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 QRS duration (QRSd) >= 150 ms. However, its beneficial effect seems to be limited for those with "mid-range" QRSd (120-149 ms). Recent studies have demonstrated that modifying QRSd to left ventricular end-diastolic volume (LVEDV)-modified QRSd-improves the prediction of clinical outcomes of CRT. OBJECTIVE The purpose of this study was to investigate the clinical impact of the modified QRSd on the efficacy of CRT in patients with "mid-range" QRSd. METHODS We conducted a retrospective, multicenter, observational study, with heart failure hospitalization (HFH) after CRT as the primary endpoint. Modified QRSd is defined as QRSd divided by LVEDV, determined through the Teichholtz method of echocardiography. RESULTS Among the 506 consecutive patients considered, 119 (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 median follow-up of 878 days [interquartile range 381-1663 days], HFH occurred in 45 patients (37%). Fine-Gray analysis revealed modified QRSd was an independent predictor of HFH (hazard ratio [HR] 0.97; 95% confidence interval [CI] 0.96-0.99; P <.01). Receiver operating characteristic curve analysis revealed a cutoff value of 0.65 ms/mL for the modified QRSd in predicting HFH. Patients above the threshold exhibited a significantly lower incidence of HFH than patients below the threshold (HR 0.46; 95% CI 0.25-0.86; P = .01). CONCLUSION Modified QRSd can effectively predict the efficacy of CRT in patients with a "mid-range" QRSd.