Metabolic assessment of exercise in chronic heart failure patients treated with short-term vasodilators.

Short-term vasodilators increase exercise cardiac output without an increase in exercise tolerance when administered to chronic heart failure patients. This study was designed to examine cardiac output, oxygen consumption, and lactate metabolism during exercise in chronic heart failure. Thirteen patients participated in 17 studies during control exercise (C) and during vasodilator exercise after short-term treatment with either hydralazine (H) or prazosin (P). Cardiac output increased during exercise both with hydralazine (C = 5.8 2.3 1/min,H = 6.9 i 2.3 1/min; p < 0.001) and with prazosin (C = 5.9 ± 2.3 1/min, P = 7.6 ± 2.7 1/min; p < 0.005). Oxygen consumption did not change during exercise either with hydralazine (C = 663 249 ml/min, H = 651 ± 200 mI/min; p > 0.10) or with prazosin (C = 696 ± 246 ml/min, P= 734 245 ml/min; p > 0.10). Peak blood lactate did not change either with hydralazine (C = 49.7 i 24.2 mg/dl, H = 44.0 ± 21.4 mg/dl; p > 0.05) or with prazosin (C = 33.8 ± 16.5 mg/dl, P = 32.1 i 12.2 mg/dl; p > 0.10). Vasodilators did not change the rate of lactate disappearance during