Congenital long QT syndromes and Brugada syndrome: the arrhythmogenic ion channel disorders

Abstract

Congenital long QT syndromes (LQTS) and Brugada syndrome are hereditary disorders of cardiac ion channels which result in life-threatening cardiac arrhythmias or sudden cardiac death in patients with anatomically normal hearts. The pathogenesis of these dramatic events has been partially elucidated with the identification of the individual ion channels involved and understanding of the effect of some disease-causing mutations on the membrane currents and action potential. The clinical spectrum of congenital LQTS is broader than previously thought and involves certain patients previously diagnosed with idiosyncratic drug-induced proarrhythmia. The initial treatment for congenital LQTS patients involves beta-blockers in most cases. Indications for implantable cardioverter-defibrillator (ICD) or pace-maker (PM) implantation in selected individuals continue to evolve.

Effects of ECG sampling rate on QT interval variability measurement

“…The QT interval of ECG is a measure of ventricular depolarization and repolarization duration. Corrected for heart rate, it is clinically used to diagnose congenital or acquired QT syndromes [1,2]. The QT interval fluctuates from beat to beat and quantification of this so-called QT interval variability (QTV) has received increasing interest as evidence of the association between increased QTV and elevated risk of cardiac and overall mortality is mounting [3][4][5].…”

1. Chapter 1

“…1.11). 12 Reentry VT/VF By far the most common mechanism for VT and VF is reentry. 13 Reentrant VT frequently starts around an area of scar tissue on the heart, such as might occur as a result of an MI or heart disease.…”