Cardiac resynchronization therapy for patients with left ventricular systolic dysfunction: a systematic review.

CONTEXT: Left ventricular (LV) systolic dysfunction causes substantial morbidity and mortality, even with optimal pharmacotherapy. Atrial-synchronized biventricular pacemakers (cardiac resynchronization therapy [CRT]) received US Food and Drug Administration (FDA) approval for use in selected patients with LV systolic dysfunction in 2001.

OBJECTIVE: To summarize the current evidence base for the efficacy, effectiveness, and safety of CRT in patients with LV systolic dysfunction.

EVIDENCE ACQUISITION: A search of multiple electronic databases until November 2006 was supplemented by hand searches of reference lists of included studies and review articles, proceedings booklets from meetings, FDA reports, and contact with primary study authors and device manufacturers. A total of 14 randomized trials (4420 patients) were included for the CRT efficacy review, 106 studies (9209 patients) for the CRT effectiveness review, and 89 studies (9677 patients) reported safety outcomes with implantation of a CRT device.

EVIDENCE SYNTHESIS: All patients in the CRT studies had LV systolic dysfunction (mean LV ejection fraction [LVEF] range, 21%-30%), prolonged QRS duration (mean range, 155-209 milliseconds), and 91% had New York Heart Association (NYHA) class 3 or 4 heart failure symptoms despite optimal pharmacotherapy. CRT improved LVEF (weighted mean difference, 3.0%; 95% confidence interval [CI], 0.9%-5.1%), quality of life (weighted mean reduction in Minnesota Living With Heart Failure Questionnaire, 8.0 points; 95% CI, 5.6-10.4 points), and functional status (improvements of >/=1 NYHA class were observed in 59% of CRT recipients in the randomized trials). CRT decreased hospitalizations by 37% (95% CI, 7%-57%), and all-cause mortality decreased by 22% (95% CI, 9%-33%). Implant success rate was 93.0% (95% CI, 92.2%-93.7%) and 0.3% of patients died during implantation (95% CI, 0.1%-0.6%). During a median 11-month follow-up, 6.6% (95% CI, 5.6%-7.4%) of CRT devices exhibited lead problems and 5% (95% CI, 4%-7%) malfunctioned.

CONCLUSIONS: CRT reduces morbidity and mortality in patients with LV systolic dysfunction, prolonged QRS duration, and NYHA class 3 or 4 symptoms when combined with optimal pharmacotherapy. The incremental benefits of combined CRT plus implantable cardioverter-defibrillator devices vs CRT-alone devices in patients with LV systolic dysfunction remain uncertain.