Cardiac Electrophysiology Review

QT dispersion (QTd) has not proven to be a useful marker derived from the 12-leadelectrocardiogram (ECG) for stratification of patients at risk for sudden cardiac death. To overcomeits methodological shortcomings, novel ECG variables of T wave morphology have been proposed. The total cosineR-to-T (TCRT), T wave morphology dispersion, T wave loop dispersion, normalized T wave loop area, aswell as absolute and relative T wave residuum evaluating non-dipolar ECG signal contents were evaluated in twoclinical studies involving post myocardial infarction (MI) patients and US veterans with cardiovasculardisease. In 280 post MI patients with 27 events over a mean follow-up of 32 months, TCRT and T wave loop dispersionwere independent predictors of mortality. In 813 male US veterans with cardiovascular disease the absolute andrelative T wave residua were independent predictors of patient risk during a long-term follow-up of more than 10years. On Cox regression analysis, age, presence of left ventricular hypertrophy (LVH) and leftventricular ejection fraction (LVEF) were also predictors of survival. The latter study in US veteranstherefore was the first to demonstrate that a novel parameter characterizing heterogeneity of ventricularrepolarization within the 12-lead surface ECG permits risk stratification in patients with cardiovasculardisease. All of the ECG variables are easily accessible from digital 12-lead surface ECG recordings using customcomputer programs. They may prove useful to identify risk patients that benefit from the implantablecardioverter-defibrillator (ICD).