Vectorial interpretation of the ventricular complex in Wolff-Parkinson-White syndrome

Abstract

A vectorial analysis of twenty-seven electro-cardiograms showing the Wolff-Parkinson-White syndrome found among 31,822 (0.085 per cent) tracings was made. By taking into consideration the delta wave vector orientation (SÂΔ) the cases were classified in two types: 1. WPW syndrome, type I, showing positive delta waves in lead V 2 (SÂΔ with a forward orientation) with SÂQRS pointing either forward or backward: and 2. WPW syndrome, type II, characterized by a negative pre-excitation component in lead V 2 (SÂΔ oriented backward). Based upon previously published experimental studies and considering the spatial orientation of the SÂΔ, we believe that the area of pre-excitation is probably located at the posterior septal and ventricular regions in the WPW syndrome, type I and at the right and anterior sites of the interventricular septum and right ventricle in cases of the WPW syndrome, type II. The average of the spatial angle between SÂQRS and SÂΔ showed a small magnitude (34.7 degrees), with a minimum angle of 10 degrees and a maximum angle of 90 degrees. This finding suggests that the electrical forces developed during the premature excitation may influence the orientation of the total ventricular activation. Five of six patients showing the WPW syndrome, type I, with large S waves in leads V 1 and V 2, were associated with left ventricular hypertrophy. Nine of eleven patients presenting positive T waves not opposed to the ventricular complexes in the left precordial leads had normal hearts; but all patients whose electrocardiograms showed negative T waves in leads V 6 and V 7 presented cardiopathies with left ventricular overloading. Finally, we call attention to the possibility of having the WPW syndrome with Q waves in leads V 6 and V 7 related to a particular orientation of SÂΔ.