QRS fusion complex analysis using wave interference to predict reverse remodeling during cardiac resynchronization therapy

Abstract

Biventricular (BV) electrical wavefront fusion can induce improvement in left ventricular (LV) size and function during cardiac resynchronization therapy (CRT). Changes in BV wave propagation sequence and duration register in the QRS complex on the standard electrocardiogram. We developed a wave interference method for the characterization of BV fusion to predict LV reverse remodeling. To develop a simple electrocardiographic method for predicting reverse remodeling during CRT. QRS complexes during left bundle branch block (LBBB) and CRT were analyzed in 375 patients with ejection fraction ≤35% and New York Heart Association class III-IV (Leiden study: n = 226) as well as in patients with ejection fraction ≤40% and New York Heart Association class I-II (REVERSE trial: n = 149) for predictors of ≥10% reduction in left ventricular end-systolic volume at 6 months. CRT-induced changes in ventricular activation (QRS fusion contour), electrical asynchrony (QRS difference = BV-paced QRS - LBBB QRS, in milliseconds), and LBBB substrate (LV activation time and QRS score for LV scar) were quantified. Multivariable predictors of reverse remodeling were as follows: (1) either of 2 BV fusion patterns: QRS normalization in leads V1 and V2 (n = 66 [18%]; odds ratio [OR] 3.71; 95% confidence interval [CI] 1.26-10.94) or a new or an increased R wave in leads V1-V2 (n = 267 [71%]; OR 1.55; 95% CI 0.65-3.65); (2) QRS difference ≤ -25 ms (OR 2.35; 95% CI 1.12-4.91); and (3) good substrate (low to moderate QRS score and LV activation time ≥110 ms; OR 2.94; 95% CI 1.68-5.14). Remodeling rates were 40% for poor substrate and persistent LBBB QRS complex (absent BV fusion; QRS type 3: n = 42 [11%]) and 97% for the best BV QRS fusion pattern and greater reduction in electrical asynchrony (larger QRS difference). Easily determined QRS complex attributes before and after CRT predict LV reverse remodeling.