Systematic Review: Cardiac Resynchronization in Patients with Symptomatic Heart Failure

BACKGROUND: Even with optimal pharmacotherapy, symptomatic heart failure is associated with substantial morbidity and mortality. PURPOSE: To determine the efficacy and safety of cardiac resynchronization therapy in adults with advanced systolic heart failure. DATA SOURCES: The Cochrane Central Register of Controlled Trials (2002, volume 4), MEDLINE (1980-2003), EMBASE (1980-2003), other electronic databases, and U.S. Food and Drug Administration reports. We contacted primary study authors and device manufacturers, and we hand searched bibliographies of relevant papers and conference proceedings. STUDY SELECTION: Randomized, controlled clinical trials for efficacy and controlled trials plus prospective cohort studies for safety. DATA EXTRACTION: Two reviewers chose studies and extracted data independently; random-effects models were used for analyses. DATA SYNTHESIS: Nine trials were included in the efficacy review (3216 patients). All trial participants had reduced ejection fraction and prolonged QRS duration, and 85% had New York Heart Association (NYHA) class III or IV symptoms. Cardiac resynchronization therapy improved ejection fraction (weighted mean difference, 0.035 95% CI, 0.015 to 0.055), quality of life (weighted mean reduction in score on the Minnesota Living with Heart Failure Questionnaire, 7.6 points CI, 3.8 to 11.5 points), and function (58% vs. 37% of patients improved by at least 1 NYHA class). Heart failure hospitalizations were reduced by 32% (relative risk RR, 0.68 CI, 0.41 to 1.12), with benefits most marked in patients with NYHA class III or IV symptoms at baseline (RR, 0.65 CI, 0.48 to 0.88; number needed to treat for benefit NNT(B), 12). All-cause mortality was reduced by 21% (RR, 0.79 CI, 0.66 to 0.96; NNT(B), 24), driven largely by reductions in death from progressive heart failure (RR, 0.60 CI, 0.36 to 1.01). Eighteen studies (total of 3701 patients with cardiac resynchronization devices) were included in the safety review. Implant success rate was 90% (CI, 89% to 91%), and 0.4% of patients died during implantation (CI, 0.2% to 0.7%). Over a median 6-month follow-up, leads dislodged in 9% of patients (CI, 7% to 10%) and mechanical malfunctions occurred in 7% (CI, 5% to 8%). LIMITATIONS: These trials enrolled only patients with heart failure with NYHA class III or IV symptoms despite medical therapy, a prolonged QRS duration, and reduced ejection fraction; in addition, experienced providers implanted the devices. Because all but one of these trials randomly assigned patients after device implantation, their results may overestimate the potential benefits of cardiac resynchronization. Finally, since few patients in these trials had bradyarrhythmias or atrial fibrillation, the role of cardiac resynchronization in such patients is uncertain. CONCLUSIONS: In selected patients with heart failure, cardiac resynchronization therapy improves functional and hemodynamic status, reduces heart failure hospitalizations, and reduces all-cause mortality.