Six-Minute Walk Test and Cardiopulmonary Exercise Testing in Patients With Chronic Heart Failure A Comparative Analysis on Clinical and Prognostic Insights

Background-The six-minute walk test (6MWT) and cardiopulmonary exercise testing (CPET) are the 2 testing modalities most broadly used for assessing functional limitation in patients with heart failure (HF). A comprehensive comparison on clinical and prognostic validity of the 2 techniques has not been performed and is the aim of the present investigation. Methods and Results-Two hundred fifty-three patients diagnosed with systolic (n = 211) or diastolic (n = 42) HF (age: 61.9 +/- 10.1 years; New York Heart Association Class: 2.2 +/- 0.78) underwent a 6MWT and a symptom-limited CPET evaluation and were prospectively followed up. During the 4-year tracking period, there were 43 cardiac-related deaths with an annual cardiac mortality rate of 8.7%. The 6MWT distance correlated with CPET-derived variables (ie, peak VO(2), VO(2) at anaerobic threshold, and VE/VCO(2) slope) and was significantly reduced in proportion with lower peak VO(2) and higher VE/VCO2 slope classes and presence of an exercise oscillatory breathing (EOB) pattern (P < 0.01). However, no significant differences were observed in distance covered between survivors and nonsurvivors (353.2 +/- 95.8 m versus 338.5 +/- 76.4 m; P = NS). At univariate and multivariate Cox proportional analyses, the association of the 6MWT distance with survival was not significant either as a continuous or dicotomized variable (<= 300 m). Conversely, CPET-derived variables emerged as prognostic with the strongest association found for EOB (systolic HF) and VE/VCO(2) slope (entire population with HF and patients with a 6MWT <= 300 m). Conclusions-The 6MWT is confirmed to be a simple and reliable first-line test for quantification of exercise intolerance in patients with HF. However, there is no supportive evidence for its use as a prognostic marker in alternative to or in conjunction with CPET-derived variables. (Circ Heart Fail. 2009; 2: 549-555.)