Last update:
12-Mar-2009

The early detection of patients with increased risk of developing arrhythmia is an everyday necessity for the clinician. Ventricular depolarization or repolarization abnormalities play an important role in arrhythmiogenesis and have been shown to carry prognostic value for various patient groups. However, the role of noninvasive detection of the risk of developing arrhythmia is not well defined. The studies of the electrophysiological activity of the myocardium have been focused exclusively on the study of QT interval and its parameters. The electrophysiological meaning of the prolongation of the QT interval and its dispersion has recently being doubted and it has been supported that it does not predict the risk of arrhythmiogenesis, but reflects physiological variations in T loop morphology. In conclusion, there is an urgent need for the study of new prognostic markers of cardiovascular morbidity that will permit their application in high-risk populations and will assist in their inclusion for an early and a more intensive prevention treatment. Recent population-based studies revived the interest of the medical community for clinical vectorcardiography, and specifically for the spatial QRS-T angle, a new vectorcardiographic marker, defined as the angle between the maximum vector of the QRS complex (direction of the ventricular depolarization) and the maximum vector of the T wave (direction of the ventricular repolarization). In comparison with the classical electrocardiographic markers, its power lays in the ability to consider both the ventricular depolarization and repolarization and to assess therein the nondipolar factors that contribute to the QRS complex and the T wave, that reflect the local heterogeneity in the ventricular depolarization and repolarization of the myocardium. Prospective studies have recently shown that it is a strong and independent predictor of cardiac morbidity and mortality (including sudden cardiac death). It has been suggested that high spatial QRS-T angle values may reflect subclinical damaged areas of the myocardium that could distort the normal spread of electrical forces through the myocardial wall. As a result, subjects with an abnormal spatial QRS-T angle may be prone to lethal ventricular arrhythmias. Recent studies suggest that spatial QRS-T angle is a strong and independent prognostic marker of cardiovascular events in the general population and in subjects where classical electrocardiographic parameters failed to prevent a fatal outcome. The prognostic value of the spatial QRS-T angle for cardiovascular morbidity and mortality was found to be independent of other cardiovascular risk factors. This review focuses on the history of clinical vectorcardiography and evaluates the classical electrocardiographic markers and the newer vectorcardiographic ones in their ability to establish the risk for arrhythmiogenesis in various high risk population groups.

Key words: Arrhythmiogenesis, Clinical vectorcardiography, Diabetic cardiomyopathy.