Congenital long QT syndrome in children

Ivana Cerović,Jovan Košutić

doi:10.5937/medpodm1602056c

Abstract

Long QT syndrome (LQTS) is a cardiac repolarization disorder characterized by prolonged QT interval on the electrocardiogram (ECG) and increased propensity to ventricular tachyarrhythmias and cardiac events. LQTS might be acquired or congenital, which presents a group of channelopathies that occur due to mutation in one of 15 so far identified genes. The most frequent types of congenital LTQS are LQT1, LQT2 and LQT3. Prolonged or delayed repolarization leads to the increase of action potential duration which predisposes early afterdepolarization, as well as the amplification of transmural dispersion of repolarization, both contributing to the development of Torsades de Pointes ventricular tachycardia. Clinical manifestations of LQTS are palpitations, syncope, aborted cardiac arrest or sudden cardiac death, but it can also be asymptomatic. Trigger factors for symptoms are specific for certain genotype. LQTS examination includes thorough clinical and family history focused on distinctive data (repeated syncopes, cases of sudden cardiac death in the family, hereditary arrhythmias), resting ECG, exercise stress testing and genetic analysis, with additional methods (serial ECG records, 24h ECG Holter, epinephrine test). Clinical LQTS diagnosis is based on Schwartz's scoring system, while the criteria for final diagnosis of LQTS depend on Schwartz's score, QT interval duration, presence of pathogenic mutation and clinical symptoms. Treatment approach begins with lifestyle modifications and β-blockers therapy, while other options include implantable cardioverter- defibrillator, permanent pacemaker or surgical sympathectomy. Sudden cardiac death is the reason of 90% of sudden deaths in young athletes, while LQTS is one of its causes. Recommendations for physical activities in children with congenital LQTS arise from the ones for adults and they presume very strict limitations. Further researches are expected to advance the understanding of genotype-phenotype correlation of congenital LQTS and enable eventual genetically-guided personalized treatment, novel insight into rare LQTS types, as well as more precise recommendations for physical activity of LQTS children.

Highlights

Genetic and molecular basisLong QT syndrome (LQTS) is a cardiac repolarization disorder characterized by prolonged QT interval on the electrocardiogram (ECG) and increased propensity to ventricular tachyarrhythmias (Torsades de pointes (TdP) tachycardia and ventricular fibrillation (VF))
Long QT syndrome (LQTS) is a cardiac repolarization disorder characterized by prolonged QT interval on the electrocardiogram (ECG) and increased propensity to ventricular tachyarrhythmias and cardiac events
Congenital LQTS presents a group of monogenic, predominantly autosomal-dominant (A-D) channelopathies or other proteinopathies, denominated as LQT1-LQT15, according to 15 so far identified genes known to be associated with LQTS (3)

Summary

Introduction

Long QT syndrome (LQTS) is a cardiac repolarization disorder characterized by prolonged QT interval on the electrocardiogram (ECG) and increased propensity to ventricular tachyarrhythmias (Torsades de pointes (TdP) tachycardia and ventricular fibrillation (VF)) (figure 1a). It can be asymptomatic or clinically manifested as palpitations, syncope, aborted cardiac arrest (ACA) or sudden cardiac death (SCD) (1). The most common forms are LQT1, LQT2 and LQT3, constituting about 90% of genetically proven cases (1) These mutations cause alterations in specific ion channels which participate in action potential, leading to the delay of repolarization process. Comorbidity of epilepsy with LQT2 due to KCNH2 expression in brain makes their differential diagnosis very important for therapeutic approach (18)

Diagnostic methods and criteria for LQTS

High dynamic

Findings

Conclusion