Coronary thrombosis is an important determinant of prognosis in patients with acute coronary syndromes (ACS). However, the identification of patients at high-risk for progression of coronary thrombosis is difficult partly because we currently lack clinically meaningful laboratory methods for its detection. The most promising approaches involve the measurement in plasma of markers of fibrin formation and degradation. Thrombin activity, as reflected by plasma or urine concentrations of fibrinopeptide A, is increased in patients with ACS and is associated with adverse outcome. However, the use of fibrinopeptide A as a marker of fibrin formation is limited by the very short half-life of the compound, by artifact due to sample acquisition, and by extremely long turnaround times. To overcome these limitations, measurement of soluble fibrin has been proposed. We have recently explored the prognostic value of a new fibrin-specific ELISA assay for soluble fibrin in patients with ACS and found that patients with the highest levels had a 2-fold increased risk of early and late cardiac events. Increases in plasma concentrations of cross-linked fibrin degradation products (XL-FDPs), which reflect increased fibrin turn-over, are a marker of risk for complications of myocardial infarction. However, until recently, assays for XL-FDPs lacked specificity, because they did not distinguish between fibrin and fibrinogen degradation products. Recently, fibrin-specific ELISAs have been described and a rapid whole blood assay for D-dimer has been developed. We recently validated the prognostic value of this whole blood agglutination assay in patients with ACS. These results suggest that: (1) The detection of significant activation of the coagulation and/or fibrinolytic system may be important for rapid risk stratification of patients with ACS; (2) patients with biochemical evidence of ongoing coronary thrombosis may particularly benefit from aggressive antithrombotic strategies; (3) sequential measurement of these markers may be useful to guide antithrombotic treatment during the unstable phase of coronary artery disease.
