Emergent Care / Stabilization:
Follow advanced cardiac life support (ACLS) guidelines to resuscitate the patient. Acquired short QTc intervals can be caused by electrolyte disturbances, acidosis, and hyperthermia, so obtaining and correcting for these values is critical to emergent stabilization.

Diagnosis Overview:
Short QT syndrome (SQTS) is a cardiac channelopathy that leads to a shortened QTc interval, putting the patient at risk for life-threatening arrhythmias and sudden cardiac death (SCD). Typically, otherwise young and healthy patients present after syncopal events or cardiac arrest that occurs without warning.

The average age of diagnosis is around 30 years. However, cases have been reported in infants, suggesting a possible link to sudden infant death syndrome (SIDS), and into the sixth decade of life. In more than 80% of patients, palpitations and atrial fibrillation (AF) occur during childhood and adolescence, making these the most common symptoms. The most common presenting symptoms, though, are cardiac arrest (34%) and syncope (28%), likely related to self-terminated ventricular fibrillation (VF).

The genetics behind SQTS are under active investigation. There are many mutations noted and various subtypes of each. The current understanding points to gain-of-function mutations in potassium channels and/or loss-of-function mutations in calcium channels, resulting in shortened action potentials that lead to dysrhythmias. These mutations can be inherited in an autosomal dominant pattern, but there are cases of patients with no family history and confirmed genetic testing implying de novo mutations. Notably, while genetic in nature, only 25% of those tested are found to have a known mutation.

As the name suggests, a shortened QTc interval is integral to the diagnosis, although there is no formally agreed upon number. A QTc interval < 330 milliseconds (ms) highly suggests the diagnosis, but newer genotypes can include QTc intervals < 360 ms or even < 370 ms. Additionally, ECG can reveal peaked T waves and shortened ST segments.