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.


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/Vco(2) 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 (< or =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< or =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.
Guazzi
Marco
M
Cardiopulmonary Unit, University of Milano, Italy. marco.guazzi@unimi.it
Dickstein
Kenneth
K
Vicenzi
Marco
M
Arena
Ross
R
D000368:Aged; D002319:Cardiovascular System / Q000503:physiopathology*; D002908:Chronic Disease; D004562:Electrocardiography; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D005500:Follow-Up Studies; D054144:Heart Failure, Diastolic / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology / Q000628:therapy; D054143:Heart Failure, Systolic / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology / Q000628:therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D011446:Prospective Studies; D015203:Reproducibility of Results; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics; D012137:Respiratory System / Q000503:physiopathology*; D018570:Risk Assessment; D012720:Severity of Illness Index; D013997:Time Factors; D016896:Treatment Outcome; D016277:Ventricular Function, Left; D016138:Walking