A previously healthy 15-year-old boy presents to the emergency department in cardiac arrest. He was in class when he suddenly fainted and became unresponsive. His teacher began chest compressions and he has received epinephrine and defibrillation from paramedics while in transport. On arrival, the patient remains pulseless and is pronounced dead. An autopsy is performed and is notable for no clear abnormalities. The patient’s laboratory studies were unremarkable from a visit to the pediatrician 3 weeks ago. A previous ECG is seen in Figure A. Which of the following is the most likely underlying etiology of this patient’s death?
Short QT syndrome
Ventricular tachycardia
Complete heart block
Torsades des pointes
Short QT syndrome
This healthy pediatric patient is presenting with cardiac arrest and an ECG demonstrating a short QT segment. Short QT syndrome is lethal and can lead to cardiac arrest in young, otherwise healthy patients.

Short QT syndrome is an inherited condition that is caused by ion channel mutations (the most common identified mutation is a mutation in the cardiac myocyte potassium channel). There is no strict criteria for short QT syndrome, but the QT segment is often < 320 ms. Patients are usually young and healthy, and it is very common for the first presentation of this disease to be syncope or sudden cardiac death. ECG features suggestive of this condition include a short QT interval (without a clearly defined value but often < 360 ms) that is fixed (does not change with exercise or rest), peaked T waves, short or even absent ST segments, and episodes of atrial fibrillation or ventricular fibrillation in a patient in whom this would not be expected (such as a young patient). The only effective intervention is the placement of an implantable cardioverter-defibrillator.

Bjerregaard and Gussak discuss short QT syndrome. They note it is a heritable condition of the conduction system of the heart that can lead to lethal dysrhythmias. They discuss the management of this condition and recommend an implantable cardioverter-defibrillator.

Figure/Illustration A is an ECG demonstrating a short QT segment (red arrow). Note the T waves appear peaked which can be seen in this syndrome. This may suggest hyperkalemia, but this patient’s labs were normal at his appointment when the ECG was taken.

Incorrect Answers:
Answer A: Complete heart block is more common in elderly patients with acute coronary syndrome and presents with regular P-P and R-R intervals with complete P-R dissociation. It may cause syncope but is not associated with short QT syndrome. Management involves the placement of a pacemaker.

Answer C: Torsades des pointes is associated with a prolonged QT segment that progresses to the classic twisting of the QRS complexes around an isoelectric baseline. It can lead to cardiac arrest and requires immediate cessation of QT-prolonging medications and administration of magnesium. Note that this patient’s QT segment is short rather than long.

Answer D: Ventricular fibrillation presents with disorganized electrical activity with no discernible rhythm. While this patient may have arrested from ventricular fibrillation, the most likely underlying etiology for his cardiac arrest given his age, ECG, and risk factors is an underlying condition such as short QT syndrome. For this reason, short QT syndrome is a better answer.

Answer E: Ventricular tachycardia could also occur in short QT syndrome and may have caused this patient’s cardiac arrest. It presents with a monomorphic wide complex tachycardia that may cause arrest. Unstable patients require cardioversion while pulseless patients require defibrillation. Note that if this patient arrested from ventricular tachycardia, it was likely secondary to short QT syndrome.

Bullet Summary:
Short QT syndrome is a rare but possible diagnosis in young, healthy patients who present with recurrent syncope or cardiac arrest.