Usefulness of ventricular sense response in last-generation cardiac resynchronization therapy devices

High percentages of pacing were associated to maximal symptomatic and mortality benefit from cardiac resynchronization therapy (CRT). Loss of CRT pacing is linked to intrinsic ventricular activation preceding biventricular pacing (BiV), as it occurs in patients with atrial fibrillation (AF). Last generation CRT devices incorporate the ventricular sense response (VSR) mechanism to maintain biventricular pacing in patients with atrial arrhythmias. This work aimed to characterize electrical dyssynchrony differences among baseline, BiV and VSR pacing, and determine whether the VSR mode is as beneficial as the BiV mode in terms of electrical dyssynchrony.

Thirty-two patients implanted with CRT devices were retrospectively studied. All patients presented non-ischemic dilated myocardiopathy and complete left bundle branch block (LBBB). Every patient went through baseline, BiV and VSR pacing while recording the 12‑lead ECG. Electrical dyssynchrony was assessed by a dyssynchrony index (DIn) obtained from correlation analysis on the 12‑lead ECG.

When comparing with baseline, VSR pacing improved QRS duration (178 ± 22 ms vs 158 ± 43 ms, baseline vs VSR, p < 0.05) and so did BiV pacing (178 ± 22 ms vs 142 ± 20 ms, baseline vs BiV, p < 0.05). However, electrical dyssynchrony only improved at BiV pacing (2.86±0.6 vs 0.54±0.8, baseline vs BiV, p < 0.05) while VSR showed average DIn values similar to those at baseline.

VSR pacing did not improve the electrical synchrony while did shorten QRS duration in this sample population. Therefore, VSR paced beats would fall in the category of inefficient BiV and may not be the preferred alternative in patients with CRT and AF.