Chapter30 Aorta

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Section V: Cardiac Radiology

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Figure 30.20.  Aortic Coarctation. Sagittal CT ( A ), sagittal CT MIP ( B ), and coronal MIP ( C ). Focal narrowing of the proximal descending thoracic aorta corresponds to a postductal aortic coarctation ( white arrow ). Large collateral intercostal ( B , dashed black arrows ) and internal mammary arteries ( C , *) are present.

blood flow occurs via adjacent internal mammary and inter- costal arteries which become enlarged (Fig. 30.20). Although classically there is differential blood pressure and asymmetric pulses between the right and left upper extremities (in the con- text of preductal coarctation) or between the upper and lower extremities (postductal coarctation), blood pressure between upper and lower extremities can potentially equalize in the setting of very extensive collateral formation. Radiographic findings of aortic coarctation may only be apparent in severe cases. Indentation of the distal aortic arch with pre- and poststenotic dilation results in a “figure-of-3” sign on chest radiograph. Hypertrophied intercostal arteries result in bilateral central rib notching, involving the posterior fourth through eighth ribs (Fig. 30.21). Although CT best

approximately 6% to 8% of all congenital heart disease. There is a strong association with bicuspid aortic valve, which occurs in up to 75% of coarctation cases, and Turner syn- drome. The etiology remains unclear but a common pathogen- esis with bicuspid aortic valve has been proposed, including abnormalities of neural crest tissue migration, decreased in utero blood flow, and aortopathy with cystic medial necrosis. There are two main types of aortic coarctation: preduc- tal and postductal. Preductal coarctation tends to be more severe, involving a longer segment. It commonly presents in infancy, with systemic hypoperfusion following closure of the ductus arteriosus. Postductal coarctation usually presents in adulthood with hypertension and signs of left heart failure. To bypass the area of aortic narrowing, collateral systemic

Figure 30.21.  Aortic Coarctation. Coned down frontal chest radiograph in a patient with aortic coarctation demonstrates the “ figure-of-3 ” sign with indentation of the 3 corresponding to the area of aortic narrowing. Inferior rib notching is also present due to hypertrophied intercostal collateral arteries ( arrows ).