Carl L. Backer1, Joseph A. Dearani2, and Constantine Mavroudis3 1UK HealthCare Kentucky Children’s Hospital, Lexington, KY, USA 2Mayo Clinic, Rochester, MN, USA 3Peyton Manning Children’s Hospital, Indianapolis, IN, USA The word coarctation originates from the Latin coarctere, to contract. A coarctation of the aorta is a congenital narrowing of the descending thoracic aorta, usually (but not always) occurring just distal to the left subclavian artery adjacent to the site of insertion of the arterial duct (arterial ligament). The occurrence rate is 0.2–0.6 per 1000 live births and coarctation of the aorta represents 5–8% of all cases of congenital heart disease [1, 2]. Coarctation of the aorta is the eighth most common congenital heart defect. Coarctation is often associated with other congenital heart defects, including patent arterial duct, bicuspid aortic valve, ventricular septal defect, and mitral valve abnormalities [3]. The clinical presentation of coarctation varies from cardiovascular collapse in infancy after ductal closure to asymptomatic hypertension in an adult. Robert Gross [4] experimented with repair of coarctation in animals in 1938, and documented the possible complications of severe hemorrhage and paraplegia. The first successful repair of coarctation of the aorta in a human was performed in Stockholm, Sweden in 1944 by Clarence Crafoord [5]. He resected a coarctation and performed an end‐to‐end anastomosis in a 12‐year‐old boy with severe hypertension. Crafoord’s patient had relief of hypertension and normalization of lower‐extremity blood pressure. The surgical management of coarctation of the aorta has evolved over the years, mainly in attempts to prevent recoarctation [6]. Other techniques described, in historical order, include prosthetic patch aortoplasty [7], subclavian flap aortoplasty [8], and resection with extended end‐to‐end anastomosis [9, 10]. There are many other techniques with subtle variations described for coarctation repair, including subclavian flap aortoplasty with preservation of arterial blood flow to the left arm [11], subclavian flap with resection of ductal tissue [12], coarctation resection with radically extended end‐to‐end anastomosis [13], end‐to‐side anastomosis of the descending aorta to the proximal aortic arch [14], also called aortic arch advancement [15], and ascending sliding arch aortoplasty [16]. Transcatheter therapy for coarctation of the aorta has evolved substantially in the past 10 years [17]. This chapter will review the embryology, anatomy, pathophysiology, natural history, diagnostic techniques, surgical and transcatheter alternatives, postoperative considerations, and complications for coarctation of the aorta. Coarctation of the aorta was first noted as an autopsy finding by Morgagni in 1760 [18]. He described a localized constriction of the descending aorta. In 1903, Bonnet [19] suggested dividing patients with coarctation of the aorta into two groups, infantile and adult. “Infantile” later became known as preductal, and “adult” as postductal. In the infantile group, the arterial duct is open and there is a tubular narrowing of the isthmus of the aorta proximal to the arterial duct. The arterial duct supplies the blood flow to the descending aorta (Figure 13.1A). In the adult type of coarctation, the arterial duct is closed and there is a shelf‐like narrowing within the lumen of the aorta (Figure 13.1B). The key difference between these two types is that the patent arterial duct provides blood flow to the lower extremity in the preductal (infantile) group and the arterial duct is closed in the postductal (adult) coarctation. The critical factors that determine the hemodynamic burden to the patient are whether the arterial duct is patent, the size of the transverse aortic arch, and the degree of narrowing at the coarctation site. In surgical series, particularly for evaluating outcome, a classification system of three groups of coarctation patients has been widely used: group I, patients with isolated coarctation; group II, patients with coarctation and ventricular septal defect; and group III, patients with coarctation and complex intracardiac anomalies other than isolated ventricular septal defect [20–22]. The classification system proposed by the International Nomenclature and Database Conferences for Pediatric Cardiac Surgery [23] is as follows: coarctation of the aorta, isolated; coarctation of the aorta, with ventricular septal defect; and coarctation of the aorta, with complex intracardiac anomaly. Other useful modifiers are isthmus hypoplasia and/or arch hypoplasia. The aortic arch can be divided into three parts, the proximal transverse arch (arch between the innominate and left carotid arteries), the distal transverse arch (arch between the left carotid and left subclavian arteries), and the aortic isthmus (arch between the left subclavian and insertion of the patent arterial duct). Isthmus hypoplasia is defined as present if the isthmus is less than 40% of the diameter of the ascending aorta [24]. Arch hypoplasia is defined as present if the proximal or distal transverse arch is less than 60% or 50%, respectively, of the diameter of the ascending aorta [25]. A relatively simple clinical definition of hypoplastic transverse aortic arch is when the transverse aortic arch dimension measured in millimeters is less than the weight of the patient in kilograms plus 1 [26]. Figure 13.1 (A) Infantile or “preductal” coarctation of the aorta. The patent arterial duct (PDA) provides the majority of blood flow to the descending aorta (Ao). There is tubular narrowing of the transverse arch and a small aortic isthmus. (B) Adult or “postductal” coarctation of the aorta. The area of narrowing is actually juxtaductal and consists of a prominent posterior ridge projecting into the lumen. The arterial duct has closed and is now an arterial ligament. PA, pulmonary artery. Source: Reproduced with permission from Backer CL, Mavroudis C, in Pediatric Cardiac Surgery, 3rd ed. Philadelphia, PA: Mosby, 2003, pp. 251–272. There are two complementary theories explaining the embryology of coarctation of the aorta: (i) the flow theory and (ii) the ductal sling theory. The flow theory is based on the hypothesis that blood flow through the cardiac chambers and great arteries during fetal life often determines their size at birth [27]. In a normal fetus, the left and right ventricles have approximately equal stroke volumes, although they function in parallel rather than in series. If there is an increase in blood flow through the right heart because of an intracardiac ventricular septal defect (VSD), then there is a decrease in flow through the left heart and hence the aortic isthmus. If there is an upstream left‐sided obstructive lesion (i.e., mitral or aortic stenosis), again, there will be less flow through the ascending aorta and the isthmus. This theory holds that coarctation of the aorta forms because of a lack of fetal blood flow across the aortic isthmus. The intracardiac defects that would cause coarctation on the basis of the flow theory are in fact clinically commonly associated with patients with coarctation of the aorta. These include VSD, bicuspid aortic valve, congenital aortic stenosis, and congenital mitral valve stenosis [3]. The hemodynamic disturbances in embryonic circulatory pathways that lead to reduced aortic arch flow need not be dramatic [28]. The role of the limbus of the foramen ovale is to deflect the appropriate proportion of the inferior caval vein blood to the ascending aorta. Prenatal narrowing of the foramen ovale or an improper angulation of its limbus can lead to variable degrees of hypoplasia of the left‐sided structures. This may explain Shone syndrome [29] (coarctation of the aorta, parachute mitral valve, supravalvar mitral ring of the left atrium, and subaortic stenosis). Corroborating evidence is the corollary that lesions that reduce right heart output such as tetralogy of Fallot, pulmonary stenosis, and tricuspid atresia are almost never associated with coarctation of the aorta [27]. The flow theory, however, is not very convincing for patients with no obvious intracardiac defects. For these patients the ductal sling theory is more appealing. More than 100 years ago, Skoda postulated that abnormal extension of contractile ductal tissue into the aorta is a significant factor in the pathogenesis of coarctation of the aorta [30]. More recently it has been microscopically shown that the obstructing shelf of coarctation can be composed of cells similar to that found in the arterial duct [31]. Careful histologic examination of resected coarctation specimens has demonstrated extension of ductal tissue in a circumferential sling extending from the arterial duct and into the adjacent aorta [32]. Contraction and fibrosis of this “ductal sling” at the time of ductal closure would lead to constriction of the aorta and a primary coarctation (Figure 13.2) [32]. There is confirmatory echocardiographic evidence for this theory [33]. This may explain the origin of coarctation of the aorta when there is no associated intracardiac lesion. Other investigators have advanced ideas that may also play some role in the embryology of coarctation of the aorta. Kappetein and colleagues believe that an abnormality of neural crest development plays a role in the pathogenesis of coarctation of the aorta [34]. There may also be genetic factors, given the increased incidence of coarctation of the aorta in females with Turner syndrome [35]. This syndrome was originally described in adult karyotype XO female patients with sexual infantilism, webbed neck, and cubitus valgus; 15–36% of these patients have associated coarctation of the aorta. Figure 13.2 Illustration of the extent of ductal tissue present in a coarctation of the aorta specimen. The white areas show the coarctation shelf, circumferential ductal sling, and the prolongations of ductal tissue distally in the aorta. Source: Reproduced by permission from Russell GA et al. J Thorac Cardiovasc Surg. 1991;102:596. The anatomic features of coarctation depend on the age of the patient, whether there is an associated patent arterial duct, and the degree of hypoplasia of the transverse aortic arch and isthmus. In a typical infant with coarctation of the aorta and patent arterial duct, there is often a diffuse narrowing of the aorta distal to the left common carotid artery. A large patent arterial duct the size of the descending aorta connects the descending aorta to the pulmonary artery. The opened aorta reveals a coarctation membrane proximal to the entrance of the arterial duct. There is minimal poststenotic dilatation of the descending aorta and only minor enlargement of the intercostal arteries. In an older child with a juxtaductal coarctation, there is often a visible external narrowing of the descending aorta at the level of the ligament. The degree of external narrowing, however, does not necessarily correlate with the inner lumen of the aorta, which will contain a shelf‐like concentric narrowing that may result in a pinpoint lumen (Figure 13.3). Rarely, there is complete occlusion of the lumen, and all flow to the descending aorta is from collateral arteries. The aorta proximal and distal to the coarctation is often dilated with enlargement of the proximal subclavian artery. The aortic wall may be very thin in the region of poststenotic dilatation. The intercostal vessels entering the descending aorta are large, thin walled, and may even become aneurysmal. Figure 13.3 Coarctation lumen in a 14‐year‐old child who underwent coarctation resection and placement of an 18 mm interposition graft. Lumen measures 3 mm. Source: Reproduced by permission from Backer CL et al., in Pediatric Cardiac Surgery, 4th ed. Oxford: Wiley‐Blackwell, 2013, pp. 257–282. Figure 13.4 Computed tomography angiogram showing severe coarctation of the aorta with near occlusion of the isthmus. Large collateral arteries are seen entering the descending aorta from various origins proximal to the coarctation site. Note the massively dilated bilateral internal thoracic arteries. Courtesy of Cynthia R. Rigsby. When a coarctation is present, there is progressive enlargement of collateral blood vessels around the coarctation. This collateral flow is predominantly from the subclavian artery and its branches: the internal thoracic, intercostal, scapular, cervical, vertebral, epigastric, and spinal arteries (Figure 13.4). These vessels enlarge steadily and in older children (more than 4 years of age) and adults the chest radiograph may show the characteristic “rib notching” of the inferior aspect of the ribs due to the presence of dilated and tortuous collaterals. These large collateral vessels provide enough flow to the lower body to maintain organ function and growth. Pseudocoarctation of the aorta is a rare condition, presumably resulting from a congenital elongation of the aortic arch [36]. The elongation leads to redundancy and “kinking” of the aorta, which may appear similar to a coarctation of the aorta but has no actual obstruction to blood flow (Figure 13.5) [37]. There is usually little or no demonstrable pressure gradient present in pseudocoarctation [37]. Because of the tortuous nature of the aorta, however, there is a tendency for dilatation and aneurysm formation, presumably related to turbulent flow beyond the kink [38]. These patients should be followed closely and surgical intervention may be required if dilatation compresses surrounding structures (i.e., esophagus) or aneurysm formation is discovered [39]. Coarctation of the abdominal aorta occurs in only 0.5–2% of all coarctations [1]. The embryology of abdominal coarctation may be congenital or related to congenital rubella, Takayasu arteritis, or von Recklinghausen disease [40]. In two‐thirds of cases the narrowing is circumscribed, and in one‐third there is a long diffuse hypoplasia. Diagnosis is confirmed by angiography. It is important to establish the status of the renal arteries in these patients. Effective surgical therapy has included patch aortoplasty and bypass grafts [41–43]. Figure 13.5 Pseudocoarctation. Aortogram showing a dilated ascending aorta, elongation of the arch, and kinking of the descending thoracic aorta in the region of the ligament. There was only a 20 mmHg systolic pressure gradient across the pseudocoarctation, but marked poststenotic dilatation of the descending thoracic aorta. Resection with interposition graft was performed to relieve dysphagia. Source: Reproduced by permission from Kessler RM et al. Ann Thorac Surg. 1993;55:1003–1005. The presentation of patients with coarctation of the aorta occurs in a bimodal distribution. There is a group that presents in the first week of life whose blood flow to the lower body is dependent on a patent arterial duct. If they are not diagnosed prior to ductal closure, they present in cardiovascular shock. Collateral flow is inadequate in infancy and ischemia of organs distal to the coarctation results in renal failure and acidosis. At the same time, the sudden increased afterload on the left ventricle results in acute left heart failure. The management of these neonates was greatly improved by the introduction of prostaglandin E1 (PGE1), which opens and maintains the patency of the arterial duct. PGE1 was initially used (1975) successfully for infants with cyanotic heart disease (pulmonary atresia, transposition of the great arteries) [44], and later (1979) applied to infants with aortic arch interruption and coarctation of the aorta [45]. Intravenous infusion of PGE1 dilates and maintains the patency of the arterial duct, which normalizes perfusion to the lower body and unloads the left ventricle. In some patients PGE1 may not open the patent arterial duct, but it does improve flow through the coarctation site by acting on the “ductal sling” tissue [33]. This slight increase in coarctation orifice diameter is often enough to help stabilize the patient prior to elective surgical repair. The use of PGE1 combined with intubation and ventilation, intravenous inotropic support, and intravenous sodium bicarbonate acts to correct the low output state and reverse metabolic acidosis and renal failure. Surgical intervention can then be planned on a semielective basis at a time when the function of the various organ systems has been optimized. In our series of patients, PGE1 therapy was effective in allowing cardiac and organ system recovery in over 95% of cases. Figure 13.6 Survival curve of patients with coarctation of the aorta surviving the first year of life compared with normal subjects. Source: Reproduced by permission from Campbell M. Br Heart J. 1970;32:633–640. The other arm of this bimodal presentation is a group of patients who are “asymptomatic” but present with hypertension on a routine physical examination. The main cause of symptoms in these patients is the proximal systemic hypertension, which may cause headaches or epistaxis. They may also have claudication from inadequate lower‐extremity perfusion with exercise. Alterations in renal, adrenal, and baroreceptor function all contribute to the development of this proximal systemic hypertension. This may lead to circle of Willis aneurysms, aortic aneurysm proximal or distal to the coarctation, aortic dissection, and increased coronary atherosclerotic heart disease with associated myocardial infarction [46]. The following diagnoses are the causes of death in patients with unrepaired coarctation: congestive heart failure (26%), bacterial endocarditis (25%), spontaneous rupture of the aorta (21%), and intracranial hemorrhage (13%) [47]. The frequency of intracranial aneurysms among adult patients with coarctation (mean age 42 years) is 10%, compared to 2% in the general population [48]. The survival curve of patients with an unoperated coarctation of the aorta is shown in Figure 13.6 [49]. In a review of 200 autopsies in patients with coarctation of the aorta, Abbott found that the average age at death was 33.5 years [50]. Reifenstein and associates in a similar study of 104 autopsies quoted a figure of 35.0 years [47]. In these patients pregnancy increases the risk of associated complications. There is essentially no medical therapy for coarctation and these patients should be referred at the time of diagnosis for surgical or transcatheter intervention. The newborn infant with critical coarctation and arterial duct closure will present in shock. On physical examination the child will be tachypneic and tachycardic, and will appear pale. Lower‐extremity pulses are absent, and upper‐extremity pulses may be thready. The child may be hypotensive, even in the arms, and the liver will be enlarged. Chest radiograph will demonstrate cardiomegaly and evidence of congestive heart failure. Electrocardiogram shows a left ventricular strain pattern. Two‐dimensional echocardiography with color Doppler interrogation is diagnostic in most instances [51–53]. The echocardiogram will demonstrate lack of pulsatile flow in the descending aorta, the anatomic coarctation site, the size of the transverse arch, and any other associated intracardiac anomalies. In many instances, for newborn infants a comprehensive echocardiogram is all that is required to prepare a patient for surgical or transcatheter intervention after stabilization of organ systems. However, if there are complex associated cardiac anomalies, cardiac catheterization can safely be performed in a stable baby who is being maintained on PGE1 infusion. This will reveal the precise great vessel morphology, significant hemodynamic parameters, and intracardiac anatomy [28]. For the child who does not need a cardiac catheterization for the intracardiac anatomy, but has an arch that is difficult to image, computed tomography (CT) scan is our procedure of choice. Ultrafast scan with three‐dimensional reconstruction reveals the anatomy beautifully and gives the surgeon a very clear “roadmap” (Figure 13.7) [54]. Our current preference is to use CT imaging for essentially all coarctation cases unless every anatomic detail is perfectly seen on the preoperative echocardiogram [55]. Physical examination of an older child (often with no symptoms) reveals upper‐extremity hypertension and absent or greatly diminished femoral pulses. Electrocardiogram demonstrates left ventricular hypertrophy and left ventricular strain. Chest radiograph will often demonstrate “notching” of the ribs if the patient is over 4 years of age. In addition, the classic “3” sign on chest radiograph is caused by dilatation of the left subclavian artery, the narrowing of the coarctation site, and poststenotic dilatation of the descending aorta. The echocardiogram in most instances of simple coarctation in older children, adolescents, and adults will provide the diagnosis. In those patients a preintervention CT is very helpful for surgical or transcatheter planning. This will fully delineate the anatomy. The presence or absence of collaterals is noted to help in predicting the need for left heart bypass. In summary, the diagnosis of aortic coarctation can be accomplished accurately and comprehensively in many instances by using the combined methodologies of two‐dimensional and Doppler echocardiography. CT is very useful for infants and magnetic resonance imaging (MRI) or CT scanning can be used for older children and adults to precisely define the arch anatomy [56]. In all cases a complete two‐dimensional and Doppler echocardiographic examination of intracardiac anatomy is necessary to reach appropriate therapeutic and surgical recommendations. Figure 13.7 Three‐dimensional computed tomographic (CT) reconstruction of a newborn with coarctation of the aorta. By echocardiographic analysis adequate visualization of the transverse arch could not be obtained. Because of the CT angiogram showing complex hypoplasia of the transverse aortic arch and stenosis of the origin of the left carotid and left subclavian artery, repair was electively performed through a sternotomy with modified cerebral perfusion. Source: Reproduced by permission from Kaushal S et al. Ann Thorac Surg. 2009;88:1932–1938. The surgical approach to coarctation in most instances is through a left posterolateral thoracotomy incision entering the thorax through the third or fourth intercostal space. The exception to this is a median sternotomy approach for patients with associated cardiac anomalies that are to be repaired simultaneously or in the patient with a severely hypoplastic transverse aortic arch. The arterial blood pressure is monitored in the right radial artery. Should the right subclavian artery arise anomalously below the coarctation, the temporal artery provides a potential site for monitoring the proximal aortic pressure. One must be very careful with this site, however, as there is a chance of injecting air or debris to the cerebral circulation. In some cases like this we have done the repair with only near‐infrared spectroscopy (NIRS) monitoring of the brain. Using the left thoracotomy approach, we divide the latissimus dorsi muscle, but spare the serratus anterior by retracting it anteriorly. In older children the multiple chest wall collateral vessels should be individually ligated and divided to prevent hemorrhage either during the operation or postoperatively. The lung is retracted anteriorly and the mediastinal pleura overlying the coarctation site is incised. Any large lymphatic channels are either preserved or ligated and divided. The vagus nerve and recurrent laryngeal nerve are carefully identified and preserved by retracting these structures with the mediastinal pleura anteriorly. The descending aorta, left subclavian artery, isthmus of the aorta, patent arterial duct (or ligament), and transverse aortic arch distal to the left carotid artery are mobilized. An anomalous artery originally described by Abbott is an occasionally encountered collateral vessel originating from the posterior wall of the aortic arch or left subclavian artery [57]. This vessel is not found in normal subjects or described in standard anatomy textbooks (Figure 13.8) [58]. If present, it should be ligated and divided to facilitate the repair. In older children there are often large collateral intercostal vessels entering the descending aorta distal to the coarctation. Great care should be taken when dissecting these vessels, as they are very thin walled and if injured can cause torrential bleeding. Figure 13.8 Abbott’s artery. The drawing outlines the area on the posterior wall of the aortic arch or subclavian artery from which a blood vessel, which Gross chose to call Abbott’s artery, may take its origin. The black circles show possible other sites of origin of this artery. Source: Adapted from Schuster SR, Gross RE. J Thorac Cardiovasc Surg. 1962;43:54–70 and reproduced with permission from Backer CL, Mavroudis C, in Pediatric Cardiac Surgery, 3rd ed. Philadelphia, PA: Mosby, 2003, pp. 251–272. It is very important that the proximal aortic pressure be allowed to stay quite high (100–120 mmHg for infants, 160–200 mmHg for older children and adults) during the time of the aortic cross‐clamp to provide adequate mean aortic arterial blood pressure distal to the clamp to help prevent the complication of paraplegia. Sodium nitroprusside should never be used during the time of cross‐clamping for coarctation repair. The use of nipride while the aorta is clamped has actually been shown to increase the incidence of paraplegia postoperatively [59]. A distal aortic pressure monitoring line should be placed in older children in the femoral artery. In these older children the mean distal aortic pressure should be maintained above 45 mmHg during the period of aortic cross‐clamp [60, 61]. During the first 10 minutes of cross‐clamping the mean distal aortic pressure usually increases by 5 mmHg. Maintaining the distal aortic pressure can be done by the administration of volume expanders, use of inotropes such as dopamine or dobutamine, or reduced anesthetic during the time period of the cross‐clamp. Other useful maneuvers are to readjust the proximal clamp (if anatomically feasible) to allow flow in the left subclavian artery or to allow more intercostal arteries to remain open. Should the mean pressure drop below 45 mmHg, alternative techniques such as the use of partial left heart cardiopulmonary bypass with left atrial and descending aortic cannulation should be used [61–63]. We are very proactive in using left heart bypass should there be any question regarding the distal perfusion pressure during the coarctation repair. Hypoperfusion of the spinal cord can lead to the dreaded complication of paraplegia, which will be discussed in detail later in this chapter. The various techniques of repair are now reviewed separately (Table 13.1) [5–9, 64]. Table 13.1 Major surgical milestones in coarctation surgery. Crafoord and Nylin [5] reported the first successful resection of coarctation of the aorta with end‐to‐end anastomosis. Their two patients were a 12‐year‐old boy and a 27‐year‐old man operated on in October 1944. Kirklin and associates [65] described the successful surgical treatment of coarctation of the aorta in an infant when they operated on a 10‐week‐old child performing successful coarctation resection with end‐to‐end anastomosis in 1951. The technique of resection and end‐to‐end anastomosis is shown in Figure 13.9. The obviously narrowed coarctation segment is excised with a direct end‐to‐end circumferential anastomosis of the aorta. Early repairs utilized silk suture in a continuous fashion posteriorly and interrupted everting horizontal mattress sutures anteriorly. The mortality and recoarctation rates using resection and end‐to‐end anastomosis in several series [13, 66–72] are shown in Table 13.2. Although the mortality rate was very acceptable in large series [73], several institutions reported a relatively high recoarctation rate (20–86%), particularly in the age group <1 year [13, 66, 69, 71] .This high rate of stenosis in retrospect is attributed to (i) the use of silk sutures instead of the currently available fine monofilament suture [58]; (ii) inadequate resection of all ductal tissue, which may extend into areas of normal‐appearing aorta [69]; (iii) lack of growth at a circumferential suture line [74]; and (iv) lack of growth of a hypoplastic transverse arch. More recent series [70, 72] tend to indicate that with modern sutures and microvascular techniques, the recoarctation rate is reduced. However, this technique does not address the issue of a hypoplastic transverse arch, which is present in many infants. This technique is not easily applicable to older children, in whom the location of the arch and descending aorta is more “fixed” than in infants and is difficult to mobilize for a safe tension‐free anastomosis. Simple resection with end‐to‐end anastomosis has been essentially abandoned at most centers because of new, superior techniques that decrease the incidence of recoarctation. Figure 13.9 Resection with end‐to‐end anastomosis. (A) Exposure through a left thoracotomy. The patent arterial duct (PDA) has been ligated and divided. Dotted lines show area to be resected. (B) Clamps have been applied and the coarctation segment is being resected. (C) Anastomosis has been constructed with running suture for the back wall and interrupted suture anteriorly. Ao, aorta; LSA, left subclavian artery; PA, pulmonary artery. Source: Reproduced with permission from Backer CL, Mavroudis C, in Pediatric Cardiac Surgery, 3rd ed. Philadelphia, PA: Mosby, 2003, pp. 251–272. Table 13.2 Results of resection with end‐to‐end anastomosis. * Kaplan‐Meier estimate at 30 years; †Congenital Heart Surgeons’ Society. Vossschulte [7] in 1961 described an “isthmusplastic” procedure that developed into the prosthetic patch aortoplasty. For many years this was the procedure of choice for older children (1–16 years of age). However, the potential for aneurysm formation has led surgeons to now use this technique only rarely [75–77]. As discussed earlier under general considerations, this operation is performed through a left thoracotomy and fourth intercostal space incision. After vessel dissection and arterial duct ligation, the aorta is occluded proximal and distal to the coarctation with vascular clamps. The aorta is then incised longitudinally through the site of the coarctation, with the incision being extended well beyond the level of the coarctation both distally and proximally. Proximally this means that the patch often extends up onto the left subclavian artery. If the isthmus is hypoplastic with stenosis between the left subclavian and left carotid artery, the patch may be extended up into this area by placing the proximal clamp proximal to the left carotid artery. In the initial descriptions of this procedure, the posterior coarctation membrane or fibrous shelf was excised. This maneuver, however, can cause disruption of the intima and predispose to aortic aneurysm formation, and is no longer recommended [78]. A circular prosthetic patch (slightly elliptical) made of polytetrafluoroethylene (PTFE) is sutured in place longitudinally along the aortotomy edge. An effort is made to use the largest patch feasible and place the widest portion of the patch at the level of the aortic constriction (see Figure 13.10). The pleura should be closed as completely as possible over the patch. The prosthetic patch technique offers several advantages over simple resection with end‐to‐end anastomosis: (i) the collateral vessels are all preserved and do not require ligation and division; (ii) the technique allows simultaneous enlargement of isthmic hypoplasia if necessary; (iii) the anastomosis is tension free; and (iv) the posterior aortic wall and even a hypoplastic aortic arch will grow after prosthetic patch repair [79]. The primary worrisome late complication of this technique is aneurysm formation of the posterior aortic wall opposite the patch [75–77]. This may be explained by several different factors. Most reported aneurysm formation occurred after resection of the coarctation membrane with violation of the intimal layer [80, 81]. The patch causes altered hemodynamics arising from the different tensile strengths of the prosthetic patch and the posterior aortic wall, the pulsatile waveform being completely directed to the posterior aortic wall by the inflexible anterior patch [82]. Resection of the coarctation ridge (which is no longer performed) significantly predisposes to this complication. Another theory to explain aneurysm formation is a congenital abnormality of the aortic wall at the coarctation site [83]. Mortality, recoarctation rates, and incidence of aneurysm formation in several series [79–82, 84–87] of patch aortoplasty are shown in Table 13.3. In a collected series of 815 patients, 9% had recoarctation and 4% had aneurysm formation. The issue of aneurysm formation is addressed in greater detail in the section on postoperative complications. For many years the patch aortoplasty was our operation of choice for children older than 1 year and less than 16 years of age. The potential for late aneurysm formation, however, has now led us to use this procedure only in rare cases. In our experience the younger children (<5 years of age) are frequently candidates for a resection with an extended end‐to‐end anastomosis (to be discussed later in the chapter). The older children and certainly those over 10 years of age are now in our opinion better served by an interposition graft with essentially no risk for aneurysm formation or disruption of the anastomosis because of tension. In addition, patients over 35 kg with milder forms of coarctation may be candidates for a transcatheter intervention. We last used a patch aortoplasty for a primary coarctation repair in 2002. We reported our results with this procedure in 1995 [87]. Between 1979 and 1993, 125 infants and children underwent PTFE patch aortoplasty. The posterior coarctation ridge was not excised in any patient. There were 111 primary repairs and 14 reoperations. The mean age at the time of surgery was 5.1 years. There were no cases of intraoperative mortality or postoperative paraplegia. There were four deaths (3% mortality) at 10–40 days postoperatively, all neonates having additional intracardiac procedures for complex lesions. We have had only one patient develop an aneurysm and this was a false aneurysm detected four months after the surgery. One of the lessons that we did learn from this series was that infants who have this approach at less than 1 month of age had a high incidence of residual or recurrent coarctation. That experience has been confirmed by others [81, 88]. We currently believe that the patch aortoplasty should only be used in the rare patient who is too small for an interposition graft, whose anatomy precludes resection with extended end‐to‐end anastomosis, and for patients with a recoarctation. All patients having patch aortoplasty should be carefully followed for aneurysm formation. Figure 13.10 Patch aortoplasty. (A) Exposure of the coarctation through a left thoracotomy. Note juxtaductal coarctation and enlarged intercostal collateral arteries. (B) An elliptical polytetrafluoroethylene (PTFE) patch is fashioned prior to clamp placement. (C) Clamps have been applied and the aorta opened laterally opposite the site of the ligament. Note that intercostal arteries are controlled with small Rumel tourniquets. The coarctation ridge is not excised. (D) The patch is sutured in place in such a manner that the PTFE creates a “roof” over the coarctation ridge. Ao, aorta; LSA, left subclavian artery; PA, pulmonary artery. Source: Reproduced with permission from Backer CL, Mavroudis C, in Pediatric Cardiac Surgery, 3rd ed. Philadelphia, PA: Mosby, 2003, pp. 251–272. Table 13.3 Results of patch aortoplasty. NS, not specified; PTFE, polytetrafluoroethylene. The use of a prosthetic interposition graft was first described by Robert Gross [64] in 1951 when he used an aortic homograft as a replacement for a coarctation in a child with a long narrowed coarctation segment. In 1960, Morris, Cooley, DeBakey, and Crawford [89] described the use of a Dacron prosthetic interposition graft in 3% of 171 patients undergoing coarctation repair. Currently we recommend prosthetic interposition grafts (Figure 13.11) for patients over 10 years of age, patients with an associated aneurysm, patients with complex long‐segment coarctation, and selected patients with recurrent coarctation. It is also a useful technique if during a planned resection and end‐to‐end anastomosis it appears that the anastomosis will be under tension or the aorta requires further resection because of a thinned aortic wall secondary to poststenotic dilatation. Aris and colleagues [90] reported successful use of this technique in eight patients over 50 years of age, using 16 or 18 mm Dacron tube grafts. We have used GelweaveTM (Vascutek‐Terumo, Renfrewshire, Scotland, UK) grafts for these patients to minimize bleeding, especially if partial cardiopulmonary bypass is used (Figure 13.12). The obvious disadvantage of the interposition graft is the developmental size discrepancy in the growing child, making the operation more applicable for older patients. Another consideration is the longer aortic cross‐clamp time taken to perform two circular anastomoses. This is now our procedure of choice for patients over 10 years of age where an adult‐sized graft can be inserted. We have used this technique in 50 patients in the past 30 years; 19 patients were less than 10 years of age. The subclavian flap aortoplasty technique was introduced by Waldhausen and Nahrwold [8] in 1966. Successful coarctation repair was reported in three patients aged 4 months, 6 months, and 3 years (see Figure 13.13). The operation is performed through the left fourth intercostal space, as described earlier under general considerations. The ligament or arterial duct is ligated. The aorta is clamped proximal to the left subclavian artery as well as distal to the coarctation. The left subclavian artery is ligated distally, opened along its lateral margin, and then divided near the ligature. The incision is extended through the isthmus across the coarctation site into the area of poststenotic dilatation. The subclavian artery is folded down onto the incision in the aorta and then the subclavian “flap” is sutured in place with continuous fine polypropylene suture. The clamps are released and the appearance is of the subclavian patch creating a “roof” over the area of the previous coarctation. The issue of ligation of the vertebral artery is decided on a case‐by‐case basis. Leaving it intact provides collateral circulation to the arm, but may possibly cause subclavian steal syndrome as the child grows. If possible, the internal mammary artery and the thyrocervical trunk are left intact to provide collateral circulation to the left arm. Occasionally more length is required to span the coarctation site and sacrifice of these vessels is required. Failure to extend the incision far enough downstream across the coarctation and onto the area of poststenotic dilatation may contribute to restenosis at a later date. Several variations of this technique have been described for complex coarctations. In 1983, Hart and Waldhausen [91] described the reversed subclavian flap technique for repair of a coarctation proximal to the left subclavian artery. Meier and colleagues [11] also described a technique for subclavian reimplantation in 1986 to preserve the arterial blood flow to the left arm. Dietl and associates [92] used a combined technique of coarctation resection and subclavian flap aortoplasty. Allen and coworkers [93] described a modification of the subclavian flap, adding a side‐to‐side transverse aortic anastomosis at the level of the coarctation. Kanter [94] has also described using a reverse subclavian flap for repair of a hypoplastic transverse arch.
CHAPTER 13
Coarctation of the Aorta
Embryology and Anatomy
Embryology
Anatomy
Natural History and Pathophysiology
Diagnosis
Surgical Techniques
General Considerations
Surgical Procedure
Author
Year
Country
Resection with end‐to‐end
anastomosis
Crafoord [5]
1944
Sweden
Prosthetic interposition graft
Gross [64]
1951
USA
Prosthetic patch augmentation
Vossschulte [7]
1957
Germany
Subclavian flap aortoplasty
Waldhausen and Nahrwold [8]
1966
USA
Resection with extended end‐to‐
end anastomosis
Amato [9]
1986
USA
Resection and End‐to‐End Anastomosis
Author
Age
Year
Patients
Mortality
Recoarctation
Williams [66]
<1 yr
1980
176
66 (38%)
39 (33%)
Cobanoglu [67]
<3 mo
1985
55
16 (29%)
3 (8%)
Körfer [68]
<4 mo
1985
55
2 (4%)
3 (6%)
Ziemer [69]
<1 mo
1986
24
8 (33%)
4 (25%)
Brouwer [70]
<2 yr
1991
32
2 (6%)
4 (13%)
Kappetein [71]
<3 yr
1994
48
5 (10%)
41 (86%)*
van Heurn [13]
<3 mo
1994
42
5 (10%)
11 (30%)
Quaegebeur [72], †
<1 mo
1994
139
20 (14%)
6 (4%)
Totals
571
124 (21%)
111 (19%)
Prosthetic Patch Aortoplasty
Operative
Author
Age
Year
Patients
Mortality
Recoarctation
Aneurysm
Patch
Yee [84]
<l yr
1984
100
0
10 (12%)
0
PTFE
Clarkson [82]
>15 yr
1985
38
NS
6 (16%)
5 (13%)
Dacron
Hehrlein [80]
2 d–64 yr
1986
317
16 (5%)
4 (1.3%)
18 (6%)
Dacron
Del Nido [85]
3 d–32 yr
1986
63
1 (2%)
8 (13%)
3 (5%)
Dacron
Ungerleider [86]
NS
1991
54
0
2 (5%)
0
PTFE
Backer [87]
5.1 yr (mean)
1994
125
4 (3%)
10 (8%)
0
PTFE
Walhout [81]
1.8 yr (mean)
2003
118
4 (3%)
30 (25%)
8 (7%)
PTFE
Totals
815
25 (3%)
70 (9%)
34 (4%)
Prosthetic Interposition Graft
Subclavian Flap Aortoplasty
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