Background: The hypothesis that intravenous L-arginine infusion improves the vasodilatory response to ischemia in the resistance vessels of human lower limbs in relatively young coronary heart disease patients taking vasodilating drugs was tested.
Methods: Twenty patients with onset of symptoms of coronary artery disease before age 50, operated for aortocoronary bypass and taking vasodilating drugs, were compared with 20 control subjects of comparable age and gender; neither group included heavy smokers (>10 cigarettes/day). Blood flow in the lower limbs was measured noninvasively with strain-gauge plethysmography, both at rest and during a reactive hyperemia test. Intravenous infusion of L-arginine was performed in nine coronary heart disease patients and in nine control subjects.
Results: Resting blood flow to the lower limbs was 2.3 mL/min/100 mL in control subjects vs 3.4 mL/min/100 mL in patients (difference not statistically significant). Peak blood flow measured after a 3-minute arterial occlusion was 24.0 mL/min/100 mL in control subjects vs 20.3 mL/min/100 mL in coronary heart disease patients (P<0.05). Peripheral minimal vascular resistances were 4.28 and 5.46 peripheral resistances units (p.r.u.) in control subjects and patients, respectively (P<0.05). Intravenous infusion of L-arginine was followed by increased resting blood flow in cases and controls (P=0.009), with a parallel reduction in peripheral resting vascular resistances (P=0.009). Coronary heart disease patients showed increased peak blood flow (P=0.04) and reduced minimal vascular resistances (P=0.02), whereas no statistically significant changes in these parameters were detectable in control subjects. Intravenous glucose infusion, leading to increased serum insulin concentration, did not modify any hemodynamic parameter.
Conclusions: Hemodynamic responses in the skeletal muscle are impaired during a reactive hyperemia test in relatively young coronary heart disease patients taking vasodilating drugs. Intravenous L-arginine infusion corrects the impaired vasodilatory response of the lower limbs to an acute increase in flow following a cuff thigh occlusion.