warfarinfo

Warfarin Institute of America

DEDICATED TO YOUR HEALTH SINCE 2000

HOW LONG SHOULD WARFARIN BE CONTINUED AFTER I HAVE HAD ONE BLOOD CLOT IN MY LEG?

The question of how long to continue warfarin after a person has one blood clot, of unknown origin, in their leg has been perplexing for as long as warfarin has been on the market. In my opinion anything less than six months is too short. There is a high risk of recurrence if the warfarin is stopped sooner than that. The longer that warfarin is continued, the less risk there is of recurrence if it is stopped. Now there has been a study published that shows that it is probably possible to run a test that quantifies the risk of recurrence.

PLEASE NOTE: THE FOLLOWING STUDY EXCLUDED PEOPLE WHO HAD BLOOD CLOTS CAUSED BY SURGERY, TRAUMA, BEEN PREGNANT WITHIN THE PAST THREE MONTHS, DEFICIENCY OF A NATURAL COAGULATION INHIBITOR, LUPUS ANTICOAGULANT, CANCER OR WHO WERE ON LONG-TERM ANTICOAGULATION.

So who was included? This applies only to people who have had one blood clot that was of an unexplained origin. Please note this distinction very carefully – only people who had one blood clot and that clot was of an unknown origin should use this information.

This article is based on a study done by Dr. Sabine Eichinger and associates in Vienna, Austria. (JAMA 2003;290:1071-1074) They studied patients who had taken anticoagulants for at least three months. When the anticoagulant was stopped, the people were then enrolled in this study. The study measured levels from a test called the D-Dimer level. D-Dimer is a substance released into the blood when a clot is present. The amount of D-Dimer in the blood AFTER people stopped anticoagulation was found to be a good predictor of the chance of another blood clot.

People who had a D-Dimer level of less than 250 had about an 8% chance of having another clot in the next two years. People who had a D-Dimer level higher than 250 had about double this risk of having another clot in the next two years.

The important things that I think that you should consider about this study are:

The anticoagulant had to be stopped

There was at least an 8% chance of recurrence in the next two years. Each individual and their physician will have to make a determination as to whether or not this risk rate is acceptable to them.

There were many exclusions to the study. Only about 1/3 of people who have blood clots fall into the category of first clot with an unexplained origin.

If you are one of the group of people who fall into this category, you have a valuable new set of evidence to help you determine whether or not you need to continue anticoagulation.

There has also been a study published showing that many people who must continue on warfarin for a blood clot in the leg (DVT) will do well with a less intense warfarin therapy. This study by Ridker et al (New Engl J Med 2003;348:1425-34) called the PREVENT Trial followed people who had taken warfarin for about six months, keeping their INR between 2.0 and 3.0. The range for the INR was then lowered to 1.5 to 2.0 and the warfarin dose decreased appropriately. They followed 508 people for an average of about two years. They concluded that this was highly effective in preventing recurrences.

I have spoken with one of the co-authors of this study (Dr. Moll) and he says that he is keeping everyone except those who absolutely would not tolerate another clot on this low-intensity therapy.

Please also look at a similar discussion from a different perspective.

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Last updated May 11, 2006