Refining cardiac resynchronization therapy selection in borderline QRS duration patients

Cardiac resynchronization therapy (CRT) improves outcomes in heart failure patients with left bundle branch block (LBBB) and QRS of ≥150 ms, but benefits with borderline QRS (120-149 ms) remain uncertain. Electrical (ED) and mechanical dyssynchrony (MD) may refine patient selection, although reliable predictors are lacking.

To examine clinical predictors of dyssynchrony in patients with borderline QRS duration (QRSd) undergoing CRT.

We retrospectively studied 336 CRT recipients (2006-2015). Vectorcardiograms quantified QRS area (QRSa), with ED defined as QRSa of ≥95 μVs. MD was assessed via speckle-tracking echocardiography. Logistic regression identified predictors of dyssynchrony. QRSa indexed to left ventricular end-diastolic volume (QRSa/LVEDV) was evaluated in logistic and Cox models, stratified by a QRSd of 150 ms threshold.

ED and MD were present in 53.0% and 74.4% of patients. Shorter height was independently associated with ED, while female sex predicted MD. Among patients with QRSd of <150 ms, ED and MD were less prevalent, and height was the sole independent predictor of ED. Over a median follow-up of 28.3 months, 241 patients (71.7%) experienced a composite endpoint, with similar event rates between QRS subgroups. QRSa/LVEDV was the strongest predictor of MD (odds ratio: 26.83; P = .0004) and reduced risk of adverse outcomes (hazard ratio: 0.172; P = .0006) in the <150-ms subgroup, outperforming QRSd and sex. When MD was added, the QRSa/LVEDV association attenuated (hazard ratio: 0.35; P = .07).

Among LBBB patients with borderline QRSd, QRSa/LVEDV was more strongly associated with MD and outcomes than QRSd or other factors, supporting its potential role in refining patient selection.