Published Online
on September 28, 2009

A more recent version of this article appeared on November 1, 2009

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Original Article

6 Minute Walk Test and Cardiopulmonary Exercise Testing in Chronic Heart Failure: a Comparative Analysis on Clinical and Prognostic Insights

Marco Guazzi^1,4; Kenneth Dickstein²; Marco Vicenzi¹ and Arena Ross³

¹ University of Milano, Milano, Italy;
² University of Bergen, Stavanger, Norway;
³ Virginia Commonwealth University, Richmond, VA

^* Corresponding author; email: marco.guazzi{at}unimi.it

Background—6 min walk test (6MWT) and cardiopulmonary exercise testing (CPET) are the two testing modalities most broadly used for assessing functional limitation in heart failure (HF) patients. A comprehensive comparison on clinical and prognostic validity of the two techniques has not been performed and is the aim of the present investigation.

Methods and Results—253 patients diagnosed with systolic (n=211) or diastolic (n= 42) HF (age: 61.9±10.1 NYHA class: 2.2±0.78) underwent a 6MWT and a symptom-limited CPET evaluation and were prospectively followed-up. During the four-year tracking period there were 43 cardiac-related deaths with an annual cardiac mortality rate of 8.7%. 6MWT distance correlated with CPET-derived variables (i.e., 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 oscillatory breathing pattern (P<0.01). However, no significant differences were observed in distance covered between survivors and non-survivors (353.2±95.8 vs 338.5±76.4 meters; P=NS). At univariate and multivariate Cox proportional analysis the association of the 6MWT distance with survival was not significant either as continuous or dicotomized variable ( 300 meters>). Conversely, CPET-derived variables emerged as prognostic with the strongest association found for EOB (systolic HF) and VE/VCO₂ slope (entire HF population and patients with a 6MWT 300 meters).

Conclusions—6MWT is confirmed to be a simple and reliable first-line test for quantification of exercise intolerance in HF patients. 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