Coronary Arterial Diameter and Coronary Hemodynamics in Humans

Effects of H1-receptor stimulation on coronary arterial diameter and coronary hemodynamics were examined in 11 patients with angiographically normal coronary arteries and without variant angina or resting angina. Selective H1-receptor stimulation was achieved by infusing histamine into the left coronary artery at a rate of 2.0 1£g/min for 5 minutes after pretreatment with cimetidine (25 mg/kg). Plasma histamine concentration in the coronary sinus, coronary sinus blood flow, heart rate, and aortic pressure were measured before, during, and after the histamine infusion. Coronary arterial diameter was measured by cinevideodensitometric analysis of coronary arteriograms performed before and immediately after the histamine infusion. During the histamine infusion, plasma histamine concentration in the coronary sinus increased from 0.33+±0.06 to 5.86±0.71 ng/ml (p<0.01); coronary sinus blood flow increased from 98±12 to 124±13 ml/min (p<0.01), and coronary vascular resistance decreased from 1,113±+117 to 851±91 mm Hg. min/l (p<O.Ol). Heart rate and aortic pressure remained unchanged. The mean luminal diameters of the proximal, middle, and distal left anterior descending artery increased by 9.4±3.6% (p<0.05), 19.2±3.8% (p<0.001), and 31.5±5.6% (p<0.001), respectively, after the histamine infusion. The mean luminal diameters of the proximal, middle, and distal left circumflex artery increased by 15.2±3.6%o (p<O.Ol), 17.5 ±5.2% (p<O.Ol), and 20.6±4.3% (p<O.OOl), respectively, after the histamine infusion. We conclude that histamine at the present dose dilates large coronary arteries as well as small coronary resistance vessels via H1-receptor stimulation in patients with angiographically normal coronary arteries and without variant angina or resting angina. (Circulation 1990;81:65-71)