Delta QRS and outcomes post CRT in the Resynchronization-Defibrillation for Ambulatory Heart Failure Trial.

Background: For patients with left ventricular systolic dysfunction and prolonged QRS duration, cardiac resynchronization therapy (CRT) can improve cardiac electromechanical synchrony and prevent adverse clinical outcomes.

Objective: This study sought to investigate the role of delta QRS duration (ΔQRSd) in predicting clinical response to CRT.

Methods: The RAFT (Resynchronization-Defibrillation for Ambulatory Heart Failure Trial) study randomized 1798 patients to CRT with defibrillator or implantable cardioverter-defibrillator alone. Those who received CRT and had electrocardiograms available at baseline and after CRT implantation were included in this analysis. ΔQRSd was calculated as the absolute difference between QRS duration at baseline and with CRT pacing. The primary outcome was the composite of death and heart failure hospitalization.

Results: There were 813 patients included in this analysis. The median age was 67 years, and 125 patients (15.2%) were female. The median ΔQRSd was -2 ms (-20 to 18 ms), and 447 (55%) patients had a ΔQRSd ≤0 after implantation. ΔQRSd was an independent predictor of the composite outcome for patients with CRT (hazard ratio, 1.012; 95% confidence interval, 1.008-1.017). CRT recipients with ΔQRSd >0 had higher rates of the composite outcome than patients randomized to implantable cardioverter-defibrillator alone.

Conclusion: For patients receiving CRT for heart failure with left ventricular systolic dysfunction and QRS prolongation, ΔQRSd was an independent predictor of long-term mortality and heart failure hospitalization.