The role of delayed contrast-enhanced cardiac magnetic resonance in differentiating myocarditis from myocardial infarction

A number of different conditions can present with symptoms that mimics acute coronary syndrome (ACS). Even after performing coronary angiography, diagnosis can still be challenging. The aim of this study was to evaluate the utility of contrast-enhanced cardiac magnetic resonance (CMR) to differentiate between myocarditis and myocardial infarction (MI) in patients presenting with acute chest pain syndrome, elevated cardiac markers, and unobstructed coronary arteries. We studied 26 consecutive patients (mean age 32.4 +/- 11.3 years, 80.1% males) presenting with acute symptoms, elevated cardiac markers, unobstructed coronary arteries, and referred for Gadolinium-enhanced CMR examinations. Myocarditis was ascertained by the presence of myocardial edema and/or epicardial or scattered intra-myocardial late gadolinium enhancement (LGE). Myocardial infarction was diagnosed if there was territorial subendocardial LGE with variable degrees of transmural involvement. In patients with no LGE, the diagnosis was uncertain. Of 26 patients, 15 (57.7%) were initially diagnosed with ACS, the majority (8 patients, 53.3%) had LGE pattern of myocarditis, 4 (26.7%) had LGE pattern of MI. The remaining 11 patients had suspected myocarditis, 2 (18.2%) had LGE pattern of MI, and 7 (63.6%) had LGE pattern of myocarditis. Five (19.2%) patients had no LGE and diagnosis was unclear. Cardiac magnetic resonance helped to reclassify more than half of our patients (57.7%). We demonstrated that contrast-enhanced CMR allows differentiation between MI and myocarditis in patients presenting with possible ACS and unobstructed coronary arteries. This, in turn, helps with planning long-term therapeutic strategies and redefines the patient's future risk.