Platelet Activation and Fibrinopeptide Formation in Pulmonary Hypertension

Intravascular thrombosis is postulated to cause or to contribute to the development of uncharacterized (“primary”) pulmonary hypertension (PPH). To assess whether there is ongoing platelet-fibrin thrombosis in patients with PPH, we measured specific markers of platelet activation: platelet factor 4 (PF4) and s-thromboglobulin (BTC); of fibrin formation: fibrinopeptide A (FPA); and of fibrin dissolution: fibrinopeptide BB1-42 (FPBB1-42) in peripheral venous blood from 10 patients with PPH (group 2). Results were compared with those of normal volunteers (group 1, n = 9) and with results from patients with pulmonary hypertension secondary to congenital heart disease (group 3, n = 7). Both groups 2 and 3 exhibited severe pulmonary hypertension (mean pulmonary arterial pressure = 62 ±20 mm Hg and 70 ±13 mm Hg, respectively). Mean levels of PF4, BTC, FPA, and FPBB1-42 in patients with pulmonary hypertension, either primary or secondary to congenital heart disease, did not differ from levels in normal subjects. Within group 2, levels of platelet proteins and fibrinopeptides did not differ between patients who were classified clinically as having plexogenic arteriopathy vs thromboembolic disease. These observations suggest that a sustained state of abnormal platelet activation and fibrin formation or dissolution is not present in patients with established pulmonary hypertension.