7 year-old female referred to cardiology clinic for evaluation a murmur noted on routine physical examination.

Figures 1 and 2: The aortic arch is high and tortuous. There is a change in aortic caliber at the takeoff of the left subclavian artery, with the distal arch greater in size than the proximal aorta. There are no collaterals (normal internal mammary artery and intercostals arteries), to suggest hemodynamically significant stenosis.

Pseudocoarctation.

Pseudocoarctation (aortic kink) of the thoracic aorta is a distinct anatomic entity resulting from elongation of the aorta due to an unknown etiology. Because the descending aorta is fixed by both the intercostals arteries and the ductus arteriosus, the aortic arch rises higher into the mediastinum and buckles at the level of the insertion of the ductus arteriosus (similar to the localized form of true coarctation). The angiographic appearance resembles that of aortic coarctation, so the term pseudocoarctation is used, although “kinking or buckling” are more descriptive terms. Patients are usually asymptomatic because there is a lack of hemodynamically significant stenosis with < 10 mmHg pressure gradient across the kink. Patients have equal pulses bilaterally in the upper and lower extremities. A small number of patients can present with clinical symptoms, including chest pain, dyspnea, syncope, CHF, and hypertension. Although no pressure gradient exists, flow through the kinked area is turbulent, and an aneurysm of the proximal descending aorta may develop and require resection.

Pseudocoarctation of the aorta can be confused with true coarctation without a pressure gradient and with cervical aortic arch. It can be clinically differentiated from true coarctation by the absence of systemic hypertension, collateral circulation, delayed femoral pulses, or a significant hemodynamic gradient across the kinked segment. Pseudocoarctation has a similar incidence of associated bicuspid valve as true coarctation.

The imaging findings of pseudocoarctation can be identical to those of true coarctation and may be similar to a cervical aortic arch. The plain film findings are similar to true coarctation, with the exception that no rib notching or other evidence of collateral vessel formation is present. Pseudocoarctation can present as a homogeneous left upper mediastinal mass due to the redundancy of the elongated thoracic aorta. The angiographic findings are characteristic for pseudocoarctation and show an elongated aorta that buckles at the insertion of the ductus ligament. The descending aorta below the ductus is dilated because of turbulent flow.

Pseudocoarctation can be differentiated from a cervical aortic arch, because the latter shows an increased number of arteries to the head, a retroesophageal segment, and a descending aorta located on the side opposite the aortic arch. Pseudocoarctation also must not be confused with coarctation of the aorta without a pressure gradient, which shows a “butter-knife” deformity, no buckling, and no pressure gradient. MRI is the diagnostic study of choice. Images can adequately show the site and length of narrowing in pseudocoarctation, allow for evaluation of collateral, and allow for pressure measurements (phase contrast). MRI can also help define cardiac structure, for example, to look at a bicuspid valve.

References:

1. Amplatz K and JH Moller. Radiology of Congenital Heart Disease. Baltimore: Williams & Wilkins, 1993.
2. Brandt WE and CA Helms. Fundamentals of Diagnostic Radiology. Baltimore: Williams & Wilkins, 1999.