Changes in Oxygen Uptake-Work Rate Relationship as A Compensatory Mechanism in Patients with Heart Failure : COMPENSATORY MECHANISMS AND THEIR LIMITATIONS IN HEART FAILURE

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To assess the compensatory change in oxygen uptake (VO_2) 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 VO_2 to increase in work rate (ΔVO_2/Δ WR) was determined by linear regression of VO_2 plots. Cardiac output by dye dilution method and plasma norepinephrine concentration (NE) were measured at rest and 20w warm-up. VO_2 at rest and at 20w warm-up and ΔVO_2/ΔWR decreased significantly with increasing severity in NYHA functional classification. ΔVO_2/ΔWR showed significant negative correlation to the difference in NE levels at rest and at 20w (r=-0.69, p<0.001). The delta values of arteriovenous O_2 content difference, calculated using Fick's principle, and cardiac index from rest to 20w warm-up failed to show significant relationship to ΔVO_2/ΔWR. These results suggest that the decrease in VO_2 requirement in heart failure patients is due probably to blood redistribution during exercise as a compensatory mechanism for exercise intolerance.
社団法人日本循環器学会の論文
1992-05-20