Coarctation of the aorta accounts for approximately 5% of all congenital heart diseases. Coarctation is a discrete infolding of the posteriolateral wall of the aorta, which results in an obstructing membrane at the level of the ductus arteriosus. There are several classifications of the coarctation based on the age of the patient, the length of the coarctation and the site of the ductus arteriosus in relation to the coarctation. Coarctation is most commonly classified into adult (postductal) type and infantile (preductal) type. However, many patients with preductal lesions do not present until adulthood. The age of the patient at presentation is dependent on the severity rather than the site of obstruction. Usually those with severe obstruction or associated cardiac anomalies present early, as a result of cardiac failure or occasionally cerebrovascular accident, aortic dissection, or endocarditis. Most other patients are identified accidentally during routine medical examination. 25-50% of patients will also have a bicuspid aortic valve. Patent ductus arteriosus, ventricular septal defects and Turner syndrome are other common associations with aortic coarctation.
Imaging plays an important role in confirming the diagnosis suggested by physical examination. The patency of the ductus arteriosus, collateral pathways, other arch anomalies, subclavian artery anomalies and associated lesions all must be assessed. In infancy, the evaluation is made by echocardiography. In children and adults MRI, CT and occasionally angiography provide additional important information.
On frontal chest radiographs, the indentation at the site of the coarctation results in the figure of 3 sign. The distal convexity in this region represents the poststenotic dilatation. The ascending aorta may be dilated, normal or invisible. The left subclavian artery is frequently dilated in response to the hypertension and visible as it swings towards the apex of the left lung. Rib notching along the inferior aspect of the third to the eighth ribs can usually be seen in untreated patients by 8 to 10 years of age. The intercostal arteries that serve as collateral channels originate from the descending aorta. For this reason the first and second ribs do not have notches. Unilateral rib notching means presence of an anomalous subclavian artery.
Echocardiography is useful in evaluating the aortic valve and measuring the pressure gradients across the coarctation. MRI is now considered the imaging modality of choice in older children and adults for evaluation of the thoracic aorta. Spiral CT with three-dimensional reconstruction is a reliable non-invasive technique and provides impressive images of the aortic arch, but may be inferior to MRI. Aortography gives the highest resolution of the coarctation, the aortic arch vessels and the collateral channels.
Treatment of coarctation is surgical. There are several techniques available such as resection with end-to-end anastomosis, subclavian flap aortoplasty, percutaneous balloon angioplasty and expandable endovascular stents. Despite accurate anatomical reconstruction, local aortic complications including recoarctation, aneurysm formation and rupture may occur during long-term follow-up. These complications can be diagnosed by using echocardiography, CT and MRI.