Correlation of scar in cardiac MRI and high-resolution contact mapping of left ventricle in a chronic infarct model.
BACKGROUND
Endocardial mapping for scars and abnormal electrograms forms the most essential component of ventricular tachycardia ablation. The utility of ultra-high resolution mapping of ventricular scar was assessed using a multielectrode contact mapping system in a chronic canine infarct model.


METHODS
Chronic infarcts were created in five anesthetized dogs by ligating the left anterior descending coronary artery. Late gadolinium-enhanced magnetic resonance imaging (LGE MRI) was obtained 4.9 ± 0.9 months after infarction, with three-dimensional (3D) gadolinium enhancement signal intensity maps at 1-mm and 5-mm depths from the endocardium. Ultra-high resolution electroanatomical maps were created using a novel mapping system (Rhythmia Mapping System, Rhythmia Medical/Boston Scientific, Marlborough, MA, USA) Rhythmia Medical, Boston Scientific, Marlborough, MA, USA with an 8.5F catheter with mini-basket electrode array (64 tiny electrodes, 2.5-mm spacing, center-to-center).


RESULTS
The maps contained 7,754 ± 1,960 electrograms per animal with a mean resolution of 2.8 ± 0.6 mm. Low bipolar voltage (<2 mV) correlated closely with scar on the LGE MRI and the 3D signal intensity map (1-mm depth). The scar areas between the MRI signal intensity map and electroanatomic map matched at 87.7% of sites. Bipolar and unipolar voltages, compared in 592 electrograms from four MRI-defined scar types (endocardial scar, epicardial scar, mottled transmural scar, and dense transmural scar) as well as normal tissue, were significantly different. A unipolar voltage of <13 mV correlated with transmural extension of scar in MRI. Electrograms exhibiting isolated late potentials (ILPs) were manually annotated and ILP maps were created showing ILP location and timing. ILPs were identified in 203 ± 159 electrograms per dog (within low-voltage areas) and ILP maps showed gradation in timing of ILPs at different locations in the scar.


CONCLUSIONS
Ultra-high resolution contact electroanatomical mapping accurately localizes ventricular scar and abnormal myocardial tissue in this chronic canine infarct model. The high fidelity electrograms provided clear identification of the very low amplitude ILPs within the scar tissue and has the potential to quickly identify targets for ablation.
['Thajudeen|Anees|A|', 'Jackman|Warren M|WM|', 'Stewart|Brian|B|', 'Cokic|Ivan|I|', 'Nakagawa|Hiroshi|H|', 'Shehata|Michael|M|', 'Amorn|Allen M|AM|', 'Kali|Avinash|A|', 'Liu|Ezh|E|', 'Harlev|Doron|D|', 'Bennett|Nathan|N|', 'Dharmakumar|Rohan|R|', 'Chugh|Sumeet S|SS|', 'Wang|Xunzhang|X|']
D000818:Animals D055424:Cardiac-Gated Imaging Techniques D002921:Cicatrix D003287:Contrast Media D004195:Disease Models, Animal D004285:Dogs D004562:Electrocardiography D019786:Gadolinium DTPA D007091:Image Processing, Computer-Assisted D008279:Magnetic Resonance Imaging D009203:Myocardial Infarction D017180:Tachycardia, Ventricular
ventricular tachycardia ventricular scar magnetic resonance imaging electroanatomical mapping late potentials