Short QT syndrome (SQTS) constitutes a rare inherited arrhythmogenic disorder with an estimated prevalence of 2.7 in 100,000 inhabitants or 0.02% to 0.1% and with a male predominance [1].

SQTS is characterized by an abbreviated rate-corrected QT (QTc) interval on the electrocardiogram (ECG) associated with a high risk of atrial fibrillation (AF), and ventricular tachycardia/fibrillation (VT/VF), which may cause dizziness, syncope, cardiac arrest (CA) or even sudden cardiac death (SCD). These manifestations can occur at any time from early infancy to old age. SQTS is characterized by very short QT/QTc intervals caused by mutations in several genes, particularly in the first three K+ channel -related variants (SQT1–3); these result from gain of function (GOF) mutations in genes that encode K+ channel subunits, which are responsible for the IKr, IKs and IK1 cardiac K+ currents, respectively.

SQTS is diagnosed mainly based on the ECG but may also include clinical and family history, and genetic testing. The current diagnostic criterium for a short QT interval is 330–370 ms (QTc) [2]. Gussak et al. were the first to describe the entity [3]. They reported a brother, a sister, and their mother, who had an idiopathic persistently short QT interval.

All the three family members had QTc intervals of <80% of the predicted value. The 17-year-old-girl required cardioversion for several episodes of paroxysmal AF (according to the definition, paroxysmal AF terminates spontaneously or with intervention within 7 days of onset). At a heart rate (HR) of 69 bpm, her QT interval measured 280 ms. Her 21-year-old brother and 51-year-old mother displayed QT intervals of 272 ms (HR of 58 bpm) and 260 ms (HR of 74 bpm), respectively. The publication also included an unrelated 37-year-old female with similar ECG changes (QT interval of 260 ms), which were associated with SCD.

Hong et al [4] reported that in the family originally studied by Gussak et al. [3], the deceased maternal grandfather also had short QT interval and chronic AF.

Programmed electrical stimulation in the mother and the two siblings revealed remarkably short atrial and ventricular refractory periods and inducibility of AF and VF. All three affected members of the family received implantable cardioverter defibrillators, and treatment with propafenone maintained them free of AF.

Following these cornerstone observations, there were other reports of families with congenital short QT interval associated with arrhythmias and SCD.

Variants causing SQTS have been located to genes encoding cardiac cation channels causing an accentuated K+ efflux, or an attenuated Ca++ influx, which both result in a shortening of the ventricular action potential and a short QT interval. Publications have dealt with the issue of genes and associated mutations that have been linked to congenital SQTS [5].