When headaches are not neurological: an unusual presentation of Ebstein's anomaly

A 16-year-old male was admitted following a loss of vision. Baseline observations demonstrated SpO2 80% on air, tachycardia of 180 beats per minute (bpm) and hypotension of 90/50 mmHg. He reported bilateral visual disturbance while sitting in bed together with breathlessness, chest discomfort and dizziness but had not had palpitation or syncope. He had been prescribed propranolol for recurrent migraines of increasing frequency with similar visual disturbances, nausea and vomiting but with no perceived benefit. He was otherwise well, a non-smoker who drank minimally and denied recreational drug use. 
On examination, the jugular venous pressure was elevated but there were no other cardiorespiratory findings of note. Arterial blood gas analysis revealed profound hypoxia and a compensated metabolic acidosis. A 12-lead electrocardiogram demonstrated a supraventricular tachycardia with broad QRS (Figure 1). Carotid sinus massage and intravenous adenosine had no effect. Electrolyte levels were abnormal (potassium 2.7 mmol/litre, magnesium 0.45 mmol/litre, corrected calcium 1.60 mmol/litre) and a central venous line was inserted to allow electrolyte replacement. During this procedure, he spontaneously reverted to sinus rhythm at a rate of 70 bpm. 
A repeat electrocardiogram showed sinus rhythm with normal axis but T wave inversion in the inferior leads and evidence of pre-excitation with a short PR interval and classical delta waves (Figure 2). As a result, Wolff–Parkinson–White syndrome was diagnosed. The chest radiograph showed an abnormal, globular cardiac silhouette (Figure 3). 
Following return to sinus rhythm, the blood pressure and acid–base status normalized. Routine transthoracic echocardiography demonstrated Ebstein's anomaly with an associated atrial septal defect and small membranous ventricular septal defect.