Preductal coarctation: The narrowing is proximal to the ductus arteriosus. If severe, blood flow to the aorta distal (to lower body) to the narrowing is dependent on a patent ductus arteriosus, and hence its closure can be life-threatening. Preductal coarctation results when an intracardiac anomaly during fetal life decreases blood flow through the left side of the heart, leading to hypoplastic development of the aorta.
Ductal coarctation: The narrowing occurs at the insertion of the ductus arteriosus. This kind usually appears when the ductus arteriosus closes.
Postductal coarctation: The narrowing is distal to the insertion of the ductus arteriosus. Even with an open ductus arteriosus blood flow to the lower body can be impaired. Newborns with this type of coarctation may be critically sick from the birth. This type is most common in adults. It is associated with notching of the ribs, hypertension in the upper extremities, and weak pulses in the lower extremities. Postductal coarctation is most likely the result of muscular ductal (ductus arteriosis) extends into the aorta during fetal life.
Signs and symptoms
Arterial hypertension in the right arm with normal to low blood pressure in the lower extremities is classic. Poor peripheral pulses in the femoral arteries may be found in severe cases.
If the coarctation is situated before the left subclavian artery, asynchronous radial pulses will be detected in the right and left arms. A radial-femoral delay between the right arm and the femoral artery would be apparent, whilst no such delay would occur under left arm radial-femoral palpation.
A coarctation occurring after the left subclavian artery will produce synchronous radial pulses, but radial-femoral delay will be present under palpation in either arm.
Imaging and diagnosis
With imaging, resorption of the lower part of the ribs may be seen, due to increased blood flow over the neurovascular bundle that runs there. Post-stenotic dilation of the aorta results in a classic 'reverse 3 sign' on x-ray. The characteristic bulging of the sign is caused by dilatation of the aorta due to an indrawing of the aortic wall at the site of cervical rib obstruction, with consequent post-stenotic dilation. This physiology results in the reversed '3' image for which the sign is named.
Coarctation of the aorta can be accurately diagnosed with magnetic resonance angiography. In teenagers and adults echocardiograms may not be conclusive. In adults with untreated coarctation blood often reaches the lower body through collaterals, eg. internal thoracic arteries via. the subclavian arteries. Those can be seen on MR or angiography. An untreated coarctation may also result in hypertrophy of the left ventricle.
Therapy is conservative if asymptomatic, but may require surgical resection of the narrow segment if there is arterial hypertension. In some cases angioplasty can be performed to dilate the narrowed artery. If the coarctation is left untreated, arterial hypertension may become permanent due to irreversible changes in some organs (such as the kidney).