Abstract Body (Do not enter title and authors here): BACKGROUND: Left Ventricle Ejection Fraction (LVEF) has been a key predictor of long-term patient outcomes post-CRT. However, clinical scores may offer superior predictive value.

HYPOTHESIS: We hypothesized that clinical scores assessed at 6 months post-CRT would be better predictors of long-term survival.

AIMS: To compare the predictive accuracy of various clinical and LVEF for 2-year survival in patients who underwent CRT.

METHODS: This prospective cohort study included patients who underwent CRT at the Cleveland Clinic between May 2016 and June 2022. A set of clinical scores and LVEF were assessed at 6 months post-CRT. Our primary endpoint was Event-Free Survival (EFS) – defined by the absence of both significant cardiac interventions (LVAD implantation or heart transplant) and mortality. Scores included 6 Minute Walk Distance (6MWD; <1200ft), Gait Speed (GS, <0.7m/s), Timed Up and Go Test (TUG, >12s), SOF Frailty Index (SOF, ≥2) and the 5-level EuroQol-5 Dimension (EQ-5D-5L, >10). Each parameter was individually incorporated into a base Cox proportional hazards models while adjusting for baseline parameters. The predictive accuracy was compared using the concordance index (C-index).

RESULTS: Overall, 527 patients were recruited, of which 346 (66%) were men and 422 (81%) received a defibrillator. Median (IQR) values for age, QRS duration, LVEF, and NYHA class were 71 years (IQR: 62-78), 160ms (IQR: 146-176), 29% (IQR: 23-35), and 2 (IQR: 2-3), respectively. The response rate at 6 months post-CRT was 322 (67.9%), and the 2-year EFS rate was 400 (75.9%). Significant predictors of 2-year mortality included 6MWD (HR: 2.8542, p<0.001), GS (HR: 3.2145, p<0.001), TUG (HR: 2.5056, p<0.001), SOF (HR: 2.7371, p<0.001) and EQ-5D-5L (HR: 2.3324, p<0.001), and LVEF was not a significant predictor (HR: 0.9901, p=0.337). C-index values of the clinical scores – 6MWD (0.748), GS (0.746), TUG (0.741), SOF (0.753), EQ-5D-5L (0.730) – proved superior to LVEF (0.719).

CONCLUSION: Our findings show that clinical scores are better predictors of two-year EFS following CRT than LVEF. Thus, incorporating functional assessments into post-CRT evaluation may improve survival prediction and patient management.