The effect of conduction velocity slowing in left ventricular midwall on the QRS complex morphology: A simulation study.
UNLABELLED
Midwall fibrosis is a frequent finding in different types of left ventricular hypertrophy. Fibrosis presents a local conduction block that can create a substrate for ventricular arrhythmias and lead to the continuous generation of reentry. Having also impact on the sequence of ventricular activation it can modify the shape of QRS complex. In this study we simulated the effects of slowed conduction velocity in the midwall in the left ventricle and in its anteroseptal region on the QRS morphology using a computer model.


MATERIAL AND METHODS
The model defines the geometry of cardiac ventricles analytically as parts of ellipsoids; the left ventricular wall is represented by five layers. The impulse propagation velocity was decreased by 50% in one and two midwall layers, respectively, in the whole left ventricle and in LV anterior region. The effects of slowed conduction velocity on the QRS complex of the 12-lead electrocardiogram are presented as 12-lead electrocardiograms and corresponding values of ECG criteria for left ventricular hypertrophy (ECG-LVH criteria): Gubner criterion, Sokolow-Lyon index (SLI) and Cornell voltage.


RESULTS
All simulated situations led to increased R wave amplitude in the lead I and of S wave in the lead III, showing a leftward shift of the electrical axis and increased values of ECG-LVH criteria based on limb leads alone or in combination with precordial leads (Gubner criterion, Cornell voltage). The slowed conduction velocity in the whole LV influenced the QRS complex voltage in precordial leads, having an impact on the SLI and Cornell voltage. The changes were pronounced if two layers were involved.


CONCLUSION
Using computer modeling we showed that the midwall slowing in conduction velocity modified the QRS complex morphology. The QRS complex changes were consistent with ECG-LVH criteria, i.e. QRS patterns usually interpreted as the effect of left ventricular hypertrophy (the increased left ventricular mass).
['Bacharova|Ljuba|L|', 'Szathmary|Vavrinec|V|', 'Svehlikova|Jana|J|', 'Mateasik|Anton|A|', 'Gyhagen|Julia|J|', 'Tysler|Milan|M|']
D003198:Computer Simulation D004562:Electrocardiography D056966:Excitation Contraction Coupling D006329:Heart Conduction System D006801:Humans D008955:Models, Cardiovascular D009431:Neural Conduction D016277:Ventricular Function, Left
Conduction velocity Midwall QRS complex Left ventricular hypertrophy