The rationale behind ventricular resynchronization.

Biventricular pacing or cardiac resynchronization therapy was first proposed in 1994 as a form of non-pharmacological therapy in patients with heart failure and intraventricular and atrioventricular conduction delay, refractory to medical therapy. In this group of patients the presence of ventricular dyssynchrony is associated with progressive adverse remodeling and worsening of systolic and diastolic performance and carries independent prognostic significance. Acute clinical studies have demonstrated hemodynamic benefit as well as improved systolic and diastolic ventricular performance. Also, most clinical short- and medium-term studies have shown clinical and hemodynamic improvement associated with reverse ventricular remodeling. It has recently been demonstrated that cardiac resynchronization therapy reduces morbidity and mortality. This paper analyzes the pathophysiology of abnormal electrical conduction and the acute and chronic response to cardiac resynchronization, and reviews the most relevant aspects of the various trials.