NEW YORK (Reuters Health) - When patients with atrialfibrillation need surgery or other invasive therapy, doctors can safely interrupt their warfarin therapy without offering a bridging anticoagulation regimen, according to a new U.S.-Canadian study.
The test of 1,884 patients treated at 108 centers found virtually identical rates of arterial thromboembolism in people who were switched to low-molecular-weight heparin and volunteers who got matching placebo twice daily immediately before and after the procedure.
In contrast, the incidence of major bleeding nearly tripled with bridging; it was 1.3% without heparin and 3.2% with the anticoagulant (p=0.005).
The study is "the first to give us really high-quality data. It allows us to make a recommendation that, at least with atrial fibrillation, you don't need to use bridging therapy," coauthor Dr. Thomas Ortel, chief of hematology at Duke University in Durham, North Carolina, told Reuters Health by phone.
"There may be certain high-risk patients where you may still wish to use it, but the vast majority of these patients really don't need anything done in the perioperative setting," he said.
The findings were presented Monday at the International Society on Thrombosis and Haemostasis 2015 Congress in Toronto and released online by the New England Journal of Medicine.
This is an issue doctors have wrestled with for years.
"Each year, this common clinical scenario affects approximately one in six warfarin-treated patients with atrial fibrillation," the researchers wrote in the Journal.
"Recommendations and guidelines have been conflicting," said Dr. Ortel. "We feel this is something more definitive."
In all patients, warfarin was halted five days before the procedure and restarted within 24 hours after the procedure.
In the bridging group, patients subcutaneously received 100 IU of dalteparin per kilogram of body weight or matching placebo twice daily, beginning three days before the procedure. Treatment was suspended 24 hours before the procedure.
Dalteparin/placebo therapy resumed within 24 hours after the procedure if that procedure carried a low risk of bleeding, and within 48 to 72 hours if the bleeding risk was high. Treatment continued until the international normalized ratio hit 2.0, usually for five to 10 days. Patients were followed for 30 to 37 days after the procedure.
In the placebo group, 0.4% developed an arterial thromboembolism versus 0.3% of the patients who received the heparin (p=0.01 for noninferiority). The rates were based on 1,813 patients who remained in the study until the end.
"For many of the patients it actually is not surprising because the risk of thromboembolism is pretty low," said Dr. Ortel. "But the issue has been that nobody has shown that you really can skip low-molecular-weight heparin as a bridge. There's quite a bit of conflicting thought out there among providers, as well as among patients, about whether something like this needs to be done."
"Major bleeding occurred in 1.3% of the patients (12 of 918) in the no-bridging group and 3.2% (29 of 895) in the bridging group, which indicated that no bridging was superior to bridging with regard to major bleeding," the researchers reported. None of the major bleeding episodes was fatal.
The two treatments produced no difference in the likelihood of death, acute myocardial infarction, pulmonary embolism ordeep vein thrombosis.
Dr. Ortel said the findings, if widely adopted, could save money by reducing the use of low-molecular-weight heparin and decreasing the expense of treating bleeding complications. "There are several different ways this could affect costs.
He cautioned that the study, known as BRIDGE, "does not apply to patients with prosthetic heart valves or patients with venous thromboembolism, like a deep vein thrombosis or pulmonary embolism. But for patients with atrial fibrillation, it's high-quality data that should indicate that people do not need to use anything to bridge these folks."
The National Heart, Lung, and Blood Institute funded this research. Ten coauthors reported relationships with pharmaceutical companies.