Abstract 13153: Non-Rheumatic Streptococcal Myocarditis Manifesting as Acute Non-ST-Elevation Myocardial Infarction

Abstract

Case presentation: A 24-year-old healthy man presented with acute, constant, non-radiating, chest pain with pleuritic quality. Three days prior, he had developed fever, sore throat, cervical lymphadenopathy, and tachycardia. Amoxicillin was given for a positive rapid streptococcal test. He was afebrile and bradycardic at 50 bpm. Lab showed leukocytosis (WBC 20,000/μL, neutrophil 80%), elevated ESR 70 mm/hr, CRP 23 mg/dL, and rising hs-cTn from 800 to 1,700 ng/L. Anti-streptolysin O and anti-DNase-B were normal. Tests for adenovirus, EBV, CMV, and other respiratory viruses were negative. Initial EKG showed sinus bradycardia with ST depression and T-wave inversion in V1-V2 and III. CXR and echo were unremarkable. He received intravenous penicillin G and indomethacin. Chest pain resolved on the following day. Repeat EKG showed resolution of bradycardia, ST depression, and T-wave inversion in V2. Indomethacin, colchicine, and amoxicillin were given upon discharge. Discussion: In contrast to acute rheumatic fever (ARF), a condition caused by molecular mimicry leading to cross-reactive humoral and cellular immune responses between cardiac and Streptococcus pyogenes antigens, the pathophysiology of non-rheumatic streptococcal myocarditis is presumably toxin-mediated. Although the revised Jones criteria were fulfilled in our patient, the temporal relationship between pharyngitis and the onset of carditis must be taken into account to distinguish these two entities. Concurrent myocarditis and pharyngitis suggest non-rheumatic streptococcal myocarditis, as opposed to a delayed presentation in ARF. Latency from pharyngitis to chest pain was reportedly around 3 days. The absence of valvular heart disease and streptococcal antibodies, such as anti-streptolysin O and anti-DNase B, are a clue to diagnosis. A recent case-series also suggested male-predominance. There has been an increase in a diagnosis of non-rheumatic streptococcal myocarditis due to a widespread use of diagnostic modalities such as MRI. Clinicians should consider this condition in a differential diagnosis of acute coronary syndrome, particularly in any young individuals with chest pain, elevated cardiac biomarkers, EKG changes, and simultaneous streptococcal pharyngitis.