Effects of captopril on forearm oxygen consumption during dynamic handgrip exercise in patients with congestive heart failure.

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Abstract
The maximal exercise capacity of patients with congestive heart failure (CHF) is frequently decreased because of decreased skeletal muscle oxygen utilization. In this study we examined whether forearm oxygen utilization is decreased during dynamic handgrip exercise in patients with CHF and whether captopril improves forearm oxygen utilization. They were divided into 3 groups according to the level of plasma renin activity (PRA) and New York Heart Association functional classification (NYHA): Group 1 consisted of 7 normal (control) subjects (PRA: 0.5±0.2ng/ml/h, NYHA: 0); Group 2, 7 patients with severe CHF (PRA: 11.3±3.9ng/ml/h, NYHA: 3.6±0.3); Group 3, 4 patients with mild CHF (PRA: 2.4±0.2ng/ml/h, NYHA: 2±0). Forearm blood flow was measured by a strain gauge plethysmograph at rest and during dynamic handgrip exercise. Regional arterial venous oxygen content was measured and forearm oxygen consumption was calculated by the Fick principle. Forearm blood flow was less (p<0.05) at rest and during exercise in patients with severe CHF than in control subjects; this was compensated for by increased oxygen extraction, thus maintaining forearm oxygen consumption at a normal level at rest and during submaximal exercise. During maximal exercise, oxygen extraction was not different between normal control subjects and patients with severe CHF, thus forearm oxygen consumption was significantly less (p<0.01) in patients with severe CHF than in control subjects. In patients with mild CHF, forearm blood flow, oxygen extraction and oxygen consumption were not different from those in normal control subjects. Captopril (25mg orally) did not alter forearm hemodynamics at rest and during exercise in control subjects and patients with mild CHF. In patients with severe CHF, captopril lowered systolic and mean blood pressure (p<0.05). Captopril increased forearm oxygen extraction (p<0.05) and tended to increase blood flow and thus increased oxygen consumption (p<0.01) during maximal exercise. Our data indicate that oxygen utilization was impaired in patients with severe CHF and, that captopril improved forearm oxygen utilization during maximal handgrip exercise in patients with severe CHF.

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