Mexiletine in a Newborn with Type 3 Long QT Syndrome: When Access is Difficult

Introduction

Long QT syndrome type 3 (LQT3) is a highly lethal channelopathy. It is associated with delayed closing of sodium channels, resulting from mutations in the SCN5A gene, with an autosomal dominant pattern, responsible for 7-10% of all long QT syndromes (LQTSs). The initial presentation can have a wide spectrum, from asymptomatic to sudden death in the first year of life. The addition of class IB sodium channel blocker (mexiletine) to propranolol or nadolol is considered a gene-guided treatment, as its benefit is proven in LQT3. In some countries, such as Brazil, it is not feasible to treat patients with LQT3, because of the unavailability of mexiletine.

We present here a severe case of a child with LQT3, who underwent multiple implantable cardioverter-defibrillator (ICD) therapies because of difficult access to mexiletine in Brazil.

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