[Left aortic arch without a circumflex segment and a right descending aorta: a hypothetical case and a real example].

We studied a case of a patent left ductus arteriosus, with a left aortic arch connected to a right descending aorta without an aortic circumflex (retroesophageal) segment. We believe this is the first world-published example of this--so far--hypothetical anomaly, included in Kirkling and Edwards classification of vascular rings. The case was a 27-year-old deaf-mute female patient with a patent left ductus arteriosus, with important left to right shunt and moderate pulmonary arterial hypertension who underwent a successful closing surgical procedure. In the aortographic study a left (normal) aortic arch was seen, which after giving off a large left ductus arteriosus, crossed to the right and connected to a right descending aorta. In the upper part of the thorax the esophagus and trachea were displaced to the right by the left aortic arch. The esophagus in the middle and the upper inferior parts of the thorax was also displaced to the right by the descending right aortic segment. Complete vascular ring was not evident. The case--although without clinical importance--reinforces the pathogenic concept of the Rathke diagram of a complete double aortic primitive arch originating the pulmonary and supraaortic vascular structures which are formed by the obliteration or disappearance of particular segments of the structure. This knowledge explains the embryogenesis of these complex anomalies. Our case is believed to be formed by the very early disappearance of a frontal portion of the primitive left dorsal aorta.