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Coronary vasoconstrictor response to cold pressor test in variant angina: lack of relation to intracoronary
Insights
Intracoronary thromboxane A2 levels do not affect coronary vasoconstriction during the cold pressor test in variant angina. Aspirin pretreatment did not alter this response, indicating thromboxane A2 is not a key factor in this condition.
Area of Science:
- Cardiology
- Pharmacology
Background:
- Variant angina is characterized by transient ST-segment elevation.
- Thromboxane A2 (TxA2) is a potent vasoconstrictor implicated in cardiovascular events.
Purpose of the Study:
- To investigate the role of intracoronary thromboxane A2 (TxA2) in the coronary vascular response to the cold pressor test (CPT) in patients with variant angina.
- To determine if aspirin pretreatment modifies this response.
Main Methods:
- Measured great cardiac vein blood flow and TxB2 concentrations in the great cardiac vein and aorta during CPT in 14 variant angina patients.
- Compared seven patients pretreated with aspirin to seven patients without aspirin.
Main Results:
- Aspirin pretreatment significantly reduced baseline TxB2 concentrations in both the great cardiac vein and aorta.
- Both groups showed an increase in anterior region coronary resistance during CPT.
- There was no significant difference in the vasoconstrictor response between aspirin-pretreated and non-pretreated groups.
Conclusions:
- Intracoronary TxB2 concentrations do not influence the vasoconstrictor response of coronary vessels to CPT in variant angina.
- Aspirin pretreatment does not modify the coronary response to CPT in this patient group.
Abstract:
To test the hypothesis that intracoronary concentrations of thromboxane (Tx)A2 could influence the response to cold pressor test (CPT) in variant angina, great cardiac vein blood flow (by thermodilution) and the concentration of TxB2 (the stable metabolite of TxA2) in the great cardiac vein and aorta were measured under control conditions and during CPT in 14 patients with angina at rest associated with transient ST-segment elevation in the anterior leads. In seven patients pretreated with aspirin (intravenous administration of 3.6 mg/kg lysine salt of acetylsalicylic acid, corresponding to 2 mg/kg aspirin), TxB2 baseline concentrations were lower in both the great cardiac vein (47 +/- 19 vs 176 +/- 88 pg/ml; p less than 0.005) and the aorta (45 +/- 16 vs 109 +/- 56 pg/ml, p less than 0.02) than in seven patients who were not taking cyclooxygenase inhibitors. In the two groups, great cardiac vein flow and anterior region coronary resistance were similar under control conditions. During CPT anterior region coronary resistance increased in patients pretreated with aspirin (from 1.97 +/- 0.99 to 2.22 +/- 1.11 mm Hg/ml/min; p less than 0.02) and in patients without aspirin pretreatment (from 1.94 +/- 0.43 to 2.06 +/- 0.34 mm Hg/ml/min; p less than 0.05), and the difference between the two groups was not statistically significant. Therefore the vasoconstrictor response of coronary vessels to CPT in variant angina is not influenced by the intracoronary TxB2 concentrations and is not modified by aspirin pretreatment.