Gene Ups Risk for Those on Blood-Thinner Plavix

MONDAY, Dec. 22 (HealthDay News) -- A gene variation can make younger heart attack patients more prone to another heart attack, death or other heart problems if they receive the anti-clotting drug Plavix, a trio of new studies finds.

One study is published in the Dec. 23 online edition of The Lancet, while two more studies with similar results will appear in the Jan. 22 issue of the New England Journal of Medicine.

Plavix plus low-dose aspirin are often used to prevent blood vessels from clogging after a heart attack or after patients receive an artery-opening stent.

But some patients do not do well on Plavix (clopidogrel). Until now, the reasons for that variance have been unclear.

Plavix "targets a very important receptor on platelets, but people vary substantially in how good an anti-clotting effect they have" from the drug, explained Dr. Robert F. Storey, from the Cardiovascular Research Unit at the University of Sheffield School of Medicine in the United Kingdom. He is also the author of an accompanying comment in The Lancet.

"The variation in response is partly due to genetics, but there are other factors such as age which influence the response," Storey said.

For the study in The Lancet, a team led by Dr. Gilles Montalescot, from the Hopital Pitie-Salpetriere in Paris, collected data on 259 patients aged 45 and younger who suffered a first heart attack and were given Plavix.

Among these patients, 28 percent carried a gene variation called CYP2C19*2. This variation is common among the western population and even more common in Asia, the researchers noted.

During an average of a year of follow-up, patients with the gene variation were more than three-and-a-half times more likely to die, have another heart attack or require additional cardiac treatment compared to those without the variation, the researchers found.

In addition, patients with CYP2C19*2 were six times more likely to have a blockage in a stent they had received after a heart attack.

Moreover, the variation continued to cause heart problems up to eight years after treatment with Plavix. In fact, patients with the variation were four times more likely to suffer additional heart problems after receiving the blood thinner.

Similar results were found in the two New England Journal of Medicine studies, released early by the journal on Monday. In one study, a French team led by Dr. Laurent Becquemont of the University of Paris found that carriers of the CYP2C19 variant had a higher rate of heart events when treated with Plavix after heart attack. A third study, led by Dr. Marc Sabatine of Harvard Medical School in Boston, found that gene carriers with acute coronary syndromes who were taking Plavix had a 53 percent higher risk of death from cardiovascular causes, heart attack or stroke compared to those without the CYP2C19 variant.