A novel pacing method to suppress repolarization alternans in vivo: Implications for arrhythmia prevention

Background Repolarization alternans (RA), a pattern of ventricular repolarization that repeats on an every other beat basis, has been closely linked with the substrate associated with ventricular tachycardia/ventricular fibrillation. Objective To evaluate a novel method to suppress RA. Methods We have developed a novel method to dynamically (on R-wave detection) trigger pacing pulses during the absolute refractory period. We have tested the ability of this method to control RA in a structurally normal swine heart in vivo. Results RA induced by triggered pacing can be measured from both intracardiac and body surface leads and the amplitude of R-wave triggered pacing-induced alternans can be locally modulated by varying the amplitude and width of the pacing pulse. We have estimated that to induce a 1 μV change in alternans voltage on the body surface, coronary sinus, and left ventricle leads, a triggered pacing pulse delivered in the right ventricle of 0.04±0.02, 0.05±0.025, and 0.06±0.033 μC, respectively, is required. Similarly, to induce a 1 unit change in K score (ratio of alternans peak to noise), a pacing stimulus of 0.93±0.73, 0.32±0.29, and 0.33±0.37 μC, respectively, is required. We have been able to demonstrate that RA can be suppressed by R-wave triggered pacing from a site that is within or across ventricles. Lastly, we have demonstrated that the proposed method can be used to suppress spontaneously occurring alternans in the diseased heart. Conclusion We have developed a novel method to suppress RA in vivo.