QT dispersion and heart rate variability in sudden death risk stratification in patients with ischemic heart disease

The aim of the article is to review the literature data about the significance and problems of the QT dispersion and heart rate variability in sudden death risk stratification in patients with coronary heart disease. QT dispersion is defined as the difference between the longest and the shortest QT intervals as measured in the 12-lead electrocardiogram. A direct relationship between the prolongation of QT dispersion and myocardial ischemia has been reported by several authors. Our previous study showed that QT dispersion assessed immediately after bicycle exercise test was significantly higher in patients with coronary stenoses of > 50% as compared to the patients without coronary artery disease. Despite some controversial data, several studies showed that QT dispersion is a significant predictor of cardiovascular mortality. Heart rate variability representing a relationship between the autonomic nervous system and cardiovascular mortality, including sudden cardiac death, is one of the most promising markers. The predictive value of heart rate variability is independent of other factors established for postinfarction risk stratification, such as depressed left ventricular ejection fraction, increased ventricular ectopic activity, and presence of late potentials. For prediction of all-cause mortality, the value of heart rate variability is similar to that of left ventricular ejection fraction, but heart rate variability is superior to left ventricular ejection fraction in predicting arrhythmic events (sudden cardiac death and ventricular tachycardia).