Use of Antithrombotic Agents During Pregnancy: Management of Pregnant Women With Prosthetic Heart Valves
Although the reported high rates of thromboembolism might be explained by inadequate heparin dosing and/or the use of an inappropriate target therapeutic range, this recent publication does raise the concern that patients with mechanical heart valves are resistant to moderate doses of heparin and draws attention to the need to use adequate heparin doses in these patients. Insufficient heparin dosing is associated with treatment failure, emphasizing the need for adequate initial heparinization and stringent monitoring. Contemporary APTT reagents are more sensitive to the anticoagulant effect of heparin and, therefore, a minimum target APTT ratio of 1.5 times the control is likely to be inadequate. A target APTT ratio of at least twice the control should be attained. Canadian-familypharmacy.com Here The higher rate of thromboembolic events reported in heparin-treated compared with warfarin-treated women is based on level V studies and is difficult to interpret because the adequacy of heparin dosing was usually not reported in these studies and because a minimum target APTT ratio of 1.5 times control was often used. Although long-term ql2h adjusted subcutaneous heparin has been shown to be effective and safe for the treatment of acute venous thrombosis, such doses of heparin might be less effective than warfarin in preventing arterial thromboembolism in patients with mechanical heart valves. There are no data available, however, to support or refute this conclusion.
At present, there are insufficient grounds to make definitive recommendations about optimal antithrombotic therapy in pregnant patients with mechanical heart valves because properly designed studies have not been performed. Substantial concern remains about the fetal safety of warfarin, the efficacy of subcutaneous heparin in preventing thromboembolic complications, and the risks of maternal bleeding with various regimens.