American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the recommended anticoagulation strategy from weeks 37 to term for patients undergoing mechanical valve management?

1. Only weight-based LMWH

2. UFH (IV; aPTT 2 × control)

3. Discontinue all anticoagulation

4. Warfarin administration only

The correct answer is: UFH (IV; aPTT 2 × control)

In managing patients with mechanical valves during late pregnancy, from week 37 until term, the recommended anticoagulation strategy is to use unfractionated heparin (UFH) administered intravenously, maintaining activated partial thromboplastin time (aPTT) at 2 times the control level. This approach balances the risk of thromboembolic events, which patients with mechanical valves are susceptible to, with the risk of bleeding during delivery, which is heightened by certain anticoagulants. Using UFH allows for rapid reversibility, which is crucial as the delivery date approaches and the risks associated with anticoagulation must be carefully managed. In the event of labor or an emergency cesarean section, the effects of UFH can be quickly reversed by stopping the infusion, unlike other anticoagulants that may have longer half-lives or are not as easily adjusted. Weight-based low molecular weight heparin (LMWH) is generally not recommended in this scenario because it is not as easily reversible and might not achieve the target anticoagulation levels needed for those with mechanical valves. Discontinuing all anticoagulation is contraindicated due to the increased risk of thrombosis in patients with mechanical valves. Warfarin is also not advised during late