Embryology

Two theories of embryologic development of coarctation include the flow theory and the ductal sling theory. The flow theory was postulated by Rudolph and colleagues who observed a group of neonates with aortic narrowing.[1] They observed that narrowing of the isthmus was commonly associated with intracardiac lesions, especially lesions with intracardiac shunts, which led to less antegrade aortic flow during development. In addition, they observed that those patients with discrete juxtaductal narrowing had a lower incidence of intracardiac lesions, and such narrowing becomes physiologically significant upon closure of the ductus. A lower incidence of aortic narrowing with right-sided lesions (e.g., tetralogy of Fallot) was also later observed and provided further support for this theory.[2]

The ductal sling theory holds that abnormal extension of ductal-derived or ductal-related smooth muscle cells constrict and fibrose causing circumferential, shelf-like narrowing of the aorta independently of intracardiac anatomy.[3],[4],[5] Ductal tissue has also been found to extend beyond the juxtaductal region into the descending aorta and proximally into the isthmus.[6],[7]