Fibrinopeptide A: A marker of acute coronary thrombosis

To determine whether coronary thrombosis in vivo is reflected by elevations in levels of fibrinopeptide A (FPA) in plasma, we sequentially characterized plasma FPA levels associated with evolving infarction in patients admitted to the cardiac care unit early after the onset of symptoms, in patients with transmural infarction admitted later, and in patients with nontransmural infarction. Studies were also performed in patients in whom the diagnosis of infarction was suspected but subsequently excluded. FPA values were significantly higher in patients with transmural infarction (42.3 ± 11.2 ng/ml [mean ± SEM], n = 53) compared with those in patients with nontransmural infarction (4.8 ± 1.6 ng/ml, n = 17) or with those in patients in whom infarction was subsequently excluded as a diagnosis (3.5 ± 0.6 ng/ml, n = 17, p < .01 for both). Elevations in FPA level were greatest in patients with transmural infarction from whom samples were obtained soon after the onset of symptoms. Thus, in 39 patients from whom samples were obtained within 10 hr after the onset of symptoms, FPA levels were significantly higher than in 14 patients from whom samples were obtained initially more than 10 hr after the onset of symptoms (55.5 ± 14.7 vs 4.9 ± 1.4 ng/ml, p < .01). In 30 of the 39 patients with evolving transmural infarction from whom samples were obtained within the first 10 hr after the onset of symptoms, the level of FPA was greater than 8 ng/ml. In contrast, FPA level was greater than 8 ng/ml in only two of the 14 patients from whom initial samples were obtained more than 10 hr after the onset of symptoms. In patients admitted early after transmural infarction from whom samples were obtained sequentially (n = 8), FPA values declined consistently during the 24 hr sampling interval. Thus, an elevated FPA level appears to be a criterion of acute coronary thrombosis.