Aortic Coarctation

Aortic coarctation is the most common congenital abnormality of the thoracic aorta, occurring with a frequency in newborns of 4/10000. It can be found in 7% of patients with congenital heart disease [ 12, 13]. Coarctation of the aorta develops secondarily to a deformity of the aortic media in which a fibrous ridge protrudes into the vascular lumen. The anomaly most frequently occurs distal to the left subclavian artery or near the branching of the ductus arteriosus (Fig. 5). Different forms of stenotic vascular segments can be found: the lesion may be focal, as in a juxtaductal coarctation; diffuse, as in a hypoplastic aortic isthmus; or complete, as in an aortic arch interruption. Depending on the grade of the stenosis, collateral circulation may develop via intercostal arteries, internal mammary arteries, lateral thoracic arteries, the anterior spinal artery, scapular arteries or transverse cervical arteries.

MR imaging has similar sensitivity to conventional angiography and higher sensitivity than echocardiography for the evaluation of stenotic segments and collateral vessels and for therapeutic monitoring (Fig. 6) [14]. Axial and left anterior oblique spin-echo sequences can determine the localisation and extension of the lesion. The vessel diameter can be measured on axial images perpendicular to the ascending and descending aorta. Expression of the severity of stenosis is possible as a percentage ratio between the minimal diameter of the isthmus and the mean diameter of the ascending and descending aorta subtracted from 100 [15]. A relevant stenotic segment can be presumed if a measured segment has a diameter of less than 50%.

CINE imaging with left anterior oblique orien-

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Fig. 5a-c. This case demonstrates a 2 week old male newborn with aortic coarctation. a After intravenous contrast agent application (Gd-BOPTA 0.1 mmol/kg bodyweight) the systemic arterial system from the supraaortic vessels down to the abdominal vessels are clearly depicted on the MIP reconstruction. Note the subtotal stenosis of the aortic isthmus distal to the branching of the left subclavian artery (arrow) depicting as complete interruption of contrast enhancement within the vessel. The subsequent increased blood pressure and blood flow leads to a kinking of the supraaortic vessels. b demonstrates the corresponding surface rendered image reconstruction in anterior-posterior and posterior-anterior (c) view

Fig. 5a-c. This case demonstrates a 2 week old male newborn with aortic coarctation. a After intravenous contrast agent application (Gd-BOPTA 0.1 mmol/kg bodyweight) the systemic arterial system from the supraaortic vessels down to the abdominal vessels are clearly depicted on the MIP reconstruction. Note the subtotal stenosis of the aortic isthmus distal to the branching of the left subclavian artery (arrow) depicting as complete interruption of contrast enhancement within the vessel. The subsequent increased blood pressure and blood flow leads to a kinking of the supraaortic vessels. b demonstrates the corresponding surface rendered image reconstruction in anterior-posterior and posterior-anterior (c) view

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Fig. 6a, b. MIP reconstruction of a 3D CE MRA dataset of the thoracic aorta (Gd-BOPTA, 0.1 mmol/kg) in a patient undergoing surgical intervention for aortic coarctation 6 years prior to the current imaging study. Although blood flow is significantly improved and the pressure gradient is relatively shallow, a late recurrence of reduced vessel diameter is depicted (arrow). b represents the corresponding surface reconstruction

Fig. 6a, b. MIP reconstruction of a 3D CE MRA dataset of the thoracic aorta (Gd-BOPTA, 0.1 mmol/kg) in a patient undergoing surgical intervention for aortic coarctation 6 years prior to the current imaging study. Although blood flow is significantly improved and the pressure gradient is relatively shallow, a late recurrence of reduced vessel diameter is depicted (arrow). b represents the corresponding surface reconstruction tation can demonstrate flow phenomena such as poststenotic jet phenomenon. Measurement of peak flow velocity is possible with the use of phase contrast images in through plane orientation and with this information the pressure gradient over the stenosis can be estimated on the basis of the Bernoulli equation.

Collateral vascularisation is best demonstrated on 3D CE MRA since the whole spectrum of possible collateral vascular pathways is demonstrable with one acquisition.

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