Prostacyclin and Variant Angina

Plasma levels of thromboxane B2 (TXB2) and 6-keto PGF1 alpha in the blood samples taken at the coronary sinus and ascending aorta from twenty-one Japanese patients with variant angina and twenty with effort angina were measured by radioimmunoassay, the objective being to search for the contribution of prostanoids in coronary spasm. The data were compared with data on thirteen subjects free from coronary artery diseases. In coronary sinus blood, plasma TXB2 in patients with effort angina exhibited statistically significant high levels, as compared with data in the controls. These with variant angina also had high levels, albeit without a statistically significant difference. Eight patients with variant angina and for whom the coronary angiogram showed more than 50% of narrowing had statistically significant high levels of TXB2, and the other thirteen with variant angina and normal coronaries or less than 50% of narrowing had the same plasma levels of TXB2 as the controls. In contrast to TXB2, the plasma levels of 6-keto PGF1 alpha in both coronary sinus and aortic blood of patients with variant angina were very low, as compared with normal controls. Statistically significant low levels of 6-keto PGF1 alpha were noted in the coronary sinus blood of patients with variant angina with normal coronaries and in the aortic blood of those with variant angina, as compared with data on the normal controls. Neither ergonovine test nor spontaneous attacks in patients with variant angina revealed characteristic changes in levels of TXB2 and 6-keto PGF1 alpha in the coronary sinus. These data suggest that high levels of TXB2 in patients with atherosclerotic coronaries may be one factor leading to spasm, while low levels of PGI2 may be a contributing factor.