Influence of Point at which Ventricle Contacts Thoracic Wall on Form of the Electrocardiogram

Abstract

The recent experiments of Katz, 1 Wilson, 2 and of Kountz, Prinzmetal and Smith 3 have indicated that the point at which the heart contacts the thoracic wall may play an important part in determining the character of the electrocardiogram. Especially the work of the latter authors has suggested that the point of the ventricle in contact with the chest wall, as well as the point on the chest wall where this contact is made, may have a profound influence on the resulting curves. It has also served to show that it is extremely difficult in the animal body to change the contact of the heart without changing its electrical axis. Since the influence of these changes has not been studied separately, the following method was devised.

A dog heart-lung preparation (Starling) was set up and removed from the dog's body. The thorax of a second dog, just dispatched, was opened anteriorly and the thoracic viscera left in situ. The esophagus of the heart-lung preparation was connected to a point 4 cm. to the left of the sternum on the anterior chest wall. On the heart-lung preparation a wire electrode which could be moved from place to place on either ventricle, was connected by a second wire to the esophagus in the opened thorax. In this way, a cardioelectric impulse arising in the heart-lung preparation was conveyed to the dog's body and recorded on the electrocardiograph by the 3 usual leads attached to the dog's body.

It was found that contact could be made with either ventricle of the heart-lung preparation without changing greatly the character of the normal QRS impulse. In the complexes the initial deflection of the galvanometer was always in the same direction. This was followed by a second deflection, which, when the left ventricle of the heart preparation was in contact, was tall (3mm.). When the right ventricle was in contact it was small. The second deflection of the galvanometer was always opposite in direction to the first; the following “T”wave was always in a direction opposite to its preceding second deflection.