BACKGROUND:Myocarditis is a recognized but rare complication of smallpox immunization. It typically presents within 30 days of immunization and on initial presentation shares many characteristics with acute coronary syndrome. Electrocardiogram findings, elevated cardiac enzymes, and undifferentiated chest pain require immediate implementation of therapy directed towards an acute coronary syndrome. In an austere environment, access to advanced care may be limited.

OBJECTIVES:Smallpox vaccine-mediated myocarditis may present, typically within 30 days of immunization, in such a fashion that it is impossible to distinguish from acute myocardial infarction. The purpose of this article is to alert the clinician to this problem and to provide information to assist in making a suitable diagnosis and disposition in the absence of an absolute diagnosis.

CASE REPORT:We present a case of smallpox vaccine-associated myocarditis in an American serviceman deployed in Iraq, and review the literature to determine management of these cases in an emergency setting.

CONCLUSIONS:This case serves to increase awareness of the association of vaccine-mediated myocarditis in the month after immunization, and the fact that it may present similar to infarction. If the clinical probability of myocarditis is greater than infarction, this will lead the clinician to different treatment modalities.

The development of vaccines ushered in the most profound advancement in 20th century medicine, and have widely been regarded as the one of the most important scientific discovery in the history of mankind. However, vaccines are not without risk; reactions can range from injection site reactions to life-threatening anaphylaxis. Among the more serious vaccine-related sequela is myocarditis. Although myocarditis has been reported following many different vaccines, the smallpox vaccine has the strongest association. We report a case of a 36-year-old active duty service member presenting with progressive dyspnoea, substernal chest pain and lower extremity swelling 5 weeks after receiving the vaccinia vaccination. The aetiology of his acute decompensated heart failure was determined to be from myocarditis. Although the majority of cases of myocarditis resolve completely, some patients develop chronic heart failure and even death. Vaccine-associated myocarditis should always be on the differential for patients that exhibit cardiopulmonary symptoms after recent vaccinations.