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Is Low Dose War..

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Recent trials suggest low dose anticoagulant therapy with a target INR of 1.5 to 2.5 may be as effective as a traditional INR goal of 2.0 to 3.0 in preventing thromboembolic (TE) complications in non-pregnant patients with mechanical aortic valves.1 However, because pregnancy induces a hypercoagulable state, and warfarin therapy poses significant risks to the fetus, the applicability of this management strategy during pregnancy has not been validated. While unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH) may have a higher risk of TE complications compared to warfarin during pregnancy, warfarin carries a much higher risk of fetal complications including embryopathy and fetal hemorrhage.2,3 There is limited data to suggest a dose-dependency of warfarin related embryopathy with warfarin doses of >5 mg daily being a predictor of poor fetal outcomes4,5.

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De Santo and colleagues published data from a small pilot, observational trial which enrolled young women with valvular disease who were not candidates for valve repair to examine the impact of multi-stage counseling for women undergoing valve surgery and the rate of TE and bleeding events and successful pregnancy with low-dose warfarin during pregnancy.2 Prior to valve surgery, patients were provided counseling on the risks and benefits of various valve choices, anticoagulant options, and maternal and perinatal complications associated with each option; the counseling included advice that avoiding pregnancy after surgery would be the safest alternative. To aid in the decision process, patients with a negative pregnancy test were given a 3 month trial of warfarin to determine if they would require an average daily dose of less than 5 mg to achieve a target INR. For women requiring aortic valve replacement who met the criteria defined by Torella et al1, the target INR was 1.5 to 2.5, but for women requiring mitral valve replacement the INR goal was 2.5 to 3.5. Women requiring <5mg per day of warfarin were recommended to receive a third generation mechanical device; women requiring more than 5mg per day were offered a bioprosthesis.2

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During the trial period, 22 women had valve replacement procedures (20 aortic and 2 mitral). Both patients who had mitral valve replacement required >5mg warfarin daily and received bioprosthetic valves. Seventeen patients who received aortic valves were maintained on <5mg of warfarin daily, and received a third-generation, St. Jude mechanical valve. The other 3 patients required >5mg warfarin daily; one received a bioprosthetic valve and 2 requested mechanical devices. Twenty of the women became pregnant after valve replacement surgery. Three pregnancies occurred in the patients who received a bioprosthetic heart valve, each resulting in a healthy fetus without structural degeneration of the valve. Sixteen pregnancies occurred in women with a mechanical prosthesis who were managed with low dose warfarin (mean 4.1 + 0.4mg per day) to maintain a mean INR of 1.9+0.3. Each pregnancy resulted in a healthy full term baby, and no maternal TE or hemorrhagic complications were observed. The majority of INR values (90.2%) were within the INR range. One patient with a mechanical valve became pregnant and opted to receive LMWH; despite compliance and close monitoring of peak anti-Xa levels, the patient experienced valve thrombosis at week 11. After emergency reoperation, the pregnancy was successfully completed utilizing ...

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