Fibrinopeptide A and platelet factor levels in unstable angina pectoris.

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Abstract
Fibrinopeptide A, platelet factor 4, .beta.-thromboglobulin, thromboxane B2, and 6-ketoprostaglandin F1.alpha. were estimated by radioimmunoassay on venous plasma samples taken within 48 hr of admission from 16 consecutive patients with unstable angina and 15 patients with stable angina matched for clinical variables. The rato of circulating platelet aggregates, platelet aggregation to increasing concentrations of ADP (0.455 to 1.82 .mu.g/ml), and platelet thromboxane B2 production in vitro were also tested. The two groups of patients were statistically similar in terms of sex distribution, age, presence of risk factors, use of medication, extent of coronary artery disease and history of previous myocardial infarction. Mean plasma levels of fibrnopeptide A were 2.7 .+-. 0.4 .+-. 0.4 ng/ml (geometric means .+-. SEM, range 1.5 to 5.5) in patients with stable angina vs. 5.5 .+-. 1.8 ng/ml (range 2.4 to 32; p < .001) in those with unstable angina. In the latter group, after 6 to 8 days, fibronopeptide A levels decreased to 3.6 .+-. 0.5 ng/ml (range 1.5 to 9.3; p < .04 vs admission). All other variables measured were statistically identical in two groups. We conclude that plasma fibrinopeptide A levels, as opposed to platelet factors, discriminate between patients with unstable and stable angina, indicating an activation of the coagulation system in unstable angina.