Cardiac resynchronization therapy

The first case report introducing the concept of cardiac resynchronisation therapy (CRT) was published less than 10 years ago, opening the way to the development of the first successful non-pharmacological treatment of congestive heart failure (CHF). The now routine implantation of CRT systems is applicable to multitudes of patients as adjunctive therapy in advanced CHF. This technique has transformed the traditional concepts associated with stimulation of the heart, and is now applied not only to restore an appropriate heart rate, but also to change the process of cardiac mechanical activation. Since it must be integrated within a comprehensive and multidisciplinary CHF management program, CRT has changed the practice of experts in the field of cardiac pacing. CRT in the management of CHF was ultimately validated in 2 randomised trials. MUSTIC, the first trial, compared in a single-blind, 3x3 months crossover design active versus inactive biventricular stimulation in a group of patients in sinus rhythm and another group in atrial fibrillation. Both phases of the trial were completed by 48 patients, with significant positive effects conferred by CRT on the distance walked in 6 min and on peak oxygen consumption. The number of hospitalizations for management of CHF was decreased by 2/3 (P<0.05), and 85% of patients preferred the atrio-biventricular over the inactive stimulation mode (P<0.001). These results were amply confirmed by the parallel-design MIRACLE trial. The current indications for CRT, diagnostic tools to assist in its implementation, and limitations of this new therapeutic adjunct are further discussed in this review.