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Short QT syndrome. Genotype-phenotype correlations.
Martin Borggrefe1, Christian Wolpert, Charles Antzelevitch
11st Department of Medicine-Cardiology, University Hospital Mannheim, Faculty of Clinical Medicine of the University of Heidelberg, 68167 Mannheim, Germany. martin.borggrefe@med.ma.uni-heidelberg.de
Journal of Electrocardiology
|October 18, 2005
Summary
Short QT syndrome, a genetic disorder, increases risks of sudden cardiac death and arrhythmias. Quinidine shows promise in managing this condition, potentially serving as an alternative to implantable cardioverter-defibrillators.
Area of Science:
- Cardiology
- Genetics
- Electrophysiology
Background:
- Short QT syndrome (SQT) is a rare congenital disorder linked to familial atrial fibrillation, syncope, and sudden cardiac death.
- It is caused by gain-of-function mutations in genes encoding cardiac potassium channels (KCNH2, KCNQ1, KCNJ2).
- Electrocardiographically, SQT is defined by a shortened QTc interval (<300-320 ms) and lack of rate adaptation.
Purpose of the Study:
- To review the characteristics, genetic basis, and management strategies for Short QT syndrome.
- To evaluate the efficacy of quinidine in managing SQT, particularly in patients with HERG mutations.
Main Methods:
- Review of existing literature on Short QT syndrome.
- Analysis of the effects of various drugs (sotalol, ibutilide, flecainide, quinidine) on QT interval and arrhythmias.
- Assessment of quinidine's impact on IKr current and ventricular tachyarrhythmias in SQT patients.
Main Results:
- Programmed electrical stimulation reveals shortened refractory periods and inducible ventricular tachyarrhythmias in SQT.
- Sudden cardiac death is a significant risk across all age groups, including newborns.
- Quinidine effectively suppressed IKr gain-of-function, prolonged the QT interval, and rendered ventricular tachyarrhythmias noninducible in HERG-mutated patients.
Conclusions:
- Implantable cardioverter-defibrillators (ICDs) are the primary therapy for SQT due to high sudden death incidence, though inappropriate shocks are a concern.
- Quinidine demonstrates efficacy in managing SQT by normalizing the QT interval/heart rate relationship and suppressing arrhythmias.
- Quinidine may serve as an adjunct or alternative therapy to ICDs, especially in pediatric and neonatal populations.