Introduction:
The long QT syndrome (LQTS) is one of the causes of sudden cardiac death in children. Although the risk factors for cardiac events depending on the genotype have been reported, age-related difference in phenotype remains unknown.
Objectives:
We aimed to clarify the age-and genotype-related clinical features in the young LQTS cohort (form 1 to 20y.o.).
Methods and Results:
This study comprised 101 symptomatic LQTS patients that were genotyped (male n=36, mean age 10.6±4.3). We excluded patients with multiple mutations. Fifty patients carried heterozygous mutations in KCNQ1, 48 in KCNH2 and 3 in SCN5A. LQTS-related cardiac events were classified into 3 categories; syncope, documented Torsades de pointes (TdP) and cardio-pulmonary arrest (CPA). Ninety patients experienced syncope, 7 were documented TdP and 4 suffered CPA. Figure shows a frequency histogram for the ages of first event in each genotype. The mean age of the onset in KCNH2 mutation carriers were significantly older (12.2±4.6y.o.) than those in KCNQ1 (9.2±3.5y.o., p<0.001). The numbers and mean ages of the patients suffered CPA were 1 in KCNQ1 (12y.o.), 2 in KCNH2 (10.5±3.5y.o.) and 1 in SCN5A (6y.o.). TdP was significantly more frequently documented in the patients with KCNH2 mutations (n=6, 13.7±3.3y.o.) than those with KCNQ1 mutations (n=1, 9y.o., p=0.029).
Conclusion:
In the young LQTS patients, therefore, KCNH2 mutation carriers showed a severer phenotype than those of KCNQ1, though their age of onset was older. These finding helped us to choose more appropriate preventive therapy depend on the age of onset and genotype.
Potential depot medroxyprogesterone acetate–triggered torsades de pointes in a case of congenital type 2 long QT syndrome
