Cardiac Magnetic Resonance Assessment of Myocarditis

Symptoms consistent with myocarditis are a frequent cause of medical visits, especially in young and middleaged patients. Moreover, myocarditis was found to be the most frequent disease in patients with acute coronary syndrome yet normal coronary arteries. 1 Although many causes have been identified, acute cases are mostly because of myocardial involvement in systemic viral disease. 2,3 During the first days of viral myocarditis, there is direct cardiomyocyte injury, accompanied by edema, necrosis, and, depending on its spatial extent, regional, or even global contractile dysfunction. The tissue is typically cleared from the virus within 5 days; yet, reactive inflammation (clean-up) may last for several weeks. In uncomplicated disease, there is full tissue and functional recovery within 3 to 4 weeks, whereas more severe disease necrosis results in myocardial scarring. Prolonged autoimmune response or virus persistence may lead to chronic inflammation and is considered a frequent cause of dilated cardiomyopathy. 3 Symptoms are not specific; patients may present with chest pain, fatigue, dyspnea, or arrhythmia. ECG findings may include AV block, ventricular or supraventricular arrhythmia, and ST changes, including severe elevation mimicking acute myocardial infarction. Except for more severe cases, echocardiography typically shows normal systolic wall motion or just mild regional dysfunction. Serological markers for cardiomyocyte injury, such as troponin, may be normal. Because of the nonspecificity of its symptoms, signs and test findings, myocarditis is often diagnosed by exclusion of other cardiac diseases. The specific identification of an active nonischemic inflammatory process, therefore, is a clinical challenge, especially in patients presenting with acute chest pain and heart failure. Invasive endomyocardial biopsy is only recommended in patients with evidence for heart failure in combination with acute disease (<2 weeks, class I) or left ventricular dilatation (<3 months, class I) or specific other cases of heart failure (class IIa). 4 While nuclear imaging methods have not been proven useful, echocardiography and contrast-enhanced cardiovascular magnetic resonance (CMR) are standard imaging tools in patients with suspected myocarditis. Figures 1 to 3 present results of a 31-year-old male patient presenting with acute chest pain and a normal physical examination. Although ECG, coronary angiography, and echocardiography were either normal or nonspecific, CMR provided strong evidence for myocardial edema, hyperemia, and necrosis and thus allowed for establishing the diagnosis of acute myocarditis.