Too Many Strokes in Heart-Rhythm Patients Due to Coumadin Undertreatment
Daniel J. DeNoon
WebMD Health News
Reviewed By Louise Chang, MD
Aug. 28, 2008 — Far too many people with atrial fibrillation, an abnormal heart rhythm, suffer preventable strokes, a University of Toronto study suggests.
The "tragedy" is that Coumadin, an inexpensive blood thinner, could prevent about half of these strokes, yet few high-risk patients get proper treatment, says neurologist David J. Gladstone, MD, PhD.
"On one hand, we have an extremely effective and cheap medication for stroke prevention — Coumadin — yet on the other hand it remains under-used in people who would benefit most from it," Gladstone says in a news release.
Gladstone's team at the University of Toronto's Sunnybrook Health Sciences Center looked at 597 patients with atrial fibrillation who suffered a first stroke. Stroke in atrial fibrillation patients is particularly severe, so it's no surprise that 20% of the patients died and 60% suffered disabling strokes.
These patients, because of their age, diabetes, or other factors, were at particularly high risk of stroke. All of them should have been taking Coumadin with blood levels of the drug above 2.0 on a blood-thinness scale called the INR.
But only 10% of these stroke patients had an INR this high. Only 40% of these high-risk patients were getting Coumadin, and nearly 30% weren't getting any blood thinner at all.
The finding galls John Worthington, MBBS, of the University of New South Wales in Sydney, Australia.
"As a stroke specialist at two hospitals and a university, it is frustrating to see people disabled or even dying from avoidable stroke," Worthington tells WebMD. "If we were [giving Coumadin to] all the people that should be on this anticoagulant, we would reduce the amount of fatal and disabling stroke by at least 20% and often more. We have a gap between 20 years of compelling evidence about what we should do and what we actually do in treating the high stroke risk in atrial fibrillation."
This happens in the U.S., too, says Leonardo Tamariz, MD, MPH, assistant professor of medicine at the University of Miami Miller School of Medicine. In a soon-to-be-published study, Tamariz and colleagues found that only half of atrial fibrillation patients were taking Coumadin.
That's not too big a surprise, because not all patients are at high risk of stroke. But Tamariz found that high-risk patients were much less likely to be treated with Coumadin than low-risk patients.
"That is not concordant with the American College of Cardiology recommendations," Tamariz tells WebMD. "The ACC recommends that for low-risk patients you could actually use aspirin, because their lifetime stroke risk is about twice the normal risk. But high-risk patients should be on Coumadin because their stroke risk is 8% to 9%, and Coumadin could reduce it to 4%."
Coumadin: Lifesaver and Nuisance
What's the problem? Why aren't patients who should be on Coumadin getting the drug? And why are so many patients on Coumadin getting too little protection?
Coumadin is a brand name for the drug warfarin. Warfarin was originally invented to kill rodents. Later was it discovered that tiny doses of the drug act as a powerful blood thinner. But the therapeutic window — the difference between no effect, a helpful effect, and a harmful effect — is relatively small. And many factors, including other medical conditions or other drugs and dietary supplements, can drastically alter Coumadin's effect.
"Warfarin is known as rat poison for a reason," William O'Neill, MD, professor of medicine and cardiology at the University of Miami Miller School of Medicine, tells WebMD. "I am afraid patients at the highest risk of stroke are also those at highest risk of bleeding complications from Coumadin. It is very hard to maintain patients at the correct level long term. It is a real nuisance."
O'Neill's University of Miami colleague, electrophysiologist Robert Myerburg, MD, agrees with O'Neill that Coumadin is hard to manage.
"It is a nuisance for the patients. But the way I see it is that stroke is a bigger nuisance," Myerberg tells WebMD. "I don't know if Coumadin is underused. I agree with what this and other studies have shown: that atrial fibrillation patients inadequately anticoagulated or not on anticoagulants are at high risk of stroke."
Coumadin is a nuisance for doctors, too. It takes a lot of a doctor's time to manage Coumadin treatment, to assess elderly patients' risk of a fall (Coumadin ups the risk of deadly bleeding in elderly patients who fall) and to help patients go on and off the drug when they need a dental or surgical procedure.
Worthington agrees that Coumadin has suffered a poor reputation among patients and doctors. But he passionately argues that this poor reputation is undeserved.
"Warfarin is an inconvenient truth. Warfarin is inconvenient because regular blood tests are inconvenient," he says. "The truth, too, is inconvenient: We can reduce the chance of stroke and we do not always do this. Until we do what the evidence suggests — that is, start more people over age 65 with atrial fibrillation on Coumadin — individuals will suffer avoidable strokes and our health services will carry an avoidable [and] expensive burden of sick and disabled stroke patients."
Worthington and colleagues' editorial accompanies the Gladstone report in the January 2009 issue of the journal Stroke, published ahead of print on Aug. 28.
SOURCES: Gladstone, D.J. Stroke, January 2009; published online Aug. 28, 2008. Gattellari, M. Stroke, January 2009; published online Aug. 28, 2008. News release, American Heart Association. Email interview with John Worthington, MBBS, FRACP, Liverpool Health Service and Northern Beaches Hospitals, University of New South Wales, Sydney, Australia. William O'Neill, executive dean for clinical affairs and professor of medicine and cardiology, University of Miami Miller School of Medicine. Leonardo Tamariz, MD, MPH, assistant professor of medicine, University of Miami Miller School of Medicine; staff physician, Miami Veteran's Affairs Medical Center. Robert J. Myerburg, MD, professor of medicine and cardiology, University of Miami Miller School of Medicine.
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