Benefit of Cardiac Resynchronization Therapy for Heart Failure May Be Limited to Patients with Severe QRS Interval Prolongation
DynaMed Weekly Update - Volume 6, Issue 41
Current guidelines from the American College of Cardiology and the American Heart Association (ACC/AHA) recommend cardiac resynchronization therapy (CRT) for patients with NYHA class III or IV heart failure symptoms who have an ejection fraction < 35%, a QRS interval > 120 milliseconds, and are in sinus rhythm (ACC/AHA Class I, Level A recommendation, Circulation 2009 Apr 14;119(14):1977). Systematic reviews have found that CRT may reduce mortality and hospitalization in patients with QRS prolongation, in both patients with class III-IV symptoms (Health Technol Assess 2007 Nov;11(47):iii, Ann Intern Med 2004 Sep 7;141(5):381) and patients with class I-II symptoms ( Ann Intern Med 2011 Mar 15;154(6):401).
A new systematic review examined data from randomized trials that provided subgroup analyses of patients stratified by severity of QRS prolongation. QRS intervals 120-149 milliseconds were classified as moderately prolonged and intervals ? 150 milliseconds as severely prolonged. Analyses included 1,738 patients with class III-IV symptoms (from 2 trials, 64% with severe prolongation) and 4,228 patients with class I-II symptoms (from 3 trials, 60% with severe prolongation).
The primary outcome in all trials was a composite of adverse clinical events including mortality and hospitalization. CRT was associated with reduced risk of adverse clinical events in patients with severely prolonged QRS intervals (level 2 [mid-level] evidence) in the overall analysis (risk ratio [RR] 0.6, 95% CI 0.53-0.67) and in analyses of patients with class III-IV symptoms (RR 0.67, 95% CI 0.57-0.8) and patients with class I-II symptoms (RR 0.47, 95% CI 0.37-0.6). In patients with only moderately prolonged QRS intervals, there were no significant differences in risk overall or in either symptom subgroup (Arch Intern Med 2011 Sep 12;171(16):1454).
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