J Korean Med Sci.  2013 Oct;28(10):1454-1460. 10.3346/jkms.2013.28.10.1454.

Long QT Syndrome: a Korean Single Center Study

• Lee YS
• Kwon BS
• Kim GB
• Oh SI
• Bae EJ
• Park SS
• Noh CI

• KMID: 1777681
• DOI: http://doi.org/10.3346/jkms.2013.28.10.1454

Abstract

The long QT syndrome (LQTS) is a rare hereditary disorder in which affected individuals have a possibility of ventricular tachyarrhythmia and sudden cardiac death. We investigated 62 LQTS (QTc > or = 0.47 sec) and 19 family members whose genetic study revealed mutation of LQT gene. In the proband group, the modes of presentation were ECG abnormality (38.7%), aborted cardiac arrest (24.2%), and syncope or seizure (19.4%). Median age of initial symptom development was 10.5 yr. Genetic studies were performed in 61; and mutations were found in 40 cases (KCNQ1 in 19, KCNH2 in 10, SCN5A in 7, KCNJ2 in 3, and CACNA1C in 1). In the family group, the penetrance of LQT gene mutation was 57.9%. QTc was longer as patients had the history of syncope (P = 0.001), ventricular tachycardia (P = 0.017) and aborted arrest (P = 0.010). QTc longer than 0.508 sec could be a cut-off value for major cardiac events (sensitivity 0.806, specificity 0.600). Beta-blocker was frequently applied for treatment and had significant effects on reducing QTc (P = 0.007). Implantable cardioverter defibrillators were applied in 6 patients. Congenital LQTS is a potentially lethal disease. It shows various genetic mutations with low penetrance in Korean patients.

Keyword

Long QT Syndrome; Tachycardia; Heart Ventricles; Mutation

MeSH Terms

Adolescent
Adult
Aged
Aged, 80 and over
Asian Continental Ancestry Group/genetics
Calcium Channels/genetics
Child
Child, Preschool
Electrocardiography
Heart Arrest/genetics/pathology
Humans
Infant
KCNQ1 Potassium Channel/genetics
KCNQ2 Potassium Channel/genetics
Long QT Syndrome/*diagnosis/*genetics
Middle Aged
Mutation/*genetics
NAV1.5 Voltage-Gated Sodium Channel/genetics
Penetrance
Potassium Channels, Inwardly Rectifying/genetics
Republic of Korea
Risk Factors
Seizures/genetics/pathology
Young Adult
Calcium Channels
KCNQ1 Potassium Channel
KCNQ2 Potassium Channel
NAV1.5 Voltage-Gated Sodium Channel
Potassium Channels, Inwardly Rectifying

Figure

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  Fig. 1 The age distribution in proband group. The bright gray columns represent the number of symptomatic subjects and the dark columns represent the total number including incidentally found subjects with ECG abnormalities at each age groups.

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  Fig. 2 The modes of presentation in proband group. ECG abnormality was the most frequent initial presentation, but aborted cardiac arrest and syncope are more than half (71.1%) in symptomatic presentation.

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  Fig. 3 The distributions of genetic mutation confirmed in the proband and family group. KCNQ1, KCNH2, SCN5A, KCNJ7, and CACNA1C are genes for LQT1, 2, 3, 7, and 8, respectively.

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