Stroke: MI incidence doubles after TIA

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After a transient ischemic attack (TIA), the annual incidence of MI is almost 1 percent, double that of the general population and risk is higher in patients aged 60 and under, according to a report published in the March 28 issue of Stroke.

“Coronary artery disease (CAD) is the leading cause of death after TIA,” the authors wrote. In fact, previous studies have reported that CAD may be the culprit of almost 24 to 62 percent of deaths in the first five to 10 years after TIA. “Reliable estimates of the risk of MI after TIA, however, are lacking,” the authors wrote.

To bulk up these sparse data, Joseph D. Burns Jr., MD, of the Mayo Clinic and Mayo Foundation in Rochester, Minn., and colleagues used the Rochester Epidemiology Project for TIA (1985-1994) and MI (1979-2006) to identify patients with incidence of MI after TIA.

The authors compared age, sex and period-specific MI incidences in the general public.

Burns and colleagues reported that there were 456 incidents of TIA between 1985 and 1994 and the average annual incidence of MI and TIA was 0.95 percent.

Of the patients who experienced TIA, 41 percent were male, 62 percent had hypertension, 11 percent had diabetes, 55 percent were current or previous smokers and the mean age at the time of a TIA was 71.

Of these patients, 15 percent had a history of MI prior to a TIA and of those, 12 percent experienced another MI post-TIA. In addition, the relative risk for incident MI in the TIA cohort compared with the general population was 2.09. The median time from index TIA to index MI was 4.6 years.

These numbers were highest in patients under the age of 60 and the authors noted that increasing age, male sex and the use of lipid-lowering therapy at the time of TIA were independent risk factors for MI after TIA.

In a univariate analysis, the researchers reported that patients who suffered an MI after a TIA were three-times more likely to die during follow-up compared with patients who didn’t experience an MI post-TIA.

Due to the finding that having MI increased the risk of death by three-fold in patients with TIA, the authors said that a bigger focus should surround primary prevention of CAD in TIA patients, even if symptoms are absent. In addition, Burns et al said that screening for CAD in some TIA patients could be useful.

"Physicians and other healthcare providers should be mindful of the increased risk for heart attack after TIA, just as they are about the increased occurrence of stroke," the authors concluded. "In the same way that we evaluate the patient to determine the cause of TIA and implement strategies to reduce the occurrence of stroke after a TIA, we should step back and consider whether a stress test or some other screening study for coronary artery disease should also be performed after a TIA, in an attempt to lessen the occurrence of heart attack."