Acute Myocarditis in Emergency Medicine

Emergency doctors provide primary care to many patients with an acute-onset condition in the emergency room (ER) every day. We occasionally must address circulatory failure in patients that ranges from “acutely developing” to “severe.” Usually, it is not difficult to diagnose or to choose the proper therapeutic procedures, because most of these cases are caused by heart diseases, such as ischemic heart disease or an arrhythmia. However, in some cases the causes of circulatory failure cannot be determined immediately. It is known that cardiomyopathies account for some of those undiagnosed cases. Classically, cardiomyopathies have been regarded as idiopathic myocardial diseases because of the difficulty of detecting their etiology or the mechanisms causing the problem. Recent developments in biochemical technology have provided the option of approaching these unknown mechanisms using genetic analyses (Richardson et al., 1996). Cardiomyopathies are presently classified into several groups, defined by the cause, tissue type, and clinical course. In 2006, a committee of the American Heart Association (AHA) advocated new criteria for cardiomyopathies. With those criteria, primary cardiomyopathies are classified into a genetic type, a mixed type, and an acquired type (Maron et al., 2006). We encounter several types of cardiomyopathy in the ER. Immediate adequate primary treatment of these cases must be prudent because circulatory insufficiency can rapidly progress to cardiac arrest. In most cases, myocarditis is caused by an inflammatory response and is classified as an acquired type of primary cardiomyopathy. It is also categorized as either acute or chronic. The comprehensive concept of chronic myocarditis has not yet been established because cases of chronic myocarditis have not been sufficiently reported. For most cases of chronic myocarditis, the causes and developmental mechanisms remain unclear. We have only practical guidelines for treating chronic myocarditis in Japan (JCS, 1996). These patients usually have long-term therapeutic histories. Therefore, the patients’ own doctors who are familiar with their clinical histories should be responsible for treatment in the ER. On the other hand, most cases of acute myocarditis are of sudden onset, and severe cases are taken to the ER by the emergency medical service. Doctors in the ER must then be responsible for the primary treatment of these patients. Because there is the risk of sudden development of circulatory insufficiency with acute myocarditis, immediate and adequate initial treatment is necessary for survival.