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

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.

Inclusion criteria

• Age between 18 and 80 years
• Permanent conduction system pacing implantation for atrioventricular block
• At least 1 month elapsed since device implantation
• Sinus rhythm at the time of enrollment
• Left ventricular ejection fraction >40%
• Adequate echocardiographic image quality for comprehensive assessment
• Ability and willingness to provide informed consent

Exclusion criteria

• Permanent or persistent atrial fibrillation
• Significant valvular heart disease
• Active malignancy
• Severe systemic illness with limited life expectancy
• Sinus node dysfunction requiring alternative pacing strategies
• Inadequate echocardiographic image quality
• Inability to comply with study procedures
• Refusal to participate in the study