Using Heparin After Cardioembolic Stroke Increases Risk Of Severe Bleeding

HOUSTON—(July 2008)—The common practice of giving patients the anticoagulant heparin after one of the most common forms of stroke can increase the risk of serious bleeding, according to researchers in the Department of Neurology at The University of Texas Medical School at Houston.

The research has been released in an online article posted July 14 that will appear in the September 2008 print edition of Archives of Neurology.

“This can potentially influence clinical practice,” said Hen Hallevi, M.D., neurology fellow at the UT Medical School at Houston and principal investigator of the retrospective study. “Our research reveals that 10 percent of patients placed on high-dose enoxaparin (Lovenox) after the cardioembolic stroke develop serious cerebral hemorrhaging.”

Enoxaparin is a low-molecular-weight heparin.

Cardioembolic stroke is a stroke caused by a clot traveling from the heart, which can occur in patients with atrial fibrillation (a flutter or abnormal heart rhythm). It accounts for 20 percent of ischemic stroke, the most common form of stroke.

After the stroke, patients routinely are placed on anticoagulants to prevent further strokes. But because the original stroke can also cause damage to the blood vessels and increase the risk of hemorrhage shortly after the stroke, the questions are when to start the anticoagulants and which ones to use.

According to previous research, the best anticoagulant to use is warfarin (Coumadin), but it takes several days to build up to a therapeutic level in the blood. So many physicians commonly “bridge” that time by giving patients heparin or high-dose enoxaparin despite a lack of studies proving efficacy.

“Although it’s a retrospective study, it may be enough evidence for some physicians to discontinue bridging with heparin or enoxaparin” said Sean Savitz, M.D., assistant professor of neurology at the UT Medical School at Houston and a co-author on the study.

Researchers studied 204 patients who had been admitted to Memorial Hermann – Texas Medical Center with cardioembolic stroke between 2004 and 2006. Of those, eight received no anti-clotting therapy, 88 received aspirin only, 35 received aspirin and warfarin, 44 received intravenous heparin and warfarin, and 29 received a full dose of enoxaparin, followed by warfarin. Those not receiving heparin or the full dose of enoxaparin also received low doses of enoxaparin to prevent blood clots in the legs or thighs.

Two of the patients (1 percent) had a recurrent stroke due to atrial fibrillation. All of the patients who developed serious cerebral hemorrhaging, 10 percent, received high doses of enoxaparin, the low-molecular-weight heparin. Systemic bleeding (bleeding in other areas of the body) occurred in two patients and was associated with heparin bridging. Patients who received only aspirin were at a higher risk of progressive stroke with worsening symptoms and poorer outcomes.

But the combination of aspirin and warfarin—even with a low-dose of enoxaparin—appeared to be safe and therapeutically helpful.

“If you give these stroke patients aspirin and warfarin, they don’t bleed and they don’t have another stroke,” Hallevi said.

James Grotta, M.D., senior author and chairman of the Department of Neurology at the UT Medical School at Houston, said the study further supports the use of warfarin in patients with atrial fibrillation.

“This is something not just for stroke specialists because atrial fibrillation is so common and a very untreated condition. This is important information for any medical doctor,” Grotta said.