Study Confirms Benefits of CRT in Patients with Heart Failure

Research published in the Canadian Medical Association Journal demonstrates that “cardiac resynchronization therapy (CRT) shows major benefit in reducing mortality in people with heart failure when combined with optimal medical therapy or implantable cardioverter defibrillator.”

In the paper “Cardiac Resynchronization Therapy: A Meta-analysis of Randomized Controlled Trials,” published online ahead of print on the website of the Canadian Medical Association Journal, the authors performed a meta-analysis of the RAFT trial (Resynchronization/Defibrillation for Ambulatory Heart Failure Trial) and other clinical studies to assess “the effect on mortality of cardiac resynchronization therapy with and without an implantable defibrillator among patients with mildly symptomatic and advanced heart failure.”

The researchers identified 12 clinical studies that involved patients with “mildly symptomatic or advanced heart failure, with a QRS interval of more than 120 ms,” in which the patients received “optimal medical therapy” (defined as “evidence-based use of angiotensin-converting-enzyme (ACE) inhibitors or angiotensin II receptor blockers, beta-blockers, spironolactone (if indicated) and diuretics at a stable dose for at least one month”) in conjunction with cardiac resynchronization therapy with or without an implantable cardioverter defibrillator. The authors compared intervention with cardiac resynchronization therapy versus optimal medical therapy alone, and cardiac resynchronization therapy with an implantable defibrillator versus a standard implantable defibrillator.

The 12 trials included in the study enrolled more than 7,500 patients, including more than 4,200 in cardiac resynchronization therapy groups. Five trials compared cardiac resynchronization therapy plus optimal therapy with optimal medical therapy alone; seven compared cardiac resynchronization therapy and an implantable defibrillator with an implantable defibrillator. Follow up ranged from 3 to 40 months (five studies had follow up of 12 months or less). Four studies enrolled only patients with NYHA class I or II heart failure; four studies enrolled only patients with NYHA class III or IV disease. In the remaining four studies, 8%—80% of patients had NYHA class I or II disease and 20%–92% had NYHA class III or IV disease.

The five studies that evaluated the effect on mortality of cardiac resynchronization therapy plus optimal medical therapy versus optimal medical therapy alone enrolled patients with NYHA class III or IV heart failure. IN these studies, patients experienced “a significant relative risk reduction of 27% in mortality.” Actually, although all five studies reported a risk reduction in mortality, only the largest of the group (the CARE-HF [Cardiac Re-synchronization in Heart Failure] study) reported a significant reduction. Without this study, the reduction in mortality in the treatment group “was not significant compared with optimal medical therapy alone.”

The seven studies that looked at cardiac resynchronization therapy and an implantable defibrillator, in addition to optimal medical therapy, enrolled patients with a wide range of NYHA classifications. Patients in these studies experienced “a significant relative risk reduction of 17%.” Interestingly, three of the studies reported a relative risk reduction in mortality, while three reported a risk increase. Only the largest study (the RAFT Study) reported a significant relative risk reduction (20% for RAFT), without which the reduction in mortality with the intervention of cardiac resynchronization therapy and an implantable defibrillator “was not significant.”

The authors report that these findings indicate “an unequivocal benefit of cardiac resynchronization therapy in addition to optimal medical therapy or an implantable cardioverter defibrillator in reducing all-cause mortality,” an effect that was “particularly evident among patients with NYHA class II heart failure.”

George Wells, MD, University of Ottawa Heart Institute, one of the authors of the study, said that this data, especially when combined with the findings of the RAFT trial, confirms that “the cumulative evidence is now conclusive that the addition of cardiac resynchronization therapy to optimal medical therapy or to implantable defibrillator significantly reduces mortality among patients with mildly symptomatic or advanced heart failure.”

A PDF of the full-text version of the article is available for download.