Coronary vasoconstrictor response to cold pressor test in variant angina: Lack of relation to intracoronary thromboxane concentrations

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 <0.005) and the aorta (45 ± 16 vs 109 ± 56 pg/ml, p <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 <0.02) and in patients without aspirin pretreatment (from 1.94 ± 0.43 to 2.06 ± 0.34 mm Hg/ml/min; p <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.