DOI: 10.1148/rg.273065713
RadioGraphics 2007;27:829-846
© RSNA, 2007
Pre- and Postoperative Evaluation of Congenital Heart Disease in Children and Adults with 64-Section CT1
Sebastian Leschka, MD,
Erwin Oechslin, MD,
Lars Husmann, MD,
Lotus Desbiolles, MD,
Borut Marincek, MD,
Michele Genoni, MD,
René Prêtre, MD,
Rolf Jenni, MD,
Simon Wildermuth, MD, and
Hatem Alkadhi, MD
1 From the Institute of Diagnostic Radiology (S.L., L.H., L.D., B.M., S.W., H.A.), Cardiovascular Center (E.O., R.J.), and Clinic for Cardiovascular Surgery (M.G., R.P.), University Hospital Zurich, Raemistrasse 100, 8091 Zurich, Switzerland; and Congenital Cardiac Centre for Adults, Toronto General Hospital/University Health Network, Toronto, Ontario, Canada (E.O.). Received April 21, 2006; revision requested July 6 and received August 21; accepted December 6. Supported by the National Center of Competence in Research, Computer Aided and Image Guided Medical Interventions (NCCR-CO ME), of the Swiss National Science Foundation; and by the Georg und Bertha Schwyzer-Winiker Stiftung, Zurich, Switzerland. All authors have no financial relationships to disclose.
Address correspondence to H.A. (e-mail: hatem.alkadhi{at}usz.ch).
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Abstract
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Although echocardiography is the imaging method of choice for diagnostic, preoperative, and postoperative evaluation of congenital heart disease, computed tomography (CT) is a helpful complementary imaging modality, particularly for postoperative evaluation. A thorough understanding of the normal anatomy and the morphologic features of congenital heart diseases is a prerequisite for choosing the optimal CT technique and achieving an accurate diagnosis. Furthermore, a close collaboration with a cardiologist with special training and expertise in congenital heart diseases is required. A sequential segmental approach should be used in evaluating morphologic features, especially during the review of CT images obtained in patients with rare congenital cardiac defects and in postoperative adult patients. To accurately document and interpret the altered flow conditions in patients with congenital heart disease, knowledge of the wide spectrum of surgical procedures and familiarity with the dedicated protocols for performing 64-section CT are needed.
© RSNA, 2007
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LEARNING OBJECTIVES FOR TEST 5
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After reading this article and taking the test, the reader will be able to:
- Identify the anatomic and morphologic features of congenital heart disease.
- Describe a sequential segmental approach that may be used in interpreting CT images of congenital heart disease.
- Determine appropriate CT protocols for evaluating congenital heart disease according to the anatomic, pathologic, and hemodynamic characteristics of the defect; type of previous surgical repair; and patients age and ability to cooperate.
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Introduction
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Advances in medicine have increased the life expectancy of patients with congenital heart disease. Thus, the population of individuals who may benefit from long-term follow-up with cross-sectional imaging is steadily increasing (1). Cross-sectional imaging with magnetic resonance (MR) or computed tomography (CT) may help overcome the limitations of echocardiography, including a poor acoustic window and poor depiction of extracardiac vascular structures (2), as well as limitations of conventional angiography such as overlap of adjacent cardiovascular structures, difficulties in simultaneously depicting the systemic and the pulmonary vascular systems, and catheter-related complications (2,3). Despite the great capabilities of MR imaging for anatomic and functional assessment of the heart, an examination with this modality is time-consuming and may require a lengthy period of patient sedation; therefore, the use of MR imaging in seriously ill or uncooperative patients is often limited (3). In addition, the use of MR imaging is contraindicated in patients with a pacemaker or an internal cardioverter-defibrillator (4).
CT has the advantages of widespread availability and short acquisition times. The development of 64-section CT, with increased scanning speed, higher spatial resolution, and enhanced capabilities for simultaneous evaluation of cardiovascular structures and lung parenchyma, has increased the clinical application of CT for the evaluation of patients with congenital heart diseases (5). When coupled with electrocardiographic (ECG) data, CT images accurately delineate rapidly moving cardiac and paracardiac structures and allow an assessment of coronary artery disease (610) and associated coronary artery anomalies (11). In addition, 64-section CT may be used to obtain functional data about motion of the ventricular wall (12) or cardiac valves (13,14). The modality should play a particularly substantial role in the evaluation of patients after surgical intervention for congenital heart disease. Its drawbacks include exposure of the patient to ionizing radiation and the risks inherent in iodinated contrast material. These disadvantages must be kept in mind when considering the use of CT, particularly in pediatric patients.
The purpose of this article is to underscore the importance of knowledge about the anatomy, morphology, and terminology of congenital heart disease and to describe a sequential segmental approach for the accurate and comprehensive assessment of pediatric and adult patients with such disease. In addition, the article provides guidelines for designing a CT protocol based on the anatomic, pathologic, and hemodynamic characteristics of the cardiac defect; the type of previous surgical repair; and the patients age and ability to cooperate. The CT findings of various common and rare congenital cardiac defects before and after surgery are described and explained.
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Scanning Technique
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Careful preparation is a prerequisite for CT in both pediatric and adult patients. In our experience, short-term sedation often is necessary, particularly in young children (<5 years old). We prefer the administration of midazolam hydrochloride 0.1 mg/kg body weight (Dormicum 0.5% solution; Hoffmann-La Roche, Grenzach-Wyhlen, Germany) via the intranasal route.
Optimal contrast agent administration and CT scanning techniques vary, depending on the anatomic, pathologic, and hemodynamic characteristics of the cardiac defect, the type of previous surgical repair, and the patients age and level of cooperation. Consequently, the CT protocol should be selected on a case-by-case basis. The Table summarizes the preferred scanning protocols for patients with a suspected cardiac disorder. We routinely use a 64-section CT scanner (Sensation 64; Siemens Medical Solutions, Forchheim, Germany) with a detector collimation of 64 x 0.6 mm (64 sections, each with a thickness of 0.6 mm), pitch of 1.4, gantry rotation time of 330 msec, tube voltage of 120 kV, and fully automated real-time anatomy-based dose regulation (CARE Dose 4D) to reduce radiation exposure (15). For image acquisitions in adult patients, the tube current is set to 220 mA, whereas in pediatric patients a body weightbased low-dose protocol (120 kV, 3080 mA, pitch of 2.0) is used to further reduce radiation exposure. The size of pediatric patients varies from that of a premature infant to that of an adult, and the tube current should be increased if the patients body weight exceeds approximately 50 kg, to improve the signal-to-noise ratio. Lowering of the tube voltage to 80 kV in pediatric patients was recently recommended to further reduce their radiation exposure without impairing the image quality (3). These protocols are used in patients with extracardiac abnormalities and abnormal connections. Scanning of the entire thorax is performed within one breath hold of approximately 5 seconds.
In patients with a complex cardiac abnormality or with a minor intracardiac abnormality and an abnormal communication, synchronization of the CT data acquisition with the ECG tracing is recommended to reduce motion artifacts, which may obscure abnormalities. Data acquisition is performed in a craniocaudal direction from the level of the tracheal bifurcation to the diaphragm. Scanning parameters include a detector collimation of 32 x 0.6 mm, section collimation of 64 x 0.6 mm by means of a z-flying focal spot, gantry rotation time of 330 msec, pitch of 0.2, and tube potential of 120 kVp. ECG-controlled tube current modulation (ECG pulsing) is applied with a nominal tube current during diastole (600 mAs) and a reduced tube current during systole (120 mAs). The use of this technique leads to a considerable reduction in radiation dose (16). However, the ability to perform ECG-gated CT is limited by the temporal resolution of the scanner, and imaging with this technique may not be feasible in patients with high heart rates (eg, young children, who may have a heart rate as high as 200 beats per minute). Thus, ECG-gated CT in children should be performed only in the presence of specific indications that outweigh the potential risk of radiation exposure. In contrast to nongated scanning, ECG-gated CT scanning of the entire thorax requires an increase in scanning time to approximately 20 seconds, with a resultant increase in radiation dose. Image quality is usually reduced in patients with elevated heart rates but is still sufficient to evaluate intracardiac abnormalities or the course of anomalous coronary arteries. We do not consider the administration of a ß-blocker before CT mandatory for the evaluation of patients with congenital heart disease.
For vascular and cardiac opacification, a non-ionic contrast agent (Visipaque 320; GE Healthcare, Little Chalfont, England) that contains 320 mg of iodine per milliliter is injected via an ante-cubital vein at a dose of 11.5 mL/kg body weight and a rate of 34 mL/sec. To reduce artifacts from undiluted contrast material and to reduce the total amount of contrast material, a saline bolus chasing technique should be applied. In neonates and infants, the injection access route usually necessitates a lower flow rate; thus, the injection rate should be reduced to 2 mL/sec or less. The scanning delay is determined with an automatic bolus tracking technique. In the pediatric patient, a region of interest is placed in the left ventricle, and a threshold attenuation of 200 HU is set. In adults, the region of interest is placed in the ascending aorta, and the attenuation threshold is set at 140 HU (17). In children and uncooperative adults, scanning is performed during quiet breathing, usually without serious impairment of depiction of intracardiac structures and the course of anomalous coronary arteries. Sections with a thickness of 2.0 mm (increment of 1.5 mm) and a medium (soft-tissue) reconstruction kernel (B30f) are used for image interpretation at nongated CT. For assessing ventricular wall motion, cardiac valves, and coronary arteries, CT image data sets are reconstructed at a section width of 1.0 mm (increment of 0.8 mm) and synchronized to the ECG data in 10% steps of the R-R interval throughout the cardiac cycle. For optimal adaptation of the scanning technique and contrast agent protocol to the individual patients condition, the radiologist should have experience with the use of multidetector CT in patients with congenital heart disease.
Depending on the targeted structure and the purpose of the examination, various image data postprocessing techniques, including multiplanar reformation, maximum intensity projection (MIP), and volume rendering, are performed at a workstation equipped with dedicated software (Syngo InSpace4D; Siemens). Multiplanar reformation is a rapid and easy way to obtain images of structures that follow a course oblique to the axial plane. The plane of the reformatted image can be individually adjusted to the long axis of the structure of interest and to obtain accurate measurements (diameters or area of the dedicated structure). MIP images are obtained by projecting onto an image plane the highest-attenuation voxels encountered throughout a volume, a technique that facilitates the evaluation of structures that are not lying in a single plane. MIP is used mainly for the evaluation of vascular structures but has the disadvantage that vessels adjacent to bones may be obscured. Although volume rendering is the most time-consuming postprocessing technique, it is helpful for the three-dimensional visualization of complex anatomy, particularly for referring cardiologists and cardiovascular surgeons. In general, the combined use of various postprocessing techniques improves overall understanding of the cardiovascular situation and reduces the time needed for CT-based diagnosis (18), although the greatest amount of structural information about the cardiovascular anatomy usually is obtained with multiplanar reformation.
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Radiation Exposure
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Particular emphasis must be placed on radiation exposure issues, because the initial CT examination in patients with congenital heart disease often takes place in childhood or in early adulthood, and repeated scanning sometimes is necessary. If ECG-gated CT is to be used, the benefits of assessing ventricular function, cardiac valves, small intracardiac abnormalities, and coronary arteries must outweigh the higher risk of radiation exposure that is inherent in the technique. The effective radiation dose from ECG-gated CT of the heart is estimated to be approximately 15 mSv (19). For comparison, the effective radiation dose from nongated CT of the chest is approximately 5 mSv (20).
In general, three different algorithms may be used to reduce the radiation dose: First, weight-and size-based adjustments of tube current usually are performed according to the patients body habitus (eg, at thoracic CT, tube current is increased for the lateral projection and reduced in the anteroposterior projection) so that equal numbers of photons are received by the detector array (15,20). Second, an ECG-controlled tube current modulation algorithm known as ECG pulsing may be used to reduce radiation exposure by modulating the x-ray tube output according to the patients ECG tracing (16,21,22). During a user-defined phase of the cardiac cycle (usually between mid- and end-diastole), the output is kept at a nominal value; in the remainder of the cardiac cycle, the tube output is reduced by 80%. The quality of low-dose images obtained during systole is sufficient for the evaluation of ventricular functional parameters or the origin and course of coronary artery anomalies; however, it is usually inadequate for the assessment of stenoses or other abnormalities in more distal parts of the coronary artery tree. Mean dose reduction rates of 29% (21) and 37% (19) with the use of ECG pulsing in CT coronary angiography protocols have been reported. The effective dose for ECG-gated CT scanning with ECG pulsing has been estimated as 9 mSv (19). Third, the radiation dose may be lowered by reducing the tube voltage. In a comparison of cardiac CT protocols in which tube voltages of 120 kV and 100 kV were used, a dose savings of 57% was found (19). Decreased tube voltage also leads to increased opacification of contrast-enhanced structures because of an increase in the photoelectric effect and decreased Compton scattering (23). However, reduction of the tube voltage may result in increased image noise and decreased image quality. For noncardiac CT studies with decreased tube voltage, an increase of the tube current has been recommended to decrease image noise (24).
Although the radiation burden incurred by ECG-gated CT may be substantially reduced with dose-saving algorithms, a trade-off between a higher radiation dose and additional information provided by ECG gating must be made on a patient-by-patient basis.
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Sequential Segmental Approach
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Congenital heart defects may occur in many different combinations and be very complex, and their accurate diagnosis requires profound knowledge. Several approaches to classifying congenital heart diseases have been suggested, but no consensus has been reached about nomenclature. Nomenclature systems based on embryology were common in the past; other, more physiologic classification systems rely on clinical manifestations (eg, cyanosis) and the presence of an increase or decrease in pulmonary vascularity. In the latter system, congenital heart diseases may be classified as acyanotic with increased pulmonary vascularity (with a left-to-right shunt), acyanotic with normal pulmonary vascularity (with either out-flow obstruction or valvular insufficiency), cyanotic with decreased pulmonary vascularity (with an intracardiac defect that shunts blood away from the lung), or cyanotic with increased pulmonary vascularity (with bidirectional systemic and pulmonary venous shunts).
A simpler descriptive system derived from the sequential segmental approach was introduced in the 1980s. Based on the visualization of blood flow into, through, and out of the heart, the sequential segmental approach for interpreting anatomic images obtained in patients with congenital heart disease consists of the following steps: (a) determining cardiac sidedness (arrangement of atrial chambers), (b) locating the three segments (the atrial chambers, ventricular chambers, and the great arteries), (c) identifying the cardiac connections (venoatrial, atrioventricular, and ventriculoarterial), (d) assessing associated malformations, and (e) determining the cardiac position (position of the heart within the chest, orientation of the apex) (2529).
The cardiac chambers are defined according to their morphologic characteristics and need not be in the expected locations. Each chamber has intrinsic morphologic features. Thus, the reader of images must be familiar with normal and abnormal morphologic features. The assessment of sidedness (situs) includes cardiac, pulmonary, and abdominal sidedness, which usually are concordant. Cardiac sidedness is determined by the position of the morphologic right atrium and is independent from cardiac position, cardiac orientation, and the positions of the ventricles or great arteries. In situs solitus (the normal configuration), the morphologic right atrium lies to the right of the morphologic left atrium. In situs in-versus, the morphologic right atrium lies to the left of the morphologic left atrium.
The features of congenital heart disease in adults resemble those in pediatric patients but are more likely to include complications that result from hemodynamic alterations (eg, pulmonary hypertension, ventricular hypertrophy). Therefore, changes in cardiac chamber size and morphologic features should be thoroughly investigated with follow-up imaging studies (30).
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Normal Anatomy
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Knowledge of the normal cardiac morphology is a prerequisite for the evaluation of congenital heart disease (3,31). The heart consists of atrial, ventricular, and arterial segments (2529). These main cardiac segments and their connections (venoatrial, atrioventricular, and ventriculoarterial) must be completely identified.
Atria
The appendages are landmarks for morphologic right-sidedness or left-sidedness of the atria. The right atrial appendage is characterized by a triangular shape with a broad base and a terminal crest; the left atrial appendage has a fingerlike shape with a narrow entrance (Fig 1a).

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Figure 1a. Normal anatomy of the heart, mediastinal vessels, and main bronchi at multidetector CT. (a) Thin-section axial image at the level of the ascending aorta (Ao) and pulmonary valve (PV) demonstrates normal anatomy of the left atrium (LA) and right atrium. The right atrial appendage (RAA) typically has a triangular shape, with a wider opening and larger pectinate muscles (arrows) than those of the left atrial appendage (LAA), which has a fingerlike shape. (b) Thin-section double-oblique image through the left ventricular inflow and outflow tract shows normal anatomy of the morphologic left ventricle with fine trabeculae, the anterolateral and posteromedial papillary muscles, and fibrous continuity (arrowhead) between the aortic valve (AV) and the mitral valve (MV). (c) Thin-section oblique sagittal image depicts the morphologic right ventricle (RV), which is characterized by coarse trabeculae and a muscular crest, the crista supraventricularis (arrowhead), between the tricuspid valve (TV) and the pulmonary valve (PV). (d) Thin-section oblique sagittal image shows the normal anatomy of the ascending aorta (aA), the aortic arch (AoA), the aortic isthmus (Isth), and the descending aorta (dA). The ascending aorta originates from the aortic valve (AV), between the left atrium (LA) and right atrium (RA). (e) Thin-section axial image demonstrates the pulmonary trunk (PT), the left pulmonary artery (lPA), and the right pulmonary artery (rPA). The left pulmonary artery is shorter than the right, and it courses in a more posterior direction. The right pulmonary artery passes behind the ascending aorta and the superior vena cava and in front of the descending aorta (dA). (f) Thin-section coronal image obtained with lung window settings shows a normal bronchial branching pattern. The right upper lobe bronchus (RULB) is superior to the right pulmonary artery (rPA), whereas the left pulmonary artery (lPA) courses over the left upper lobe bronchus (LULB). (g) Thick-section oblique coronal image obtained with a slab thickness of 5 mm demonstrates normal connections of the three systemic veinsthe superior vena cava (SVC), inferior vena cava (IVC), and coronary sinus (CS)to the right atrium (RA). The mixture of highly contrast-enhanced venous blood from the superior vena cava with nonenhanced venous blood from the inferior vena cava is visible in the atrium. LA = left atrium. (h) Volume-rendered image, obtained with reconstruction in an oblique right-posterior plane by using the cut-plane mode, demonstrates the relationship of the superior (SVC) and inferior (IVC) venae cavae to other anatomic structures adjacent to the site of venous connection to the right atrium (RA).
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Figure 1b. Normal anatomy of the heart, mediastinal vessels, and main bronchi at multidetector CT. (a) Thin-section axial image at the level of the ascending aorta (Ao) and pulmonary valve (PV) demonstrates normal anatomy of the left atrium (LA) and right atrium. The right atrial appendage (RAA) typically has a triangular shape, with a wider opening and larger pectinate muscles (arrows) than those of the left atrial appendage (LAA), which has a fingerlike shape. (b) Thin-section double-oblique image through the left ventricular inflow and outflow tract shows normal anatomy of the morphologic left ventricle with fine trabeculae, the anterolateral and posteromedial papillary muscles, and fibrous continuity (arrowhead) between the aortic valve (AV) and the mitral valve (MV). (c) Thin-section oblique sagittal image depicts the morphologic right ventricle (RV), which is characterized by coarse trabeculae and a muscular crest, the crista supraventricularis (arrowhead), between the tricuspid valve (TV) and the pulmonary valve (PV). (d) Thin-section oblique sagittal image shows the normal anatomy of the ascending aorta (aA), the aortic arch (AoA), the aortic isthmus (Isth), and the descending aorta (dA). The ascending aorta originates from the aortic valve (AV), between the left atrium (LA) and right atrium (RA). (e) Thin-section axial image demonstrates the pulmonary trunk (PT), the left pulmonary artery (lPA), and the right pulmonary artery (rPA). The left pulmonary artery is shorter than the right, and it courses in a more posterior direction. The right pulmonary artery passes behind the ascending aorta and the superior vena cava and in front of the descending aorta (dA). (f) Thin-section coronal image obtained with lung window settings shows a normal bronchial branching pattern. The right upper lobe bronchus (RULB) is superior to the right pulmonary artery (rPA), whereas the left pulmonary artery (lPA) courses over the left upper lobe bronchus (LULB). (g) Thick-section oblique coronal image obtained with a slab thickness of 5 mm demonstrates normal connections of the three systemic veinsthe superior vena cava (SVC), inferior vena cava (IVC), and coronary sinus (CS)to the right atrium (RA). The mixture of highly contrast-enhanced venous blood from the superior vena cava with nonenhanced venous blood from the inferior vena cava is visible in the atrium. LA = left atrium. (h) Volume-rendered image, obtained with reconstruction in an oblique right-posterior plane by using the cut-plane mode, demonstrates the relationship of the superior (SVC) and inferior (IVC) venae cavae to other anatomic structures adjacent to the site of venous connection to the right atrium (RA).
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Figure 1c. Normal anatomy of the heart, mediastinal vessels, and main bronchi at multidetector CT. (a) Thin-section axial image at the level of the ascending aorta (Ao) and pulmonary valve (PV) demonstrates normal anatomy of the left atrium (LA) and right atrium. The right atrial appendage (RAA) typically has a triangular shape, with a wider opening and larger pectinate muscles (arrows) than those of the left atrial appendage (LAA), which has a fingerlike shape. (b) Thin-section double-oblique image through the left ventricular inflow and outflow tract shows normal anatomy of the morphologic left ventricle with fine trabeculae, the anterolateral and posteromedial papillary muscles, and fibrous continuity (arrowhead) between the aortic valve (AV) and the mitral valve (MV). (c) Thin-section oblique sagittal image depicts the morphologic right ventricle (RV), which is characterized by coarse trabeculae and a muscular crest, the crista supraventricularis (arrowhead), between the tricuspid valve (TV) and the pulmonary valve (PV). (d) Thin-section oblique sagittal image shows the normal anatomy of the ascending aorta (aA), the aortic arch (AoA), the aortic isthmus (Isth), and the descending aorta (dA). The ascending aorta originates from the aortic valve (AV), between the left atrium (LA) and right atrium (RA). (e) Thin-section axial image demonstrates the pulmonary trunk (PT), the left pulmonary artery (lPA), and the right pulmonary artery (rPA). The left pulmonary artery is shorter than the right, and it courses in a more posterior direction. The right pulmonary artery passes behind the ascending aorta and the superior vena cava and in front of the descending aorta (dA). (f) Thin-section coronal image obtained with lung window settings shows a normal bronchial branching pattern. The right upper lobe bronchus (RULB) is superior to the right pulmonary artery (rPA), whereas the left pulmonary artery (lPA) courses over the left upper lobe bronchus (LULB). (g) Thick-section oblique coronal image obtained with a slab thickness of 5 mm demonstrates normal connections of the three systemic veinsthe superior vena cava (SVC), inferior vena cava (IVC), and coronary sinus (CS)to the right atrium (RA). The mixture of highly contrast-enhanced venous blood from the superior vena cava with nonenhanced venous blood from the inferior vena cava is visible in the atrium. LA = left atrium. (h) Volume-rendered image, obtained with reconstruction in an oblique right-posterior plane by using the cut-plane mode, demonstrates the relationship of the superior (SVC) and inferior (IVC) venae cavae to other anatomic structures adjacent to the site of venous connection to the right atrium (RA).
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Figure 1d. Normal anatomy of the heart, mediastinal vessels, and main bronchi at multidetector CT. (a) Thin-section axial image at the level of the ascending aorta (Ao) and pulmonary valve (PV) demonstrates normal anatomy of the left atrium (LA) and right atrium. The right atrial appendage (RAA) typically has a triangular shape, with a wider opening and larger pectinate muscles (arrows) than those of the left atrial appendage (LAA), which has a fingerlike shape. (b) Thin-section double-oblique image through the left ventricular inflow and outflow tract shows normal anatomy of the morphologic left ventricle with fine trabeculae, the anterolateral and posteromedial papillary muscles, and fibrous continuity (arrowhead) between the aortic valve (AV) and the mitral valve (MV). (c) Thin-section oblique sagittal image depicts the morphologic right ventricle (RV), which is characterized by coarse trabeculae and a muscular crest, the crista supraventricularis (arrowhead), between the tricuspid valve (TV) and the pulmonary valve (PV). (d) Thin-section oblique sagittal image shows the normal anatomy of the ascending aorta (aA), the aortic arch (AoA), the aortic isthmus (Isth), and the descending aorta (dA). The ascending aorta originates from the aortic valve (AV), between the left atrium (LA) and right atrium (RA). (e) Thin-section axial image demonstrates the pulmonary trunk (PT), the left pulmonary artery (lPA), and the right pulmonary artery (rPA). The left pulmonary artery is shorter than the right, and it courses in a more posterior direction. The right pulmonary artery passes behind the ascending aorta and the superior vena cava and in front of the descending aorta (dA). (f) Thin-section coronal image obtained with lung window settings shows a normal bronchial branching pattern. The right upper lobe bronchus (RULB) is superior to the right pulmonary artery (rPA), whereas the left pulmonary artery (lPA) courses over the left upper lobe bronchus (LULB). (g) Thick-section oblique coronal image obtained with a slab thickness of 5 mm demonstrates normal connections of the three systemic veinsthe superior vena cava (SVC), inferior vena cava (IVC), and coronary sinus (CS)to the right atrium (RA). The mixture of highly contrast-enhanced venous blood from the superior vena cava with nonenhanced venous blood from the inferior vena cava is visible in the atrium. LA = left atrium. (h) Volume-rendered image, obtained with reconstruction in an oblique right-posterior plane by using the cut-plane mode, demonstrates the relationship of the superior (SVC) and inferior (IVC) venae cavae to other anatomic structures adjacent to the site of venous connection to the right atrium (RA).
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Figure 1e. Normal anatomy of the heart, mediastinal vessels, and main bronchi at multidetector CT. (a) Thin-section axial image at the level of the ascending aorta (Ao) and pulmonary valve (PV) demonstrates normal anatomy of the left atrium (LA) and right atrium. The right atrial appendage (RAA) typically has a triangular shape, with a wider opening and larger pectinate muscles (arrows) than those of the left atrial appendage (LAA), which has a fingerlike shape. (b) Thin-section double-oblique image through the left ventricular inflow and outflow tract shows normal anatomy of the morphologic left ventricle with fine trabeculae, the anterolateral and posteromedial papillary muscles, and fibrous continuity (arrowhead) between the aortic valve (AV) and the mitral valve (MV). (c) Thin-section oblique sagittal image depicts the morphologic right ventricle (RV), which is characterized by coarse trabeculae and a muscular crest, the crista supraventricularis (arrowhead), between the tricuspid valve (TV) and the pulmonary valve (PV). (d) Thin-section oblique sagittal image shows the normal anatomy of the ascending aorta (aA), the aortic arch (AoA), the aortic isthmus (Isth), and the descending aorta (dA). The ascending aorta originates from the aortic valve (AV), between the left atrium (LA) and right atrium (RA). (e) Thin-section axial image demonstrates the pulmonary trunk (PT), the left pulmonary artery (lPA), and the right pulmonary artery (rPA). The left pulmonary artery is shorter than the right, and it courses in a more posterior direction. The right pulmonary artery passes behind the ascending aorta and the superior vena cava and in front of the descending aorta (dA). (f) Thin-section coronal image obtained with lung window settings shows a normal bronchial branching pattern. The right upper lobe bronchus (RULB) is superior to the right pulmonary artery (rPA), whereas the left pulmonary artery (lPA) courses over the left upper lobe bronchus (LULB). (g) Thick-section oblique coronal image obtained with a slab thickness of 5 mm demonstrates normal connections of the three systemic veinsthe superior vena cava (SVC), inferior vena cava (IVC), and coronary sinus (CS)to the right atrium (RA). The mixture of highly contrast-enhanced venous blood from the superior vena cava with nonenhanced venous blood from the inferior vena cava is visible in the atrium. LA = left atrium. (h) Volume-rendered image, obtained with reconstruction in an oblique right-posterior plane by using the cut-plane mode, demonstrates the relationship of the superior (SVC) and inferior (IVC) venae cavae to other anatomic structures adjacent to the site of venous connection to the right atrium (RA).
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Figure 1f. Normal anatomy of the heart, mediastinal vessels, and main bronchi at multidetector CT. (a) Thin-section axial image at the level of the ascending aorta (Ao) and pulmonary valve (PV) demonstrates normal anatomy of the left atrium (LA) and right atrium. The right atrial appendage (RAA) typically has a triangular shape, with a wider opening and larger pectinate muscles (arrows) than those of the left atrial appendage (LAA), which has a fingerlike shape. (b) Thin-section double-oblique image through the left ventricular inflow and outflow tract shows normal anatomy of the morphologic left ventricle with fine trabeculae, the anterolateral and posteromedial papillary muscles, and fibrous continuity (arrowhead) between the aortic valve (AV) and the mitral valve (MV). (c) Thin-section oblique sagittal image depicts the morphologic right ventricle (RV), which is characterized by coarse trabeculae and a muscular crest, the crista supraventricularis (arrowhead), between the tricuspid valve (TV) and the pulmonary valve (PV). (d) Thin-section oblique sagittal image shows the normal anatomy of the ascending aorta (aA), the aortic arch (AoA), the aortic isthmus (Isth), and the descending aorta (dA). The ascending aorta originates from the aortic valve (AV), between the left atrium (LA) and right atrium (RA). (e) Thin-section axial image demonstrates the pulmonary trunk (PT), the left pulmonary artery (lPA), and the right pulmonary artery (rPA). The left pulmonary artery is shorter than the right, and it courses in a more posterior direction. The right pulmonary artery passes behind the ascending aorta and the superior vena cava and in front of the descending aorta (dA). (f) Thin-section coronal image obtained with lung window settings shows a normal bronchial branching pattern. The right upper lobe bronchus (RULB) is superior to the right pulmonary artery (rPA), whereas the left pulmonary artery (lPA) courses over the left upper lobe bronchus (LULB). (g) Thick-section oblique coronal image obtained with a slab thickness of 5 mm demonstrates normal connections of the three systemic veinsthe superior vena cava (SVC), inferior vena cava (IVC), and coronary sinus (CS)to the right atrium (RA). The mixture of highly contrast-enhanced venous blood from the superior vena cava with nonenhanced venous blood from the inferior vena cava is visible in the atrium. LA = left atrium. (h) Volume-rendered image, obtained with reconstruction in an oblique right-posterior plane by using the cut-plane mode, demonstrates the relationship of the superior (SVC) and inferior (IVC) venae cavae to other anatomic structures adjacent to the site of venous connection to the right atrium (RA).
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Figure 1g. Normal anatomy of the heart, mediastinal vessels, and main bronchi at multidetector CT. (a) Thin-section axial image at the level of the ascending aorta (Ao) and pulmonary valve (PV) demonstrates normal anatomy of the left atrium (LA) and right atrium. The right atrial appendage (RAA) typically has a triangular shape, with a wider opening and larger pectinate muscles (arrows) than those of the left atrial appendage (LAA), which has a fingerlike shape. (b) Thin-section double-oblique image through the left ventricular inflow and outflow tract shows normal anatomy of the morphologic left ventricle with fine trabeculae, the anterolateral and posteromedial papillary muscles, and fibrous continuity (arrowhead) between the aortic valve (AV) and the mitral valve (MV). (c) Thin-section oblique sagittal image depicts the morphologic right ventricle (RV), which is characterized by coarse trabeculae and a muscular crest, the crista supraventricularis (arrowhead), between the tricuspid valve (TV) and the pulmonary valve (PV). (d) Thin-section oblique sagittal image shows the normal anatomy of the ascending aorta (aA), the aortic arch (AoA), the aortic isthmus (Isth), and the descending aorta (dA). The ascending aorta originates from the aortic valve (AV), between the left atrium (LA) and right atrium (RA). (e) Thin-section axial image demonstrates the pulmonary trunk (PT), the left pulmonary artery (lPA), and the right pulmonary artery (rPA). The left pulmonary artery is shorter than the right, and it courses in a more posterior direction. The right pulmonary artery passes behind the ascending aorta and the superior vena cava and in front of the descending aorta (dA). (f) Thin-section coronal image obtained with lung window settings shows a normal bronchial branching pattern. The right upper lobe bronchus (RULB) is superior to the right pulmonary artery (rPA), whereas the left pulmonary artery (lPA) courses over the left upper lobe bronchus (LULB). (g) Thick-section oblique coronal image obtained with a slab thickness of 5 mm demonstrates normal connections of the three systemic veinsthe superior vena cava (SVC), inferior vena cava (IVC), and coronary sinus (CS)to the right atrium (RA). The mixture of highly contrast-enhanced venous blood from the superior vena cava with nonenhanced venous blood from the inferior vena cava is visible in the atrium. LA = left atrium. (h) Volume-rendered image, obtained with reconstruction in an oblique right-posterior plane by using the cut-plane mode, demonstrates the relationship of the superior (SVC) and inferior (IVC) venae cavae to other anatomic structures adjacent to the site of venous connection to the right atrium (RA).
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Figure 1h. Normal anatomy of the heart, mediastinal vessels, and main bronchi at multidetector CT. (a) Thin-section axial image at the level of the ascending aorta (Ao) and pulmonary valve (PV) demonstrates normal anatomy of the left atrium (LA) and right atrium. The right atrial appendage (RAA) typically has a triangular shape, with a wider opening and larger pectinate muscles (arrows) than those of the left atrial appendage (LAA), which has a fingerlike shape. (b) Thin-section double-oblique image through the left ventricular inflow and outflow tract shows normal anatomy of the morphologic left ventricle with fine trabeculae, the anterolateral and posteromedial papillary muscles, and fibrous continuity (arrowhead) between the aortic valve (AV) and the mitral valve (MV). (c) Thin-section oblique sagittal image depicts the morphologic right ventricle (RV), which is characterized by coarse trabeculae and a muscular crest, the crista supraventricularis (arrowhead), between the tricuspid valve (TV) and the pulmonary valve (PV). (d) Thin-section oblique sagittal image shows the normal anatomy of the ascending aorta (aA), the aortic arch (AoA), the aortic isthmus (Isth), and the descending aorta (dA). The ascending aorta originates from the aortic valve (AV), between the left atrium (LA) and right atrium (RA). (e) Thin-section axial image demonstrates the pulmonary trunk (PT), the left pulmonary artery (lPA), and the right pulmonary artery (rPA). The left pulmonary artery is shorter than the right, and it courses in a more posterior direction. The right pulmonary artery passes behind the ascending aorta and the superior vena cava and in front of the descending aorta (dA). (f) Thin-section coronal image obtained with lung window settings shows a normal bronchial branching pattern. The right upper lobe bronchus (RULB) is superior to the right pulmonary artery (rPA), whereas the left pulmonary artery (lPA) courses over the left upper lobe bronchus (LULB). (g) Thick-section oblique coronal image obtained with a slab thickness of 5 mm demonstrates normal connections of the three systemic veinsthe superior vena cava (SVC), inferior vena cava (IVC), and coronary sinus (CS)to the right atrium (RA). The mixture of highly contrast-enhanced venous blood from the superior vena cava with nonenhanced venous blood from the inferior vena cava is visible in the atrium. LA = left atrium. (h) Volume-rendered image, obtained with reconstruction in an oblique right-posterior plane by using the cut-plane mode, demonstrates the relationship of the superior (SVC) and inferior (IVC) venae cavae to other anatomic structures adjacent to the site of venous connection to the right atrium (RA).
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Ventricles
Normal ventricles consist of three components: inlet, apex, and outlet. The cornerstone for morphologic identification of the two ventricles is their inlet component, which includes the inlet (atrioventricular valve) and its tension apparatus. The latter consists of the chordae tendinae, which prevent the valve from inverting, and the papillary muscles, which are attached to the chordae tendinae and cause tension that prevents the valve from prolapsing into the atrium when the valve is closed. The inlet portion of the morphologic right ventricle is completely different from that of the morphologic left ventricle. Because the atrioventricular valve is connected to the corresponding ventricle, identification of the tricuspid and mitral valves is key for determining the ventricular structure. First, the hingepoint of the tricuspid valve is more apically positioned than that of the mitral valve; second, the septal leaflet of the tricuspid valve is extensive, and its tethering to the septum is an anatomic landmark of the valve.
The second landmark for determining morphologic right- or left-sidedness of ventricles is their outlet portion. The outlet of the morphologic right ventricle is a saddle-shaped supraventricular muscular crest that is located between the pulmonary valve and the tricuspid valve. There is no conical musculature between the aortic and mitral valves; instead, complete continuity of the fibrous tissue is seen (Fig 1b).
The ventricular wall thickness and the appearance of trabeculae are not useful for defining the morphologic left- versus right-sidedness of ventricles in the clinical setting. The left ventricle is demarcated by fine trabeculae and by two large papillary muscles that arise from the free wall and that are situated in the anterolateral and posteromedial positions, respectively. In the right ventricle, the muscular trabeculae are coarse and tend to parallel the right ventricular inflow and outflow tracts. The papillary muscles are relatively small and arise from both the septal and free wall surfaces. Papillary muscles that arise from the septal surface are unique to the morphologic right ventricle. Another characteristic feature of the right ventricle is the moderator band, a prominent muscle bundle that crosses from the septomarginal trabecula to the anterior papillary muscle and then to the parietal wall (Fig 1c).
Great Arteries
The great arteries are distinguished by their branching pattern rather than by the arterial valve, which is indistinguishable. Connection to the morphologic right or left ventricle cannot be used to define the great arteries. In most patients, the aortic sinuses give rise to the coronary arteries. Normally, the ascending aorta arises from the left ventricle and extends to the aortic arch, which is usually on the left side and gives rise to the brachiocephalic trunk, the left common carotid artery, and the left subclavian artery. The distal part of the aortic arch, which is called the aortic isthmus and which continues as the descending aorta, gives rise to the intercostal arteries and bronchial arteries (Fig 1d).
The main pulmonary artery passes from an anterior position toward the left posterior aspect of the aorta and subdivides into the left and right pulmonary arteries. The left pulmonary artery courses in a more posterior direction, while the right pulmonary artery passes behind the ascending aorta and superior vena cava (Fig 1e).
The bronchial branching pattern is helpful for defining the right- or left-sidedness of pulmonary structures. However, the anatomic relationship between the upper lobe bronchus and the branch pulmonary artery is the only characteristic feature defining the morphologic left- or right-sidedness of pulmonary structures (Fig 1f ). When the pulmonary structures are in the normal position (situs solitus), the right upper lobe bronchus is superior and posterior to the descending branch of the right pulmonary artery (epiarterial bronchus), while the left upper pulmonary artery courses posterior to the left upper bronchus and over the left upper lobe bronchus (hyparterial bronchus).
Great Veins
The great veins are identified by the organs that they drain. Three systemic veins are connected to the heart: the superior and inferior venae cavae and the coronary sinus (Fig 1g, 1h). In most people, these three veins join the right atrium within the confines of the sinus venosus, which is bounded by the atrial septum and the crista terminalis.
The four pulmonary veins normally are connected to the left atrium in a different corner of the posterior atrial wall. The right upper- and middle-lobe veins join to form the right superior pulmonary vein, while the left superior pulmonary vein receives blood from the left upper lobe. The left and right inferior lobes drain blood into the left and right inferior pulmonary veins, respectively.
Normal Connections
Three types of connectionsvenoatrial, atrioventricular, and ventriculoarterialmust be described. In the setting of concordant (normal) atrioventricular connection, the morphologic right atrium is connected to the morphologic right ventricle via the tricuspid valve, and the morphologic left atrium is connected to the morphologic left ventricle via the mitral valve. In the setting of concordant (normal) ventriculoarterial connection, the morphologic right ventricle is connected to the pulmonary artery, and the morphologic left ventricle is connected to the aorta.
In the presence of discordant connection, the atria and ventricles or the ventricles and arteries are not connected to the corresponding chambers. Atrioventricular concordance and ventriculoarterial discordance occur together in complete transposition of the great arteries. Atrioventricular and ventriculoarterial discordance, or double discordance, occurs in congenitally corrected transposition of the great arteries.
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Extracardiac Abnormalities
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Aortic Coarctation
Coarctation of the aorta typically consists of a diaphragmlike ridge that extends into the aortic lumen just distal to the left subclavian artery. The condition results in upper-body arterial hypertension and often is associated with a bicuspid aortic valve (familial aortic ectasia syndrome). Most adults with aortic coarctation are asymptomatic because chronic luminal narrowing of the aorta provokes the development of collateral vessels (eg, collateral epigastric, intercostal, thoracoacromial, vertebral, and anterior spinal arteries) to allow blood to flow from high-pressure to low-pressure areas (Fig 2) (32). CT is an effective and rapid imaging modality for the morphologic assessment of vessels, determination of the degree of stenosis, and visualization of collateral vessels (32). In addition, CT is a valuable tool when considering different therapeutic strategies (balloon catheterization and stent implantation vs surgery) in patients with severe aortic coarctation. However, CT is less useful than MR imaging in patients with mild stenosis, because of the lack of hemodynamic information provided by CT (33). On the other hand, CT is superior to MR imaging for postinterventional or postsurgical follow-up, because of the magnetic susceptibility artifacts produced by metallic stents and metallic clips at MR imaging.

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Figure 2a. Coarctation of the aorta at nongated CT in a 25-year-old man with atypical chest pain. (a) Thick-section oblique sagittal MIP image shows a high-grade aortic coarctation (arrow). AoA = aortic arch, dA = descending aorta, PT = pulmonary trunk. (b) Thin-section volume-rendered image, obtained with reconstruction in an oblique left-posterior plane by using the cut-plane mode, demonstrates narrowing of the aortic isthmus (small arrow) and extensive collateral intercostal and nuchal arteries (large arrow).
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Figure 2b. Coarctation of the aorta at nongated CT in a 25-year-old man with atypical chest pain. (a) Thick-section oblique sagittal MIP image shows a high-grade aortic coarctation (arrow). AoA = aortic arch, dA = descending aorta, PT = pulmonary trunk. (b) Thin-section volume-rendered image, obtained with reconstruction in an oblique left-posterior plane by using the cut-plane mode, demonstrates narrowing of the aortic isthmus (small arrow) and extensive collateral intercostal and nuchal arteries (large arrow).
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Anomalous Pulmonary Venous Connection
Total anomalous pulmonary venous connection is characterized by the connection of all the pulmonary veins to the right atrium either directly or indirectly via the superior or the inferior vena cava; the pulmonary veins may form a confluence behind the left atrium (34). Depending on the site of connection with the right atrium or systemic veins, total anomalous pulmonary venous connection is described as supracardiac, cardiac, infracardiac, or mixed (3,17). In partial anomalous pulmonary venous connection, one or more (but not all) pulmonary veins are connected to the vena cava or right atrium. The anatomic variations of partial anomalous pulmonary venous connection are manifold. Anomalous connection of the right pulmonary vein or veins to the inferior vena cava, often seen in association with hypoplasia of the right lung and anomalous systemic arterial supply through aortopulmonary collateral vessels, is called scimitar syndrome (Fig 3) (35,36). Abnormal connection of the right upper pulmonary vein to the superior vena cava occurs frequently in the presence of a sinus venosus defect (37); in such cases, the anomalous connection occurs at a slightly higher level than it does in the absence of an interatrial communication (Fig 4). If echocardiography performed for surgical planning fails to depict the pulmonary venous connection, CT may complete the visualization of pulmonary venous connections to the atria and may provide useful information about the lung parenchyma.

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Figure 3a. Scimitar syndrome at nongated CT performed for preoperative evaluation of pulmonary structures and lung parenchyma in a 16-year-old girl. Thick-section coronal MIP image (a) and thick-section axial MIP image (b) with a slab thickness of 10 mm show an anomalous connection of the right lower pulmonary vein (*) to the inferior vena cava (IVC). Hypoplasia of the right lung also is depicted. lPA = left pulmonary artery, rPA = right pulmonary artery.
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Figure 3b. Scimitar syndrome at nongated CT performed for preoperative evaluation of pulmonary structures and lung parenchyma in a 16-year-old girl. Thick-section coronal MIP image (a) and thick-section axial MIP image (b) with a slab thickness of 10 mm show an anomalous connection of the right lower pulmonary vein (*) to the inferior vena cava (IVC). Hypoplasia of the right lung also is depicted. lPA = left pulmonary artery, rPA = right pulmonary artery.
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Figure 4. Partial anomalous pulmonary venous connection at ECG-gated CT performed for preoperative evaluation of coronary artery anomalies in a 37-year-old woman. Thin-section axial CT scan shows an anomalous connection of the superior right pulmonary vein (rPV) (arrow) to the right atrium via the superior vena cava (SVC). The origin and course of the coronary arteries (not shown) were normal. lPV = left pulmonary vein, AV = aortic valve.
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Patent Ductus Arteriosus
The ductus arteriosus in the fetus connects the proximal left pulmonary artery with the proximal part of the descending aorta just distal to the left subclavian artery. If the ductus arteriosus does not close spontaneously after birth, there is a continuous flow from the descending aorta to the pulmonary arteries (38). Echocardiography usually is considered the diagnostic method of choice to diagnose a patent ductus arteriosus. CT plays a minor role in diagnostic imaging of patent ductus arteriosus, but it may be more helpful for assessing the size and shape of the patent ductus arteriosus and for identifying ductal calcifications during treatment planning (Fig 5) (39,40). Accurate measurement of the size of the duct is necessary to determine whether transcatheter closure may be performed; the morphologic characteristics of the duct and the presence and degree of ductal calcifications are important factors when surgery is considered (39,40). Even in young infants, ductal calcifications are more the norm than the exception.

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Figure 5. Patent ductus arteriosus at non-gated CT performed for follow-up assessment in a 36-year-old woman. Thin-section oblique sagittal image demonstrates a large patent ductus arteriosus (arrowhead) that connects the roof of the common pulmonary artery (CPA) with the descending aorta (dA). AoA = aortic arch.
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Intracardiac Communications
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Atrial Septal Defect
Atrial septal defect accounts for about one-third of cases of congenital heart disease detected in adults (38). Ostium secundum atrial septal defects are the most common type of interatrial communication located within the oval fossa, and ostium primum atrial septal defects are the next most common type (38). The ostium primum defect, which is part of an atrioventricular septal defect, is roofed superiorly by the inferior border of the oval fossa and inferiorly by the superior and inferior bridging leaflets. This type of atrial septal defect is manifested with a defect (cleft) of the anterior mitral valve leaflet. The least common type of interatrial communication is a sinus venosus defect, which is located at the mouth of either the superior or the inferior vena cava (Fig 6). In patients with a superior sinus venosus defect, there is frequently an abnormal connection of one or all of the right pulmonary veins (37).

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Figure 6. Superior sinus venosus defect at non-gated CT performed for preoperative evaluation in a 38-year-old woman. Thin-section axial reformatted image demonstrates interatrial communication between the right atrium (RA) and left atrium (LA) through a large defect in the mouth of the superior vena cava (SVC), at the level of the upper portion of the atrial septum (arrow).
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Echocardiography is the method of choice for diagnosing atrial septal defects. Quantification of a shunt is not feasible with CT. Hemodynamically less severe interatrial communications may be incidental findings at nongated thoracic CT, but small communications are usually missed unless ECG-gated scanning is performed.
Ventricular Septal Defect
Ventricular septal defect is the most common congenital heart condition in infants and children (38). Seventy percent of such defects are located in the membranous portion of the interventricular septum (Fig 7); 20%, in the muscular portion of the septum; 5%, just below the aortic valve; and 5%, near the junction of the mitral and tricuspid valves, causing atrioventricular canal defects (41). Patients who have a large defect and who survive until adulthood usually have pulmonary hypertension with subsequent right ventricular hypertrophy and enlargement (38). Ventricular septal defects are frequently associated with complex congenital heart disease. The role of CT in the evaluation of ventricular septal defects, as in that of interatrial communications, is limited to the depiction of morphologic features.

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Figure 7. Ventricular septal defect at ECG-gated CT performed in a 20-year-old man to monitor atrial and ventricular dimensions and function after a Fontan procedure for tetralogy of Fallot in early childhood. Thin-section reformatted image along the short axis of the heart shows a small ventricular septal defect (arrow) that leads to a communication between the left ventricle (LV) and the hypoplastic right ventricle (RV). RA = right atrium, RCA = right coronary artery.
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Conotruncal Defects
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Tetralogy of Fallot
This condition is characterized by a subpulmonary infundibular stenosis (which commonly coexists with an obstruction at another level), large ventricular septal defect, overriding of the aorta, and right ventricular hypertrophy (42). Several other abnormalities may occur in association with tetralogy of Fallot, including a right aortic arch in 25% of cases, an atrial septal defect in 10% of cases (so-called pentalogy of Fallot) (42), and coronary artery anomalies in another 10% of cases (43). In addition, hypoplasia of the pulmonary valve and the main pulmonary artery is common. Because the surgical repair is usually performed during early childhood, the role of CT in diagnosing tetralogy of Fallot is minimal. In postsurgical evaluation, the main purpose of CT is to visualize extracardiac complications, to depict the morphologic characteristics of the main pulmonary artery and its branches (to identify any obstruction, distortion after previous palliative shunt creation, or aneurysm), and to detect any right ventricular enlargement due to chronic volume overload in the presence of severe pulmonary regurgitation. Postsurgical evaluation is usually performed without ECG gating and with echocardiographic monitoring of ventricular function; however, ECG-gated CT should be used for the postoperative evaluation of tetralogy of Fallot if there is concern about associated coronary artery anomalies. Left and right ventricular parameters can be measured in the same study.
Common Arterial Trunk
In this condition, a single large artery (arterial trunk) originates from the base of the heart with a single semilunar valve (truncal valve) (3,17). There are different types of common arterial trunks (44 46). Either a short main pulmonary trunk or both the right and the left pulmonary arteries may arise from the arterial trunk. A subtruncal ventricular septal defect is always present. About one-third of patients with a common arterial trunk also have a right-sided aortic arch. Surgical repair consists of (a) disconnection of the pulmonary trunk from the ascending aorta with patch closure and (b) restoration of continuity between the right ventricle and pulmonary vascular bed with graft implantation (Fig 8).

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Figure 8a. Childhood surgical repair of a common arterial trunk at ECG-gated CT performed in a 32-year-old woman because of suspicion of a coronary artery anomaly. (a) Thin-section axial CT scan shows a patch (arrow) between the common arterial trunk (CAT) and the right ventricle (RV). RA = right atrium. (b) Thin-section axial CT scan demonstrates a graft implanted from the right ventricle to the pulmonary trunk. The connection to the ascending aorta (aA) was closed with a patch (arrow). The origin and course of the coronary arteries (not shown) were normal. dA = descending aorta, rPA = right pulmonary artery.
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Figure 8b. Childhood surgical repair of a common arterial trunk at ECG-gated CT performed in a 32-year-old woman because of suspicion of a coronary artery anomaly. (a) Thin-section axial CT scan shows a patch (arrow) between the common arterial trunk (CAT) and the right ventricle (RV). RA = right atrium. (b) Thin-section axial CT scan demonstrates a graft implanted from the right ventricle to the pulmonary trunk. The connection to the ascending aorta (aA) was closed with a patch (arrow). The origin and course of the coronary arteries (not shown) were normal. dA = descending aorta, rPA = right pulmonary artery.
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Abnormal Connections
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Univentricular Heart
This condition is characterized by a single atrioventricular connection, with both atria emptying into a single common ventricle (double inlet) that is morphologically predominantly left, predominantly right, or indeterminate (47). There is a subpulmonary or subaortic outlet chamber or a rudimentary and incomplete ventricle that lacks an inlet portion. The terminology is subject to debate: A ventricular chamber that has no connection to an atrioventricular valve is usually called the outlet chamber because a ventricle is defined by an atrioventricular connection (Fig 9). A univentricular heart may be observed in association with other cardiac abnormalities and with any arrangement of the great arteries.

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Figure 9a. Double inlet left ventricle with d-transposition of the great arteries, observed at ECG-gated CT performed to supplement postoperative echocardiography in a 30-year-old man after surgical banding of the common pulmonary artery. (a) Thin-section reformatted image along the long axis of the heart shows connection of the left atrium (LA) and right atrium (RA) through a left-sided valve (LSV) and a right-sided valve (RSV), respectively, to a dominant ventricle (DV, morphologic left ventricle). (b) Thin-section oblique sagittal image demonstrates a subaortic outlet chamber (SOC) connected via a bulboventricular foramen (*) to the subpulmonary ventricle (the dominant ventricle in a). There is no atrioventricular connection to the subaortic outlet chamber. Banding of the common pulmonary artery was performed to protect the lung from high systemic blood flow and pressure. The great arteries are in parallel position (d-transposition): The pulmonary artery arises from the morphologic left single ventricle, and the aorta arises from the subaortic outlet chamber. AV = aortic valve, PV = pulmonary valve.
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Figure 9b. Double inlet left ventricle with d-transposition of the great arteries, observed at ECG-gated CT performed to supplement postoperative echocardiography in a 30-year-old man after surgical banding of the common pulmonary artery. (a) Thin-section reformatted image along the long axis of the heart shows connection of the left atrium (LA) and right atrium (RA) through a left-sided valve (LSV) and a right-sided valve (RSV), respectively, to a dominant ventricle (DV, morphologic left ventricle). (b) Thin-section oblique sagittal image demonstrates a subaortic outlet chamber (SOC) connected via a bulboventricular foramen (*) to the subpulmonary ventricle (the dominant ventricle in a). There is no atrioventricular connection to the subaortic outlet chamber. Banding of the common pulmonary artery was performed to protect the lung from high systemic blood flow and pressure. The great arteries are in parallel position (d-transposition): The pulmonary artery arises from the morphologic left single ventricle, and the aorta arises from the subaortic outlet chamber. AV = aortic valve, PV = pulmonary valve.
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Transposition of the Great Arteries
Complete transposition of the great arteries is one of the most common types of cyanotic congenital heart disease. It is defined by concordant atrioventricular and discordant ventriculoarterial connections (48). The aorta arises in an anterior position from the morphologic right ventricle, and the main pulmonary artery arises from the morphologic left ventricle; as a result, there is a complete separation of the pulmonary from the systemic circulation (Fig 10). The pulmonary valve is in fibrous continuity with the mitral valve. In about two-thirds of patients, no other cardiac defects are present, and the patent ductus arteriosus and the patent foramen ovale ensure communication between the two circulatory pathways and survival during the first days of life (49). The one-third of patients with associated defects that allow intracardiac mixing (eg, atrial septal defect, ventricular septal defect) are less critically ill but are at risk for ventricular failure due to volume overload from a left-to-right shunt (49). Today, surgical repair is usually performed by using the arterial switch procedure, which has replaced both the Senning and the Mustad atrial switch operations (49). However, most adults with transposition of the great arteries have undergone the atrial switch procedure, in which an atrial baffle redirects systemic venous blood to the anatomic left pulmonary ventricle and pulmonary venous blood to the anatomic right systemic ventricle, with a resultant functional atrial switch. The Mustad operation usually is performed with pericardial tissue or a tissue graft used for the baffle, whereas in the Senning procedure the atrial septum is reconstructed to form the baffle (50). In the arterial switch operation, the aorta and the pulmonary artery are transected above the valves and moved to the correct circulatory position. The coronary arteries are excised from the right side with a buttonlike margin of tissue around each artery and are implanted just above the valve on the left side of the heart; the areas from which the coronary arteries were excised then are patched with pericardium.

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Figure 10a. Transposition of the great arteries at ECG-gated CT after an arterial switch operation and reconstruction of the atrial septum in a 17-year-old girl with a previous atrial switch procedure. CT was performed to exclude stenosis of the reimplanted coronary arteries. (a) Thin-section axial CT scan shows the ascending aorta (aA) after its transfer by means of the LeCompte maneuver from an anterolateral position (*) to a position posterior to the pulmonary trunk (PT). As is typical after this procedure, the ascending aorta appears to be embraced by the left pulmonary artery (lPA) and right pulmonary artery (rPA). The dilated right pulmonary artery compresses the superior vena cava (SVC). A stent was implanted into the superior vena cava to relieve the obstruction of blood flow. dA = descending aorta. (b) Thin-section oblique coronal image shows the former aortic root in the anterior position (*) and the pulmonary trunk (PT) embracing the repositioned ascending aorta (aA). IVC = inferior vena cava, LA = left atrium, RA = right atrium. (c) Thin-section oblique sagittal image shows the postsurgical location of the ascending aorta (aA) posterior to the pulmonary trunk (PT), which is dilated and compresses the aorta. RV = right ventricle.
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Figure 10b. Transposition of the great arteries at ECG-gated CT after an arterial switch operation and reconstruction of the atrial septum in a 17-year-old girl with a previous atrial switch procedure. CT was performed to exclude stenosis of the reimplanted coronary arteries. (a) Thin-section axial CT scan shows the ascending aorta (aA) after its transfer by means of the LeCompte maneuver from an anterolateral position (*) to a position posterior to the pulmonary trunk (PT). As is typical after this procedure, the ascending aorta appears to be embraced by the left pulmonary artery (lPA) and right pulmonary artery (rPA). The dilated right pulmonary artery compresses the superior vena cava (SVC). A stent was implanted into the superior vena cava to relieve the obstruction of blood flow. dA = descending aorta. (b) Thin-section oblique coronal image shows the former aortic root in the anterior position (*) and the pulmonary trunk (PT) embracing the repositioned ascending aorta (aA). IVC = inferior vena cava, LA = left atrium, RA = right atrium. (c) Thin-section oblique sagittal image shows the postsurgical location of the ascending aorta (aA) posterior to the pulmonary trunk (PT), which is dilated and compresses the aorta. RV = right ventricle.
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Figure 10c. Transposition of the great arteries at ECG-gated CT after an arterial switch operation and reconstruction of the atrial septum in a 17-year-old girl with a previous atrial switch procedure. CT was performed to exclude stenosis of the reimplanted coronary arteries. (a) Thin-section axial CT scan shows the ascending aorta (aA) after its transfer by means of the LeCompte maneuver from an anterolateral position (*) to a position posterior to the pulmonary trunk (PT). As is typical after this procedure, the ascending aorta appears to be embraced by the left pulmonary artery (lPA) and right pulmonary artery (rPA). The dilated right pulmonary artery compresses the superior vena cava (SVC). A stent was implanted into the superior vena cava to relieve the obstruction of blood flow. dA = descending aorta. (b) Thin-section oblique coronal image shows the former aortic root in the anterior position (*) and the pulmonary trunk (PT) embracing the repositioned ascending aorta (aA). IVC = inferior vena cava, LA = left atrium, RA = right atrium. (c) Thin-section oblique sagittal image shows the postsurgical location of the ascending aorta (aA) posterior to the pulmonary trunk (PT), which is dilated and compresses the aorta. RV = right ventricle.
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Postoperative evaluation after an atrial switch procedure may be difficult with echocardiography because of the retrosternal position of the pulmonary trunk and pulmonary arteries. Dilatation of the great arteries and pulmonary artery stenosis are common in these patients, and nongated CT may be helpful in the evaluation of these complications. In addition, ECG-gated CT may depict stenoses of the reattached coronary arteries after an arterial switch operation. ECG-gated CT also may be used for follow-up monitoring of ventricular function if the use of echocardiography is limited by a poor acoustic window.
Congenitally Corrected Transposition of the Great Arteries
In this condition, there is both an atrioventricular and a ventriculoarterial discordant connection, or double discordance (51). The right atrium is connected via the mitral valve to the morphologic left ventricle and then to the pulmonary artery (Fig 11). In patients with congenitally corrected transposition, the great arteries are parallel (side-by-side arrangement). In the absence of associated anomalies (eg, ventricular septal defect, pulmonary outflow tract obstruction), congenitally corrected transposition of the great arteries is often asymptomatic until adulthood. The diagnosis may be established with echocardiography or, when echocardiographic findings are in doubt, with CT. The measurement of ventricular functional parameters at ECG-gated CT is helpful in the follow-up of these patients.

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Figure 11a. Congenitally corrected transposition of the great arteries at nongated CT performed to exclude Kartagener syndrome in a 36-year-old man with known dextrocardia and chronic dyspnea. (a) Thin-section axial CT scan shows the ascending aorta (aA) in a position anterior to and left of the pulmonary artery (PA). dA = descending aorta. (b) Thin-section axial CT scan at the level of the ventricle shows that the pulmonary artery arises from the left ventricle (LV) and the aorta arises from the right ventricle (RV). The right atrium, which received flow from the systemic veins, was connected to the morphologic left ventricle (not shown). Thus, the findings included atrioventricular and ventriculoarterial discordant connections. Bronchiectasis indicative of Kartagener syndrome was not found.
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Figure 11b. Congenitally corrected transposition of the great arteries at nongated CT performed to exclude Kartagener syndrome in a 36-year-old man with known dextrocardia and chronic dyspnea. (a) Thin-section axial CT scan shows the ascending aorta (aA) in a position anterior to and left of the pulmonary artery (PA). dA = descending aorta. (b) Thin-section axial CT scan at the level of the ventricle shows that the pulmonary artery arises from the left ventricle (LV) and the aorta arises from the right ventricle (RV). The right atrium, which received flow from the systemic veins, was connected to the morphologic left ventricle (not shown). Thus, the findings included atrioventricular and ventriculoarterial discordant connections. Bronchiectasis indicative of Kartagener syndrome was not found.
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Double Outlet Ventricle
Double outlet ventricle encompasses a wide spectrum of congenital heart abnormalities in which both great arteries arise predominantly from either the morphologic right or the morphologic left ventricle (Fig 12) (52). The "50% rule" usually is applied in determining a ventriculoarterial connection, and an artery is considered to be connected to a ventricle when more than half of its semilunar valve is connected to that ventricle. In more than 50% of patients with a double outlet ventricle, both the ascending aorta and the pulmonary trunk arise from the morphologic right ventricle, a condition denoted by the term double outlet right ventricle (53). In patients with double outlet right ventricle, numerous anatomic and physiologic variations may occur with regard to the location of the ventricular septal defect (subaortic, subpulmonary) and the presence or absence of right ventricular outflow tract obstruction. The identification of anatomic and physiologic variations has an important influence on the surgical strategy (54). ECG-gated CT might be performed for the initial evaluation of these patients, to better define the position of the ventricular septal defect. However, follow-up evaluation usually is performed with nongated CT.

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Figure 12a. Double outlet right ventricle with d-transposition of the great arteries at ECG-gated CT performed for follow-up evaluation of complex anatomy in a 17-year-old girl after a Damus-Kaye-Stansel procedure, patch closure of an atrial septal defect and tricuspid valve, and a Fontan-Kreutzer procedure. (a) Thin-section oblique coronal image shows the connections of the systemic veins to the dilated right atrium (RA), which was surgically anastomosed to the left pulmonary artery (lPA) and right pulmonary artery (rPA). The tricuspid valve was closed with a patch. In the postsurgical circulation, blood flows directly from the systemic veins to the pulmonary arteries, without a subpulmonary ventricle (Fontan-Kreutzer procedure). The pulmonary veins are connected to the left atrium, which is connected to the hypoplastic left ventricle. The morphologic left ventricle is connected to the morphologic right ventricle (RV) via a ventricular septal defect. (b) Thin-section oblique sagittal image demonstrates connection of the right ventricle (RV) to the left ventricle (LV) via a ventricular septal defect (*). (c) Thin-section oblique sagittal image shows a hypoplastic morphologic left ventricle (LV) and a normal-sized right ventricle (RV). Both the ascending aorta (aA) and the pulmonary trunk (PT) arise from the morphologic right ventricle, with the pulmonary trunk overriding the ventricular septal defect. The pulmonary trunk was surgically connected to the ascending aorta with the Damus-Kaye-Stansel procedure. LA = left atrium.
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Figure 12b. Double outlet right ventricle with d-transposition of the great arteries at ECG-gated CT performed for follow-up evaluation of complex anatomy in a 17-year-old girl after a Damus-Kaye-Stansel procedure, patch closure of an atrial septal defect and tricuspid valve, and a Fontan-Kreutzer procedure. (a) Thin-section oblique coronal image shows the connections of the systemic veins to the dilated right atrium (RA), which was surgically anastomosed to the left pulmonary artery (lPA) and right pulmonary artery (rPA). The tricuspid valve was closed with a patch. In the postsurgical circulation, blood flows directly from the systemic veins to the pulmonary arteries, without a subpulmonary ventricle (Fontan-Kreutzer procedure). The pulmonary veins are connected to the left atrium, which is connected to the hypoplastic left ventricle. The morphologic left ventricle is connected to the morphologic right ventricle (RV) via a ventricular septal defect. (b) Thin-section oblique sagittal image demonstrates connection of the right ventricle (RV) to the left ventricle (LV) via a ventricular septal defect (*). (c) Thin-section oblique sagittal image shows a hypoplastic morphologic left ventricle (LV) and a normal-sized right ventricle (RV). Both the ascending aorta (aA) and the pulmonary trunk (PT) arise from the morphologic right ventricle, with the pulmonary trunk overriding the ventricular septal defect. The pulmonary trunk was surgically connected to the ascending aorta with the Damus-Kaye-Stansel procedure. LA = left atrium.
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Figure 12c. Double outlet right ventricle with d-transposition of the great arteries at ECG-gated CT performed for follow-up evaluation of complex anatomy in a 17-year-old girl after a Damus-Kaye-Stansel procedure, patch closure of an atrial septal defect and tricuspid valve, and a Fontan-Kreutzer procedure. (a) Thin-section oblique coronal image shows the connections of the systemic veins to the dilated right atrium (RA), which was surgically anastomosed to the left pulmonary artery (lPA) and right pulmonary artery (rPA). The tricuspid valve was closed with a patch. In the postsurgical circulation, blood flows directly from the systemic veins to the pulmonary arteries, without a subpulmonary ventricle (Fontan-Kreutzer procedure). The pulmonary veins are connected to the left atrium, which is connected to the hypoplastic left ventricle. The morphologic left ventricle is connected to the morphologic right ventricle (RV) via a ventricular septal defect. (b) Thin-section oblique sagittal image demonstrates connection of the right ventricle (RV) to the left ventricle (LV) via a ventricular septal defect (*). (c) Thin-section oblique sagittal image shows a hypoplastic morphologic left ventricle (LV) and a normal-sized right ventricle (RV). Both the ascending aorta (aA) and the pulmonary trunk (PT) arise from the morphologic right ventricle, with the pulmonary trunk overriding the ventricular septal defect. The pulmonary trunk was surgically connected to the ascending aorta with the Damus-Kaye-Stansel procedure. LA = left atrium.
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Isomerism
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The term isomerism (ie, bilateral symmetry) describes paired, mirror-image sets of normally single or nonidentical organ systems. Although atrial arrangement is characterized by the left or right morphologic characteristics of the atrial appendages, accurate identification of morphologic left- or right-sidedness may be difficult (55). In patients with right isomerism, there is bilateral right-sidedness; hence, the anomalies include bilateral morphologic right atrial appendages, bilateral bronchi (trilobed right-sided lungs), asplenia syndrome, and bilateral superior venae cavae. Conversely, left atrial isomerism describes bilateral left-sidedness and includes bilateral morphologic left atrial appendages, bilateral left bronchi (bilateral bilobed lungs with hyparterial bronchus on both sides), polysplenia, and an interrupted inferior vena cava with azygos continuation (Fig 13). Although these criteria are helpful for determining sidedness, there is considerable variation within each syndrome, and features of one syndrome also may be found in another (56).

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Figure 13a. Left pulmonary isomerism at ECG-gated cardiac CT and nongated chest and abdominal CT performed for suspicion of situs inversus in a 38-year-old man after unknown surgical procedures in early childhood. (a) Thin-section reformatted image along the long axis of the heart reveals morphologic left atria on both sides, with ventricular inversion: a morphologic left atrium with right-sided pulmonary venous atrium (LA*); a morphologic left atrium with right-sided atrial appendage (LAA*); a morphologic left atrium and left-sided systemic venous atrium (LA); a morphologic left atrium and right-sided left ventricle (LV); and a morphologic right atrium and left-sided right ventricle (RV). The left-sided systemic venous atrium is connected via the tricuspid valve to the left-sided right ventricle and the pulmonary artery; the right-sided pulmonary venous atrium is connected via the mitral valve to the right-sided left ventricle and the aorta. (b) Thick-section oblique coronal MIP image with a slab thickness of 10 mm shows direct connection of the hepatic veins (arrows) to the left-sided systemic venous atrium (LA). LA* = morphologic left atrium with right-sided pulmonary venous atrium, LV = left ventricle, RV = right ventricle. (c) Thin-section coronal reformatted image demonstrates an abnormal bronchial branching pattern, with the left pulmonary artery (lPA) and right pulmonary artery (rPA) coursing over the upper lobe bronchus on the left and right sides, respectively (hyparterial bronchus). AoA = aortic arch, AV = azygos vein, dA = descending aorta, LB = left-sided (morphologic left) bronchus, RB = right-sided (morphologic left) bronchus, SVC = left-sided superior vena cava. (d) Thin-section axial CT scan through the upper abdomen shows a large, predominantly midline liver and right-sided polysplenia (*).
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Figure 13b. Left pulmonary isomerism at ECG-gated cardiac CT and nongated chest and abdominal CT performed for suspicion of situs inversus in a 38-year-old man after unknown surgical procedures in early childhood. (a) Thin-section reformatted image along the long axis of the heart reveals morphologic left atria on both sides, with ventricular inversion: a morphologic left atrium with right-sided pulmonary venous atrium (LA*); a morphologic left atrium with right-sided atrial appendage (LAA*); a morphologic left atrium and left-sided systemic venous atrium (LA); a morphologic left atrium and right-sided left ventricle (LV); and a morphologic right atrium and left-sided right ventricle (RV). The left-sided systemic venous atrium is connected via the tricuspid valve to the left-sided right ventricle and the pulmonary artery; the right-sided pulmonary venous atrium is connected via the mitral valve to the right-sided left ventricle and the aorta. (b) Thick-section oblique coronal MIP image with a slab thickness of 10 mm shows direct connection of the hepatic veins (arrows) to the left-sided systemic venous atrium (LA). LA* = morphologic left atrium with right-sided pulmonary venous atrium, LV = left ventricle, RV = right ventricle. (c) Thin-section coronal reformatted image demonstrates an abnormal bronchial branching pattern, with the left pulmonary artery (lPA) and right pulmonary artery (rPA) coursing over the upper lobe bronchus on the left and right sides, respectively (hyparterial bronchus). AoA = aortic arch, AV = azygos vein, dA = descending aorta, LB = left-sided (morphologic left) bronchus, RB = right-sided (morphologic left) bronchus, SVC = left-sided superior vena cava. (d) Thin-section axial CT scan through the upper abdomen shows a large, predominantly midline liver and right-sided polysplenia (*).
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Figure 13c. Left pulmonary isomerism at ECG-gated cardiac CT and nongated chest and abdominal CT performed for suspicion of situs inversus in a 38-year-old man after unknown surgical procedures in early childhood. (a) Thin-section reformatted image along the long axis of the heart reveals morphologic left atria on both sides, with ventricular inversion: a morphologic left atrium with right-sided pulmonary venous atrium (LA*); a morphologic left atrium with right-sided atrial appendage (LAA*); a morphologic left atrium and left-sided systemic venous atrium (LA); a morphologic left atrium and right-sided left ventricle (LV); and a morphologic right atrium and left-sided right ventricle (RV). The left-sided systemic venous atrium is connected via the tricuspid valve to the left-sided right ventricle and the pulmonary artery; the right-sided pulmonary venous atrium is connected via the mitral valve to the right-sided left ventricle and the aorta. (b) Thick-section oblique coronal MIP image with a slab thickness of 10 mm shows direct connection of the hepatic veins (arrows) to the left-sided systemic venous atrium (LA). LA* = morphologic left atrium with right-sided pulmonary venous atrium, LV = left ventricle, RV = right ventricle. (c) Thin-section coronal reformatted image demonstrates an abnormal bronchial branching pattern, with the left pulmonary artery (lPA) and right pulmonary artery (rPA) coursing over the upper lobe bronchus on the left and right sides, respectively (hyparterial bronchus). AoA = aortic arch, AV = azygos vein, dA = descending aorta, LB = left-sided (morphologic left) bronchus, RB = right-sided (morphologic left) bronchus, SVC = left-sided superior vena cava. (d) Thin-section axial CT scan through the upper abdomen shows a large, predominantly midline liver and right-sided polysplenia (*).
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Figure 13d. Left pulmonary isomerism at ECG-gated cardiac CT and nongated chest and abdominal CT performed for suspicion of situs inversus in a 38-year-old man after unknown surgical procedures in early childhood. (a) Thin-section reformatted image along the long axis of the heart reveals morphologic left atria on both sides, with ventricular inversion: a morphologic left atrium with right-sided pulmonary venous atrium (LA*); a morphologic left atrium with right-sided atrial appendage (LAA*); a morphologic left atrium and left-sided systemic venous atrium (LA); a morphologic left atrium and right-sided left ventricle (LV); and a morphologic right atrium and left-sided right ventricle (RV). The left-sided systemic venous atrium is connected via the tricuspid valve to the left-sided right ventricle and the pulmonary artery; the right-sided pulmonary venous atrium is connected via the mitral valve to the right-sided left ventricle and the aorta. (b) Thick-section oblique coronal MIP image with a slab thickness of 10 mm shows direct connection of the hepatic veins (arrows) to the left-sided systemic venous atrium (LA). LA* = morphologic left atrium with right-sided pulmonary venous atrium, LV = left ventricle, RV = right ventricle. (c) Thin-section coronal reformatted image demonstrates an abnormal bronchial branching pattern, with the left pulmonary artery (lPA) and right pulmonary artery (rPA) coursing over the upper lobe bronchus on the left and right sides, respectively (hyparterial bronchus). AoA = aortic arch, AV = azygos vein, dA = descending aorta, LB = left-sided (morphologic left) bronchus, RB = right-sided (morphologic left) bronchus, SVC = left-sided superior vena cava. (d) Thin-section axial CT scan through the upper abdomen shows a large, predominantly midline liver and right-sided polysplenia (*).
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Conclusions
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The high spatial and temporal resolution provided by multidetector CT, combined with the short scanning times, enable the use of no sedation or only short-term sedation while evaluating patients with congenital heart disease. Consequently, CT has become a useful imaging modality for the pre- and postsurgical evaluation of a wide variety of cardiac defects in pediatric and adult patients.
Although echocardiography is the method of choice for diagnosing the vast majority of congenital cardiac abnormalities, CT plays an increasing complementary role by providing objective and accurate morphologic and functional information and is useful for detecting extracardiac abnormalities. When findings with other imaging modalities are equivocal, the use of CT may help decrease diagnostic error. However, non-gated CT cannot be used for functional assessment, and the benefit of obtaining functional information with ECG-gated CT must outweigh the increased radiation exposure to the patient, particularly the pediatric or young adult patient, especially with repeated CT examinations.
The reader of CT images must be familiar with the complex anatomy, morphology, and terminology of congenital heart disease, as well as with the interventional procedures used to correct congenital abnormalities. Thus, the use of CT is recommended in care centers with a multidisciplinary congenital heart disease team. Nonfamiliarity with the complexity of congenital heart diseases might lead to misinterpretation and mismanagement.
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Footnotes
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Abbreviations: ECG = electrocardiography, MIP = maximum intensity projection
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