Type 3 long QT syndrome: Is the effectiveness of treatment with beta-blockers population-specific?

Background: The efficacy of beta-blocker treatment in type 3 long QT syndrome (LQT3) remains debated.
Objectives: The purpose of this study was to test the hypothesis that beta-blocker use is associated with cardiac events (CEs) in a French cohort of LQT3 patients.
Methods: All patients with a likely pathogenic/pathogenic variant in the SCN5A gene (linked to LQT3) were included and followed-up. Documented ventricular tachycardia/ventricular fibrillation, torsades de pointes, aborted cardiac arrest, sudden death, and appropriate shocks were considered as severe cardiac events (SCEs). CEs also included syncope.
Results: We included 147 patients from 54 families carrying 23 variants. Six of the patients developed symptoms before the age of 1 year and were analyzed separately. The 141 remaining patients (52.5% male; median age at diagnosis 24.0 years) were followed-up for a median of 11 years. The probabilities of a CE and an SCE from birth to the age of 40 were 20.5% and 9.9%, respectively. QTc prolongation (hazard ratio [HR] 1.12 [1.0-1.2]; P = .005]) and proband status (HR 4.07 [1.9-8.9]; P <.001) were independently associated with the occurrence of CEs. Proband status (HR 8.13 [1.7-38.8]; P = .009) was found to be independently associated with SCEs, whereas QTc prolongation (HR 1.11 [1.0-1.3]; P = .108) did not reach statistical significance. The cumulative probability of the age at first CE/SCE was not lower in patients treated with a beta-blocker.
Conclusion: In agreement with the literature, proband status and lengthened QTc were associated with a higher risk of CEs. Our data do not show a protective effect of beta-blocker treatment.
Competing Interests: Disclosures The authors have no conflicts to disclose.
(Copyright © 2023 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)