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DOI:10.2214/AJR.07.2889
AJR 2008; 191:854-861
© American Roentgen Ray Society

Review

Surgically Corrected Congenital Heart Disease: Utility of 64-MDCT

Philip J. Spevak1,2, Pamela T. Johnson3 and Elliot K. Fishman3

1 Department of Pediatrics, The Johns Hopkins Medical Institutions and Johns Hopkins Hospital, Brady 5, 600 N Wolfe St., Baltimore, MD 21287.
2 Department of Medicine, The Johns Hopkins Medical Institutions and Johns Hopkins Hospital, Baltimore, MD.
3 The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins Medical Institutions, Baltimore, MD.

Received July 19, 2007; accepted after revision March 24, 2008.

 
Address correspondence to P. J. Spevak (spevak{at}jhmi.edu).

CME

This article is available for CME credit.

See www.arrs.org for more information.


Abstract
Top
 Abstract
Introduction
 Scanning Protocols
 Clinical Applications
 Discussion
 References
 
OBJECTIVE. The purpose of this article is to review the CT appearance of postoperative morphology and complications after surgical correction of congenital heart anomalies.

CONCLUSION. Echocardiography is typically the initial imaging technique used for congenital heart disease; however, some thoracic regions are beyond the imaging scope of echocardiography, particularly after surgical revision. This article shows, through a series of illustrative cases, the usefulness of 64-MDCT in these patients.

Keywords: cardiac surgery • congenital heart disease • MDCT • three-dimensional rendering


Introduction
Top
 Abstract
 Introduction
Scanning Protocols
 Clinical Applications
 Discussion
 References
 
Imaging of surgically treated patients with congenital heart disease is complicated by the variable and complex cardiac anatomy in these patients, modification of complicated anatomy by surgical intervention, and interference from the frequently present conduits, baffles, stents, and coils. The clinician can choose from one of four techniques when imaging the patient with congenital heart disease: echocardiography, catheterization with angiography, MRI, and CT. Catheterization is uncommonly per formed for diagnostic reasons alone and is chosen predominantly to intervene thera peutically. Echocardiography is usually the initial choice because of the excellent resolution and the logistic simplicity. However, the post operative patient is often difficult to image because of degradation of acoustic windows. When echocardiographic images are inadequate to address a specific clinical question, the alternatives of cardiac MRI and CT must be weighed. If primarily additional functional information is im portant, MRI is preferred, particularly if longitudinal exami nations are anticipated. MRI has good spatial and temporal resolution, allowing excellent flow and volumetric functional evaluation and tissue characterization. Although MRI can be performed in some patients with selected implantable pacemakers, for many patients and at many centers, a pacemaker remains a contraindication to performing an MRI examination [1]. CT has outstanding spatial resolution; however, it suffers in its temporal resolution, making it an inferior technique for evaluating ventricular function, particularly when the heart rate is elevated.

If the clinical question requires further delineation of cardiac anatomy and morphology, CT and MRI can both be considered. However, in infants and toddlers, administration of sedation medication or even general anesthesia may be needed to complete MRI examinations. Current generation MDCT scanning times enable examinations to be completed in seconds, obviating sedation in most patients. Submillimeter isotropic resolution results in superior spatial resolution compared with MRI. These advantages must be balanced against the additional risk of ionizing radiation. Fortunately, measures to reduce radiation exposure are evolving, including reduction of tube current based on weight and size, modulation of tube current depending on anatomic position or phase of cardiac cycle (ECG-modulated pulsing), or reduction of tube voltage [2].

Although primary surgical repair of many congenital heart disorders is being performed early in life with greater frequency, some patients who have had palliative procedures at a young age will require imaging. Older children and adults with congenital heart disease who have undergone surgical correction constitute a growing population because of the improved survival after treatment. Accordingly, radiologists per forming MDCT will be imaging more of these patients for clinical assessment, and in the setting of suspected complications. This focused review presents a series of cases to show the utility of cardiac 64-MDCT for imaging patients with congenital heart disease who have undergone various forms of palliative or definitive surgical correction. Using a procedure-based approach, emphasis is placed on the anatomic configuration after surgical correction, potential complications that must be excluded, and the utility of MDCT for visualizing anatomic regions not accessible to echocardiography. The cases show the importance of 2D and 3D multiplanar viewing for revealing vascular anatomy, surgical anastomoses, and shunts or conduits that are often not fully visualized in an axial plane.


Scanning Protocols
Top
 Abstract
 Introduction
 Scanning Protocols
Clinical Applications
 Discussion
 References
 
In select cases, 16-MDCT may be satisfactory for imaging congenital heart disease. However, the temporal resolution of 64-MDCT results in acceptable image quality for a much higher percentage of patients. The faster acquisition time results in shorter breath-hold duration and a reduction in the volume of IV contrast material needed, with intraindividual comparison revealing improved image quality [3]. The narrow temporal window of data acquisition is particularly important for pediatric patients with high heart rates. Proper patient preparation is essential to performing high-quality studies, and one of our most important assets is a dedicated pediatric nurse who is adept with these delicate patients.

Protocol design is tailored to each case. Leschka et al. [2] have written a detailed summary of 64-MDCT protocols specific to each congenital cardiac anomaly, including contrast infusion, when to use ECG gating, anatomic region covered, and reconstruction parameters. In patients with shunts or baffles, the timing is often more difficult because of differential flow. Depending on the case, a single- or dual-phase acquisition may be indicated. This series of cases was performed on a commercially available 64-MDCT scanner (Sensation 64, Siemens Medi cal Solutions) using the following scanning protocol: 90–150 mAs (depending on patient size and weight); 120 kVp; pitch, 0.7; detector thickness, 0.6 mm; slice thickness, 0.75 mm; reconstruction interval, 0.5 mm; scanner rotation time, 0.33 second. Total study time is in the range of 1.5–5 seconds for a child and 10–12 seconds for an adult. Patients were injected with up to 2 mL/kg of Visipaque 320 (iodixanol, GE Healthcare) at an injection rate of 2 mL/s for children and 3–5 mL/s for adults. For complicated congenital heart cases, a saline flush is usually not used, to enable contrast opacification of both right and left sides of the heart. A flush will be used if the coronary arteries are being evaluated. We use a test-bolus technique to delineate the timing, using 5–10 mL of contrast agent with a 10-mL saline flush.


Figure 1
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  		Fig. 1A —15-month-old male infant who had previously undergone modified left Blalock-Taussig shunt and placement of central shunt. Left pulmonary artery could not be seen on echocardiography after central shunt was placed. AO = aorta. Axial volume rendering with clip plane editing from IV contrast-enhanced CT shows central shunt (arrow) arising from anterior aorta to supply mildly hypoplastic right pulmonary artery (RPA). Origin of left pulmonary artery is not well seen.

 


Figure 2
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  		Fig. 1B —15-month-old male infant who had previously undergone modified left Blalock-Taussig shunt and placement of central shunt. Left pulmonary artery could not be seen on echocardiography after central shunt was placed. AO = aorta. Coronal oblique multiplanar reconstruction (MPR) shows moderate to severe narrowing (arrow) of left pulmonary artery (LPA), and good-sized, more distal left pulmonary artery. LV = left ventricle.

 


Figure 3
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  		Fig. 1C —15-month-old male infant who had previously undergone modified left Blalock-Taussig shunt and placement of central shunt. Left pulmonary artery could not be seen on echocardiography after central shunt was placed. AO = aorta. Oblique color-coded volume rendering from left superior perspective shows length of left pulmonary artery (LPA) stenosis ({approx} 8 mm). Distance is particularly important to know in determining whether stenosis can be reached from midsternotomy, or if left thoracotomy is required.

 
In selected patients, such as those in whom coronary artery or cardiac wall motion evaluation is indicated, a gated study is performed. Retrospective gating as we perform it requires a slower heart rate, ideally less than 65 beats per minute (bpm) for adults with a 64-MDCT scanner. In children, gating can be performed up to a heart rate of 90 bpm with a 64-MDCT scanner. The protocol for adults in these cases was 400 mAs; 120 kVp; pitch, 0.2; detector thickness, 0.6 mm; slice thickness, 0.75 mm; reconstruction interval, 0.5 mm; scanner rotation time, 0.33 second; and total scanning time, less than 5 seconds.

All scan data were sent to an independent workstation (Leonardo, Siemens Medical So lutions) running InSpace software (Siemens). Three-dimensional renderings were developed using a combination of volume rendering and maximum intensity projection (MIP), in addition to 2D multiplanar reconstructions (MPRs). We perform 3D rendering on all patients because it adds additional information. Once the CT data are acquired, our goal is to extract the maximum information from the volume. These patients have complex anatomy that is often best visualized with volume rendering because it conveys 3D relationships not shown on MPRs or MIP. Although 3D rendering requires minimal additional time, it is available on most workstations and does not necessitate any additional radiation exposure. Further more, our referring physicians prefer to see complex anatomy in 3D.


Clinical Applications
Top
 Abstract
 Introduction
 Scanning Protocols
 Clinical Applications
Discussion
 References
 
Systemic and Venous Shunts to Augment Effective Pulmonary Blood Flow
A systemic shunt redirects blood from the aorta or a branch of the aorta to the pulmonary arteries in order to increase oxygen saturation. These include central shunts (surgical graft to the pulmonary arteries from the ascending aorta) (Fig. 1A, 1B, 1C), Potts shunts (from descending aorta to left pulmonary artery, no longer performed), Waterston shunts (from ascending aorta to right pulmonary artery), and Blalock-Taussig shunts (subclavian artery to ipsilateral pulmonary artery). The contemporary modified Blalock-Taussig shunt is performed by interposing a prosthetic graft from the subclavian or innominate artery to the ipsilateral branch pulmonary art ery via an end-to-end anastomosis [4]. Postoperative complications include distortion of the ipsilateral pulmonary artery, identified in 24–33% after a modified Blalock-Taussig shunt [5, 6], occurring more commonly in those who undergo shunt placement earlier in life [5]. Major (≥ 50%) pulmonary artery stenosis occurs in 14% of cases, and rarely, there is complete occlusion of the pulmonary artery or the shunt [5]. In approximately 50%, shunt narrowing occurs, usually at the anastomosis [6].


Figure 4
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  		Fig. 2A —7-year-old girl with double-outlet right ventricle status after pulmonary artery banding followed by bilateral bidirectional Glenn shunts. Catheterization revealed acceptable hemodynamics to proceed with Fontan procedure. MDCT was conducted to assess for branch pulmonary artery distortion, assess for aorta-to-pulmonary artery or venoatrial collaterals, and review caval–pulmonary artery connections. Sagittal multiplanar reconstruction (MPR) shows aorta (AO) and main pulmonary artery (MPA) arising from right ventricle (V). Note tight pulmonary artery band (arrow).

 


Figure 5
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  		Fig. 2B —7-year-old girl with double-outlet right ventricle status after pulmonary artery banding followed by bilateral bidirectional Glenn shunts. Catheterization revealed acceptable hemodynamics to proceed with Fontan procedure. MDCT was conducted to assess for branch pulmonary artery distortion, assess for aorta-to-pulmonary artery or venoatrial collaterals, and review caval–pulmonary artery connections. Coronal oblique color-coded volume-rendering with clip plane editing shows that left-sided Glenn anastomosis, from left superior vena cava (LSVC) to left pulmonary artery (LPA), is unobstructed and left pulmonary artery is of a good size. AO = aorta.

 


Figure 6
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  		Fig. 2C —7-year-old girl with double-outlet right ventricle status after pulmonary artery banding followed by bilateral bidirectional Glenn shunts. Catheterization revealed acceptable hemodynamics to proceed with Fontan procedure. MDCT was conducted to assess for branch pulmonary artery distortion, assess for aorta-to-pulmonary artery or venoatrial collaterals, and review caval–pulmonary artery connections. Coronal MPR shows that right-sided Glenn anastomosis (right superior vena cava [RSVC] to right pulmonary artery) is minimally distorted, with caval connection close to or extending across origin of right upper lobe pulmonary artery. CPA = central pulmonary artery.

 
Although echocardiography is often the initial imaging technique used to evaluate the branch pulmonary arteries, usually only the central pulmonary arteries are imaged because of acoustic interference by the lungs. Frequently in the postoperative patient, surgical clips or catheter-placed coils create imaging artifacts on MRI, which may obscure visualization of the branch pulmonary arteries. In this case, MDCT is helpful, particularly for the left pulmonary artery. The appearance of the left pulmonary artery and the extent of distortion are important to define preoperatively, before any additional sur gical intervention. If the area of distortion is too posterior to adequately visualize from a midsternotomy incision, the surgeon must approach it from a left thoracotomy.

Venous shunts, although not performed in neonates because of elevated pulmonary resistance, can be used to increase pulmonary blood flow after infants are approximately 3 months old. A classic Glenn shunt is a surgical connection between the vena cava and the transected ipsilateral pulmonary artery. These have been performed in the setting of tricuspid atresia and single ventricle [7], but they are essentially no longer used because of the undesirable creation of discontinuous branch pulmonary arteries. The currently performed bidirectional Glenn shunt connects the cranial segment of the transected superior vena cava to the right pulmonary artery via an end-to-side anastomosis, allowing blood to flow to both lungs [4] (Fig. 2A, 2B, 2C). A hemi-Fontan procedure, a variant of the bidirectional Glenn shunt, involves a second anastomosis of the caudal superior vena cava segment with the inferior right pulmonary artery and may facilitate a subsequent Fontan procedure. Sequelae after a Glenn shunt include decreased arterial diameter and flow in the contralateral pulmonary artery as well as development of decompressing venous collaterals (superior vena cava-to-inferior vena cava circulation), resulting in reduced oxygen saturation [7, 8]. Patients are also at risk for developing pulmonary arteriovenous fistulas (AVFs) (20%); the incidence correlates with the number of years after the procedure [7].

A Kawashima procedure is performed in the setting of heterotaxy syndrome and refers to placement of a bidirectional Glenn shunt in a patient with interruption of the inferior vena cava and azygous extension to the superior vena cava. This therefore redirects all systemic venous blood to the lungs except the hepatic and coronary venous return. A left-sided Kawashima vascular connection is anasto mosed to the left branch pulmonary artery. Postoperatively, patients have mild cyanosis because the desaturated hepatic venous blood is pumped along with the pulmonary venous blood to the body. Surgeons sometimes avoid redirecting hepatic venous drainage in patients with an interrupted inferior vena cava because of the complexity of incorporating this return. Unfortunately, failure to incorporate hepatic venous blood results in a number of patients after Kawashima repair developing a pulmonary arteriovenous malformation (AVM) [9]. When an AVM is present, a conduit may be placed to incorporate hepatic blood flow into the pulmonary circuit to facilitate its resolution [10]. Difficult to visualize with echocardiography, these conduits from the hepatic veins to the innominate vein can be evaluated with MDCT to exclude thrombosis or stenosis (Fig. 3A, 3B, 3C, 3D).


Figure 7
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  		Fig. 3A —12-year-old girl with double-outlet right ventricle, severely malaligned complete atrioventricular canal, ipsilateral pulmonary venous return, interrupted inferior vena cava with azygous extension to left superior vena cava, and abdominal situs inversus. Kawashima procedure was performed, and subsequently conduit was placed to incorporate hepatic blood flow into pulmonary circuit in order to treat pulmonary arteriovenous malformations. In these coronal volume renderings, conduit (C) is positioned to right of aorta (AO in A) and has mild narrowing as it turns superiorly (arrow in B). No thrombus was present. LIA in A = left innominate artery.

 

Figure 8
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  		Fig. 3B —12-year-old girl with double-outlet right ventricle, severely malaligned complete atrioventricular canal, ipsilateral pulmonary venous return, interrupted inferior vena cava with azygous extension to left superior vena cava, and abdominal situs inversus. Kawashima procedure was performed, and subsequently conduit was placed to incorporate hepatic blood flow into pulmonary circuit in order to treat pulmonary arteriovenous malformations. In these coronal volume renderings, conduit (C) is positioned to right of aorta (AO in A) and has mild narrowing as it turns superiorly (arrow in B). No thrombus was present. LIA in A = left innominate artery.

 

Figure 9
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  		Fig. 3C —12-year-old girl with double-outlet right ventricle, severely malaligned complete atrioventricular canal, ipsilateral pulmonary venous return, interrupted inferior vena cava with azygous extension to left superior vena cava, and abdominal situs inversus. Kawashima procedure was performed, and subsequently conduit was placed to incorporate hepatic blood flow into pulmonary circuit in order to treat pulmonary arteriovenous malformations. In more posterior coronal volume rendering with clip plane editing, aorta (AO) is shown arising from right ventricle (RV), and subaortic conus is present. A = right atrium, CV = connecting vein.

 

Figure 10
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  		Fig. 3D —12-year-old girl with double-outlet right ventricle, severely malaligned complete atrioventricular canal, ipsilateral pulmonary venous return, interrupted inferior vena cava with azygous extension to left superior vena cava, and abdominal situs inversus. Kawashima procedure was performed, and subsequently conduit was placed to incorporate hepatic blood flow into pulmonary circuit in order to treat pulmonary arteriovenous malformations. Coronal volume rendering with clip plane editing shows sites of ipsilateral pulmonary venous return (small arrows) and connection of left superior vena cava (LSVC) with left pulmonary artery (large arrow). Note right aortic arch (AO), right-sided stomach, and left-sided liver. Multiple small spleens were seen in right upper quadrant in addition to interrupted inferior vena cava with azygous continuation (not shown), typical of polysplenic form of heterotaxy syndrome.

 

Separation of Systemic and Pulmonary Circulations: Single and Biventricular Circuits
The Fontan procedure was initially conducted for tricuspid atresia and is currently performed as the final palliative procedure in any heart with single-ventricle physiology, such as hypoplastic left heart syndrome. This procedure involves separation of the systemic and pulmonary circulations. Systemic venous blood is routed directly to the lungs, which may be performed initially during a staged hemi-Fontan procedure or a bidirectional Glenn shunt. The single ventricle pumps exclusively (or nearly exclusively) to the body. Historically, the inferior vena cava connection involved an anastomosis between the superior aspect of the right atrium with the right pulmonary artery. More recently, the connection is made using an intraatrial baffle or an external conduit from the inferior vena cava to the pulmonary artery [11, 12] (Fig. 4A, 4B, 4C, 4D).


Figure 11
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  		Fig. 4A —19-year-old man with history of double-inlet left ventricle after Glenn shunt and Fontan procedure complicated by protein-losing enteropathy. MDCT was performed to assess cardiopulmonary morphology and function. Coronal color-coded volume rendering shows external conduit from inferior vena cava to right pulmonary artery. Conduit is well seen without artifact using MDCT.

 

Figure 12
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  		Fig. 4B —19-year-old man with history of double-inlet left ventricle after Glenn shunt and Fontan procedure complicated by protein-losing enteropathy. MDCT was performed to assess cardiopulmonary morphology and function. Coronal volume rendering with clip plane editing enables visualization of internal portion of conduit from inferior vena cava to right pulmonary artery, which was patent.

 

Figure 13
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  		Fig. 4C —19-year-old man with history of double-inlet left ventricle after Glenn shunt and Fontan procedure complicated by protein-losing enteropathy. MDCT was performed to assess cardiopulmonary morphology and function. Sagittal volume rendering with clip plane editing shows persistent left superior vena cava (arrows) to coronary sinus, which is dilated.

 

Figure 14
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  		Fig. 4D —19-year-old man with history of double-inlet left ventricle after Glenn shunt and Fontan procedure complicated by protein-losing enteropathy. MDCT was performed to assess cardiopulmonary morphology and function. Sagittal oblique volume rendering from inferolateral orientation depicts prominent venous collaterals along cardiac border that arose from left vena cava. Also seen is conduit from inferior vena cava to right pulmonary artery.

 
The Fontan cavopulmonary pathway is at risk for thrombosis or suboptimal flow dynamics [11, 12]. Systemic circulation complications include subaortic obstruction, systemic ventricular dysfunction, and atrioventricular valve regurgitation [12]. Aortocollateral vessels and pulmonary AVFs may also develop, and alterations in venous pressure result in an increased propensity for pleural effusion and protein-losing entero pathy [12]. In the early postoperative period, an unusual complication is a large fluid collection adjacent to the external conduit (Fig. 5A, 5B). MDCT with IV contrast material can delineate the extent of such a collection, determine whether it represents a contained collection or a pseudoaneurysm, and show resolution after treatment.


Figure 15
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  		Fig. 5A —Unexpected desaturation after Fontan procedure in 33-year-old woman. At catheterization, there was distortion of external conduit by mediastinal mass. Echocardiography (not shown) showed that mass was fluid-filled. IV contrast-enhanced MDCT was performed to better understand nature of mediastinal mass and its relationship to external conduit. From this coronal multiplanar reconstruction (MPR), conduit (C) from inferior vena cava and hepatic veins to right pulmonary artery is well visualized and is surrounded by fluid collection (F). V = left ventricle, AO = aorta.

 

Figure 16
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  		Fig. 5B —Unexpected desaturation after Fontan procedure in 33-year-old woman. At catheterization, there was distortion of external conduit by mediastinal mass. Echocardiography (not shown) showed that mass was fluid-filled. IV contrast-enhanced MDCT was performed to better understand nature of mediastinal mass and its relationship to external conduit. Delayed IV contrast–enhanced axial MDCT image shows enhancing conduit (C) from inferior vena cava and hepatic veins to right pulmonary artery, surrounded by fluid collection (F). Note that, except for thin rim, fluid collection does not enhance, suggesting that it does not communicate with vascular bed. Collection was drained percutaneously. V = left ventricle, LA = left atrium.

 
In truncus arteriosus, a rare congenital anomaly, the pulmonary arteries arise from the aorta, which overrides a ventricular septal defect. Classification systems reflect the origins of the branch pulmonary arteries and whether the aortic arch is interrupted. During surgical repair, the ventricular septal defect is closed, and the pulmonary arteries are anastomosed to the right ventricle using a conduit. Follow-up requires evaluation for conduit or truncal valve stenosis or regurgitation, adequacy of ventricular septal defect closure, stenosis of the pulmonary arteries (Fig. 6), dilatation of the aortic root, and ventricular dysfunction [13]. Cardiac angiography can assess for hemodynamically significant stenosis and residual ventricular septal defects; however, the conduit to pulmonary artery anastomosis may not be fully visualized to enable adequate assessment of the pulmonary artery origins, which are seen well with MDCT (Fig. 6).


Figure 17
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  		Fig. 6 —3-month-old boy with type II truncus arteriosus after surgical anastomosis of pulmonary arteries to right ventricle using 11-mm conduit and repair of ventral septal defect. Postoperative catheterization showed minimal residual ventral septal defect and pressure gradient at origin of right (RPA) and left (LPA) pulmonary arteries. However, because of conduit orientation, pulmonary artery origins could not be visualized to determine caliber. Axial oblique volume-rendered CT image with clip plane editing shows that both proximal pulmonary arteries are narrowed, with right measuring 3.3 mm and left, 4.2 mm. Three months after CT, diminished right ventricular systolic function prompted cardiac catheterization to allow stent placement in both branch pulmonary arteries.

 
A Norwood procedure is the initial palliation for patients with hypoplastic left heart; it establishes a reliable egress of systemic arterial blood from the systemic right ventricle via the main pulmonary artery to the reconstructed aortic arch [11, 14]. Pulmonary blood flow is then provided by either a systemic shunt or a restrictive conduit from the right ventricle to the branch pulmonary arteries (Sano modification) [14]. After a Norwood procedure, CT is performed to visualize the aortic arch and ventricular or aortic pulmonary artery anastomoses (Fig. 7A, 7B, 7C). Distal aortic arch narrowing is an important complication to identify in order to avoid a pressure overload on the systemic right ventricle. Elevation in ventricular end-diastolic pressure related to ventricular dysfunction will raise pulmonary venous pressure (and then pulmonary artery pressure) and increase the risk of subsequent Glenn or Fontan procedures.


Figure 18
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  		Fig. 7A —3.5-year-old boy with bilateral superior vena cava and hypoplastic left heart after bilateral, bidirectional Glenn shunts and an initial Norwood procedure. Oxygen saturation was less than expected, and mild right ventricular dysfunction was seen at echocardiography (not shown). MDCT was performed to image aortic arch, main pulmonary artery-to-aorta anastomosis, and cava–pulmonary artery connections. Coronal color-coded volume rendering shows that anastomosis between ascending aorta (AO) and main pulmonary artery (MPA) is wide, resulting in dilated neoascending aorta.

 

Figure 19
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  		Fig. 7B —3.5-year-old boy with bilateral superior vena cava and hypoplastic left heart after bilateral, bidirectional Glenn shunts and an initial Norwood procedure. Oxygen saturation was less than expected, and mild right ventricular dysfunction was seen at echocardiography (not shown). MDCT was performed to image aortic arch, main pulmonary artery-to-aorta anastomosis, and cava–pulmonary artery connections. Coronal volume rendering with clip plane editing confirms that connection of right superior vena cava (RSVC) to right pulmonary artery (asterisk) is unobstructed. Arrow points to anastomosis between aorta (AO) and main pulmonary artery (MPA). RA = right atrium, RV = right ventricle.

 

Figure 20
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  		Fig. 7C —3.5-year-old boy with bilateral superior vena cava and hypoplastic left heart after bilateral, bidirectional Glenn shunts and an initial Norwood procedure. Oxygen saturation was less than expected, and mild right ventricular dysfunction was seen at echocardiography (not shown). MDCT was performed to image aortic arch, main pulmonary artery-to-aorta anastomosis, and cava–pulmonary artery connections. Sagittal volume rendering with clip plane editing delineates dilated neoascending aorta (NeoAO) and shows that arch is unobstructed.

 
Augmentation of Pulmonary Artery Flow for Pulmonic Atresia with Tetralogy of Fallot
In patients with severe pulmonary atresia resistant to interventional dilatation, arterial stents or surgical conduits may be required to augment pulmonary artery flow distal to the region of narrowing (Fig. 8A, 8B).


Figure 21
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  		Fig. 8A —17-year-old girl with history of tetralogy of Fallot and pulmonary atresia, after intracardiac repair with right ventricular outflow patch, right ventricular–pulmonary artery conduit valve replacement, and stent enlargement of left pulmonary artery, followed by surgical replacement of right ventricle-to-pulmonary artery conduit. Pulmonary perfusion studies (not shown) showed 35% flow to right lung and 65% to left lung. Branch pulmonary arteries were not visualized on echocardiography (not shown) but are known to be stenotic. MDCT was performed to delineate anatomy in consideration of augmenting flow to right lung by dilatation. Axial volume rendering from superior orientation with clip plane editing delineates unifocalization of collateral (arrows) supplying blood to right lower lobe. Collateral now passes anterior to ascending aorta. Because of critical right pulmonary artery hypoplasia (shown in B), this collateral is important to right lung flow.

 

Figure 22
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  		Fig. 8B —17-year-old girl with history of tetralogy of Fallot and pulmonary atresia, after intracardiac repair with right ventricular outflow patch, right ventricular–pulmonary artery conduit valve replacement, and stent enlargement of left pulmonary artery, followed by surgical replacement of right ventricle-to-pulmonary artery conduit. Pulmonary perfusion studies (not shown) showed 35% flow to right lung and 65% to left lung. Branch pulmonary arteries were not visualized on echocardiography (not shown) but are known to be stenotic. MDCT was performed to delineate anatomy in consideration of augmenting flow to right lung by dilatation. Axial CT image shows severe hypoplasia of native right pulmonary artery. Cardiac catheterization (not shown), performed several months later, confirmed hypoplasia of right pulmonary artery and branch pulmonary artery distortion as well as collaterals from left lower lobe pulmonary artery and right internal mammary artery to right pulmonary arterial circulation, latter of which was embolized. MDCT detected extensive aortic collaterals (not shown), which were embolized at catheterization.

 

Revising Transposed Outflow Tracts
Older techniques used to correct transposition of the great vessels include the Senning and Mustard procedures, aimed at revising the venous return. This was accomplished with an atrial baffle composed of autologous tissue (Senning) or synthetic material (Mustard) in conjunction with atrial septal resection [15]. Venous inflow was diverted via the baffle to the contralateral atrio ventricular valve and ventricle [15]. Com plications include arrhythmia, sudden death, right ventricular dysfunction, tricuspid regurgitation, obstruction of the atrial baffle due to narrowing, systemic and pulmonary venous obstruction, and atrial baffle leak [16, 17]. Repair for transposition of the great vessels is currently most commonly performed with an arterial switch procedure; however, not all patients are candidates. The pulmonary artery and aorta superior to the sinotubular junction (i.e., distal to coronary artery origins) are transected and reattached in the alternative location, and the coronary arteries migrate to the neoaortic root [15, 18]. Potential cardiopulmonary complications after an arterial switch operation include anastomotic obstruction (most commonly pulmonary), ventricular dysfunction, central and peripheral pulmonary stenosis (with branch pulmonary artery distortion occurring more commonly on the left side), neoaortic insufficiency, mitral regurgitation, left mainstem bronchus compression resulting from posteriorly displaced aorta, and less frequently, coronary artery stenoses [15, 18]. In the setting of compromised oxygenation postoperatively, MDCT can add considerable information in addition to that provided by echocardiography to determine whether a pulmonary artery anomaly is the underlying cause (Fig. 9A, 9B, 9C, 9D).


Figure 23
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  		Fig. 9A —27-day-old, 3.4-kg female infant with transposition of great vessels who underwent arterial switch procedure. Branch pulmonary arteries are draped anterior to ascending aorta (Lecompte maneuver); ductus is ligated but aortic end remains patent. Postoperatively, patient had persistent tachypnea and right lung atelectasis. MDCT was performed to evaluate branch pulmonary arteries and right lung collapse in order to determine cause of respiratory distress. Coronal oblique color-coded volume rendering shows that main pulmonary artery (MPA) anastomosis is unobstructed. MPA and left pulmonary artery (LPA) pass anterior to ascending aorta (AO). RV = right ventricle, LV = left ventricle.

 

Figure 24
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  		Fig. 9B —27-day-old, 3.4-kg female infant with transposition of great vessels who underwent arterial switch procedure. Branch pulmonary arteries are draped anterior to ascending aorta (Lecompte maneuver); ductus is ligated but aortic end remains patent. Postoperatively, patient had persistent tachypnea and right lung atelectasis. MDCT was performed to evaluate branch pulmonary arteries and right lung collapse in order to determine cause of respiratory distress. Sagittal color-coded volume rendering confirms that left main coronary artery (arrow) is unobstructed. Aortic end of ductus arteriosus (DA) is noted. LV = left ventricle, AO = aorta.

 

Figure 25
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  		Fig. 9C —27-day-old, 3.4-kg female infant with transposition of great vessels who underwent arterial switch procedure. Branch pulmonary arteries are draped anterior to ascending aorta (Lecompte maneuver); ductus is ligated but aortic end remains patent. Postoperatively, patient had persistent tachypnea and right lung atelectasis. MDCT was performed to evaluate branch pulmonary arteries and right lung collapse in order to determine cause of respiratory distress. On this coronal color-coded volume rendering from superior orientation, branch pulmonary arteries are well seen and undistorted. RPA = right pulmonary artery, LPA = left pulmonary artery.

 

Figure 26
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  		Fig. 9D —27-day-old, 3.4-kg female infant with transposition of great vessels who underwent arterial switch procedure. Branch pulmonary arteries are draped anterior to ascending aorta (Lecompte maneuver); ductus is ligated but aortic end remains patent. Postoperatively, patient had persistent tachypnea and right lung atelectasis. MDCT was performed to evaluate branch pulmonary arteries and right lung collapse in order to determine cause of respiratory distress. Coronal multiplanar reconstruction reveals bilateral atelectasis (right worse than left), accounting for patient's respiratory symptoms.

 


Discussion
Top
 Abstract
 Introduction
 Scanning Protocols
 Clinical Applications
 Discussion
References
 
The cases presented show how MDCT with 2D and 3D renderings can play an important role in the care of the patient with congenital heart disease by providing information not available with echocardiography. For certain anatomic regions, including the cardiac septa and valves, echocardiography has been shown to be superior to CT [19, 20]. However, CT has particular value beyond echocardiography for evaluating branch pulmonary arteries, particularly the left [19, 21, 22]; the aortic arch [23, 24]; complex abnormalities of systemic and pulmonary venous return [20, 25, 26]; the coronary sinus and inferior vena cava [19]; the coronary arteries [19, 20]; aortopulmonary collaterals [19, 21]; surgically placed conduits, baffles, and shunts [21]; and associated airway abnormalities [27, 28].

It is our practice to initially image all patients with echocardiography. If clinically important questions remain, we identify alternative techniques expected to offer adequate spatial and temporal resolution to answer the remaining questions. If more than one technique is suitable, we choose the technique on the basis of the patient characteristics (e.g., length of time able to tolerate scanning, clinical stability, feasibility of transport) and examination requirements (e.g., need for sedation).

In certain ways, we are at a golden moment in cardiac imaging because of the remarkable advances to date and the anticipated advances over the next 5 years. For echocardiography, anticipated changes are the increased application of 3D scanning and regional measures of ventricular function. For MRI, wider application of parallel processing and navigator sequences should decrease the need for patient sedation and should shorten scanning time. Scanning time may further decrease (or resolution increase) with more extensive use of 3-T scanners. For CT, dual-source scanners, which can decrease scanning time by half and reduce dose as well, should allow still further improvements in spatial resolution and shorter scanning times. Perhaps even more important, the improvements in temporal resolution will allow better quanti fication of ventricular function.

As cross-sectional imaging techniques become more widely used to evaluate patients with congenital heart disease, radiologists who interpret these studies will need to thoroughly understand the clinical and surgical history to assist in managing each of these challenging patients, and will need to maintain an understanding of the normal postoperative appearances and potential complications after surgical correction.


References
Top
 Abstract
 Introduction
 Scanning Protocols
 Clinical Applications
 Discussion
 References
 

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J. R. Dillman and R. J. Hernandez
Role of CT in the Evaluation of Congenital Cardiovascular Disease in Children
Am. J. Roentgenol., May 1, 2009; 192(5): 1219 - 1231.
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