Cardiac Resynchronization Therapy: Is Atrial Resynchronization Important with Biventricular Pacing?

Cardiac resynchronization therapy performed with biventricular pacing has been recognized as one of the most promising techniques in the treatment of patients with congestive heart failure [1–3]. Many papers demonstrate significant hemodynamic improvement in patients with severe left ventricular dysfunction and left bundle branch block treated with VDD biventricular pacing and shortened atrioventricular (AV) delays [1–4]. The concept is that biventricular pacing may be an effective pacing modality by synchronizing contraction of the right and left ventricles, leading to improvement of cardiac performance and reduction of mitral regurgitation. Some authors have emphasized the importance of optimization of the stimulation site during ventricular resynchronization therapy and concluded that a posterior/lateral/posterior- lateral left ventricle lead position in combination with a right ventricle apex lead position provides more consistent hemodynamic improvements [5]. Recently published trials have shown a substantial improvement in symptoms, cardiac function, and functional capacity and a less consistent effect on hospitalization, but no convincing evidence for a reduction in cardiac mortality [4]. However, cardiac resynchronization probably is not yet optimal, and many technical and physiopathological concepts are under debate. The subject of this paper is the importance of atrial resynchronization and, consequently, the importance of optimization of the AV delay on both the right and the left sides of the heart.