Atrioventricular Delay Optimization in His-Optimized Cardiac Resynchronization Therapy: A Case Report.

His bundle pacing (HBP) has recently emerged as a physiologic pacing strategy that preserves ventricular synchrony and may improve outcomes in patients with heart failure and conduction abnormalities. Optimization of the atrioventricular (AV) delay plays a pivotal role in ensuring hemodynamic efficiency in patients with conduction system pacing. We report a 41-year-old male with dilated cardiomyopathy and severe heart failure (NYHA class IV, EF 16%), who was initially implanted with a cardiac resynchronization therapy (CRT) device. Despite multiple attempts to reposition the right and left ventricular leads, QRS duration during biventricular pacing widened from 140 to 185 ms. The right ventricular lead was subsequently repositioned to the His bundle (His-optimized CRT, HOT-CRT). Following AV delay optimization, the QRS duration narrowed to 120 ms, improving hemodynamic function. At 15-month follow-up, the patient remained clinically stable, able to perform moderate physical activity, with an improved EF of 25% and no recurrence of ventricular tachycardia. HOT-CRT combines the physiologic advantage of His bundle pacing with optimized AV conduction timing, which is particularly valuable in patients with prolonged PR interval and nonresponse to conventional CRT. AV delay optimization ensures proper atrioventricular synchrony, enhances left ventricular filling, and contributes to improved cardiac output. This case highlights the significance of individualized AV delay adjustment in conduction system pacing to maximize therapeutic outcomes. Optimization of AV delay is essential for maximizing the benefits of conduction system pacing, especially in HOT-CRT recipients. Attention to QRS morphology and duration during device implantation can help identify patients who will benefit most from individualized AV programming.