Warfarin could reduce risk for pulmonary
embolisms, deep-vein thrombosis
When 39-year-old David Bloom, an NBC news correspondent in Iraq, suddenly
died of a pulmonary embolism this spring, the life-threatening condition
made headlines. Pulmonary embolisms are most often related to deep-vein
thrombosis (DVT), essentially a blood clot in a leg vein. Sometimes,
all or part of the clot will break away from the vein wall and lodge
in an artery in the lungs. This is a pulmonary embolism. While traveling
with the Army in Iraq, Bloom reported sleeping with his knees propped
up. Staying immobile like this can cause circulation to slow. Sluggish
blood flow is one cause of clots. DVT can also be caused by blood that
has a greater-than-normal tendency to clot.
Although in Bloom’s case the condition was not detected in time,
pulmonary embolisms and DVT are treatable. Patients are often initially
prescribed heparin and then switched over to warfarin for 3 to 12 months.
Both of these drugs are anticoagulants; they help thin the blood by preventing
it from clotting. But a little clotting is necessary; to prevent uncontrollable
bleeding we need our blood to clot. Frequent blood tests help doctors
determine the amount of medication necessary for a safe balance of clotting
The balance becomes tricky once the typical treatment of heparin and
warfarin is complete. If anticoagulation therapy is stopped, the risk
of recurring DVT returns. But previous studies have shown extended use
of warfarin at full-dose leads to a risk of serious hemorrhaging.
To help solve this Catch-22, researchers started a trial of long-term,
low-intensity warfarin treatment in comparison to treatment with a placebo.
Over 500 patients were enrolled in the study; roughly half receiving
low-intensity warfarin and the other half receiving a placebo. Data from
this study, published in the New England Journal of Medicine, show low-intensity
warfarin treatment is superior to a placebo. The risk of recurring DVT
was 64% less in those patients who received warfarin, compared to those
who received the placebo. Even participants with an inherited tendency
to form blood clots experienced comparable reductions in risk. The number
of major bleeding episodes was similar between the two treatment groups.
These results were so positive that the study was halted early.
Preliminary results from a different study, however, somewhat contradict
these findings. Data from this study show treatment with low-intensity
warfarin is less effective than treatment with standard-intensity warfarin
for long-term prevention of recurring DVT.
To reconcile the differences between these two studies, a three-way comparison
of warfarin at full-dose, low-intensity, and no treatment is needed.
Until then, talk to your doctor about which treatment, if any, is right
July 2003 Update
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