Coarctication of the Aorta
- Coarctication of the aorta refers to a lesion whereby blood flow through the descending aorta is obstructed. The location of obstruction is variable; although is most commonly found at the insertion of the ductus arteriosus (Keane).
- Historically, coarctication has been classified as being either pre- or post-ductal; however, this nomenclature is anatomically incorrect and is of little value in planning corrective surgery. A classification system based on the degree of aortic hypoplasia and associated lesions was developed to address this (St. Louis).
- Type I defects involves narrowing in a segment of aorta adjacent to the ductus arteriosus insertion point.
- Type II defects refer to narrowing in the same area as in type I in combination with hypoplasia of the aorta in the area between the ductus arteriosus and left subclavian artery.
- Type III defects are the most extreme form and involve a severe hypoplasia of a large portion of the aortic arch, typically between the left carotid artery and left subclavian artery.
- Coarctication of the aorta is also commonly associated with other congenital defects such as ventricular septal defects, mitral valve abnormalities, complex heart disease, and an interrupted aortic arch.
- In the normal situation, the aortic arch narrows just superior to the insertion of the ductus arteriosus. In the fetus, blood supply below this narrowing is supplied by the right ventricle via the patent ductus arteriosus while the blood above is supplied by the left ventricle via the ascending aorta.
- Coarctication results in differential blood flow to regions of the body, specifically upper and lower body. It typically becomes more obstructive as the child grows but due to concurrent development of extensive collateral blood flow to circumvent the obstruction, differences between blood pressure in the arms and legs may not be apparent.
- In addition to variations in blood pressure between the upper and lower body, coarctication also causes hypertension and hypertrophy in the left ventricle.
- Management of this lesion depends on location of coarctication and presence of associated cardiac anomalies. Early surgery is recommended for patients with uncomplicated coarctication and variation in systolic pressure between arms and legs of 20 mmHg.