Clinical Utility of QRS Duration Normalized to Left Ventricular Volume for Predicting Cardiac Resynchronization Therapy Efficacy in Patients with "Mid-Range" QRS Duration

Background Cardiac resynchronization therapy (CRT) is effective for patients with heart failure with a QRS duration (QRSd) > 150 milliseconds (ms). However, its beneficial effect appears to be limited for those with a "mid-range" QRSd (120–149 ms). Recent studies have demonstrated that modifying the QRSd to left ventricular end-diastolic volume (LVEDV), modified QRSd, improves the prediction of clinical outcomes of CRT. Objective To investigate the clinical impact of the modified QRSd in patients with a "mid-range" QRSd regarding the efficacy of CRT. Methods We conducted a retrospective, multi-center, observational study, with heart failure hospitalization (HFH) after CRT as the primary endpoint. Modified QRSd is defined as the QRSd divided by LVEDV, determined through the Teichholtz method of echocardiography. Results Among the 506 consecutive patients considered, 119 patients (mean age: 61±15 years, 80% male, QRSd: 135±9 ms) with a "mid-range" QRSd who underwent de-novo CRT device implantation were included for analysis. During a median follow-up period of 878 days (interquartile range: 381–1663 days), HFH occurred in 45 (37%) patients. Fine-Gray analysis revealed the modified QRSd was an independent predictor of HFH (hazard ratio [HR]: 0.97, 95% confidence interval [CI]: 0.96-0.99, p<0.01). Receiver operating characteristic curve analysis revealed a cutoff value of 0.65 ms/mL for the modified QRSd for predicting HFH. Those patients above exhibited a significantly lower incidence of HFH compared to those patients below (HR: 0.46, 95% CI: 0.25-0.86, p=0.01). Conclusion The modified QRSd can effectively predict the efficacy of CRT in patients with a "mid-range" QRSd.