Unexplained Cardiac Arrest in an Apparently Healthy Young Woman

An 18-year-old woman with a history of anorexia nervosa and multiple episodes of dizziness and syncope of unknown cause was transferred to the emergency department by ambulance 1 hour after starting to feel palpitations, dizziness, tightness in the chest, and presyncope at school. At the time of presentation, she was hemodynamically stable, but the symptoms persisted. The ECG recorded at admission is shown in Figure 1A. A supraventricular tachycardia with aberrancy was suspected. Conversion attempts first with vagal maneuvers (carotid sinus massage and Valsalva maneuver) followed by adenosine (6 mg IV) were unsuccessful, but the ventricular rate and the QRS duration normalized gradually within 12 hours. The full cardiovascular and laboratory workup showed unremarkable findings, and the patient was discharged with prescription of metoprolol 25 mg/d.Figure 1. ECG obtained at the time of initial admission and readmission to the emergency department. A , The ECG recorded at initial admission shows regular wide-QRS complex tachycardia with right bundle-branch block morphology and a ventricular rate of 120 bpm, no identifiable P waves, and no atrioventricular dissociation. B , The ECG recorded at readmission shows agonal heart rhythm with …