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Arterial thrombosis is usually associated with acquired risk factors such as diabetes, dyslipidemia, hypertension, obesity and smoking. Thrombophilic defects known to predispose to arterial thrombosis include hyperhomocysteinemia and antiphospholipid antibodies. The inherited thrombophilic disorders, including factor V Leiden (FVL), prothrombin gene mutation (PGM), and deficiencies of protein C (PC), protein S (PS), and antithrombin (AT), are well established risk factors for venous thromboembolism, however their association with arterial thrombosis is controversial. A recent review (Semin Hematol 44:106-113, 2007) addressed the prevalence and significance of these hereditary defects in relation to occlusive arterial disease (myocardial infarction, ischemic stroke, and peripheral arterial disease). Multiple studies and meta-analyses revealed conflicting results, however the authors concluded that the association between FVL and PGM and arterial occlusive disease is modest. PGM appears to be more often associated with arterial events than FVL, however results have been inconsistent. The very low prevalence of PC, PS, and AT deficiency has made it difficult to study the association of these genetic defects with arterial thrombosis. Routine screening for all these hereditary thrombophilic defects is not warranted in most cases of arterial thrombosis. There are, however, sub-groups of patients in whom there is a stronger association between thrombophilic defects and arterial thrombosis, most notably younger patients with age of onset < 45 years. In one study FVL was detected in 13.0% of patients with early presentation of myocardial infarction, significantly higher than the 3.8% prevalence in patients with older age presentation. In another study of myocardial infarction patients less than 36 years of age there was an increased prevalence of PGM (11.4%) compared with healthy young subjects (3.1%). Furthermore, in young patients environmental factors such as smoking and oral contraceptive use appear to have a synergistic effect with hereditary thrombophilia. One study reported an interaction between smoking and PGM for the risk of myocardial infarction in young women, with an odds ratio of 43 when both factors are present. Another subgroup to consider is early arterial occlusion occurring after revascularization procedures. Inherited thrombophilias have been reported to predispose to failure of revascu-larization procedures in patients with peripheral arterial disease, with a failure rate more than three-fold higher than in patients without the defects. The authors recommend that thrombophilia be excluded prior to such procedures in patients with a personal or family history of thrombosis, or early age onset of disease ( < 45 years). Testing for arterial thrombosis should include an antiphospholipid antibody panel and plasma homocysteine assay. Beyond this testing, current evidence does not support routine testing for the hereditary thrombophilic defects in most cases of arterial thrombosis. Testing for FVL and PGM is recommended, however, in two sub-groups of arterial thrombosis patients: those with early onset of disease ( < 45 years, or < 55 years in patients without the usual acquired risk factors for arterial disease), and those with early occlusion after revascularization procedures. |
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