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Dangerous Duo: Unrecognized MI and Angina

Unrecognized myocardial infarction is most often diagnosed when new Q waves are detected on ECG in a patient who has had no symptoms of MI. To determine the clinical importance of unrecognized MI, these authors studied 9141 men who were part of a population-based cohort study in Reykjavik, Iceland.

Unrecognized MI was common, accounting for a third of all MIs and reaching a prevalence of greater than 5% in subjects aged 75 to 79. The incidence was very low in patients under 40, peaked at age 65 (at more than 300 per 100,000 person-years), and declined thereafter. Risk factors for unrecognized MI were very similar to those for recognized MI except that angina pectoris was more common in patients with recognized MI (58% vs. 34%, P<0.001).

However, by year 15, mortality from coronary heart disease and from all causes was about the same in subjects with unrecognized MI as in those with recognized MI (at 10 years, 51% and 38%, respectively; at 15 years, 55% and 52%). Relative risk of mortality was especially high (16.9) in patients with both unrecognized MI and angina pectoris (compared to 4.6 in patients with unrecognized MI and no angina).

Comment: This is a very important study. Unrecognized MI is common and is associated with a poor prognosis. Although angina is more often associated with recognized MI, when angina is combined with unrecognized MI the prognosis is especially poor. The actual importance of unrecognized MI may be underestimated, given the well-described tendency of Q waves to disappear over time. From a clinical viewpoint, this study supports the use of routine ECGs in patients with angina. Furthermore, strong consideration should be given to screening asymptomatic subjects for unrecognized MI when they have a high profile of risk factors for coronary disease.

— MS Lauer

Published in Journal Watch Cardiology March 1, 1995

Citation(s):

Sigurdsson E et al. Unrecognized myocardial infarction: epidemiology, clinical characteristics, and the prognostic role of angina pectoris: the Reykjavik Study. Ann Intern Med 1995 Jan 15 122 96-102.

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