Relationship Between the Anatomical Orientation of the Interventricular Septum and the Manifest Orientation of Ventricular Depolarization in Dogs

Abstract

Exact anatomical orientation of the interventricular septum was compared with apparent direction of electrical activity during ventricular depolarization in 22 dogs. In 15 control animals, the mean orientation of a vector normal to the right septal surface was toward the front, to the right, and slightly headward. The mean orientation of the 10-msec. vector (QRS) was almost directly toward the front and slightly tailward. The mean orientation of the polar vector was to the left, slightly to the front, and slightly headward. The values for each of these means were obtained in spherical coordinates: anatomical vector--141.7 degrees azimuth, 20.2 degrees altitude; 10-msec. vector (QRS)--92.0 degrees azimuth, -9.4 degrees altitude; and polar vector--14.8 degrees azimuth, 20.0 degrees altitude. In 7 dogs, rotation of the heart to the right by means of previously implanted guy sutures consistently moved the 10-msec. vector to the right also, but there was simultaneous unpredictable deviation either headward or tailward of the electrical vector. Polar vector shift was not consistent. Rotational transformation of axes for each dog, bringing the vector of the right septal surface into coincidence with the negative X-axis, did not bring to a focus the scatter of orientations of either group of electrical vectors, indicating that variation in electrical position depends upon other factors in addition to variation in anatomical position.