EDITORIAL The frontal plane QRS-T angle

This editorial refers to ‘QRS-T angle as a predictor of sudden cardiac death in a middle-aged general population’ by A.L. Aro et al., on page 872 Availability of the limb leads of the 12-lead electrocardiogram (ECG) allows calculation of a mean QRS axis and a mean T axis, as is well known. These axes lie in the frontal plane of the body and can be used to calculate a very simple difference in angle between the two axes, namely the planar QRS-T axis. In contrast, it is possible to calculate the mean direction of ventricular activa-tion in three-dimensional space. This is sometimes termed the orientation of the mean spatial QRS vector. Similarly, there is a mean spatial T vector and the science of vectorcardiography revolves around the study of spatial P, QRS, and T vectors as they vary throughout the cardiac cycle.1 Figure 1 shows a mean spatial QRS and T vector and their corresponding projection