Impact of Atrioventricular Delay Optimization on Ventricular Function in Conduction System Pacing

Overview

Conduction system pacing has emerged as a physiological pacing strategy that preserves ventricular electrical activation and minimizes pacing-induced dyssynchrony. However, the optimal atrioventricular delay setting in patients undergoing conduction system pacing remains uncertain. This study aims to evaluate the effects of individualized echocardiography-guided atrioventricular delay optimization on ventricular function and hemodynamic performance in patients with conduction system pacing. Echocardiographic parameters including global longitudinal strain, left ventricular ejection fraction, left ventricular outflow tract velocity-time integral, cardiac output, and diastolic function indices will be assessed before and after atrioventricular delay optimization. The study will investigate whether optimization of atrioventricular timing provides additional mechanical and hemodynamic benefits beyond physiological ventricular activation achieved by conduction system pacing alone.

Conduction system pacing (CSP), including His bundle pacing and left bundle branch area pacing, has emerged as a physiological pacing strategy capable of preserving ventricular electrical activation and reducing pacing-induced dyssynchrony. Compared with conventional right ventricular pacing, CSP has been associated with improved electrical synchrony, ventricular function, and clinical outcomes. Despite restoration of physiological ventricular activation, optimal atrioventricular (AV) coupling remains essential for maximizing ventricular filling, stroke volume, and overall cardiac performance. Inadequate AV timing may impair diastolic filling, reduce atrial contribution to ventricular preload, and limit the hemodynamic benefits achieved by physiological pacing. While AV delay optimization has been extensively investigated in cardiac resynchronization therapy, data regarding its role in patients undergoing CSP remain limited. The present study evaluates the impact of individualized echocardiography-guided AV delay optimization on ventricular mechanical performance and hemodynamic parameters in patients with CSP implanted for atrioventricular block. Comprehensive transthoracic echocardiographic assessment will be performed before and after AV delay optimization. Measurements include left ventricular ejection fraction, global longitudinal strain, left ventricular outflow tract velocity-time integral, cardiac output, chamber dimensions, pulmonary artery systolic pressure, and diastolic function parameters. The primary objective is to determine the effect of AV delay optimization on global longitudinal strain. Secondary objectives include assessment of changes in left ventricular systolic function, hemodynamic performance, and diastolic parameters. The study aims to provide additional evidence regarding the importance of individualized AV programming in patients undergoing conduction system pacing.