Case Presentation: A 50 year old male with no past medical history presented with severe chest pain that progressively worsened over 2 days. His chest pain was described as left sided, non-radiating, and constant. He reported sore throat, headaches, and subjective fevers for the past 5 days. The patient also reported multiple family members received antibiotics for sore throat infection within the prior weeks. Vitals and examination of neck, oropharynx, heart, lungs, and extremities were normal. Electrocardiogram showed normal sinus rhythm with ST-segment elevations in II, III, aVF, and V4-V6, as well as ST-segment depressions in aVR and V2-3 concerning for anterolateral ischemia. Point-of-care ultrasound showed inferior wall motion abnormalities and moderate mitral regurgitation. Laboratory results were significant for marked troponin elevation to 48ng/mL, AST 153 U/L, ALT 66U/L, HDL 29mg/dL, and LDL 140mg/dL. Emergent cardiac catheterization showed non-obstructive coronary artery disease. Transthoracic echocardiogram showed moderately reduced left ventricular systolic function with ejection fraction (EF) of 40% and akinesis of the lateral and anteroseptal walls, as well as hypokinesis of the basal and mid inferior walls. Workup for alternative etiologies included elevated C-reactive protein to 195mg/dL and sedimentation rate to 48mm/hr, as well as positive throat culture for group A Streptococcus pyogenes. The patient was diagnosed with acute nonrheumatic streptococcal myocarditis and started on amoxicillin, lisinopril, carvedilol, aspirin, and atorvastatin. Follow-up echocardiogram 3-months post-admission showed normalization of his cardiac function.

Discussion: Myocarditis can be produced by a variety of different causes, many of which are infectious, specifically viral. The clinical manifestations are highly variable, ranging from subclinical disease to chest pain, heart failure, cardiogenic shock, arrhythmias, and sudden death. Acute nonrheumatic streptococcal myocarditis (ANSM) has been identified as an independent entity with different symptoms, time course, and pathophysiology from acute rheumatic fever. ANSM mimics acute coronary syndrome on presentation and should be considered in the differential of young adults presenting with chest pain and history of a preceding sore throat. This disease entity usually affects adults younger than age 35 and is caused by Group A or G streptococci. ANMS responds favorably to conventional antibiotic therapy and has excellent long-term clinical prognosis when compared to long-term effects of acute rheumatic fever. On a case series of 9 patients with ANMS treated with antibiotics, 3 out of 3 patients with depressed EF and wall motion abnormalities at diagnosis had no significant abnormalities on follow-up imaging.

Conclusions: Our case demonstrates the importance of considering ANSM in patients evaluated for acute chest pain and sore throat, even when out of the expected age range. Unlike many forms of viral myocarditis, ANSM is associated with an excellent clinical prognosis and favorable response to antibiotic therapy.