Patients with moderate to severe heart failure see improved functional status, exercise capacity, and quality of life with implantable devices that combine cardiac resynchronization therapy and cardioverter defibrillator functions, according to a study in the May 28th issue of The Journal of the American Medical Association.

James B. Young, M.D., and his colleagues in the Multicenter InSync ICD Randomized Clinical Evaluation (MIRACLE ICD) trial examined the efficacy and safety of combined cardiac resynchronization therapy and implantable cardioverter defibrillator therapy in patients with advanced congestive heart failure.

The study was a randomized, double-blind trial conducted from October 1999 to August 2001 that involved 369 patients at high risk of life-threatening ventricular arrhythmias and with New York Heart Association class III or IV heart failure (328 and 41 patients, respectively) despite optimized medical treatment.

All patients received devices with combined capabilities, with 182 serving as controls (cardioverter defibrillator activated, resynchronization off) and 187 in the cardioverter defibrillator/ dual-function group (cardioverter defibrillator and resynchronization activated).

At 6 months, patients assigned to the dual-function group had a greater improvement in average quality of life score and functional class than controls. However, there was no difference in the change in distance walked in 6 minutes. There was a greater increase in peak oxygen consumption in the dual-function group than in controls. No significant differences were observed in changes in left ventricular size or function, overall heart failure status, survival, and rates of hospitalization. The capability to terminate an abnormal heart rhythm was not impaired.

The authors conclude, "cardiac resynchronization therapy without interfering with cardioverter defibrillator functions improved the quality of life, functional capacity, and cardiopulmonary exercise test performance of patients with moderate to severe heart failure ... and life-threatening ventricular arrhythmias. These therapeutic effects were observed in the context of appropriate preexistent and continuing vigorous medical management of these patients."

In an accompanying editorial, David J. Bradley, M.D., Ph.D., wrote, "The MIRACLE ICD trial is an important step forward in understanding the role of device therapy for heart failure. History shows that when 2 beneficial therapies are combined, unanticipated outcomes and even harm can occur. In the case of these devices, however, MIRACLE ICD demonstrates that, for a selected group of patients with heart failure, treatment with these devices can improve quality of life and functional class without compromising cardioverter defibrillator function. Ongoing and future studies will refine and possibly expand the indications for this promising therapy."