Has mechanical dyssynchrony still a role in predicting cardiac resynchronization therapy response?

Unlabelled: Current guidelines for cardiac resynchronization therapy (CRT) include electrical but not mechanical dyssynchrony assessment. Our study aims to investigate the effects of isolated or combined mechanical and electrical dyssynchrony, according, respectively, to a standard deviation of tissue Doppler imaging (TDI) derived time to systolic peak ≥32.6 ms and to a QRS duration ≥120 ms, in predicting CRT reverse remodeling.

Method: One hundred ninety-two CRT patients were studied. All patients underwent a complete standard and TDI echocardiography examination before and 6 months after CRT. According to baseline evaluation patients were divided into Group 1, patients with isolated electrical dyssynchrony (QRS ≥ 120 ms, TS-SD < 32.6), Group 2, patients with isolated mechanical dyssynchrony (QRS < 120 ms, TS-SD ≥ 32.6) and Group 3, patients with combined electrical and mechanical dyssynchrony (QRS ≥ 120 ms, TS-SD ≥ 32.6). Patients were considered CRT responders according to ≥15 left ventricular end-systolic volume (LVESV) reduction at follow-up (FU).

Result: At FU, 86 (45%) patients were responders. The highest CRT response rate was observed in Group 3 (62/119, 52%, P < 0.001 vs. Group 1). No significant differences in response rate were observed between Group 1 (13/47, 27%) and Group 2 (11/26, 42%). In Group1, CRT did not induce any significant change in LV end-diastolic volume (LVEDV), LVESV, LV ejection fraction (LVEF), myocardial performance index (MPI), while in Group 2, LVEF (P < 0.001) and MPI (P < 0.05) were improved. In Group 3, LVEDV, LVESV, LVEF, MPI were significantly improved (P < 0.0001 for all).

Conclusion: Our data demonstrate that the highest CRT response rate can be achieved by combining traditional QRS criterion and a currently used echocardiographic dyssynchrony parameter.