Effect of hydralazine on perfusion and metabolism in the leg during upright bicycle exercise in patients with heart failure

Abstract

The aerobic exercise capacity of patients with chronic heart failure is frequently impaired because of inadequate O2 transport to working skeletal muscle. To determine whether hydralazine improves O2 transport to working muscle, we examined the effect of intravenous hydralazine on blood flow (measured by thermodilution) and metabolism in the leg during maximal upright bicycle exercise in 10 patients with chronic heart failure. Hydralazine increased maximal exercise cardiac output (5.6 ± 0.7 to 6.7 ± 0.6 l/min; p < .01) and decreased systemic O2 extraction (79 ± 3% to 65 ± 2%; p < .03); the proportion of cardiac output delivered to the leg remained unchanged (59 ± 3% vs 57 ± 9%). This increase in flow was associated with a decrease in O2 extraction in the leg (84 ± 2% to 79 ± 2%; p