J Wave Syndromes: From Cell to Bedside

Abstract

The J wave, a deflection that follows the QRS complex of the surface ECG, is usually partially buried in the R wave in humans, appearing as a J point elevation. An early repolarization (ER) pattern characterized by J point elevation, slurring of the terminal part of the QRS and ST segment elevation has long been recognized and considered to be totally benign. Recent studies have presented evidence demonstrating that an ER pattern in inferior leads or infero-lateral leads is associated with increased risk for life-threatening arrhythmias, named early repolarization syndrome (ERS). ERS and Brugada syndrome (BrS) share similar ECG characteristics, clinical outcomes, risk factors as well as a common arrhythmic platform related to amplification of I tomediated J waves. Although BrS and early repolarization syndrome (ERS) differ with respect to the magnitude and lead location of abnormal J wave manifestation, they can be considered to represent a continuous spectrum of phenotypic expression, termed J wave syndromes. ERS has been proposed to be divided into three subtypes: Type 1, displaying an ER pattern predominantly in the lateral precordial leads, is prevalent among healthy male athletes and rarely seen in VF survivors; Type 2, displaying an ER pattern predominantly in the inferior or infero-lateral leads, is associated with a higher level of risk; whereas Type 3, displaying an ER pattern globally in the inferior, lateral and right precordial leads, is associated with the highest level of risk for development of malignant arrhythmias and is often associated with VF storms. KeywordsCardiac arrhythmias; Sudden cardiac death; Sudden cardiac arrest; Transient outward current; J point elevation; Early repolarization syndrome; Brugada syndrome; Idiopathic Ventricular fibrillation; Hypothermia; STEMI The J wave is a deflection that follows the QRS complex on the surface electrocardiogram (ECG). When partially buried in the R wave, the J wave appears as a J point elevation and may be accompanied by an ST segment elevation, an ECG feature referred to as an early repolarization (ER) pattern. Recent studies have provided evidence in support of an © 2011 Elsevier Inc. All rights reserved. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Conflicts of Interest:There are no conflicts of interest to disclose. The early repolarization pattern, consisting of a distinct J wave or J point elevation, a notch or slur of the terminal part of the QRS and an ST segment elevation, is predominantly found in healthy young males and has traditionally been viewed as benign 2, 3 . Our observation i...

Evaluation of Genes Encoding for the Transient Outward Current (Ito) Identifies the KCND2 Gene as a Cause of J-Wave Syndrome Associated With Sudden Cardiac Death

“…16 With an increase in I to (48%) in line with our experimental results from heterozygous expression of Kv4.2-WT/D612N, we observed complete and stable loss of the dome of the action potential in the epicardial layer. This observation predicts the formation of ECG J waves, as demonstrated by Antzelevitch and Yan, 14 and creates the risk of propagation of the action potential dome from sites where it is maintained to sites where it is lost, producing local reexcitation (phase 2 reentry) and generation of polymorphic ventricular arrhythmia. 12,13 Furthermore, the facilitation of heterogeneous action potential durations within the RVOT induced by Kv4.2-D612N may lead to relative delayed activation of epicardial regions, delaying depolarization in some regions and manifesting as late potentials or a fractionated QRS, as observed in our patient.…”

“…12 Exacerbation of this natural epicardial to endocardial gradient, either by increased outward current (I to , I K-ATP ) or decreased inward current (I Na , I Ca ), results in the manifestation of the ECG J wave and creates an arrhythmia substrate for arrhythmia (phase 2 reentry). 13,14 Based principally on remote gene expression studies using canine left ventricular tissue, the molecular correlates for I to have been deemed to predominantly involve the KCND3-encoded Kv4.3 channel, and KCHIP2, which encodes an accessory subunit required for channel function. 22,23 Traditionally, the role of the poreforming Kv4.2 subunit encoded by KCND2 has not been considered significant within human myocardium in light of these previous observations.…”

“…[12][13][14] Despite insight into this pathophysiology, knowledge of the genetic determinants of J-wave syndromes, aside from Brugada syndrome, remains scarce.…”