MKSAP Quiz: Preconception counseling for mitral stenosis
A 26-year-old woman seeks preconception counseling. She has a history of mitral stenosis and underwent mitral valve replacement with a tilting-disc mechanical prosthesis 5 years ago. Following a physical exam, lab studies, and electrocardiogram, what is the most appropriate anticoagulation regimen for this patient during the first trimester?
A 26-year-old woman seeks preconception counseling. She has a history of mitral stenosis and underwent mitral valve replacement with a tilting-disc mechanical prosthesis 5 years ago. She is asymptomatic. Medications are warfarin, 4 mg/d, and low-dose aspirin.
On physical examination, a normal mechanical S1 and normal S2 are appreciated. The remainder of the examination is unremarkable.
Laboratory studies reveal an INR of 3.0 (therapeutic target, 3.0).
An electrocardiogram demonstrates normal sinus rhythm.
In addition to continuing low-dose aspirin, which of the following is the most appropriate anticoagulation regimen for this patient during the first trimester?
A. Continue INR-adjusted warfarin
B. Stop warfarin and start apixaban
C. Stop warfarin and start unfractionated heparin, 5000 units subcutaneously twice
daily
D. Stop warfarin and start weight-based low-molecular-weight heparin
MKSAP Answer and Critique
The correct answer is A. Continue INR-adjusted warfarin. This content is available to MKSAP 18 subscribers as Question 80 in the Cardiovascular Medicine section. More information about MKSAP is available online.
The most appropriate anticoagulation regimen to prevent prosthesis thrombosis in this patient is INR-adjusted warfarin. Pregnant women with a mechanical valve prosthesis represent a high-risk subset of patients; concerns include valve thrombosis with its associated maternal risk, bleeding, and fetal morbidity and mortality. Warfarin anticoagulation appears to be the safest agent to prevent maternal prosthetic valve thrombosis; however, warfarin poses an increased fetal risk, with possible teratogenicity, miscarriage, and fetal loss due to intracranial hemorrhage. Risk to the fetus is dose related, and warfarin is the preferred anticoagulation regimen during the first trimester when the dose is 5 mg daily or less. During the second and early third trimesters, warfarin therapy is the preferred anticoagulation therapy.
Anticoagulation with apixaban is not recommended in patients with a mechanical valve prosthesis because of the potentially increased risk for valve thrombosis. In addition, its use has not been demonstrated to be safe during pregnancy.
In patients who prefer not to take warfarin during the first trimester of pregnancy, dose-adjusted intravenous unfractionated heparin can be used; however, 5000 units of unfractionated heparin will not provide adequate anticoagulation coverage for a patient with a mechanical prosthetic valve. Dose-adjusted, intravenous unfractionated heparin is an appropriate therapeutic option during the first trimester of pregnancy if the warfarin dose is more than 5 mg daily. Intravenous unfractionated heparin is the drug of choice for patients with a mechanical valve prosthesis around the time of delivery.
Weight-based low-molecular-weight heparin does not provide adequate anticoagulation coverage for a pregnant patient with a mechanical valve prosthesis and should not be used in this patient. Dose-adjusted low-molecular-weight heparin administered subcutaneously is appropriate during the first trimester if the warfarin dose is more than 5 mg daily.
Key Point
- In pregnant patients with a mechanical valve prosthesis, warfarin is the preferred anticoagulation therapy during the first trimester if the dose is 5 mg daily or less; warfarin is preferred to all other anticoagulants during the second and early third trimesters.