A Case of Early-Stage Acute Myocarditis in a Child Detected by Focused Cardiac Ultrasound.

Myocarditis in children is a life-threatening condition requiring prompt diagnosis and intervention. Its nonspecific signs and symptoms often mimic those of common viral illnesses and pose significant diagnostic challenges. Focused cardiac ultrasound (FoCUS) has recently been used for cardiac assessment in paediatric emergency care; however, reports on its use in diagnosing myocarditis are limited. We herein report a case of early-stage acute myocarditis detected by FoCUS. A previously healthy two-year-old girl presented with a three-day history of fever, and vomiting for one day. During the initial assessment, the patient was lethargic with slight tachycardia, but the physical examination results were unremarkable. She was treated for viral gastritis with oral ondansetron and a oral rehydration solution. However, she exhibited worsened tachycardia with a heart rate of 150 beats per minute and a gallop rhythm after the initial treatment. Electrocardiography showed sinus rhythm with a right bundle branch block; however, chest radiography was normal. FoCUS revealed a moderately reduced ejection fraction and distended inferior vena cava, suggesting acute myocarditis. She was referred to a paediatric cardiologist and echocardiography revealed similar findings. Cardiac enzymes levels were significantly elevated with a troponin T of 15,089 ng/l. Acute myocarditis was diagnosed, and the patient was admitted to the intensive care unit, where she underwent extracorporeal membrane oxygenation (ECMO). The patient was hospitalized for 13 days and was then discharged. FoCUS enables direct assessment of cardiac function, facilitating early diagnosis of critical conditions and improving outcomes.