Published online before print September 28, 2009, doi: 10.1161/CIRCHEARTFAILURE.109.881326
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Original Articles |
Six-Minute Walk Test and Cardiopulmonary Exercise Testing in Patients With Chronic Heart Failure
A Comparative Analysis on Clinical and Prognostic Insights
From the Cardiopulmonary Unit (M.G., M.V.), University of Milano, Italy; Stavanger University Hospital (K.D.), Stavanger, Rogaland, Norway; Institute of Internal Medicine (K.D.), University of Bergen, Bergen, Norway; Virginia Commonwealth University (R.A.), Virginia, Richmond, Va.
Correspondence to Marco Guazzi, MD, PhD, FACC, Cardiopulmonary Unit, University of Milano, San Paolo Hospital, Via A. di Rudinì, 8, 20142 Milano, Italy. E-mail marco.guazzi{at}unimi.it
Received May 20, 2009; accepted September 8, 2009.
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 VO2, VO2 at anaerobic threshold, and VE/VCO2 slope) and was significantly reduced in proportion with lower peak VO2 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/VCO2 slope (entire population with HF and patients with a 6MWT300 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.
Key Words: exercise • heart failure • prognosis • ventilation