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Sketch showing heart with coarctation of the aorta. A: Coarctation (narrowing) of the aorta. 1:Inferior vena cava, 2:Right pulmonary veins, 3: Right pulmonary artery, 4:Superior vena cava, 5:Left pulmonary artery, 6:Left pulmonary veins, 7:Right ventricle, 8:Left ventricle, 9:Pulmonary artery, 10:Aorta
Schematic drawing of alternative locations of a coarctation of the aorta, relative to the ductus arteriosus. A: Ductal coarctation, B: Preductal coarctation, C: Postductal coarctation. 1: Aorta ascendens, 2: Arteria pulmonalis, 3: Ductus arteriosus, 4: Aorta descendens, 5: Truncus brachiocephalicus, 6: Arteria carotis communis sinistra, 7: Arteria subclavia sinistra
Coarctation of the aorta, or aortic coarctation, is a congenital condition whereby the aorta narrows in the area where the ductus arteriosus (ligamentum arteriosum after regression) inserts.
There are three types:
- Preductal coarctation: The narrowing is proximal to the ductus arteriosus. If severe, blood flow to the aorta distal to the narrowing (supplying lower body) 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. This is the type seen in approximately 5% of infants with Turner Syndrome.
- 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. 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 and a weak femoral artery pulse 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 'figure 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 '3' image for which the sign is named. When the esophagus is filled with barium, a reverse 3 or E sign is often seen and represents a mirror image of the areas of prestenotic and poststenotic dilatation.
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, e.g. internal thoracic arteries via. the subclavian arteries. Those can be seen on MR, CT or angiography. An untreated coarctation may also result in hypertrophy of the left ventricle.
A case of coarctation of the aorta was published in the New England Journal of Medicine in 2007 employing chest radiography and magnetic resonance images.
A case of long-standing misdiagnosed coarctation of the aorta in an adult was described in the New York Times Magazine.
Therapy is conservative if asymptomatic, but may require surgical resection of the narrow segment if there is arterial hypertension. The first operations to treat coarctation were carried out by Clarence Crafoord in Sweden in 1944. 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).
For fetuses at high risk for developing coarctation, a novel experimental treatment approach has been developed and is being investigated at the German Center for Fetal Surgery & Minimally Invasive Therapy, Bonn University, Germany (Materno-fetal hyperoxygenation) (www.uniklinik-bonn.de/dzft). The treatment requires the mother to inhale 45% of oxygen via a face mask three times a day (3 x 3–4 hours) and is initiated beyond 34 weeks of gestation. The oxygen is transferred via the placenta to the fetus and results in dilatation of the fetal lung vessels. As a consequence, more blood flows through the fetal lungs and returns to the left side of the heart. From there it is pumped into the aorta and reaches its underdeveloped arch. In suitable fetuses, marked increases in aortic arch dimensions have been observed over treatment periods of about two to three weeks (Ref. Kohl T, Tchatcheva K, Stressig R, Geipel A, Heitzer S, Gembruch U. Maternal hyperoxygenation in late gestation promotes rapid increase of cardiac dimensions in fetuses with hypoplastic left hearts with intrinsically normal or slightly abnormal aortic and mitral valves. Ultraschall in Med 2008;29: 92).
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