Six-minute walking test predicts long-term cardiac death in patients who received cardiac resynchronization therapy

Abstract

Cardiac resynchronization therapy (CRT) has been proven to be effective in patients suffering from chronic heart failure (CHF) associated with electrical dyssynchrony. However, long-term predictors of mortality in that subset have not been extensively investigated. The aim of this study was to establish baseline long-term predictors of cardiovascular mortality in CHF patients treated with CRT. A total of 188 consecutive patients with moderate to severe CHF who had undergone a successful CRT implant were evaluated. Baseline measurements included clinical history, a 6-min walking test (6MWT), and echocardiographic parameters. Patients with cardiac or non-cardiac diseases limiting their ability to perform a 6MWT were excluded, with the final count totalling 155 patients [82% men, mean age 69 +/- 8 years, New York Heart Association (NYHA) functional class: II 22%, III 73.5%, IV 4.5%]. A total of 24 patients (15.5%) died of cardiovascular causes and one patient underwent heart transplantation during a mean follow-up of 24.4 +/- 18.1 months. Univariate analysis showed that NYHA class, distance walked in the 6MWT, left atrial diameter, digoxine and left ventricle (LV) ejection fraction were all significantly related to rates of mortality. Multivariate Cox regression after adjustment for the presence of a defibrillator showed that the LV ejection fraction [HR 0.91 (95% CI: 0.84-0.98) P = 0.008] and 6MWT distance <225 m [HR 5.6 (95% CI: 1.2-25.3) P = 0.026] were independent predictors of cardiovascular mortality. Baseline functional capacity, measured by the 6MWT distance, and LV ejection fraction are independent predictors of mortality in moderate to severe CHF patients, despite CRT. A 6MWT distance walked of <225 m identifies patients at high risk of cardiovascular death at mid-long term.