Coronary hemodynamic effects of intravenous vasoactive intestinal peptide in humans

Vasoactive intestinal polypeptide (VIP), a probable neurotransmitter, is present in the hearts of experimental animals and is a coronary vasodilator in dogs. We evaluated the coronary hemodynamic effects of intravenously infused VIP in 11 men at two rates that modestly raised circulating VIP concentrations. The decreases in coronary and systemic vascular resistances during the second infusion, 33 and 31%, respectively, were slightly but insignificantly greater than the 24% decrease in pulmonary vascular resistance. Coronary sinus levels of 6-keto-prostaglandin F1 alpha were not elevated during the infusions, and cyclooxygenase inhibition did not significantly blunt coronary vasodilation. However, myocardial oxygen uptake rose significantly during both infusions. To test for a direct coronary vasodilator effect, we infused VIP into the left coronary artery of four other men at four levels. The maximum decline in coronary vascular resistance was 46% and was not associated with an increase in myocardial oxygen uptake. We conclude that 1) intravenous administration of low to intermediate doses of VIP in humans is associated with substantial coronary vasodilation, 2) the coronary bed appears to be at least as responsive as other vascular beds, 3) the coronary vasodilation is due to both direct and indirect effects, and 4) the coronary vasodilation does not appear to be mediated by prostaglandins.