coarctation of aorta

Coarctation of the aorta (CoA) refers to a narrowing of the aortic lumen.

Epidemiology

Coarctations account for between 5-8% of all congenital heart defects. They are more frequent in males, M:F ratio of ~2-3:1.

Clinical presentation

Varies accordingly to the degree of stenosis and the associated abnormalities. Patients may be asymptomatic in a setting of non-severe stenosis.

Children and adults can present with angina pectoris and leg claudication. On clinical examination, diminished femoral pulses and differential blood pressure between upper and lower extremities may be noted.

ECG
  • high left ventricular voltage (HLVV) 
  • left ventricular "strain" pattern
    • variably present in the lateral leads (I, aVL, V5-6)
    • asymmetric T-wave inversion originating from a depressed ST segment
  • right ventricular hypertrophy
    • less common

Pathology

It can be primarily divided into two types:

  • infantile (pre-ductal) form
  • adult (juxta-ductal, post-ductal or middle aortic) form
    • characterized by a short segment abrupt stenosis of the post-ductal aorta
    • it is due to thickening of the aortic media and typically occurs just distal to the ligamentum arteriosum (a remnant of the ductus arteriosus)
  • Associations

    As with many congenital abnormalities, coarctation of the aorta is associated with other congenital anomalies.

    Radiographic features

    Plain radiograph
    • figure of 3 sign: contour abnormality of the aorta
    • inferior rib notching: Roesler sign
      • secondary to dilated intercostal collateral vessels which form as a way to bypass the coarctation and supply the descending aorta
      • the dilated and tortuous vessels erode the inferior margins of the ribs, resulting in notching
      • seen only in long standing cases, and therefore not seen in infancy (unusual in patients <5 years of age) 
      • seen in 70% of cases presenting in older children or adults
      • if the coarctation is distal to either subclavian artery, then increased flow occurs through the subclavian artery, forming a collateral pathway via the internal thoracic artery, anterior intercostal artery, posterior intercostal artery and then into the descending thoracic aorta
      • usually the 4 to 8 ribs are involved; occasionally involves the 3rd to 9th ribs
      • as the 1st and 2nd posterior intercostal arteries arise from the costocervical trunk (a branch of the subclavian artery) and do not communicate with the aorta, these are not involved in collateral formation, and the 1st and 2nd ribs do not become notched
      • if bilateral rib notching: the coarctation must be distal to the origin of both subclavian arteries, to enable bilateral collaterals to form
      • if unilateral right rib notching
        • then the coarctation lies distal to the brachiocephalic trunk but proximal to the origin of the left subclavian artery
        • or there may be a right sided aortic arch with aberrant left subclavian artery distal to coarctation
          • collaterals cannot form on the left, as the left subclavian is distal to the coarctation
      • if unilateral left rib notching, then this suggests an associated aberrant right subclavian artery arising after the coarctation
        • the coarctation is distal to the origin of the left subclavian artery, therefore collaterals form on the left
        • collaterals cannot form on the right, as the aberrant right subclavian artery arises after the coarctation
    Antenatal ultrasound

    Useful in assessing for infantile coarctations. The suprasternal notch-long axis views are considered helpful. The fetal right ventricle can be appear enlarged in severe coarctations although this alone is not a specific feature. Occasionally an aortic arch view may directly show a narrowing.

    Echocardiography

    Best visualized from the suprasternal window with transthoracic echocardiography and the upper esophageal positions with a transesophageal approach. Features commonly present include :

    • reduction in luminal caliber of the descending aorta
      • often accompanied by post-stenotic dilatation
    • demonstrates sudden increase in velocity as measured by pulsed wave Doppler
      • the continuous wave Doppler envelope will demonstrate the characteristic "shark tooth" morphology
        • sharply elevated systolic peak
        • diastolic velocity profile markedly concave
    • left ventricular hypertrophy
    Angiography: CTA/MRA/DSA

    All modalities are capable of delineating the coarctation as well as collateral vessels, most common collateral pathway being subclavian artery to internal mammary artery to intercostal arteries (resulting in inferior rib notching) to post-coarctation part of descending thoracic aorta.

    Treatment and prognosis

    The urgency of treatment depends on the presence of congestive cardiac failure. This is usually the case in severe coarctations found in infancy. In less severe cases, elective treatment when the child is older (typically ~2 years of age) is preferred .

    Treatment can be either primary surgical repair with excision of the coarctation and end-to-end anastomosis, or balloon angioplasty. Subclavian flap repair is a common surgical technique used, where the origin and proximal left subclavian artery is excised, opened up and sutured onto the aorta. If the subclavian is ligated, it is usually anastomosed onto the left common carotid artery.

    Complications

    Differential diagnosis

    Imaging differential considerations include: