Effect of Bi-ventricular Pacing on Autonomous Nervous System

Patients with congestive heart failure are often associated with delayed intraventricular depolarization which causing dyssynchrony and an inefficient pattern of left ventricular contraction. A number of studies have shown that bi-ventricular or left ventricular pacing improves indexes of systolic function as well as decreases sympathetic activation in patients with severe left ventricular systolic dysfunction, dilated cardiomyopathy and a major left-sided intraventricular conduction disorder such as left bundle branch block. One recent study also demonstrated that bi-ventricular pacing can shift heart rate variability (HRV) toward a more favorable profile. Baroreflex sensitivity (BRS) is a measure of the negative feedback properties that interact in modulating the dynamic heart rate and arterial pressure fluctuations. Blunted BRS is found to be associated with an increased risk for both cardiac deaths and arrhythmic events. However, the effect of bi-ventricular pacing on BRS has never been studied. In the present proposal, we plan to measure common hemodynamic parameters, BRS and HRV in a group of heart failure patients receiving open heart surgery in different pacing conditions (bi-ventricular pacing, single LV pacing, single RV pacing). The major aims are to investigate the effect of bi-ventricular pacing on BRS and to clarify the underlying mechanisms.