The role of thrombophilic risk factors in the severity of pulmonary thromboembolism.

High plasma factor-VIIIc concentration, presence of factor-V 1691 G-A (FVL) and prothrombin20210A (PT20210A) mutations were shown to be significant risk factors for venous thromboembolism (VTE) and recurrent VTE. The objective of this study was to investigate the role of these thrombotic risk factors in the severity of pulmonary thromboembolism (PTE). The plasma concentrations of factor VIIIc, presence of FVL and PT20210A mutations were studied in 32 patients with PTE. Eleven of the patients had documented recurrent VTE. Lung perfusion scans were scored according to the percentage of vascular obstruction. Patients who had a pulmonary vascular obstruction score (PVOs) >50% were compared to those with PVOs <50%. There was no significant difference between the patients with PVOs >50% and those with PVOs <50%, with regard to the presence of FVL and PT20210A mutation. However, patients with PVOs >50% had a significantly higher factor-VIIIc concentration than those with PVOs <50% (factor-VIIIc levels were 253.3 +/- 29.1 International Units (IU) x dL(-1) and 138.5 +/- 16.2 IU x dL(-1), respectively; p<0.005). Factor-VIIIc concentrations were significantly correlated with PVOs (r=0.52, p<0.005). Patients with recurrent VTE had significantly higher factor-VIIIc concentrations than those in which it occurred for the first time (factor-VIIIc concentrations were 232.6 +/- 30.9 IU x dL(-1) and 158.3 +/- 20.6 IU x dL(-1), respectively; p<0.05). The authors conclude that in addition to being a risk factor for venous thromboembolism, high factor-VIIIc concentration is an important factor in the severity of pulmonary thromboembolism.