Coarctation of the Aorta and Interrupted Aortic Arch

Coarctation

Coarctations vary in severity. When stenosis is localized, the lumen must be reduced in cross-sectional area by more than about 50% before there is a hemodynamically important pressure gradient across it, but longer tubular coarctations may be hemodynamically important with lesser narrowing. Thirty-three percent of autopsy specimens (patients aged 2 years to adulthood) examined prior to the era in which operation was available show moderate luminal narrowing, 42% severe (pinhole) stenosis, and 25% luminal atresia. Occasionally the adult aorta may be redundant and severely kinked opposite the ligamentum arteriosum, without any pressure gradient; this is called a pseudocoarctation lesion.

The localized morphology of classic coarctation is a shelf, projection, or infolding of the aortic media into the lumen. It is most prominent in that portion of the circumference opposite the ductus arteriosus (the posterior and leftward wall). This inward projection is present also on anterior and posterior walls but absent on the ductal side (inferior or rightward wall). The shelf is usually marked externally by a localized indentation or waisting of the left aortic wall as if a string had been placed around it, pulling the aorta toward the ductus ( Figs. 48-1 and 48-2 ). External narrowing may be absent in the young infant. The aorta beyond the narrowing usually shows poststenotic dilatation, and paradoxically the wall beyond the stricture is usually thicker than that just proximal to it where the pressure is higher. The localized shelf or curtain of media and intima lies adjacent to the ductus arteriosus in utero and to the ligamentum arteriosum if the ductus closes. The shelf may be preductal or postductal but is usually periductal. Hutchins pointed out that the histologic features of this aortic media infolding are identical to those seen at a branch point of the normal aorta.

In addition to infolding of aortic media, there is usually a localized ridge of intimal hypertrophy (intimal veil) that extends the shelf circumferentially and further narrows the lumen. This, and perhaps other portions of the coarctation area, consists of ductal tissue. It forms a sling that completely surrounds the periductal aorta, which may progressively proliferate after birth and cause restenoses after repair of coarctation in neonates and young infants. It is well documented that use of PGE ₁ can result in symptomatic relief of a critical coarctation in some young infants by relaxing the coarctation site without reopening the ductus.

Rodbard has presented experimental and theoretical evidence that lowering of lateral pressure on the aortic wall secondary to the increase in velocity that occurs across a site of narrowing (according to the Bernoulli principle) allows the intimal cells to multiply until probe patency is reached. Resistance to flow across this stenosis then lowers the velocity so that ingrowth usually stops.

Rudolph and colleagues postulated that prevalence and type of coarctation are related to fetal flow patterns through the ductus and aorta. These investigators have shown that flow through that portion of the arch between origins of the left common carotid and left subclavian arteries in the normal fetal lamb is approximately half that across the ductus, explaining the normally smaller diameter of the arch compared with the ascending and descending aorta in the normal human newborn. A localized shelf opposite the ductus may result from a reorientation of the angle at which the ductus meets the aorta, which results in abnormal fetal flow patterns in some types of cardiac anomalies. The tendency for a shelf to develop is present when ductal flow is increased more than usual relative to isthmus flow; for example, with a ventricular septal defect (VSD). However, intrauterine events that account for the relatively frequent association of coarctation with lesions that produce left-to-right shunts postpartum are not fully identified.

Coarctation, as well as isthmus hypoplasia, is more common than usual when ascending aorta flow is diminished during fetal life (and ductal flow is relatively increased) by lesions such as aortic stenosis or atresia (see Chapter 47, Chapter 49 ), and mitral stenosis or regurgitation (see Chapter 50 ). Conversely, prevalence of coarctation is severely reduced and size of the isthmus increased when pulmonary flow and thus right-to-left ductal flow is decreased by lesions such as pulmonary stenosis or atresia, tetralogy of Fallot, and tricuspid atresia. Coarctation is uncommon when the aortic arch is right sided, presumably because of alteration of ductal and isthmus flow patterns in this situation.

Distal Aortic Arch Narrowing

Narrowing of the isthmus —the segment of aorta between a discrete coarctation and the left subclavian artery—commonly exists with coarctation. Narrowing of the distal aortic arch between the left subclavian and left common carotid arteries also coexists commonly, particularly in neonates and infants ( Fig. 48-3 ). This narrowing appears in some cases to be a transient finding related to prenatal flow pattern (excessive ductal flow extending proximally in the aorta and out the left subclavian artery), which reduces flow in the distal aortic arch between the left subclavian and left common carotid arteries and allows this segment to narrow. This view leads to the inference that surgical enlargement of the distal arch at the time of coarctation repair is unnecessary because it will, in any event, gradually enlarge after the coarctation is repaired (see under Indications for Operation later in this section). Others believe that the narrowing in this area is a coexisting congenital anomaly and that the narrow area must be widened surgically at the time of coarctation repair. There is evidence that unrepaired arch hypoplasia, at least in some cases, does not grow adequately, requiring repeat surgery. Whether isolated distal aortic arch narrowing exists as a congenital anomaly in the absence of localized coarctation and results in a pressure gradient is arguable. It probably does, but uncommonly. In an interesting study comparing 23 patients with coarctation (ranging in age from 1 month to 26 years, median 4.6 years) to normal controls, the proximal arch, distal arch, and isthmus were significantly smaller in the coarctation group; however, the subaortic diameter, aortic root, ascending aorta, and descending aorta were larger.

Proximal Aortic and Arterial Walls

Although coarctation itself, as well as dimensions of adjacent portions of the aorta, has received considerable attention through the years, only in recent years has evidence emerged to indicate that:

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  The wall of the entire aorta proximal to the coarctation is abnormal.

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  The abnormalities extend out to all major arteries supplied by the aorta proximal to the coarctation.

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  These abnormalities may be primary ones that have developed in utero.

Coarctation has been documented by fetal echocardiography in utero as early as 21 weeks of gestation, but it likely exists much earlier. Hypoplasia of the isthmus and, in some patients at least, the distal aortic arch develops during intrauterine development. It is hypothesized that either the coarctation was present very early in development and the hypoplasia is secondary, or the hypoplasia is related to a primary aortic wall abnormality rather than to the coarctation. Or the hypoplasia and coarctation are a result of altered patterns of blood flow caused by intracardiac abnormalities that lead to decreased flow to the arch and increased flow to the ductus during fetal development.

Degenerative changes occur in the peripheral arterial vasculature proximal to the coarctation, and these changes persist after coarctation repair and can be identified in children. Surrogate markers of arteriosclerosis, such as impaired flow-mediated vasodilatation and increased intima media thickness, were apparent in a study group with a mean age of 12 years.

Collateral Circulation

Collateral circulation between aorta proximal to the coarctation and that distal to it is one of the striking features of coarctation. When well developed, it is responsible for some of the classic signs of the malformation, such as parascapular pulsations and rib notching. It is usually present to some extent in newborns but increases in size and extensiveness as the patient ages ( Fig. 48-4 ).

Inflow into the collateral circulation is widespread, but is primarily from branches of both subclavian arteries, particularly internal thoracic, vertebral, costocervical, and thyrocervical trunks. Outflow from the collateral system is primarily into the upper descending thoracic aorta. The largest vessels participating in this outflow are usually the first two pairs of intercostal arteries distal to the coarctation. These are the third and fourth intercostal arteries, and they are greatly enlarged by the large reversed flow (outflow from collateral circulation). This reversed flow into the aorta can be documented by magnetic resonance imaging (MRI) and has been demonstrated at operation by directional Doppler velocity detector probes. Flow returns to a normal direction immediately after coarctation repair. Only the intercostals carrying this large reversed flow are sufficiently enlarged to produce rib notching, which explains lack of notching of the first and second ribs, whose intercostals arise above the coarctation. The lower intercostal arteries provide less outflow from the collateral circulation, as do the inferior epigastric artery and other branches of the abdominal aorta.

Collateral circulation and its clinical manifestations are altered by anatomic variations associated with classic coarctation. Associated stenosis at the origin of the left subclavian artery excludes this artery as an important source of inflow into the collateral circulation; thus, rib notching occurs only on the right side. When the right subclavian artery arises as the fourth aortic branch (see Morphology in Section I of Chapter 51 ) and distal to the coarctation, it does not serve as a source of inflow, and rib notching occurs only on the left side.

Aneurysm Formation

Enlarged, tortuous third and fourth intercostal arteries may become aneurysmal, but this is rare before about age 10 years. Resulting thin-walled aneurysms are usually saccular and are most likely to occur at the aortic origin of intercostal arteries. This is a weak point of surgical importance; if an enlarged intercostal artery must be ligated, the ligature should be placed a few millimeters beyond its aortic origin.

The aorta itself may become aneurysmal adjacent to the site of maximal narrowing as a result of hemodynamic effects, aortic dissection, or mycotic aneurysm. This is uncommon in young children. Prevalence of aneurysm is about 10% by the end of the second decade of life, 20% by the end of the third decade, and probably even higher in older patients.

Coronary Arteries

Left ventricular hypertrophy occurring in untreated patients is accompanied by histologic changes in coronary arteries. In young patients, nonarteriosclerotic lesions are conspicuous in the intimal layer. These consist of degenerative and proliferative changes of the elastic fibers and excess collagenous tissue. The media thickens to about twice normal with a rich elastic fiber network and often hyaline changes. Mean total area of the coronary arteries is increased, so they have greater than normal capacity, presumably in response to increased metabolic requirements of the left ventricle. As a result of prolonged hypertension, arteriosclerotic changes are apt to occur more often and at a younger age. In adolescents and young adults, reduced myocardial perfusion reserve is apparent.

Atria

In newborn infants it is common for the “valve” of the foramen ovale to be prolapsed, causing left-to-right shunting. This prolapse often resolves after coarctation repair. A true secundum atrial septal defect (ASD) may also occur with coarctation. Moderate to large ASDs appear to show the same tendency to close when coarctation is present and when it is not. In about 10% of patients with ASD, however, intractable heart failure will develop in infancy following coarctation repair, requiring ASD closure. The best predictor of development of heart failure when ASD coexists with coarctation is small mitral valve diameter, not the size of the ASD itself.

Left Ventricle

Left ventricular hypertrophy without volume increase is present in most patients with coarctation within a few days of birth. This progresses as the patient ages and may be aggravated by associated cardiac anomalies.

The left ventricular outflow tract may be abnormal in patients with arch obstruction, particularly when a VSD coexists. The left ventricular papillary muscles may be abnormally positioned, typically with a reduced interpapillary distance.

Aortic Valve

A bicuspid aortic valve is common, although its exact prevalence is uncertain. In two autopsy series, it was 46% and 27%, with an additional 6% and 7%, respectively, with congenital valvar stenosis. Tawes and colleagues report that among 250 living children with long-term follow-up, 32 (13%) had clinical evidence of aortic valve disease (mainly stenosis but also regurgitation). When aortic regurgitation appears in coarctation, it is usually based on a bicuspid aortic valve combined with persistent hypertension. Bicuspid aortic valve is known to be associated with dilatation of the ascending aorta. In one study, presence of coarctation in this setting was not associated with increased magnitude or rate of ascending aortic dilatation. Another study indicates that patients with coarctation and bicuspid aortic valve have greater aortic root dilatation than those with coarctation and tricuspid aortic valves. In the presurgical era, aortic dissection was noted to occur in 19% of coarctation patients without bicuspid aortic valve, but in 50% of those with bicuspid aortic valve.

Intracranial Aneurysm

Coarctation and berry-type intracranial aneurysm coexist in some patients. Some instances of sudden death in untreated as well as treated coarctation are from rupture of the intracranial aneurysm. That coarctation, bicuspid aortic valve, and intracranial aneurysm are associated leads to the inference that coarctation is only one manifestation of a diffuse arteriopathy.

Coarctation as Part of Hypoplastic Left Heart Physiology

Coarctation (with or without a patent ductus arteriosus, and with or without hypoplasia of the isthmus or distal aortic arch between left common carotid and left subclavian arteries) sometimes coexists with anomalies that also affect left ventricular function and structure directly (see Morphogenesis and Morphology in Chapter 49 ). This is particularly a problem in symptomatic neonates and infants. These anomalies include:

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  Hypoplasia of ascending aorta

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  Supravalvar, valvar, subvalvar, and anular aortic stenosis or hypoplasia

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  Aortic atresia

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  Left ventricular hypoplasia or hypertrophy

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  Endocardial fibroelastosis

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  Mitral stenosis with or without a single papillary muscle (parachute mitral valve)

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  Supravalvar mitral ring

When these occur in any of a number of possible combinations, they represent hypoplastic left heart physiology ( Table 48-1 ) if the left heart is unable to sustain the systemic circulation (see Chapter 49 ).

Multiple associated anomalies within the left heart are not unusual even when a functional left heart is present in early infancy. Levine and colleagues have shown that additional left heart obstructive lesions develop late in more than 20% of patients originally diagnosed in early infancy with isolated coarctation. A predictor of these additional anomalies is mitral valve diameter with a z score less than −1 on the original echocardiogram. A broad spectrum of sizes of important left heart structures can exist without negatively affecting left heart function.

Coexisting Cardiac Anomalies

When coarctation first presents in older children and young adults (as it did in the early years of cardiac surgery, but uncommonly now), coexisting cardiac anomalies are uncommon. When it presents in neonates, and to some extent in infants, coexisting cardiac anomalies are common ( Table 48-2 ). These associations are explained by the fact that survival beyond infancy is much less likely when coexisting anomalies are present; thus, long-term survivors tend to have simple lesions. Because in the current era most coarctations are diagnosed in neonates or infants, it follows that prevalence of associated anomalies found in neonates with coarctation closely approximates true prevalence.

Patent ductus arteriosus is present in almost 100% of neonates and in most infants with a preductal type of coarctation. This is considered part of isolated coarctation rather than an additional anomaly. Tubular hypoplasia of the distal aortic arch is also considered to be part of the anomaly of coarctation rather than an associated anomaly. ASD is not considered as an additional anomaly unless large enough to need closure. This excludes the fairly numerous examples of infants presenting with a left-to-right shunt through a stretched patent foramen ovale that may subsequently close. Anomalous right subclavian artery occurs in about 1% of cases of coarctation and may be proximal or distal to the coarctation. This variation does not appear to affect the collateral circulation that develops in any clinically significant way.

Approximately 82% of individuals born with coarctation have it as an isolated lesion (with or without continuing patency of the ductus arteriosus). About 11% have an important coexisting VSD, and approximately 7% have other important coexisting cardiac anomalies. These prevalences are different from those in patients who become symptomatic during neonatal life or infancy and require early intervention (see Table 48-2 ).

Prevalence of isolated coarctation in patients with an otherwise normal heart appears to be about 40 per 100,000 live births. Persons with pulmonary stenosis or atresia, tetralogy of Fallot, and tricuspid atresia with concordant ventriculoarterial connection have a prevalence of coarctation close to 0 per 100,000. Patients with aortic stenosis and mitral stenosis or regurgitation have a considerably higher prevalence than patients with otherwise normal hearts. Patients with VSD and other lesions such as transposition, double outlet right ventricle, truncus arteriosus, atrioventricular septal defect, and single ventricle who have associated VSD also appear to have a relatively high prevalence of coexisting coarctation. This may relate to altered blood flow patterns within the heart that result in less flow across the aortic isthmus during fetal development.

Neonates and Infants

Severe heart failure in a neonate or infant requires that coarctation be considered, especially when a favorable response to medical treatment does not occur promptly. It may be unsuspected in complex lesions when the baby is in extremis, because even when the ductus is closed, a large left-to-right shunt proximal to the aorta can decrease manifestation of hypertension in the arms. Severe proximal obstructing lesions (aortic or mitral stenosis) can have a similar effect. Control of heart failure and tachycardia in these situations frequently unmask differential pressures in upper and lower extremities as cardiac output improves.

Signs and symptoms of coarctation presenting in the neonate are those of heart failure. After a variable period of well-being, tachypnea, feeding problems, and sweating develop. On examination, there is a gallop rhythm and a systolic murmur along the left sternal edge and usually posteriorly over the coarctation site. Femoral pulses are absent or reduced in volume and delayed compared with radial or brachial pulses, although in small, sick infants with tachycardia, pulse delay may be difficult to detect. Blood pressure is higher in the arms than in the legs (by >20 mmHg). Delay in onset of heart failure is probably related, at least in isolated coarctation, to the variable time it takes for the ductus to close. Ductal closure usually commences at the pulmonary end, and generally it is not until the aortic end closes that the periductal aortic shelf produces severe obstruction (see Morphology earlier in this section). Thus, femoral pulses can be normal at birth but absent at 1 week.

When the ductus arteriosus remains widely patent and a severe coarctation lies proximal to it (preductal coarctation), there may be a right-to-left shunt into the descending aorta and, classically, cyanosis of the toes and sometimes the left hand while the right hand and lips remain pink (differential cyanosis). Femoral pulses are normal, and there is no ductus murmur. In fact, differential cyanosis is uncommon, either because flow through the coarctation is large or because P o ₂ of the pulmonary artery blood is high from an additional intracardiac shunt through a VSD, an interatrial communication, or both. Moreover, despite presence of a severe coarctation proximal to a patent ductus arteriosus, systemic vascular resistance in the lower compartment usually exceeds pulmonary vascular resistance, so the ductal shunt is left to right or bidirectional.

In infancy, hypertension may be present but is seldom severe, and a collateral circulation is not palpable, although it is usually present angiographically ( Fig. 48-5 ). Marked cardiomegaly is almost invariable on chest radiograph. The electrocardiogram (ECG) usually shows right ventricular hypertrophy in the first few months of life, even with isolated coarctation. About two thirds of infants operated on in the first year of life have right ventricular hypertrophy or combined hypertrophy, and fewer than 25% have pure left ventricular hypertrophy.

Left-to-right shunt through a stretched patent foramen ovale is common in infants with severe coarctation in heart failure. When heart failure disappears, so does the atrial shunt. Congenital aortic stenosis may not be evident clinically (or by catheter withdrawal pressure differential) in infancy, and yet it may be severe enough to require surgical relief at age 2 to 5 years, particularly when it is subvalvar (see Section II in Chapter 47 ).

Childhood (Age 1 to 14 Years)

Almost all patients who first present at age 1 to 14 years are asymptomatic unless they have important associated anomalies. Tawes and colleagues noted that children with associated anomalies may present in heart failure up to age 3 years, and Patel and colleagues noted heart failure in 7 of 65 children (11%) age 1 to 14 years. Subarachnoid hemorrhage from rupture of a berry aneurysm occurs occasionally but is rare in children younger than 7 years, and spontaneous paresis or paraplegia caused by dilated intercostal arteries compressing the anterior spinal artery or by epidural hemorrhage is even less common. Hypertension occurs in almost 90% of patients.

The chest radiograph shows cardiomegaly in 33% and rib notching in about 15% ( Fig. 48-6 ), but this feature does not occur before age 3 years. ECG shows predominantly left ventricular hypertrophy, with right ventricular hypertrophy present only when there is pulmonary hypertension with elevated pulmonary vascular resistance. ECG is normal in about one third of children.

Adolescence (Beyond 14 Years) and Adult Life

Many adolescent and young adult patients remain asymptomatic and are diagnosed at routine examination because femoral pulses are noted to be absent or reduced and delayed in the presence of a cardiac murmur, hypertension, or an abnormal chest radiograph. Hypertension is common and more severe than in younger patients, and heart failure may occur after about age 30 years. Heart failure is preceded by effort dyspnea, cardiomegaly, and important left ventricular hypertrophy on ECG. Headache, nose bleeds, fatigue, and calf claudication occasionally occur. Collaterals are usually palpable or audible posteriorly. Radiographic findings include a “figure-3” sign in the left upper mediastinal shadow ( Fig. 48-7 ) and, almost always, rib notching. (Absence of rib notching in the right chest suggests an anomalous origin of the right subclavian artery and in the left chest a stenosis of the left subclavian artery origin.)

Associated Syndromes

There is an association between Turner syndrome and von Recklinghausen disease and coarctation. Rarely, patients with coarctation have Noonan syndrome or congenital rubella.

Special Diagnostic Methods

Two-dimensional echocardiography can visualize coarctation in neonates and small infants ( Fig. 48-8 ) and is usually the definitive study. Associated intracardiac defects can also be defined in detail. Severity of coarctation can often be assessed by characterizing intracardiac and great artery blood flow patterns using color Doppler signaling. Fetal echocardiographic measurements of the z value of the aortic isthmus and the isthmus-to-ductus ratio are sensitive indicators of postnatal coarctation. Outside infancy, echocardiography may still be helpful but is usually not definitive. In moderate or mild coarctation, presence of an open ductus may obscure a coarctation at echocardiographic examination. This is due partly to altered blood flow patterns associated with the patent ductus, but more importantly to the fact that the coarctation itself may evolve as the ductus closes.

MRI and computed tomography (CT) are currently the imaging modalities of choice for coarctation in patients beyond infancy. Excellent detailed imaging of pertinent vascular structures can be obtained, often exceeding the detail seen with aortography ( Fig. 48-9 ). Three-dimensional rendering can be particularly informative ( Fig. 48-10 ). Post-surgical changes also can be defined in detail ( Fig. 48-11 ). Hemodynamic data can be assessed by MRI and may be particularly useful in older patients with well-developed collaterals, or in patients with restenosis, in whom there may be little or no gradient across the coarctation site. Assessment of flow in the collaterals directly, and quantitation of the flow increase in the aorta at the diaphragm compared with the flow in the upper aorta near the coarctation (as a measure of collateral flow), can be more accurate in determining the significance of the coarctation or recoarctation.

Cardiac catheterization and aortography , once the standard for diagnosis in older patients, now play a secondary role and are used mainly when hemodynamic data are important in determining management of the patient. A withdrawal gradient is present at rest across the coarctation, and in borderline cases, measurement of cardiac output and gradient during exercise helps assess severity. Severity of the coarctation can be better assessed on aortography than by catheter withdrawal pressures, mainly because collateral flow may increase the pressure in the aorta distal to the coarctation. Aortography also reveals any hypoplasia of the isthmus or arch, arrangement of the aortic arch branches, degree of collateral circulation, and presence of an aneurysm. Intracardiac hemodynamics can provide important information when there is concern about valve function, myocardial function, or pulmonary hypertension.

Isolated Coarctation

This category includes patients with or without associated patent ductus arteriosus.

Coarctation Associated with Ventricular Septal Defect

Most infants born with a large VSD and coarctation develop severe heart failure in the first month. By contrast, presentation so early is uncommon in patients with isolated large VSD (see under Natural History in Section I of Chapter 35 ). Unless the VSD rapidly diminishes in size, most of these babies die within a few months without surgical treatment. However, in many the VSD rapidly becomes small (see Fig. 35-21 in Chapter 35 ), and the natural history then becomes essentially that of isolated coarctation.

Coarctation Associated with Other Major Cardiac Anomalies

The combination of coarctation with other major cardiac anomalies nearly always produces severe heart failure during the early weeks of life. Without surgical treatment, from 80% to 100% of such babies die in their first year of life.

All reported series show a high proportion of associated cardiovascular anomalies in patients with coarctation presenting in infancy (see Table 48-2 ). In such infants, isthmus and arch hypoplasia is almost constant as a consequence of disturbed fetal blood flow patterns (see Morphology earlier in this section). In many of these infants, particularly those with complex and severe intracardiac anomalies, the natural history is primarily that of the associated anomaly. However, associated severe coarctation undoubtedly precipitates early heart failure.

Preparation, Incision, and Dissection

Neonates and Infants

After anesthetic induction, body temperature is allowed to drift down to a nasopharyngeal temperature of about 35°C. This downward drift is helped by reducing the operating room temperature to about 18°C (65°F) and by using the cooling mode in the heating-cooling pad under the child. Blood pressure in the right arm is monitored by an indwelling radial or brachial artery catheter. Near-infrared spectroscopy can be used to monitor tissue oxygenation both proximal and distal to the coarctation. Substantial changes in tissue oxygen values both above and below the coarctation have been documented with varying technical maneuvers; however, these changes have not yet been correlated with clinical adverse events.

The patient is positioned in full lateral position, secured with strapping across the hip and onto the operating table, with a sandbag tucked against the front of the chest ( Fig. 48-12, A ). Approach is made through a left posterolateral thoracotomy, with the entry through the fourth intercostal space. For this, the intercostal muscles may be incised in the center of the interspace or entry made via the fifth rib bed, elevating the periosteum from the superior half of this rib and incising the rib bed rather than the intercostal muscles. Care is required posteriorly because careless elevation of the periosteum too far in this direction or attempts to dislocate the costotransverse joint will result in excessive bleeding from collaterals. In most cases, the trapezius muscle need not be incised. Scoliosis is well documented following left thoracotomy in infants and children ; however, it is not known whether minimizing trauma to chest wall muscles and ribs will reduce this late development.

The rib spreader is inserted and opened in stages to avoid rib fractures ( Fig. 48-12, B ). The lung is retracted anteriorly, and the mediastinal pleura is opened over the aorta downward for several centimeters below the coarctation site and upward to include the distal arch and subclavian artery and, if necessary for arch hypoplasia, all the brachiocephalic arteries. Numerous closely placed stay sutures are placed along each side of the pleural incision, and the ends are gathered into clamps for exposure ( Fig. 48-12, C ). No other retractors are then required. The left superior intercostal vein is ligated and divided.

Keeping dissection in the areolar tissue just superficial to the adventitial aortic coat, the proximal left subclavian artery, the distal transverse arch, and the aortic isthmus are dissected. All dissection is kept close to the aorta, in part because this is the best plane of dissection and in part to minimize the possibility of damage to the thoracic duct. “The Abbott artery” occasionally arises from the medial aspect of the isthmus and, when present, should be ligated and divided. Next, with great care to avoid damaging the intercostals and bronchial arteries, the aorta beyond the coarctation is dissected. It is occasionally necessary to divide one or more bronchial arteries medially. Finally, the ductus arteriosus or ligamentum arteriosum is dissected. If the nasopharyngeal temperature has not decreased to about 35°C, and especially if the patient is hyperthermic, the left pleural space is lavaged with ice-cold saline for the few minutes required to accomplish the repair (see “Paraplegia after Aortic Clamping” under Special Situations and Controversies in Chapter 24 ).

Resection and Primary Anastomosis

Neonates and Infants

Some form of this operation is currently the preferred technique for young patients. Preparations for operation, incision, and dissection are described previously under “Preparation, Incision, and Dissection.” Once the coarctation is resected, there are various options for reconstruction, each of which is described in this section.

When the coarctation is well beyond the origin of the left subclavian artery, the proximal clamp is usually placed across the aorta to include the origin of the left subclavian artery. The distal clamp is placed on the aorta below the third and fourth set of intercostal arteries. The ligamentum arteriosum or ductus arteriousus, which has been tied at its pulmonary end, is transected at its aortic insertion. The aorta is transected proximal to the coarctation at a level that ensures removal of any narrowed portion of the isthmus as well as the coarctation ( Fig. 48-13, A ). Similar transection of the aorta is made beyond the coarctation, where the aortic diameter is usually ample.

The suture line is made with a continuous simple suture of 6-0 or 7-0 absorbable monofilament suture, sewing “from within” for the posterior wall ( Fig. 48-13, B ). After the posterior row of sutures has been placed, the ends of the aorta are approximated by the assistant and the sutures are pulled up snugly. The remainder of the anastomosis is completed by suturing the anterior wall using the other end ( Fig. 48-13, C ). Finally, the clamps are removed as described under “Immediate Post-Repair Management” and the operation completed similarly ( Fig. 48-13, D ).

When the coarctation is near the takeoff of the left subclavian artery, or when the segment between it and the subclavian artery is importantly hypoplastic, proximal transection is begun just beyond the origin of the left subclavian artery.

When the distal portion of the aortic arch between the left common carotid and subclavian arteries is hypoplastic, as it often is in neonates and young infants, the operation may be modified so as to enlarge this area. In young patients, end-to-end anastomosis is easily accomplished after extended resection, and the distal transverse arch and aorta proximal to the coarctation are widened by the procedure. Alternatively, hypoplasia in the distal arch and even the proximal arch can be managed by placing the curved proximal side-biting clamp to occlude the proximal arch just distal to the brachiocephalic artery origin, occluding both the left carotid and left subclavian arteries, in preparation for performing an end-to-side distal aorta to arch reconstruction (see Fig. 48-14, A ). After resecting the discrete coarctation, the isthmus is ligated with a 5-0 polypropylene ligature, and the undersurface of the proximal arch is incised opposite the left carotid artery origin and extended to the point opposite the left subclavian artery origin. The cut end of the descending aorta, trimmed of all ductal tissue, is connected to the incision in the undersurface of the arch with an end-to-side anastomosis using a running suture technique with 6-0 or 7-0 absorbable monofilament suture ( Fig. 48-14, B and C ).

Resection with end-to-end anastomosis can be combined with subclavian flap aortoplasty (see “ Subclavian Flap Aortoplasty ” in text that follows) if there is concern about the size of the aorta just beyond the subclavian artery. This problem is better managed by resection with extended end-to-end anastomosis or resection with end-to-side anastomosis, as described earlier; however, the combined operation will be briefly described for completeness. After preparing the subclavian artery and placing clamps as for the standard subclavian flap repair, the coarctation area is excised as described for standard end-to-end anastomosis. The proximal and distal aortic segments are reconstructed with an end-to-end anastomosis, with the exception that the posterior wall and anterior wall continuous suture lines are not tied to each other posterolaterally after their completion. Rather, each suture line is tied to itself posterolaterally, leaving a small posterolateral gap. The subclavian artery is split open longitudinally, and incision is extended into the proximal aortic segment, then carried through the small suture line gap onto the distal aortic segment. The subclavian flap is sewn into position as described previously in the standard subclavian flap method, straddling across the end-to-end anastomosis.

Subclavian Flap Aortoplasty

Currently this technique is most frequently used selectively in neonates, when circumstances make resection and reconstruction inappropriate—for example, when it is advantageous to preserve the ductus in the setting of a borderline left ventricle (see Indications for Operation later in this section). PGE ₁ infusion is maintained throughout the procedure (see Fig. 48-12, A and B , which illustrate the exposure). To begin the subclavian flap aortoplasty, dissection of the subclavian artery is carried distally to expose the branches. It is ligated and divided proximal to all branches, none of which are ligated ( Fig. 48-15, A ). The ductus arteriosus is dissected, and a delicate vascular clamp, such as a temporary neurovascular clip, is placed across the ductus. A delicate vascular clamp is placed across the aortic arch between the left common carotid and left subclavian arteries, and a second clamp is placed well distal to the coarctation but proximal to the intercostal arteries, allowing space above and below the coarctation for the incision, as shown by the dotted line in Fig. 48-15, A . Uncommonly, it must be placed beyond the third pair of intercostal arteries (the first set beyond the coarctation), which are then controlled with removable metal clips or vessel loops made from heavy suture material.

The subclavian artery, before its transection, is split open longitudinally along its posterior margin, carrying this incision across the coarctation into the dilated distal aorta for at least 1 cm. Stay sutures are placed on either side at the level of the coarctation. The subclavian artery is transected just proximal to the ligature. Sharp corners at the end of the opened subclavian artery are trimmed; if the subclavian flap is unusually wide, the lateral edge is trimmed so that its width is about 1.5 times the diameter of the aorta. The turned-down subclavian flap may be tacked to the distal opened aorta using a double-ended 6-0 or 7-0 absorbable monofilament suture, which is then carried proximally as a continuous stitch ( Fig. 48-15, B ). Alternatively, the suture line may be started proximally on the medial side and carried just beyond the inferior angle of the aortic incision; another suture line is then started proximally on the lateral side and carried down to the previous one. Absorbable monofilament suture material 6-0 or 7-0 is used. Angles at either end of the turned-down subclavian flap must lie beyond the level of the coarctation, achieving this when necessary by sliding the flap distally in the process of suturing. In this manner, a proper “cobra head” is achieved. Following completion, the aortic clamps and the neurovascular clamp on the ductus are removed ( Fig. 48-15, C ).

Modifications of the subclavian flap repair have been used successfully.

Repair of Coarctation Proximal to Left Subclavian Artery

When hypoplasia occurs proximal to the left subclavian artery, the usual methods of repair can be unsatisfactory. When the situation is encountered in infants, a reversed subclavian flap aortoplasty may be used, or resection with end-to-side anastomosis as described earlier in this section and shown in Fig. 48-14 can be performed.

The reverse subclavian flap combined with end-to-end anastomosis is illustrated in Fig. 48-16 . After usual exposure and dissection, the left common carotid artery and aortic arch between this and the subclavian artery are completely dissected. Clamps are placed on the left common carotid artery and on the aorta just proximal to this vessel and on the aorta distal to the left subclavian artery. The subclavian artery is ligated and divided distally. The subclavian artery is split down its medial side and the incision extended proximally onto the arch and the origin of the left common carotid artery ( Fig. 48-16, A ). The subclavian artery is turned down, in reverse to the classic subclavian flap operation, and sewn into place ( Fig. 48-16, B and C ). Alternatively, the end-to-side anastomosis of the descending aorta to the arch, as described earlier in this section under “Resection and Primary Anastomosis,” can be used. In addition, when an anomalous right subclavian artery is present, it can be used in the reconstruction to address arch hypoplasia.

In older patients, replacement of the coarcted area with an interposed tube graft may be done when the coarctation is severe, but techniques for aneurysms of the distal portion of the transverse aortic arch are necessary (see “Replacement of Aortic Arch” under Technique of Operation in Chapter 26 ). The simpler palliative placement of a bypassing polyester tube graft between the ascending aorta and lower descending thoracic aorta via a right thoracotomy may be used, but is less satisfactory and should be reserved for particularly complex recurrent arch obstructive problems (see Special Situations and Controversies later in this section for further discussion).

Repair When Aneurysm Is Present

When an aneurysm is present, either in the intercostal arteries (single or multiple) or aorta (see Morphology earlier in this section), resecting the segment of aorta involved along with the coarctation is required, and continuity is reestablished with an interposed tubular polyester graft. This procedure can be hazardous, particularly in regard to hemostatic control of the large intercostal artery feeding into the aneurysm. Pharmacologically induced hypotension is helpful to dissection. Early placement of the proximal aortic clamp and then ligation and division of the ligamentum arteriosum and placement of a clamp across the coarctation itself allows transection of the aorta proximal to the coarctation. Then gentle forward traction on the clamp across the coarctation allows the distal aorta and posteriorly placed intercostal artery aneurysm to be brought into better view for dissection and management.

Postrepair paraplegia is a greater hazard than usual because of the need to sacrifice intercostal arteries (see “Paraplegia after Aortic Clamping” under Special Situations and Controversies in Chapter 24 ). Special precautions required for all aneurysm surgery in this area are used (see “Replacement of Descending Thoracic Aorta” under Technique of Operation in Chapter 26 ).

Repair of Persistent or Recurrent Coarctation

Several options are open to the surgeon. The choice is partly determined by morphologic details of the obstruction and partly by surgeon preference. Resection and primary anastomosis, subclavian flap repair with or without resection, patch aortoplasty, and placing an interposition graft can all be considered. Repeat left thoracotomy is feasible in selected cases with discrete obstruction that does not involve the arch; however, most cases require median sternotomy and cardiopulmonary bypass (CPB). Results are excellent.

In particularly difficult technical situations in older patients, a bypassing polyester tube graft on the left or right side may be all that is possible. This is most conveniently performed through a right thoracotomy. The end of a properly prepared polyester tube is anastomosed to the side of the intrapericardial portion of the ascending aorta using a side-biting clamp on the aorta. A side-biting clamp is placed on the descending aorta, just above the diaphragm, the tube graft is routed posterior to the right pulmonary hilum, and end-to-side anastomosis is performed. Intermediate-term results are generally good. Alternative extra-anatomical approaches have been described.

Repair of Persistent or Recurrent Coarctation with Aneurysm

Aneurysm following coarctation repair is more likely when transverse arch hypoplasia is present. The aneurysm may be very large and thin walled, with rupture almost a certainty over a 15-year period. These cases represent a major challenge and must be addressed directly. The option of “indirect management,” such as by an extra-anatomical bypass graft, is contraindicated because of the rupture risk. Standardized management techniques have not been established, but they include surgical, interventional, and hybrid techniques. Optimal outcomes will be achieved with a multidisciplinary team including a cardiac surgeon, interventional cardiologist, and radiologist. The variables that influence treatment strategy include the severity of residual stenosis or hypoplasia, location of the aneurysm relative to the obstruction, suitability of “landing zones” for transcatheter devices, patient age and comorbidity, and likelihood of exclusion of the left subclavian artery or other brachiocephalic artery. Surgical management can vary but typically requires CPB, either via median sternotomy or left thoracotomy, with resection of the aneurysm and obstructive segment and interposition graft insertion. These procedures carry a mortality risk of 14% to 23%, and therefore endovascular management should be considered when anatomic details are favorable.

Repair from an Anterior Midline Approach

Particularly in neonates and young infants, coarctation of the aorta can be well repaired from an anterior midline approach using CPB. Although use of hypothermic circulatory arrest is advocated by some, continuous CPB with antegrade cerebral perfusion can be used routinely for this repair ( Fig. 48-17 ). The midline approach is particularly useful when concomitant repair of intracardiac defects is contemplated, but it can also be used to advantage when coarctation is accompanied by severe hypoplasia of the proximal transverse arch, or when there is no proximal arch segment because the left carotid and brachiocephalic arteries share a common origin (“bovine” trunk) in association with hypoplasia of the segment between this common brachiocephalic trunk and the left subclavian artery.

Technical and CPB considerations are similar to those involved with repair of interrupted aortic arch (see Section II ). The anterior midline approach has also been described for both children and adults with coarctation and other complex arch problems using interposition conduits.