Surgical Approach to Coarctation of the Aorta and Interrupted Aortic Arch

Coarctation is a term derived from the Latin coarctation, meaning a drawing or pressing together. More precisely, coarctation refers to a narrowing of the lumen of a vessel producing an obstruction to flow. A localized segment of narrowing is called a coarctation, whereas a diffuse segment of narrowing is known as tubular hypoplasia.

Coarctation was once described as infantile and adult; however, these descriptions were not accurate because both types can be observed in either age group. As our understanding of the pathophysiology of coarctation evolved, the terms preductal and postductal were often used to categorize coarctation in relation to the ductus arteriosus. Although this anatomic description remains true, the exact location usually does not change the presentation; this knowledge has led to the unified description of most neonatal coarctation as juxtaductal.

Meckel originally noted coarctation on autopsy in 1750, and Morgagni again noted it in 1760. Forty-four years after Paris provided the first accurate description of coarctation of the aorta in 1791, Legrand made the first diagnosis in a living patient in 1835. Bonnet was the first to categorize coarctation into infantile and adult forms, which were later revised to preductal and postductal forms.

Blalock and Park proposed the first surgical repair in 1944, describing a bypass from the left subclavian artery to the aorta to circumvent the area of narrowing. Crafoord and Nylin performed the first resection with end-to-end reanastomosis in 1945, whereas Gross used homografts to replace the narrowed segments of aorta. In 1966, Waldhausen and Nahrwold performed the first subclavian-flap aortoplasty. More recently, advanced interventional cardiology techniques have led to an interest in percutaneous transluminal aortoplasty for both native coarctation and recoarctation.[1]

Coarctation

Coarctation is defined as a narrowing of the lumen of the aorta that obstructs flow. Variations of coarctation depend on the length of the involved segment. Typically located at the insertion of the ductus or ligamentum arteriosum, a localized coarctation may occur at any point along the length of the aorta. Coarctation rarely occurs at multiple sites, a phenomenon sometimes observed in Turner syndrome. Diffuse long-segment coarctation, also known as tubular hypoplasia, is typically found at the aortic isthmus (ie, the segment between the left subclavian artery and the insertion of the ductus). With extreme coarctation, the entire transverse arch may be hypoplastic.

Pseudocoarctation

Souders first described pseudocoarctation in 1951. Often discovered on simple chest radiography, the aorta has an abnormal contour. Aortography shows a tortuous, kinked aorta with no gradient. Kinking or buckling of the aorta changes the healthy conformation of the aorta but does not obstruct flow. Once thought benign, aneurysmal dilation can occur distal to the affected area, leading to the specter of rupture of the aorta. Current therapy requires close follow-up care. Aggressively pursue surgical repair after the aorta begins to demonstrate progressive dilation.

Complete interruption of the aortic arch

Complete interruption of the aorta, or interrupted aortic arch (IAA), is a fairly rare condition. First described in 1778 by Steidele, IAA accounts for less than 1.5% of all instances of congenital heart disease. Complete interruption of the aorta is usually associated with other anomalies, including DiGeorge syndrome (29% incidence).[2] In 1955, Samson performed the first known surgical correction of IAA. Sirak performed the first repair in a neonate in 1968.

Defined as a complete absence of a segment of the aortic arch, the description of IAA is based on the absent segment. In 1959, Celoria and Patton developed the following classification of IAA[3] ; Schreiber et al provided the percentages in 1997[2] :

• Type A (13%): Interruption occurs between the left subclavian artery and the descending aorta.

• Type B (84%): Interruption occurs between the left subclavian artery and the left common carotid artery.

• Type C (3%): The absent segment occurs between the left common carotid artery and the innominate artery.

• Subtypes A1, B1, and C1: All describe an anomalous origin of the right subclavian artery from the distal aorta.

Although the cause is unknown, IAA is associated with defects that decrease ascending aortic flow and increase ductal flow. As with coarctation, abnormal fetal blood-flow patterns are theorized to substantially contribute to the etiology of IAA.

Previously uniformly fatal, the development of prostaglandin E1 (PGE1) therapy to maintain ductal patency has greatly improved surgical results by allowing time to optimize the patient's hemodynamic state before surgery. The prognosis of patients with IAA is poor if the condition is uncorrected. The mean age at death is 4-10 days, with 90% dying within the first year of life. After repair, the 10-year survival rate has improved from approximately 47% to 81% in non-complex cases and 54% in complex cases.[4]

Noncomplex cases included concomitant ventricular septal defect (VSD), aortopulmonary window, or left ventricular outflow tract obstruction. Complex cases included concomitant Taussig-Bing double-outlet right ventricle and truncus arteriosus. Risk factors for increased mortality included primary aortic anastomosis, presence of complex anomalies, and initial IAA repair before 1994.

Whether a staged repair or a single operation should be used to repair IAA remains controversial. Median sternotomy is still preferred if correction of associated anomalies is to occur concomitantly. Methods of surgical correction are similar to those of coarctation repair and include end-to-end anastomosis of the remaining segments with or without patch augmentation, end-to-side anastomosis of the arch vessel with either the proximal or distal segment, or use of an interposition graft to take the place of the missing segment. Long-term probability for reintervention remains high regardless of operative technique.[4, 5, 6]

Ohye et al describe operative techniques for IAA with special circumstances in the second edition of Mastery of Cardiothoracic Surgery.[7] These include IAA with aortic valve hypoplasia or atresia, IAA with truncus arteriosus, IAA with transposition of the great arteries, and IAA with single ventricle.

Mortality

Most data demonstrate that mortality rates decrease and outcomes improve with increasing experience. In their series, Schreiber et al demonstrated that early mortality rates decreased from 42% in 1975-1985 to only 17% in 1985-1995, which was a result of improved surgical techniques and advances in the preoperative and postoperative treatment of neonates.[2] Immediate surgical intervention remains the only therapy. IAA is a difficult surgical problem, although the most recent results have been encouraging, with increased survival and decreased morbidity rates.

Frequency

Observed in 1 in 3000 to 1 in 4000 autopsies, coarctation accounts for approximately 5-10% of cases of congenital heart disease. Isolated coarctation is more common in males than in females, whereas the incidence of complex lesions is equal in males and females. The birth prevalence of coarctation for patients in 1980-1994 was 0.32 case per 1000 live births.[8]

Although the cause of coarctation remains controversial, 2 major theories are supported by the current literature.

Muscular theory

The muscular theory suggests that extension of tissue from the ductus arteriosus (a muscular artery) extends into the aorta (an elastic artery) during development. When the ductus contracts and fibroses at birth, it leads to a narrowing of the aortic lumen.

Theory of abnormal fetal blood-flow patterns

The second theory is related to abnormal fetal blood-flow patterns. During fetal development, the aortic isthmus is a watershed area, as the ascending aorta receives blood from the heart, sending it to the head, while the descending aorta receives ductal blood to send to the rest of the body. As a result, the initial diameter of the isthmus is small, and if the proper molecular cues are not present, it may not grow sufficiently. The incidence of coarctation is increased in disorders in which an obstruction of the left ventricular outflow tract reduces ascending aortic flow. In converse, the incidence is decreased in disorders in which decreased ductal flow is present, such as tetralogy of Fallot.

Combination of theories

Although both theories provide ample evidence, a combination probably best encompasses the likely etiology.[9]

Common associated anomalies of coarctation of the aorta include bicuspid aortic valve, VSD, patent ductus arteriosus, and various mitral-valve disorders. Congenital aortic stenosis, aortic atresia, and hypoplastic left heart syndrome are less common. Coarctation of the aorta may be observed in transposition of the great vessels, particularly when the right ventricular outflow tract is obstructed. Data suggest that more than 70% of VSDs that occur with coarctation may close spontaneously.[10, 11] Coarctation is observed in as many as 50% of patients with the Taussig-Bing anomaly.[12, 13] A genetic or familial basis may be involved because 15-36% of children with Turner syndrome may have coarctation.

The pathophysiology of untreated coarctation revolves around the associated hypertension. A 3-pronged hypertensive response occurs in the presence of coarctation. Blood pressure is mechanically affected at all levels and at the level of the kidneys, and recent data suggest that hypertension evolves from an endothelial process as well.

The natural history of coarctation depends on the age of the individual at presentation and on the associated anomalies. Symptomatic infants have a high mortality rate, and those who survive to adulthood still have greatly decreased life expectancy, even with surgical correction. The data have changed somewhat over the years with the introduction of antibiotics and improved neonatal care; however, untreated coarctation still results in a grave prognosis.

In 1928, Abbott reviewed 200 cases with coarctation in patients older than 2 years and found that 34% died by the time they were aged 40 years, with an average age at death of 42 years. At that time, the 3 major causes of death were spontaneous rupture of the aorta, bacterial endocarditis, and cerebral hemorrhage.

Neonates usually present with left ventricular failure as a result of severe and acute afterload, which is further exacerbated by acidosis. This acidosis results from diminished peripheral flow secondary to the coarct itself, in addition to the failing left ventricle.

Twenty years later, in 1947, Reifenstein reviewed 104 cases and found little change, with an average age at death of 35 years. The 2 leading causes of death were unchanged. By 1970, the results had improved somewhat; however, the mortality rate was still 75% by the time a person with coarctation was aged 46 years.[14] In persons with untreated coarctation, the coronary arteries have intimal degeneration, medial thickening, and increased mineralization, all of which are secondary to the hypertension associated with untreated disease.

The clinical presentation of patients with coarctation depends on their age at presentation and on the presence and severity of any associated anomalies. The 2 clinically significant variants, preductal and postductal coarctation, can manifest in different ways.

Preductal coarctation

Preductal coarctation is associated with an increased incidence of cardiac defects, and the patient may present with congestive heart failure (CHF) if a VSD is present. A preductal defect does not change normal fetal blood-flow patterns. As a result, no collaterals form in utero. If blood flows through the patent ductus arteriosus, pulses are often palpable in the lower extremities. Symptoms develop as the ductus closes, leading to a clinically significant obstruction.

Upon clinical examination, the infant is often irritable and disinterested in feeding. Tachycardia is often present. Few findings may be apparent on physical examination in a healthy-appearing infant. However, in the uncompensated patient, differential cyanosis may be observed between the upper body and the lower body. A systolic murmur may be present over the left precordium or between the scapulae on the patient's back. An infant who is compensating (ie, one with a left-to-right shunt through a patent foramen ovale) should have a substantial systolic blood-pressure gradient between the arms and the legs.

Physical findings in a neonate who is decompensating and critically ill may differ substantially. The blood-pressure gradient is often absent secondary to diminished cardiac output. Hypotension, oliguria, and severe metabolic acidosis are concurrent with severe coarctation, as blood flow to the kidneys and all distal structures is drastically impaired. In severe obstruction or in IAA, diagnosis by physical examination can be obscured as long as the ductus remains patent because the pulmonary artery pulse is palpated in the femoral arteries.

Paraductal and postductal anomalies

Paraductal and postductal anomalies are often isolated defects, and the incidence of associated anomalies is low. Later in life, patients may present with headache, epistaxis, or visual disturbances. Exertional dyspnea and stroke are other presenting symptoms.[15]

Coarctation can be clinically diagnosed depending on the available evidence, as described above. To summarize, hypertension or a systolic blood-pressure gradient between the arms and legs may be observed. Checking the patient's blood pressure in both arms is important because an anomalous origin of the right subclavian distal to the coarcted segment may be present. A systolic murmur over the left precordium or between the scapulae may be heard, and the femoral pulses may be absent or diminished with a delayed upstroke. In children older than 5 years, look for the signs of collateral circulation (ie, enlarged and palpable collateral vessels, audible bruits, and dilatation of the intercostals [rib notching]).

The presence of coarctation alone is usually indication for surgery. Timing of the operation and the method of repair are decisions to be made. Symptomatic infants often require urgent surgery. However, the patient's condition must be stabilized with medical therapy before the coarctations is repaired. Neonates often present with profound acidosis and respiratory distress. An infusion of prostaglandin E1 (PGE1) may be administered within a month of birth and often opens a closed ductus.

The most relevant anatomy for understanding coarctation of the aorta is the aortic arch, the great vessels, and the insertion of the ductus. Because coarctation and interrupted aortic arch (IAA) can occur anywhere along the arch, being able to recognize the origins of the great vessels, especially on aortography, is important. The ductus arteriosus is a remnant of the sixth left aortic arch; it connects the pulmonary trunk with the aorta in utero and attaches to the lower concave surface of the aortic arch directly opposite the left common carotid and left subclavian arteries. The left recurrent laryngeal nerve hooks around the lower border of this structure and can easily be damaged if care is not taken to avoid it.

Generally considered a life-saving procedure, repair of coarctation has few absolute contraindications. Coexisting illnesses or anomalies in an infant (eg, necrotizing enterocolitis) make take initial precedence in treatment. Sepsis is likely the greatest relative contraindication to surgery. This condition is related to the overall inflammatory response and to edema formation observed with the septic immune response. Dissection into the periaortic space is made more difficult that is otherwise would be, and the crucial tension-free anastomoses are considerable more difficult to construct than they are in other situations.

Arterial blood gas

ABG analysis may be ordered to look for acidosis, which is common in severe coarctation in a newborn. The results of ABG analysis are nonspecific.

Electrocardiography

Another nonspecific but noninvasive examination, ECG may reflect signs of right, left, or biventricular hypertrophy, or they findings may be entirely normal in older children and adults.

Left ventricular hypertrophy with strain is a common late finding in severe coarctation.

Chest radiography

Chest radiography may reveal little more than left ventricular hypertrophy in a mild case of coarctation. However, several other findings are considered pathognomonic of coarctation.

The classic sign of rib notching, which Meckel first described in 1827. This sign may be clearly evident on posteroanterior radiographs. The notching, a result of dilated intercostal arteries eroding the lower edge of the rib, may be absent in older patients who have not developed collaterals. It is usually absent in young patients (usually < 5-6 y) who have not had time to develop clinically significant collaterals.

The reverse-3 sign is another classic radiologic finding in coarctation. Observed en face, the upper part of the 3 is formed by the dilated proximal segment coming down into the coarcted segment, whereas the bottom portion of the 3 is formed by the coarcted segment exiting into the normal distal segment of the aorta.

Chest computed tomography scanning

CT scanning of the chest may be useful in evaluating complex abnormalities and in making the diagnosis in adults.

Angiography

Angiography was considered the criterion standard. However, CT and MRI have replaced angiography as their resolution has improved. See the image below.

Magnetic resonance imaging

MRI is similar to CT scanning in that it is most helpful in assessing complex abnormalities. The resolution of MRI is better than that of CT scanning; however, the long exposure times necessary for MRI make it a more difficult to perform in infants than a 30-second rapid spiral chest CT scan. See the image below.

The risks associated with the sedation necessary for adequate imaging likely outweigh any additional benefit.

Echocardiography

Echocardiography has gained favor in relatively recent years because its resolution has dramatically increased and its processing power has been improved.

Two-dimensional echocardiography can demonstrate the site of coarctation and helps in evaluating for other cardiac anomalies. Color Doppler flow can suggest the magnitude of pressure gradients.

Because of its portability, accuracy, and noninvasive nature, echocardiography is the diagnostic test of choice in neonates. Neonates seldom require angiographic study, except in rare cases when the area cannot be visualized well and when the abnormality cannot be effectively ruled out.

Advances in transesophageal echocardiography have made it the diagnostic test of choice during surgery, and it provides an excellent noninvasive means for postoperative follow-up care.

The most important disadvantage of echocardiography is a consequence of its noninvasive nature. Because the pressure gradients are not measured directly, they may not be as accurate as angiographically determined gradients.

Intravascular ultrasonography

IVUS is an imaging technique recently used in the diagnosis and treatment of coarctation. Capabilities include measurement of the diameter of the aorta, coarctation, and length of the lesion. This information guides the selection and deployment of stents. It also provides a means by which the endovascular repair can be followed.[16]

Cardiac catheterization

This invasive examination is not typically considered necessary because coarctation rarely involves the coronary arteries. Patients with coarctation are at risk for coronary disease later in life because of the latent effects of hypertension; therefore, cardiac catheterization may be useful in a patient examined for recoarctation at an older age.

Angiography and aortography

Considered the most objective method of analysis, angiography and aortography have many benefits; however, less invasive diagnostic techniques have largely replaced these studies.

Angiography and aortography reflect the location and extent of the coarctation, it delineates any great-vessel involvement, it facilitates the evaluation of any associated cardiac defects, and it allows for the direct measurement of pressure gradients.

Angiography and aortography are particularly useful in evaluating recurrent coarctation because balloon angioplasty can be performed at the time of the procedure if necessary.

Ductal tissue stains lighter than aortic tissue because of its low elastin levels. In a normal aorta, the inner one third of the elastic lamellae of the aorta merges into the internal elastic lamina of the ductus, whereas the outer two thirds should merge into the adventitia.

In coarctation, ductal tissue often encircles the lumen of the aorta. As the ductus attempts to close soon after birth, ductal tissue encroaching on the aorta constricts as well, narrowing the aortic lumen.

This ectopic tissue growth is not present in all patients. This observation led to the proposal that coarctation is not a result of abnormal tissue growth, but rather, a result of abnormal fetal blood-flow patterns.[17]

The role of medical therapy in coarctation is limited. Medical therapy is confined to preoperative temporization to optimize the patient's hemodynamic status before surgery.

Since 1984, medical therapy of coarctation has revolved around the introduction of prostaglandin E1 (PGE1) therapy. PGE1 allows for reopening of the ductus arteriosus and perfusion to the lower body. When PGE1 therapy is effective, the severe acidosis and oliguria, which are often present, are corrected by reestablishing blood flow to the lower body. Optimizing the patient's hemodynamic status and converting an otherwise emergency procedure into an elective one can substantially reduce the mortality risk.

For additional information, please see Coarctation of the Aorta.

The European Society of Cardiology (ESC) updated their 2010 guidelines on the management of adult congenital heart disease (ACHD) in 2020.[18, 19]  Their class I recommendation is that repair of coarctation or recoarctation (surgically or catheter based) is indicated in hypertensive patients with an increased noninvasive gradient between the upper and lower limbs confirmed with invasive measurement (peak-to-peak ≥20 mmHg); catheter treatment (stenting) is preferred when technically feasible.[18, 19]

Several techniques are currently used to repair coarctation of the aorta. The method of repair is usually tailored to each patient. To help determine the operative approach, consider the length of the segment involved and whether associated anomalies are present.[20]

Several surgical methods of repair are used, including end-to-end reanastomosis, subclavian flap aortoplasty, prosthetic patch onlay grafts, and interposition grafts (see Intraoperative details), as well as sternotomy for an approach to the ascending aorta and aortic coarctation, and an ascending-to-descending aortic bypass.

Many variations of the described procedures have been used throughout the years, including modification of the subclavian flap that include reimplantation, end-to-end anastomosis using the subclavian to enlarge the anastomosis, and ascending aorta–to–descending aorta bypass grafts. All of these techniques may be useful depending on the individual anatomy and associated anomalies.[21, 22, 23]

Extra-anatomic correction, ascending-descending aorta via a median sternotomy with cardiopulmonary bypass support, seeks to provide additional blood flow to the distal aorta, but the stenosed aorta remains in place.[22]  Proximally, an anastomosis is created between a prosthetic conduit and the ascending aorta or the subclavian artery; distally, the prosthetic conduit is anastomosed to the descending aorta, bypassing the area of aortic coarctation. This technique is particularly valuable during concomitant cardiac procedures (aortic valve replacement, coronary artery bypass grafting).[22]

The repair of associated anomalies at the time of aortic coarctation repair remains controversial. Optimal management remains unclear. If concurrent repair of associated anomalies is to be attempted at the time of coarctation repair, the best approach is by means of a median sternotomy.[24] Coarctation repair is then carried out in a manner to that used to repair an interrupted aortic arch (IAA).

Current knowledge suggests ligation and division if a patent ductus is present. A bicuspid aortic valve can usually be left untreated. Strategy for concurrent ventricular septal defect (VSD) repair remains somewhat unclear. Previous studies indicated greatest survival in patients who underwent coarctation repair with pulmonary artery banding; but this has fallen out of favor due to the frequency of subsequent avoidable procedures and associated morbidities. If preoperative congestive heart failure (CHF) does not resolve, a second operation is required to close the VSD. If the VSD does spontaneously close, a debanding procedure is required.

Numerous VSDs associated with coarctation do spontaneously close, avoiding the need for cardiopulmonary bypass; this leads some to favor a 2-stage procedure. In 1992, Park et al demonstrated that this suggestion was a feasible option in 23 infants younger than 3 months, 9 of whom required no further treatment.[11] Six required early closure of the VSD, and 8 required late repair. Seven more were older than 3 months, and none required repair of the VSD.

More recent reports attempt to outline predictors of spontaneous VSD closure. Considerations in decision for simultaneous VSD repair include the magnitude of the shunt through the VSD, the likelihood of persistent symptoms in the postoperative period, and whether the VSD is a type likely to spontaneously close. Initial coarctation repair is ideal when the VSD is likely to close, a band is not required, and arch hypoplasia is not present. Large size defects, defined as those with diameter greater than 50% of the aortic valve annulus, and types other than muscular such as perimembranous, inlet, outlet, and malaligned are less likely to close.

Proximal arch hypoplasia is best addressed through a midline sternotomy to alleviate the risk of recurrent obstruction, thus a combined repair strategy is favored in this situation.[25] Despite the controversy, many surgeons simply prefer to repair a clinically significant VSD when the coarctation is addressed to avoid the obvious disadvantages of the two-stage approach.

Dutta et al reported on the results of a study of 31 patients who underwent repair of coarctation of aorta with associated cardiac defects, through a midline sternotomy; coarctation and when necessary, the distal arch, was repaired prior to cardiopulmonary bypass. The overall event-free survival rate was 88.5% at both 2 and 3 years of post-surgical follow-up. The investigators concluded that repair of coarctation and distal arch hypoplasia or type I arch interruption is feasible prior to cardiopulmonary bypass without the use of hypothermic circulatory arrest or regional cerebral perfusion, with acceptable results.[26]

In a retrospective analysis, Kanter et al described in detail the advantages and disadvantages of the 1-stage and 2-stage approaches and introduce the 1-stage 2-incision approach.[27] All approaches have similar survival and rates of recoarctation, but the 1-stage 2-incision method results in shorter lengths of stay and corrects all defects at once without palliation and without the use of circulatory arrest or regional perfusion. The study advocates strategy selection on an individual basis.

End-to-end reanastomosis

One of the most common methods of repair is resection of the involved segment with end-to-end reanastomosis. This repair is usually reserved for infants and small children because of the absence of enlarged collaterals and the short distance for reanastomosis. In adolescents and adults, direct anastomosis is challenging because of large collaterals and the length of the aorta necessary for adequate repair.

Note the following:

• Place the patient in the right lateral decubitus position. The arterial line should be placed in the right radial artery, and a blood pressure cuff is placed on the right arm and lower extremity.

• Make a left posterolateral thoracotomy incision.

• Retract the lung anteriorly and inferiorly to allow for identification and incision of the pleura that overlies the descending aorta.

• Perform careful dissection from the proximal aorta at the level of the innominate artery takeoff, to the ductus, and then as far distal as safely possible. This step includes mobilizing the intercostals arteries. The present authors prefer not to sacrifice the intercostal vessels if at all possible.

• Avoid damage to the left recurrent laryngeal nerve, the vagus nerve, and the phrenic nerve, all which lie in the dissection field.

• After the plane of dissection is developed, the critical component of the procedure is resection of the entire coarcted segment and ductal tissue, followed by reconstruction of the aorta without clinically significant tension on the anastomosis.

• In general, heparin 100 units/kg is systemically administered.

• The aorta is cross-clamped at the proximal aspect just beyond the innominate artery takeoff and at the distal aspect about 1 interspace below the coarctation. The intercostal vessels may be controlled with a vessel loop or clip.

• The ductus is then ligated and divided if necessary. Ligating the ductus before aortic clamping creates a possibility of a ductal tear, which may be catastrophic.

• The involved aortic segment is then resected.

• Using a continuous absorbable monofilament suture (eg, Maxon, PDS), create the anastomosis. Release the distal aortic clamp before tying the suture to avoid "purse-stringing" of the anastomosis.

• At the termination of the procedure, identify any residual gradient by measuring the patient's blood pressure in the lower extremity by comparing that pressure to the pressure in the right arm.

• Transesophageal echocardiography can be useful to estimate the gradients during surgery.

• Benefits of this particular technique include avoidance of prosthetic materials, excision of ductal tissue, preservation of the left subclavian artery, total relief of left ventricular outflow obstruction, and growth potential of the aortic anastomosis.

Subclavian-flap aortoplasty

A second commonly employed method is the subclavian-flap aortoplasty, as follows:

• For this procedure, perform a left thoracotomy. The initial dissection follows that of the end-to-end anastomosis.

• Identify the left subclavian and ligate it at the first branch. Ligate the vertebral artery to avoid subclavian steal.

• Make a lengthwise incision along the coarctation, continuing on to the subclavian and creating a flap.

• Then, resect the posterior shelf and turn down and place the subclavian flap to enlarge the constricted area, ensuring an adequate length.

• Benefits of this technique include avoidance of prosthetic materials, decreased cross-clamp time, and the possibility that the anastomosis may grow as the child ages.

Prosthetic-patch onlay graft

First performed in 1957, this technique has fallen out of favor because of the need for prosthetic implants and the risk of aneurysms and pseudoaneurysms.[28] The differential elasticity of the often-rigid grafts (historically made of Dacron) in relation to the supple aorta is believed to increase the rate of aneurysmal formation. Literature from more recent experience with homograft patch material (used extensively in arch reconstruction for hypoplastic left-heart syndrome) has not shown an increased rate of aneurysmal formation.

Note the following:

• With the prosthetic patch onlay graft, perform a left thoracotomy and make a longitudinal incision along the coarcted segment.

• In this case, do not resect the posterior shelf.

• Sew a prosthetic patch into place, thereby enlarging the lumen.

Interposition grafts

Interposition grafts are most often used in older patients who have exceeded their growth potential. Interposition grafts are also useful when the narrowed segment cannot be completely excised without making primary reanastomosis impossible. In 1951, Gross used aortic homografts as interposition grafts and reported no clinically significant complications in 70 patients other than graft calcification, which was present in less than 50%. Aneurysmal dilatation has not been reported. The technique of interposition graft is selectively used in individuals with complex coarctation, recurrence, or aneurysmal formation.

Always measure the arm and/or leg gradient after surgery to differentiate inadequate repair from true recoarctation. In the optimal case, perform exercise testing for best accuracy because some patients do not have a gradient except during and after exercise. Although exercise testing is not a feasible option in infants and neonates, it is an excellent test for follow-up observation of adolescent patients.

Follow-up care of the patient with coarctation can range from an office visit with physical examination and the measurement of arm and/or leg gradients to repeat aortography to directly measure any residual gradients and to identify any anatomic problems.

With the advent of advanced echocardiography, physicians are increasingly willing to rely on the noninvasive results obtained with this technique. Echocardiography can enable a good approximation of the anatomy, and it provides a good estimation of gradients.

Causes implicated in recoarctation include inadequate resection of ductal tissue, failure of anastomotic growth, and suture-line thrombosis.

Given the technical complexity of coarctation repair, the list of complications is remarkably short. Many of the complications are not specific to coarctation but are common with other cardiac procedures; these include hemorrhage, infection, chylothorax (from injuries to the thoracic duct), suture line thrombosis, and suboptimal repair or recurrence.

Numerous complications are unique to both aortic surgery and coarctation. A 2-phased phenomenon of paradoxic hypertension can occur after coarctation repair. During the first phase, systolic blood pressure rises throughout the first 24-36 hours after the operation. This rise is believed to result from activation of the sympathetic nervous system with elevation of serum catecholamine levels. A rise in diastolic blood pressure occurs later and is a result of activation of the renin-angiotensin system.

Another complication unique to coarctation repair is the postcoarctectomy syndrome of abdominal pain and distension that Sealy first described in 1957. As many as 20% of patients have this complication, and laparotomy may be necessary. In 1985, Kawauchi et al noted that mesenteric ischemia secondary to acute necrotizing arteritis appeared to be the cause.[29] Relatively recent data suggest that aggressive control of postoperative hypertension usually prevents the full-blown syndrome. In addition, this phenomenon appears to be associated with coarctation in older patients, as this complication is rarely seen with infants and small children.

The most worrisome complication after coarctation repair continues to be paraplegia, which occurring in 0.1-1% of neonates after coarctation repair. No definitive predisposing factors are known. Current data suggest that poor collaterals, anomalies of the origin of the right subclavian artery, distal hypertension during cross-clamp, reoperation, or relative hyperthermia during the operation may all contribute to the incidence of paraplegia. The incidence in the adult population undergoing coarctation repair rises proportionately with age and is as high as 2.6%.

The tremendous variation in spinal-cord blood supply, including the elusive artery of Adamkiewicz, makes predicting adequate collateral flow extraordinarily difficult. Some theories suggest that maintaining a distal aortic pressure of more than 60 mm Hg may help to prevent cord ischemia (as measured by means of maintenance of somatosensory evoked potentials), and some have suggested using a shunt to achieve this if necessary. In 1987, Cunningham demonstrated that distal hypertension with loss of somatosensory evoked potentials for more than 30 minutes resulted in a more than 70% incidence of paraplegia.[30]

Other complications include temporary or permanent hoarseness from recurrent injury to the laryngeal nerve. The nerve can be directly injured by transection or indirectly by retraction. Careful identification of the anatomy and knowledge of the course of the recurrent laryngeal nerve is critical to avoid this complication.

Outcomes from coarctation repair depend on several factors, most notably the patient's age at the time of operation, the method of repair, and the presence of associated anomalies.

The recoarctation rate with the end-to-end repair has historically approached 60%, with somewhat lower rates for subclavian-flap aortoplasty and prosthetic graft repair. However, recent studies have demonstrated that end-to-end repair favorably compares with other techniques, with recoarctation rates of only 5-10%.[9]

Some suggested reasons for this dramatic change are improved neonatal intensive care units and advances in vascular surgical technique and suture materials. Improved preoperative conditioning and increased use of prostaglandins have also contributed to lowered mortality rates. Circumferential suture lines were initially blamed for high rates of recoarctation; however, because this technique was perfected with the arterial switch operation, they should likely prove effective for coarctation as well. At this time, the current authors know of no prospective randomized trials that are being conducted to compare the repair techniques.

Overall mortality rates are still 2-10% in neonates, which includes those with intracardiac anomalies as well as those with coarctation.

A 1998 retrospective study of 176 patients by Seirafi and associates demonstrated an overall mortality rate of 7.4%.[31] Nine of 13 deaths were in patients with associated complex intracardiac anomalies. No mortality occurred in the 113 patients with isolated coarctation. A 15% incidence of residual or recurrent coarctation was reported, although neither the patient's age at operation nor the type of repair appeared to influence recurrence. The other major complication was persistent hypertension, which was associated with repair in patients older than 1 year (27% vs 4.2%).

In the same year, Backer and associates reported a series of 55 infants who underwent repair by using extended resection with end-to-end reanastomosis.[32] They reported a 5.4% mortality rate and a 3.6% rate of recurrence. The median age at surgery was 21 days. A total of 62% of surgeries performed through a left thoracotomy and the others through a median sternotomy with concurrent repair of associated anomalies. About 47% of patients had isolated coarctation, and 53% had at least 1 associated intracardiac anomaly, with ventricular septal defect (VSD) comprising 69% of those anomalies. Total resection of all ductal tissue was achieved.

In 2000, Allen and associates described a modified subclavian patch aortoplasty.[33] They demonstrated excellent results in 53 infants with no mortality and only a 4% incidence of clinically significant recoarctation. Of these instances, 49% were associated with cardiac anomalies. As with all techniques, the key features to this technique are a tension-free repair and a long aortotomy to help prevent restenosis.

A report from the Society of Thoracic Surgeons Congenital Heart Surgery Database looked at early outcomes in a large 95 center cohort of 5025 patients undergoing repair of coarctation of the aorta or hypoplastic aortic arch repair between 2006 and 2010.[34] Patients were divided into three groups with Group 1 consisting of coarctation or hypoplastic aortic arch without ventricular septal defect (VSD); Group 2, coarctation or hypoplastic aortic arch with ventricular septal defect; and Group 3, coarctation or hypoplastic aortic arch with other major cardiac diagnoses. Overall mortality was 2.4%; it was 1% for Group 1, 2.5% for Group 2, and 4.8% for group 3.  In 211 patients undergoing VSD closure, mortality was 4%; it was 1% for those undergoing pulmonary artery banding as a management strategy for the VSD; and it was 2% for those not underdoing intervention for the VSD mortality.  There were postoperative complications in 36% of patients. No injury to the spinal cord was noted. The investigators were unable to measure the recurrence rate or how it related to surgical technique.[34]

Despite some excellent outcomes, controversy remains over the use of flap aortoplasty in infants younger than 3 months. Potential pitfalls are associated with early use of this technique, most notably concern over the loss of the major vascular supply to the left upper extremity. Complications are rare (the left subclavian was historically divided for pulmonary systemic shunts, with complications occurring rarely); however, decreased growth and rare reports of ischemia and gangrene have been documented.[35] In addition, neonates most often have associated arch hypoplasia, which is better addressed with resection and end-to-end anastomosis than with other methods. Complete hypoplasia of the aortic arch is best addressed by means of arch reconstruction performed through a median sternotomy.

The prosthetic-path onlay technique has the advantages of a relatively short operating time, minimal dissection, maximal augmentation of the stenosed area, and maintenance of normal vascular anatomy. However, this technique has been associated with an aneurysmal-development rate of as much as 35%, and repeat operation is required in almost 20% of patients.[28]

Balloon angioplasty has been performed for more than 20 years; however, its use in coarctation remains controversial because of the formation of pseudoaneurysms and concerns about long-term patency. The surgical literature shows a high restenosis rate for neonatal (< 40 d) balloon angioplasty; 57% need surgical intervention. However, in the population with surgically treated restenosis (18%), secondary angioplasty is the treatment of choice, and no repeat interventions were necessary.[36]

A long-term randomized study of angioplasty versus surgery in children (3-10 y) showed that only 50% of patients treated with balloon angioplasty remained free of both aneurysmal formation and repeat intervention compared with 87.5% of surgically treated subjects.[37]

At present, the optimal timing and mode of treatment for patients with coarctation remains controversial. In neonates and young children, surgical intervention remains the criterion standard. It is well-tolerated, with excellent long-term efficacy due to an 88-96% 5 years freedom from reintervention. Balloon angioplasty carries a higher risk of complication and suboptimal outcome in as many as 19% of native coarctation cases. Stents overcome some of the problems inherent to simple dilation but are not without serious complications related to materials and biomechanics.

No evidence suggests superiority of an endovascular therapy over surgery for treatment of primary coarctation.[38] However, for patients with hemodynamic instability or for those who have undergone surgery for restenosis, angioplasty can be a palliative and potentially curative procedure. Al-Ata et al studied a series of infants with complex aortic coarctations and relative contraindications to surgery who underwent palliative stent implantation as a nondefinitive procedure.[39] Three of the four improved and eventually underwent definitive repair.

Stent placement in infants has also been studied, although (to the authors' knowledge) no long-term results have been reported. A report published in 2000 by Thanopoulos et al suggests that stent implantation can be performed with low morbidity and mortality rates and that no recoarctation was noted in any of the 17 patients who were examined at the age of 33 months.[7] Peak systolic gradients were reduced to just 2.1 mm Hg from 50 mm Hg. A report of retrospective study by Marshall et al in 2000 suggested that, although stent implantation was a feasible option for challenging cases, it was not without a risk of serious complications.[40]

Stent placement is still under investigation in adolescents and adults, and long-term data is still being released. A nonrandomized selection-biased case series describes initial and 5-year outcomes for stent placement to treat adult aortic coarctation. Complications included a single incidence of stent migration requiring percutaneous intervention and a femoral pseudoaneurysm requiring surgical correction. Complete relief of coarctation was achieved with no recoarctation.[41] A retrospective review of endovascular stent placement to treat thoracic aortic aneurysm following repair of aortic coarctation in a select few patients revealed promising, yet nondefinitive results.[42]

Fiszer et al implanted a new type of extra-large stent, the AndraStent XL/XXL, in 38 patients with native coarctation of the aorta (CoA) and 8 patients with recurrent coarctation of the aorta following prior surgery (ReCoA). The outcome was successful for all procedures, and the systolic gradient across the aorta decreased from 40.6 mmHg pre-procedure to 11.6 mmHg post-procedure (p< 0.001). The procedural outcome remained favorable during a mean of 2.4 years of follow-up, and at follow-up neither stent fracture nor dislocation was found in any patients.[43]

The future of aortic coarctation repair may include direct genetic intervention or in utero therapy, which may decrease the growth of ductal tissue into the main aorta or which may help alter neonatal blood flow in such a way to prevent coarctation completely. Until that time, surgical techniques will continue to improve, and the use of angioplasty should continue as studies continue to find the subset of patients in whom it will prove most useful.