Atrial depolarization in Wolf-Parkinson-White and Lown-Ganong-Levine syndrome: vectorcardiographic features.

The atrial depolarization pattern was studied in 22 patients with Wolff-Parkinson-White and Lown-Ganong-Levine syndrome. The influence of the accessory pathways on the shape, magnitude and conduction pattern of the PSE loop was analyzed. An accurate evaluation of the beginning of the delta wave and of the P loop distortions was obtained by using high magnification (1 mV = 30 cm) recordings. The Frank lead system was used. The influence of atrial size (documented by echocardiography) on the PSE loop is emphasized. Special attention has been focused on the terminal vectors as compared to a control group. In Wolff-Parkinson-White syndrome the size of the PSE loop was smaller than in Lown-Ganong-Levine syndrome or in the normal group. When atrial conduction disturbances and/or atrial enlargement was present the PSE loop was larger and distorted. The terminal vectors were abnormally oriented in 75 percent of the patients with Wolff-Parkinson-White syndrome, but only in one with Lown-Ganong-Levine syndrome. The beginning of the delta wave in patients with Wolff-Parkinson-White syndrome was located to the left of the E point in all but two. When the "concertina" effect was present, the direction of the terminal vectors remained unchanged. In four patients with the Lown-Ganong-Levine syndrome, the PSE loop closed, and in three patients, a small opening was present. We suggest that the changes in contour, duration and amplitude of the PSE loop are due to an abnormal pattern of atrial depolorization in Wolff-Parkinson-White syndrome.