Cardiac resynchronization therapy reduces death, HF hospitalization in patients with IVCD but not RBBB: Circulation

The study, published in the journal, Circulation, found that in patients with IVCD or left bundle branch block (LBBB), cardiac resynchronization therapy (CRT) helped outcomes but not for those with RBBB. The researchers suggest reconsidering aggregating RBBB and IVCD into a single "non-LBBB" category during patients' selection for CRT.

The benefit from cardiac resynchronization therapy differs by QRS characteristics; individual randomized trials are underpowered to evaluate usefulness for relatively small subgroups. Daniel J Friedman from Duke University School of Medicine in Durham, NC, and colleagues analyzed patient-level data from pivotal CRT trials: MIRACLE, MIRACLE-ICD, MIRACLE-ICD II, REVERSE, RAFT, BLOCK-HF, MADIT-CRT, and COMPANION using Bayesian Hierarchical Weibull survival regression models.

They assessed CRT benefit by QRS morphology (LBBB, n=4549, RBBB, n=691; and IVCD, n=1024 and duration (with 150-ms partition). The primary endpoint was time to death or heart failure hospitalization; a secondary endpoint was time to all-cause death.

The study led to the following findings:

· Of 6264 patients included, 25% were women, the median age was 66 [interquartile range, 58 to 73] years, and 61% received CRT (with or without an implantable cardioverter defibrillator).

· CRT was associated with an overall lower risk of HFH or death (hazard ratio [HR], 0.73), and in subgroups of patients with QRS ≥150 ms and either LBBB (HR, 0.56) or IVCD (HR, 0.59), but not RBBB (HR 0.97).

· No significant association for CRT with HFH or death was observed when QRS was <150 ms (regardless of QRS morphology) or in the presence of RBBB. Similar relationships were observed for all-cause death.

"Cardiac resynchronization therapy in patients with QRS ≥150 ms and LBBB or IVCD is associated with reduced death or hospitalization for heart failure but not for those with RBBB," the researchers wrote.

"Lumping RBBB and IVCD together into a single "non-LBBB" category should be reconsidered when selecting patients for CRT," they conclude.

Reference:

Friedman DJ, Al-Khatib SM, Dalgaard F, Fudim M, Abraham WT, Cleland JGF, Curtis AB, Gold MR, Kutyifa V, Linde C, Tang AS, Ali-Ahmed F, Olivas-Martinez A, Inoue LYT, Sanders GD. 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. Circulation. 2023 Jan 26. doi: 10.1161/CIRCULATIONAHA.122.062124. Epub ahead of print. PMID: 36700426.