After a "mini-stroke" a person is at twice the risk of suffering a heart attack as the general population, according to new research from the Mayo Clinic in the US that was published in the journal Stroke this week.

Senior investigator of the study, Dr Robert D. Brown Jr, who is chair of the neurology department at the Mayo Clinic in Rochester, Minnesota, said doctors should be aware of the increased risk of heart attack after mini-stroke or transient-ischemic attack (TIA), just as they are about the increased risk of stroke:

"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," he urged.

Brown and colleagues also found that the risk of heart attack after TIA was much higher for those under 60 years of age, as much as 15 times higher than the general population.

A TIA or mini-stroke is when a clot in a blood vessel temporarily stops blood flow to the brain. The symptoms are similar to a stroke but last only a few minutes or hours at the most, and they don't cause long term disability. However, a TIA usually signals a higher risk of having a larger stroker later.

A heart attack or myocardial infarction (MI) happens when blood and oxygen can't get to the heart muscle, mostly because of a clot in a coronary artery which in turn is usually due to coronary-artery disease, where plaque builds up on the inside of the blood vessel walls.

Brown and colleagues carried out the study because, although we know that coronary artery disease is a leading cause of death after TIA, we don't have reliable estimates of the risks of MI after TIA.

By cross-referencing records from the Rochester Epidemiology Project for TIA (1985 to 1994) and MI (1979 to 2006) they found all community residents who had experienced MI and TIA.

This revealed 456 patients (average age 72, and 43% male) who were diagnosed with a TIA. Nearly two-thirds had high blood pressure, more than half were smokers, and three-quarters were on medication to prevent blood clots (eg aspirin). The average follow up was 10 years.

They compared these results to incidences of MI in the general population, taking into account factors like age, sex, and time of year, and then looked for links between clinical variables and the occurrence of MI after TIAs.

The results showed that:
  • Average annual incidence of MI after TIA was 0.95%.

  • The average length of time between a first TIA and an MI was 5 years.

  • The risk of having MI after TIA was double compared to the general population (Relative Risk RR was 2.09, with 95% confidence interval CI ranging from 1.52 to 2.81).

  • The risk was highest in those under 60 years of age (RR 15.1; 95% CI from 4.11 to 38.6).

  • Increasing age (Hazard Ratio HR 1.51 per 10 years; 95% CI 1.14 to 2.01) was an independent risk factor for having MI after TIA.

  • Being male, and being on cholesterol-lowering drugs at time of TIA, were also independent risk factors for MI after TIA. (HR 2.19, 95% CI 1.18-4.05; HR 3.10, 95% CI 1.20-8.00, respectively).
The researchers also found that having a heart attack after a TIA was linked to a three times higher risk of dying over the 20 year period they studied, compared to not having a heart attack after TIA.

Brown and colleagues concluded that these findings will be "useful for identifying subgroups of patients with TIA at highest risk for subsequent MI".

They also showed the importance of screening TIA patients for signs of heart disease, they said.

Brown urged that we now use TIA not only to forewarn of higher risk of stroke, but also of heart attack.

The signs of stroke and TIA can come on very suddenly:
  • Feelings of numbness or weakness in the face, arm, leg (this often happens on side of the body).
  • Vision problems.
  • Speech problems, such as confusion and difficulty speaking or understanding others.
  • Feeling dizzy, losing balance or coordination, problems walking.
  • Unexplained, severe headache.
Any one of these signs warrants a 911 call for immediate medical, according to the Mayo Clinic, who funded the study.

"Incidence and Predictors of Myocardial Infarction After Transient Ischemic Attack: A Population-Based Study."
Joseph D. Burns, Alejandro A. Rabinstein, Veronique L. Roger, Latha G. Stead, Teresa J.H. Christianson, Jill M. Killian, and Robert D. Brown, Jr
Stroke, Published online before print 24 Mar 2011
DOI:10.1161/STROKEAHA.110.593723

Additional source: American Heart Association (24 Mar 2011).

Written by: Catharine Paddock, PhD