A left hemiblock improves cardiac resynchronization therapy outcomes in patients with a right bundle branch block.

BACKGROUND

The current recommendation for cardiac resynchronization therapy (CRT) in congestive heart failure (CHF) patients is based on QRS duration, not on QRS morphology.

HYPOTHESIS: This study was performed to compare the effects of CRT in CHF patients with pure RBBB vs those with a coexisting left hemiblock (LHB). METHODS AND PATIENT POPULATION: A total of 271 consecutive patients who underwent CRT at Montefiore Medical Center were analyzed. Baseline ECGs were analyzed by 2 reviewers for RBBB and further classified into those with a coexisting LHB. Response to CRT was defined to be, at > or = 6 months after CRT, either an improvement in ejection fraction (EF) of at least 5%, or an improvement in New York Heart Association (NYHA) CHF class. A total of 44 patients were identified: 18 had pure RBBB and 26 had a coexisting LHB. The 2 groups were similar in respect to baseline characteristics (P > 0.05).

RESULTS

Only 4 out of 18 patients with pure RBBB compared to 18 out of 26 with LHB (P = 0.005) had an improvement in EF > or = 5%. The mean EF was - 1% in the pure RBBB group, but + 5.4% in those with LHB (P = 0.0031). Improvement in NYHA class was seen in 0 out of 18 with pure RBBB vs 7 out of 26 patients with LHB (P = 0.03).

CONCLUSION

If patients with RBBB also had LHB, their response to CRT was significantly better than if they had RBBB alone.