Thrombophilia in Patients with Occlusions of Vascular Bypass Grafts.

Background: Causes of vascular bypass occlusions are surgical failure, hyperplastic intima, progression of arterial occlusive disease and thrombophilic disorders. The aim of this registry was to determine the prevalence of thrombophilic risk factors in patients with occlusions of arterial bypass grafts of the lower extremities.

Patients and Methods: From 2001 to 2004 we studied 81 consecutive patients (pts) with a mean age of 60,5 years. 64/81 pts showed occlusions of arterial prosthetic grafts and 17/81 pts occlusions of venous grafts of the lower extremities. Bypass occlusion occured 7,1 months (mean value) after primary operation. 68/81 patients had concomittent risk factors for arteriosclerosis like arterial hypertension, diabetes, hypercholesterinemia or smoking.

The laboratory testing for thrombophilia (performed at least 4 weeks after the bypass occlusion) included antithrombin, protein C, protein S, homocysteine, factor V-G1691A-mutation, prothrombin-G20210A-mutation, lupus anticoagulant, anti-cardiolipin-antibodies, lipoprotein (a), factor VIII, plasminogen activator inhibitor (PAI) and induced platelet aggregation in platelet rich plasma with different concentrations of ADP to evaluate hyperreactive platelets.

Results: Thrombophilia screening revealed abnormalities in 65/81 pts. 36/81 patients showed combined defects. Screening for antiphospholipid antibodies (LA and/or ACA) revealed pathologic values in 31/81 pts, heterozygous factor V- mutation was present in 8/81 pts, heterozygous prothrombin-G20210A-mutation in 2/81. 20/81 pts had elevated homocysteine levels, 16/81 pts elevated lipoprotein (a) levels, 19/81 pts had a persistent factor VIII elevation higher than 200% and 14/81 pts had PAI-levels more than two fold higher than the upper normal value. There was 1/81 patient with protein S deficiency and 20/81 pts had abnormal platelet aggregation fulfilling the criteria of hyperreactive platelets.

Conclusions: In patients with occlusions of arterial bypass grafts of the lower extremities we found a high prevalence of hereditary and acquired thrombophilic risk factors. There seems to be a causal relation between arterial bypass occlusions and especially antiphospholipid antibosies. The evaluation of thrombophilic risk factors in patients with arterial bypass occlusions could lead to an improved antithrombotic treatment after surgical revasculation.