Spatial vectorcardiogram in dogs with chronic localized myocardial lesions

¹ Department of Medicine, Tulane University School of Medicine, Charity Hospital of Louisiana; Department of Engineering, Tulane University; and Veterans Administration Hospital, New Orleans, Louisiana

Small discrete ventricular myocardial lesions were produced in 20 of 21 dogs by injecting 0.4 cc of formaldehyde into selected sites of the left ventricle. Serial electrocardiograms and spatial vectorcardiograms were obtained up to 14 weeks after placement of the lesions. Generally, changes in the spatial vectorcardiograms and electrocardiograms were transient; characteristic changes of loss of myocardium persisted in only seven dogs. Six of these had sVCG or EKG changes characteristic of loss of muscle of the posterior wall of the left ventricle. Isolated destruction of the basal two-thirds of the anterior papillary muscle ultimately produced electrocardiographic and spatial vectorcardiographic patterns of loss of muscle in the posterior wall of the left ventricle. Although there were minor changes in magnitude and configuration of the QRS sÊ-loop in all dogs following injury to the myocardium, the major changes usually developed more slowly (several hours to days). The slight QRS changes were more evident in the vectorcardiogram than in the electrocardiogram because the process is recorded in greater detail in the former.