Strategies for managing heparin therapy in patients with antiphospholipid antibody syndrome

Antiphospholipid antibody syndrome (APS) is a common acquired thrombophilia. The diagnosis of APS is based on both clinical and laboratory criteria. The clinical criteria include vascular thrombosis or pregnancy morbidity. The laboratory criteria include a positive test for lupus anticoagulant, anticardiolipin antibodies, or anti-β(2)-glycoprotein I (anti-β(2)GPI) antibodies on two or more occasions at least 12 weeks apart. Antiphospholipid antibodies with lupus anticoagulant activity may prolong phospholipid-dependent coagulation tests such as the activated partial thromboplastin time (aPTT) and the activated clotting time (ACT). This prolongation adds a level of complexity to monitoring heparin therapy in patients with APS who have thrombosis. A literature search of the PubMed database was conducted for relevant articles published from 1995-April 2011. The usual management approach in nonsurgical patients with APS is to switch to low-molecular-weight heparin. In patients in whom heparin remains the agent of choice, management options include monitoring heparin antifactor Xa levels, determining an individualized therapeutic aPTT range, targeting an aPTT goal of 2 times the baseline aPTT, or using an aPTT reagent insensitive to lupus anticoagulant. An algorithm for anticoagulation management in nonsurgical patients with APS who require heparin is provided. The strategies to monitor intraoperative heparin in patients undergoing cardiac surgery include measuring heparin concentrations by an automated protamine titration device, targeting twice the baseline ACT, using preoperative in vitro heparin-ACT titration curves, and measuring heparin antifactor Xa levels. The available published case reports on the use of these strategies are reviewed. Each institution should determine an approach to managing heparin in patients with APS that best meets its needs and resources.