turbulent flow created by the obstruction can cause leaflet thickening and progressive aortic

insufficiency. Diffuse subaortic stenosis is a more severe form that creates a long, tunnel-like

obstruction. Diffuse subaortic stenosis should be distinguished from hypertrophic cardiomyopathy. Both

forms of subaortic stenosis are associated with a high risk of endocarditis. The clinical findings in

subvalvar AS are similar to those for valvar stenosis.

Intervention for discrete subvalvar stenosis is usually undertaken when the gradient exceeds 30 to 50

mm Hg or when aortic insufficiency is present. In these patients, resection of the membrane is readily

performed by a transaortic approach. To reduce the incidence of restenosis, we advocate concurrent

performance of a septal myomectomy to alter the geometry of the left ventricular outflow tract.98

Operative mortality approaches zero. The recurrence rate of discrete stenosis following membrane

resection and myomectomy has been reported to be as low as 4%.99 Complications associated with

membrane resection can include heart block, VSD, or damage to the aortic or mitral valve leaflets.

The indications for operative intervention in diffuse subaortic stenosis are similar to those for valvar

stenosis. When diffuse subaortic stenosis is associated with hypoplasia of the aortic annulus, repair is

best achieved with a Konno aortoventriculoplasty, whereby an incision is carried across the aortic

annulus and subjacent ventricular septum, the opening patched, and an aortic valve implanted. Patients

with an adequate aortic annulus may undergo a septoplasty (modified Konno), in which the septal

incision is confined to the immediate subvalvar area and a patch is used to widen the left ventricular

outflow tract without replacing the aortic valve. Despite the technical complexity of repair for diffuse

subaortic stenosis, excellent results have been reported with high survival and freedom from

reoperation.100

Supravalvar AS is characterized by thickening of the wall of the ascending aorta. The lesion may be

localized (80%) to the region of the sinotubular ridge (at the level of the valve commissures), creating

an hourglass deformity, or it may be more diffuse (20%), extending into the aortic arch and its

branches. In both varieties, the aortic valve leaflets may be abnormal. The free edges of the aortic valve

leaflets may adhere to the aortic wall in the region of intraluminal thickening, and this may lead to

reduced coronary blood flow during diastole. Aortic wall thickening may also extend into the coronary

ostia and further impair coronary blood flow. Associated cardiac lesions are common, particularly

branch PA stenoses. A genetic basis for supravalvar AS has been established.101 About 50% of cases of

supravalvar AS are associated with Williams syndrome, in which a partial deletion of chromosome 7

(including the elastin gene) leads to the triad of supravalvar stenosis, mental retardation, and a

characteristic “elfin” facies. Isolated mutations in the elastin gene have also been shown to produce

familial supravalvar AS with an autosomal dominant pattern of transmission. There is a significant

incidence of endocarditis in patients with supravalvar AS. Sudden death is frequently reported and is

probably related to coronary obstruction.

The signs and symptoms of supravalvar AS are similar to those in other forms of left ventricular

outflow tract obstruction. The diagnosis is made by echocardiography, but cardiac catheterization (and

more recently magnetic resonance imaging [MRI]) is essential to define the aortic, coronary, and

pulmonary arterial anatomy prior to surgical intervention.

Operative intervention is indicated for patients with supravalvar AS in whom the gradient exceeds 50

mm Hg. A number of operations have been proposed for the treatment of localized supravalvar stenosis.

The classic repair involves a longitudinal incision across the obstruction in the ascending aorta, which is

extended into the noncoronary sinus. The thickened, hypertrophic ridge is resected by endarterectomy

and the aortotomy is augmented with an elliptical patch. A variation of this repair involves creation of

an inverted-Y aortotomy with one limb of the Y extended into the noncoronary sinus and the other into

the right coronary sinus. A Y-shaped patch is then used to augment the aortotomy. Finally, the Brom

repair is performed by transection of the ascending aorta beyond the supravalvar ridge. Separate

incisions are then made through the supravalvar ridge into each sinus of Valsalva. Triangular patches

are placed to augment each of these incisions, thereby relieving the supravalvar obstruction.

Reconnection of the aortic root to the ascending aorta completes the repair. The repair of the diffuse

type of supravalvar stenosis is performed under circulatory arrest with extensive patching of the

ascending aorta, transverse arch, and involved arch arteries. Branch pulmonary stenoses are best

managed using transcatheter techniques.

The results of surgery for localized supravalvar AS are generally good with low operative mortality

and excellent long-term survival.102–104 The diffuse form is more difficult to treat, and recurrence is

more likely. Overall results are much worse when severe bilateral PA stenoses are present.

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COARCTATION OF THE AORTA

Coarctation of the aorta is a narrowing of the proximal descending thoracic aorta distal to the origin of

the left subclavian artery, near the insertion of the ductus arteriosus (or ligamentum arteriosum). The

severity of luminal narrowing and the length of the aorta affected are variable. Coarctation is thought

to occur as a result of ectopic tissue from the ductus arteriosus, which migrates into the wall of the

adjacent aorta. After birth, as the ductus closes, the ectopic tissue in the aorta also constricts.

Frequently, a posterior shelf of tissue is present at the point of most severe obstruction. The aortic

obstruction caused by coarctation creates a pressure load on the LV.

The incidence of coarctation is about 0.5 per 1,000 live births, and its prevalence is 5% of congenital

heart defects.7 Coarctation is commonly associated with other heart defects including bicuspid aortic

valve (in more than 50% of cases), PDA, and VSD. Other left-sided obstructive lesions may also be

present, such as aortic arch hypoplasia, AS, mitral stenosis, and left ventricular hypoplasia. Coarctation

is also recognized to occur in association with Turner syndrome.

Patients with severe coarctation present in the newborn period. Aortic obstruction is so significant

that perfusion of the lower body is dependent on flow from the ductus arteriosus. Spontaneous ductal

closure typically worsens the aortic obstruction and may lead to malperfusion of tissues distal to the

coarctation. The pressure load on the LV may precipitate CHF. Patients may develop shock with severe

acidosis, oliguria, and diminished distal pulses. Infants with severe coarctation will generally not

survive without intervention.

7 Older children with coarctation are usually asymptomatic. The diagnosis is commonly made on the

basis of hypertension in the upper extremities with decreased pulses in the lower extremities.

Noninvasive blood pressure measurements in all four extremities help to quantify the severity of aortic

obstruction. These older patients tend to develop extensive collateral arteries that bypass the

obstruction. Life expectancy for these patients is limited due to the development of heart failure later in

life. Other long-term complications of coarctation include chronic hypertension, endocarditis (frequently

involving a bicuspid aortic valve), endarteritis (in the poststenotic area of the aorta at the site of the jet

of turbulent flow), aortic dissection, aortic aneurysm, and intracranial hemorrhage (from Berry

aneurysms, which occur more commonly in patients with coarctation).105

The diagnosis of coarctation can usually be made clinically. The infant with significant coarctation is

frequently asymptomatic at birth, but following closure of the ductus develops signs of heart failure

such as irritability, tachypnea, and poor feeding. Lower extremity pulses are absent, and upper

extremity pulses may be weak. Chest radiography shows cardiomegaly and pulmonary venous

congestion. There is a left ventricular strain pattern on the ECG. Echocardiography is usually diagnostic,

demonstrating narrowing of the aorta at the coarctation site with a loss of pulsatility in the descending

aorta.

In older children and adults with coarctation, there is usually a pressure gradient between the arms

and legs, which can be demonstrated by measuring cuff pressures in all four extremities. On chest

radiography, rib notching may be evident, secondary to erosion of the inferior rib borders from the

development of large intercostal collateral vessels. Echocardiography usually confirms the diagnosis.

Anatomic details may also be clarified with computed tomography (CT) and MRI. Cardiac

catheterization is usually not necessary.

Generally, all patients with coarctation should undergo surgical repair. For neonates, the acute

medical management includes initiation of PGE1

for the purpose of reopening the ductus; this maneuver

partially relieves the aortic obstruction and augments perfusion of the lower body due to improved

antegrade flow across the arch, as well as right-to-left flow across the ductus. Prostaglandins are usually

effective for reopening the ductus when initiated within 7 to 10 days of life, but are less successful

thereafter.

Surgical repair of coarctation is usually performed through a left posterolateral thoracotomy via the

third or fourth intercostal space. Neonates with an associated hypoplastic aortic arch may require

sternotomy for extended arch augmentation with either primary extended end-to-end repair or patch

augmentation. For repair via thoracotomy, the descending thoracic aorta, ductus (or ligamentum),

transverse aortic arch, and brachiocephalic vessels are mobilized. Care is taken to preserve the vagus

nerve and its recurrent laryngeal branch. The preferred surgical approach to coarctation in infants and

children is a resection with end-to-end anastomosis or extended end-to-end repair if there is associated

mild distal arch hypoplasia.106 In older children and adults, it may not be possible to perform a

resection with primary repair without creating excessive tension on the anastomosis, which may lead to

hemorrhage or scarring with recurrent coarctation. An alternative strategy is necessary in these cases.

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Patch aortoplasty may be performed in children in whom further growth is anticipated.107,108 The

subclavian flap repair augments the narrowed aorta using native arterial tissue. Blood flow to the left

arm is maintained by collateral vessels, although long-term studies have demonstrated a slight

discrepancy in limb length in some patients. Prosthetic patch material may also be used. By avoiding

circumferential prosthetic material, growth potential of the native aorta is preserved. The disadvantage

of patch repair is a high risk of aneurysm formation. In adults, in whom growth is no longer a concern,

resection of the coarctation may be performed with subsequent placement of a prosthetic interposition

graft (either Dacron or polytetrafluoroethylene).

One of the principal concerns during coarctation repair is interruption of distal aortic blood flow,

especially to the spinal cord. The anterior spinal artery is fed by major radicular branches from

intercostal arteries. In patients without well-formed collaterals, ischemia of the spinal cord may be

precipitated by aortic cross-clamping, and paraplegia may result. Protective measures include induction

of mild hypothermia, maintenance of a high proximal aortic pressure, and minimization of cross-clamp

time. In older patients, distal aortic perfusion may be maintained by the technique of left heart bypass,

in which oxygenated blood is taken from the left atrium and delivered to the femoral artery or distal

aorta using a centrifugal pump.109 This is usually not necessary due to the presence of significant

collaterals. Overall, the incidence of paraplegia following coarctation repair is less than 1%.110

Following repair, patients may develop severe hypertension. This can be managed using intravenous

beta blockers (e.g., esmolol). Uncontrolled hypertension can lead to the complication of mesenteric

arteritis. Hypertension usually resolves within days to weeks after repair, although older children and

adults may require lifelong antihypertensive therapy. Repair of coarctation during infancy is thought to

minimize the risk of late hypertension.111

Transcatheter intervention for primary therapy of discrete coarctation in young children and

adolescents remains controversial. Technical success rates range from 80% to 98%, with reintervention

rates of 10% to 20%.112–114 Placement of a stent has been associated with higher success rates and lower

restenosis rates

114; however, the long-term outcome of stents in this population remains unknown, and

stents are not an ideal option in younger children. There is no evidence to date, therefore, that

demonstrates superiority or equivalence of catheter intervention compared to surgery. In addition, there

is a high complication rate of 5% to 11.7%, including recurrent coarctation, need for multiple

interventions, injury to the femoral vasculature (for access), aortic dissection, and aneurysm

formation.113,115–117 On the other hand, balloon angioplasty is widely accepted for the treatment of

recurrent coarctation following surgery, in which the success rate is on the order of 90% with low

recurrence rates.118–120

The early mortality following repair of coarctation in neonates is 2% to 10%, whereas the risk in

older children and adults is about 1%.106,121 The incidence of recurrent coarctation following resection

and end-to-end repair is about 4% to 8%.106,122,123 The long-term survival following repair of

coarctation is determined by the presence of associated defects and the persistence of hypertension.

PATENT DUCTUS ARTERIOSUS

The ductus arteriosus is a normal fetal vascular structure that allows blood from the right ventricle to

bypass the high-resistance pulmonary vascular bed and pass directly to the systemic circulation. The

ductus communicates between the main PA (or proximal left PA) and the proximal descending thoracic

aorta. Histologically, the media of the ductus contains a predominance of smooth muscle cells, whereas

the media of the aorta and PA contain well-developed elastic fibers. Vasocontrol of the ductus is

mediated by two important mechanisms: oxygen tension and prostaglandin levels. During fetal

development, low oxygen tension and high levels of circulating prostaglandin maintain ductal patency.

During the final trimester, the ductus becomes less sensitive to prostaglandins and more sensitive to the

effects of oxygen tension. Following birth, the rise in oxygen tension and a fall in prostaglandins (which

were previously supplied principally by the placenta) lead to ductal closure, which is usually complete

by 12 to 24 hours. After closure, the ductus becomes a fibrous cord known as the ligamentum

arteriosum. Failure of closure of the ductus leads to the condition called PDA. PDA occurs in about 1 out

of 1,200 live births and accounts for 7% of congenital heart defects.7 The incidence is much higher in

premature infants (>20%).124 This elevated incidence is thought to be related to immaturity of the

ductal wall resulting in impaired sensitivity to oxygen tension.

PDA may occur as an isolated defect, or it may occur in association with a number of other anomalies.

Patency of the ductus arteriosus is desirable in a number of defects in which there is either inadequate

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