Non-invasive localization of the pre-excitation site in patients with the Wolff-Parkinson-White syndrome. Vectorcardiographic and echocardiographic correlations.

Abstract

Vectorcardiographic and echocardiographic correlations were made in 160 patients with no clinical evidence of cardiovascular diseases except for the Wolff-Parkinson-White syndrome. Frank vectorcardiographic classifications of the patients were based on both the morphology of the delta loop and the direction of the mean delta vector in the horizontal plane as follows; group I (93 patients) with a delta loop inscribed nearly straightly anteriorly and either to the left or right and a mean delta vector directed more anteriorly than +20 degrees, group II (31 patients) with a hook-shaped delta loop inscribed initially anteriorly but soon posteriorly and to the left, and group III (36 patients) with a delta loop inscribed nearly linearly to the left and either posteriorly or slightly anteriorly and a mean delta vector directed more posteriorly than +20 degrees. Abnormal echocardiographic patterns of ventricular contractions in the syndrome were seen at the left ventricular posterior wall (LVPW), the interventricular septum (IVS), and the right ventricular anterior wall (RVAW). In group I abnormal LVPW motions were observed in 91 patients (98%), and both abnormal LVPW and IVS motions in 1. The remaining 1 showed no echocardiographic abnormalities either at LVPW or IVS. In contrast, abnormal IVS motions were observed in 29 patients (94%) of group II. No patient of group II showed abnormal LVPW motions. In 17 patients (47%) of group III abnormal LVPW motions alone were observed. Two patients showed both abnormal LVPW and IVS motions. In the remaining 17 patients (47%), no abnormal motions were noted either at LVPW or IVS. Abnormal RVAW motions were invariably observed in 19 patients of group II with satisfactory RVAW echograms, but never seen in groups I and III. Above findings could be explained by the pre-excitation at LVPW in group I, RVAW in group II, and posterior right ventricle in group III. In 19 patients (8 in group I and 11 in group III) frontal QRS loops were very similar to that in left anterior hemiblock. All of these patients except for 1 showed abnormal LVPW motions, so that the site of pre-excitation was presumably located at the posterior paraseptal region or the posterior IVS. Three cases with a combination of a frontal QRS loop of left anterior hemiblock pattern and abnormal IVS motions in addition to abnormal LVPW motions may be explained by the pre-excitation at the right-sided IVS near LVPW. We feel that combinations of vectorcardiographic and echocardiographic approaches are clinically quite useful as an auxiliary non-invasive means of locating the pre-excitation site.