Higher-risk patients undergoing cardiac device surgery are better off continuing warfarin than switching to heparin as guidelines recommend, according to a New England Journal of Medicine study.

The study included nearly 700 patients at moderate-to-high risk for thromboembolic events who were taking warfarin and required nonemergency pacemaker or implantable cardioverter-defibrillator surgery. Patients were randomized to either continue warfarin (target INR: 3.0 or less; 3.5 or less for patients with mechanical valves) or receive bridging therapy with heparin as recommended by the American College of Chest Physicians.

The study was stopped early after an interim analysis found that the primary outcome — device-pocket hematoma — had occurred four times as often with heparin as with warfarin (16% vs. 3.5%). Continued warfarin didn’t increase major perioperative bleeding.

One explanation for the “counterintuitive” finding, the authors write, “is the concept of an ‘anticoagulant stress test.’ That is, if patients undergo surgery while receiving full-dose anticoagulation therapy, any excessive bleeding will be detectable and appropriately managed while the wound is still open. In contrast, if bridging therapy with heparin is used, such bleeding may be apparent only when full-dose anticoagulation therapy is resumed postoperatively.”

Source: NEJM