Approximation of the Incidence of Myocarditis by Systematic Screening With Cardiac Magnetic Resonance Imaging

OBJECTIVES This study sought to obtain an approximation of the true incidence of myocarditis by systematic screening of patients at risk using cardiac magnetic resonance imaging (CMR) in a tertiary care center. BACKGROUND Underdiagnosis of myocarditis and resulting uncertainty about its incidence remain a clinical dilemma. The authors hypothesized that systematic screening of patients presenting with angina-like symptoms, elevated troponin T, and no significant coronary artery disease using CMR will provide an approximation of the true incidence of myocarditis. METHODS The authors performed a retrospective chart review of patients presenting with angina-like symptoms and elevated high-sensitivity troponin T (TnT-hs >= 14 ng/l) in 2015 and 2016. During the year 2015, only patients with elevated TnT-hs, no significant coronary artery disease, and moderate-to-high clinical likelihood of myocarditis underwent CMR. Starting in 2016, CMR was obtained in patients with similar presentation, but independent of clinical likelihood of myocarditis. RESULTS A total of 1,788 patients (74% male, age 69 +/- 14 years) qualified for our analysis. In 2015, 521 patients presented with angina-like symptoms and TnT-hs elevation. In 2016, the number increased to 1,267 patients. Although in the year 2015, a total of 4 of 88 (5%) CMRs were positive for myocarditis, the percentage of positive CMRs doubled (26 of 199; 13%; p = 0.03) in 2016. CONCLUSIONS A novel diagnostic screening algorithm led to a 6.3-fold increase of the incidence of myocarditis in our hospital. Furthermore, the percentage of CMRs positive for myocarditis doubled, supporting the diagnostic value of this method. Considering the potentially lethal adverse events of myocarditis if left untreated, we recommend a low threshold for the use of CMR in patients with angina-like symptoms and elevated TnT-hs after exclusion of coronary artery disease. (C) 2018 by the American College of Cardiology Foundation.