Short QT syndrome

Introduction

Short QT syndrome (SQTS) is characterized by a reduced duration of cardiac repolarization, which constitutes the substrate for the development of life threatening arrhythmias. 

Five genes have been linked to SQTS (KCNH2, KCNQ1, KCNJ2, CACNA1C and CACNB2b), but the yield of genetic screening remains low (20% overall).

The disease is highly lethal in all age groups, including children, and the probability of a first cardiac arrest by the age of 40 years is approx. 40%.

Clinical diagnosis

  • SQTS is diagnosed in the presence of a QTc ≤340 ms.
  • SQTS should be considered in the presence of a QTc ≤360 ms and one or more of the following:
  1. A confirmed pathogenic station
  2. A family history of SQTS
  3. A family history of sudden death at age ,40 years
  4. (d) Survival from a VT/VF episode in the absence of heart disease

Clinical features

  • Cardiac arrest
  • Ventricular fibrillation
  • Atrial fibrillation

ECG features

  • Short QT interval 
  • Peaked T waves (most commonly seen in precordial leads)
  • Episodes of VF and AFib

Possible mechanism of lethal arrhythmias

  • Extremely short atrial and ventricular refractory periods (manifest on the ECG as a short QT interval)
  • Transmural dispersion of repolarization, i.e., the different layers of the myocardium (endocardium, epicardium and the mid-myocardial ‘M-cells’) repolarise at different rates

Treatment

  • ICD in patients who survive a previous cardiac arrest as a secondary preventive measure (the rate of recurrence of cardiac arrest is approx. 10% per year)
  • Quinidine
  • Sotalol 

ECG 1 Patient with a SQT on a 12-lead ECG which was diagnosed during family surveillance after death of a brother at the age of 27 years (notice also peaked T waves)


References

  1. Priori SG, Blomström-Lundqvist C, Mazzanti A, Blom N, Borggrefe M, Camm J, Elliott PM, Fitzsimons D, Hatala R, Hindricks G, Kirchhof P, Kjeldsen K, Kuck KH, Hernandez-Madrid A, Nikolaou N, Norekvål TM, Spaulding C, Van Veldhuisen DJ; Task Force for the Management of Patients with Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death of the European Society of Cardiology (ESC). 2015 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: The Task Force for the Management of Patients with Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death of the European Society of Cardiology (ESC)Endorsed by: Association for European Paediatric and Congenital Cardiology (AEPC). Europace. 2015 Nov;17(11):1601-87. doi: 10.1093/europace/euv319. Epub 2015 Aug 29. PMID: 26318695.
  2. https://litfl.com/short-qt-syndrome-ecg-library/