Cardiopulmonary exercise performance in physiologic versus conventional pacing

Introduction Right ventricular pacing (RVP) can induce electrical and mechanical dyssynchrony, potentially impairing left ventricular performance and exercise tolerance, especially in patients who experience > 20% of RVP burden. Left bundle branch area pacing (LBBAP) provides a more physiologic alternative by engaging the native His–Purkinje system and preventing pacing induced cardiomyopathy (PICM). However, the impact of RVP on functional capacity among patients who do not develop PICM remains poorly characterized, and no study to date has compared LBBAP and RVP during exercise. Purpose To compare exercise capacity and cardiopulmonary response in patients who underwent LBBAP versus RVP implantation and who did not develop PICM, in a real-world cohort. Methods A prospective, non-randomized pilot study was conducted including patients undergoing CPET after LBBAP (n = 7) or RVP (n = 7) implantation. Baseline clinical, electrocardiographic, echocardiographic, and procedural characteristics were collected. CPET was performed on a cycle ergometer using a ram protocol. A short programmed atrioventricular interval (120 ms) ensured 100% pacing in each mode during exercise. Groups were compared using appropriate statistical tests. Results Baseline demographic, clinical, and echocardiographic characteristics were similar between groups. QRS duration was narrower in the LBBAP group (120ms vs 155ms) and all patients achieved maximal tests (RER > 1.10). Regarding functional capacity measures, although between-group differences did not reach statistical significance, LBBAP showed a consistent trend toward superior performance, including higher achieved workload (127 ± 38 W vs 99 ± 61 W; p = 0.73) and slightly higher VO₂ peak (18.5 ± 2.3 vs 17.0 ± 6.8 mL/kg/min; p = 0.47). Ventilatory efficiency (VE/VCO₂ slope), RER, and chronotropic response were comparable. Conclusions In this pilot cohort, LBBAP demonstrated a consistent trend toward improved exercise performance compared with RVP, despite the absence of statistical significance—likely influenced by limited sample size. These findings support the physiologic rationale of LBBAP and suggest that it may mitigate pacing-induced impairment during exercise, highlighting the importance of assessing functional capacity beyond resting left ventricular ejection fraction. Larger prospective studies are needed to validate these preliminary observations.