Cardiac Resynchronization Therapy Using a Conduction System Pacing Defibrillation Lead in Patients Meeting CRT-D Indications

BACKGROUND Conduction system pacing (CSP) via left bundle branch area pacing (LBBAP) is a physiologic alternative to conventional biventricular (BiV) pacing for cardiac resynchronization therapy (CRT), but prospective data using purpose-built implantable cardioverter-defibrillator (ICD) leads are limited. OBJECTIVES The purpose of this study was to evaluate procedural success, defibrillation efficacy, safety, and 6-month clinical outcomes of left bundle branch-optimized cardiac resynchronization therapy (LOT-CRT) delivered with a purpose-built CSP ICD lead and compare outcomes to conventional BiV-CRT. METHODS A total of 52 CRT defibrillator patients (age 66 ± 10 years, 31.4% female, left ventricular ejection fraction (LVEF) 29.5 ± 6.7%, left bundle branch block [LBBB] 66.7%, QRSd 164.6 ± 25.3 milliseconds, 29.4% ischemic) in the ASCEND CSP IDE (A Stylet-Driven ICD Lead Intended for Conduction System Pacing IDE Study) study underwent attempted implantation of a CSP ICD lead and a coronary sinus lead (LOT-CRT). Implant success, safety and efficacy outcomes, electrocardiographic characteristics, echocardiographic remodeling, heart failure status, patient-reported quality of life, and CRT response were assessed through 6 months. Outcomes were compared with a propensity-matched conventional CRT cohort (BiV-CRT). RESULTS Implantation succeeded in 98.1% (51 of 52), with LBBAP capture achieved in all (51 of 51). Freedom from CSP lead-related serious adverse device effects through 6 months was 98.1% (95% CI: 87.1%-99.7%). Defibrillation was successful in all tested patients (100%). Compared with baseline, QRS narrowed by 30.4 ms and LVEF increased by 10.4 points (both P < 0.0001), with a CRT response (≥5%) in 71.1% and super-response (≥14.5%) in 34.2%. Compared with matched BiV-CRT patients from the MORE-CRT MPP (MORE response on Cardiac Resynchronization Therapy with MultiPoint Pacing) study, lead-related events were similar (2.0% vs 2.5%; P = 1.0), LVEF increase was greater (10.4 points vs 4.6 points; P = 0.0005) with more responders (≥5%) and super-responders (≥14.5%) (71.1% vs 48.5%; P = 0.0107 and 34.2% vs 7.8%; P < 0.0001, respectively), and more patients improved by clinical composite score (76.5% vs 52.0%; P = 0.0016). Significant improvements were seen with LOT-CRT in both LBBB and non-LBBB patients. CONCLUSIONS LOT-CRT with a dedicated CSP ICD lead achieved high implant success, preserved defibrillation efficacy, and had favorable safety, with greater left ventricular systolic function and clinical improvement than matched conventional CRT, supporting CSP-based CRT defibrillator therapy.