Paced Left Ventricular QRS Width and ECG Parameters Predict Outcomes After Cardiac Resynchronization Therapy

BACKGROUND: For patients with symptomatic New York Heart Association class III or IV, ejection fraction ≤ 35%, and QRS ≥ 130 ms, cardiac resynchronization therapy (CRT) has become an established treatment option. However, use of these implant criteria fails to result in clinical or echocardiographic improvement in 30% to 45% of CRT patients. METHODS AND RESULTS: The Predictors of Response to CRT (PROSPECT)-ECG is a substudy of the prospective observational PROSPECT trial. ECGs collected before, during, and after CRT implantation were analyzed. Primary outcomes were improvement in clinical composite score (CCS) and reduction of left ventricular end systolic volume (LVESV) of >15% after 6 months. Age, sex, cause of cardiomyopathy, myocardial infarction location, right ventricular function, mitral regurgitation, preimplantation QRS width, preimplantation PR interval, preimplantation right ventricular-paced QRS width, preimplantation axis categories, LV-paced QRS width, postimplantation axis categories, difference between biventricular (Bi-V) pacing and preimplantation QRS width, and QRS bundle branch morphological features were analyzed univariably in logistic regression models to predict outcomes. All significant predictors (α=0.1), age, and sex were used for multivariable analyses. Cardiomyopathy cause interaction and subanalyses were also performed. In multivariable analyses, only QRS left bundle branch morphological features predicted both CCS (odds ratio OR=2.46, P=0.02) and LVESV (OR=2.89, P=0.048) response. The difference between Bi-V and preimplantation QRS width predicted CCS improvement (OR=0.89, P=0.04). LV-paced QRS width predicted LVESV reduction (OR=0.86, P=0.01). Specifically, an LV-paced QRS width of ≤ 200 ms was predictive of nonischemic LVESV reduction (OR=5.12, P=0.01). CONCLUSIONS: Baseline left bundle branch QRS morphological features, LV-paced QRS width, and the difference between Bi-V and preimplantation QRS width can predict positive outcomes after CRT and may represent a novel intraprocedural method to optimize coronary sinus lead placement. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00253357.