Clinical Significance of Global Wasted Work in Patients with Heart Failure Receiving Cardiac Resynchronization Therapy

Abstract

The relationship between myocardial work assessment using pressure-strain loops by echocardiography before cardiac resynchronization therapy (CRT) and response to CRT has been recently revealed. Among myocardial work parameters, the impact of left ventricular myocardial global wasted work (GWW) on response to CRT and outcome following CRT has been seldom studied. Hence, the authors evaluated the relationship between preprocedural GWW and outcome in a large prospective cohort of patients with heart failure (HF) and reduced ejection fraction receiving CRT. The study included 249 patients with HF. Myocardial work indices including GWW were calculated using speckle-tracking strain two-dimensional echocardiography using pressure-strain loops. End points of the study were (1) response to CRT, defined as left ventricular reverse remodeling and/or absence of hospitalization for HF, and (2) all-cause death during follow-up. Median follow-up duration was 48months (interquartile range, 43-54months). Median preoperative GWW was 281mm Hg% (interquartile range, 184-388mm Hg%). Preoperative GWW was associated with CRT response (area under the curve, 0.74; P<.0001), and a 200mm Hg% threshold discriminated CRT nonresponders from responders with 85% specificity and 50% sensitivity, even after adjustment for known predictors of CRT response (adjusted odds ratio, 4.03; 95% CI, 1.91-8.68; P<.001). After adjustment for established predictors of outcome in patients with HF with reduced ejection fraction receiving CRT, GWW < 200mm Hg% remained associated with a relative increased risk for all-cause death compared with GWW ≥ 200mm Hg% (adjusted hazard ratio, 2.0; 95% CI, 1.1-3.9; P=.0245). Adding GWW to a baseline model including known predictors of outcome in CRT resulted in an improvement of this model (χ2 to improve 4.85, P=.028). The relationship between GWW and CRT response and outcome was stronger in terms of size effect and statistical significance than for other myocardial work indices. Low preoperative GWW (<200mm Hg%) is associated with absence of CRT response in CRT candidates and with a relative increased risk for all-cause death. GWW appears to be a promising parameter to improve selection for CRT of patients with HF with reduced ejection fraction.