A Morphological Study on Localization of the Sinoatrial Node and Its Arterial Supply in Dogs

Abstract

To elucidate the localization and arterial supply of the sinoatrial(S-A) node in the dog, 10 adult dogs (9-35 kg in body weight) were selected, at random, from among those necropsied in the Department of Veterinary Pathology, Tokyo University of Agriculture and Technology. By postmortem coronary arteriography, the heart was observed for the arterial supply to the S-A node by preparing a transparent specimen of the right atrium. Finally, the S-A node and its artery were examined histologically.
The S-A node, which seemed to have the shape of a cone, was located along the sulcus terminalis. It was approximately 12×3×1 mm in size. Its head or the base of the cone, laid at the junction of the cranial vena cava and the intermediate between the anteromedial and anterolateral wall of the right atrium. Its tail, or the apex of the cone, terminated in the middle part of the free lateral wall of the right atrium.
When the angiogram and transparent specimen was observed, the artery to the S-A node originated from both left and right coronary arteries in 8 of the 10 dogs, from the left artery in one dog, and from the right artery in the other dog. In addition, there were often interarterial coronary anastomoses in the S-A node area. As for the localization of the S-A node and its artery, the S-A node artery ran along the vicinity of the node(extranodal artery). In a few dogs, a part of the node had an intranodal artery which was regarded as a type of so-called central artery.