Background The recurrence of cardiac events in patients with idiopathic ventricular fibrillation (VF)  excluding  patients with the Brugada syndrome is unclear since this entity remains present in previous studies.
Background
The recurrence of cardiac events in patients with idiopathic ventricular fibrillation (VF)  excluding  patients with the Brugada syndrome is unclear since this entity remains present in previous studies.excludingMethods Since 1992, 18 patients (72% male) with idiopathic VF out of 455 ICD implants were treated with an implantable cardioverter defibrillator (ICD). The mean age at first ICD implantation was 42 ± 14 years. Brugada syndrome, as well as other primary electrical diseases (e.g. long QT), were systematically excluded in all patients by the absence of the typical electrocardiogram (ST elevation in the right precordial leads) at rest and/or after pharmacological tests (ajmaline, flecainide, or procainamide). Recurrence of cardiac events was prospectively assessed.
Methods
Since 1992, 18 patients (72% male) with idiopathic VF out of 455 ICD implants were treated with an implantable cardioverter defibrillator (ICD). The mean age at first ICD implantation was 42 ± 14 years. Brugada syndrome, as well as other primary electrical diseases (e.g. long QT), were systematically excluded in all patients by the absence of the typical electrocardiogram (ST elevation in the right precordial leads) at rest and/or after pharmacological tests (ajmaline, flecainide, or procainamide). Recurrence of cardiac events was prospectively assessed.Results During a mean follow-up period of 41 ± 27 months, VF recurrence with appropriate shock occurred in 7 patients (39%) covering a total of 27 shocks. The median time to first appropriate shock was 12 ± 9 months. There were no deaths. In the electrophysiological study, 39% of patients were inducible, but inducibility failed to predict subsequent arrhythmic events. Forty-four percent of patients suffered 21 inappropriate shocks, which were caused by sinus tachycardia, atrial arrhythmias or lead malfunction.
Results
During a mean follow-up period of 41 ± 27 months, VF recurrence with appropriate shock occurred in 7 patients (39%) covering a total of 27 shocks. The median time to first appropriate shock was 12 ± 9 months. There were no deaths. In the electrophysiological study, 39% of patients were inducible, but inducibility failed to predict subsequent arrhythmic events. Forty-four percent of patients suffered 21 inappropriate shocks, which were caused by sinus tachycardia, atrial arrhythmias or lead malfunction.Conclusion Idiopathic ventricular fibrillation patients have a high recurrence rate of potentially fatal ventricular arrhythmias,  excluding  patients with the Brugada syndrome or other known causes. ICD prevents sudden cardiac death but inappropriate shocks remained a major issue in this young and active population.
Conclusion
Idiopathic ventricular fibrillation patients have a high recurrence rate of potentially fatal ventricular arrhythmias,  excluding  patients with the Brugada syndrome or other known causes. ICD prevents sudden cardiac death but inappropriate shocks remained a major issue in this young and active population.excluding

Background Idiopathic ventricular fibrillation (VF) is defined as spontaneous ventricular fibrillation in the absence of any structural heart disease, including coronary artery disease, valvular heart disease, myocarditis, cardiomyopathy or electrophysiological diseases, with a well-defined cause, such as the long QT syndrome, the Brugada syndrome, ventricular pre-excitation (WPW), and drug intoxication [ 1 ]. The consensus statement of the joint steering committees of the UCARE registry of Europe and of the idiopathic VF registry of US reported in 1997 that patients with the Brugada syndrome should be considered a variant of idiopathic VF [ 1 ]. Brugada syndrome is characterized by a unique electrocardiographic (ECG) pattern of right bundle branch block with ST elevation in the right precordial leads. Transient forms of the disease in which the ECG normalizes for a period of time have been described. Administration of sodium channel blockers will unmask the abnormal ECG in patients with transient normalized ECGs [ 2 , 3 ]. The American Heart Association has recently proposed diagnostic criteria for the Brugada syndrome [ 4 ]. Moreover, the incidence of Brugada syndrome among patients with idiopathic VF remains unclear. The prevalence of a Brugada type ECG pattern was reported in 21% [ 5 ] and 24% [ 6 ] of idiopathic VF populations. However, on the basis of pharmacological tests, it has been speculated that up to 40% – 60% of patients diagnosed with idiopathic VF might actually suffer from the Brugada syndrome [ 7 ]. Since this is a new clinical entity, older publications probably classified some patients with Brugada syndrome as idiopathic VF, since intravenous administration of a sodium channel blocker to unmask a concealed form of the disease was not systematically performed. Our report describes the clinical and electrophysiological characteristics of consecutive sudden cardiac arrest survivors from idiopathic VF who received an ICD, and in whom electrical and structural heart diseases including Brugada syndrome, long QT, arrhythmogenic right ventricular dysplasia, and hypertrophic cardiomyopathy characterized by a high recurrence rate, were systematically excluded.
Background
Idiopathic ventricular fibrillation (VF) is defined as spontaneous ventricular fibrillation in the absence of any structural heart disease, including coronary artery disease, valvular heart disease, myocarditis, cardiomyopathy or electrophysiological diseases, with a well-defined cause, such as the long QT syndrome, the Brugada syndrome, ventricular pre-excitation (WPW), and drug intoxication [ 1 ]. The consensus statement of the joint steering committees of the UCARE registry of Europe and of the idiopathic VF registry of US reported in 1997 that patients with the Brugada syndrome should be considered a variant of idiopathic VF [ 1 ].Brugada syndrome is characterized by a unique electrocardiographic (ECG) pattern of right bundle branch block with ST elevation in the right precordial leads. Transient forms of the disease in which the ECG normalizes for a period of time have been described. Administration of sodium channel blockers will unmask the abnormal ECG in patients with transient normalized ECGs [ 2 , 3 ]. The American Heart Association has recently proposed diagnostic criteria for the Brugada syndrome [ 4 ]. Moreover, the incidence of Brugada syndrome among patients with idiopathic VF remains unclear. The prevalence of a Brugada type ECG pattern was reported in 21% [ 5 ] and 24% [ 6 ] of idiopathic VF populations. However, on the basis of pharmacological tests, it has been speculated that up to 40% – 60% of patients diagnosed with idiopathic VF might actually suffer from the Brugada syndrome [ 7 ]. Since this is a new clinical entity, older publications probably classified some patients with Brugada syndrome as idiopathic VF, since intravenous administration of a sodium channel blocker to unmask a concealed form of the disease was not systematically performed. Our report describes the clinical and electrophysiological characteristics of consecutive sudden cardiac arrest survivors from idiopathic VF who received an ICD, and in whom electrical and structural heart diseases including Brugada syndrome, long QT, arrhythmogenic right ventricular dysplasia, and hypertrophic cardiomyopathy characterized by a high recurrence rate, were systematically excluded.Methods Patient population The total population under investigation included 455 consecutive patients who received a third generation ICD, with stored electrograms capabilities for hemodynamically poorly tolerated ventricular tachyarrhythmias, from 1992 to 2000. Of these, 29 were initially diagnosed as idiopathic VF associated with a structurally normal heart, normal left and right ventricular ejection fraction and normal coronary arteries. During the follow-up, 11 patients developed a new diagnosis potentially explaining VF, and were excluded from the final analysis. Four had right ventricular dysplasia, 5 had Brugada syndrome with the typical ECG manifestations after a drug challenge, and 2 patients had long QT syndrome. A final diagnosis of idiopathic VF was made in the remaining 18 patients. All patients had survived either an episode of cardiac arrest due to VF (12 patients) or a syncopal episode associated with documented self-terminating polymorphic ventricular tachycardia or fibrillation (6 patients). In 15 patients, the documented VF was seen during daily activity (one episode during sustained effort) and in 3 patients, during night-time. Out of the 18 patients, 10 had a previous history of unexplained syncope. Definitions and investigation Idiopathic VF was defined as VF in the absence of demonstrable cardiac abnormalities as previously reported [ 1 ]. Thus, we excluded other known causes of VT/VF such as WPW syndrome, congenital long QT syndrome, short-coupled  torsade de pointes , catecholamine-induced polymorphic VT, and Brugada syndrome. No patient had a past history of ischemic heart disease, congestive heart failure or family history of unexpected sudden cardiac death. All patients had a normal physical examination, blood testing and exercise test. Structural heart disease was excluded in all by echocardiography, cardiac catheterization including right and left ventricular angiography and coronary angiography. Patients on anti-arhythmic therapy before their cardiac arrest were excluded from the study, as well as those with electrolyte disturbances, history of significant alcohol or drug abuse or prolonged QT c . Of the 18 patients, 10 patients had normal right ventricular endomyocardial biopsy and 8 patients had a normal cardiac magnetic resonance imaging. Moreover, in 5 patients, an ergonovine provocation test was performed to exclude coronary artery spasm. Brugada syndrome was systematically excluded in all patients by negative serial ECG recordings with the typical coved or saddle shaped-type ST-segment elevation in the right precordial leads. All patients received  iv  administration of a sodium channel blocker to unmask a concealed form of the disease and all tests were negative. Flecainide (2 mg/kg body weight) was used in 9 patients, procainamide (10 mg/kg body weight) in 4 patients, and ajmaline (0.7 mg/kg body weight) in 7 patients. Electrophysiological study Programmed electrical stimulation was performed in all patients using up to 3 extra-stimuli at 3 different drive cycle lengths (600, 500, and 430 ms) delivered to the right ventricular apex. The coupling interval of the first 2 extra-stimuli was not shorter than 180 ms and not shorter than 200 ms for the third extra-stimuli. In case of non-inducibility, programmed stimulation was also performed from the right ventricular outflow tract. Sustained VF was defined as VF at a cycle length ≤ 200 ms and lasting ≥ 30 seconds or requiring immediate defibrillation. Sustained ventricular tachycardia (VT) was defined as VT lasting ≥ 30 seconds or requiring termination secondary to hemodynamic instability. Non-sustained VT was defined as >6 consecutive ventricular complexes or VT lasting <30 seconds. ICD implantation All patients received a transvenous ICD with stored electrograms. Recorded episodes were reviewed and adjudicated as appropriate or inappropriate therapies. VF was defined at follow-up as consecutive ventricular beats recorded from the device at a cycle length of 240 msec or less. In all patients, the ICD was programmed with only 1 ventricular fibrillation detection zone at 180 bpm (333 msec). Only shock therapy was programmed. All patients were seen at follow-up in our centre. Statistical analysis All data are expressed as mean ± standard deviation. Kaplan-Meier analysis was used to analyze time intervals until the first appropriate shock.
Methods
Patient population The total population under investigation included 455 consecutive patients who received a third generation ICD, with stored electrograms capabilities for hemodynamically poorly tolerated ventricular tachyarrhythmias, from 1992 to 2000. Of these, 29 were initially diagnosed as idiopathic VF associated with a structurally normal heart, normal left and right ventricular ejection fraction and normal coronary arteries. During the follow-up, 11 patients developed a new diagnosis potentially explaining VF, and were excluded from the final analysis. Four had right ventricular dysplasia, 5 had Brugada syndrome with the typical ECG manifestations after a drug challenge, and 2 patients had long QT syndrome. A final diagnosis of idiopathic VF was made in the remaining 18 patients. All patients had survived either an episode of cardiac arrest due to VF (12 patients) or a syncopal episode associated with documented self-terminating polymorphic ventricular tachycardia or fibrillation (6 patients). In 15 patients, the documented VF was seen during daily activity (one episode during sustained effort) and in 3 patients, during night-time. Out of the 18 patients, 10 had a previous history of unexplained syncope.
Patient population
The total population under investigation included 455 consecutive patients who received a third generation ICD, with stored electrograms capabilities for hemodynamically poorly tolerated ventricular tachyarrhythmias, from 1992 to 2000. Of these, 29 were initially diagnosed as idiopathic VF associated with a structurally normal heart, normal left and right ventricular ejection fraction and normal coronary arteries. During the follow-up, 11 patients developed a new diagnosis potentially explaining VF, and were excluded from the final analysis. Four had right ventricular dysplasia, 5 had Brugada syndrome with the typical ECG manifestations after a drug challenge, and 2 patients had long QT syndrome. A final diagnosis of idiopathic VF was made in the remaining 18 patients. All patients had survived either an episode of cardiac arrest due to VF (12 patients) or a syncopal episode associated with documented self-terminating polymorphic ventricular tachycardia or fibrillation (6 patients). In 15 patients, the documented VF was seen during daily activity (one episode during sustained effort) and in 3 patients, during night-time. Out of the 18 patients, 10 had a previous history of unexplained syncope.Definitions and investigation Idiopathic VF was defined as VF in the absence of demonstrable cardiac abnormalities as previously reported [ 1 ]. Thus, we excluded other known causes of VT/VF such as WPW syndrome, congenital long QT syndrome, short-coupled  torsade de pointes , catecholamine-induced polymorphic VT, and Brugada syndrome. No patient had a past history of ischemic heart disease, congestive heart failure or family history of unexpected sudden cardiac death. All patients had a normal physical examination, blood testing and exercise test. Structural heart disease was excluded in all by echocardiography, cardiac catheterization including right and left ventricular angiography and coronary angiography. Patients on anti-arhythmic therapy before their cardiac arrest were excluded from the study, as well as those with electrolyte disturbances, history of significant alcohol or drug abuse or prolonged QT c . Of the 18 patients, 10 patients had normal right ventricular endomyocardial biopsy and 8 patients had a normal cardiac magnetic resonance imaging. Moreover, in 5 patients, an ergonovine provocation test was performed to exclude coronary artery spasm. Brugada syndrome was systematically excluded in all patients by negative serial ECG recordings with the typical coved or saddle shaped-type ST-segment elevation in the right precordial leads. All patients received  iv  administration of a sodium channel blocker to unmask a concealed form of the disease and all tests were negative. Flecainide (2 mg/kg body weight) was used in 9 patients, procainamide (10 mg/kg body weight) in 4 patients, and ajmaline (0.7 mg/kg body weight) in 7 patients.
Definitions and investigation
Idiopathic VF was defined as VF in the absence of demonstrable cardiac abnormalities as previously reported [ 1 ]. Thus, we excluded other known causes of VT/VF such as WPW syndrome, congenital long QT syndrome, short-coupled  torsade de pointes , catecholamine-induced polymorphic VT, and Brugada syndrome. No patient had a past history of ischemic heart disease, congestive heart failure or family history of unexpected sudden cardiac death. All patients had a normal physical examination, blood testing and exercise test. Structural heart disease was excluded in all by echocardiography, cardiac catheterization including right and left ventricular angiography and coronary angiography. Patients on anti-arhythmic therapy before their cardiac arrest were excluded from the study, as well as those with electrolyte disturbances, history of significant alcohol or drug abuse or prolonged QT c . Of the 18 patients, 10 patients had normal right ventricular endomyocardial biopsy and 8 patients had a normal cardiac magnetic resonance imaging. Moreover, in 5 patients, an ergonovine provocation test was performed to exclude coronary artery spasm. Brugada syndrome was systematically excluded in all patients by negative serial ECG recordings with the typical coved or saddle shaped-type ST-segment elevation in the right precordial leads. All patients received  iv  administration of a sodium channel blocker to unmask a concealed form of the disease and all tests were negative. Flecainide (2 mg/kg body weight) was used in 9 patients, procainamide (10 mg/kg body weight) in 4 patients, and ajmaline (0.7 mg/kg body weight) in 7 patients.torsade de pointesivElectrophysiological study Programmed electrical stimulation was performed in all patients using up to 3 extra-stimuli at 3 different drive cycle lengths (600, 500, and 430 ms) delivered to the right ventricular apex. The coupling interval of the first 2 extra-stimuli was not shorter than 180 ms and not shorter than 200 ms for the third extra-stimuli. In case of non-inducibility, programmed stimulation was also performed from the right ventricular outflow tract. Sustained VF was defined as VF at a cycle length ≤ 200 ms and lasting ≥ 30 seconds or requiring immediate defibrillation. Sustained ventricular tachycardia (VT) was defined as VT lasting ≥ 30 seconds or requiring termination secondary to hemodynamic instability. Non-sustained VT was defined as >6 consecutive ventricular complexes or VT lasting <30 seconds.
Electrophysiological study
Programmed electrical stimulation was performed in all patients using up to 3 extra-stimuli at 3 different drive cycle lengths (600, 500, and 430 ms) delivered to the right ventricular apex. The coupling interval of the first 2 extra-stimuli was not shorter than 180 ms and not shorter than 200 ms for the third extra-stimuli. In case of non-inducibility, programmed stimulation was also performed from the right ventricular outflow tract. Sustained VF was defined as VF at a cycle length ≤ 200 ms and lasting ≥ 30 seconds or requiring immediate defibrillation. Sustained ventricular tachycardia (VT) was defined as VT lasting ≥ 30 seconds or requiring termination secondary to hemodynamic instability. Non-sustained VT was defined as >6 consecutive ventricular complexes or VT lasting <30 seconds.ICD implantation All patients received a transvenous ICD with stored electrograms. Recorded episodes were reviewed and adjudicated as appropriate or inappropriate therapies. VF was defined at follow-up as consecutive ventricular beats recorded from the device at a cycle length of 240 msec or less. In all patients, the ICD was programmed with only 1 ventricular fibrillation detection zone at 180 bpm (333 msec). Only shock therapy was programmed. All patients were seen at follow-up in our centre.
ICD implantation
All patients received a transvenous ICD with stored electrograms. Recorded episodes were reviewed and adjudicated as appropriate or inappropriate therapies. VF was defined at follow-up as consecutive ventricular beats recorded from the device at a cycle length of 240 msec or less. In all patients, the ICD was programmed with only 1 ventricular fibrillation detection zone at 180 bpm (333 msec). Only shock therapy was programmed. All patients were seen at follow-up in our centre.Statistical analysis All data are expressed as mean ± standard deviation. Kaplan-Meier analysis was used to analyze time intervals until the first appropriate shock.
Statistical analysis
All data are expressed as mean ± standard deviation. Kaplan-Meier analysis was used to analyze time intervals until the first appropriate shock.Results The study cohort consisted of 13 men and 5 women (Table  1 ), with a mean age at the first ICD implantation of 42 ± 14 years (range 20 to 70 years). Baseline electrocardiograms were normal in 16 patients. One patient had a left bundle branch block and 1 had a right bundle branch block. The mean QT c  for the entire population was 410 ± 20 msec. All patients had a normal left ventricular ejection fraction (≥ 50%) without regional wall motion abnormalities. Mean left ventricular ejection fraction (EF) was 69 ± 8% (range 52 to 81%). No patient had significant coronary artery disease (defined as ≥ 50% stenosis). Microscopic examination of right ventricular biopsy specimens in 10 patients showed no evidence of a viral, infiltrative or dysplasic process in the myocardium. Baseline electrophysiological studies were performed in all patients and showed normal sinus node, atrioventricular node and His-Purkinje function in all. Inducible sustained ventricular arrhythmias occurred in 7 patients (39%). From these, 4 patients had sustained VF and 3 patients had sustained inducible monomorphic VT or ventricular flutter (cycle length 230 ± 20 ms). Two extra-stimuli were required in 5 patients and 3 extra-stimuli in 2 patients. Non-sustained VT-VF was induced in 3 patients. No arrhythmia could be induced in 8 patients. Table 1 Clinical characteristics and outcome of 18 patients with idiopathic VF Baseline Characteristics ICD Therapy Patient Age (years) sex CE Drug test to exclude Brugada PES AS NSVT IS Ind S Time to 1 st  AS (months) Follow-up (months) AAD during follow-up 1 47,M Sy-VF F SMVT 6 7 - - 4 17 sotalol 2 51,F CA F NI 7 21 - - 1 19 sotalol 3 66,M CA AJ VF - - - - - 5 - 4 70,F CA P NI - - 6(af) - - 19 amiodarone 5 46,M CA F NI - 1 1(af) - - 23 sotalol 6 20,M Sy-VF A VF - - 3(st-lp) - - 92 b-blocker 7 46,F CA P VF - 120 - - - 27 sotalol 8 40,M CA A NSVT 1 - - - 13 75 - 9 33,M Sy-VF F NSVT - 1 - - - 19 - 10 26,M CA F NI 1 - 3(st-lp) - 7 9 sotalol 11 33,F CA F NI - - - - - 18 - 12 50,F CA F SMVT 6 - 1(st) - 13 86 flecainide 13 25,M CA AJ + P NSVT - 1 - - - 62 - 14 36,M CA AJ NI 2 - 2(af) 4 27 55 sotalol 15 58,M Sy-VF AJ NI - - 3(af) 2 - 57 sotalol 16 44,M CA F + P NI - - - - - 48 - 17 28,M Sy-VF F VF 4 - 2(st) - 18 55 sotalol 18 35,M Sy-VF A SMVT - - - - - 59 - CE: clinical events; CA: cardiac arrest; Sy-VF: syncope with documented self-terminating polymorphic VT or VF PES: programmed electrical stimulation; M: male; F: female SM: sustained monomorphic; VT: ventricular tachycardia; VF: ventricular fibrillation NS: non sustained; NI: non inducibility; af: atrial fibrillation; st: sinus tachycardia; lp: lead problem AS: appropriate shock; IS: inappropriate shock; Ind S: indeterminate cause for shocks; AAD: antiarrhythmic drug; F: flécaïnide; AJ: ajmaline; P: procainamide Long-term outcome After a mean follow-up of 41 ± 27 months (ranging from 5 to 92 months), 7 of the 18 patients (39%) with idiopathic VF had VF or sustained polymorphic VT recurrence and received appropriate shocks (Table  1 ). These patients experienced a total of 27 shocks; 5 of them had more than 1 episode (2 to 7). Mean time to first appropriate shock was 12 ± 9 months (ranging from 0.4 to 27 months). No arrhythmic storm was observed at follow-up (defined as ≥ 3 separate VT/VF episodes within 24 h). With the use of stored electrograms, 6 patients had documented non-sustained polymorphic VT or VF for a total of 149 episodes (range 1 to 120). Four of them have not received any appropriate shock. These episodes were detected by the ICD but shock delivery was appropriately aborted by the non-committed function of the device. There was no relationship between the initial clinical and arrhythmic presentation and subsequent arrhythmic events recorded from the ICD at follow-up (Table  1 ). From the intracardiac electrograms, the arrhythmia initiation was always associated with PVCs with a mean coupling interval of 300 ± 35 ms. A long-short initiating sequence of VF was never observed. In 5 patients, multiple VF episodes were recorded by the ICD, all of which for a single patient were associated with the same PVC coupling interval. Since the stored electrograms in the present study were obtained from endocardial sites and were single-channel recordings, we could not assess the origin of the PVCs. The mean QTc at the time of VF recurrence was normal in all patients (mean 418 ± 22 msec). The ICD effectively recognized and promptly treated all the polymorphic VT or VF recurrences and prevented the possible occurrence of sudden cardiac death. No death was reported during follow-up. Non-invasive follow-up examinations failed to detect any new structural heart disease or primary electrical disease such as long QT or Brugada syndrome. Value of electrophysiological Testing Programmed electrical stimulation failed to predict subsequent cardiac events. The sensitivity and specificity were 43 and 64%, respectively. The positive and negative predictive values were also 43 and 64%, respectively, that is not considered clinically useful. Causes and incidence of inappropriate shocks In this population, we observed a high incidence of inappropriate shocks. Eight of the 18 patients (44%) received an inappropriate shock for a total of 21 discharges. Atrial fibrillation was responsible for 57% of them (12 episodes in 4 patients). These were older patients with a mean age of 53 ± 14 years. Six inappropriate shocks (4 patients) were triggered by sinus tachycardia. These patients were younger with a mean age of 31 ± 13 years. Lead malfunction caused 3 inappropriate shocks in 2 patients. Six shocks in 2 patients were classified as of unknown cause, even after careful examination of the intracardiac electrograms. These shocks were probably inappropriate since no clinical symptoms occurred during these episodes and these 2 patients already experienced inappropriate shocks for atrial fibrillation. Device follow-up During the follow-up period, first-time generator replacement was performed in 9 patients after a mean of 43 ± 11 months after initial implantation (range 21 to 58). End of life battery was the indication for replacement in 8 patients, and 1 had an ICD component failure. A second replacement was done in 2 patients. Lead replacement was also indicated in 2 patients for lead insulation fracture. Adjunctive anti-arrhythmic drugs were required in 11 patients after ICD implantation in order to control for the occurrence of appropriate or inappropriate shocks (Table  1 ).
Results
The study cohort consisted of 13 men and 5 women (Table  1 ), with a mean age at the first ICD implantation of 42 ± 14 years (range 20 to 70 years). Baseline electrocardiograms were normal in 16 patients. One patient had a left bundle branch block and 1 had a right bundle branch block. The mean QT c  for the entire population was 410 ± 20 msec. All patients had a normal left ventricular ejection fraction (≥ 50%) without regional wall motion abnormalities. Mean left ventricular ejection fraction (EF) was 69 ± 8% (range 52 to 81%). No patient had significant coronary artery disease (defined as ≥ 50% stenosis). Microscopic examination of right ventricular biopsy specimens in 10 patients showed no evidence of a viral, infiltrative or dysplasic process in the myocardium. Baseline electrophysiological studies were performed in all patients and showed normal sinus node, atrioventricular node and His-Purkinje function in all. Inducible sustained ventricular arrhythmias occurred in 7 patients (39%). From these, 4 patients had sustained VF and 3 patients had sustained inducible monomorphic VT or ventricular flutter (cycle length 230 ± 20 ms). Two extra-stimuli were required in 5 patients and 3 extra-stimuli in 2 patients. Non-sustained VT-VF was induced in 3 patients. No arrhythmia could be induced in 8 patients.Clinical characteristics and outcome of 18 patients with idiopathic VFBaseline CharacteristicsICD TherapyPatientAge (years) sexCEDrug test to exclude BrugadaPESASNSVTISInd STime to 1 st  AS (months)Follow-up (months)AAD during follow-upCE: clinical events; CA: cardiac arrest; Sy-VF: syncope with documented self-terminating polymorphic VT or VFPES: programmed electrical stimulation; M: male; F: femaleSM: sustained monomorphic; VT: ventricular tachycardia; VF: ventricular fibrillationNS: non sustained; NI: non inducibility; af: atrial fibrillation; st: sinus tachycardia; lp: lead problemAS: appropriate shock; IS: inappropriate shock; Ind S: indeterminate cause for shocks;AAD: antiarrhythmic drug; F: flécaïnide; AJ: ajmaline; P: procainamideLong-term outcome After a mean follow-up of 41 ± 27 months (ranging from 5 to 92 months), 7 of the 18 patients (39%) with idiopathic VF had VF or sustained polymorphic VT recurrence and received appropriate shocks (Table  1 ). These patients experienced a total of 27 shocks; 5 of them had more than 1 episode (2 to 7). Mean time to first appropriate shock was 12 ± 9 months (ranging from 0.4 to 27 months). No arrhythmic storm was observed at follow-up (defined as ≥ 3 separate VT/VF episodes within 24 h). With the use of stored electrograms, 6 patients had documented non-sustained polymorphic VT or VF for a total of 149 episodes (range 1 to 120). Four of them have not received any appropriate shock. These episodes were detected by the ICD but shock delivery was appropriately aborted by the non-committed function of the device. There was no relationship between the initial clinical and arrhythmic presentation and subsequent arrhythmic events recorded from the ICD at follow-up (Table  1 ). From the intracardiac electrograms, the arrhythmia initiation was always associated with PVCs with a mean coupling interval of 300 ± 35 ms. A long-short initiating sequence of VF was never observed. In 5 patients, multiple VF episodes were recorded by the ICD, all of which for a single patient were associated with the same PVC coupling interval. Since the stored electrograms in the present study were obtained from endocardial sites and were single-channel recordings, we could not assess the origin of the PVCs. The mean QTc at the time of VF recurrence was normal in all patients (mean 418 ± 22 msec). The ICD effectively recognized and promptly treated all the polymorphic VT or VF recurrences and prevented the possible occurrence of sudden cardiac death. No death was reported during follow-up. Non-invasive follow-up examinations failed to detect any new structural heart disease or primary electrical disease such as long QT or Brugada syndrome.
Long-term outcome
After a mean follow-up of 41 ± 27 months (ranging from 5 to 92 months), 7 of the 18 patients (39%) with idiopathic VF had VF or sustained polymorphic VT recurrence and received appropriate shocks (Table  1 ). These patients experienced a total of 27 shocks; 5 of them had more than 1 episode (2 to 7). Mean time to first appropriate shock was 12 ± 9 months (ranging from 0.4 to 27 months). No arrhythmic storm was observed at follow-up (defined as ≥ 3 separate VT/VF episodes within 24 h). With the use of stored electrograms, 6 patients had documented non-sustained polymorphic VT or VF for a total of 149 episodes (range 1 to 120). Four of them have not received any appropriate shock. These episodes were detected by the ICD but shock delivery was appropriately aborted by the non-committed function of the device. There was no relationship between the initial clinical and arrhythmic presentation and subsequent arrhythmic events recorded from the ICD at follow-up (Table  1 ). From the intracardiac electrograms, the arrhythmia initiation was always associated with PVCs with a mean coupling interval of 300 ± 35 ms. A long-short initiating sequence of VF was never observed. In 5 patients, multiple VF episodes were recorded by the ICD, all of which for a single patient were associated with the same PVC coupling interval. Since the stored electrograms in the present study were obtained from endocardial sites and were single-channel recordings, we could not assess the origin of the PVCs. The mean QTc at the time of VF recurrence was normal in all patients (mean 418 ± 22 msec). The ICD effectively recognized and promptly treated all the polymorphic VT or VF recurrences and prevented the possible occurrence of sudden cardiac death. No death was reported during follow-up. Non-invasive follow-up examinations failed to detect any new structural heart disease or primary electrical disease such as long QT or Brugada syndrome.Value of electrophysiological Testing Programmed electrical stimulation failed to predict subsequent cardiac events. The sensitivity and specificity were 43 and 64%, respectively. The positive and negative predictive values were also 43 and 64%, respectively, that is not considered clinically useful.
Value of electrophysiological Testing
Programmed electrical stimulation failed to predict subsequent cardiac events. The sensitivity and specificity were 43 and 64%, respectively. The positive and negative predictive values were also 43 and 64%, respectively, that is not considered clinically useful.Causes and incidence of inappropriate shocks In this population, we observed a high incidence of inappropriate shocks. Eight of the 18 patients (44%) received an inappropriate shock for a total of 21 discharges. Atrial fibrillation was responsible for 57% of them (12 episodes in 4 patients). These were older patients with a mean age of 53 ± 14 years. Six inappropriate shocks (4 patients) were triggered by sinus tachycardia. These patients were younger with a mean age of 31 ± 13 years. Lead malfunction caused 3 inappropriate shocks in 2 patients. Six shocks in 2 patients were classified as of unknown cause, even after careful examination of the intracardiac electrograms. These shocks were probably inappropriate since no clinical symptoms occurred during these episodes and these 2 patients already experienced inappropriate shocks for atrial fibrillation.
Causes and incidence of inappropriate shocks
In this population, we observed a high incidence of inappropriate shocks. Eight of the 18 patients (44%) received an inappropriate shock for a total of 21 discharges. Atrial fibrillation was responsible for 57% of them (12 episodes in 4 patients). These were older patients with a mean age of 53 ± 14 years. Six inappropriate shocks (4 patients) were triggered by sinus tachycardia. These patients were younger with a mean age of 31 ± 13 years. Lead malfunction caused 3 inappropriate shocks in 2 patients. Six shocks in 2 patients were classified as of unknown cause, even after careful examination of the intracardiac electrograms. These shocks were probably inappropriate since no clinical symptoms occurred during these episodes and these 2 patients already experienced inappropriate shocks for atrial fibrillation.Device follow-up During the follow-up period, first-time generator replacement was performed in 9 patients after a mean of 43 ± 11 months after initial implantation (range 21 to 58). End of life battery was the indication for replacement in 8 patients, and 1 had an ICD component failure. A second replacement was done in 2 patients. Lead replacement was also indicated in 2 patients for lead insulation fracture. Adjunctive anti-arrhythmic drugs were required in 11 patients after ICD implantation in order to control for the occurrence of appropriate or inappropriate shocks (Table  1 ).
Device follow-up
During the follow-up period, first-time generator replacement was performed in 9 patients after a mean of 43 ± 11 months after initial implantation (range 21 to 58). End of life battery was the indication for replacement in 8 patients, and 1 had an ICD component failure. A second replacement was done in 2 patients. Lead replacement was also indicated in 2 patients for lead insulation fracture. Adjunctive anti-arrhythmic drugs were required in 11 patients after ICD implantation in order to control for the occurrence of appropriate or inappropriate shocks (Table  1 ).Discussion To our knowledge, this report is the first study to describe the clinical outcome of ICD patients with a diagnosis of idiopathic VF in whom the Brugada syndrome, characterized by a high recurrence rate, was systematically excluded. Since there is a wide variability in the ECG expression in individual patients with the Brugada syndrome, we performed  iv  administration of sodium channel blockers to unmask the ECG features of the syndrome in all our idiopathic VF patients. Two studies reported the long-term outcome of patients with idiopathic VF without the Brugada syndrome [ 5 , 6 ]. Viskin et al. [ 5 ] performed  iv  administration of a sodium channel blocker to unmask a concealed form of Brugada syndrome in only 15 % of their idiopathic VF population, whereas Remme et al. [ 6 ] tested the effect of an  iv  sodium channel blocker on ECG morphology in only 30% of the patients. The unique finding of the present report is the high recurrence rate of sustained ventricular arrhythmias in this well-characterized idiopathic VF group, even after a careful systematic evaluation to exclude the presence of Brugada syndrome. After a mean follow-up of 41 ± 27 months, 39% of the patients received an appropriate ICD discharge for VF or polymorphic VT. In accordance with references [ 8 , 9 ], ICD therapy offered good protection against fatal outcome due to recurrent ventricular arrhythmias, with no mortality during the follow-up. The high recurrence rate is consistent with the relatively high recurrence rate of arrhythmic events or sudden death from the UCARE registry [ 10 ], as well as the high frequency of electrical discharges from ICDs reported in a large series of patients with idiopathic VF [ 6 , 8 , 9 ]. In comparison, appropriate ICD discharges have been reported in 48% of arrhythmogenic right ventricular dysplasia population [ 11 ], 40 to 56% of inducible population receiving an ICD [ 12 , 13 ] and 23% (7%/year) in the hypertrophic cardiomyopathy population [ 14 ]. However, some authors have reported a more benign clinical course of their idiopathic VF population with a lower recurrence rate [ 15 - 17 ]. Our high ICD discharge rate might also be explained by the rapid ICD intervention for fast ventricular arrhythmia that could have been self-terminated. The definition of idiopathic VF remains problematic, since numerous studies including idiopathic VF population are heterogeneous. Indeed, 61% (11/18 patients) of our cohort remained free of sustained arrhythmia recurrence during follow-up despite the same initial VF or syncopal presentation. Of note, idiopathic VF is always a diagnosis of exclusion. The patients in our cohort, as well as in other reported series, had normal hearts, as defined by clinical, non-invasive and invasive testing. Even after a careful investigation, a transient phenomenon such as a reversible localized myocardial disease, silent myocardial ischemia due to coronary artery spasm or sudden manifestation of an unknown primary electrophysiological disease could easily be missed by the clinician, and be responsible for the VF episode. Idiopathic VF is in fact an amalgam of different diseases in which the first clinical manifestation is VF. The ultimate answer probably lies in a more comprehensive approach and a more precise understanding of the molecular genetics and associated electrophysiological abnormalities in finding a specific treatment avoiding ICD implantation with its associated complications. Anti-arrhythmic drugs have also been used in this clinical condition. Belhassen et al. [ 18 ] reported excellent results in their idiopathic VF population with EP-guided therapy using Class 1A drugs, primarily quinidine; no death occurred during a mean follow-up of >9 years. Recent evidence also suggests that frequent premature ventricular contractions arising from the Purkinje system are responsible for initiation of ventricular fibrillation, and can be mapped and ablated in selected patients [ 19 ]. Until another proven therapy has been assessed prospectively, the possibility of VF recurrence mandates ICD implantation as currently proposed in ICD guidelines [ 20 ]. Electrophysiological findings The inducibility rate (39%) of sustained VT/VF observed in our study is also in accordance with the results of the UCARE registry [ 10 ]. Of importance, programmed electrical stimulation was of limited value with a poor sensitivity and specificity. Moreover, inducibility failed to predict subsequent arrhythmic events. Our findings differ from the observed 79% average inducibility rate reported by Belhassen et al. [ 17 , 18 ]. This may be due to different patient characteristics and stimulation protocol. Our study excluded patients with Brugada syndrome known to have a high inducibility rate [ 21 ]. Compared to our stimulation protocol, Belhassen et al. [ 22 ] used up to 3 extra-stimuli, 2 basic cycle lengths, 2 RV sites (first RVA, then RVOT), and repetition of extra-stimulation ( n  = 10 for double, and  n  = 5 for triple) at the shortest coupling intervals that resulted in ventricular capture. Three patients had a fast monomorphic VT inducible even if the clinical presentation was aborted sudden cardiac death. This may suggest an underlying structural heart disease undetected by the current investigation. Although general cardiac function can be normal, patients might have discrete abnormalities, which are currently unidentifiable. Better risk stratification is required to identify patients who will experience recurrent VF over time. Therefore, defibrillator implantation could be seen as the primary therapy in patients with idiopathic VF, since no stratification has yet identified patients at risk of arrhythmia recurrence. ICD limitations The impact of multiple battery replacements over time in this young population with idiopathic VF needs to be emphasized. It is noteworthy that half the population (9/18 patients) had an ICD replacement and 2 other patients had their transvenous lead replaced during follow-up. We also observed a high incidence of inappropriate shocks (44%), mainly caused by atrial fibrillation and sinus tachycardia. This is well in accordance with other studies where up to 40% inappropriate discharge rates were observed even with fourth generation ICDs [ 23 ]. The addition of an anti-arrhythmic drug to decrease the incidence of inappropriate shocks was required in this group. Four patients experienced atrial fibrillation, which might indicate the presence of an associated primary electrophysiological disease also affecting the atrium. In patients with idiopathic VF, the characteristics, is the recurrence of VF and not monomorphic VT compared to other ventricular arrhythmias. To decrease the number of inappropriate shocks, one should program a higher VF zone around 200–220 bpm and a lower monitoring zone to detect atrial arrhythmia. Third-generation ICD still have limitations and complications over time, with a significant proportion of patients having hardware-related complications or inappropriate shocks [ 24 ]. Future developments in ICD technology is needed, which will hopefully address these issues.
Discussion
To our knowledge, this report is the first study to describe the clinical outcome of ICD patients with a diagnosis of idiopathic VF in whom the Brugada syndrome, characterized by a high recurrence rate, was systematically excluded. Since there is a wide variability in the ECG expression in individual patients with the Brugada syndrome, we performed  iv  administration of sodium channel blockers to unmask the ECG features of the syndrome in all our idiopathic VF patients. Two studies reported the long-term outcome of patients with idiopathic VF without the Brugada syndrome [ 5 , 6 ]. Viskin et al. [ 5 ] performed  iv  administration of a sodium channel blocker to unmask a concealed form of Brugada syndrome in only 15 % of their idiopathic VF population, whereas Remme et al. [ 6 ] tested the effect of an  iv  sodium channel blocker on ECG morphology in only 30% of the patients. The unique finding of the present report is the high recurrence rate of sustained ventricular arrhythmias in this well-characterized idiopathic VF group, even after a careful systematic evaluation to exclude the presence of Brugada syndrome. After a mean follow-up of 41 ± 27 months, 39% of the patients received an appropriate ICD discharge for VF or polymorphic VT. In accordance with references [ 8 , 9 ], ICD therapy offered good protection against fatal outcome due to recurrent ventricular arrhythmias, with no mortality during the follow-up. The high recurrence rate is consistent with the relatively high recurrence rate of arrhythmic events or sudden death from the UCARE registry [ 10 ], as well as the high frequency of electrical discharges from ICDs reported in a large series of patients with idiopathic VF [ 6 , 8 , 9 ]. In comparison, appropriate ICD discharges have been reported in 48% of arrhythmogenic right ventricular dysplasia population [ 11 ], 40 to 56% of inducible population receiving an ICD [ 12 , 13 ] and 23% (7%/year) in the hypertrophic cardiomyopathy population [ 14 ]. However, some authors have reported a more benign clinical course of their idiopathic VF population with a lower recurrence rate [ 15 - 17 ]. Our high ICD discharge rate might also be explained by the rapid ICD intervention for fast ventricular arrhythmia that could have been self-terminated. The definition of idiopathic VF remains problematic, since numerous studies including idiopathic VF population are heterogeneous. Indeed, 61% (11/18 patients) of our cohort remained free of sustained arrhythmia recurrence during follow-up despite the same initial VF or syncopal presentation. Of note, idiopathic VF is always a diagnosis of exclusion. The patients in our cohort, as well as in other reported series, had normal hearts, as defined by clinical, non-invasive and invasive testing. Even after a careful investigation, a transient phenomenon such as a reversible localized myocardial disease, silent myocardial ischemia due to coronary artery spasm or sudden manifestation of an unknown primary electrophysiological disease could easily be missed by the clinician, and be responsible for the VF episode. Idiopathic VF is in fact an amalgam of different diseases in which the first clinical manifestation is VF. The ultimate answer probably lies in a more comprehensive approach and a more precise understanding of the molecular genetics and associated electrophysiological abnormalities in finding a specific treatment avoiding ICD implantation with its associated complications.ivivivAnti-arrhythmic drugs have also been used in this clinical condition. Belhassen et al. [ 18 ] reported excellent results in their idiopathic VF population with EP-guided therapy using Class 1A drugs, primarily quinidine; no death occurred during a mean follow-up of >9 years. Recent evidence also suggests that frequent premature ventricular contractions arising from the Purkinje system are responsible for initiation of ventricular fibrillation, and can be mapped and ablated in selected patients [ 19 ]. Until another proven therapy has been assessed prospectively, the possibility of VF recurrence mandates ICD implantation as currently proposed in ICD guidelines [ 20 ].Electrophysiological findings The inducibility rate (39%) of sustained VT/VF observed in our study is also in accordance with the results of the UCARE registry [ 10 ]. Of importance, programmed electrical stimulation was of limited value with a poor sensitivity and specificity. Moreover, inducibility failed to predict subsequent arrhythmic events. Our findings differ from the observed 79% average inducibility rate reported by Belhassen et al. [ 17 , 18 ]. This may be due to different patient characteristics and stimulation protocol. Our study excluded patients with Brugada syndrome known to have a high inducibility rate [ 21 ]. Compared to our stimulation protocol, Belhassen et al. [ 22 ] used up to 3 extra-stimuli, 2 basic cycle lengths, 2 RV sites (first RVA, then RVOT), and repetition of extra-stimulation ( n  = 10 for double, and  n  = 5 for triple) at the shortest coupling intervals that resulted in ventricular capture. Three patients had a fast monomorphic VT inducible even if the clinical presentation was aborted sudden cardiac death. This may suggest an underlying structural heart disease undetected by the current investigation. Although general cardiac function can be normal, patients might have discrete abnormalities, which are currently unidentifiable. Better risk stratification is required to identify patients who will experience recurrent VF over time. Therefore, defibrillator implantation could be seen as the primary therapy in patients with idiopathic VF, since no stratification has yet identified patients at risk of arrhythmia recurrence.
Electrophysiological findings
The inducibility rate (39%) of sustained VT/VF observed in our study is also in accordance with the results of the UCARE registry [ 10 ]. Of importance, programmed electrical stimulation was of limited value with a poor sensitivity and specificity. Moreover, inducibility failed to predict subsequent arrhythmic events. Our findings differ from the observed 79% average inducibility rate reported by Belhassen et al. [ 17 , 18 ]. This may be due to different patient characteristics and stimulation protocol. Our study excluded patients with Brugada syndrome known to have a high inducibility rate [ 21 ]. Compared to our stimulation protocol, Belhassen et al. [ 22 ] used up to 3 extra-stimuli, 2 basic cycle lengths, 2 RV sites (first RVA, then RVOT), and repetition of extra-stimulation ( n  = 10 for double, and  n  = 5 for triple) at the shortest coupling intervals that resulted in ventricular capture. Three patients had a fast monomorphic VT inducible even if the clinical presentation was aborted sudden cardiac death. This may suggest an underlying structural heart disease undetected by the current investigation. Although general cardiac function can be normal, patients might have discrete abnormalities, which are currently unidentifiable. Better risk stratification is required to identify patients who will experience recurrent VF over time. Therefore, defibrillator implantation could be seen as the primary therapy in patients with idiopathic VF, since no stratification has yet identified patients at risk of arrhythmia recurrence.nnICD limitations The impact of multiple battery replacements over time in this young population with idiopathic VF needs to be emphasized. It is noteworthy that half the population (9/18 patients) had an ICD replacement and 2 other patients had their transvenous lead replaced during follow-up. We also observed a high incidence of inappropriate shocks (44%), mainly caused by atrial fibrillation and sinus tachycardia. This is well in accordance with other studies where up to 40% inappropriate discharge rates were observed even with fourth generation ICDs [ 23 ]. The addition of an anti-arrhythmic drug to decrease the incidence of inappropriate shocks was required in this group. Four patients experienced atrial fibrillation, which might indicate the presence of an associated primary electrophysiological disease also affecting the atrium. In patients with idiopathic VF, the characteristics, is the recurrence of VF and not monomorphic VT compared to other ventricular arrhythmias. To decrease the number of inappropriate shocks, one should program a higher VF zone around 200–220 bpm and a lower monitoring zone to detect atrial arrhythmia. Third-generation ICD still have limitations and complications over time, with a significant proportion of patients having hardware-related complications or inappropriate shocks [ 24 ]. Future developments in ICD technology is needed, which will hopefully address these issues.
ICD limitations
The impact of multiple battery replacements over time in this young population with idiopathic VF needs to be emphasized. It is noteworthy that half the population (9/18 patients) had an ICD replacement and 2 other patients had their transvenous lead replaced during follow-up. We also observed a high incidence of inappropriate shocks (44%), mainly caused by atrial fibrillation and sinus tachycardia. This is well in accordance with other studies where up to 40% inappropriate discharge rates were observed even with fourth generation ICDs [ 23 ]. The addition of an anti-arrhythmic drug to decrease the incidence of inappropriate shocks was required in this group. Four patients experienced atrial fibrillation, which might indicate the presence of an associated primary electrophysiological disease also affecting the atrium. In patients with idiopathic VF, the characteristics, is the recurrence of VF and not monomorphic VT compared to other ventricular arrhythmias. To decrease the number of inappropriate shocks, one should program a higher VF zone around 200–220 bpm and a lower monitoring zone to detect atrial arrhythmia. Third-generation ICD still have limitations and complications over time, with a significant proportion of patients having hardware-related complications or inappropriate shocks [ 24 ]. Future developments in ICD technology is needed, which will hopefully address these issues.Conclusions Idiopathic VF patients have a high recurrence rate of ventricular arrhythmias, even after the systematic exclusion of patients with the Brugada syndrome or other known electrical diseases from the analysis. ICD prevents sudden cardiac death in this population, but treat only the final manifestation of an unknown disease. Inappropriate shocks remain a major concern in this young population.
Conclusions
Idiopathic VF patients have a high recurrence rate of ventricular arrhythmias, even after the systematic exclusion of patients with the Brugada syndrome or other known electrical diseases from the analysis. ICD prevents sudden cardiac death in this population, but treat only the final manifestation of an unknown disease. Inappropriate shocks remain a major concern in this young population.Competing interests The author(s) declare that they have no competing interests.
Competing interests
The author(s) declare that they have no competing interests.Author's contributions JC participated in the hypothesis generation and drafted the manuscript. PG and PB were project managers. FP participated in the final writing of the manuscript. All authors have read and approved the final version of the manuscript.
Author's contributions
JC participated in the hypothesis generation and drafted the manuscript. PG and PB were project managers. FP participated in the final writing of the manuscript. All authors have read and approved the final version of the manuscript.Pre-publication history The pre-publication history for this paper can be accessed here:
Pre-publication history
The pre-publication history for this paper can be accessed here:


Intracardiac echocardiography (ICE) is a useful tool for guiding transseptal puncture during electrophysiological mapping and ablation procedures. Left-sided accessory pathways (LSAP) can be ablated by using two different modalities: retrograde approach through the aortic valve and transseptal approach with puncture of the fossa ovalis. We shall report two cases of LSAP where transcatheter radiofrequency ablation (TCRFA) was firstly attempted via transaortic approach with ineffective results. Subsequently, a transseptal approach under ICE guidance has been performed. During atrial septal puncture ICE was able to locate the needle tip position precisely and provided a clear visualization of the "tenting effect" on the fossa ovalis. ICE allowed a better mapping of the mitral ring and a more effective catheter ablation manipulation and tip contact which resulted in a persistent and complete ablation of the accessory pathway with a shorter time of fluoroscopic exposure. ICE-guided transseptal approach might be a promising modality for TCRFA of LSAP.

Background Trans-catheter radiofrequency ablation (TCRFA) has become the treatment of choice for patients suffering from refractory to medical treatment supraventricular tachycardias [ 1 , 2 ]. During percutaneous ablation procedures, catheter location is usually monitored by using fluoroscopy together with the analysis of intracardiac electrograms in order to clarify the mechanisms underlining the arrhythmia and to both locate its origin and record its circuit. This technique may be adequate for several standard ablative procedures, but it has still some limitations concerning the treatment of more complex tachycardia forms. Left-sided accessory pathway (LSAP) may be ablated using two different modalities: conventional approach through the aortic valve, or transseptal puncture of the fossa ovalis. By using the traditional approach, the left atrium is reached by a retrograde way through the left ventricle and crossing the mitral valve [ 3 , 4 ] whereas, with the transseptal puncture, the mitral ring is reached by an anterograde approach. For this reason, this approach has been considered an alternative and complementary technique for the transvenous introduction of catheters into the left cavities of the heart [ 5 - 8 ]. However, transseptal puncture under fluoroscopic guidance alone, might be hampered by some acute and potentially lethal complications that may be challenging even for expert electrophysiologists [ 9 ]. With the technological and miniaturization advances of low frequency transducers capable of enhanced tissue penetration, intracardiac echocardiography (ICE) has become feasible and potentially useful for guiding transseptal puncture and ablation procedures, especially when location of specific anatomic landmarks appears to be more crucial [ 10 , 11 ]. In this manuscript, two cases of ICE-guided catheter ablation of LSAP via transseptal approach have been described.
Background
Trans-catheter radiofrequency ablation (TCRFA) has become the treatment of choice for patients suffering from refractory to medical treatment supraventricular tachycardias [ 1 , 2 ]. During percutaneous ablation procedures, catheter location is usually monitored by using fluoroscopy together with the analysis of intracardiac electrograms in order to clarify the mechanisms underlining the arrhythmia and to both locate its origin and record its circuit. This technique may be adequate for several standard ablative procedures, but it has still some limitations concerning the treatment of more complex tachycardia forms.Left-sided accessory pathway (LSAP) may be ablated using two different modalities: conventional approach through the aortic valve, or transseptal puncture of the fossa ovalis. By using the traditional approach, the left atrium is reached by a retrograde way through the left ventricle and crossing the mitral valve [ 3 , 4 ] whereas, with the transseptal puncture, the mitral ring is reached by an anterograde approach. For this reason, this approach has been considered an alternative and complementary technique for the transvenous introduction of catheters into the left cavities of the heart [ 5 - 8 ]. However, transseptal puncture under fluoroscopic guidance alone, might be hampered by some acute and potentially lethal complications that may be challenging even for expert electrophysiologists [ 9 ].With the technological and miniaturization advances of low frequency transducers capable of enhanced tissue penetration, intracardiac echocardiography (ICE) has become feasible and potentially useful for guiding transseptal puncture and ablation procedures, especially when location of specific anatomic landmarks appears to be more crucial [ 10 , 11 ].In this manuscript, two cases of ICE-guided catheter ablation of LSAP via transseptal approach have been described.Case Presentation Case 1 A 24 year-old woman with Wolf-Parkinson-White (WPW) syndrome and recurrent episodes of sustained supraventricular tachycardia, refractory to medical therapy, was referred to our Department in order to attempt TCRFA procedure. The electrophysiological study was performed off therapy using three diagnostic catheters (one decapolar and two quadripolars) which have been positioned in the coronary sinus (CS1 → CS5 = distal → proximal coronary sinus), His bundle region, and high right atrium/right ventricular apex. The clinical arrhythmia was diagnosed as an orthodromic atrio-ventricular re-entrant tachycardia (AVRT) due to a LSAP that was repetitively induced by both right atrial and ventricular programmed electrical stimulation. The length of the tachycardia cycle ranged from 310 to 300 msec. A well-localized accessory pathway insertion was detected in the lateral left free wall with atrial-ventricular (AV) and ventricular-atrial (VA) intervals of fusion noticeable only in CS2 (Fig  1 ). During programmed atrial stimulation and AVRT, the transaortic approach was initially attempted by using a 7F-4 mm bidirectional ablation catheter (Blazer HTD, Boston Scientific). Although very short VA and AV intervals (<50 msec without isoelectric line between the two potentials) and satisfactory mean temperature (54–56 C° for 20–30 sec with less than 30 Watts for each radiofrequency application) were obtained, repeated radiofrequency erogations resulted in a transient interruption of the anomalous connection, with recurrence of retrograde conduction along the accessory pathway and atrioventricular re-entrant tachycardia inducibility after a period of 20–30 min. Therefore, by using a mechanical single element ultrasound 9F-9 MHz catheter, an ICE-guided transseptal approach was attempted in order to cranially map the mitral ring (Ultra ICE Boston Scientific/CVIS San José, CA USA). This approach has provided a 360° two-dimensional imaging on a transverse plane perpendicular to the transducer with a radial field of view of approximately 5 cm in depth. ICE catheter was introduced via femoral vein through a 10F long sheath and advanced into the high right atrium. Careful handling of the catheter, along the interatrial septum, provided optimal view of the fossa ovalis that could be easily recognized as a thin area compared to the surrounding atrial structures. The standard approach to transseptal catheterization using a long sheath and dilator over a Brockenbrough needle, was used [ 5 ]. The tip of the needle-dilator-sheath apparatus was positioned facing the middle portion of the fossa ovalis. Careful up and down movements of ICE catheter allowed a clear visualization of the needle as well as its contact with the septal wall causing the typical "tenting" effect (Fig  2 ), which allowed precise location of the puncture of the needle. Figure 1 Orthodromic AV re-entrant tachycardia.  Orthodromic AV re-entrant tachycardia induction with programmed atrial stimulation. Notice VA fusion on CS2 (lateral portion of the mitral ring; see arrow). Figure 2 Brockenbrough needle and the fossa ovalis.  Brockenbrough needle in right atrium approaching the fossa ovalis (right panel); typical "tenting" of the fossa (see arrow) just before septal puncture (left panel). Note the left atrial free wall close to the interatrial septum. (FO = fossa ovalis; LA = left atrium; RA = right atrium). Accessory pathway was completely and definitively ablated with this approach after two erogations lasting each 40 sec. Although the AV and VA intervals that had been selected to deliver radiofrequency energy were similar to those previously recorded, the only difference was a better AV ratio (Fig  3 ). Such findings might be related to the cranial approach of the atrioventricular ring which has allowed a more stable catheter position on endocardium surface and a lack of lateral sliding, resulting in a higher mean temperature (60° ± 3° vs 54° ± 2°). Radiation exposure was shorter with the transseptal approach (11 vs 19 min) when compared to the retrograde approach. Figure 3 Ablation of the accessory pathway.  Radiofrequency erogation during atrial pacing with maximal pre-excitation. Notice AV fusion (major arrow) followed by AV split (two minor arrows) on the ABLd recording, corresponding to lateral mitral annulus. Case 2 A 61 year-old man was referred to our Department for a TCRFA procedure due to a recurrent sustained supraventricular tachycardia refractory to antiarrhytmic drugs. The electrophysiological study has been performed by using the previously described protocol. An atrioventricular re-entrant tachycardia, due to an overt LSAP, was repetitively induced by atrial and ventricular programmed electrical stimulation. The length of the tachycardia cycle ranged from 340 to 320 msec. The accessory pathway insertion resulted well-localized in the left lateral mitral ring during AVRT and atrial pacing with maximal pre-excitation (Fig  4A,4B ). The trans-aortic approach was firstly attempted by using a 7F- 4 mm bidirectional ablation catheter (Blazer HTD, Boston Scientific). Despite an optimal catheter tip temperature for a reasonable period of time (five erogations reaching a mean temperature of 55° lasting 30–40 sec), only a temporary interruption of the anomalous pathway conduction was obtained. Therefore, ICE-guided transseptal approach was performed as previously described (see  additional file: Movie 1 transseptal puncture.avi ). The approach resulted in a persistent and complete ablation of the accessory pathway after two successful radiofrequency erogations which have been delivered when the VA interval resulted fused and its ratio was 1,5:1. In this case, ICE allowed a more complete mapping of the mitral ring and a confirmation of effective catheter ablation tip contact. As in the previously described case, the superior approach to the left AV ring resulted in a better manipulation of the ablation catheter in addition to a reduction in fluoroscopic time (10 vs 21 min). Figure 4 Left sided accessory pathway.  The shortest AV and VA are recorded in CS2 (see arrows) during programmed atrial stimulation (A) and atrio-ventricular orthodromic re-entrant tachycardia (B) respectively suggesting a left sided posterolateral accessory AV connection.
Case Presentation
Case 1 A 24 year-old woman with Wolf-Parkinson-White (WPW) syndrome and recurrent episodes of sustained supraventricular tachycardia, refractory to medical therapy, was referred to our Department in order to attempt TCRFA procedure. The electrophysiological study was performed off therapy using three diagnostic catheters (one decapolar and two quadripolars) which have been positioned in the coronary sinus (CS1 → CS5 = distal → proximal coronary sinus), His bundle region, and high right atrium/right ventricular apex. The clinical arrhythmia was diagnosed as an orthodromic atrio-ventricular re-entrant tachycardia (AVRT) due to a LSAP that was repetitively induced by both right atrial and ventricular programmed electrical stimulation. The length of the tachycardia cycle ranged from 310 to 300 msec. A well-localized accessory pathway insertion was detected in the lateral left free wall with atrial-ventricular (AV) and ventricular-atrial (VA) intervals of fusion noticeable only in CS2 (Fig  1 ). During programmed atrial stimulation and AVRT, the transaortic approach was initially attempted by using a 7F-4 mm bidirectional ablation catheter (Blazer HTD, Boston Scientific). Although very short VA and AV intervals (<50 msec without isoelectric line between the two potentials) and satisfactory mean temperature (54–56 C° for 20–30 sec with less than 30 Watts for each radiofrequency application) were obtained, repeated radiofrequency erogations resulted in a transient interruption of the anomalous connection, with recurrence of retrograde conduction along the accessory pathway and atrioventricular re-entrant tachycardia inducibility after a period of 20–30 min. Therefore, by using a mechanical single element ultrasound 9F-9 MHz catheter, an ICE-guided transseptal approach was attempted in order to cranially map the mitral ring (Ultra ICE Boston Scientific/CVIS San José, CA USA). This approach has provided a 360° two-dimensional imaging on a transverse plane perpendicular to the transducer with a radial field of view of approximately 5 cm in depth. ICE catheter was introduced via femoral vein through a 10F long sheath and advanced into the high right atrium. Careful handling of the catheter, along the interatrial septum, provided optimal view of the fossa ovalis that could be easily recognized as a thin area compared to the surrounding atrial structures. The standard approach to transseptal catheterization using a long sheath and dilator over a Brockenbrough needle, was used [ 5 ]. The tip of the needle-dilator-sheath apparatus was positioned facing the middle portion of the fossa ovalis. Careful up and down movements of ICE catheter allowed a clear visualization of the needle as well as its contact with the septal wall causing the typical "tenting" effect (Fig  2 ), which allowed precise location of the puncture of the needle. Figure 1 Orthodromic AV re-entrant tachycardia.  Orthodromic AV re-entrant tachycardia induction with programmed atrial stimulation. Notice VA fusion on CS2 (lateral portion of the mitral ring; see arrow). Figure 2 Brockenbrough needle and the fossa ovalis.  Brockenbrough needle in right atrium approaching the fossa ovalis (right panel); typical "tenting" of the fossa (see arrow) just before septal puncture (left panel). Note the left atrial free wall close to the interatrial septum. (FO = fossa ovalis; LA = left atrium; RA = right atrium). Accessory pathway was completely and definitively ablated with this approach after two erogations lasting each 40 sec. Although the AV and VA intervals that had been selected to deliver radiofrequency energy were similar to those previously recorded, the only difference was a better AV ratio (Fig  3 ). Such findings might be related to the cranial approach of the atrioventricular ring which has allowed a more stable catheter position on endocardium surface and a lack of lateral sliding, resulting in a higher mean temperature (60° ± 3° vs 54° ± 2°). Radiation exposure was shorter with the transseptal approach (11 vs 19 min) when compared to the retrograde approach. Figure 3 Ablation of the accessory pathway.  Radiofrequency erogation during atrial pacing with maximal pre-excitation. Notice AV fusion (major arrow) followed by AV split (two minor arrows) on the ABLd recording, corresponding to lateral mitral annulus.
Case 1
A 24 year-old woman with Wolf-Parkinson-White (WPW) syndrome and recurrent episodes of sustained supraventricular tachycardia, refractory to medical therapy, was referred to our Department in order to attempt TCRFA procedure. The electrophysiological study was performed off therapy using three diagnostic catheters (one decapolar and two quadripolars) which have been positioned in the coronary sinus (CS1 → CS5 = distal → proximal coronary sinus), His bundle region, and high right atrium/right ventricular apex. The clinical arrhythmia was diagnosed as an orthodromic atrio-ventricular re-entrant tachycardia (AVRT) due to a LSAP that was repetitively induced by both right atrial and ventricular programmed electrical stimulation. The length of the tachycardia cycle ranged from 310 to 300 msec. A well-localized accessory pathway insertion was detected in the lateral left free wall with atrial-ventricular (AV) and ventricular-atrial (VA) intervals of fusion noticeable only in CS2 (Fig  1 ). During programmed atrial stimulation and AVRT, the transaortic approach was initially attempted by using a 7F-4 mm bidirectional ablation catheter (Blazer HTD, Boston Scientific). Although very short VA and AV intervals (<50 msec without isoelectric line between the two potentials) and satisfactory mean temperature (54–56 C° for 20–30 sec with less than 30 Watts for each radiofrequency application) were obtained, repeated radiofrequency erogations resulted in a transient interruption of the anomalous connection, with recurrence of retrograde conduction along the accessory pathway and atrioventricular re-entrant tachycardia inducibility after a period of 20–30 min. Therefore, by using a mechanical single element ultrasound 9F-9 MHz catheter, an ICE-guided transseptal approach was attempted in order to cranially map the mitral ring (Ultra ICE Boston Scientific/CVIS San José, CA USA). This approach has provided a 360° two-dimensional imaging on a transverse plane perpendicular to the transducer with a radial field of view of approximately 5 cm in depth. ICE catheter was introduced via femoral vein through a 10F long sheath and advanced into the high right atrium. Careful handling of the catheter, along the interatrial septum, provided optimal view of the fossa ovalis that could be easily recognized as a thin area compared to the surrounding atrial structures. The standard approach to transseptal catheterization using a long sheath and dilator over a Brockenbrough needle, was used [ 5 ]. The tip of the needle-dilator-sheath apparatus was positioned facing the middle portion of the fossa ovalis. Careful up and down movements of ICE catheter allowed a clear visualization of the needle as well as its contact with the septal wall causing the typical "tenting" effect (Fig  2 ), which allowed precise location of the puncture of the needle.Accessory pathway was completely and definitively ablated with this approach after two erogations lasting each 40 sec. Although the AV and VA intervals that had been selected to deliver radiofrequency energy were similar to those previously recorded, the only difference was a better AV ratio (Fig  3 ). Such findings might be related to the cranial approach of the atrioventricular ring which has allowed a more stable catheter position on endocardium surface and a lack of lateral sliding, resulting in a higher mean temperature (60° ± 3° vs 54° ± 2°). Radiation exposure was shorter with the transseptal approach (11 vs 19 min) when compared to the retrograde approach.Case 2 A 61 year-old man was referred to our Department for a TCRFA procedure due to a recurrent sustained supraventricular tachycardia refractory to antiarrhytmic drugs. The electrophysiological study has been performed by using the previously described protocol. An atrioventricular re-entrant tachycardia, due to an overt LSAP, was repetitively induced by atrial and ventricular programmed electrical stimulation. The length of the tachycardia cycle ranged from 340 to 320 msec. The accessory pathway insertion resulted well-localized in the left lateral mitral ring during AVRT and atrial pacing with maximal pre-excitation (Fig  4A,4B ). The trans-aortic approach was firstly attempted by using a 7F- 4 mm bidirectional ablation catheter (Blazer HTD, Boston Scientific). Despite an optimal catheter tip temperature for a reasonable period of time (five erogations reaching a mean temperature of 55° lasting 30–40 sec), only a temporary interruption of the anomalous pathway conduction was obtained. Therefore, ICE-guided transseptal approach was performed as previously described (see  additional file: Movie 1 transseptal puncture.avi ). The approach resulted in a persistent and complete ablation of the accessory pathway after two successful radiofrequency erogations which have been delivered when the VA interval resulted fused and its ratio was 1,5:1. In this case, ICE allowed a more complete mapping of the mitral ring and a confirmation of effective catheter ablation tip contact. As in the previously described case, the superior approach to the left AV ring resulted in a better manipulation of the ablation catheter in addition to a reduction in fluoroscopic time (10 vs 21 min). Figure 4 Left sided accessory pathway.  The shortest AV and VA are recorded in CS2 (see arrows) during programmed atrial stimulation (A) and atrio-ventricular orthodromic re-entrant tachycardia (B) respectively suggesting a left sided posterolateral accessory AV connection.
Case 2
A 61 year-old man was referred to our Department for a TCRFA procedure due to a recurrent sustained supraventricular tachycardia refractory to antiarrhytmic drugs. The electrophysiological study has been performed by using the previously described protocol. An atrioventricular re-entrant tachycardia, due to an overt LSAP, was repetitively induced by atrial and ventricular programmed electrical stimulation. The length of the tachycardia cycle ranged from 340 to 320 msec. The accessory pathway insertion resulted well-localized in the left lateral mitral ring during AVRT and atrial pacing with maximal pre-excitation (Fig  4A,4B ). The trans-aortic approach was firstly attempted by using a 7F- 4 mm bidirectional ablation catheter (Blazer HTD, Boston Scientific). Despite an optimal catheter tip temperature for a reasonable period of time (five erogations reaching a mean temperature of 55° lasting 30–40 sec), only a temporary interruption of the anomalous pathway conduction was obtained. Therefore, ICE-guided transseptal approach was performed as previously described (see  additional file: Movie 1 transseptal puncture.avi ). The approach resulted in a persistent and complete ablation of the accessory pathway after two successful radiofrequency erogations which have been delivered when the VA interval resulted fused and its ratio was 1,5:1. In this case, ICE allowed a more complete mapping of the mitral ring and a confirmation of effective catheter ablation tip contact. As in the previously described case, the superior approach to the left AV ring resulted in a better manipulation of the ablation catheter in addition to a reduction in fluoroscopic time (10 vs 21 min).Conclusion Intracardiac echocardiography and catheter ablation procedures During a standard ICE examination, sequential pull-back of the probe from the superior vena cava through the right atrium to the inferior vena cava allows a detailed identification of important structures such as: the crista terminalis; the right atrial appendage; the caval and the coronary sinus orifices; the fossa ovalis; the ascending aorta and its root; the pulmonary artery; the right ventricle and all of the cardiac valves [ 12 - 14 ]. Thus, this technique has the potential to provide a direct visualization of the endocardium and to precisely locate the ablation catheter which can be identified by the highly specific fan-shaped echocardiographic artefact of the large tip of the ablation electrode [ 11 , 12 ]. ICE is a well-recognized tool to guide ablation procedures. Compared to fluoroscopy, which does not provide definition of endocardial structures, ICE gives a highly accurate evaluation of firm and stable tissue contact. This results in a reduced radiofrequency power output. In addition, it is possible to visualize the lesion site and formation, such as swelling and crater formation. Moreover, possible complications such as occurrence of microbubbles, clot formation and pericardial effusion may be promptly detected through this ultrasound technique [ 10 , 15 ]. A recently developed phased-array intracardiac echocardiography device provides two-dimensional and Doppler images of the heart [ 10 ]. Recently, new strategies for ablation of atrial fibrillation (linear atrial ablation and focal ablation of triggers) have been proposed. Phased-Array intracardiac echocardiography enables a direct visualization of the pulmonary veins and allows the assessment of the Doppler flow velocity for all of the pulmonary veins [ 16 ]. This technique has been proved to be helpful in monitoring pulmonary vein isolation in patients with atrial fibrillation by improving the outcome and decreasing the incidence of complications such as pulmonary vein stenosis [ 17 ]. Intracardiac echocardiography and transseptal catheterization Transseptal catheterization is usually performed under fluoroscopic guidance [ 5 ]. However, safe transseptal puncture requires detailed visualization of the fossa ovalis that cannot be obtained through fluoroscopy. Thus, it remains a difficult procedure especially for patients which present anatomic abnormalities such as atrial and aortic root dilatation, musculoskeletal disorders and lipomatous hypertrophy of the atrial septum [ 18 ]. Furthermore, some complications of the transseptal catheterization due to accidental puncture of adjacent structures [ 6 ], such as atrial or aortic perforations, and pericardial tamponade, although rare, can be severe and life threatening. Moreover, in hypovolemic states, the left atrial free wall may be closed to the atrial septum. This potentially dangerous condition can be promptly recognized through the ICE technique, suggesting fluid administration in order to restore an adequate blood volume and to prevent left atrial free wall puncture [ 19 ]. The ability to visualize the anatomy of atrial septum and the localization of the fossa ovalis, may greatly enhance both the safety and the efficacy of the transseptal catheterization without any additional morbidity to the procedure [ 19 , 20 ]. As in the above-described cases, ICE allows a continuous monitoring of this procedure showing the tip of the sheath and Brockenbrough needle placed against the middle of the fossa ovalis immediately prior to the puncture [ 19 , 20 ]. Previous reports suggested the use of both transthoracic and transesophageal echocardiography, but these techniques present some limitations [ 21 , 22 ]. The former fails to display, in detail the fossa ovalis, the latter requires sedation which limits communication with the patient during the procedure and increases the risk of hypoventilation. Intracardiac echocardiography and left-sided accessory pathway LSAP represent the majority (59%) of all accessory pathway locations [ 23 ]. They can be ablated via transaortic approach. However, severe complications have been reported, including aortic dissection, lesion of the aortic valve, late endocarditis, peripheral and cerebral thromboembolic events [ 3 , 4 ]. Some authors, using the transseptal approach, have reported both a decreased procedural duration and radiation exposure, with higher success rate compared to the transaortic technique [ 7 , 24 ]. Two factors have been taken into account: 1) several left accessory pathways exhibit a broad or oblique insertion on the AV ring, so that they require a multisite radiofrequency energy delivery on both the atrial and ventricular sides in order to be ablated; 2) with the transaortic approach left atrio-ventricular ring mapping becomes a cumbersome procedure due to the retrograde crossing of the ablation catheter through the aortic and the mitral valves. In such a situation, the ablation catheter should be carefully manipulated in order to avoid entrapment into the mitral valve apparatus [ 4 ]. The use of ICE during ablation procedures in order to treat LSAP has been previously reported [ 25 ]. The observations pointed out by our case report have shown that ICE provides a precise localization of the needle tip position, a clear visualization of the fossa ovalis, a more complete mapping of the mitral ring and a more effective catheter ablation manipulation as well as tip contact. All of these advantages resulted in a persistent and complete ablation of the LSAP with a shorter time in fluoroscopic exposure in opposition to the transaortic approach. It has also been taken into account that a standard TCRFA procedure involves a radiation burden of about 17–25 mSv which appears to be equivalent to what is usually absorbed from natural radiation exposure in during a time period of 10 years and to about 1000 chest X-ray [ 26 ]. The combined use of ICE allows to reduce to a half the time of fluoroscopic exposure that induces a significant reduction in radiation load and consequent long term oncogenic risk both for patients and physicians [ 27 ]. In conclusion, ICE-guided transseptal approach might be a promising modality for TCRFA of LSAP. However, this report needs to be confirmed by further studies.
Conclusion
Intracardiac echocardiography and catheter ablation procedures During a standard ICE examination, sequential pull-back of the probe from the superior vena cava through the right atrium to the inferior vena cava allows a detailed identification of important structures such as: the crista terminalis; the right atrial appendage; the caval and the coronary sinus orifices; the fossa ovalis; the ascending aorta and its root; the pulmonary artery; the right ventricle and all of the cardiac valves [ 12 - 14 ]. Thus, this technique has the potential to provide a direct visualization of the endocardium and to precisely locate the ablation catheter which can be identified by the highly specific fan-shaped echocardiographic artefact of the large tip of the ablation electrode [ 11 , 12 ]. ICE is a well-recognized tool to guide ablation procedures. Compared to fluoroscopy, which does not provide definition of endocardial structures, ICE gives a highly accurate evaluation of firm and stable tissue contact. This results in a reduced radiofrequency power output. In addition, it is possible to visualize the lesion site and formation, such as swelling and crater formation. Moreover, possible complications such as occurrence of microbubbles, clot formation and pericardial effusion may be promptly detected through this ultrasound technique [ 10 , 15 ]. A recently developed phased-array intracardiac echocardiography device provides two-dimensional and Doppler images of the heart [ 10 ]. Recently, new strategies for ablation of atrial fibrillation (linear atrial ablation and focal ablation of triggers) have been proposed. Phased-Array intracardiac echocardiography enables a direct visualization of the pulmonary veins and allows the assessment of the Doppler flow velocity for all of the pulmonary veins [ 16 ]. This technique has been proved to be helpful in monitoring pulmonary vein isolation in patients with atrial fibrillation by improving the outcome and decreasing the incidence of complications such as pulmonary vein stenosis [ 17 ].
Intracardiac echocardiography and catheter ablation procedures
During a standard ICE examination, sequential pull-back of the probe from the superior vena cava through the right atrium to the inferior vena cava allows a detailed identification of important structures such as: the crista terminalis; the right atrial appendage; the caval and the coronary sinus orifices; the fossa ovalis; the ascending aorta and its root; the pulmonary artery; the right ventricle and all of the cardiac valves [ 12 - 14 ]. Thus, this technique has the potential to provide a direct visualization of the endocardium and to precisely locate the ablation catheter which can be identified by the highly specific fan-shaped echocardiographic artefact of the large tip of the ablation electrode [ 11 , 12 ].ICE is a well-recognized tool to guide ablation procedures. Compared to fluoroscopy, which does not provide definition of endocardial structures, ICE gives a highly accurate evaluation of firm and stable tissue contact. This results in a reduced radiofrequency power output. In addition, it is possible to visualize the lesion site and formation, such as swelling and crater formation. Moreover, possible complications such as occurrence of microbubbles, clot formation and pericardial effusion may be promptly detected through this ultrasound technique [ 10 , 15 ].A recently developed phased-array intracardiac echocardiography device provides two-dimensional and Doppler images of the heart [ 10 ]. Recently, new strategies for ablation of atrial fibrillation (linear atrial ablation and focal ablation of triggers) have been proposed. Phased-Array intracardiac echocardiography enables a direct visualization of the pulmonary veins and allows the assessment of the Doppler flow velocity for all of the pulmonary veins [ 16 ]. This technique has been proved to be helpful in monitoring pulmonary vein isolation in patients with atrial fibrillation by improving the outcome and decreasing the incidence of complications such as pulmonary vein stenosis [ 17 ].Intracardiac echocardiography and transseptal catheterization Transseptal catheterization is usually performed under fluoroscopic guidance [ 5 ]. However, safe transseptal puncture requires detailed visualization of the fossa ovalis that cannot be obtained through fluoroscopy. Thus, it remains a difficult procedure especially for patients which present anatomic abnormalities such as atrial and aortic root dilatation, musculoskeletal disorders and lipomatous hypertrophy of the atrial septum [ 18 ]. Furthermore, some complications of the transseptal catheterization due to accidental puncture of adjacent structures [ 6 ], such as atrial or aortic perforations, and pericardial tamponade, although rare, can be severe and life threatening. Moreover, in hypovolemic states, the left atrial free wall may be closed to the atrial septum. This potentially dangerous condition can be promptly recognized through the ICE technique, suggesting fluid administration in order to restore an adequate blood volume and to prevent left atrial free wall puncture [ 19 ]. The ability to visualize the anatomy of atrial septum and the localization of the fossa ovalis, may greatly enhance both the safety and the efficacy of the transseptal catheterization without any additional morbidity to the procedure [ 19 , 20 ]. As in the above-described cases, ICE allows a continuous monitoring of this procedure showing the tip of the sheath and Brockenbrough needle placed against the middle of the fossa ovalis immediately prior to the puncture [ 19 , 20 ]. Previous reports suggested the use of both transthoracic and transesophageal echocardiography, but these techniques present some limitations [ 21 , 22 ]. The former fails to display, in detail the fossa ovalis, the latter requires sedation which limits communication with the patient during the procedure and increases the risk of hypoventilation.
Intracardiac echocardiography and transseptal catheterization
Transseptal catheterization is usually performed under fluoroscopic guidance [ 5 ]. However, safe transseptal puncture requires detailed visualization of the fossa ovalis that cannot be obtained through fluoroscopy. Thus, it remains a difficult procedure especially for patients which present anatomic abnormalities such as atrial and aortic root dilatation, musculoskeletal disorders and lipomatous hypertrophy of the atrial septum [ 18 ]. Furthermore, some complications of the transseptal catheterization due to accidental puncture of adjacent structures [ 6 ], such as atrial or aortic perforations, and pericardial tamponade, although rare, can be severe and life threatening. Moreover, in hypovolemic states, the left atrial free wall may be closed to the atrial septum. This potentially dangerous condition can be promptly recognized through the ICE technique, suggesting fluid administration in order to restore an adequate blood volume and to prevent left atrial free wall puncture [ 19 ].The ability to visualize the anatomy of atrial septum and the localization of the fossa ovalis, may greatly enhance both the safety and the efficacy of the transseptal catheterization without any additional morbidity to the procedure [ 19 , 20 ]. As in the above-described cases, ICE allows a continuous monitoring of this procedure showing the tip of the sheath and Brockenbrough needle placed against the middle of the fossa ovalis immediately prior to the puncture [ 19 , 20 ].Previous reports suggested the use of both transthoracic and transesophageal echocardiography, but these techniques present some limitations [ 21 , 22 ]. The former fails to display, in detail the fossa ovalis, the latter requires sedation which limits communication with the patient during the procedure and increases the risk of hypoventilation.Intracardiac echocardiography and left-sided accessory pathway LSAP represent the majority (59%) of all accessory pathway locations [ 23 ]. They can be ablated via transaortic approach. However, severe complications have been reported, including aortic dissection, lesion of the aortic valve, late endocarditis, peripheral and cerebral thromboembolic events [ 3 , 4 ]. Some authors, using the transseptal approach, have reported both a decreased procedural duration and radiation exposure, with higher success rate compared to the transaortic technique [ 7 , 24 ]. Two factors have been taken into account: 1) several left accessory pathways exhibit a broad or oblique insertion on the AV ring, so that they require a multisite radiofrequency energy delivery on both the atrial and ventricular sides in order to be ablated; 2) with the transaortic approach left atrio-ventricular ring mapping becomes a cumbersome procedure due to the retrograde crossing of the ablation catheter through the aortic and the mitral valves. In such a situation, the ablation catheter should be carefully manipulated in order to avoid entrapment into the mitral valve apparatus [ 4 ]. The use of ICE during ablation procedures in order to treat LSAP has been previously reported [ 25 ]. The observations pointed out by our case report have shown that ICE provides a precise localization of the needle tip position, a clear visualization of the fossa ovalis, a more complete mapping of the mitral ring and a more effective catheter ablation manipulation as well as tip contact. All of these advantages resulted in a persistent and complete ablation of the LSAP with a shorter time in fluoroscopic exposure in opposition to the transaortic approach. It has also been taken into account that a standard TCRFA procedure involves a radiation burden of about 17–25 mSv which appears to be equivalent to what is usually absorbed from natural radiation exposure in during a time period of 10 years and to about 1000 chest X-ray [ 26 ]. The combined use of ICE allows to reduce to a half the time of fluoroscopic exposure that induces a significant reduction in radiation load and consequent long term oncogenic risk both for patients and physicians [ 27 ]. In conclusion, ICE-guided transseptal approach might be a promising modality for TCRFA of LSAP. However, this report needs to be confirmed by further studies.
Intracardiac echocardiography and left-sided accessory pathway
LSAP represent the majority (59%) of all accessory pathway locations [ 23 ]. They can be ablated via transaortic approach. However, severe complications have been reported, including aortic dissection, lesion of the aortic valve, late endocarditis, peripheral and cerebral thromboembolic events [ 3 , 4 ]. Some authors, using the transseptal approach, have reported both a decreased procedural duration and radiation exposure, with higher success rate compared to the transaortic technique [ 7 , 24 ]. Two factors have been taken into account: 1) several left accessory pathways exhibit a broad or oblique insertion on the AV ring, so that they require a multisite radiofrequency energy delivery on both the atrial and ventricular sides in order to be ablated; 2) with the transaortic approach left atrio-ventricular ring mapping becomes a cumbersome procedure due to the retrograde crossing of the ablation catheter through the aortic and the mitral valves. In such a situation, the ablation catheter should be carefully manipulated in order to avoid entrapment into the mitral valve apparatus [ 4 ].The use of ICE during ablation procedures in order to treat LSAP has been previously reported [ 25 ]. The observations pointed out by our case report have shown that ICE provides a precise localization of the needle tip position, a clear visualization of the fossa ovalis, a more complete mapping of the mitral ring and a more effective catheter ablation manipulation as well as tip contact. All of these advantages resulted in a persistent and complete ablation of the LSAP with a shorter time in fluoroscopic exposure in opposition to the transaortic approach. It has also been taken into account that a standard TCRFA procedure involves a radiation burden of about 17–25 mSv which appears to be equivalent to what is usually absorbed from natural radiation exposure in during a time period of 10 years and to about 1000 chest X-ray [ 26 ]. The combined use of ICE allows to reduce to a half the time of fluoroscopic exposure that induces a significant reduction in radiation load and consequent long term oncogenic risk both for patients and physicians [ 27 ].In conclusion, ICE-guided transseptal approach might be a promising modality for TCRFA of LSAP. However, this report needs to be confirmed by further studies.List of abbreviations AV= atrial-ventricular; AVRNT= atrio-ventricular re-entrant tachycardia; CS= coronary sinus; ICE = intracardiac echocardiography; LSAP= left sided accessory pathway; TCRFA= transcatheter radiofrequency ablation; VA= ventricular-atrial; WPW= Wolf-Parkinson-White.
List of abbreviations
AV= atrial-ventricular;AVRNT= atrio-ventricular re-entrant tachycardia;CS= coronary sinus;ICE = intracardiac echocardiography;LSAP= left sided accessory pathway;TCRFA= transcatheter radiofrequency ablation;VA= ventricular-atrial;WPW= Wolf-Parkinson-White.Competing interests The authors declare that they have no competing interests.
Competing interests
The authors declare that they have no competing interests.Authors' contributions RC carried out intracardiac echocardiography and drafted the manuscript, VD carried out electrophysiological study, AS drafted the manuscript, MS carried out electrophysiological study, MS drafted the revision of the manuscript, GG drafted the manuscript. All authors have read and approved the final manuscript.
Authors' contributions
RC carried out intracardiac echocardiography and drafted the manuscript, VD carried out electrophysiological study, AS drafted the manuscript, MS carried out electrophysiological study, MS drafted the revision of the manuscript, GG drafted the manuscript.All authors have read and approved the final manuscript.Supplementary Material additional file: Movie 1 transseptal puncture.avi Brockenbrough needle immediately after the puncture of the fossa ovalis can be clearly visualized. Click here for file
Supplementary Material
additional file: Movie 1 transseptal puncture.avi
Brockenbrough needle immediately after the puncture of the fossa ovalis can be clearly visualized.Click here for file