Noninvasive Echocardiographic Left Ventricular Stroke Work Index Predicts Mortality in Cardiac Intensive Care Unit Patients

Abstract

Background: Reduced left ventricular stroke work index (LVSWI) has been associated with adverse outcomes in several populations of patients with chronic heart disease, but no prior studies have examined this metric in cardiac intensive care unit (CICU) patients. We sought to determine whether a low LVSWI, as measured noninvasively using transthoracic echocardiography, is associated with higher mortality in CICU patients. Methods: Using a database of unique Mayo Clinic CICU admissions from 2007 to 2018, we identified patients with LVSWI measured by transthoracic echocardiography within 1 day of CICU admission. Hospital mortality was analyzed using multivariable logistic regression, and 1-year mortality was analyzed using multivariable Cox proportional-hazards analysis, adjusted for left ventricular ejection fraction and known predictors of hospital mortality. Results: We included 4536 patients with a mean age of 68±14 years (36% women). Admission diagnoses (not mutually exclusive) included acute coronary syndrome in 62%, heart failure in 46%, and cardiogenic shock in 11%. The mean LVSWI was 38±14 g×min/m 2 , and in-hospital mortality occurred in 6% of patients. LVSWI had better discrimination for hospital mortality than left ventricular ejection fraction ( P <0.001 by De Long test). Higher LVSWI was associated with lower in-hospital mortality (adjusted odds ratio, 0.72 per 10 g×min/m 2 higher [95% CI, 0.61–0.84]; P <0.001) and lower 1-year mortality (adjusted hazard ratio, 0.812 per 1 g×min/m 2 higher [95% CI, 0.759–0.868]; P <0.001). Stepwise decreases in hospital and 1-year mortality were observed with higher LVSWI. Conclusions: Low LVSWI, reflecting poor left ventricular systolic and diastolic performance, is associated with increased short-term and long-term mortality among CICU patients. This emphasizes the importance of Doppler transthoracic echocardiography as a predictor of outcomes among critically ill patients. Further study is required to determine whether early interventions to optimize LVSWI can improve outcomes in the CICU setting.