Elsevier

American Heart Journal

Volume 163, Issue 2, February 2012, Pages 260-267.e3
American Heart Journal

Clinical Investigation
Congestive Heart Failure
Effect of QRS morphology on clinical event reduction with cardiac resynchronization therapy: Meta-analysis of randomized controlled trials

https://doi.org/10.1016/j.ahj.2011.11.014Get rights and content

Background

Cardiac resynchronization therapy (CRT) is effective in reducing clinical events in systolic heart failure patients with a wide QRS. Previous retrospective studies suggest only patients with QRS prolongation due to a left bundle-branch block (LBBB) benefit from CRT. Our objective was to examine this by performing a meta-analysis of all randomized controlled trials of CRT.

Methods

Systematic searches of MEDLINE and the Food and Drug Administration official website were conducted for randomized controlled CRT trials. Trials reporting adverse clinical events (eg, all-cause mortality, heart failure hospitalizations) according to QRS morphology were included in the meta-analysis.

Results

Four randomized trials totaling 5,356 patients met the inclusion criteria. In patients with LBBB at baseline, there was a highly significant reduction in composite adverse clinical events with CRT (RR = 0.64 [95% CI (0.52-0.77)], P = .00001). However no such benefit was observed for patients with non-LBBB conduction abnormalities (RR = 0.97 [95% CI (0.82-1.15)], P = .75). When examined separately, there was no benefit in patients with right-bundle branch block (RR = 0.91 [95% CI (0.69-1.20)], P = .49) or non-specific intraventricular conduction delay (RR = 1.19 [95% CI (0.87-1.63)], P = .28). There was no heterogeneity among the clinical trials with regards to the lack of benefit in non-LBBB patients (I2 = 0%). When directly compared, the difference in effect of CRT between LBBB versus non-LBBB patients was highly statistically significant (P = .0001 by heterogeneity analysis).

Conclusions

While CRT was very effective in reducing clinical events in patients with LBBB, it did not reduce such events in patients with wide QRS due to other conduction abnormalities.

Section snippets

Literature search

A systematic search of MEDLINE through January 2011 was performed to identify all published randomized controlled trials of CRT that reported clinical outcomes (including death and heart failure hospitalizations) according to bundle-branch block morphology. MEDLINE search terms of (heart failure and cardiac resynchronization therapy) limited to randomized controlled trials returned 113 articles. Additional search of the FDA website returned an additional trial with extractable data. The

Search results

The results of the literature search are shown in Figure 1. A total of 4 randomized controlled trials enrolling 5,356 patients (3,009 CRT, 2,347 controls) met the inclusion criteria for this meta-analysis.10, 11, 12, 13, 14 The PRISMA guideline for reporting meta-analyses is presented in the online Appendix A. A list of excluded trials and the reasons for exclusion are presented in the online Appendix B.

Study characteristics

Trial characteristics are presented in Table I. The COMPANION10 trial had 3 arms (medical

Discussion

Our results show that in patients with a LBBB, CRT is very effective in reducing adverse events with a relative risk reduction of 36% (P = .00001). Conversely, no benefit was observed in patients with other types of conduction abnormalities and a QRS duration >120 milliseconds. The narrow confidence interval for patients with QRS prolongation not due to LBBB rules out even a 20% relative risk reduction for these patients (P = .75).

The majority of studies evaluating CRT in patients with non-LBBB

Acknowledgements

Contributors:

Study concept and design - Sipahi, Fang.

Literature search - Sipahi, Chou, Hyden.

Data collection - Sipahi, Hyden.

Statistical analysis – Sipahi, Rowland.

Analysis and interpretation of data - Sipahi, Simon, Fang.

Drafting of the manuscript - Sipahi, Chou, Hyden.

Critical revision of the manuscript - Sipahi, Chou, Hyden, Rowland, Simon, Fang.

Study supervision - Sipahi, Simon, Fang.

Other Contributors: None.

Financial and material support: None.

Potential Financial Conflicts of Interest:

Dr.

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