[Cardiac resynchronization therapy in refractory heart failure]

Congestive heart failure remains associated with substantial morbidity and mortality. A common finding in advanced heart failure is abnormal electrical activation of the ventricles or electrical ventricular dyssynchrony. In the early 90s, standard dual-chamber pacing with short AV delay was proposed as a supplementary treatment of drug-resistant heart failure. Initial results were encouraging but were never confirmed. These studies however made it possible to select a population of potentially responsive patients, especially those with a prolonged PR interval reflecting major atrioventricular asynchrony in the left heart. That relative failure of standard dual-chamber pacing could be linked to the fact that by capturing the ventricle from the right apex, it increases, or at least it cannot correct the marked asynchrony of activation, contraction and relaxation, which characterizes a number of patients with chronic left ventricular dysfunction. Such is the case in particular in patients with important QRS enlargement linked to major intraventricular conduction delay. Biventricular pacing, which simultaneously activates both ventricles, may contribute to correcting the asynchrony and thus improve cardiac performance.