Abstract
Congenital Long QT Syndrome (LQTS) is a potentially lethal cardiac channelopathy characterized
by prolongation of the corrected QT (QTc) interval on the surface electrocardiogram.
The hallmark phenotypic features are syncope, seizure or sudden death, however most
of the mutation carriers are asymptomatic and their risk for arrhythmias such as Torsade
de pointes (TdP) are low. We report a case of Long QT syndrome with a corrected QT
of 520 ms. For symptom – arrhythmia correlation a loop recorder was implanted with
no documented arrhythmias. Epinephrine testing was performed for clinical risk stratification
leading to Torsades de pointes during recovery phase which required defibrillation.
Genetic testing discovered two pathogenic heterozygous mutations in two different
LQT genes (SCN5A and KCNQ1). We propose a calcium homeostasis mechanism for the interaction of both mutations
that exaggerated the phenotype, while each mutation by itself is causing a relatively
modest phenotype.
Keywords
Abbreviations:
LQTS (Long QT syndrome), QTc (Corrected QT interval), TdP (Torsade de pointes), VT (Ventricular tachycardia), ICD (Implantable cardioverter defibrillator), LQT1 (Long QT type 1), LQT3 (Long QT type 3), PVCs (Premature ventricular complexes), WT (Wild-type), KCNQ1 (Potassium voltage-gated channel, type 1), SCN5A (Sodium channel, voltage-gated, type V, alpha subunit)To read this article in full you will need to make a payment
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Article info
Publication history
Published online: September 15, 2014
Accepted:
July 24,
2014
Received in revised form:
July 22,
2014
Received:
June 4,
2014
Identification
Copyright
© 2014 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
