High Amino Acid Levels Combined With Genetic Disorder Increases Relative Risk Of Vein Clots

DALLAS, March 31 -- Men with high blood levels of an amino acid called homocysteine and a hereditary blood clotting disorder called Factor V Leiden have a far greater relative risk of forming potentially life-threatening blood clots in leg veins that can travel to the lungs than men who have neither or either condition, Boston researchers report in the current issue of the American Heart Association journal Circulation. Such clots can cause medical conditions known as deep venous thromboses, characterized by blood-clots in leg veins, and pulmonary emboli, a potentially fatal condition when a blood clot travels to a lung artery.

About one in every 400 healthy individuals is likely to be affected by high levels of homocysteine and Factor V Leiden, the authors of the study say. But, they add, the absolute risk of developing blood clots associated with the two conditions remains low, so the value of long-term treatment with drugs that keep clots from forming needs to be evaluated in future studies.

The scientists also suggest that people with Factor V Leiden disorder be screened to determine their blood levels of homocysteine.

Previous studies have suggested that folic acid, found in oranges, bananas, beans and broccoli, may protect against heart and blood vessel disease by lowering blood levels of homocysteine. The data in this study "raise the possibility that simple dietary interventions might be adequate to reduce long-term risks in some patients," the researchers write.

Paul Ridker, M.D., of Brigham and Women's Hospital, and his colleagues determined homocysteine levels and the presence or absence of Factor V Leiden in 145 initially healthy men participating in the Physicians' Health Study who later developed these wandering blood clots, and in 646 men who did not develop such blood clots during the 10-year follow-up.

Normally, men have homocysteine levels of 10-11 micromoles per liter of blood. In this study, men with homocysteine levels of at least 17.25 micromoles per liter were at least three times more likely than men with normal homocysteine levels to develop a venous blood clot that was not attributed to any other medical condition. Men with high homocysteine levels who also had Factor V Leiden had a 20-fold increased risk of developing these blood clots.

Co-authors of the study are: Charles H. Hennekens, M.D., Dr.P.H.; Jacob Selhub, Ph.D.; Joseph P. Miletich, M.D.; M. Rene Malinow, M.D.; and Meir J. Stampfer, M.D.

Circulation is one of five scientific journals published by the Dallas-based AHA.

Media advisory: Dr. Ridker can be reached in Boston by calling 617-278-0869. Reporters may call (214) 706-1173 for a copy of the journal report. (Please do not publish telephone numbers.)

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