Wednesday 10 November 2004
Definition: Coarctation of the aorta is a narrowing of the aorta.
- preductal (infantile-type)
- postductal (adult-type)
discrete or long narrowing
thickened ridges protruding posteriorly and laterally into the aortic lumen
- The ductus artriosus or ligamentum arteriosus (closed and fibrosed) inserts at the same level anteromedially.
distal to the coarctation
- intimal proliferation
- disruption of elastic tissue
aortic cystic medial necrosis
The vascular malformation responsible for coarctation is a defect in the vessel media, giving rise to a prominent posterior infolding (the "posterior shelf"), which may extend around the entire circumference of the aorta.
Coarctation is due to an abnormality in development of the embryologic left fourth and sixth aortic arches that can be explained by 2 theories, the ductus tissue theory and the hemodynamic theory.
In the ductus tissue theory, coarctation develops as the result of migration of ductus smooth muscle cells into the periductal aorta, with subsequent constriction and narrowing of the aortic lumen. Commonly, coarctation becomes clinically evident with closure of the ductus arteriosus. This theory does not explain all cases of coarctation. Clinically, coarctation may occur in the presence of a widely patent ductus arteriosus, and it may occur quite distant from the insertion of the ductus arteriosus, such as in the transverse arch or abdominal aorta.
In the hemodynamic theory, coarctation results from reduced volume of blood flow through the fetal aortic arch and isthmus. In a normal fetus, the aortic isthmus receives a relatively low volume of blood flow. Most of the flow to the descending aorta is derived from the right ventricle through the ductus arteriosus. The left ventricle supplies blood to the ascending aorta and brachiocephalic arteries, and a small portion goes to the aortic isthmus. The aortic isthmus diameter is 70-80% of the diameter of the neonatal ascending aorta.
Based on this theory, lesions that diminish the volume of left ventricular outflow in the fetus also decrease flow across the aortic isthmus and promote development of coarctation. This helps to explain the common lesions associated with coarctation, such as ventricular septal defect, bicuspid aortic valve, left ventricular outflow obstruction, and tubular hypoplasia of the transverse aortic arch. This theory does not explain isolated coarctation without associated intracardiac lesions.
In the US: This condition represents 5-10% of all congenital cardiac lesions. It represents 7% of critically ill infants with heart disease.
- aortic malformations
- aortic lesions
- aortic diseases