Anticoagulant therapy of pregnant patients with prosthetic heart valves: rationale for a clinical trial of low molecular weight heparin

Tinzaparin sodium for thrombosis treatment and prevention during pregnancy

OBJECTIVE

This study was undertaken to assess the pharmacodynamic profile, safety, and efficacy of tinzaparin during pregnancy.

STUDY DESIGN

Fifty-four pregnant women, 12 for treatment of thrombosis and 42 for thromboprophylaxis, received tinzaparin by once daily injection. Four-hour postdose anti-Xa results were analyzed by use of repeated measures statistical methods.

RESULTS

One woman (3.4%) on the 175 anti-Xa U/kg dose and three women (20%) on the 50 anti-Xa U/kg dose required a dose increase during the initial dose titration phase to achieve target anti-Xa activity. No thrombotic events occurred.

CONCLUSION

The 175 anti-Xa U/kg dose is appropriate for treatment and for high-risk thromboprophylaxis throughout pregnancy. In pregnant women at moderate risk of thrombosis, a higher tinzaparin dose is required than in the nonpregnant state and 75 anti-Xa U/kg appears to be appropriate. The majority of women do not need a dose increase with advancing gestation.

Antithrombotic therapy for prosthetic valves: routine treatment and special considerations

The use of prosthetic heart valves has increased over the past 3 decades. Antithrombotic agents remain the mainstay of therapy to prevent thromboembolic events caused by the presence of a prosthetic heart valve. We examine the risks of thromboembolic events as well as the risks and benefits of antithrombotic therapy in patients with mechanical and bioprosthetic heart valves. We also review the data regarding the use of antithrombotic therapy in special groups of patients, such as those with intracranial bleeding, pregnant women with prosthetic heart valves, and patients with prosthetic heart valves undergoing surgery.