Analysis of QRS loop changes in the beat-to-beat Vectocardiogram of ischemic patients undergoing PTCA

In the present work, we have studied dynamic changes of QRS loop in the vectocardiogram (VCG) of 80 patients that underwent percutaneous transluminal coronary angioplasty (PTCA). The VCG was obtained for each patient using the XYZ orthogonal leads of their electrocardiographic (ECG) records acquired before, during and after PTCA procedure. In order to analyze the variations of VCG, it has been proposed in this study the following parameters a) maximum module of the cardiac depolarization vector, b) volume, c) and area of vectocardiographic loop corresponding to the QRS complex of each beat, d) maximum distance between centroid and the loop, e) angle between the XY plane and the optimum plane, f) relation between the area and perimeter. The results obtained indicate that the parameters proposed show significant statistics differences (p-value<0.05) before, during (with some exceptions at the first minute of balloon inflation) and after PTCA. We conclude that the variations observed in the proposed parameters correctly represent not only the morphological changes in the depolarization VCG but also they reflect the modifications in the levels of cardiac ischemia induced by PTCA.