The origin of both the QRS and T-wave loops for the identification of the QRS and T-wave vectors is taken at v0=v(t0), where t0=QRSON. The QRS and T-wave loops are then defined by vectors:

The peak vectors vQRSmax and vTWmax are defined as those associated with the largest magnitude, i.e. vQRSmax=vQRStm, with tm=arg(max(vQRS(t))), and vTWmax=vTWtm, with tm=arg(max(vTW(t))). The mean vectors vQRSmean and vTWmean are measured as the temporal mean of vQRSt and vTWt. The spatial peak QRS-Ta, (αP), is measured as the angle between vQRSmax and vTWmax while the spatial mean QRS-Ta, (αM), is measured as the angle between vQRSmean and vTWmean.