(HealthDay is the new name for HealthScoutNews.)
WEDNESDAY, Aug. 13, 2003 (HealthDayNews) -- A new study appears to have settled one of the trickiest questions in medicine: How best to prevent the potentially fatal blood clots in the condition called deep vein thrombosis (DVT).
Or maybe it hasn't, depending on which expert you ask.
DVT can lead to recurrent clots that at the least cause severe discomfort and at the worst can kill the patient by traveling to the lungs and blocking the pulmonary artery. As many as 60,000 Americans are killed each year by these pulmonary embolisms, says Dr. Yves Rosenberg, a project officer at the National Heart, Lung, and Blood Institute who is an expert on the subject.
Recurrent clots can be prevented by giving patients warfarin (also known as Coumadin), an effective blood thinner. But too-high doses of warfarin can cause bleeding that can be damaging or fatal. Study after study has tried to determine what dose will best prevent clots while causing the minimum of dangerous bleeding.
A study led by Rosenberg earlier this year concluded that long-term treatment with lower-than-standard doses of warfarin effectively prevented clots over the long run with a minimum of bleeding. The results were so impressive the study was cut short to inform doctors about it.
But a new study now finds that while low-dose warfarin is good, standard -- higher -- doses are better. The study included 738 people who had suffered deep-vein clots. The 369 patients assigned to low-dose therapy experienced 16 clots, an incidence of 1.9 per 100 person-years, while there were only six clots in the 369 patients given standard therapy, 0.7 per 100 person-years, says a report in the Aug. 14 issue of the New England Journal of Medicine.
And the incidence of serious bleeding episodes was almost the same in both groups -- eight in the standard-dose group, nine in the low-dose group.
"We were surprised that the usual-dose warfarin treatment did not cause more bleeding," says study author Dr. Clive Kearon, an associate professor of medicine at McMaster University in Hamilton, Ontario.
An accompanying editorial says "it appears that the debate about the intensity of warfarin therapy for venous thromboembolism is now settled," and Kearon says he agrees.
Rosenberg is not so sure. "You cannot say that long-term treatment with the regular dose not increase the risk of bleeding episodes," he says, arguing that the results achieved in such a carefully controlled trial might not be possible in ordinary clinical practice.
He acknowledges the new study results are statistically significant, but points out that the study lasted only two years. "Long-term treatment has to be tailored for each individual patient," Rosenberg says. "I don't think you can say that long-term treatment with the regular dose will be effective for every patient."
On one point, Rosenberg and Kearon are in complete agreement: Patients with the condition should get long-term warfarin treatment. Some physicians stop the treatment several months after a first clot occurs, but "warfarin treatment is without doubt essential to reduce the incidence of return of blood clots," Rosenberg says.
"Patients often do not stay on warfarin for the longer term," Kearon says. "This study shows that after six months, the benefit continued and the risk was low."
More information
You can learn about deep-vein thrombosis from the National Library of Medicine or the American Heart Association.
