The surgical anatomy of the conduction tissues.

On the basis of our collective experience we have reviewed the disposition of the cardiac conduction tissues as they might be observed by the surgeon in both normal and abnormal hearts. The sinus node lies subepicardially in the terminal sulcus; because of its variable blood supply the entire superior cavoatrial junction is a potential danger area. There are no morphologically discrete tracts extending through the atrial tissues between sinus and atrioventricular nodes. The atrioventricular node, the atrial extent of the atrioventricular conduction axis, is contained exclusively within the triangle of Koch. The axis penetrates through the central fibrous body and branches on the muscular ventricular septum immediately beneath the interventricular component of the membranous septum. The landmarks to these structures are described as they might be seen through the right atrium, left atrium, and aorta. Consideration is then given to the surgical anatomy of the abnormal muscular atrioventricular connections that underscore the ventricular pre-excitation syndromes. Finally, rules are developed whereby the disposition of the conduction tissues can be predicted with accuracy in congenitally malformed hearts, in the settings of both normal and abnormal chamber connections. The most important variables in this respect are alignment between the atrial and ventricular septal structures and the pattern of ventricular architecture present.