When Myocarditis Masquerades as ST-Elevation Myocardial Infarction: A Case of Coxsackie B-induced Acute Heart Failure With Rapid Recovery

Coxsackie B viral myocarditis is a rare but important mimic of ST-elevation myocardial infarction (STEMI) and can present with fulminant heart failure and shock. Swift recognition is vital, as supportive therapy alone can lead to rapid recovery. A 69-year-old man with a history of only hypertension presented with dyspnea and fever, despite outpatient antibiotics for pneumonia. On arrival, he was hypotensive and in severe respiratory distress, requiring intubation and norepinephrine. EKG revealed anterolateral ST-segment elevations, and echocardiography showed profoundly depressed left ventricular function (ejection fraction: 10-15%) with regional wall motion abnormalities. Troponin rose to 1,700 ng/L and leukocytes to 17,900/µL. Emergent angiography demonstrated non-obstructive coronaries, raising concern for myocarditis, sepsis-induced cardiomyopathy, or Takotsubo syndrome. CT pulmonary angiography showed bilateral lung infiltrates. Given instability, cardiac MRI and biopsy were deferred. Viral serology was pursued and returned positive for Coxsackie B1-B6. Treatment continued with empiric antibiotics, vasopressors, and intra-aortic balloon pump support. By hospital day four, there was striking clinical recovery, with repeat echocardiography confirming normalization of ventricular function, eliminating the indication for defibrillator therapy. STEMI presentations with non-obstructive coronaries should prompt consideration of alternative etiologies. When cardiac MRI or biopsy is not feasible, Coxsackie B myocarditis can be identified serologically. In these cases, transient circulatory support may suffice given the potential for rapid recovery. Early follow-up echocardiography is crucial to confirm recovery and prevent unnecessary wearable or implantable defibrillator placement. Coxsackie B myocarditis can mimic STEMI with cardiogenic shock. Serology provides a practical diagnostic pathway when MRI and biopsy are not possible. Supportive management may enable rapid reversal of ventricular dysfunction, underscoring the role of early follow-up echocardiography in guiding device therapy decisions.