Reverse electrical remodelling after cardiac resynchronization therapy in a patient undergoing left bundle branch area pacing: a case report

Background: Left bundle branch area pacing (LBBAP) has been introduced as an alternative to biventricular pacing in cardiac resynchronization therapy (CRT). Several studies describe echocardiographic reverse remodelling after LBBAP. Reverse electrical remodelling after LBBAP has not yet been described. Case summary: A 77-year-old female with non-ischaemic heart failure with reduced ejection fraction [left ventricular ejection fraction (LVEF) 30-35%], left bundle branch block (QRS duration 164 ms), and symptomatic atrial fibrillation irresponsive to pharmacological therapy was evaluated for CRT with LBBAP and atrioventricular node ablation. Successful LBBAP implantation resulted in confirmed left bundle branch capture. Immediately after implantation, paced QRS duration was 194 ms with a long stimulus-V6RWPT (time to peak R wave in V6) of 93 ms, suggesting distal conduction system disease. Patient showed an echocardiographic improvement (LVEF 35-50%) and improvement in symptoms (NYHA class III to NYHA class II) at 1-year follow-up. Moreover, an improvement in conduction delays was found present. Paced QRS duration improved to 159 ms and stimulus-V6RWPT improved to 78 ms. This improvement might be due to reverse electrical remodelling. Discussion: This case demonstrates that LBBAP can induce reverse electrical remodelling, even in the presence of distal conduction system disease. With the current availability of different pacing strategies in CRT (i.e. biventricular CRT, LBBAP, and left bundle branch-optimized CRT), more research on patient selection and pacing strategy selection is needed.