Autosomal Recessive Long QT Syndrome: Clinical Aspects and Therapy

The autosomal recessive (AR) form of Long QT Syndrome (LQTS) is described both associated with deafness known as Jervell and Lange-Nielsen (JLN) syndrome, and without deafness (WD). The aim of the study is to report the characteristics of AR LQTS patients and the efficacy of the therapy. Data of all children with AR LQTS referred to the Bambino Gesù Children's Hospital IRCCS from September 2012 to September 2021were included. Three (30%) patients had compound heterozygosity and 7 (70%) had homozygous variants of the KCNQ1 gene, the latter showing deafness. Four patients (40%) presented aborted sudden cardiac death (aSCD): three with previous episodes of syncope (75%), the other without previous symptoms (16.6% of asymptomatic patients). An episode of aSCD occurred in 2/3 (66.7%) of WD and heterozygous patients, while in 2/7 (28%) JLN and homozygous patients and in 2/2 patients with QTC > 600 ms. All patients were treated with Nadolol. In 5 Mexiletine was added, shortening QTc and obtaining the disappearance of the T-wave alternance (TWA) in 3/3. Episodes of aSCD seem to be more frequent in LQTS patients with compound heterozygous variants and WD than in those with JLN and homozygous variants. Episodes of aSCD also appear more frequent in children with syncope or with QTc value > 600 ms, even on beta-blocker therapy, than in patients without syncope or with Qtc < 600 ms. However, our descriptive results should be confirmed by larger studies. Moreover, Mexiletine addition reduced QTc value and eliminated TWA.