Cardiac Resynchronization Therapy Improves Outcomes in Patients With Intraventricular Conduction Delay But Not Right Bundle Branch Block: A Patient-Level Meta-Analysis of Randomized Controlled Trials

The benefit from cardiac resynchronization therapy (CRT) varies by QRS characteristics; individual randomized trials are underpowered to assess benefits for relatively small subgroups. In this study, CRT was associated with an overall lower risk of HFH or death, and in subgroups of patients with QRS ≥150 ms and either LBBB or IVCD, but not RBBB. No significant association for CRT with HFH or death was observed when QRS was <150 ms or in the presence of RBBB. Similar relationships were observed for all-cause death. The findings suggest that aggregating RBBB and IVCD into a single “non-LBBB” category should be reconsidered when selecting patients for CRT.