The medial wall of the right atrium.

ALTHOUGH gross anatomic studies are frequently considered to be outmoded and outdated, we believe that because of its present practical importance a renaissance of the clinical anatomy of the heart1 is long overdue. Increasing interest in the group of lesions responsible for the somewhat controversial condition at present called "obstruc-tive cardiomyopathy" or "subaortic stenosis" has already prompted us to review the anatomy of the left ventricular outflow tract2 in the belief that much of the current discussion about function and angiocardiographic appearances pays too little attention to the structural features of the region. The relationships of the heart and great vessels have, moreover, assumed a new clinical significance as a result of many intracardiac procedures now routinely performed in operating theaters and diagnostic laboratories. Certain palliative3 and radical4' 5 operations in patients with transposition of the great vessels, for example, involve removal of part of the interatrial septum, and transseptal punc-ture6-8 offers a convenient route of entry from the right atrium into the left heart. Such procedures require a detailed and accurate knowledge of the clinical anatomy of the heart, and this current interest in the inter-atrial septum suggested that it might also be helpful to reexamine the medial wall of the right atrium: especially as the terms "inter-atrial septum" and "medial wall of right atrium" cannot in our view be regarded as synonymous. Some years ago Walmsley9' 10 stressed the importance of naming cardiac structures with more regard to their position in the living body and suggested that gross anatomy should 400 be more concerned with the heart in situ. Cardiac terminology has a long and complicated history, and in this communication no attempt will be made to review or discuss it except insofar as is appropriate to the right atrium and the structures related to its medial wall as they have been shown to exist both in the living and the dead. During early fetal life the heart rotates around a vertical axis so that the anterior (or sternocostal) attachment of the interven-tricular septum is displaced increasingly to the left while the posterior attachment of the interatrial septum is carried to the right. The interventricular and interatrial septa are approximately in the same plane and reach the adult angulation of about 450 to the median plane about midway through fetal life. From this time onward each atrium lies behind and to the right of its corresponding ventricle (fig. …