The Effect of Coronary Occlusion upon the Initial Phase of the Ventricular Complex in Precordial Leads.

In electrocardiograms of normal human hearts recorded by precordial leads the initial ventricular complex shows a fairly constant configuration. With the right arm electrode placed at the apical region and the second electrode at any point distant from the heart the primary ventricular deflection consists of a conspicuous downward deflection followed by an upward deflection. The initial downward deflection which is constantly present in normal controls entirely disappears or becomes conspicuously smaller after infarction involving the apex, lower anterior and lateral portions of the left ventricle 1 (8) (10) (11). Moreover, the initial downward deflection is influenced by the position of the anterior electrode as well as by pathological changes within the heart, decreasing in amplitude and even disappearing as the electrode moves from the apex toward the base of the heart. The electrocardiogram of the dog and the cat. obtained by precordial leads is similar to that observed in the human. AMoreover, the influence of change of position of the anterior electrode resembles that occurring in man. Because of this similarity and because the use of animals allows the changes to be studied at frequent intervals from the verv moment of muscle injury until repair and recovery have reached their maximum, we have used these animals to study the effects of nmvocardial infarction upon the initial downward deflection of precordial leads. In general, the experiments fall into two groups (1) acute and (2) survival experiments. In the former, the effect of muscle injury produced by ligation of different coronarv arteries, or the damage resulting from the application of a cautery directly to the heart muscle upon the initial downward deflection was observed over a period of about two hours. In the survival experiments, coronary arteries were ligated and the electrocardiographic change followed over a period of months. The purpose of this paper is to record the results of experiments in dogs