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Report of group III: prevalence and prognosis

THE INCIDENCE of silent or unrecognized myocardial infarction is currently estimated to be about 25% of total infarctions. This is unquestionably a substantial underestimate since not included are those harboring acute silent myocardial infarctions who die suddenly, others who sustain silent non-Q wave infarctions producing a nonspecific electrocardiographic pattern, and still others in whom the electrocardiographic stigmata of infarction have regressed over time. The question of silent myocardial infarction should be investigated in individuals with isolated systolic hypertension, in blacks, and in women, groups for which virtually no information exists. Although it is generally recognized that many abnormal electrocardiographic stress tests do not provoke symptoms of myocardial ischemia, comparison of published studies is difficult because of the variety of stress tests employed, differences in diagnostic criteria and end points, and heterogeneity of the populations surveyed. It is generally agreed that exercise tests in young individuals free of risk factors such as arterial hypertension, hypercholesterolemia, heavy cigarette smoking, or a family history of precocious cardiovascular disease, in conformity with the predictions of Bayes' theorem, yield many false-positive responses. The predictive power of the electrocardiographic stress test could very likely be substantially improved by the application of multiple logistic regression analysis incorporating maximum heart rate achieved, duration of exercise, blood pressure response, magnitude and duration of repolarization abnormalities, and presence or absence of angina pectoris. Computer analysis of repolarization abnormalities has been claimed to substantially improve the sensitivity and specificity of the electrocardiographic stress test. Validation of these claims should be energetically pursued. It has been convincingly shown by radionuclide methods that repolarization abnormalities recorded during Holter monitoring coincide with myocardial ischemia. The prognostic significance of such information has not, however, been established, nor is there information on outcome after therapeutic intervention. Before wholesale Holter monitoring is undertaken it is recommended that surveillance studies be done on sufficiently large populations of both symptomatic and symptom-free individuals for significant periods of time.