Congestive heart failure (CHF) is a common condition that has a poor prognosis despite recent advances. New treatments are needed to reduce sudden cardiac death in early and less-symptomatic cases and to reduce progressive failure and death among more symptomatic patients. Electrophysiologic treatments may be helpful because of intraventricular conduction disruptions occurring in heart failure. Atrial-synchronized biventricular pacing (cardiac resynchronization therapy) and implantable cardioverter-defibrillators (ICDs) have been studied for this purpose. ICDs clearly reduce mortality in patients with heart failure who have a history of ventricular arrhythmias. Cardiac resynchronization improves left ventricular filling time and reduces mitral regurgitation and septal dyskinesis, but a positive effect on mortality has not been demonstrated. McAlister and associates performed a systematic review examining the success rate, safety, and efficacy of biventricular pacemaker implantation.

Studies that investigated cardiac resynchronization therapy on patients with symptomatic heart failure were screened independently before inclusion in the review. Nine trials evaluating all-cause mortality met inclusion criteria. Cardiac resynchronization demonstrated significant mortality reduction with benefits apparent within three months of implantation.

Review of the seven trials that looked at progressive heart failure mortality favored cardiac resynchronization but did not reach statistical significance. Hospitalizations were reduced significantly among patients with New York Heart Association (NYHA) class III or IV symptoms who had undergone cardiac resynchronization therapy. NYHA functional class and quality of life also improved by at least one class with resynchronization. The use of beta blockers or digoxin (Lanoxin) did not affect the benefits of cardiac resynchronization therapy. One periprocedural death occurred for every 240 patients undergoing implantation, and over an average of six months, 7 percent of resynchronization devices malfunctioned, and leads dislodged in 9 percent.

The authors conclude that cardiac resynchronization therapy reduces all-cause mortality by 20 percent; heart failure hospitalizations among patients with class III and IV symptoms by 35 percent; and improves quality of life and functional status when added to medical therapy in patients with symptomatic CHF, prolonged QRS duration, and decreased left ventricular ejection fraction. Implantation of a biventricular pacemaker requires technical skill, and some may malfunction or be disrupted by lead dislodgement, but patient tolerability of the procedure is high. Cardiac resynchronization appears to be a useful adjunct in the management of patients with advanced CHF, but medical management and patient education remain the cornerstones of treatment.

editor’s note: In an accompanying editorial, Hlatky and Massie¹ note that the evidence supporting improvement in the quality of life among patients with heart failure using cardiac resynchronization therapy is clear. The evidence on reduced mortality is less convincing, because none of the independent studies demonstrated a statistically significant reduction. Flaws, such as overlapping mortality benefit of ICDs inserted at the same time, limit the collection of mortality results in the studies. Cost-effectiveness of cardiac resynchronization is favorable if care is used in choosing patients whose quality of life would be improved substantially by use of this procedure. Future devices probably will include cardiac resynchronization and ICD capabilities. The cost-effectiveness of these combined devices needs further study. At present, cardiac resynchronization should be considered in patients with heart failure, an ejection fraction of 35 percent or less, and a QRS duration of 120 milliseconds or greater who remain symptomatic despite careful medical, fluid, and diet management.—r.s.