Background: Conduction system pacing (CSP) has emerged as an alternative to biventricular pacing (BiVp), but its implantation requires a specific learning curve. Early experience was dominated by His bundle pacing (HBP) with lumenless leads (LLL), whereas the subsequent adoption of left bundle branch area pacing (LBBAP) and the increasing procedural standardization led to a simplification of the technique and greater uniformity in its execution. This study evaluated the learning curve for CSP by analyzing the first consecutive implants of two electrophysiologists (operator 1: OP1 and operator 2: OP2). Methods: The first 55 CSP procedures performed by each operator (n = 110) were retrospectively analyzed. Implantation and fluoroscopy times were assessed in blocks of five cases. Univariate and multivariable linear regression were used to identify independent predictors of procedural complexity. Results: A total of 110 CSP implants (55 per electrophysiologist) were analyzed. Implantation time progressively decreased with experience, reaching a stable plateau after ~45 cases per operator, when inter-operator curves completely overlapped and differences were no longer significant. Fluoroscopy time stabilized earlier and showed no consistent differences between electrophysiologists. In the univariate analysis, longer procedural times were associated with larger left ventricular end-diastolic diameters (LVEDD: r: 0.43; p < 0.001), LLL (r: 0.25; p < 0.01) and earlier implant numbers (r: 0.36; p < 0.001). In the multivariable models, only LVEDD and implant number (IN) remained independent predictors of procedure duration (LVEDD: β: 2.04, p: 0.04; and IN: β: 3.26, p < 0.04). Conclusions: CSP implantation follows a distinct learning curve, with procedure duration stabilizing after approximately 45 cases per operator. Procedural complexity is mainly determined by patient factors (LVEDD) and operator-related factors, whereas differences between LLL and SL reflect historical experience rather than intrinsic technical characteristics.

Background: Biventricular pacing (BIV) is gold standard for cardiac resynchronization therapy (CRT). Thirty % of patients result non responder to CRT. Conduction system pacing (CSP) represents a feasible alternative. Interventricular conduction delay (IVCD), as electrical desynchrony marker, is a CRT response predictor. The aim of the study was to assess CRT responder’s incidence when it has been achieved choosing best approach between BIV and CSP according to intraoperative IVCD measurement in patients with HFrEF and LBBB. Methods: Ninety-eight patients have been 1:1 randomized in a standard BIV group (control group, CG) and a group in which CRT approach has been chosen based on IVCD evaluation (study group, SG), as reported in Figure 1. If the right ventricular sensed electrogram (RVs)-left ventricular sensed electrogram (LVs) interval was ≥100 ms, the left ventricular lead was left in its original position; otherwise, the lead was removed and CSP was performed instead, as reported in Figure 2. Clinical, EKG and echocardiographic features have been assessed pre- and 6 months post-implant. Echocardiographic and clinical response have been evaluated. Results: Twenty-four % of patients in the SG underwent CSP, according to the operative algorithm adopted. CRT responders’ incidence was significantly higher in the SG (echocardiographic criterion: SG 93,9% vs CG 69,8%; clinical criterion SG 87,9% vs CG 62,8%). Patients in SG presented a significant improvement in EF between pre- and post-implant and a significantly reduced End Diastolic Volumes and End Systolic Volumes vs CG. Univariate and multivariate regression analysis showed that enrolment in SG was the only factor consistently associated to CRT response. Conclusion: Intraoperative evaluation of IVCD may guide the choice of the best resynchronization approach between BIV and CSP, allowing to achieve a significant improvement of CRT responders’ rate.Figure 1Figure 2