Myocardial infarction is a rare condition in children. We present the case of a 14-year-old girl with known cardiac abnormalities admitted to our pediatric cardiology department with cough, cyanosis, low level of consciousness, and difficult breathing. Two days after her admission, she developed severe thoracic pain associated with tachycardia and agitation. The electrocardiogram revealed myocardial ischemia and then myocardial infarction with a rapid onset of cardiac arrest not responding to resuscitation techniques. Postmortem examination confirmed the diagnosis.