New guidelines on antithrombotic therapy
create tough choices for women
Janelle Yates
OBG Management Senior Editor
Women who take a vitamin K antagonist (VKA), such as the anticoagulant warfarin, as long-term antithrombotic therapy face an increased risk of birth defects and miscarriage should they become pregnant. For that reason, they should stop taking VKA before 6 weeks’ gestation and substitute low-molecular-weight-heparin (LMWH) or unfractionated heparin (UFH).
There is one exception, however. Women who have certain types of mechanical heart valve should continue VKA therapy during pregnancy because the alternatives may not prevent stroke and valve thrombosis.
Those are some of the recommendations spelled out in a recent set of evidence-based guidelines that address the prevention and management of thrombosis in key patient populations and reinforce recommendations related to the routine use of preventive therapies.
The guidelines, Antithrombotic and Thrombolytic Therapy: ACCP Evidence- Based Clinical Practice Guidelines, 8th Edition, were developed by an international panel of 90 experts under the auspices of the American College of Chest Physicians (AACP).
“For years, clinicians have faced challenges in preventing and managing thrombosis in women who are pregnant or patients who require surgery,” said guidelines panel chair Jack Hirsh, MD, of Henderson Research Centre in Hamilton, Ontario. “The new guidelines address many troublesome issues in antithrombotic therapy and provide clinicians with a variety of options for care in special patient groups.”
Making the switch to LMWH or UFH
The AACP guidelines recommend two options for women planning to make the switch from VKA therapy:
- continue VKA during attempts to conceive but perform a pregnancy test frequently to determine when pregnancy has been achieved, followed by substitution of LMWH or UFH
- substitute LMWH or UFH before conception.
Although the second option eliminates the potential for fetal exposure to VKA, it is not without challenge. LMWH and UFH are more expensive than VKA and must be administered as once- or twice-daily injection—as opposed to a once-daily oral dose of VKA. In addition, long-term use of LMWH or UFH can be associated with osteoporosis.
“If women substitute heparin prior to pregnancy and have difficulties conceiving, they may find themselves taking the medication for a much longer timeframe than expected,” said guideline coauthor Shannon Bates, MD, of McMaster University and Henderson Research Centre in ManagementHamilton, Ontario. “This is not only inconvenient but also increases treatment costs and may be associated with long-term risks for the mother.”
Recommendations for surgical patients
Patients who are on long-term antithrombotic therapy who require surgery or other invasive procedures should usually temporarily stop receiving therapy just before the operation, as well as during the procedure, to minimize surgery-related bleeding. However, because stopping antithrombotic therapy can increase the risk of a thromboembolic event, the guidelines recommend weighing the risk of such an event against the risk for bleeding.
The guidelines also recommend routine use of thromboprophylaxis for patients who undergo major general, gynecologic, or orthopedic surgery, including bariatric surgery.
Thromboprophylaxis may not be warranted for low-risk patients
Overall, the AACP guidelines recommend thromboprophylaxis for most patients who are hospitalized, except for patient groups that have a very low risk of venous thromboembolism. Low-risk groups include patients undergoing laparoscopic surgery, knee arthroscopy, or those who take long airplane flights. For these patients, physicians can base decisions about thromboprophylaxis on the individual patient’s risk of thrombosis.
Aspirin is not the optimally effective preventative
The guidelines continue to recommend against the use of aspirin alone as a means to prevent venous thromboembolism in any patient population because more effective methods are available.
For more information You’ll find an executive summary of the guidelinesat www.chestjournal.org/content/133/6_suppl/71S.short?rss=1&ssource=mfc
Related article: Preventing VTE: Evidence-based perioperative tactics By Daniel L.Clarke-Pearson,MD www.obgmanagement.com/article_pages.asp?AID=4049&UID=52114
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