[Familial short QT syndrome]

Area of Science:

• Cardiology
• Genetics
• Electrophysiology

Context:

• Short QT syndrome (SQTS) is a rare genetic disorder characterized by a markedly shortened QT interval on ECG (< or = 300 ms).
• It is associated with a high risk of malignant ventricular arrhythmias, syncope, and sudden cardiac death, particularly in young individuals and infants.
• The condition is frequently linked with atrial fibrillation and exhibits autosomal dominant inheritance.

Purpose:

• To describe the clinical and genetic characteristics of Short QT syndrome.
• To elucidate the underlying electrophysiological mechanisms contributing to the syndrome.
• To discuss current management strategies for preventing sudden death.

Summary:

• SQTS is linked to mutations in genes (KCNQ1, KCNH2, KCNJ2) encoding cardiac potassium channels, resulting in a 'gain of function'.
• This gain of function shortens action potential duration and refractory periods in both atria and ventricles.
• Electrophysiological studies demonstrate inducible ventricular fibrillation in most affected patients.

Impact:

• Understanding the genetic basis and electrophysiological consequences of SQTS is crucial for diagnosis and risk stratification.
• Early identification and intervention are vital due to the potentially fatal nature of the syndrome.
• The only current effective treatment for preventing sudden death is an automatic implantable cardioverter-defibrillator (AICD).