Prognosis of long QT syndrome patients: The experience of the French referral center of Nantes hospital

Abstract

Congenital long QT syndrome (LQTS) is a hereditary disease characterized by prolonged QTc and a risk of sudden cardiac death (SCD) in young people. The aim of this study is to report the experience of the referral center of Nantes hospital. Patients were recruited from 15 tertiary centers in France between 1997 and 2018. Clinical data and 12-lead ECG were collected. Genetic screening was performed using dHPLC-DNA sequencing, HRM or targeted sequencing (Haloplex technology®) for at least KCNQ1, KCNH2 and SCN5A. The population consisted in 741 patients affected by LQTS according to the Schwartz score (447 (60%) females, 404 (55%) index cases). Mean age at diagnosis was 33 ± 21 years. In this cohort, 343 patients (46%) were symptomatic: 66 patients experienced resuscitated SCD (9%), 211 (28%) syncope and 66 (9%) ventricular arrhythmias. One hundred and two patients (14%) had history of familial SCD. At baseline, heart rate was 69 ± 19 bpm, PR 149 ± 39 mm, QRS 86 ± 16 mm and QTc 479 ± 62 mm. Three hundred and eighty-six patients (52%) were treated with beta-blockers and 88 patients (12%) were implanted with an ICD. Genetic screening was performed in 668 (90%) patients. Genetic screening for the 3 major genes of LQTS was positive for 411 patients (62%): 165 variants (25%) in KCNQ1, 178 variants (27%) in KCNH2, 68 variants (10%) in SCN5A and 22 variants (3%) in minor genes of LQTS. During a mean follow-up of 6.2 ± 5.2 years, 64 patients (9%) underwent arrhythmic events, 7 SCD (1%), 8 appropriate ICD therapy (1%) and 49 ventricular arrhythmias (7%). The rate of arrhythmic event was 1.39%/y. Mean age at the first event was 41.7 ± 21.5 years. Sixteen patients (2%) died of non-arrhythmic causes. Care in a specialized inherited arrhythmia center is associated with a low incidence of arrhythmic event (1.39%/y) in patients with LQTS.