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Variable coronary vasomotor responses to acetylcholine in patients with normal coronary arteriograms: evidence for
D Tousoulis1, G Davies, D C Lefroy
1Cardiology Unit, Royal Postgraduate Medical School, Hammersmith Hospital, London.
Insights
In patients with chest pain and normal coronary arteries, acetylcholine caused both constriction and dilation in epicardial arteries, indicating potential endothelial dysfunction in specific segments.
Area of Science:
- Cardiology
- Vascular Biology
- Endothelial Function
Background:
- Chest pain in patients with angiographically normal coronary arteries is a clinical challenge.
- Epicardial coronary artery vasomotor responses are crucial for regulating blood flow.
Purpose of the Study:
- To investigate the vasomotor responses of epicardial coronary arteries to acetylcholine in patients presenting with chest pain and normal coronary arteries.
- To determine if acetylcholine induces differential responses in proximal and distal coronary artery segments.
Main Methods:
- Quantitative angiography was employed to measure minimum lumen diameter.
- Acetylcholine was infused intracoronary at varying concentrations (10(-7) - 10(-3) mol/l).
- Isosorbide dinitrate was administered as an intracoronary bolus to assess vasodilation.
Main Results:
- Acetylcholine induced both dilatation and constriction in proximal and distal coronary segments.
- Two distinct vasomotor response patterns (dilatation and constriction) were observed, coexisting in over half of the patients.
- Isosorbide dinitrate caused greater dilatation in distal segments compared to proximal segments in the dilatation group.
Conclusions:
- The findings suggest localized areas of endothelial dysfunction in patients with chest pain and normal coronary arteries.
- Differential responses to acetylcholine highlight the complexity of coronary vasomotor regulation.
- These observations may contribute to understanding the pathophysiology of chest pain in the absence of obstructive coronary artery disease.
Objective:
The vasomotor responses of the epicardial coronary arteries to acetylcholine were examined in patients with normal coronary arteries and chest pain.
Design:
Quantitative angiography was used to measure minimum lumen diameter of proximal and distal coronary artery segments at baseline, during intracoronary infusion of acetylcholine (10(-7) - 10(-3) mol/l), and following an intracoronary bolus (2 mg) of isosorbide dinitrate.
Patients:
Coronary arteriograms were obtained in 15 patients (mean (SEM) age 48 (10) years) with normal coronary arteries and chest pain.
Main Results:
In response to the low concentrations of acetylcholine (10(-7) - 10(-6) mol/1) 20 (61%) distal and 11 (41%) proximal segments showed dilatation (group 1), whereas 13 (39%) distal segments and 14 (52%) proximal segments showed constriction (group 2) (P < 0.05 v group 1). In group 1, the maximum dilatation induced by acetylcholine in the proximal and distal segments was 7.83 (1.19)% and 11.6 (2.2)% respectively. In group 2, the maximum constriction at higher concentration was 16.55 (3.3)% and 33.11 (11.63)% in the proximal and distal segments respectively. The two different patterns of the vasomotor response coexisted in eight (53%) of the 15 patients. Intracoronary isosorbide dinitrate caused a greater increase in the coronary luminal diameter of distal segments than in proximal segments in group 1 (25.63 (5.16)% v 12.43 (3.48)%, P < 0.01) but not in group 2 (12.65 (2.53)% v 10.82 (3.33)%.
Conclusions:
Constriction and dilatation may occur in proximal and distal coronary artery segments, suggesting local areas of endothelial dysfunction, in response to acetylcholine in patients with chest pain and angiographically normal coronary arteries.