Published online before print March 28, 2008, 10.1148/radiol.2473061909
(Radiology 2008;247:617-631.)
© RSNA, 2008
Repair of Congenital Heart Disease: A Primer–Part 11
Ana Maria Gaca, MD,
James J. Jaggers, MD,
L. Todd Dudley, MD, and
George S. Bisset, III, MD
1 From the Division of Pediatric Radiology, Department of Radiology (A.M.G., L.T.D., G.S.B.) and Division of Cardiothoracic Surgery, Department of Surgery (J.J.J.), Duke University Health Systems, 1905 McGovern-Davison Children's Health Center, Box 3808 Duke University Medical Center, Durham, NC 27710. Received November 9, 2006; revision requested January 8, 2007; revision received February 13; accepted March 19; final version accepted July 3.
Address correspondence to A.M.G. (e-mail: ana.gaca{at}duke.edu).
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ABSTRACT
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Advances in the surgical management of congenital heart disease have led to enhanced patient survival and quality of life. Improvements in technology in computed tomography and magnetic resonance imaging have resulted in increasing use of cross-sectional imaging in these patients. Perioperative care in these patients requires that radiologists have an understanding of the surgical treatment and the resultant postoperative anatomy. Because many of these patients with treated congenital heart disease are being followed into the 4th and 5th decades of life, this is information that will fall within the domain of the radiologist who deals with adults. This review, which is presented in two parts, covers the major surgical procedures used for the treatment of congenital heart disease, and will be presented in two parts. In part 1, median sternotomy and its complications, palliative procedures, and complex repairs are discussed.
© RSNA, 2008
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INTRODUCTION
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In the past, radiology training emphasized the diagnosis of congenital heart disease based on findings from chest radiography. With advances in prenatal ultrasonography (US) and with the care of these complex patients dependent on echocardiography and cardiac angiography, the plain radiography diagnosis of congenital heart disease has become less essential. However, improvements in multidetector computed tomography (CT) and magnetic resonance (MR) technology have resulted in more imaging of these patients, and the responsibility for this imaging lies in the purview of radiologists. Multidetector CT, CT angiography, and MR imaging have several potential benefits over cardiac angiography: They may result in a shorter examination time, less radiation exposure (if appropriate pediatric protocols are used), and less contrast agent administration. The very short examination times of CT angiography may even obviate sedation. CT angiography and MR imaging may be helpful for presurgical planning, delineation of anatomy that may not be clear with echocardiography, and evaluation of surgical complications.
To be of assistance to the cardiologists and cardiothoracic surgeons caring for patients with congenital heart disease, radiologists must understand the basic anatomy and physiology of these patients before and after surgical repair (Fig 1). As surgical techniques and patient survival continue to improve, patients with repaired congenital heart disease are being followed up into their 4th and 5th decades of life. Therefore, an understanding of congenital heart disease and how these defects are repaired is essential to all radiologists interpreting cross-sectional images of the thorax.
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Figure 1: Bedside chest radiograph of 4-month-old infant after partial repair of hypoplastic left heart syndrome. Image was obtained to check peripherally inserted central catheter (PICC) placement. PICC line is shown terminating in middle portion of right lung. Without an understanding of the stages of the Norwood procedure, the PICC line position implies vascular perforation. However, with knowledge that the patient has undergone bidirectional Glenn (BDG) procedure and with understanding of resultant anatomy, this radiograph merely shows a central catheter that has entered the right pulmonary artery (PA) and been placed too distally.
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What follows is a review of surgical repair of common congenital heart lesions, including the indications, surgical approaches, resultant anatomy, and complications (Table). This will by no means be exhaustive but will rather be an overview that may serve as the starting point for understanding these complex patients with congenital heart disease.
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MEDIAN STERNOTOMY AND COMPLICATIONS
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A median sternotomy is the approach used for the majority of corrective congenital cardiac surgical procedures. In children who have relatively pliable bones and ligaments, the median sternotomy is associated with little postoperative pain or later deformity. Although this approach requires an incision along the length of the sternum, there is no cutting or stretching of muscles, with the majority of the motion occurring at the costovertebral junctions (1). In adults, sternal closure is typically achieved with nonabsorbable sutures, including stainless steel wire. Because of potential problems with bone growth and healing in the pediatric population, radiolucent synthetic absorbable suture material is now most commonly used (2,3).
The development of mediastinitis occurs in approximately 1% of pediatric patients undergoing cardiac surgery and generally manifests in the 5–10 days after surgery (4). Risk factors for pediatric patients include younger age and longer duration of surgery. Treatment generally consists of surgical drainage or débridement along with antibiotic therapy (4,5). Conventional radiographs are of limited value in the diagnosis of mediastinitis in the early postoperative period, since widening of the mediastinum and retrosternal pockets of air and fluid are also normal postoperative findings. Chest CT or MR images can demonstrate focal fluid and air collections and mediastinal hematoma as normal postoperative findings in asymptomatic patients up to 21 days following surgery. These findings, in addition to obliteration of mediastinal fat planes and sternal separation, are more concerning for infection when seen more than 2 weeks after surgery in a symptomatic patient. A normal CT study, however, may be used to exclude mediastinitis (6–8).
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PALLIATIVE PROCEDURES
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Classic and Modified BT Shunts
The original BT shunt was designed as a palliative procedure to increase pulmonary blood flow for the relief of cyanosis. Described in May 1945, the BT shunt was developed by Alfred Blalock, a pioneer in general and cardiothoracic surgery, with support from pediatric cardiologist Helen B. Taussig and surgical technician Vivien Thomas (9). Performed through a left posterolateral thoracotomy, the original (classic) BT shunt involved ligation and division of the left subclavian artery, with anastomosis of the proximal subclavian artery to the PA. This resulted in a reliable source of pulmonary blood blow that usually increased over time as the child grew (1). Disadvantages of the classic BT shunt included potential distortion and kinking of the PA in patients with a small subclavian artery and possible abnormal growth and strength of the arm ipsilateral to the shunt (steal phenomenon) (10). The classic BT shunt is rarely used in the current era of pediatric cardiac surgery.
The more recent modified BT shunt involves interposing a prosthetic graft of polytetrafluoroethylene between the subclavian artery and ipsilateral right or left PA (Fig 2) (10,11). Benefits of the modified BT shunt include technical ease of the procedure (which can be performed on either side of the aortic arch), wide anastomoses proximally and distally, and preserved blood flow to the ipsilateral arm (12,13). The modified BT shunt is currently used for palliation prior to complete repair of a lesion, as an adjunct to the repair of single-ventricle palliations, and in patients with inadequate pulmonary blood flow who are otherwise not amenable to primary complete repair.
Thrombosis of a modified BT shunt is not uncommon and may be life threatening. Although usually a late complication (occurring months to years after shunt creation), thrombosis can occur in the early postoperative period as well. Diagnosis can often be made with the aid of echocardiography but can also be made with CT angiography and MR imaging. While subtotal occlusion or stenosis of a BT shunt is typically treated with shunt revision, treatment with balloon angioplasty and stent placement has been described (14).
A well-recognized, but also uncommon, complication of the modified BT shunt is formation of a seroma adjacent to the shunt. This is caused by seepage of fluid across the polytetrafluoroethylene graft. If large enough, the seroma can cause symptoms of airway compression or pericardial tamponade (15). The presence of a seroma is suggested by a mediastinal mass seen on chest radiographs, with the differential diagnosis including mediastinal hematoma. The diagnosis of a seroma, although usually made with the aid of echocardiography, can be made with the CT demonstration of a low-attenuation cystic mass in the mediastinum (16). US-guided percutaneous drainage of these seromas has been described in symptomatic patients, eliminating the need for emergent surgical revision (17).
Waterston and Potts Shunts
Although these shunts are not currently used by pediatric cardiothoracic surgeons, adult patients with treated congenital heart disease who have undergone these procedures will occasionally be encountered. The Waterston shunt is an anastomosis between the ascending aorta and the right PA (18). The Potts shunt is an anastomosis between the descending aorta and the left PA (19). Disadvantages of these shunts include potentially excessive pulmonary blood flow and distortion of the PAs with patient growth (1).
PA Banding
Introduced in 1951 by William H. Muller, Jr, and J. Francis Dammann, Jr, of the University of California, Los Angeles, the PA band was initially used as a palliative procedure to decrease pulmonary blood flow in a 3-month-old infant with a large VSD and excessive pulmonary blood flow from a left-to-right shunt. Through a left lateral thoracotomy, a waist was created in the dilated main PA by resecting a segment of the artery, and a band of umbilical tape was sutured around the narrowed PA to keep the artery from expanding (20). Currently, PA banding is usually performed by encircling the main PA with a ring of prosthetic material via either a median sternotomy or a left thoracotomy, without resection of a segment of the arterial wall. This effectively restricts pulmonary blood flow, increases systemic perfusion and protects the pulmonary vasculature from progressive changes of prolonged pulmonary hypertension until more definitive repair or palliation of an abnormality can be undertaken. A PA band may also be necessary in any heart defect in which excessive pulmonary blood flow needs to be prevented and in which a definitive surgical option is not available. These may include single ventricle, multiple VSDs, atrioventricular septal defects, and a double-outlet right or left ventricle (20,21).
PA banding is also used for "training" the left ventricle in neonates with TGA that was not repaired in the neonatal period. In this situation, the main PA arises from the left ventricle, which to this point is pumping against low pulmonary resistance. The wall of the left ventricle will only thicken when exposed to systemic pressures in the first few weeks of life. The ventricle slowly starts to lose its ability to handle this pressure by the 2nd or 3rd week of life. In patients with TGA without a VSD, the left ventricle is not exposed to systemic pressures, and it pumps only against pulmonary resistance. If performed too late in life, an arterial switch such as the Jatene procedure (described later) will suddenly expose an unprepared left ventricle to systemic pressure. Unable to adapt to the sudden change in pressure, the left ventricle will often fail. A remedy is PA banding, which forces the left ventricle to pump against artificially high pulmonary pressures, thus inducing left ventricular wall thickening prior to the arterial switch (22,23).
Complications of PA banding include dilatation of the proximal portion of the PA, with resultant valve insufficiency. If placed too close to the pulmonary valve, the band can cause pulmonary valve injury. If the band migrates distally, blood flow may be compromised through the PAs, particularly the right PA (24–27).
Glenn and BDG Shunts
The original Glenn shunt consists of an end-to-end anastomosis of the right PA (divided from the main PA) to the side of the SVC. The SVC is ligated at its entrance to the right atrium, directing all proximal SVC blood flow to the right PA. The azygos vein is also ligated. This cavopulmonary shunt was first used clinically by William W. L. Glenn in 1958. The shunt was intended to palliate congenital heart defects in which there was hypoplasia or atresia of right-sided structures of the heart—conditions such as tricuspid atresia, Epstein anomaly, and pulmonary atresia with intact ventricular septum. These patients typically have low pulmonary vascular resistance, which allows deoxygenated blood from the SVC to passively perfuse the pulmonary circulation without the assistance of the heart.
A more commonly used systemic venous–to-PA shunt is the bidirectional cavopulmonary shunt, also known as the BDG shunt (28). The BDG shunt consists of an end-to-side anastomosis between the SVC (again divided from the right atrium) and the right PA (Fig 3). Because the right PA is not divided from the main PA in this procedure, the BDG shunt directs flow from the SVC into the right and left PAs. If there are two SVCs that are similar in size, each is anastomosed to its respective ipsilateral PA (28). Currently, the BDG shunt is used as a staging procedure in children with single-ventricle physiology who will ultimately require a Fontan procedure (discussed later). Because adequate flow through the shunt depends on low pulmonary vascular resistance, this procedure is typically performed between 3 and 9 months of life, after pulmonary vascular resistance falls from elevated neonatal levels (29).
A BDG results in one-half of the systemic venous return going directly to the lungs. The other half (deoxygenated IVC flow from the lower body) still returns directly to the heart. This flow, coupled with pulmonary venous return from the lungs, will result in a volume load if performed in a patient with a single ventricle. Even though most patients will have effective long-term palliation with the BDG, one long-term complication is the development of pulmonary arteriovenous fistulas. These malformations, which result in ineffective gas exchange, are thought to be due to the lack of hepatic venous blood perfusing the lungs (30). Humoral factors in the hepatic venous blood seem necessary to prevent formation of these fistulous communications. These fistulas can be diagnosed by using contrast agent–enhanced echocardiography, CT angiography, MR imaging, and conventional angiography. The BDG shunt is usually followed at 2–4 years of age by the complete Fontan procedure, which diverts all systemic venous return to the pulmonary vascular bed directly. This directs hepatic blood flow to the lungs, prevents the development of fistulas, and removes the volume overload on the heart (29).
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COMPLEX REPAIRS
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Fontan Operation: Total Cavopulmonary Connections
Prior to the advent of surgical palliation, most children with tricuspid atresia had a very poor prognosis, with most dying early in life. In 1971, Fontan and Baudet, building on Glenn's advances in the late 1950s, described a corrective procedure that they used on three children. Over the subsequent decades, the Fontan procedure was transformed from a single surgical procedure into a multistage process, with several slightly differing approaches. These approaches share the goal of creating the Fontan circulation—a condition where systemic venous blood enters the pulmonary circulation directly, bypassing the right ventricle. Over the course of this evolutionary process, morbidity and mortality have improved along with the surgical procedures. Furthermore, the number of conditions corrected by using this procedure has increased, now including tricuspid atresia, single-ventricle syndromes (hypoplastic left heart syndrome, hypoplastic right ventricle with pulmonary atresia, and double-inlet ventricle), and heterotaxy syndromes (1,31–34).
The goal of the original surgery for tricuspid atresia was to provide physiologic correction of blood flow, not anatomic correction (35). To accomplish this, Fontan and colleagues initially used a classic Glenn cavopulmonary shunt, in which the distal end of the divided right PA was connected to the SVC and the cavoatrial junction was ligated. In addition, they closed the atrial septal defect and created an extracardiac valved-conduit connection between the right atrium and the left PA, using homograft material to bridge the gap and provide the valves. The overall result was SVC blood directly entering the right pulmonary circulation and IVC blood directly entering the left. Multiple variations followed, all using the right atrium as a conduit for blood flow to the PAs. It was thought that incorporation of the atrium into the Fontan circuit would result in improved pulmonary blood flow with atrial contraction. Ultimately, the atrium enlarged and dilated, losing contractile function and actually impeding pulmonary blood flow.
Currently, the Fontan circulation is accomplished by using a BDG shunt to direct SVC blood to the lungs and a tunnel (lateral tunnel Fontan) or conduit (extracardiac conduit Fontan) to direct blood from the IVC to the lungs. With the lateral tunnel Fontan, a tunnel is created within the right atrium by using prosthetic material. The inferior aspect of the tunnel is anastomosed to the IVC, and the superior aspect is anastomosed to the PAs. Blood flow from the IVC is thus directed through the right atrial tunnel, exiting the superior aspect into the right PA (Fig 4a). With an extracardiac conduit Fontan, the IVC is separated from the right atrium. A polytetrafluoroethylene tube graft is created from the IVC to the right PA beside the right atrium, rather than within it (Fig 4b). With either procedure, a small opening or fenestration may be created between the venous pathway and the atrium, which acts as a "pop-off" valve to prevent rapid volume overload to the lungs. Both techniques result in smooth laminar flow through the Fontan circuit into the PAs with minimal loss of energy (1,32,35–37).
The hemi-Fontan procedure consists of a BDG shunt with a second connection: the cardiac end of the divided SVC is also attached to the right or main PA. This second anastomosis, however, is either temporarily oversewn or occluded by a polytetrafluoroethylene patch. The hemi-Fontan approach allows easier conversion to the modified Fontan procedure at a later time, which is accomplished by excising the patch or opening the anastomosis and then connecting this anastomosis to the IVC with a conduit or tunnel (1,36,38).
Despite the many advances described above, there are several well-documented complications associated with the Fontan procedure. Some of the more common complications include formation of pulmonary arteriovenous malformations, protein-losing enteropathy, elevated systemic or right atrial pressure, thrombosis in the right side of the heart and the Fontan tunnel or conduit, effusions, arrhythmias, progressive exercise intolerance, anastomotic stenosis, and hepatomegaly (31–33,35,39,40). Imaging plays a role in evaluating these complications, as well as the patency of the Fontan circulation (41,42).
Norwood Procedure
The Norwood procedure, described by William Norwood and associates in 1980, consists of a three-stage surgery to create a new functional systemic circuit in patients with hypoplastic left heart syndrome. Since that time, several modifications have been implemented to improve patient morbidity and mortality (43–45).
Prior to the inception of the Norwood procedure, hypoplastic left heart syndrome was nearly always fatal, accounting for about 25% of early cardiac-related deaths (40,45). The primary feature of hypoplastic left heart syndrome is multiple levels of stenosis or hypoplasia of structures on the left side of the heart. Typical anatomy consists of aortic stenosis or atresia and mitral stenosis or atresia. As a result, the ascending aorta and transverse aortic arch are hypoplastic, and there is coarctation of the aorta. The effective result is that the systemic circulation is dependent on blood flow through the ductus arteriosus (ductal-dependent systemic circulation). The systemic circulation is also continuous with the pulmonary vascular bed; hence, the systemic and pulmonary circulations are in parallel, not in series. This arrangement allows excessive pulmonary blood flow as the pulmonary vascular resistance falls shortly after birth (46). Immediate management requires maintenance of ductal patency with the use of prostaglandins, as well as manipulation of patient ventilation to control pulmonary vascular resistance. Presurgical imaging with MR is usually reserved for surgical planning in difficult cases (40).
The normally high neonatal pulmonary vascular resistance precludes definitive repair of hypoplastic left heart syndrome in the newborn. Thus, a staged surgical approach has been introduced to transition the infant to definitive repair (47). The overall goals of the procedure are (a) to utilize the right ventricle as the systemic arterial pump, (b) to ensure unobstructed pulmonary venous return to the right side of the heart, and (c) to reroute systemic venous return to the lungs, restoring the "in series" circulation (44).
Stage 1: Norwood procedure.—The first stage of the Norwood procedure (Fig 5) is performed within the first few days of life (1). The goals of the first stage of the Norwood procedure are (a) to establish a permanent, unobstructed connection between the right ventricle and the systemic arterial circulation, (b) to ensure unobstructed pulmonary venous return with a satisfactory interatrial communication (atrial septectomy), and (c) to provide stable but limited pulmonary blood flow via a systemic-to-pulmonary shunt (45,48).
The first goal of making the right ventricle the systemic pump is accomplished by reconstructing the aorta by using the main PA. After dividing the main PA at the level of the bifurcation, a side-to-side amalgamation is created between the main PA and the hypoplastic aortic arch (with its coronary arteries). The areas of hypoplasia and coarctation of the transverse aorta are augmented with a prosthetic patch. This creates an unobstructed single arterial trunk that leaves the heart (40,46).
The second goal of the operation is to relieve any obstruction of pulmonary venous return, which must pass through an atrial septal defect to enter the right ventricle. To avoid any obstruction at this level, the atrial septum is excised. In addition, the patent ductus arteriosus is ligated (40).
Because the main PA is used to augment the ascending aorta in the first stage of the Norwood procedure, a new source of pulmonary blood flow in a neonate with elevated PA pressures is necessary. Therefore, a stable source of pulmonary blood flow is provided by either a modified BT shunt or a right ventricle–to-PA (Sano) shunt (Fig 6) (40,44,48). A less commonly used alternative consists of a central shunt from the underside of the reconstructed aorta to the confluence of the PAs (48).
The end result of the first stage of the Norwood procedure is that the right ventricle pumps admixed blood to the systemic and coronary arteries via the reconstructed aorta. Blood from the hypoplastic left heart passes to the right side of the heart via the atrial septal defect. Blood is delivered to the PAs through the modified BT shunt (or equivalent approach). The common atria receive systemic blood from the IVC and SVC and pulmonary blood from the pulmonary veins (40).
Stage 2: bidirectional cavopulmonary shunt.—The second stage of the Norwood procedure (Fig 7) is generally performed when pulmonary vascular resistance has decreased to normal levels and the SVC is large enough to provide adequate pulmonary blood flow, typically around 3–6 months of age. The goal is to begin to separate the systemic and pulmonary circulations. This is accomplished by creating a cavopulmonary shunt, either a BDG anastomosis or a hemi-Fontan operation. The modified BT shunt is also eliminated. This results in decreased volume load on the single ventricle (40,48).
Stage 3: modified Fontan procedure.—The third and final stage of the Norwood procedure completes the separation of the pulmonary and systemic circulations and places the circulations back in series (49). Either a lateral tunnel Fontan or an extracardiac conduit Fontan is created to divert flow from the IVC to the PAs (Fig 4). Now all the systemic venous return is separated from the pulmonary venous return, thereby eliminating cyanosis. The SVC empties into the PAs via the BDG shunt created during stage 2, the IVC blood flow passes directly to the PAs through the modified Fontan conduit, and the pulmonary veins remain attached to the surgically created common atria (40,46,48).
Radiographic findings related to complications include pleural effusions, often right sided. Pericardial effusions and ascites are also seen. Increased right atrial pressure may also result in hepatomegaly or SVC syndrome. Other long-term complications may include protein-losing enteropathy and heart failure (34,40).
Dextro-TGA
Dextro-TGA is a defect of embryologic rotation of the conotruncal septum, resulting in ventriculoarterial discordance—the aorta and associated coronary arteries arise from the right ventricle and the PA arises from the left ventricle. This anatomy results in systemic and pulmonary circulations in parallel rather than in series and, hence, profound cyanosis. Most patients with TGA will have a small atrial septal defect, many will have a patent ductus arteriosus, and 25% will have a VSD. Some patients with TGA also have a degree of left ventricular (pulmonary outflow tract) obstruction.
For a neonate with TGA to survive, there must be mixing of the systemic and pulmonary venous returns. If there is no atrial defect or VSD, the neonate will not survive the first few days of life without some early intervention. The first intervention is to create an atrial level defect to allow mixing of systemic and pulmonary venous return. Previously, this type of palliation required a surgical procedure, the Blalock-Hanlon septostomy. Now, this can most often be accomplished with a balloon catheter atrial septostomy or a Rashkind procedure. This will allow a period of stabilization until definitive repair can be undertaken (50–52).
Early attempts at surgical repair of TGA were aimed at physiologic correction, because techniques for anatomic repair were not available. The first attempt at repair was described in 1959 by Åke Senning (53). A second surgeon, William Thornton Mustard, devised a similar technique, which was reported in 1964 (54). Both procedures involve the correction of blood flow at the atrial level. Both involve creation of a conduit within the atria to redirect systemic venous return to the left ventricle and PA and pulmonary venous flow to the right ventricle and aorta. The Mustard and Senning procedures have fallen out of favor, having been replaced by the Jatene arterial switch, which results in an anatomic repair and is described later in this review (55,56). The Mustard and Senning procedures remain important to understand, however, since patients who have undergone these corrections continue to be seen for long-term follow-up.
Patients with transposition can be separated into two groups, those with isolated (or simple) TGA and those with complex TGA (with associated VSD). The VSD associated with a TGA provides a route for admixing of systemic venous and pulmonary venous blood at the level of the ventricles, resulting in less cyanosis. In addition, the left ventricle in these patients is exposed via the VSD to systemic pressures. In patients without a VSD, the left ventricle is unprepared for systemic pressures if repair is undertaken too late. These patients undergo PA banding, as described earlier, to train the left ventricle (22).
Senning and Mustard procedures.—Both the Senning procedure and the Mustard procedure involve the physiologic repair of TGA with the creation of an intraatrial baffle to redirect flow entering the heart to the embryologic left ventricle and, subsequently, to the PA. In the Senning procedure, a flap is made from the atrial septum. This flap is sewn to the posterior wall of the left atrium, isolating the pulmonary veins behind it. The walls of the right atrium are then wrapped around one another to create a systemic venous atrium and a pulmonary venous atrium. Blood from the vena cavae is directed through the systemic venous atrium into the mitral valve and left ventricle and then out the PAs to the lungs. Pulmonary venous blood returns to the pulmonary venous atrium and is directed through the tricuspid valve into the right ventricle and out the aorta (Fig 8) (57,58).
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Figure 8a: (a) Illustration of Senning procedure, as performed by means of right atrial incision. (b) Cutaway illustration shows Senning procedure. Ao = aorta, LV = left ventricle, PVA = pulmonary venous atrium, RV = right ventricle, SVA = systemic venous atrium.
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Figure 8b: (a) Illustration of Senning procedure, as performed by means of right atrial incision. (b) Cutaway illustration shows Senning procedure. Ao = aorta, LV = left ventricle, PVA = pulmonary venous atrium, RV = right ventricle, SVA = systemic venous atrium.
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In the Mustard procedure, the entire atrial septum is removed. By using a portion of pericardium, a baffle is created to direct systemic venous blood from the right atrium through the mitral valve into the left ventricle and out the PA. At the same time, pulmonary venous blood is channeled through the tricuspid valve to the morphologic right ventricle and then out to the systemic circulation. This baffle does not form a tube or tunnel but instead is used as a divider in the now common atrium to direct flow (Fig 9) (54).
Complications of the Mustard and Senning procedures are typically related to the intraatrial baffle (32). Immediate complications include baffle obstruction or leak and vena cava obstruction (59). Late surgical complications include pulmonary and/or systemic venous pathway stenosis. Obstruction of the pulmonary venous pathway can manifest as pulmonary venous hypertension and pulmonary edema. Less commonly, the left pulmonary venous channel can become obstructed, causing left-sided edema. With chronic stenosis of SVC drainage, patients are often relatively asymptomatic, as they may develop retrograde flow into the azygos vein with SVC syndrome. If reversal is substantial, there may be flow into dilated paravertebral veins with retrograde drainage into the IVC. These dilated paravertebral veins can appear as paravertebral masses on chest radiographs. Patients may also have persistent pleural effusions or chylothorax. Elevated SVC pressures can also manifest as communicating hydrocephalus. Chronic stenosis of the IVC is not well tolerated owing to subsequent hepatic congestion and ascites (26,50). This stenosis can often be treated with transcatheter-delivered stents. Baffle leaks can sometimes be treated with placement of covered stents. Atrial and ventricular arrhythmias can also occur. Long-term neurologic complications include stroke and seizures, often related to thromboembolic events. Finally, right (systemic) ventricular failure with secondary tricuspid valve insufficiency is common (59). These patients can develop progressive cardiomegaly, seen on chest radiographs, and may ultimately require end-stage heart failure management, including cardiac transplant (26).
Arterial switch: Jatene procedure.—Successful anatomic repair of TGA was accomplished by Adib Jatene in Sao Paulo, Brazil, in 1976 (32). This procedure accomplished anatomic switching of the great vessels with the associated coronary arteries. Initially, this procedure was intended for patients with TGA and an associated VSD and with normal pulmonary resistance. There was a benefit to treating these infants medically for 3–6 months at a time when operating during the neonatal period was fraught with hazard. A major stumbling block to initial attempts at performing an arterial switch was not the switching of the aorta and main PA but rather the relocation of the coronary arteries while performing the arterial switch.
In the Jatene arterial switch (Fig 10), the coronary arteries are excised from the aorta with a small cuff of the aortic wall attached. Next, the ascending aorta and the PA are transected and switched. Before the vessels are anastomosed, the PA is relocated anterior to the aorta. (This relocation of the neo-PA, the Lecompte maneuver, was added in 1981 and involves threading the ascending aorta posterior to the bifurcation of the PA, maximizing the length of the neoaorta; this reduces the risk of coronary artery kinking or compression.) Small holes are created in the neoaorta near its origin from the left ventricle, and the coronary arteries are implanted. Because of complications related to pulmonary stenosis with direct anastomosis of the PA, the PA is now generally reconstructed by using pericardial patch augmentation. In patients with TGA and VSD, the VSD is corrected as well (60,61). Patients with anomalous coronary arteries are not candidates for the Jatene procedure.
With improvements in critical care and technical skill, the Jatene arterial switch is now optimally performed in neonates within the 1st week or 2 of life. In patients with isolated TGA, it was initially believed that the left ventricle, having only been exposed to the low pressure pulmonary circulation, would be unable to sustain high systemic pressures immediately after the switch (62–64). Currently, the Jatene arterial switch can be performed in neonates without a VSD in the first 3 weeks of life, before the left ventricle becomes deconditioned to pump against the low-pressure pulmonary circulation. In this situation, it may take some time for the left ventricle to recover good function (recondition). This strategy may be successful until around 2 months of life. However, if the child presents later than this, it may be necessary to train or recondition the left ventricle by means of PA banding. This effectively increases the afterload on the left ventricle, preparing it to meet the challenge of eventually becoming the systemic ventricle (50–52).
There are several benefits of the arterial switch over the Mustard and Senning operations. These include a much lower incidence of arrhythmias. Restoration of normal ventriculoarterial relationships, which include the left ventricle becoming the systemic ventricle, result in preservation of ventricular and atrioventricular valve function (51). The most common complication of the arterial switch is supravalvular pulmonary stenosis (at the anastomotic site), which is usually seen within the 1st year after surgery but is only severe enough to necessitate balloon angioplasty or open surgical repair with a patch in a small percentage of those patients. LVOT obstruction is rare (51,65). A common finding after a Jatene procedure is dilatation of the neoaortic root (often 3 standard deviations beyond the mean) (66). While this has been seen in 50% of patients 10 years after surgery, the importance of this finding is unknown. Despite this dilatation, hemodynamically significant neoaortic valve regurgitation is uncommon (65–67). Dilatation of the aorta is well demonstrated on MR images and can be visible on radiographs (68). Finally, it has been reported that there is a substantial risk of early and late coronary artery occlusion or stenosis in patients undergoing an arterial switch procedure. Most of these patients are asymptomatic, at least initially (69–72).
Rastelli procedure.—Some patients with TGA and VSD have some degree of LVOT obstruction, often with a small and abnormal pulmonary valve. Prior to repair, this may result in pulmonary stenosis or limitation of pulmonary blood flow. In these patients, the Jatene arterial switch procedure is not suitable. Initially, the repair in these patients involved an atrial switch, closure of the VSD, and repair of the LVOT obstruction—either with resection of the stenosis or placement of a conduit from the left ventricle to the PAs (73). While this would redirect blood flow for physiologic repair of TGA, the right ventricle would continue pumping against systemic pressures, and there were considerable problems with recurrent LVOT obstruction (73).
In 1969, Giancarlo Rastelli and colleagues introduced a new procedure for surgical repair in these complicated patients (74). Recognizing the difficulty of accessing and repairing LVOT obstruction, Rastelli and colleagues designed a procedure that would bypass this obstruction altogether (75,76). The first step of the classic Rastelli procedure involves closing off the original LVOT by dividing the PA just above the valve and closing the cardiac end. An intraventricular tunnel is then created with a patch that redirects blood from the left ventricle through the VSD and into the ascending aorta; the VSD is enlarged, if necessary, to prevent LVOT. Next, continuity of the right ventricle to the PA is accomplished with an external conduit, typically a pulmonary allograft (Fig 11) (75). This procedure corrects the abnormal blood flow pattern of TGA at the ventricular level and allows the left ventricle to function as the systemic ventricle (73). The Rastelli procedure can also be used for cardiac lesions characterized by two ventricles and an overriding aorta with pulmonary outflow tract obstruction (such as pulmonary atresia with a VSD or double-outlet right ventricle with pulmonary stenosis or atresia).
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Figure 11a: Cutaway illustrations of Rastelli procedure. (a) Preoperative view of heart with transposition, VSD, and LVOT obstruction. (b) Intraoperatively, left ventricular blood flow has been redirected through the VSD to the aorta, and main PA has been transected. (c) Extracardiac valved conduit from right ventricle to PAs has been created.
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Figure 11b: Cutaway illustrations of Rastelli procedure. (a) Preoperative view of heart with transposition, VSD, and LVOT obstruction. (b) Intraoperatively, left ventricular blood flow has been redirected through the VSD to the aorta, and main PA has been transected. (c) Extracardiac valved conduit from right ventricle to PAs has been created.
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Figure 11c: Cutaway illustrations of Rastelli procedure. (a) Preoperative view of heart with transposition, VSD, and LVOT obstruction. (b) Intraoperatively, left ventricular blood flow has been redirected through the VSD to the aorta, and main PA has been transected. (c) Extracardiac valved conduit from right ventricle to PAs has been created.
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While the early surgical mortality of the Rastelli is acceptable at approximately 5%, questions have been raised about long-term results. LVOT and right-sided conduit obstruction can require percutaneous intervention with stent placement or repeat surgery. The authors of this same long-term study (77) also found that nearly 50% of patients who underwent the Rastelli procedure either needed cardiac transplantation or died 20 years after the procedure (77).
Congenitally Corrected Transposition: Double-Switch Procedure
In congenitally corrected TGA, also known as levo-TGA, there is discordance at the atrioventricular and ventriculoarterial levels—a case where two wrongs make a right. Systemic venous blood travels from the vena cavae to the right atrium, enters the morphologic left ventricle, and exits to the lungs via the PA. Pulmonary venous blood returns to the left atrium, enters the morphologic right ventricle, and then enters the systemic circulation via the aorta. While the circulation is physiologically correct, the right ventricle is the systemic ventricle and the tricuspid valve (always concordant with the ventricle) remains the systemic atrioventricular valve. Until the early-to-mid 1990s, conventional repair of congenitally corrected TGA was aimed only at repair of the relevant associated anomalies, including VSD, pulmonary stenosis or atresia, and tricuspid valve abnormalities. Studies, however, have shown a high prevalence of tricuspid valve insufficiency and right ventricular failure, as well as complete heart block, associated with this anomaly. These complications become more prevalent with patient age (78,79). This has led to the performance of the double-switch procedure in patients with congenitally corrected TGA, particularly in those with right ventricular or tricuspid valve dysfunction.
To achieve anatomic correction, the patient undergoes an atrial correction procedure (either the Senning or the Mustard procedure) and a Jatene arterial switch, or an atrial switch and a Rastelli-type repair (this combination is also known as the Ilbawi procedure or the "Senelli" procedure). These procedures are more commonly performed in children of several months to years of age. In the absence of LVOT obstruction, the left ventricle will require training with a PA band (80–84).
Follow-up studies in patients undergoing the double-switch procedure have shown improved right ventricular function and decreased tricuspid regurgitation when right ventricular dysfunction was present preoperatively. This improvement may result simply from removal of the systemic pressure load from the right ventricle (without direct surgical intervention on the tricuspid valve) (81,84). The development of left ventricular dysfunction is a rare complication of the double-switch procedure (85). The complications associated with the double-switch procedure also include all those associated with the individual procedures, which have been described in detail in the previous sections.
DKS Procedure
The majority of patients with a single functioning ventricle are adequately treated with a modified Fontan procedure (with the exception of patients with a hypoplastic left heart, who are treated with the Norwood procedure) (86). However, the presence of systemic outflow obstruction in these patients is one of the most important factors affecting long-term outcome. If recognized early and treated appropriately with a Norwood or DKS procedure to bypass the obstruction, the long-term effect of systemic outflow obstruction can be minimized (1). Described independently in the early-to-mid 1970s by Paul S. Damus, Michael Kaye, and H. C. Stansel, Jr, the DKS procedure was originally intended to treat TGA with VSD. The DKS procedure is now used in patients who all have similar anatomy: a dominant left ventricle giving rise to the PA and a rudimentary right ventricle giving rise to the aorta, as is seen with double-inlet left ventricle, tricuspid atresia with TGA, or TGA with a hypoplastic right heart (26).
In the DKS procedure, the PA is divided near its bifurcation. The proximal PA is anastomosed to the side of the ascending aorta by using a patch, as needed, to ensure a tension-free anastomosis (Fig 12). This PA-to-aorta anastomosis bypasses any systemic outflow obstruction. While the original DKS procedure included an extracardiac conduit from the right ventricle to the distal PA, later modifications have omitted this and instead include a shunt to provide pulmonary blood flow, such as a modified BT shunt (particularly in the neonatal period), a BDG shunt, or an extracardiac Fontan procedure in older patients (87,88). Because pressures in the PA and aorta are higher than that of the right ventricle, the aortic valve stays closed throughout the cardiac cycle; later modifications of the DKS procedure, however, include surgical closure of the aortic valve to prevent development of aortic valve insufficiency (87,89–92). Patch augmentation of the aortic arch may also be performed if the arch is hypoplastic, making this procedure very similar to stage 1 of the Norwood procedure (1).
Early mortality due to the DKS procedure is approximately 20% (88,92). Pulmonary valvular regurgitation, although mild, has also been described in 25% of patients undergoing the DKS procedure (93). Narrowing at the site of the aorta-to-PA anastomosis is a rare complication of the DKS procedure (94). If performed in the neonatal period, patients who undergo modified BT shunt creation in addition to the DKS procedure will, as their pulmonary pressures decrease, require repeat surgery to convert the BT shunt to a BDG or Fontan shunt (88).
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CONCLUSION
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Advances in the surgical management of congenital heart disease have led to improved patient survival and quality of life. Improvements in CT and MR technology have resulted in the increasing use of cross-sectional imaging in these patients. For the perioperative care of these patients, it is essential that radiologists have an understanding of the surgical treatment and the resulting anatomy of these complex patients. Because many of these patients with treated congenital heart disease are being followed up into the 4th and 5th decades of life, this is not information that falls exclusively within the domain of the pediatric radiologist but is vital to all radiologists.
Topics to be addressed in the second part of this review will include the repair of aortic arch anomalies, including coarctation and interruption of the arch; the repair of total anomalous pulmonary venous return; left-to-right shunts; valvular disease; tetralogy of Fallot; truncus arteriosus; and cardiac transplantation.
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ESSENTIALS
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- The modified Blalock-Taussig shunt, from a subclavian artery to a pulmonary artery (PA), is commonly used in the neonatal period as a temporary shunt to augment pulmonary blood flow while PA pressures transition from elevated perinatal levels to normal.
- The bidirectional Glenn shunt, from the superior vena cava to the PA is a permanent shunt to supply pulmonary blood flow after neonatal PA pressures have normalized.
- The goal of the Fontan circulation is systemic venous blood flow to the lungs independent of right heart pulsations.
- The Norwood procedure is a series of staged surgical operations to bring about the Fontan circulation, typically performed in cases of hypoplastic left heart syndrome.
- The Jatene arterial switch procedure is anatomic repair of D-loop transposition of the great arteries, resulting in the left ventricle as the systemic arterial ventricle.
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FOOTNOTES
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Abbreviations: BDG = bidirectional Glenn • BT = Blalock-Taussig • DKS = Damus-Kaye-Stansel • IVC = inferior vena cava • LVOT = left ventricular outflow tract • PA = pulmonary artery • SVC = superior vena cava • TGA = transposition of the great arteries • VSD = ventricular septal defect
Authors stated no financial relationship to disclose.
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TOP
ABSTRACT
INTRODUCTION
