▸ Pregnancy. Anticoagulation management during pregnancy is particularly important, as the risk of VTE in pregnant women is five times greater than in nonpregnant women, the authors stated. However, the available data are insufficient to recommend specific therapies in pregnant women. The guideline recommends avoiding vitamin K antagonists because they can cross the placenta and have been associated with fetal bleeding and embryopathy at 6-12 weeks' gestation. “Neither LMWH nor unfractionated heparin crosses the placenta, and neither is associated with embryopathy or fetal bleeding,” they wrote.
▸ Secondary and idiopathic VTE. For VTE secondary to transient risk factors, such as surgery, trauma, or immobilization, the available evidence indicates that patients may be well served with 3-6 months of oral anticoagulation therapy.
With respect to idiopathic VTE, available data suggest that extended-duration anticoagulation therapy is associated with a reduced relative risk of recurrence, although the optimal duration is not known as the length of therapy in the trials varied substantially, and the results reflect follow-up only to 4 years. Consequently, the guideline advises continuing anticoagulant therapy for more than 12 months for recurrent VTE.
▸ Long-term treatment. In comparing long-term treatment with LMWH versus vitamin K antagonists, the former is “safe and efficacious for the long-term treatment of VTE in selected patients, and may be preferable for patients with cancer,” as studies have linked LMWH to a survival advantage in this population. Specifically, the data suggest that “LMWH may be a useful treatment for patients in whom INR [international normalized ratio] control is difficult.”
▸ Pulmonary embolism. Regarding pulmonary embolism treatment, “LMWH is at least as effective as unfractionated heparin,” according to a review of the available evidence; thus, either drug is appropriate for initial treatment, said Dr. Vincenza Snow, director of clinical programs and quality of care for the ACP. The authors did note, however, that additional trials are needed to more rigorously examine the efficacy of LMWH for pulmonary embolism.