Genetic and Clinical Characteristics of Patients with Congenital Long QT Syndrome- Genotype. Experiences During Long-Term Follow-up

pp. 114-120

Abstract

Background: Congenital long QT syndrome (LQTS) is an inherited channelopathy with a broad genetic spectrum but with a common phenotypic manifestation, the prolonged QT interval. However, its clinical presentation and natural history are highly variable.

Objectives: The aim of this study was to define the genetic and clinical characteristics of patients with congenital LQTS during a long-term follow-up.

Methods: Retrospective cohort study of patients with congenital LQTS genotype. The incidence of serious events at follow-up was defined. Quantitative variables are expressed as median and interquartile range (IQR) and qualitative variables as frequency and percentage.

Results: Forty-four patients were included. Thirty percent of patients had LQTS1 genotype, 65% LQTS2 genotype and 5% LQTS3 genotype; 57% of cases carried the missense mutation, 11% the nonsense mutation and 32% the frameshift mutation. The corrected QT interval was 490 msec (IQR 462-498). The phenotype was present in 66% of patients, but it remained permanently only in 32%. Syncopal episodes occurred in 39% of patients. Cardiac arrest was the first manifestation in 7% of cases. Syncope recurred in 11% of patients even after pharmacological therapy, and 5% suffered sudden death. Seven patients received an implantable cardioverter-defibrillator (ICD). Among them, 29% received shocks due to ventricular tachycardia or ventricular fibrillation (VT/VF) and 58% presented device-related complications.

Conclusions: Most patients had the LQTS1 or LQTS2 genotype, the intermittent phenotype, and a good response to treatment. Implantation at an early age and the high rate of complications during long-term follow-up require careful evaluation when indicating an ICD.