Abnormalities of the Ductus Arteriosus and Pulmonary Arteries

Abstract

The ductus arteriosus is a normal vascular structure in mammalian embryos that connects the main pulmonary artery (MPA) with the descending aorta or a subclavian artery. In left aortic arch the ductus arteriosus inserts into the proximal descending aorta at its junction with the aortic isthmus, distal to the origin of the left subclavian artery. In right aortic arch the ductus arteriosus can connect the right descending aorta with the MPA (right-sided ductus arteriosus), the proximal left subclavian artery with the MPA (left-sided ductus arteriosus), or both (bilateral ductus arteriosus). In the fetus, the ductus arteriosus carries blood from the right ventricle (RV) to the aorta, bypassing the high-resistance pulmonary vascular bed. Normally, the ductus arteriosus closes during the first day of life. Persistent ductal blood flow beyond the newborn period is termed patent ductus arteriosus (PDA). IncidenceThe incidence of PDA varies considerably depending on the postnatal age of subjects and their degree of prematurity. PDA is common in preterm infants and is considered a functional abnormality as opposed to a structural congenital cardiac anomaly. In term infants the normal ductus arteriosus may stay open for several days after birth. Echo-Doppler studies in healthy newborns have shown functional closure of the ductus arteriosus in almost all subjects by 4-7 days after birth [1,2]. Based on analysis of 40 published articles spanning several decades, Hoffman and Kaplan estimated the median incidence of PDA in term infants at 56.7 per 100 000 live births [3]. EtiologyThe etiology of isolated PDA in full-term infants older than 1 week is not known. Recent investigations have identified the genes affecting the development of the fourth and sixth pharyngeal arches, and noted their association with cardiovascular defects similar to those observed in DiGeorge syndrome [4]. Morphology Developmental considerationsThe normal anatomy and congenital malformations of the ductus arteriosus and branch pulmonary arteries are rooted in the development of the embryonic sixth aortic arches (see Chapter 30). The embryo has two dorsal aortas, which communicate with the ventrally located aortic sac via several pairs of branchial arch arteries. During development, there is an orderly appearance and regression of six pairs of primitive aortic arches. The fate of the fourth and sixth arches is most important to the topics covered in this chapter. The left fourth arch persists as the distal left aortic arch between the left common carotid and left subclavian arteries, and the left dorsal aorta persists to become the segment that extends between the left subclavian artery and the site of the entrance of the ductus arteriosus. The right fourth arch becomes the brachiocephalic trunk and proximal right subclavian artery, whereas the right dorsal aorta largely involutes. The proximal portions of the right and left sixth arches form the proximal right and left pulmonary arteries, respectively. The distal right sixth arch regresses, whereas the...

A proposed method to visualize the ductus arteriosus on transesophageal echocardiography

“…[2] Arising from the posterosuperior aspect of the junction of the pulmonary trunk and the LPA it then courses posteriorly and slightly leftward to join the aorta at its isthmus. The LPA arises from the pulmonary trunk in the concavity of the aortic arch in front of the left main bronchus, is attached to the undersurface of the aortic isthmus by the ligamentum arteriosus (the obliterated DA) and then quickly spirals over the top of this bronchus to reach the back of the airway and the hilum of the left lung [5] and because of the intervening left bronchus imaging of the LPA on TEE is often the echo cardiographer's Achilles heel.…”

“…[10] Our alternative perspective is also validated by the need to obtain a "high" parasternal short axis ("ductal") view rather than a standard parasternal short axis view in trans-thoracic imaging of the DA; this view optimally traces the pulmonary artery bifurcation and the descending aorta simultaneously. [2] In the variegated landscape of congenital heart disease, there is a subset of patients who will have a large ductus, but with reversal of flow (from right to left) in which case the ductus can easily be confused with the flow in either the pulmonary artery or the proximal descending aorta; [2] since our proposed view simultaneously views both the descending aorta and the origin of the LPA it could potentially be useful as it can show the ductus (on 2D echocardiography) as a communication between these two structures. However, since this is an isolated case report it will need prospective validation.…”

“…[1] In transthoracic echocardiography (TTE), the ductus is visualized using "high" parasternal (or the "ductal" view) or suprasternal windows. [2] It is generally agreed that imaging ductus during transesophageal echocardiography (TEE) can be suboptimal. [3] During TEE, visualization of the ductus arteriosus (DA) is obscured by the acoustic impedance offered by the left main bronchus.…”