Conduction system pacing as a rescue strategy for unsuccessful cardiac resynchronisation therapy implantation

Failure to achieve effective cardiac resynchronisation therapy (CRT) remains a clinically significant challenge, often driven by anatomical constraints or suboptimal left ventricular lead performance. Conduction system pacing (CSP), incorporating His bundle pacing and left bundle branch area pacing, has emerged as a physiological alternative; however, data focussing specifically on its role as a rescue strategy following unsuccessful CRT implantation, rather than biological non-response, remain limited.

To evaluate the feasibility, safety, and short- to mid-term clinical and echocardiographic outcomes of CSP in patients with unsuccessful conventional CRT implantation.

In this single-centre retrospective study, consecutive patients undergoing attempted CSP after unsuccessful CRT between January 2020 and May 2025 were analysed. Unsuccessful CRT was defined as inability to deliver effective biventricular pacing due to anatomical or technical limitations, excluding patients with true non-response despite successful implantation. Procedural success, electrical resynchronisation, changes in left ventricular ejection fraction (LVEF), and clinical outcomes were assessed.

Thirty-two patients (mean age 69 years, mean LVEF 27.8%) were included. CSP was successfully achieved in 91% of cases, predominantly using left bundle branch area pacing. Baseline QRS duration (165 ± 38 ms) significantly narrowed to 122 ± 19.8 ms following CSP. This was accompanied by marked improvement in LVEF (from 27.0 ± 8.6% to 47.7 ± 11.2%, p < 0.001). Procedural complications were infrequent, with one pneumothorax and no device-related infections. Over a mean follow-up of 641 ± 522 days, heart failure hospitalisation occurred in 7%, and three deaths were observed, non-attributable to device-related causes.

CSP is a highly feasible and safe rescue strategy in patients with unsuccessful CRT implantation, achieving substantial electrical resynchronisation and meaningful recovery of left ventricular function. These findings support CSP as a compelling alternative in anatomically or technically challenging CRT cases where conventional resynchronisation delivery is not achievable.