'Bridging' Anticoagulation May Not Be Necessary

November 13, 2011

November 13, 2011 (Orlando, Florida) — A National Heart, Lung, and Blood Institute (NHLBI)–funded study on the issue of "bridging" patients on long-term anticoagulation who need to undergo invasive procedures will help inform many unanswered questions on this controversial topic, says one expert in the field.

Speaking to a packed room at the American Heart Association 2011 Scientific Sessions this morning, with his talk being broadcast outside to those who could not get in, Dr Samuel Z Goldhaber (Brigham and Women's Hospital, Boston, MA) did a quick poll of his audience and discovered that 90% had "bridged" patients. "But there is a lack of evidence. There are no randomized clinical trials to say that bridging is the way to go," he observed.

In fact, bridging "creates all sorts of miscommunications and logistical nightmares, and it's hard to get everyone on the same page," he said. Despite the belief that bridging is required--without any scientific proof to indicate this--there is some evidence that it is unnecessary in the vast majority of patients and that routine bridging can do more harm than good, he noted. In fact, one of the few published studies to have examined this issue found that thromboembolism (TE) is uncommon in low- or intermediate-risk patients interrupting warfarin for five days or less [1], he noted.

And, far from being benign, frequent bleeding complications can result from bridging, and these can cause incisional pain, increase the length of hospital stays, and predispose patients to infections, Goldhaber cautioned.

Whom Not to Bridge: Dental, Cataract, and Colonoscopy Patients

Translating some of the terminology employed for attendees, he explained that "bridging in" means taking people off warfarin prior to a surgery or procedure and substituting it with another form of anticoagulation; "bridging out" refers to the postoperative period; "full bridging" means the use of full-intensity anticoagulation, such as IV unfractionated heparin; and "prophylactic bridging" indicates a low preventive dose of treatments such as low-molecular-weight heparin.

There are no randomized clinical trials to say that bridging is the way to go.

Goldhaber said the NHLBI trial should provide many answers but unfortunately will not report results until 2015, "and we have to bridge between now and then."

He offered guidance on those he definitely believes do not require bridging: people undergoing dental cleaning and simple extraction, a recommendation that is supported in the latest guidelines from the American Dental Association, he noted. And those undergoing cataract surgery "simply don't need to have their warfarin interrupted," he observed, adding "most eye surgeons agree with this."

Those undergoing cataract surgery simply don't need to have their warfarin interrupted. Most eye surgeons agree with this.

Finally, patients who need to undergo colonoscopy do not need bridging either, he noted, pointing out there "is a new generation of endoscopists, generally those who are under the age of 45, who are usually willing to snare the polyps when patients are on full-dose warfarin."

Importantly, he notes also that the ACC/AHA 2006 guidelines for the management of patients with valvular heart disease advise not bridging patients with mechanical aortic valves who have no other risk factors [2].

Conversely, those who are "high risk" definitely should receive bridging, he noted, citing among these patients those with multiple prosthetic valves or "advanced" mitral-valve disease and AF patients with a CHADS score of 3 or higher. In these people, it's important not to forget the option of intravenous unfractionated heparin given in the hospital, noted Goldhaber.

NHLBI Study Ongoing, But Will Newer Drugs Make Bridging Unnecessary?

The NHLBI study has so far enrolled 686 out of a planned 3600 patients with AF who require temporary interruption of warfarin, and its aim is to compare the efficacy of bridging anticoagulation (with a therapeutic dose of the low-molecular-weight heparin dalteparin, 100 IU/kg subcutaneously twice daily) with no bridging (placebo) on the rate of arterial thromboembolic events (ATE) and on the rate of major bleeding.

There is a new generation of endoscopists, generally who are usually willing to snare the polyps when patients are on full-dose warfarin.

The study hypotheses are that withholding warfarin for five days prior to surgery and restarting it afterward will prove noninferior to a bridging strategy for the outcome of ATE at 30 days and that this approach will be superior to a bridging strategy for the outcome of major bleeding at 30 days.

Of course, Goldhaber concluded, the use of novel anticoagulants may ultimately make bridging unnecessary; he observed, however, that there are "instructions on bridging with dabigatran [Pradaxa, Boehringer Ingelheim]" in the package insert for the new drug.

Depending on renal function, dabigatran should be stopped between one to five days before a procedure, although longer times should be considered in those undergoing major surgery, spinal puncture, or epidural catheter. Bleeding risk in these patients can be assessed by the ecarin clotting time (ECT) or activated partial thromboplastin time (aPTT), he noted.

Goldhaber reports receiving consulting fees from Boehringer Ingelheim, Bristol-Myers Squibb, Daiichi Sankyo, Eisai, EKOS, Medscape, Merck, Portola, and Sanofi-Aventis and grant support through his institution from Boehringer Ingelheim, Bristol-Myers Squibb, Eisai, EKOS, Johnson & Johnson and Sanofi-Aventis. He is the author of Clotblog on theheart.org.