In coarctation of the aorta, which occurs in 3.2/10,000 births, the aortic lumen below the origin of the left subclavian is significantly narrowed. Since the constriction may be above or below the entrance of the ductus arteriosus, two types of coarctations may be distinguished: preductal and posductal.
The cause of aortic narrowing is primarily abnormality in the media of the aorta, followed by intima proliferations.
In the preductal type the ductus arteriosus persists, whereas in the postductal type, which is more common, this channel is usually obliterated. In the latter case, collateral circulation between the proximal and distal parts of the aorta is established by way of large intercostal and internal thoracic arteries. In this manner, the lower part of the body is supplied with blood.
Complications of coarctation include the backflow of blood to the left ventricle, which can cause ventricular hypertrophy. Because of this ventricular hypertrophy, the body would increase its demand for blood.
Complications of postductal coarctation include increased pressure in the upper extremities, a loss of femoral pulse, and cerebral hemorrhage.
In patients who have coarctation of the aorta, the intercostal arteries enlarge greatly and produce nothing of the lower ribs. The notching occurs because the intercostal artery is retracted from the rib, demonstrating erosion of the costal groove by the tortuous vessel.
- Coarctation of the aorta is a congenital narrowing of the aorta just proximal to, opposite, or distal to the site of attachment of the ligamentum arteriosum.
- In coarctation of the aorta, the blood supply for the head, neck, and upper limbs are not affected (in fact, blood pressure in these regions increases)
- In this condition, there is absent or diminished femoral pulses
- As compensation, an enormous collateral circulation develops with dilation of the anterior internal carotid artery (from the internal thoracic and then subclavian) and posterior internal carotid artery (descending aorta)
- this condition is treated surgically.
- Most of constrictions in the aorta occur distal to the origin of left subclavian artery opposite the attachment of ligamentum arteriosum (juxta ductal).
- Postductal coarctation: distal to ductus arteriosus - permits collaterals to form.
- Preductal coarctation: proximal to ductus arteriosus. Flow to lower parts through ductus arteriosus.
- Constriction of the systemic arch.
- In the fetus the left ventricle blood in the aortic arch goes to the heart, head, neck, and arms; whilst the descending aorta gets its own supply through the ductus arteriosus. The blood flow between the subclavian artery and the ductus is minimal.
- After birth this section may narrow causing coarctation.
- The seriousness depends on the degree of constriction.
- The blood pressure in the arms tends to be significantly greater than the blood pressure in the legs.
- There is diminished and delayed femoral pulse.
- Patients exhibit a harsh systolic ejection murmur between the shoulder blades.
- There may be rib notching (due to collateral circulation through the intercostal arteries).
- There may also be dilatation of the aorta
- In 95% of cases, the coarctation (narrowing) is distal to the left subclavian artery. The infantile type is proximal to the ligamentum arteriosum; the adult type is distal.
- Treatment is surgial repair or balloon angioplasty.
- Coarctation of the aorta is twice as common in males as in females and is frequently associated with ventricular septal defect, patent ductus arteriosus, and bicuspid aortic valve. The most common surgically correctable and cause of secondary hypertension include Conn's Syndrome (aldosterone-producing adrenocortical adenoma), renal artery stenosis, coarctation of the aorta, and pheochromocytoma. Turner's Syndrome (45, XO) is associated with an increased incidence of coarctation of the aorta.
Reference:
1. Anatomy & Physiology Manual. Butler L, Bouncir G, Burnett G. Lancashire & South Cumbria Cardiac Network. 2004.
2. Blackwell's Underground Clinical Vignettes: Anatomy, 3rd Ed. Bhushan, Vikas, M.D., et al. Blackwell Science Publishing. 2002.
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