Postoperative Imaging in Cyanotic Congenital Heart Diseases: Part 1, Normal Findings

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1 Normal Postoperative Imaging in Cyanotic Congenital Heart Diseases Cardiac Imaging Pictorial Essay Esther Rodríguez 1 Rafaela Soler 1 Rosa Fernández 1 Inés Raposo 2 Rodríguez E, Soler R, Fernández R, Raposo I Keywords: cardiac surgery, cine imaging, congenital heart disease, cyanosis, heart disease, hemodynamics, MR angiography, MRI, shunts DOI: /AJR Received February 23, 2007; accepted after revision June 19, Department of Radiology, Complejo Hospitalario Universitario Juan Canalejo, Xubias de Arriba 84, La Coruña, Spain. Address correspondence to E. Rodríguez (esther.rodriguez@mundo-r.com). 2 Department of Pediatric Cardiology, Complejo Hospitalario Universitario Juan Canalejo, La Coruña, Spain. CME This article is available for CME credit. See for more information. AJR 2007; 189: X/07/ American Roentgen Ray Society Postoperative Imaging in Cyanotic Congenital Heart Diseases: Part 1, Normal Findings OBJECTIVE. The objective of this article is to illustrate the most common surgical procedures performed in patients with cyanotic congenital heart diseases along with the respective postoperative MRI findings normally seen in clinical practice. CONCLUSION. Radiologists need a solid knowledge of the surgical procedures used to treat patients with cyanotic congenital heart diseases to identify what constitutes normal postoperative findings on MR images and to play an ongoing role in the integral lifelong care of these patients. mprovements in surgical techniques and medical treatment over I the past two decades have increased the life span of patients with cyanotic congenital heart diseases more than ever. Cardiac MRI is an ideal technique for evaluating postsurgical morphology and function in these patients [1]. Contrast-enhanced 3D MR angiography (MRA), in turn, can be used to effectively assess the extracardiac aspects of surgery. An understanding of the surgical procedures used to treat patients with cyanotic congenital heart diseases and of their postoperative appearances on MR images is a basic requirement for radiologists to be able to differentiate normal postoperative findings from complications. This article, which includes sketches of the most common surgical palliation and repair procedures performed in patients with cyanotic congenital heart diseases, aims to contribute to that understanding. Extracardiac Procedures Systemic Arterial to Pulmonary Artery Shunts Systemic arterial to pulmonary artery shunts (i.e., Blalock-Taussig, Potts, Waterston-Cooley, Davidson, and Sano shunts) are palliative surgical procedures performed to increase the delivery of desaturated venous blood to the lungs, thereby alleviating cyanosis and enlarging the pulmonary arteries. Blalock-Taussig shunt The subclavian artery to pulmonary artery shunt or Blalock- Taussig shunt (Fig. 1A) used in the past has been largely replaced by the modified Blalock-Taussig shunt in which a graft connects the subclavian artery to the pulmonary artery [2] (Fig. 1B). The advantages of the modified Blalock-Taussig shunt over the standard Blalock-Taussig shunt include greater growth of the pulmonary tree and less distortion of the pulmonary arteries. MRI is a robust technique for visualizing shunt patency (Fig. 1C) and the increase in size of the pulmonary arteries after the procedure [1]. Potts, Waterston-Cooley, and Davidson shunts A Potts shunt consists of creating a small communication between the posterior wall of the left pulmonary artery and the anterior aspect of the ipsilateral descending thoracic aorta (Fig. 2A). In the Waterston- Cooley shunt, the small communication is created between the posterior wall of the ascending aorta and the anterior wall of the right pulmonary artery (Fig. 2B). Potts and Waterston-Cooley shunts have become obsolete because of the high incidence of pulmonary hypertension and distortion of the pulmonary arteries recorded [2]. In the Davidson shunt, also called a central shunt, a prosthetic graft material is inserted between the ascending aorta and the main pulmonary artery (Fig. 2C). This shunt is usually performed when the pulmonary arteries are hypoplastic. Sano shunts Today, many cardiac surgeons use a Sano shunt in which an extracardiac allograft valved conduit is inserted directly from the right ventricle to the pulmonary artery (Figs. 2D and 2E). This shunt is created to avoid the reduced diastolic blood flow in the coronary circulation associated with the Blalock-Taussig shunt [3]. AJR:189, December

2 Systemic Venous to Pulmonary Artery Shunts Systemic venous to pulmonary artery shunts (i.e., Glenn, Fontan, and Rastelli procedures) provide venous flow to the lung fields for oxygenation without the increase in ventricular workload or volume observed in systemic arterial to pulmonary artery shunts. Glenn shunt The original Glenn shunt, consisting of an anastomosis of the superior vena cava (SVC) and the distal end of the divided right pulmonary artery, provided perfusion of only the right lung. This technique has been largely replaced today. The modified procedure that is in current use is termed the bidirectional Glenn shunt, in which an endto-side anastomosis of the SVC and the right pulmonary artery provides bidirectional flow to the lungs without raising the workload on the heart (Fig. 3). Depending on the diagnosis and timing of the surgery, the Glenn shunt may be only one of several palliative procedures for a cyanotic patient, a step in palliative surgery for a total right heart bypass with the Fontan procedure, which requires an intact, unobstructed pulmonary artery tree [4]. Fontan circulation The aim of the Fontan procedure is to establish circulation in which the systemic venous return enters the pulmonary arteries directly [4]. The original Fontan operation consisted of placing a valved conduit between the right atrium or atrial appendage and the pulmonary artery (Figs. 4A and 4B). There are many procedural variations, including the direct right atrium right ventricle (Björk modification) (Fig. 4C) and total cavopulmonary connections, the latter consisting of either an intraatrial tunnel (Fig. 4D) or an extracardiac conduit (Figs. 4E 4G). A small residual atrial shunt (fenestrated Fontan) may be deliberately constructed to moderate systemic venous pressure in the postoperative period (Fig. 4H). The Fontan circuit has now been extended to palliate most forms of a single functional ventricle. Postoperative ventricular function, the Fontan circulation itself, and the dimensions of the right and left pulmonary arteries expressed as the McGoon ratio that is, the sum of the diameters of the two central pulmonary arteries immediately upstream of where they branch divided by the diameter of the descending aorta measured just above the diaphragm should be carefully monitored by cine MRI and gadolinium-enhanced 3D MRA. Increased risk of death or a dysfunctional Fontan circuit may be expected when this ratio is less than 1.8 [5]. Rastelli procedure In the Rastelli procedure, blood is redirected at the ventricular level with a baffle in the right ventricle to connect the left ventricle to the aorta and a valved conduit from the right ventricle to the pulmonary artery (Fig. 5). Because it was the first operation that incorporated a systemic ventricle to repair dextroposed transposition of the great arteries (D-TGA), it was regarded as an anatomic correction. Actually, however, it is a palliative procedure given that the patient is committed to additional operations because the conduit is likely to need to be replaced several times during the patient s life. Nowadays, the Rastelli operation is relegated to alternative status in cases of D-TGA when the membrane obstructing left ventricular outflow is not resectable during the anatomic correction [6]. Pulmonary Artery Banding Surgical stenosis of the main pulmonary artery, pulmonary artery banding (Fig. 6A), is widely used by cardiac surgeons worldwide in patients with cyanotic congenital heart diseases and excessive pulmonary blood flow to protect the pulmonary vasculature from hypertrophy and irreversible pulmonary hypertension. The current indications for banding include multiple ventricular septal defects (Swiss-cheese interventricular septum), ventricular septal defect with coarctation of the aorta, and D-TGA in patients who are not immediate candidates for switch procedure [7]. In D-TGA, the band is placed to increase work of the left ventricle and cause an increase in muscle mass before corrective surgery. The anatomic position of the pulmonary artery band (Fig. 6B), the mass and function of the right ventricle, and the appearance of the pulmonary vascular tree can be readily monitored using MRI. Intracardiac Procedures Anatomic Repair of Tetralogy of Fallot Reparative surgery for tetralogy of Fallot is usually performed in the first year of life. This procedure consists of patch closure of the ventricular septal defect and widening of the right ventricular outflow (Figs. 7A 7C). The latter is achieved by either removing the obstructing muscle or pulmonary valve and using a patch to enlarge the area as needed or building a conduit from the right ventricle to the main pulmonary artery [8]. MRI is an excellent noninvasive technique to closely monitor biventricular function, to assess the pulmonary vascular tree (Fig. 7D), and to detect early and late postoperative complications. Physiologic Correction of D-TGA In the physiologic correction of transposed great arteries (atrial switch) [9], systemic venous blood from the SVC and inferior vena cava (IVC) is redirected to the left ventricle, and pulmonary venous blood from the pulmonary veins is redirected to the right ventricle (Fig. 8A) using artificial pericardial (Mustard procedure) or atrial (Senning procedure) tissue. Although a physiologic correction circulation is created, normal anatomic relations are not restored, and the right ventricle remains subject to systemic loading, followed by compensatory hypertrophy. This can result in late right ventricle failure. Right and left ventricular function and venous pathway patency can be effectively evaluated with gradient-echo MRI (Figs. 8B and 8C). Anatomic Repair of D-TGA Today, arterial switch is the surgical treatment of choice in neonates with D-TGA [9]. In this procedure, surgical repair involves the repositioning of both the aorta and the pulmonary arteries (Fig. 9A). The arterial switch procedure prevents the development of right ventricle failure because the left ventricle is the systemic and the right, the pulmonary ventricle. The postoperative anatomic relationship between the ascending aorta and the pulmonary artery branches is clearly visible with 3D gadolinium-enhanced MRA (Fig. 9B). Hemodynamic changes in the pulmonary arteries after the arterial switch procedure (Figs. 9C and 9D) can be seen with cine MRI, and velocity mapping can be used to evaluate the hemodynamic significance of such changes [10]. The reversal in muscle thickness and shape of the right ventricle can be viewed with cine MRI. Conclusion This article illustrates many of the complex surgical procedures performed in patients with cyanotic congenital heart diseases. Knowledge of postsurgical anatomy is important to avoid misdiagnosing expected anatomy as complications on MR examinations. References 1. Masui T, Katayama M, Kobayashi S, et al. Gadolinium-enhanced MR angiography in the evaluation of congenital cardiovascular disease pre- and postoperative states in infants and children. J Magn Reson Imaging 2000; 12: Alkhulaifi AM, Lacour-Gayet F, Serraf A, Belli E, Planche C. Systemic pulmonary shunts in neonates: 1354 AJR:189, December 2007

3 Normal Postoperative Imaging in Cyanotic Congenital Heart Diseases early clinical outcome and choice of surgical approach. Ann Thorac Surg 2000; 69: Pizarro C, Malec E, Maher KO, et al. Right ventricle to pulmonary artery conduit improves outcome after stage I Norwood for hypoplastic left heart syndrome. Circulation 2003; 108:[suppl 1]:II155 II Mavrouids C, Backer CL, Deal BJ. Venous shunts and the Fontan circulation in adult congenital heart disease. In: Gatzoulis MA, Webb GD, Daubeney PEF, eds. Diagnosis and management of adult congenital heart disease. Edinburgh, Scotland: Churchill Livingstone, 2003: Fontan F, Fernandez G, Costa F, et al. The size of the pulmonary arteries and the results of the Fontan operation. J Thorac Cardiovasc Surg 1989; 98: Kreutzer C, De Vive J, Oppido G, et al. Twenty-fiveyear experience with Rastelli repair for transposition of the great arteries. J Thorac Cardiovasc Surg 2000; 120: Miura T, Kishimoto H, Kawata H, Hata M, Hoashi T, Nakajima T. Management of univentricular heart with systemic ventricular outflow obstruction by pulmonary artery banding and Damus-Kaye- Stansel operation. Ann Thorac Surg 2004; 77: Gatzoulis MA. Tetralogy of Fallot. In: Gatzoulis MA, Webb GD, Daubeney PEF, eds. Diagnosis and management of adult congenital heart disease. Edinburgh, Scotland: Churchill Livingstone, 2003: Hornung T. Transposition of the great arteries. In: Gatzoulis MA, Webb GD, Daubeney PEF, eds. Diagnosis and management of adult congenital heart disease. Edinburgh, Scotland: Churchill Livingstone, 2003: Gutberlet M, Boeckel T, Hosten N, et al. Arterial switch procedure for D-transposition of the great arteries: quantitative midterm evaluation of hemodynamic changes with cine MR imaging and phaseshift velocity mapping initial experience. Radiology 2000; 214: Fig. 1 Blalock-Taussig shunt. A, Sketch of Blalock-Taussig shunt. Drawing shows classic Blalock-Taussig procedure in which end-to-side anastomosis (gray) is performed between subclavian artery and ipsilateral pulmonary artery, usually on side opposite descending aorta. Although this procedure provides shunt flow appropriate for patient who is size of infant, it requires careful, lengthy dissection and distorts peripheral pulmonary artery. B, Sketch shows modified Blalock-Taussig shunt, in which prosthetic graft material (gray) is inserted between subclavian artery and ipsilateral pulmonary artery. With this modified shunt, which can be performed on either side, subclavian blood supply to arm is preserved. C, Oblique coronal thin-slab reformatted maximum-intensity-projection image obtained with gadolinium-enhanced 3D MR angiography shows patent modified Blalock- Taussig shunt (arrows) from right subclavian artery to pulmonary artery. Procedure was performed for palliative correction of tetralogy of Fallot in 6-year-old boy. AJR:189, December

4 Fig. 2 Aortopulmonary shunt. A, Sketch of Potts shunt. Drawing shows side-to-side anastomosis (gray) between descending aorta and pulmonary artery. B, Sketch of Waterston-Cooley shunt. Drawing shows side-to-side anastomosis (gray) of ascending aorta and pulmonary artery. C, Sketch shows central shunt, in which prosthetic graft material (gray) is inserted between ascending aorta and main pulmonary artery. Amount of shunt flow is controlled by size of graft (usually 4 5 mm in diameter). This procedure prevents distortion of pulmonary arteries and allows symmetric blood flow and growth. D, Sketch of Sano shunt shows from right ventricle to pulmonary bifurcation using prosthetic graft conduit (gray). Important advantage of Sano shunt is that flow occurs only during systole. There is no competition between pulmonary and coronary blood flow during diastole, as is case with Blalock shunt. E, Oblique coronal maximum-intensity-projection image shows Sano shunt from right ventricle (arrow) to pulmonary artery (arrowhead) performed for palliative correction of pulmonary atresia in 4-year-old boy. D E Fig. 3 Modified Glenn shunt. A, Sketch of bidirectional Glenn shunt. Diagram depicts postoperative anatomy of bidirectional Glenn shunt (gray) in which superior vena cava (SVC) is disconnected from right atrium and anastomosed to undivided right pulmonary artery, providing flow for both lung fields. As with classic Glenn shunt, bidirectional cavopulmonary shunt is less likely to engender pulmonary vascular obstructive disease than systemic artery to pulmonary artery shunts and involves only minimal distortion of pulmonary artery architecture. B and C, Postoperative anterior 3D shaded surface display (B) and maximum-intensity-projection (C) images show bidirectional Glenn shunt extending from SVC (arrows) to right pulmonary artery (stars) performed for tricuspid atresia and proximal right pulmonary artery stenosis in 20-year-old man. Bright blue and white show SVC and right pulmonary artery, respectively, in C AJR:189, December 2007

5 Normal Postoperative Imaging in Cyanotic Congenital Heart Diseases D Fig. 4 Fontan procedures. A, Sketch of original Fontan procedure. Diagram shows conduit between right atrium and pulmonary artery (gray), as in original Fontan procedure. B, Contrast-enhanced 3D reformatted volume-rendered MR angiography image shows hypoplastic right ventricle (star), large right atrium (arrows), and patent conduit (arrowhead) between right atrial appendage and right pulmonary artery, as in original Fontan procedure, in 12-year-old boy. Yellow shows conduit, blue shows right atrium and right ventricle, and red shows left atrium and left ventricle. C, Sketch of Björk modification, which consists of inserting conduit (gray) (often valved) between right atrium and right ventricle. D, Sketch of lateral tunnel procedure. Diagram shows postoperative anatomy of intraatrial tunnel (lateral tunnel procedure). Baffle in right atrium directs inferior vena cava (IVC) flow to lower portion of divided superior vena cava (SVC), which is connected to pulmonary artery. Upper part of SVC is connected to superior aspect of pulmonary artery as in bidirectional Glenn shunts. Right and left pulmonary arteries are interconnected, while pulmonary trunk is disconnected from heart. Most of right atrium is excluded from systemic venous circuit. Gray area shows right atrial baffle connected to right pulmonary artery and IVC, pulmonary trunk disconnected from heart, and SVC to right pulmonary artery anastomosis. E, Sketch shows extracardiac Fontan procedure, in which IVC blood is directed to pulmonary artery via extracardiac conduit. SVC is anastomosed to pulmonary artery, as in modified Glenn shunt, and pulmonary trunk is disconnected from heart. Gray area shows extracardiac conduit connected to right pulmonary artery and IVC, pulmonary trunk disconnected from heart, and SVC to right pulmonary artery anastomosis. (Fig. 4 continues on next page) E AJR:189, December

6 F G H Fig. 4 (continued) Fontan procedures. F and G, Reconstructed shaded surface display gadolinium-enhanced 3D MR angiography (F) and coronal cine MR (G) images in 22-year-old woman reveal patency of extracardiac conduit (stars; yellow in F) between IVC and right pulmonary artery (stars) as well as anastomosis of SVC and proximal right pulmonary artery stenosis (arrows, F), as in modified extracardiac Fontan procedure. H, Sketch shows fenestrated Fontan, in which surgical creation of atrial septal defect in atrial patch or baffle (gray) provides escape valve, allowing right-to-left shunting to reduce pressure in systemic venous circuit, with attendant systemic hypoxemia. This fenestration either closes spontaneously or is occluded by device in due course. A B Fig. 5 Rastelli procedure. A, Drawing depicts Rastelli procedure postoperative anatomy. In this procedure, prosthetic tunnel (gray) is constructed from left ventricle to aorta through ventricular septal defect. Continuity between right ventricle and main pulmonary artery is restored with extracardiac conduit. B, Contrast-enhanced 3D shaded surface display MR angiography oblique coronal image shows conduit (yellow) between right ventricle and main pulmonary artery of Rastelli operation performed for dextrotransposition of great arteries in 28-year-old man with ventricular septal defect and left ventricular outflow tract obstruction AJR:189, December 2007

7 Normal Postoperative Imaging in Cyanotic Congenital Heart Diseases A A C B B D Fig. 6 Pulmonary artery banding. A, Sketch of pulmonary artery banding. Diagram shows surgical ligature around midportion of main pulmonary artery (gray) causing artificial pulmonary stenosis to reduce systolic pulmonary artery pressure. Repeated progressive occlusion and reopening are possible with new surgically implantable devices that actually behave like adjustable pulmonary artery bands. B, Reformatted shaded surface display contrastenhanced 3D MR angiography image depicts correct placement of pulmonary artery band in midportion of main pulmonary artery (arrowhead); procedure was performed for palliative correction of double-outlet right ventricle with large ventricular septal defect in 15-year-old girl. Blue shows right ventricle; yellow shows pulmonary artery banding; and red shows left ventricle, pulmonary veins, and aorta. Fig. 7 Complete surgical correction for tetralogy of Fallot. A, Sketch of corrective surgery for tetralogy of Fallot. Diagram shows closing of ventricular septal defect and widening of right ventricular outflow tract with patching of infundibular tract (gray). B, Bulge (arrowhead) visible on this axial cine MR image obtained during diastole is ventricular septal defect closed. Defect was closed during corrective surgery for tetralogy of Fallot in 20-year-old man. No residual left-to-right shunt was found in phase velocity mapping images (not shown). C, Bulge (arrow) of right ventricular outflow tract and of main pulmonary artery seen in this short-axis cine MR image of same patient shown in B is patch. D, Reformatted 3D shaded surface display MR coronal image of same patient shown in B and C shows enlarged right ventricular outflow tract (star) and pulmonary artery branches in which no significant narrowing or stenosis is visible after complete surgical repair of tetralogy of Fallot. Blue shows right atrium, right ventricle, and pulmonary arteries; and red shows right aortic arch and apex of left ventricle. AJR:189, December

8 Fig. 8 Atrial switch procedure. A, Sketch of atrial switch procedure. Diagram depicts postoperative status. Systemic venous flow is directed behind baffle into left atrium, through mitral valve, and out pulmonary artery to lungs. Pulmonary venous return is directed over baffle, into right atrium, through tricuspid valve, and out aorta. Gray area highlights left atrial baffle. B, Axial cine MR image obtained during diastole in 20-year-old man shows how atrial baffle (arrow) of Senning procedure for dextrotransposition of great arteries isolates mitral valve from pulmonary venous drainage. Pulmonary venous blood enters posterior pulmonary venous atrium and flows anteriorly across tricuspid valve (arrowhead). Note thickness of right ventricle wall. C, Coronal cine MR image obtained during diastole in same patient shown in B shows that superior (arrowhead) and inferior (arrow) venae cavae drain into systemic venous baffle (star). A C FOR YOUR INFORMATION This article is available for CME credit. See for more information. B D Fig. 9 Arterial switch operation (Jatene arterial switch procedure). A, Anatomic sketch after arterial switch operation (Jatene arterial switch procedure). This procedure consists of removing great vessels from their native ventricles and switching them to contralateral ventricles, with reimplantation of coronary arteries into neoaorta (gray). So-called Lecompte maneuver is performed to bring branch pulmonary arteries from their original posterior position to position anterior to aorta. B, Reconstructed shaded surface display gadoliniumenhanced 3D MR angiography image shows typical anatomic arrangement of ascending aorta (red) surrounded by pulmonary branches (blue) after Lecompte maneuver arterial switch operation for dextrotransposition of great arteries in 13-year-old girl. C, Axial cine MR image of same patient shown in B obtained at level of pulmonary bifurcation during diastole shows full length of patent right and left pulmonary arteries and typical anteroposterior position of pulmonary trunk with respect to ascending aorta. D, In this cine MR image of same patient shown in B and C, left and right pulmonary arteries appear to be mildly compressed (arrowheads) at same level as in C but during systole. Nonphysiologic anatomic relationship between ascending aorta and pulmonary branches causes hemodynamic changes in right and left pulmonary arteries. Phase velocity mapping (not shown) did not reveal significant hemodynamic narrowing or stenosis. FOR YOUR INFORMATION The reader s attention is directed to part 2 accompanying this article, titled Postoperative Imaging in Cyanotic Congenital Heart Diseases: Part 2, Complications, which begins on page AJR:189, December 2007