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Effects of H1-receptor stimulation on coronary arterial diameter and coronary hemodynamics in humans
K Matsuyama1, H Yasue, K Okumura
1Division of Cardiology, Kumamoto University Medical School, Japan.
Insights
Histamine H1-receptor stimulation dilates coronary arteries and improves blood flow in healthy individuals. This study shows histamine increases coronary arterial diameter, enhancing coronary hemodynamics.
Area of Science:
- Cardiovascular Physiology
- Pharmacology
Background:
- Histamine's role in coronary circulation is not fully understood.
- Previous research has not extensively explored H1-receptor mediated coronary vasodilation.
Purpose of the Study:
- To investigate the effects of selective H1-receptor stimulation on coronary arterial diameter and hemodynamics.
- To assess histamine's impact on coronary blood flow and resistance in individuals with normal coronary arteries.
Main Methods:
- 11 patients with normal coronary arteries underwent selective left coronary artery histamine infusion after cimetidine pretreatment.
- Coronary arterial diameter was measured using cinevideodensitometry.
- Coronary sinus blood flow, heart rate, aortic pressure, and plasma histamine were monitored.
Main Results:
- Histamine infusion significantly increased plasma histamine levels and coronary sinus blood flow.
- Coronary vascular resistance decreased significantly during histamine infusion.
- Mean luminal diameters of the left anterior descending and left circumflex arteries increased significantly, indicating vasodilation.
Conclusions:
- Selective H1-receptor stimulation with histamine causes significant coronary vasodilation in humans.
- Histamine administration improves coronary hemodynamics by increasing arterial diameter and blood flow.
- These findings suggest a role for H1-receptors in regulating coronary blood flow.
Abstract:
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 micrograms/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 less than 0.01); coronary sinus blood flow increased from 98 +/- 12 to 124 +/- 13 ml/min (p less than 0.01), and coronary vascular resistance decreased from 1,113 +/- 117 to 851 +/- 91 mm Hg.min/l (p less than 0.01). 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 less than 0.05), 19.2 +/- 3.8% (p less than 0.001), and 31.5 +/- 5.6% (p less than 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% (p less than 0.01), 17.5 +/- 5.2% (p less than 0.01), and 20.6 +/- 4.3% (p less than 0.001), respectively, after the histamine infusion.(ABSTRACT TRUNCATED AT 250 WORDS)