Significance of abnormal Q waves in the electrocardiograms of adults less than 40 years old.

BACKGROUND: Abnormal Q waves (AQW) in the electrocardiogram are commonly ascribed to underlying myocardial infarction (MI). As an imperfectly specific sign of MI, the usefulness of AQW in identifying MI depends on its incidence in the population studied.

METHODS: Eighty-two subjects under 40 years of age with AQW were compared with 82 subjects from the same institution aged > or =40 years with similar AQW to determine the presence or absence of cardiac disease or MI.

RESULTS: Cardiac disease was present in 90.2% and 92.7% of the younger and older subjects, respectively, whereas MI was present in only 15.9% of younger subjects and in 68.3% of older subjects. Etiologies of cardiac disease differed between younger and older subjects. Some types of AQW were more useful than others in ruling MI in or out.

CONCLUSIONS: AQW were a strong indicator of organic heart disease in both adult age groups, but their utility to indicate MI was age-dependent. In the population studied, MI was present in only a small minority of subjects under 40 years of age with AQW, but was usually present in older subjects with similar AQW.