Prevalence and Prognosis of Unrecognized Myocardial Infarction Determined by Cardiac Magnetic Resonance in Older Adults

Study Questions:

What is the relative prevalence and prognostic significance of unrecognized myocardial infarction (UMI), identified by magnetic resonance imaging (MRI) or electrocardiogram (ECG), relative to recognized myocardial infarction (RMI)?

Methods:

The study (ICELAND MI) examined 936 individuals in a substudy of the AGES-Reykjavik Study, a randomly selected cohort born between 1907 and 1935, with follow-up since 1967. Individuals with documented history of MI were defined as RMI, whereas UMI represented patients with MI by standard ECG criteria and/or late gadolinium enhancement in a coronary distribution by MRI. The prevalence and prognosis of UMI by ECG or MRI were compared relative to RMI.

Results:

Median age was 76 years, 52% were female, and 10% had RMI. Of 936 patients, 17% and 5% had UMI identified by MRI and ECG, respectively (p < 0.001). Over a median follow-up of 6.4 years, mortality was higher in those with RMI (hazard ratio [HR], 2.2; 95% confidence interval [CI], 1.3-2.6) or UMI by MRI (HR, 1.8; 95% CI, 1.3-2.6) as compared to those without MI, with no significant difference in mortality between RMI and UMI by MRI (p = 0.40). In contrast, UMI by ECG was not associated with higher mortality (HR, 0.9; 95% CI, 0.5-1.9). After adjusting for risk factors and RMI, UMI by MRI was independently associated with increased mortality (HR, 1.5; 95% CI, 1.02-2.1), whereas UMI by ECG was not (HR, 0.9; 95% CI, 0.5-1.7).

Conclusions:

In a community cohort, UMI by MRI was observed more frequently than UMI by ECG or RMI. UMI by MRI, but not by ECG, was associated with an increased risk of mortality.

Perspective:

This community cohort study demonstrated that UMI by MRI was more common than RMI, and identified more than triple the number of UMI compared to ECG testing. UMI may be more common than previously realized, and we may be significantly underestimating the overall burden of MI. In addition, individuals with UMI by MRI (but not by ECG) were observed to have an increased mortality risk that was comparable to those with RMI, suggesting that current approaches miss a large population of patients at high risk of future mortality. Whether identification of UMI by MRI would improve patient outcomes or be cost-effective is not known.

Clinical Topics: Noninvasive Imaging, Magnetic Resonance Imaging

Keywords: Prevalence, Prognosis, Myocardial Infarction, Follow-Up Studies, Gadolinium, Cardiovascular Diseases, Risk Factors, Confidence Intervals, Electrocardiography, Magnetic Resonance Spectroscopy, Magnetic Resonance Imaging


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