[QT Variability Index as a tool for risk stratification of sudden cardiac death]

Sudden cardiac death is the leading cause of mortality in patients with chronic heart failure (CHF) and history of myocardial infarction. Selection of patients at risk of sudden cardiac death is dramatically important to choose the correct therapeutic approach. The QT Variability Index (QTVI) is a non-invasive measure of repolarization lability that has been applied to a wide variety of subjects with cardiovascular disease. It is a ratio of normalized QT variability to normalized heart rate variability, and therefore includes an assessment of the autonomic nervous system tone. As opposed to T wave alternans, QTVI assesses variance in repolarization at all frequencies. Recent studies suggest that QTVI may help clinicians choosing the appropriate implantable cardiovester defibrillator timing implantation, in patients with dilated or hypertrophic cardiomyopathy or CHF because of its efficacy in patient evaluation and follow-up.