Circadian variation of plasma fibrinopeptide A level in patients with variant angina.

Plasma levels of fibrinopeptide A (FPA), beta-thromboglobulin (BTG), and platelet factor 4 (PF4) were examined on venous plasma samples taken every 4 hours for 24 hours in 20 patients with variant angina and 20 patients with stable exertional angina together with 24-hour Holter recordings. The mean plasma FPA levels (ng/ml) at 2:00 PM, 6:00 PM, 10:00 PM, 2:00 AM, 6:00 AM, and 10:00 AM were 4.6 +/- 1.0, 3.1 +/- 0.5, 6.1 +/- 1.6, 9.9 +/- 2.4, 8.7 +/- 1.4, and 4.2 +/- 0.8 in patients with variant angina (p less than 0.01) and 1.8 +/- 0.2, 2.3 +/- 0.3, 1.9 +/- 0.3, and 2.3 +/- 0.2 in those with stable exertional angina. In seven patients with variant angina, we also examined the effects of heparin (3,000 units), given subcutaneously at 6:00 PM, 10:00 PM, and 2:00 AM, on the plasma FPA levels and the anginal attacks. Although heparin suppressed the elevation and circadian variation of plasma FPA levels, it did not suppress the attacks and their circadian variation in these patients. Plasma FPA levels increased significantly from 3.7 +/- 0.5 to 12.5 +/- 2.7 ng/ml during or immediately after an attack in the seven patients with no heparin. On the other hand, the plasma levels of BTG and PF4 were increased in patients with variant angina as compared with those with stable exertional angina but did not show a significant circadian variation in both groups. We conclude that 1) plasma levels of FPA, BTG, and PF4 were increased in patients with variant angina as compared with those with stable exertional angina; 2) there was a significant circadian variation in the plasma levels of FPA in parallel with that of the frequency of the attacks with the peak level occurring from midnight to early morning in patients with variant angina; and 3) elevated levels of plasma FPA are the result and not the cause of coronary spasm.