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.

引言：心脏再同步治疗（Cardiac resynchronization therapy, CRT）是经临床证实用于筛选合适患者治疗心力衰竭的有效手段。然而，当前的指南适应证无法准确预测患者接受CRT后的个体预后，仍有高达30%的患者无应答。既往研究表明，CRT术后QRS波面积（QRS area）缩小与生存率改善相关。本研究旨在评估从数字化心电图（digital electrocardiogram, ECG）记录中提取的QRS波面积，在术前及CRT起搏期间应用的增量价值。
方法：本研究回顾性评估了瑞典一家大型三级医疗中心内445例接受CRT植入术患者的病历资料。收集了CRT植入前后的数字化心电图资料，并分析心电图参数与主要复合终点（心力衰竭住院或任何原因导致的死亡）的相关性。
结果：在中位随访2.7年期间，共有147例患者（占比33%）达到了主要复合终点，其中93例死亡，103例因心力衰竭住院。术前更大的QRS波面积[风险比（hazard ratio, HR）0.89，95%置信区间0.85~0.93；p<0.0001；校正后HR 0.93，95%置信区间0.88~0.98；p=0.011]以及术后更大的QRS波面积缩小幅度[HR 0.92，95%置信区间0.88~0.96；p<0.0001；校正后HR 0.95，95%置信区间0.90~0.99；p=0.042]均与达到主要复合终点的风险降低相关。该相关性在窦性左束支传导阻滞形态、非特异性心室内传导延迟或起搏心电图形态的患者中均存在，但在右束支传导阻滞患者中未观察到。
结论：在本回顾性研究资料中，术前更大的QRS波面积以及术后QRS波面积缩小幅度与CRT术后更佳的临床结局相关。该研究结果有助于优化患者筛选及术后管理方案。