Multisite Biventricular Pacing to Treat Refractory Heart Failure: Why and How?

Abstract

Despite pharmacological advances, in particular the introduction of ACE inhibitors and ß-blockers, the prognosis of patients with severe heart failure (grades III and IV of the NYHA classification) remains pejorative and their quality of life is poor. A number of nonpharmacological treatments have been proposed for this type of patients: heart transplantation remains the reference treatment although its application is restricted by donor shortage, among other factors. Left ventricular (LV) support devices are still at the evaluation stage and the results of cardiomyoplasty are highly controversial. In the early 1990s, standard dual-chamber pacing with short AV delay was proposed as a supplementary treatment for 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 LV 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.