title: Clinical correlates and prognostic significance of six-minute walk test in patients with primary pulmonary hypertension. Comparison with cardiopulmonary exercise testing.
abstract: The six-minute walk test is a submaximal exercise test that can be performed even by a patient with heart failure not tolerating maximal exercise testing. To elucidate the clinical significance and prognostic value of the six-minute walk test in patients with primary pulmonary hypertension (PPH), we sought (1) to assess the relation between distance walked during the six-minute walk test and exercise capacity determined by maximal cardiopulmonary exercise testing, and (2) to investigate the prognostic value of the six-minute walk test in comparison with other noninvasive parameters. The six-minute walk test was performed in 43 patients with PPH, together with echocardiography, right heart catheterization, and measurement of plasma epinephrine and norepinephrine. Symptom-limited cardiopulmonary exercise testing was performed in a subsample of patients (n = 27). Distance walked in 6 min was significantly shorter in patients with PPH than in age- and sex-matched healthy subjects (297 +/- 188 versus 655 +/- 91 m, p < 0. 001). The distance significantly decreased in proportion to the severity of New York Heart Association functional class. The distance walked correlated modestly with baseline cardiac output (r = 0.48, p < 0.05) and total pulmonary resistance (r = -0.49, p < 0. 05), but not significantly with mean pulmonary arterial pressure. In contrast, the distance walked correlated strongly with peak V O(2) (r = 0.70, p < 0.001), oxygen pulse (r = 0.57, p < 0.01), and V E-VCO(2) slope (r = -0.66, p < 0.001) determined by cardiopulmonary exercise testing. During a mean follow-up period of 21 +/- 16 mo, 12 patients died of cardiopulmonary causes. Among noninvasive parameters including clinical, echocardiographic, and neurohumoral parameters, only the distance walked in 6 min was independently related to mortality in PPH by multivariate analysis. Patients walking < 332 m had a significantly lower survival rate than those walking farther, assessed by Kaplan-Meier survival curves (log-rank test, p < 0.01). These results suggest that the six-minute walk test, a submaximal exercise test, reflects exercise capacity determined by maximal cardiopulmonary exercise testing in patients with PPH, and it is the distance walked in 6 min that has a strong, independent association with mortality.
authors.affiliation: Division of Cardiology, Department of Medicine, National Cardiovascular Center, Osaka, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Miyamoto
authors.forename: N
authors.initials: N
authors.lastname: Nagaya
authors.forename: T
authors.initials: T
authors.lastname: Satoh
authors.forename: S
authors.initials: S
authors.lastname: Kyotani
authors.forename: F
authors.initials: F
authors.lastname: Sakamaki
authors.forename: M
authors.initials: M
authors.lastname: Fujita
authors.forename: N
authors.initials: N
authors.lastname: Nakanishi
authors.forename: K
authors.initials: K
authors.lastname: Miyatake
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005080:Exercise Test; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010807:Physical Endurance / Q000502:physiology; D011237:Predictive Value of Tests; D011379:Prognosis; D011669:Pulmonary Wedge Pressure / Q000502:physiology; D012016:Reference Values; D015996:Survival Rate; D016138:Walking / Q000502:physiology*