Plasma anticoagulant system in patients with pulmonary hypertension.

Adults with pulmonary hypertension and polycythemia (N = 22) have low levels of plasma antithrombin III (84 +/- 18 vs 98 +/- 13% for controls, N = 35, P less than 0.005) and protein C (66 +/- 21 vs 125 +/- 30%, N = 8, P less than 0.0002) but normal levels of total protein S. Data are reported as means +/- SD and percent normal values obtained for pooled plasma from normal healthy adults. Children with the same disorder (N = 6) also had low protein C levels (66 +/- 16 vs 85 +/- 5%, P less than 0.025). Total protein S was normal for children, but free protein S was decreased (66 +/- 13 vs 91 +/- 23%, P less than 0.025). Since the levels observed in these patients are above those reported for congenital deficiencies, the reduction in plasma levels of anticoagulant proteins may be the result of chronic intravascular coagulation. Furthermore, normal levels of plasminogen and fibrin degradation products suggest a localized disorder or an acquired decrease in fibrinolytic activity.