Predictors of Functional Capacity in Chronic Heart Failure: Echocardiography Versus Six-Minute Walk Test

Abstract

Background: Six-minute walk test (6MWT) constitutes a suitable alternative for Cardio-pulmonary exercise testing to assess functional capacity in patients with heart failure (HF). Echocardiography has always been considered as the most useful easy test for evaluation of these patients. Purpose: to determine the echocardiographic predictors of six-minute walk distance (6MWD) in patients with chronic systolic heart failure as an objective assessment of functional capacity. Methods: This study included 40 patients with HF, ejection fraction (EF) <40% presenting with grade I to II NYHA (New York Heart Association) classification. All performed simultaneous transthoracic echocardiographic study and 6MWT. Results: The mean 6MWD was 340.25 ±88.64 meters. 26 patients (65%) walked more than 300 meters (group I) while 35% (14 patients) did not (group II). Right ventricular systolic pressure (RVSP) and E/e' were significantly higher in (group II), (p=0.04 and 0.05 respectively). There were significant negative correlations between 6MWD and each of LVESV (r=-0.34, p=0.03), E/e' (r=-0.36, p=0.02) and, RVSP (r=-0.34, p=0.03). Linear regression analysis showed RVSP as the only independent predictor of 6MWD, thus an independent predictor of functional capacity in HF patients. Furthermore this study suggested a predictive model of estimation of 6MWD from a given value of RVSP: 6MWD=a + (b×RVSP); (a and b are constants) with a standard error of±42 m. Conclusion: RVSP, LVESV and E/e' were correlated with 6MWD in chronic HF patients. Among different echocardiographic parameters, RVSP can be used as an independent predictor of functional capacity in HF patients. Further studies are still needed to ascertain the sensitivity and specificity of this model in prediction of functional capacity in HF patients in everyday practice.