Repolarization alternans: techniques, mechanisms, and cardiac vulnerability.
Sudden cardiac death continues to be the leading cause of mortality in developed countries. Electrical alternans of the ST segment and the T wave on the surface ECG as a noninvasive marker of patients at risk is a phenomenon that was initially observed early in this century and was seen then to be associated with cardiac rhythm disturbances. Substantial evidence indicates that T wave alternans (TWA) is related to myocardial ischemic as a harbinger of malignant ventricular arrhythmias because it reflects dispersion and heterogeneity of repolarization. Recent data have demonstrated a significant correlation between TWA and vulnerability to ventricular arrhythmias in individuals with or without organic heart disease, it also predicts the results of electrophysiological testing and arrhythmia-free survival in patients with a variety of cardiac diseases. This article reviews the historical background of TWA and discusses the early experimental and recent clinical evidence implying an integral link between TWA and ischemia-induced cardiac vulnerability.
Murda'h
M A
MA
Department of Cardiological Sciences, St. George's Hospital Medical School, London, United Kingdom.
McKenna
W J
WJ
Camm
A J
AJ
D000788:Angina Pectoris, Variant / Q000150:complications / Q000503:physiopathology; D001145:Arrhythmias, Cardiac / Q000175:diagnosis* / Q000209:etiology / Q000401:mortality; D002312:Cardiomyopathy, Hypertrophic / Q000150:complications / Q000503:physiopathology; D016757:Death, Sudden, Cardiac / Q000209:etiology*; D004562:Electrocardiography; D006333:Heart Failure / Q000150:complications / Q000503:physiopathology; D006801:Humans; D008133:Long QT Syndrome / Q000150:complications / Q000503:physiopathology; D017202:Myocardial Ischemia / Q000150:complications / Q000503:physiopathology; D012307:Risk Factors