Adaptive Cardiac Resynchronization Therapy Effect on Electrical Dyssynchrony (aCRT-ELSYNC): a randomized controlled trial

Introduction Adaptive cardiac resynchronization therapy (aCRT) is known to have clinical benefits over conventional CRT; however, their effects on the electrical dyssynchrony have not been compared. Methods We conducted a double-blind, randomized controlled trial in patients receiving CRT for routine clinical indications. Participants underwent cardiac computed tomography and 128-electrodes body surface mapping. We measured electrical dyssynchrony on the epicardial surface using noninvasive electrocardiographic imaging (ECGI) before and 6 months post-CRT. Ventricular electrical uncoupling (VEU) was calculated as the difference between the mean left ventricular (LV) and right ventricular (RV) activation times. An electrical dyssynchrony index (EDI) was computed as the standard deviation of local epicardial activation times. Results We randomized 27 participants (mean age 64±12 y; 34% female; 53% ischemic cardiomyopathy; LV ejection fraction 28±8%; QRS duration 155±21 ms; strict left bundle branch block (LBBB) in 13%). In atypical LBBB (n=11;41%) with S-waves in V 5 -V 6 , conduction block occurred in the anterior RV, as opposed to the interventricular groove in those who met the strict LBBB criteria. As compared to baseline, VEU reduced post-CRT in aCRT (median reduction 18.9(interquartile range 4.3-29.2 ms; P=0.034), but not in conventional CRT (21.4(−30.0 to 49.9 ms; P=0.525) group. There were no differences in the degree of change in VEU and EDI indices between treatment groups. Conclusion The effect of aCRT and conventional CRT on electrical dyssynchrony is largely similar. Further studies are needed to investigate if atypical LBBB with prominent S wave in V 5 -V 6 responds to His bundle pacing.