Comparison of clinical presentation of acute myocarditis following smallpox vaccination to acute coronary syndromes in patients <40 years of age.

Smallpox vaccine-associated myopericarditis may have a similar presentation to acute coronary syndrome (ACS). The clinical records of 78 young patients (<40 years of age) presenting with ACS (n = 16) or myocarditis after smallpox vaccination (n = 62) were reviewed. Comparisons were made among clinical presentation, cardiac enzymes, echocardiographic findings, and electrocardiographic changes. The presence of cardiac risk factors or focal wall motion abnormalities on echocardiography were associated with a diagnosis of ACS. There was a trend toward earlier elevation of troponin-I and creatine kinase in patients with myocarditis compared with ACS.