Mexican-American stroke survivors with atrial fibrillation at increased risk for second stroke

- Mexican-American stroke survivors with atrial fibrillation had more than double the risk for a second stroke compared to non-Hispanic white survivors with the disorder.

- Strokes were more severe among these Mexican-Americans than among non-Hispanic whites; however, researchers found no major differences in death rates between the two groups.

- Researchers said the findings could help physicians develop strategies to prevent recurrent stroke in Mexican-Americans.

Mexican-American stroke survivors with a heart rhythm disorder have more than twice the risk for another stroke compared to non-Hispanic whites, according to a study published in Stroke: Journal of the American Heart Association.

Mexican-Americans' recurrent strokes are also more likely to be severe, though they don't have a greater risk of death after stroke, researchers said.

Researchers compared 88 Mexican-American and 148 non-Hispanic white stroke survivors who had atrial fibrillation, a disorder in which the heart's upper chambers (called the atria) beat irregularly and don't pump blood effectively, possibly causing blood to pool within the atria  and blood clot formation in the heart.  

They found that the likelihood of suffering another stroke during the study follow-up period was more than double for Mexican-Americans than for non-Hispanic whites. Although stroke recurrence was higher and strokes were more severe among Mexican-Americans, death rates didn't differ between the two groups.

"Based on some of our prior research, we were not necessarily surprised by the higher recurrence risk in Mexican-Americans with atrial fibrillation, but the greater severity of recurrent strokes in Mexican-Americans was surprising," said Darin B. Zahuranec, M.D., study co-author and an assistant professor of neurology at the University of Michigan Cardiovascular Center in Ann Arbor.

Results are based on cases of ischemic stroke and transient ischemic attack from the Brain Attack Surveillance in Corpus Christi Project, a population-based stroke surveillance study. The data were collected between January 2000 and June 2008. Corpus Christi has a large Mexican-American population and is located along the Gulf coast of Texas.

The study also showed that Mexican-American patients were younger, less likely to have completed 12 years of education, more likely to have diabetes, and less likely to have a primary care physician.  Researchers found no ethnic differences between the two groups in the severity of the first stroke.

Nineteen Mexican-Americans and 14 non-Hispanic whites had at least one recurrent stroke over a median follow-up of 427.5 days; all but one event was an ischemic stroke (one Mexican-American patient experienced intracerebral hemorrhage).

One reason for the difference could be that the management of warfarin — a blood thinning drug — among Mexican-Americans may not be optimal, Zahuranec said. However, the study found no ethnic difference in the proportion of patients who were prescribed warfarin at hospital discharge.  They did not evaluate data looking at outpatient use of warfarin after hospital discharge which might have contributed to the increased risk of stroke in Mexican-Americans.

Atrial fibrillation affects approximately 2.2 million Americans; about 15 percent of strokes occur among individuals with atrial fibrillation.

SOURCE American Heart Association