Changes in oxygen uptake-work rate relationship as a compensatory mechanism in patients with heart failure

• Published in: Japanese circulation journal Vol. 56; no. 5; pp. 504 - 508
• Main Authors: Itoh, H, Nakamura, M, Ikeda, C, Yanagisawa, E, Hatogai, F, Iwadare, M, Taniguchi, K
• Format: Journal Article
• Language: English
• Published: Japan 1992
• Subjects: Adolescent; Adult; Aged; cardiac muscle; Cardiac Output; characterization; Exercise Test; Female; heart diseases; Heart Failure - metabolism; Heart Failure - physiopathology; Humans; Kinetics; Male; man; Middle Aged; Norepinephrine - blood; oxygen; Oxygen - metabolism; Physical Exertion; Regression Analysis; uptake
• ISSN: 0047-1828; 1347-4839
• DOI: 10.1253/jcj.56.504

To assess the compensatory change in oxygen uptake (VO2) kinetics during exercise in patients with heart failure, we performed cardiopulmonary exercise testing using a cycle ergometer in 29 cardiac patients and 18 normal subjects. The work rate increased linearly (1w/6sec) after a 4 min, 20w warm-up. The ratio of increase in VO2 to increase in work rate (delta VO2/delta WR) was determined by linear regression of VO2 plots. Cardiac output by dye dilution method and plasma norepinephrine concentration (NE) were measured at rest and 20w warm-up. VO2 at rest and at 20w warm-up and delta VO2/delta WR decreased significantly with increasing severity in NYHA functional classification. delta VO2/delta WR showed significant negative correlation to the difference in NE levels at rest and at 20w (r = -0.69, p less than 0.001). The delta values of arteriovenous O2 content difference, calculated using Fick's principle, and cardiac index from rest to 20w warm-up failed to show significant relationship to delta VO2/delta WR. These results suggest that the decrease in VO2 requirement in heart failure patients is due probably to blood redistribution during exercise as a compensatory mechanism for exercise intolerance.