The Long and Short of QT Intervals

Abstract

The long QT syndrome (LQTS) describes the phenotype of a group of disorders characterised by a prolonged QT interval on ECG and a propensity to develop torsades de pointes (TdP) ventricular tachycardia. This frequently leads to syncope or sudden cardiac death (SCD) in otherwise healthy individuals.

The underlying pathophysiology involves prolongation of ventricular repolarisation, which is sculpted by either loss-of-function of ventricular K+ channels, or gain-offunction of the Na+ channels. Early afterdepolarisations (EAD) that reach ventricular depolarisation thresholds predispose to TdP, which may degenerate into ventricular fibrillation.

LQTS may be inherited or acquired. The incidence is around 1:2,500. Pathophysiology, genetics, diagnosis and anaesthetic implications are discussed.