Right Aortic Arch with Report of Eight Cases

Abstract

Right aortic arch has long been known in the anatomical literature as a rare congenital defect of the aorta. Maude Abbott (1) lists 13 instances of this abnormality in her collection of 1,000 cases of congenital heart disease. Garland (2), in 1938, was able to collect from the literature the records of 113 cases. It is only Since 1926, however, when the criteria for the roentgen diagnosis of this condition were laid down by Arkin (3) and by Renander (4), that it has become possible to diagnose this congenital defect during life. In 1939 Metzger and Ostrum (5) reported its recognition roentgenologically in 18 patients, to which series they added 2 cases of their own. Anatomy There are two varieties of right aortic arch. In the simple or anterior type, the aortic arch loops over the right main bronchus and then passes straight downward, the transverse arch being anterior to the trachea and esophagus as in the normal subject. This type is uncommon; it is rarely encountered in the roentgen literature and will not be discussed in this paper. In the posterior or retro-esophageal type (Fig. 1), to which all of our cases belong, a more complicated course is followed. After passing over the right main bronchus, the transverse arch takes a turn to the left behind the esophagus, It then swings to the right and descends as a rule slightly to the right of the midline. From the ascending portion of the arch, before it passes over the right bronchus, the left subclavian branches off from a common trunk with the left common carotid and passes to the left, in front of the trachea. From the anterior surface of the descending arch, after it has emerged to the left from behind the esophagus, there arises a diverticulum which is joined to the left subclavian artery by a short obliterated vessel. With this arrangement the trachea and esophagus are surrounded by a complete vascular ring, the tightness of which presumably determines whether or not compressive symptoms will arise, This peculiar vascular arrangement in front of the trachea is regarded by Arkin as the formative structure of the left aortic arch, the obliterated vessel connecting the left subclavian artery with the left pulmonary branch representing an isthmus stenosis. He considers this type of right aortic arch as essentially a double aorta, representing a throw-back to the reptilian type of heart. Embryology For a proper understanding of the bizarre anatomical picture, it is necessary to review briefly the development of the aortic arch (Fig. 2). In the 4–5-week embryo the blood leaves the primitive two-chambered heart by a single vessel, the truncus arteriosus, which soon divides into two branches, the ventral aortae. These are connected by six branchial vessels with the paired dorsal aortae. Of pertinent interest is the subsequent development of the fourth branchial arches.