Coarctation of the Aorta

Valerie L Ward, MD
Robert D Pugatch, MD

March 19, 1997

Presentation

Imaging Findings

Posteroanterior (PA) and lateral chest radiographs demonstrate mild dilatation of the ascending aorta with filling of the anterior clear space (long black arrows), localized narrowing of the distal aortic arch (long white arrow), and mild dilatation of the descending aorta. These prestenotic and poststenotic dilatations result in a "figure 3" appearance of the aorta. The left ventricle is hypertrophied and the pulmonary blood flow is normal. The inferior aspects of posterior ribs 3 to 12 bilaterally are notched (white arrows).

Differential Diagnosis

The "figure 3" sign can also be seen in pseudocoarctation. However, a pressure gradient is not associated with the stenosis of pseudocoarctation (rib notching does not occur). Thus, pseudocoarctation is a less likely diagnosis in this patient.

Diagnosis

Discussion

The most specific chest radiograph findings in aortic coarctation are inferior rib notching and the aortic "figure 3" sign. Rib notching is due to pressure erosion by the enlarged and tortuous intercostal arteries in the costal sulcus of the ribs. The intercostal arteries provide collateral blood flow to circumvent the stenotic aortic segment. However, the first two intercostal arteries are supplied by the costocervical trunk rather than the descending aorta below the level of coartation. Therefore, the first two intercostal arteries are not collateral pathways and so ribs one and two do not show notching. Rib notching implies long-standing obstruction and is not seen before age 10.

The aortic contour abnormalities that result in the "figure 3" sign are formed by prestenotic dilatation of the ascending aorta, indentation of the coarctation site, and poststenotic dilatation of the descending aorta. The chest radiograph is the mainstay for this diagnosis.

Of the two types of coarctation, the most common is localized (adult or postductal) with a short segment of narrowing near the ligamentum arteriosum. These patients are asymptomatic until later in childhood, and at that time they present with hypertension, differential arm/leg blood pressures and/or a heart murmur. The diffuse type (infantile or preductal) has a long segment of hypoplastic narrowing just distal to the brachiocephalic artery orifice. These patients present in early infancy and childhood with congestive heart failure. These patients have a worse prognosis than those who present with the more common type.

Coarctation of the aorta is associated with other congenital anomalies such as bicuspid aortic valve (70%), patent ductus arteriosus, ventricular septal defect, tricuspid atresia, and transposition of the great vessels. Noncardiac associations include berry aneurysms in the circle of Willis and Turner's syndrome. Diagnosing coarctation early is important to prevent associated complications including aortic aneurysm, dissection, and bacterial endocarditis at the coarctation site or bicuspid aortic valve.

References

2. Brandt WE, Helms CA. Fundamentals of diagnostic radiology. Baltimore: Williams & Wilkins, 1994.

3. Amplatz K, Moller JH , Casteneda-Zuniga WR. Radiology of congenital heart disease. New York: Thieme, 1986:466

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