Variability of the body surface distributions of QRS, ST-T and QRST deflection areas with varied activation sequence in dogs

Distributions of QRS, ST-T and QRST areas of 192 lead body surface ECG's were measured in dogs for multiple activation orders. Qualitatively, the distributions of QRST area were found to be strikingly similar over all activation orders in contrast to the distributions of QRS or ST-T areas. Quantitative results showed that variability of the QRST areas over all activation orders was consistently less than those of either QRS or ST-T. The factor responsible for the QRS deflection is ventricular activation sequence while those responsible for the ST-T deflection are both activation sequence and ventricular recovery properties. Since the total QRST deflection area was largely independent of activation sequence it is likely the quantity is an index of ventricular recovery properties. The significance of this relation is that QRST deflection area may permit evaluation of intrinsic ventricular recovery properties in the presence of abnormal ventricular activation as occurs with intraventricular conduction disorders and ectopic origin of excitation. Evaluation of intrinsic ventricular recovery properties may also permit recognition of states at risk of ventricular arrhythmias due to increased disparity of these properties.