Pathophysiology of the long QT syndrome
- Peter J Zimetbaum, MD
Peter J Zimetbaum, MD
- Section Editor — Cardiac Arrhythmias
- Professor of Medicine
- Harvard Medical School
- Section Editors
- Samuel Lévy, MD
Samuel Lévy, MD
- Section Editor — Cardiac Arrhythmias
- Professor of Cardiology
- University of Marseille, France
- John K Triedman, MD
John K Triedman, MD
- Section Editor — Pediatric Cardiology
- Professor of Pediatrics
- Harvard Medical School
- Samuel Asirvatham, MD
Samuel Asirvatham, MD
- Section Editor — Long QT Syndrome
- Professor of Medicine and Pediatrics
- Mayo Clinic College of Medicine
The long QT syndrome (LQTS) is the phenotypic description of a group of disorders that are defined by two characteristics:
●Prolongation of the QT interval
●A characteristic arrhythmia, polymorphic ventricular tachycardia
The LQTS can be congenital, as an inherited disorder usually involving a mutation of an ion channel gene, or can be acquired as an adverse response to medication, metabolic abnormalities, or bradyarrhythmias (table 1) [1,2]. Torsades de pointes (TdP) or "twisting of points" is the specific type of polymorphic ventricular tachycardia (VT) associated with either form of the LQTS.
There are some pathophysiologic differences between the acquired and congenital forms of the LQTS.
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- Derangements in ion flow
- - The normal action potential
- - Prolonged repolarization and EADs
- - Triggered activity
- - Common precipitants of EADs and triggered activity
- Increased sympathetic activity
- Dispersion of repolarization and reentry
- Initiation and maintenanance of VT