Coarctation of the Aorta
(See also Overview of Congenital Cardiovascular Anomalies.)
Coarctation of the aorta is a localized narrowing of the aortic lumen that results in upper-extremity hypertension, left ventricular hypertrophy, and malperfusion of the abdominal organs and lower extremities. Symptoms vary with the anomaly’s severity and range from headache, chest pain, cold extremities, fatigue, and leg claudication to fulminant heart failure and shock. A soft bruit may be heard over the coarctation site. Diagnosis is by echocardiography or by CT or MR angiography. Treatment is balloon angioplasty with stent placement, or surgical correction.
Coarctation of the aorta accounts for 6 to 8% of congenital heart anomalies. It occurs in 10 to 20% of patients with Turner syndrome. The male:female ratio is 2:1.
Coarctation of the aorta usually occurs at the proximal thoracic aorta just beyond the left subclavian artery and before the opening of the ductus arteriosus. Coarctation rarely involves the abdominal aorta. Thus, in utero and before the patent ductus arteriosus (PDA) closes, much of the cardiac output bypasses the coarctation via the PDA. Coarctation may occur alone or with various other congenital anomalies (eg, bicuspid aortic valve, ventricular septal defect, aortic stenosis, patent ductus arteriosus, mitral valve disorders, intracerebral aneurysms).
Physiologic consequences involve 2 phenomena:
Pressure overload causes left ventricular hypertrophy and hypertension in the upper part of the body including the brain.
Hypoperfusion affects the abdominal organs and lower extremities. Malperfusion of the intestine increases the risk of sepsis due to enteric organisms.
Ultimately, the pressure gradient increases collateral circulation to the abdomen and lower extremities via intercostal, internal mammary, scapular, and other arteries.
Untreated coarctation may result in left ventricular hypertrophy, heart failure, collateral vessel formation, bacterial endocarditis, intracranial hemorrhage, hypertensive encephalopathy, and hypertensive cardiovascular disease during adulthood. Patients with untreated coarctation are at increased risk of aortic dissection or rupture later in life or in association with pregnancy. The ascending aorta is the area most frequently involved in dissection or rupture. Current data suggest that this risk is less likely a direct consequence of the coarctation and more likely related to a bicuspid aortic valve and associated aortopathy.
If coarctation is significant, circulatory shock with renal insufficiency (oliguria or anuria) and metabolic acidosis may develop in the first 7 to 10 days of life and may mimic findings of other systemic disorders such as sepsis. Infants with critical (severe) coarctation are likely to become acutely ill as soon as the ductus arteriosus constricts or closes.
Less severe coarctation may be asymptomatic during infancy. Subtle symptoms (eg, headache; chest pain, fatigue, and leg claudication during physical activities) may be present as children age. Upper-extremity hypertension is often present, but heart failure (HF) rarely develops after the neonatal period. Rarely, intracerebral aneurysms rupture, resulting in subarachnoid or intracerebral hemorrhage.
Typical physical examination findings include strong pulses and hypertension in the upper extremities, diminished or delayed femoral pulses, and a BP gradient, with low or unobtainable arterial BP in the lower extremities.
A grade 2 to 3/6 ejection systolic murmur is often present at the upper left sternal border, left axilla, and sometimes most prominently in the left interscapular area (see Table: Heart Murmur Intensity). An apical systolic ejection click is present if a bicuspid aortic valve is also present. Dilated intercostal collateral arteries may cause a continuous murmur in the intercostal spaces.
Affected females may have Turner syndrome, a congenital disorder causing lymphedema of the feet, webbed neck, squarely shaped chest, cubitus valgus, and widely spaced nipples.
Diagnosis is suggested by clinical examination (including BP measurement in all 4 extremities), supported by chest x-ray and ECG, and established by 2-dimensional echocardiography with color flow and Doppler studies or, in older patients with a suboptimal echocardiographic window, with CT or MR angiography.
Chest x-ray shows coarctation as a “3” sign in the upper left mediastinal shadow. Heart size is normal unless heart failure supervenes. Dilated intercostal collateral arteries may erode the 3rd to 8th ribs, causing rib notching, but this is seldom seen before age 5 yr.
ECG usually shows left ventricular hypertrophy but may be normal. In neonates and small infants, ECG usually shows right ventricular hypertrophy rather than left ventricular hypertrophy.
Symptomatic neonates are treated promptly. In infants who do not have symptoms, the condition is monitored until definitive repair is done.
Symptomatic neonates require cardiopulmonary stabilization with infusion of prostaglandin E1 (0.01 to 0.10 mcg/kg/min—titrate to the lowest effective dose) to reopen the constricted ductus arteriosus. Opening the ductus and its aortic ampulla provides some relief by allowing pulmonary artery blood to bypass the aortic obstruction via the ductus and increase perfusion of the descending aorta, improving systemic perfusion and reversing metabolic acidosis.
Diuretics can help treat heart failure symptoms. IV cardioactive drugs (eg, milrinone, dopamine, dobutamine) can be useful in select circumstances (eg, infants with HF and significant left ventricle dysfunction).
In nonemergent situations, patients with hypertension may be treated with beta-blockers; ACE inhibitors may adversely affect renal function. After repair of the coarctation, hypertension may persist or develop years after repair and can be treated with beta-blockers, ACE inhibitors, angiotensin II receptor blockers, or calcium channel blockers.
Supplemental oxygen should be used with caution in neonates because the resulting decrease in pulmonary vascular resistance may increase pulmonary blood flow at the expense of systemic blood flow.
The preferred definitive treatment is controversial. Some centers prefer balloon angioplasty with or without stent placement, but most prefer surgical correction and reserve the balloon procedure for recoarctation after surgical correction or for primary treatment of discrete coarctation in older children or adolescents. Initial success rate after balloon angioplasty is about 73% in patients with native coarctation and about 80% in patients with recurrent coarctation. Subsequent catheterization can dilate the stent as children grow.
Surgical options include resection and end-to-end anastomosis, patch aortoplasty, and left subclavian flap aortoplasty. In severe coarctation manifesting early in life, the transverse aorta and isthmus are often hypoplastic, and this region of the aorta may need to be surgically enlarged.
Choice of surgical technique depends on anatomy and center preference. Surgical mortality rate is < 5% for symptomatic infants and <1% for older children. Residual coarctation is common (6 to 33%). Rarely, paraplegia results from cross-clamping of the aorta during surgery.
Endocarditis prophylaxis is not needed preoperatively and is required only for the first 6 mo after repair.
Coarctation of the aorta is a localized narrowing of the lumen, typically in the proximal thoracic aorta just beyond the left subclavian artery and before the opening of the ductus arteriosus.
Manifestations depend on severity of coarctation but typically involve pressure overload proximal to the coarctation, leading to heart failure, and hypoperfusion distal to the coarctation.
Severe coarctation can manifest in the neonatal period with acidosis, renal insufficiency, and shock, but mild coarctation may not be apparent until an adolescent or adult is evaluated for hypertension.
There is typically a BP gradient between upper and lower extremities and a grade 2 to 3/6 ejection systolic murmur, sometimes most prominent in the left interscapular area.
For symptomatic neonates, infuse prostaglandin E1 to reopen the constricted ductus arteriosus.
Correct coarctation surgically or using balloon angioplasty with or without stent placement.