Effect of the sympathetic nervous system on limb circulation and metabolism during exercise in patients with heart failure

Abstract

During exercise in patients with heart failure, activation of sympathetic vasoconstrictor nerves may impair vasodilation in active skeletal muscle and thereby interfere with skeletal muscle blood flow. To investigate this hypothesis, we examined the effect of acute α-adrenergic blockade with systemic administration of prazosin (10 patients) or regional administration of phentolamine (eight patients) on blood flow, vascular resistance, oxygen consumption (V̇O2), and lactate release in the leg during maximal bicycle exercise in patients with heart failure. During control exercise, systemic V̇O2 increased to 12.6 ± 4.3 ml/min/kg (normal > 20 to 25 ml/min/kg), leg blood flow to 2.8 ± 1.8 liters/min, and leg lactate release to 362 ± 256 mg/min. Prazosin decreased systemic vascular resistance (12.5 ± 3.2 to 9.7 ± 2.5 units; p