Short QT syndrome. Update on a recent entity

Abstract

The short QT syndrome, a recently discovered ion channel disorder, combines shortened repolarization, a predisposition to atrial and ventricular fibrillatory arrhythmias, and a risk of sudden death. Few cases have been reported, but the prevalence may be underestimated. This syndrome might account for some cases of unexplained ventricular fibrillation in patients with otherwise healthy hearts. Patients have abnormally short QT intervals and refractory periods, and atrial/ventricular fibrillation can be triggered during investigations. Gain-of-function mutations have been detected in three genes encoding potassium channels. Treatment is based on defibrillator implantation, sometimes as a preventive measure. Quinidine may be beneficial in certain cases.

Epidemiology of Arrhythmias and Sudden Cardiac Death in Asia

“…62 Among 10,984 Japanese (females: 49.8%), only 3 (0.03%) subjects exhibited QTc <300 ms. 63 It is likely that a number of the cases of idiopathic VF corresponded to latent or borderline SQTS, and SQTS has been found in 12% of survivors of VF with no apparent cause. 64 SQTS patients with prior history of aborted SCD or syncope have a high risk of recurrent arrhythmic events, including SCD. 65 …”

The Short QT Syndrome

“…Whilst shortened atrial and ventricular refractory periods of SQTS patients [16,71] might be anticipated to increase the risk of reentrant arrhythmia, it is difficult to investigate in detail the mechanisms underlying SQT-linked arrhythmogenesis in humans. At present, there is no animal model that mimics accurately the identified gene mutations in human SQTS.…”

“…Given the evidence for dangerous ventricular arrhythmia and sudden death in SQT families [16,71], it is of some importance that mechanisms of arrhythmogenesis in the syndrome are understood. Whilst shortened atrial and ventricular refractory periods of SQTS patients [16,71] might be anticipated to increase the risk of reentrant arrhythmia, it is difficult to investigate in detail the mechanisms underlying SQT-linked arrhythmogenesis in humans.…”

Shortening of the Short Refractory Periods in Short QT Syndrome

“…Even if apparently straightforward because simply linked to the value of QT interval, diagnosis of SQTS has in fact remained poorly defined over previous years because of changing cut‐off values 6. A diagnostic value of 300 ms,1, 7 then of 320 ms8 for the QT interval and of 340 ms for the corrected QT (QTc)9 had been initially proposed, although some symptomatic patients with SQTS may present with longer QTc interval 4, 10, 11, 12.…”