Mechanism of nitroglycerin-induced coronary dilatation: Lack of relation to intracoronary thromboxane concentrations

Intracoronary nitroglycerin (NTG) increases coronary blood flow and NTG inhibits thromboxane (Tx) A 2 production and release. However, whether an alteration in TxA 2 is the mechanism by which NTG increases coronary blood flow is not known. Coronary sinus (CS) blood flow (BF) (by thermodilution) and the concentration of TxB 2 (the stable metabolite of TxA 2) in CS blood were measured in 23 patients (16 men and 7 women, aged 26 to 65 years) with coronary artery disease before, during and after injection of normal saline solution (n = 5, control subjects) or NTG, 100 μg (n = 18), into the left coronary artery. In the 5 control subjects, saline solution caused no change in CSBF or the concentration of TxB 2 in CS blood. Ten of the 18 patients to whom NTG was given had received no cyclooxygenase inhibitors for 10 days. In these patients, NTG caused a marked increase in CSBF (from 112 ± 64 to 152 ± 70 ml/min, p