Supplementary Material for: Baseline QRS area and reduction in QRS area are associated with lower mortality and risk of heart failure hospitalization after Cardiac Resynchronization Therapy

Introduction: Cardiac resynchronization therapy (CRT) is an established treatment for heart failure in selected patients. However, current guideline indications do not accurately predict individual prognosis with CRT, and up to 30% are non-responders. Previous studies have shown that QRS area reduction following CRT is associated with improved survival. This study evaluates the incremental value of using QRS area derived from digital ECG recordings, preoperatively and during CRT pacing.
Methods: Medical records of 445 patients receiving CRT implants at a large-volume tertiary care center in Sweden were retrospectively evaluated. Digital electrocardiograms (ECG) before and after CRT implantation were collected and ECG parameters were analyzed in relation to a primary composite endpoint of heart failure hospitalization or death from any cause.
Results: 147 patients (33%) reached the primary endpoint (93 deaths and 103 heart failure hospitalizations) over a median follow-up time of 2.7 years. A larger pre-implant QRS area (HR, 0.89; [0.85-0.93]; p=<0.0001; adjusted HR, 0.93; [0.88-0.98]; p=0.011) and larger QRS area reduction (HR, 0.92; [0.88-0.96]; p=<0.0001; adjusted HR, 0.95; [0.90-0.99]; p=0.042) post-implant correlated with a reduced risk of reaching the primary endpoint. This association was seen in patients with native left bundle branch block morphology, non-specific intraventricular conduction delay, or paced ECG morphology but not in patients with right bundle branch block.
Conclusion: Larger pre-implant QRS area and QRS area reduction was associated with better clinical outcome following CRT in this retrospective material. This knowledge could help optimize patient selection and postoperative management.