Chest Pain in a 17-Year-Old

A 17-year-old, previously healthy, Caucasian male reports one week of flu-like symptoms consisting of fevers, chills, and myalgias. On day 7 of his symptoms, he develops pleuritic chest pain and pressure and presents to the emergency department with the following electrocardiogram (Figure 1). His serial laboratory data reveals peak values of: troponin T 1.30ng/mL (normal 0.000-0.029ng/mL), CK 1000U/L (normal 30-220 U/L), CK-MB 87.6ng/mL (normal 30-220 U/L), CRP 3.3mg/dL (normal 0.0-1.0mg/dL), and WSR 9mm/hr (normal 0-10mm/hr). His creatinine and complete blood count (CBC) are normal. The patient undergoes transthoracic echocardiography which reveals normal biventricular function with a left ventricular ejection fraction (LVEF) of 60% and no evidence of pericardial effusion or valvular abnormalities. Left ventricular myocardial strain analysis is also normal. The same day, he undergoes a cardiac MRI (representative image in Figure 2), which suggests a lower LVEF than echo (52%), and reveals abnormal delayed enhancement imaging.

Figure 1: Presenting EKG

Figure 1

Figure 2: Cardiac MRI: four chamber delayed enhancement image

Figure 2

What is the most likely diagnosis?

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