Effect of qrs morphology and duration on clinical outcomes after cardiac resynchronization therapy ― Analysis of japanese multicenter registry

Background: QRS duration (QRSd) and morphology are established response predictors of cardiac resynchronization therapy (CRT). However, evidence in Japanese populations is lacking. Methods and Results: We retrospectively analyzed the Japanese multicenter CRT database. We divided patients according to their intrinsic QRSd and morphology, and assessed echocardiographic responses and clinical outcomes. The primary endpoint was a composite of all-cause death or hospitalization because of heart failure. A total of 510 patients were enrolled: 200 (39%) had left bundle branch block (LBBB) and QRSd ≥150 ms; 80 (16%) had LBBB (QRSd: 120–149 ms); 61 (12%) had non-LBBB (NLBBB) (QRSd: ≥150 ms); 54 (11%) had NLBBB (QRSd: 120–149 ms); 115 (23%), narrow (<120 ms). The proportion of echocardiographic responders was higher in LBBB (QRSd ≥150 ms) [74% vs. 51% vs. 38% vs. 52% vs. 50%, LBBB (QRSd ≥150 ms) vs. LBBB (QRSd 120–149 ms) vs. NLBBB (QRSd ≥150 ms) vs. NLBBB (QRSd 120–149 ms) vs. narrow, respectively, P<0.001]. During follow-up (3.2±1.5 years), the incidence of the primary endpoint was lowest in the LBBB group (QRSd ≥150) (28.6% vs. 42.3% vs. 45.9% vs. 55.6% vs. 55.3%, respectively, P<0.001). This difference was still significant after adjusting for other baseline characteristics. Conclusions: In this Japanese patient population, LBBB intrinsic QRS morphology and prolonged QRSd (≥150 ms) exhibited the best response to CRT.