Experimental Investigation of Electrocardiogram in the boat

Abstract

NÖRR first introduced electrocardiography to horses in 1913. Since then, various attempts have been made by many investigators to apply it to clinical veterinary medicine. Between man and domestic animals, there are many differences in the anatomy of the heart and thorax, especially the location of the heart in the thoracic cavity. So there were many problems to be solved until electrocardiography, originally developed for man, could be applied to domestic animals. To begin with, NÖRR (1913) and KAHN (1913) indicated the irrationality of applying the lead systems established for human electrocardiography to horses. Subsequently, various lead systems were developed by many investigators in animal electrocardiography. None of them, however, were internationally standardized as yet. So far as the excitation-conducting system is concerned, KISCH et al. (1948) studied direct lead electrograms of calves. They concluded that the excitation was directed from the epicardium to the endocardium of the ventricular free wall of the calf, while it was directed reversely from the endocardium to the epicardium of the ventricular free wall of man and the dog. SPÖRRI et al. (1956) studied direct lead electrograms of horses and cattle. They reported that the excitation was directed from the epicardium to the inner layer of the ventricular myocardium in some areas and from the endocardium to the inner layer of the ventricular myocardium in others. DÜRRER et al. (1957) studied direct lead electrograms of goats. They observed that the epicardial and the endocardial surface were excited almost simultaneously in the left ventricle. BEDDING (1957) studied direct lead electrograms of sheep. He assumed that there was almost simultaneous excitation in all areas of the left ventricle, except a small apical epicardial area and a small area of the extreme base. SUGENO et al. (1959, 1960, and 1964) studied direct lead electrograms of cattle, goats, and horses. They suggested that the ventricular activation process in them might be quite different from that of man and dogs. HAMLIN et al. (1961) studied direct lead electrograms of goats. They reported that all areas of the ventricle, except a small apical epicardial area and a small area of the base, were excited almost simultaneously. Thus it was indicated by many investigators that the ventricular excitation process in ungulates was quite different from that of man and dogs. Further details of the process, however, are still unknown. Especially, there were few reports regarding the derivation of the body surface potentials. In the present investigation, this author studied unipolar precordial lead electro-cardiograms, vectorcardiogams, direct lead epicardiograms, intracavity lead electrograms, and the location of the heart in the thoracic cavity, and determined the ventricular excitation process and derivation of the body surface potentials in goats, which were chosen because of their convenience to handle among ungulates.