Validation Cohort

The target validation sample size is 343 patients, based on 120 required non-response events and an assumed 35% non-response rate. CRT response will be assessed at 6 months using outpatient and hospitalisation records. Responders are defined as patients meeting at least one criterion: improved NYHA class, increased LVEF, or reduced left ventricular end-systolic volume. The validation cohort will include patients undergoing CRT implantation at the First Affiliated Hospital of Xinjiang Medical University from January 2018 to October 2025. Eligible validation procedures include CRT pacemakers, CRT defibrillators, and ICD-to-CRT upgrades. Validation cohort inclusion requires optimized guideline-directed medical therapy before CRT, NYHA class II-IV, QRS duration of at least 120 ms, LVEF of 35% or below, and adult age.