Clinical importance of intramural blood vessels in the sino-atrial segment of the conducting system of the heart

Abstract

We studied the morphology and histology of intramural vessels in the sino-atrial [S-A] segment of the cardiac conducting system because of the clinical relevance of the anatomy of the microvascular system for those performing cardiac surgery or coronary angiography, cathetherization or arterialization. In 25 human and 25 canine hearts the vasculature was fixed by the Komahidze method, the anatomy was studied and sections were stained and studied by microscopy. Of clinical importance is a finding of considerable variation in the exact anatomy of the arterial supply. The sinonodal artery is a large artery originating from the right or left coronary arteries. In some cases the coronary arterial course could not be demonstrable by coronary angiography thus increasing the risk of coronary artery surgery at the site. Cross connections also permit the extracardiac circulation to supply the nodal tissue. The S-A node has a rich intramural network of anastomosing blood vessels which is of surgical importance in the case of damage and surgical procedures. The density of the capillary network in the node is greater than that in adjacent atrial tissue. The distribution and density of the smallest anastomotic blood vessels were different in various parts of the node, the capillary net was most dense in sections from dorsal parts of the S-A node. No marked differences were found when human and canine systems were compared. Canine preparations could be used for analysis of the S-A node vascularization because of their similarity to the human heart. These findings are clinically relevant to the S-A node dysfunction that may follow cardiac surgical procedures. Surgeons should be aware that there is considerable variation in the exact anatomy of the arterial supply of the S-A node which might be important for cardiological examination and treatment (cardiac surgery, coronary angiography, etc.).