羊とヒトの心臓刺激伝導系の比較

組織学的研究

抄録

Though the cardiac conduction system of sheep has been frequently used for electrophysiological experiments, yet a satisfactory morphological comparison between that of sheep and human had not been made. To clarify the difference, young adult male hearts of sheep and human were histopathologically studied for their conduction systems using Lev's serial sectioning method.
The sinus node of sheep is rounder in shape at cross section, the nodal cells are more concentrically arranged and it contains tighter connective tissue than that of human.
The atrioventricular nodes of sheep and human are similar in structure but the former has a fatty pad between the node and the central fibrous body (CFB), and the latter has fatty tissue covering its surface to the atrial muscle.
His' bundle in sheep consists of Purkinje type large cells and penetrates the CFB more centrally than that in human which consists of smaller cells. The special channels which are occupied with fatty tissue peretrate the CFB of sheep, and they resemble the dual His' bundles rerely observed in human congenital heart anomalies. At the top of the ventricular septum, a conal muscle cap over the bundle is observed in sheep but this phenomena is very rare in human except in case of Pokkuri disease.
The left bundle branch of sheep is a solitary narrow bundle consisting of Purkinje type cells, and contains tight connective tissue in and around the branch, whereas that of human is a fan-shaped broad bundle consisting of small cells and loose connective tissue. The right bundle branch in sheep is shorter, the branch cells are larger, and it has tighter connective tissue than that in human. In human, evidence that both the His' bundle and the bundle branch cells show signs pre- and post-blockade hypertrophy, suggests the possibility of transforming of the small conducting cells to Purkinje cells in pathologic situation.