Differential Modulation of Electrocardiographic Indices of Ventricular Repolarization Dispersion Depending on the Site of Pacing During Premature Stimulation

Differential Modulation of ECG Indices of Dispersion. Introduction: Dispersion of ventricular repolarization has been shown to increase with premature stimulation. Moreover, a straight correlation between the amount of dispersion of repolarization and the vulnerability to ventricular fibrillation was reported. On the other hand, differences between right ventricular (RV) and left ventricular (LV) fibrillation threshold have been reported. However, no data exist regarding the influence of the site of stimulation on modulation of dispersion of repolarization. Methods and Results: In the present study, several ECG indices of dispersion of repolarization, as a function of the coupling interval and the site of stimulation, were evaluated in a modified Langendorff‐perfused rabbit heart (n = 12), with a 5 × 8 array of a simulated body surface unipolar lead system. As the coupling interval was shortened, a biphasic modulation of dispersion of repolarization was found when stimuli were elicited at the LV. In contrast, when the heart was paced from the RV, the dispersion increased monotonically as coupling interval was shortened. Conclusion: A differential behavior of the modulation of dispersion of repolarization was found as a function of the site of stimulation.