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
beta-thromboglobulin (BTG); 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 level of PF4, BTG, 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.