Vasospasm of the internal thoracic artery (ITA) is common. The purpose of this study was to characterize the vascular reactivity of human ITA to dopaminergic agents used in patients undergoing coronary bypass surgery (CBS): dopamine, dobutamine, and dopexamine.Methods and Results.
Segments of the distal ITA 3 mm long were obtained from patients undergoing CBS, mounted on two stainless steel wires in a tissue bath filled with Krebs' solution at 37°C, and attached to a force-displacement transducer. To assess the functional status of the endothelium, the arterial segments were preconstricted with phenylephrine 10−5 mol/L and then exposed to increasing concentrations of acetylcholine (10−8 to 10−5 mol/L). To study vessel relaxation, segments were again preconstricted with phenylephrine 10−5 mol/L and concentration-relaxation responses to dopamine, dobutamine, and dopexamine (10−8 to 10−4 mol/L) were obtained. There was significant vessel relaxation with both dobutamine (log EC50=-5.83±0.16) and dopexamine (log EC50=-5.37±0.06) but none with dopamine. Vasoconstrictor effects of the drugs were studied from baseline tension. Neither dobutamine nor dopexamine caused vasoconstriction from baseline tension, whereas vessels exposed to dopamine showed constriction at high concentrations. The vessel responses to the dopaminergic agents did not differ according to the functional status of the endothelium as initially assessed by acetylcholine-induced vessel relaxation.Conclusions.
High-dose dopamine may aggravate ITA vasoconstriction, whereas dobutamine and dopexamine appear to cause vasodilation only. (Circulation.1993;88[part 2]:110–114.)