TIA Signals Increased Risk of MI

Patients who have a transient ischemic attack (TIA) have a higher risk of subsequent myocardial infarction (MI) than the general population, and this excess risk continues over time. The risk of MI in those with TIA is 1% per year, which is approximately double the risk of MI in the general population, noted Robert Brown Jr, MD, professor and chair of neurology, Mayo Clinic, Rochester, Minnesota.

Community residents with MI after incident TIA were identified using the database of the Rochester Epidemiology Project, which is a medical records-linkage system that documents the care delivered to residents of Rochester and Olmsted County, Minnesota. The incidence rate of MI after TIA was compared with the age-, sex-, and period-specific incidence of MI in the general population of Olmsted County. Between 1985 and 1994, 388 residents had a TIA without a history of MI. Follow-up data were available for all but 1 patient after 5 years. The median duration of follow-up was 10.2 years.

Of the patients included in the analysis, 44 had an MI after TIA, yielding an average incidence of MI of 0.95%. The risk of MI after TIA remained fairly constant over time. The age-, sex-, and period-specific relative risk for incident MI in those with a TIA compared with that of the general population was 2.09. This relative risk was most pronounced in patients younger than 60 years, who had a relative risk of 15.1. In a multivariate analysis, independent predictors of MI after TIA were increasing age, male sex, and the use of lipidlowering therapy. After adjustment for factors associated with mortality in patients with TIA, MI was a significant independent predictor of death after TIA, tripling the risk.

These findings underscore the importance of coronary artery disease (CAD) prevention in patients with a TIA, said Dr Brown. “The key point from this study is not to remain so focused on the neurological implications that you ignore the systemic implications of the TIA,” he said. “Once you’ve evaluated for the mechanism of the TIA and you’ve implemented secondary prevention strategies for stroke, step back and ask if the patient has a risk profile placing him at high risk of MI. If so, consider if you should be doing some kind of noninvasive study of the coronary arteries, either a stress test or an imaging study...to screen for evidence of CAD. If you find evidence of CAD, then you can prophylactically treat as well. Here’s a way we may be able to prevent sudden MIs,” he noted.

The etiology of the TIA was not a predictor of future MI, which suggests that all patients with TIA, regardless of the specific etiology, should have a CAD risk factor assessment. The use of lipid-lowering therapy as a predictor of MI is likely a surrogate for systemic atherosclerosis, noted Dr Brown. “These patients likely had multisystem disease and that is why they were on lipid-lowering therapy to start with,” he said.