The Ductus Arteriosus, a Vascular Outsider, in Relation to the Pulmonary Circulation

The muscular ductus arteriosus (DA) has many unique characteristics setting it apart from the adjoining elastic arteries. Preparation for neonatal closure takes place in utero with the development of intimal thickening. Ductus-specific gene and protein expression patterns were demonstrated during this process. We postulated that the closing process, with increased expression of progerin, might reflect aspects of premature ageing. Persistent patency of the DA, can be congenitally or immaturity based. During embryonic development the sixth pharyngeal arch arteries are the last to develop. In avian embryos this arch is divided into a proximal (part of the future pulmonary artery) and a distal part (on the left side the origin of the DA). The consequence is that the pulmonary arteries have a double vascular contribution being a proximal sixth arch artery component and a distal true pulmonary artery segment. We have conclusive evidence that this is not encountered in the human embryo. Both sixth arch arteries and the right and left pulmonary arteries connect separately and at distinct locations to the pulmonary trunk side of the aortic sac. The insertion of the wall of the DA between the proximal and distal part of the left pulmonary artery, referred to as pulmonary coarctation, constitutes a congenital malformation and not a remnant of what is encountered during normal development. This configuration is found almost exclusively in combination with pulmonary atresia leading to neonatal interruption of the proximal left pulmonary artery with consequences for surgical or intervention repair.