Ionic and cellular mechanisms underlying J wave syndromes

Abstract

Prominent J waves are encountered in a number of life-threatening cardiac arrhythmia syndromes, including the Brugada (BrS) and early repolarization (ERS) syndromes. BrS and ERS differ with respect to the magnitude and lead location of abnormal J waves and are thought to represent a continuous spectrum of phenotypic expression termed J wave syndromes. Both are associated with the development of polymorphic ventricular tachycardia (VT) and ventricular fibrillation (VF) leading to sudden cardiac death (SCD) in young adults. J wave syndromes are characterized by J-onset and ST-elevation in distinct ECG-leads. The region most affected by BrS is the anterior right ventricular outflow tract, accounting for why J-onset and ST-segment elevation are limited to the right precordial leads. The region most affected in ERS is the inferior wall of the left ventricle, accounting for why the appearance of J waves or early repolarization in the inferior ECG leads is associated with the highest risk for development of arrhythmias and SCD. Risk stratification and the approach to therapy of the J wave syndromes continue to be mired in controversy. Our objective in this chapter is to provide an integrated review of the clinical characteristics, risk stratifiers, as well as the molecular, ionic, cellular and genetic mechanisms underlying the J wave syndromes.