Coarctation of the Aorta

Coarctation of the aorta is best displayed from the suprasternal or high parasternal window. 2D imaging differentiates between discrete stenosis and tubular hypoplasia of the aortic arch. Colour Doppler helps to differentiate normal flow from accelerated turbulent flow in the region of the stenosis. Patency of the ductus arteriosus can be displayed in the left parasternal view. In the neonatal period, as long as the ductus arteriosus is widely patent, absence of accelerated flow in the aortic arch or isthmus during colour Doppler interrogation is completely insufficient to exclude severe coarctation. In the presence of a closed ductus arteriosus, PW and CW Doppler show accelerated flow across the stenosis. Severe coarctation is characterized by accelerated flow velocities both in systole and diastole resulting in a sawtooth flow pattern, while exclusive acceleration of systolic flow is found in mild to moderate stenosis. With the Bernoulli equation, the systolic pressure gradient across the stenosis can be estimated. In the presence of accelerated flow proximal to the stenosis, the expanded Bernoulli equation has to be applied. In neonates and infants, additional flow measurements of the aortic arch and isthmus flow measurements in pre- and poststenotic reference arteries are helpful for confirmation of the diagnosis: prestenotic reference arteries are the cerebral arteries; poststenotic reference arteries are the abdominal arteries. In severe coarctation with closed ductus arteriosus, significantly reduced flow velocities are found in the abdominal arteries, while in contrast to healthy infants, peak systolic flow velocities in the cerebral arteries are significantly higher than peak systolic flow velocities in the coeliac artery.