ST-segment elevation in the early repolarization syndrome, idiopathic ventricular fibrillation, and the Brugada syndrome: cellular and clinical linkage

ST-segment elevation in a structurally normal heart is associated with an electrocardiographic (ECG) J wave, which can be observed in the early repolarization syndrome (ERS), idiopathic ventricular fibrillation (VF), and the Brugada syndrome. Animal studies have demonstrated that the J wave is the consequence of a transmural voltage gradient resulting from an I-to-mediated action potential notch (spike and dome) in epicardium but not endocardium. I-to-mediated spike and dome morphology predisposes loss or depression of the dome in epicardium, leading to ST-segment elevation. Despite the fact that 3 clinical syndromes share many common ECG features, their clinical consequences are remarkably different. The ERS is a benign ECG finding characterized by a distinct J wave and ST segment in left precordial leads V-4 through V-6. In contrast, idiopathic VF and the Brugada syndrome, characterized by a J wave and ST-segment elevation in the inferior and right precordial leads, respectively, are the leading causes for sudden cardiac death in young Southeast Asian males. The underlying mechanism for such a difference in clinical consequences among these syndromes is due to a difference in I-to density and I-to-mediated epicardial spike and dome. When I-to is prominent, complete loss of the dome may occur due to either a decrease in inward currents or an increase in outward currents, leading to phase 2 reentry capable of initiating VF as in idiopathic VF and the Brugada syndrome. When I-to is relatively small as in the ERS, partial depression of the dome occurs without the development of phase 2 reentry. (c) 2005 Elsevier Inc. All rights reserved.Cardiac & Cardiovascular SystemsSCI(E)CPCI-S(ISTP)5