Prevalence, clinical features, and acute course of atypical myocardial infarction.

Ninety-four consecutive patients (60 men and 34 women; mean age 68.5 +/- 11.5 years) with acute myocardial infarction (MI) were investigated retrospectively, in order to evaluate the prevalence, clinical features, and short-term course of the atypical forms (symptoms other than chest pain). An atypical MI was found in 30 patients, with a prevalence of 32% (95% confidence limits 27-36%). It was most prevalent in women above sixty-five years old (P < 0.05). Abdominal pain, paroxysmal dyspnea, and pulmonary edema were the most frequent symptoms (33%, 17%, 13%, respectively). No differences were observed between typical and atypical MI in regard to risk factors (hypercholesterolemia, arterial hypertension, diabetes mellitus, cigarette smoking) and history of MI, cerebrovascular disease, peripheral vascular disease, or chronic lung disease. Significantly fewer patients with atypical MI had a history of angina pectoris (P < 0.05). No differences were observed in regard to previous medication, except for antiarrhythmic drugs, more often used by atypical patients (P < 0.05). Location and severity of MI (as judged by ECG and peak levels of creatine kinase in the serum) were similar in both subgroups, as were the complications (34% typical and 50% atypical) and death rate (12.5% and 16.7%, respectively). In conclusion, atypical MI is not less severe than typical. This emphasizes the need for a high suspicion index in many different clinical settings, but particularly (although not exclusively) in elderly females, in the presence of abdominal pain or otherwise unexplained paroxysmal dyspnea.