Spatial Vectorcardiography in the Wolff‐Parkinson‐White Syndrome: Correlation with Epicardial Mapping Findings

The spatial vectorcardiograms (VCG) of 13 patients with WPW syndrome due to single accessory pathways were analyzed and correlated with the excitation analysis obtained on epicardial mapping. The azimuth angle of the initial 10 ms cardiac vector was > + 90° (directed right and anteriorly) in patients with a left ventricular free wall; it ranged between 0° to 90° (left and anteriorly) in those with a left or right paraseptal free wall and was ‐ 30° (left and posteriorly) in one patient with a right ventricular free wall location. The elevation angle of the initial 10 and 20 ms cardiac vector was either zero or positive (inferiorly directed) in those with right and left ventricular free wall pathway. Among six patients with a paraseptal location, the elevation angle was negative (superiorly directed) in four and positive in two. Both the patients with a clockwise inscription of a QRS loop in the horizontal plane (HP) had pathways located to the left ventricle. Among the paraseptal group, at surgery, the accessory pathway could not be excised in two in spite of dissection very close to the IV (interventricular) septum. The elevation angle in both these patients was markedly negative (‐45° and ‐62°) in contrast to the other in whom surgical excision was successful. We thus conclude: 1) an azimuth angle of the initial 10 ms vector of more than 90° indicates early activation in the left ventricular free wall and less than 0° on the right ventricular free wall; 2) presence of a negative elevation angle [superiorly directed) of the initial 10 and 20 ms vector suggests a paraseptal location; 3) a markedly negative elevation angle may further indicate that the accessory connection is located very close to, or in, the IV septum.