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Correlation of B-type natriuretic peptide level to 6-min walk test performance in patients with left ventricular
Stacey J Wieczorek1, David Hager, Mary-Beth Barry
1Department of Pathology and Laboratory Medicine, Hartford Hospital, 80 Seymour St, Hartford, CT 06102, USA.
Background:
B-type natriuretic peptide (BNP) is a neurohormone that can be measured in blood and is useful in patients with congestive heart failure (CHF). We compared whole blood BNP concentrations to distance walked during a 6-min walk test in patients with CHF.
Methods:
Forty-four patients with CHF underwent a 6-min walk test. The distance walked was compared to the BNP concentration on blood collected prior to the walk test. Patients were followed for 16 +/- 2.8 months after testing.
Results:
A significant correlation was observed between the BNP concentration and the distance walked (r = -0.47, p < 0.001). One patient without congestion died suddenly. Two patients died of progressive heart failure, and two other patients underwent cardiac transplantation. Each of the latter four patients had high BNP concentrations (median 1080 ng/l) and walked short distances (median 183 m). This study indicates that the BNP concentration in blood correlates inversely with the degree of physical capability of patients with heart failure.
Conclusions:
The BNP concentration could be used as an alternative to the 6-min walk test to assess the severity of heart failure. The assay for BNP is non-invasive, inexpensive, and results are available at the bedside or in a heart failure clinic.