The role of atrioventricular delay in left bundle branch stimulation: when diastole is more important than systole

Abstract

We present a clinical case of an 86yearold patient with initially preserved left ventricular ejection fraction, left bundle branch block, and sick sinus syndrome, who underwent implantation of a dualchamber pacemaker with selective left bundle branch pacing. With a programmed short atrioventricular delay (100/120 ms) and a high percentage of ventricular pacing, progression of chronic heart failure, a decrease in left ventricular ejection fraction, and worsening exercise tolerance were observed, without signs of myocardial ischemia, significant tachyarrhythmia, or loss of conduction system capture. Using echocardiographic parameters according to Ritter’s method, an optimal atrioventricular interval was selected, which resulted in restoration of atrioventricular synchrony and an increase in left ventricular ejection fraction.