Sodium channel blocker in therapy of type 3 long Q–T syndrome

Long QT syndrome caused by a mutation in the SCN5A gene is the third most common molecular genetic type of the syndrome. Cardiac events in long QT syndrome type 3 are associated with a high risk of death, and beta-blocker therapy is not effective enough. Given the impaired inactivation of the cardiomyocyte sodium channel due to variants in the SCN5A gene, sodium channel blockers have been proposed as gene-specific therapy.The aim of this study was to evaluate the efficacy and safety of therapy with the sodium channel blocker lappaconitine hydrobromide in a cohort of children with type 3 long QT syndrome.Materials and methods. The study included 16 patients from 11 unrelated families who received combination therapy with a betablocker and lappaconitine hydrobromide for 48±37 months.Results. The main indication for the use of lappaconitine hydrobromide was a pronounced prolongation of the QT interval (in 81.25% of cases). The duration of the QTc interval significantly decreased after the administration of lappaconitine hydrobromide both according to the standard ECG (from 507±20.7 to 451±26.0 ms; p=0.000003) and during Holter monitoring (mean QTc from 536±16.2 to 489±24.9 ms; p=0.0002). No spontaneous arrhythmic events were noted during combined antiarrhythmic therapy.Conclusion. The sodium channel blocker lappaconitine hydrobromide in patients with type 3 long QT syndrome affects such a risk factor for sudden cardiac death as the QTc interval by significantly reducing its duration. The drug can be recommended for use in addition to beta-blocker therapy for QTc ≥ 500 ms on a standard ECG or mean QTc during Holter monitoring in patients with type 3 of the syndrome.