10 Mar 09
T-Wave alternans and the susceptibility to ventricular arrhythmias
By S Narayan
J Am Coll Cardiol. 2006;47:269:281
Sudden cardiac arrest (SCA) claims over 400,000 lives per year in the U.S. alone, predominantly from ventricular tachycardia (VT) or ventricular fibrillation (VF). Although prophylaxis with the implantable cardioverter defibrillator (ICD) is extremely effective, identifying individuals who should receive such therapy remains challenging. Certainly, reduced systolic function and heart failure are sensitive indices of SCA risk, yet they identify populations in whom arrhythmic event rates may be low. From an individual as well as a public health perspective, there is therefore an urgent need for more accurate indices of lethal ventricular arrhythmias.
T-wave alternans (TWA) is a promising electrocardiographic (ECG) index that measures beat-to-beat alternation in T-wave shape, amplitude, or timing. Decades of research now link TWA with inducible and spontaneous clinical ventricular arrhythmias, and with basic mechanisms leading to their initiation. This bench-to-bedside foundation makes TWA a very plausible index of susceptibility to SCA, and motivates the need to define optimal conditions for its detection and clinical populations in whom its potential can be realized.