16-72: Magnitude of QRS reduction after biventricular pacing identifies responders to Cardiac Resynchronization Therapy

Purpose of the study: Several studies have investigated the association between native QRS duration (QRSd) or QRS narrowing and response to biventricular pacing. However, their results have been conflicting. The aim of our study was to determine the association between the relative change in QRSd (QI) and clinical outcome and prognosis in patients who undergo CRT implantation.

Method used: We included 311 patients in whom a CRT device was implanted in accordance with current guidelines for CRT. On implantation, the native QRS, the QRSd and the QI during CRT were measured.

Summary of results: After 6 months, 220 (71%) patients showed a 10% reduction in LVESV. The median [25th–75th] QI was 14.3% [7.2–21.4] and was significantly related to reverse remodeling (r = +0.22; 95%CI:0.11-0.32, p = 0.0001). The cut-off value of QI that best predicted LV reverse remodeling after 6 months of CRT was 12.5% (sensitivity = 63.6%, specificity = 57.1%, area under the curve = 0.633, p = 0.0002). The time to the event was significantly longer among patients with QI > 12.5% (log-rank test, p = 0.0155), with a hazard ratio (HR) of 0.3 [95%CI:0.11-0.78]. In the multivariate regression model adjusted for baseline parameters, a 10% increment in QI (HR = 0.61[0.44–0.83], p = 0.002) remained significantly associated with CRT response.

Conclusion: Patients with a larger decrease in QRSd after CRT initiation showed greater echocardiographic reverse remodeling and better survival from death or cardiovascular hospitalization. QI is an easy-to-measure variable that could be used to predict CRT response at the time of pacing site selection or pacing configuration programming.