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7.2.2 Long QT syndrome (including acquired long

QT syndrome) LQTS is characterized by a prolonged QT interval and VAs mainly triggered by adrenergic activation. The mean age at presentation is 14 years. The annual rate of SCD in asymptomatic patients with untreated LQTS has been estimated to be less than 0.5%,82 while it increases to around 5% in those with history of syncope.931 Rare variants in 17 genes932 have been associated with LQTS. However, the causality for several of the identified genes has been questioned.166 The undisputed genes are those causing LQT1, LQT2 and LQTS3: KCNQ1, KCNH2 and SCN5A, respectively, with genespecific triggers being exercise (LQTS1), emotional stress (LQTS2) and sleep (LQTS3). Genetic screening identifies a mutation in 75% of LQTS cases and three main genes account for 90% of positively genotyped cases.178 The subtypes of LQTS may be grouped as follows:

(1) Autosomal-dominant LQTS (prevalence: 1 in 2500) without extra-cardiac manifestation. (2) Autosomal-dominant LQTS with extra-cardiac manifestation,

comprising: (a) Andersen–Tawil Syndrome (LQT7), increasingly considered

its own entity.933,934 (b) Timothy Syndrome (LQT8), characterized by prolonged

QT, syndactyly, cardiac malformations, autism spectrum disorder and dysmorphism.935 (3) Autosomal-recessive LQTS (Jervell and Lange–Nielsen Syndrome), combining extreme QT prolongation with congenital deafness.936

This panel of experts has confirmed the diagnostic criteria proposed in the previous version of the guidelines: a QTc ≥480 ms or a LQTS risk score .3937 (Table 10) for clinical diagnosis (Figures 29 and 30). In the presence of arrhythmic syncope or CA, a QTc ≥460 ms is sufficient to consider a diagnosis of LQTS. A challenge for the clinician is establishing the duration of the QT interval in patients with broad QRS complexes (e.g. in the presence of ventricular pacing or ventricular conduction defects). In this setting, a formula has been proposed that adjusts QT by QRS duration.938 While measuring the QT, the patient moving briskly from recumbent to

Patient with idiopathic v entricular fibrillation

Catheter ablation of PVC triggers

(Class IIa)

Recu r r ent ICD shocks

Recu r r ent ICD shocks

Acute t r eatment:

Isop r ote r enol

V er

V

V a pamil Quinidine (Class IIa) Ch r onic t r eatment:

Quinidine (Class IIa)

Genetic counselling and testing

(Class IIb)

ICD implantation

(Class I)

Figure 27 Algorithm for the management of patients with idiopathic ventricular fibrillation. ICD, implantable cardioverter defibrillator; PVC, premature ventricular complex. Downloaded from academic.oup.com/eurheartj/article/43/40/3997/6675633 by guest on 07 October 2026