Mexiletine Treatment for Neonatal LQT3 Syndrome: Case Report and Literature Review

Alena Bagkaki; Alexandros Tsoutsinos; Eleftheria Hatzidaki; Manolis Tzatzarakis; Fragiskos Parthenakis; Ioannis Germanakis

doi:10.3389/fped.2021.674041

Mexiletine Treatment for Neonatal LQT3 Syndrome: Case Report and Literature Review

Front Pediatr. 2021 Aug 24:9:674041. doi: 10.3389/fped.2021.674041. eCollection 2021.

Authors

Alena Bagkaki¹, Alexandros Tsoutsinos², Eleftheria Hatzidaki³, Manolis Tzatzarakis⁴, Fragiskos Parthenakis⁵, Ioannis Germanakis¹

Affiliations

¹ Pediatric Cardiology Unit, Department of Pediatrics, School of Medicine, University Hospital Heraklion, University of Crete, Heraklion, Greece.
² Department of Pediatric Cardiology and Adult Congenital Heart Disease, Onassis Cardiac Surgery Center, Athens, Greece.
³ Department of Neonatology, School of Medicine, University Hospital Heraklion, University of Crete, Heraklion, Greece.
⁴ Laboratory of Toxicology, School of Medicine, University of Crete, Heraklion, Greece.
⁵ Department of Cardiology, School of Medicine, University Hospital Heraklion, University of Crete, Heraklion, Greece.

Abstract

Background: Early diagnosis of long QT type 3 (LQT3) syndrome during the neonatal period is of paramount clinical importance. LQT3 syndrome results in increased mortality and a mutation-specific response to treatment compared to other more common types of LQT syndrome. Mexiletine, a sodium channel blocker, demonstrates a mutation-specific QTc shortening effect in LQT3 syndrome patients. Case Presentation: A neonate manifested marked QTc prolongation after birth. An electrocardiogram (ECG) recording was performed due to positive family history of genetically confirmed LQT3 syndrome (SCN5A gene missense mutation Tyr1795Cys), and an association with sudden cardiac death was found in family members. The mexiletine QTc normalizing effect (QTc shortening from 537 to 443 ms), practical issues related to oral mexiletine treatment of our young patient, along with a literature review regarding identification and mexiletine treatment in infants with LQT3 syndrome are presented. Conclusions: Mexiletine could be considered in the treatment of high-risk LQT3 patients already in the neonatal period in addition to b-blocker therapy. Availability of standardized commercial mexiletine pediatric formulas, serum mexiletine level analyses, and future prospective studies are needed to evaluate the potential beneficial effect of early mexiletine treatment on the incidence of future acute cardiac events in these high-risk LQT syndrome patients.

Keywords: LQT syndrome; LQT3; QT prolongation; SCN5A mutation; case report; child; mexiletine; neonate.

Publication types

Case Reports