MR imaging of aortic coarctation.

Aortic coarctation accounts for 5%-10% of all congenital heart diseases and represents 7% of critically ill infants with heart disease. Magnetic resonance (MR) imaging allows the study of this disease with several advantages in comparison with conventional angiography, transesophageal echocardiography, and computed tomography. The MR protocol applied at our institution for both diagnosis and follow-up after surgical or endovascular treatment consists of four steps: morphologic study, cine MR study, flow analysis, and MR angiography (MRA). The first three sequences are acquired during breath-hold and with electrocardiographic gating. Anatomy is well depicted with dark-blood half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences. Cine true-fast imaging with steady-state precession (true-FISP) sequences show not only morphologic features but also blood-flow changes inside the aorta. Gradient-echo sequences for phase-velocity mapping allow flow analysis. Application of Bernoulli's equation - here briefly presented and discussed - allows for calculation of the pressure gradient caused by the coarctation. MRA, acquired with a breath-hold three-dimensional T1-weighted gradient-echo sequence and intravenous administration of paramagnetic contrast material, allows for optimal depiction of the aortic lumen, with a panoramic view of the whole aorta, its main branches and possible collateral circulation.