Blood vials laid on top of a medical chart.

Study indicates blood thinners may not be needed during surgery in atrial fibrillation

Medicine is full of hard choices. For years, doctors have faced a difficult decision concerning surgery for patients with atrial fibrillation, the most common type of irregular heartbeat. These patients receive continuous treatment with a widely used blood thinner to prevent heart attack or stroke. But doctors often stop this treatment if surgery is scheduled in order to prevent excessive bleeding.

On the other hand, some doctors use another type of blood thinner with more easily reversible effects to “bridge” patients with atrial fibrillation who undergo surgery. They reason that this “bridging” approach might be safer than withdrawing blood thinners altogether.    

Without clear guidelines on which approach is best, the decision of whether or not to use bridging has become somewhat of a judgement call. Now, a research study funded by the National Heart, Lung, and Blood Institute (NHLBI) provides what scientists say is the first clear answer to this treatment dilemma: Blood thinners are not needed during surgery among patients with atrial fibrillation and may cause more harm than good.

In the study, the scientists showed that heart patients who stopped taking the blood thinner warfarin prior to surgery do not have an increased risk of stroke and have a lower risk of bleeding compared to patients who received a “bridge” therapy using another blood thinner. The finding helps resolve inconsistent practice guidelines that affect an estimated 250,000 surgery patients each year who are using warfarin for atrial fibrillation. The placebo-controlled study, called BRIDGE (which stands for Bridging Anticoagulation in Patients who Require Temporary Interruption of Warfarin Therapy for an Elective Invasive Procedure), appeared in the New England Journal of Medicine.

“The results of this study suggest that bridging, while commonly used, is not needed and may increase the risk of bleeding,” said Andrei Kindzelski, M.D., Ph.D., an NHLBI medical officer who provided an oversight of the study. “It’s a game-changing clinical trial that could lead to new medical guidelines for managing patients with atrial fibrillation who undergo planned surgery.”

Atrial fibrillation affects an estimated 3 million people in the United States alone. The condition causes the upper chambers of the heart to beat rapidly and irregularly. This uncontrolled quivering can cause the blood to pool and form clots, which can eventually lead to stroke or heart attack. As a result, doctors often prescribe the blood thinner warfarin for patients with this condition. These patients are usually advised to halt warfarin in the days before and after surgery. That’s because warfarin, one of the most widely used blood thinners, can cause dangerous amounts of bleeding during and after surgery.

To protect patients from this risk, doctors often prescribe low-molecular weight heparin, a blood thinner that has the same effect as warfarin but works faster and wears off more quickly. Doctors have been using this so-called “bridge” therapy for years, even though its usefulness was uncertain.

“Bridging has been controversial because there has been a lack of data demonstrating that it’s necessary, so people don’t know what to do,” said senior author Thomas L. Ortel, M.D., Ph.D., chief of the Division of Hematology at Duke University Medical Center in North Carolina, in a news release. He is a principal investigator for the study. “You can go to five different doctors, and some will bridge and others won’t – it just depends on what they feel they can safely do.”

The BRIDGE study, which ran from 2009 to 2015, included nearly 1,900 patients with atrial fibrillation from 108 clinical sites in the United States and Canada. Half received “bridge” therapy and the other half received placebo while halting warfarin for up to 13 days around their elective surgeries. Investigators studied the patients for up to 37 days after their procedures.

The incidence of blood clot was similar for both study groups. In the group that received placebo (no blood thinners), the incidence of blood clot was 0.4 percent, while the incidence of blood clot in the “bridge” therapy group was 0.3 percent. 

But the incidence of bleeding between the two groups was significantly different. About 1.3 percent of the patients on placebo developed severe bleeding, compared with 3.2 percent of the bridging group, the researchers said.

“Bridging does not improve the outcome for stroke prevention, but increases the risk of major bleeding complications,” Dr. Ortel said in the news release. “That’s the counter balance – we’re not doing patients any good, and we are potentially hurting them.”

Dr. Ortel pointed out that the findings are specific to patients with atrial fibrillation who are taking warfarin and should not be generalized to other patients using the blood thinner. He added that even though there are other alternatives to warfarin, the findings remain very relevant because the medication is still widely used among patients with atrial fibrillation.

Today, doctors continue to face a difficult choice of whether or not to bridge in patients with atrial fibrillation who undergo surgery. But thanks to the BRIDGE study, researchers hope that in the future more treatment decisions will be made based on the latest science rather than guesswork.  

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