Beat-to-beat variations in activation-recovery interval derived from the right ventricular electrogram can monitor arrhythmic risk under anesthetic and awake conditions in the canine chronic atrioventricular block model

Background: In the chronic atrioventricular block (CAVB) dog model, beat-to-beat variation of repolarization in the left ventricle (LV) quantified as short-term variability of the left monophasic action potential duration (STV_LVMAPD) increases abruptly upon challenge with a proarrhythmic drug. This increase occurs before the first ectopic beat (EB), specifically in subjects who demonstrate subsequent repetitive torsades de pointes arrhythmias (TdP). Objective: The purpose of this study was to demonstrate that STV is feasible to monitor arrhythmic risk through use of the intracardiac electrogram (EGM) derived from the right ventricular (RV) lead from pacemakers or implantable cardioverter–defibrillators. Methods: In 30 anaesthetized, inducible (≥3 TdP) CAVB dogs, STV between LV and RV monophasic action potential duration (STV_LVMAPD and STV_RVMAPD) was compared. In prospectively enrolled CAVB dogs, STV of the activation-recovery interval (ARI) derived from the RV EGM (STV_RVARI) was measured before and after a challenge with dofetilide under anesthesia (2a; n = 10) and cisapride under awake conditions (2b; n = 8). Results: Both STV_LVMAPD and STV_RVMAPD increased before the first EB (1.29 ± 0.58 ms to 3.05 ± 1.70 ms and 1.11 ± 0.53 ms to 2.18 ± 1.43 ms, respectively; P = 0.001). STV_RVARI increased from 2.82 ± 0.33 ms to 3.77 ± 0.69 ms (P =.001). Inducible subjects (4/8) showed an increase in STV_RVARI from 2.65 ± 0.55 ms to 3.45 ± 0.33 ms (in the first hour; P =.02) and 4.20 ± 1.33 ms (before the first EB; P =.04). Conclusion: Behavior of STV from the RV and LV is comparable. STV_RVARI increases significantly before the occurrence of an arrhythmia in awake and anaesthetized conditions. This finding can be integrated into devices to monitor arrhythmic risk.