Abstract 15417: High Prevalence of Late Onset T in Patients With Long QT Syndrome Type 8
Background: In long QT syndrome type 1 to type 3 (LQT3), T wave morphologies (TWMs) in 12-lead-ECGs have been well explored. The consequences of these are helpful to distinguish the genotype before genetic analysis, and the late onset T (LOT) has been reported as a specific characteristic in LQT3. Long QT syndrome type 8 (LQT8) is caused by mutations in CACNA1c, which have been regarded as the cause only for Timothy syndrome, a systematic disease with QT prolongation. However, recent advances in genetic analysis have revealed that CACNA1c mutations could cause LQT8 in patients without systematic disorders, and the LOT has been frequently observed in LQT8 patients.
Purpose: We aimed to clarify the TWMs in patients with LQT8 and to compare these with their phenotypes.
Methods: The cohort consisted of 17 LQT8 probands (4 males) and their family members from 12 families (9 mutations) including a Timothy syndrome patient. LOT was defined as a T wave with the start point after more than half of the QT duration. TWMs were classified into 3 types; normal T, LOT and two peaks T. Phenotypes and mutation locations were compared depending on the types of TWMs.
Results: A proband was excluded from the TWM analysis due to conduction block. The mean age of 16 participants was 17±13 years old. LOT was detected in 10 carriers (62.5%), normal T in 5 and two peaks T in 2. The QTc intervals at rest were longer tendency in carriers with LOT (480±16 ms) than normal T (432±16 ms). Six participants (60%) with LOT suffered syncope or ventricular arrhythmias, whereas only one suffered syncope without LOT. As shown in the figure, LOT was highly detected in carriers with mutations located in domain linkers (n=7) than in transmembrane (n=2) or segment linkers (n=1).
Conclusions: More than half of the LQT8 patients showed LOT and suffered syncope or ventricular arrhythmias. Further investigation would be required for the differentiation between LQT3 and LQT8 in patients showing LOT for the optimized therapy.
Author Disclosures: S. Ohno: None. J. Ozawa: None. M. Fukuyama: None. T. Makiyama: None. M. Horie: None.
- © 2016 by American Heart Association, Inc.