Patients with atrial fibrillation who stopped taking blood thinners before they had elective surgery had no higher risk of developing blood clots and less risk of major bleeding compared to patients who were given a “bridge” therapy, according to research led by Duke Medicine in Durham, NC.

The findings add much-needed clarity to inconsistent practice guidelines that annually affect an estimated 250,000 patients with atrial fibrillation/flutter who take the blood thinner warfarin, according to the Duke researchers. The study was presented June 22, 2015, at the International Society on Thrombosis and Haemostasis meeting and published in The New England Journal of Medicine. (To access the abstract, go to http://bit.ly/1LshHSb.)

Atrial fibrillation patients typically are told to halt their warfarin for five days before and after they undergo an elective procedure, because it can cause dangerous bleeding and slow healing. After the procedure and resuming warfarin, it can take five or more days before the blood thinner reaches its effective target therapeutic level. To continue protecting them from blood clots during this intermission, many doctors prescribe a low-molecular weight heparin, a faster-acting blood thinner, in what is known as a “bridge” therapy.

“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, MD, PhD, chief of the Division of Hematology at Duke and the principal investigator of the Clinical Coordinating Center for the study. The study’s Statistical Data Coordinating Center, led by Vic Hasselblad, PhD, and the Clinical Coordinating Center were based at the Duke Clinical Research Institute.

“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,” Ortel said. “This trial gives a firm answer to that question.”

The study, named BRIDGE, enrolled 1,884 patients with atrial fibrillation and atrial flutter. Roughly half received the bridge therapy (dalteparin), and the other half received a placebo while halting their warfarin for up to 13 days around their elective surgeries. Patients were followed for up to 37 days after their procedures.

Among patients who stopped all blood thinners, the incidence of arterial blood clot was 0.4%, compared to 0.3% for patients who received the bridge therapy. Major bleeding events were significantly less common among the non-bridging group, occurring in 1.3% of patients who received no blood thinners, compared to 3.2% of those in the bridging group. “Bridging does not improve the outcome for stroke prevention, but increases the risk of major bleeding complications,” Ortel said. “That’s the counter balance: We’re not doing patients any good, and we are potentially hurting them.”

Ortel noted that the findings are specific to patients with atrial fibrillation who take warfarin and should not be generalized to other types of patients on the blood thinner. He said the findings also don’t cover newer blood thinners. However, the results will be taken into consideration by the organizations that develop guidelines for doctors on managing atrial fibrillation patients who plan to undergo a procedure or surgery.

“This is the first study to provide high-quality clinical trial data demonstrating that for patients with atrial fibrillation who need a procedure and who need to come off warfarin, they can simply stop and restart,” Ortel said. “They do not need to be bridged.”