Thrombophilias and recurrent pregnancy loss.

Thrombophilia by definition represents acquired and/or genetic conditions that predispose patients to both venous and arterial thromboembolic events. Thrombosis is the most common cause of death worldwide. On the arterial side, myocardial infarction and stroke result in significant morbidity and mortality. Venous thromboembolic events most commonly involve the deep veins of the lower extremity with potential complications of pulmonary emboli. Pregnancy is a hypercoagulable state, and thromboembolism is the leading cause of antepartum and postpartum maternal mortality. With the description by Dahlback in 1993 of a condition initially labeled activated protein C resistance, significant advances have rapidly followed. Activated protein C resistance was linked to an underlying point mutation resulting in coagulation factor V (factor V Leiden). Recent attention has focused on certain inherited thrombophilic factors that may predispose to arterial and/or venous thromboses and their possible association with pregnancy complications, including early pregnancy loss. These include a group of mostly autosomal dominant, inherited gene mutations leading to a hypercoagulable state, such as factor V Leiden G1691A, factor II or prothrombin G20210A, and hyperhomocysteinemia associated with methylenetetrahydrofolate reductase C677T mutation. In addition, deficiencies in protein S, protein C, and antithrombin can lead to a hypercoagulable state. Although some studies of recurrent pregnancy loss patients with a positive test for an inherited thrombophilia are conflicting, a case-control study of untreated recurrent miscarriage patients who were heterozygous for the factor V Leiden mutation revealed a lower success rate than the controls who had a history of idiopathic recurrent miscarriage. With the identification of genetic risk factors, there has been synergistic amplification of thrombotic risk when one has an abnormal gene (e.g., factor V Leiden) plus environmental issues (e.g., pregnancy). Current understanding indicates that a combination of risk factors, including multiple inherited thrombophilic defects associated with secondary hypercoagulable states, have a particularly strong association with adverse pregnancy outcome.

Inhibition of Binding of ß2-Glycoprotein 1 to Phosphatidylserine by Polymyxin B, a Lupus-Like Anticoagulant.

Polymyxin B is a cationic peptide that inhibits phospholipid-dependent coagulation tests including activated partial thromboplastin time and to a lesser degree prothrombin time. Thrombin clotting time is insensitive to polymyxin B. ß2-glycoprotein 1 (ß2GP1) is a cofactor of antiphospholipid antibodies. Antiphospholipid autoantibodies also poses lupus anticoagulant activity through interactions with ß2GP1. Using affinity chromatography, polymyxin B can effectively decrease the binding of ß2GP1 to immobilize phosphatidylserine. Since then, anticoagulant effect of polymyxin B is most likely due to the binding to negatively charged phospholipids, preventing formation of coagulation complexes.

Comprehensive hypercoagulable state testing is indicated in patients with a first idiopathic deep venous thrombosis.

A 45-year-old man presents with a 3-day history of right leg swelling and pain. He is diagnosed with an acute right common femoral vein thrombosis. He takes no medications, has an unremarkable medical history, no recent trauma or surgery, no recent travel, and no known cancer. Performance of a comprehensive hypercoagulable state panel is contemplated.

Antiphospholipid antibodies.

OBJECTIVE: To review the role of lupus anticoagulants in the pathogenesis of both venous and arterial thromboembolic events, as well as in recurrent spontaneous abortions. The pathophysiology of lupus anticoagulants and associated antiphospholipid antibodies (eg, anticardiolipin antibodies) is also discussed. DATA SOURCES: Review of the recent medical literature. DATA EXTRACTION AND SYNTHESIS: Key articles in the recent medical literature dealing with lupus anticoagulants and their role in pathogenesis of thromboembolic events were reviewed. Plasma proteins that have an affinity for binding to "perturbed cellular membranes" have been identified as the antigenic targets for antiphospholipid antibodies. Thus, the concept of antiphospholipid antibodies needs to be reevaluated. Perhaps a better term is antiprotein-phospholipid antibodies. The principal antigenic protein targets are beta(2)-glycoprotein I, prothrombin, and a wide range of additional proteins that interact with activated cellular membranes, including protein C, protein S, annexin V, etc. Most research reported in the literature has focused on beta(2)-glycoprotein I and human prothrombin.

Antiphospholipid antibodies.

Antiphospholipid antibodies (APAs) have been associated with thromboembolic events. Since they were fi rst described in 1906, APAs have been the subject of multidisciplinary studies seeking to link them to potential pathophysiologic mechanisms. This review summarizes the different types of APAs, antigenic targets, clinical complications associated with APAs, and APA syndrome. In addition, the currently available methods for laboratory identification of lupus anticoagulants are discussed, as is the laboratory diagnosis of anticardiolipin antibodies.

Antiphospholipid antibodies and subsequent thrombo-occlusive events in patients with ischemic stroke.

CONTEXT: The presence of antiphospholipid antibodies (aPL) has been associated with vascular occlusive events. However, the role of aPL in predicting ischemic events, particularly recurrent ischemic stroke, is controversial. OBJECTIVE: To evaluate the effect of baseline aPL positivity (ie, positivity for anticardiolipin antibodies [aCL], lupus anticoagulant antibodies [LA], or both) on subsequent thrombo-occlusive events, including recurrent stroke. DESIGN, SETTING, AND PARTICIPANTS: The Antiphospholipid Antibodies and Stroke Study (APASS), a prospective cohort study within the Warfarin vs Aspirin Recurrent Stroke Study (WARSS), a randomized double-blind trial (N = 2206) conducted at multiple US clinical sites from June 1993 through June 2000 and comparing adjusted-dose warfarin (target international normalized ratio, 1.4-2.8) and aspirin (325 mg/d) for prevention of recurrent stroke or death. APASS participants were 1770 (80%) WARSS participants who consented to enroll in the APASS, with usable baseline blood samples drawn prior to randomization to the WARSS and analyzed for aPL status within 90 days of index stroke by a central independent laboratory. Quality assurance was performed on approximately 10% of samples by a second independent laboratory. MAIN OUTCOME MEASURE: Two-year rate of the composite end point of death from any cause, ischemic stroke, transient ischemic attack, myocardial infarction, deep vein thrombosis, pulmonary embolism, and other systemic thrombo-occlusive events. The primary analysis assessed the outcome associated with aPL positivity within each WARSS treatment group separately, after risk-factor adjustment (since these aPL-positive vs aPL-negative comparisons were not randomized). RESULTS: Of the 1770 APASS patients, 720 (41%) were classified as aPL-positive and 1050 (59%) as aPL-negative. There was no increased risk of thrombo-occlusive events associated with baseline aPL status in patients treated with either warfarin (relative risk [RR], 0.99; 95% confidence interval [CI], 0.75-1.31; P =.94), or aspirin (RR, 0.94; 95% CI, 0.70-1.28; P =.71). The overall event rate was 22.2% among aPL-positive and 21.8% among aPL-negative patients. There was no treatment x aPL interaction (P =.91). Patients with baseline positivity for both LA and aCL antibodies tended to have a higher event rate (31.7%) than did patients who tested negative for both antibodies (24.0%) (unadjusted RR, 1.36; 95% CI, 0.97-1.92; P =.07). Classification and regression tree analyses did not identify a specific LA test or aCL isotype or titer that was associated with increased risk of thrombo-occlusive event. CONCLUSIONS: The presence of aPL (either LA or aCL) among patients with ischemic stroke does not predict either increased risk for subsequent vascular occlusive events over 2 years or a differential response to aspirin or warfarin therapy. Routine screening for aPL in patients with ischemic stroke does not appear warranted.