DOI: 10.1148/rg.23si035501
(Radiographics. 2003;23:S147-S165.)
© RSNA, 2003
CT of Congenital Heart Disease: Normal Anatomy and Typical Pathologic Conditions1
Hyun Woo Goo, MD,
In-Sook Park, MD,
Jae Kon Ko, MD,
Yong Hwue Kim, MD,
Dong-Man Seo, MD,
Tae-Jin Yun, MD,
Jeong-Jun Park, MD and
Chong Hyun Yoon, MD
1 From the Departments of Radiology (H.W.G., C.H.Y.), Pediatric Cardiology (I.S.P., J.K.K., Y.H.K.), and Pediatric Cardiac Surgery (D.M.S., T.J.Y., J.J.P.), Asan Medical Center, University of Ulsan College of Medicine, 388–1 Pungnap-2 dong, Songpa-gu, 138–736 Seoul, Korea. Recipient of a Magna Cum Laude award for an education exhibit at the 2002 RSNA scientific assembly. Received January 23, 2003; revision requested March 11 and received March 18; accepted April 3. Address correspondence to H.W.G. (e-mail: hwgoo@amc.seoul.kr).
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Abstract
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Computed tomography (CT) plays an important supplementary role in the evaluation of patients with congenital heart disease (CHD). Fast multisection spiral CT can be used to obtain isotropic volume data, and high-quality two- and three-dimensional multiplanar reformatted images can be created to accurately and systematically delineate the normal and pathologic morphologic features of the cardiovascular system. CT may be technically challenging and demanding in uncooperative young children. However, it can be used to systematically evaluate the aorta, pulmonary artery, pulmonary vein, cardiac chambers and ventriculoarterial connection, relationship between the upper lobe bronchi and pulmonary arteries, coronary artery, valves, systemic veins (superior vena cava, inferior vena cava, hepatic veins), and visceral situs with a step-by-step approach. This approach may be helpful in understanding the anatomy of the cardiovascular system in CHD patients. CT has both advantages and disadvantages in evaluating patients with CHD. Nevertheless, it is useful in this setting, and radiologists who perform CT in young children with CHD should be familiar with the advantages and disadvantages of CT and with the normal anatomy and typical pathologic conditions in affected patients.
© RSNA, 2003
Index Terms: Heart, abnormalities, 50.14, 50.15, 50.16, 50.17, 50.18 • Heart, anatomy, 50.92 • Heart, CT, 50.1211 • Heart, diseases, 50.191
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Learning Objectives for Test 6
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- After reading this article and taking the test, the reader will be able to:
- Identify optimal CT techniques for evaluation of congenital heart disease.
- Describe the normal anatomy and typical pathologic conditions seen on reformatted images from CT in patients with congenital heart disease.
- Discuss the advantages and disadvantages of CT in the evaluation of congenital heart disease.
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Introduction
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Echocardiography and catheter cardioangiography are the primary cardiac imaging modalities, but both have weaknesses. Echocardiography is limited by a small field of view, an acoustic window, and operator dependence. Catheter cardioangiography is limited by the overlapping of adjacent vascular structures, difficulty in demonstrating systemic and pulmonary vascular systems simultaneously, catheter-related complications (especially in young children), and relatively high doses of ionizing radiation and iodinated contrast material. Computed tomography (CT) and magnetic resonance (MR) imaging have important roles in overcoming these limitations.
CT has been used in the morphologic evaluation of congenital heart disease (CHD) (1–24). For this purpose, electron-beam CT and single-section spiral CT have been used because of their fast image acquisition times and their capacity to obtain volume data. Cardiac imaging with CT and MR imaging always relies on technical developments because high temporal and spatial resolution is necessary for the satisfactory evaluation of CHD. In addition, multiplanar evaluation is essential because each vascular structure has its own axis—an axis that is different from the axes of the adjacent vascular structures. Recently introduced multisection spiral CT comes close to fulfilling all these requirements.
In this article, we discuss and illustrate the CT and image reformatting techniques used for young children with CHD, the normal anatomy and typical pathologic conditions (extracardiac abnormalities, cardiac abnormalities, connection problems) seen at CT in patients with CHD, and the advantages and disadvantages of CT in this setting.
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CT and Image Reformatting Techniques
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Patients who were not able to hold their breath were sedated with 50–75 mg/kg of orally administered chloral hydrate. Sedative drugs were injected intravenously when necessary. All CT examinations were performed with a four-section spiral CT scanner. CT data were obtained with the following parameters: 1.25-mm collimation, 3.75-mm/sec table feed, and 0.5-mm reconstruction interval. A weight-based low-dose CT protocol (120 kVp, 30–80 mA) was used. Recently, 80 kVp was recommended for contrast material–enhanced CT because the radiation dose can be further reduced without loss of image quality. Moreover, radiation dose in state-of-the-art multisection spiral CT can be reduced with tube current modulation. Faster table feed may also reduce radiation dose but decreases z-axis resolution. Scanning was performed from the thoracic inlet level to the L1–2 level. Nonionic contrast agent (2 mL/kg) was injected at different sites along peripheral venous routes. A leg vein was the preferred route, whereas an arm vein was used in patients who had undergone bidirectional cavopulmonary shunting or a Fontan procedure or when the leg vein was not accessible. Whenever the arm vein was used, contrast agent was mixed with an equal amount of normal saline solution and CT was performed in the caudocranial direction to decrease contrast agent–related artifacts and to achieve homogeneous contrast enhancement. The injection rate was adjusted so that the contrast agent could be injected during the entire scan. Scan delay was determined with an automatic bolus tracking system. Two round regions of interest were placed, one in the right atrium and the other in the right ventricle, because the minimum delay to the start of scanning was 5.5 seconds with our CT system. A threshold level of 70 HU was set for starting the scan. CT was performed during quiet breathing in patients who could not hold their breath. Electrocardiography- and respiration-gated techniques were not used. Electrocardiography-gated multisection spiral CT has recently become available and is helpful in evaluating the coronary artery. Among the steps necessary to produce diagnostically useful reformatted images, the most important is to obtain optimal-quality CT volume data. Therefore, a radiologist who performs CT for CHD should know how to optimize the CT techniques.
The CT volume data were transferred to a commercially available workstation (Advantage Windows 3.1 or 4.0; General Electric Medical Systems, Milwaukee, Wis). Various image reformatting techniques, including linear or curved planar reformatting, maximum intensity projection (MIP), minimum intensity projection, shaded surface display, and volume rendering (VR), were used depending on target structure and purpose. The plane of the reformatted image was adjusted to correspond to the long axis of the structure of interest. Curved planar reformation was used to evaluate curved structures such as the pulmonary artery system, MIP was used mainly for evaluation of the cardiovascular structures, and minimum intensity projection was used to evaluate the airway and lung parenchyma. For three-dimensional reformatting, shaded surface display was used to evaluate the airway and lung, whereas VR was used to evaluate the cardiovascular structures. Thin-section multiplanar reformatting was used to accurately measure the diameter or an area of the structure in question. As mentioned earlier, image reformatting techniques should be selected on a case-by-case basis to avoid obtaining faulty information. On average, image reformatting took about 1 hour per patient. VR for evaluation of the cardiovascular structures was the most time-consuming step because the skeletal thorax had to be "removed" with various segmentation techniques.
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Normal Anatomy
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Awareness of the normal cardiovascular anatomy is a prerequisite to understanding CHD. In the following sections, we review the basic anatomy in CHD with respect to the aorta, pulmonary artery, pulmonary vein, cardiac chambers, coronary artery, and valves (25,26). The normal bronchial branching pattern is also discussed because it is necessary for evaluation of the situs anomaly.
Aorta
The aorta consists of an ascending segment, a transverse segment or arch, and a descending segment (Fig 1). The ascending aorta arises from the left ventricle. Its proximal portion is called the aortic root and includes the aortic valve, annulus, and sinuses of Valsalva. The ascending aorta extends to the origin of the innominate artery. The aortic arch begins at the innominate artery and ends at the ligamentum or ductus arteriosum. It gives rise to the innominate, left carotid, and left subclavian arteries. The distal part of the aortic arch after the origin of the left subclavian artery is called the aortic isthmus. The aortic arch is usually on the left side. The descending aorta begins at the ligamentum or ductus, and its proximal portion may look slightly dilated. The intercostal artery and bronchial arteries are the branches of the descending aorta.
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Figure 1. Normal aorta. CT scan shows the ascending aorta (aA), aortic arch (Ar), and descending aorta (dA). The aortic root (Ro) represents the proximal portion of the ascending aorta, and the aortic isthmus (Is) represents the distal portion of the aortic arch.
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Pulmonary Artery
The main pulmonary artery arises from the right ventricular outflow tract. It passes to the left of and posterior to the aorta and divides into the right and left pulmonary arteries (Fig 2). The left pulmonary artery is shorter and higher than the right pulmonary artery and courses in a more posterior direction. The right pulmonary artery passes behind the ascending aorta, superior vena cava (SVC), and right upper pulmonary vein. The right and left pulmonary arteries divide into ascending and descending branches. The pulmonary artery branches to both lungs usually follow the corresponding bronchial course; however, variations may occur in the upper lobes. The morphologic features of the pulmonary arteries are fully evaluated in multiple planes, including curved planes (Fig 2).
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Figure 2a. Normal pulmonary arteries. Curved planar reformatted images show the right (a) and left (b) pulmonary arteries, along with the outlet portion of the right ventricle and the main pulmonary artery.
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Figure 2b. Normal pulmonary arteries. Curved planar reformatted images show the right (a) and left (b) pulmonary arteries, along with the outlet portion of the right ventricle and the main pulmonary artery.
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Pulmonary Vein
The pulmonary veins normally drain into the left atrium (Fig 3). The right middle and upper lobe veins join to form the right superior pulmonary vein. The left superior pulmonary vein receives blood from the left upper lobe. The right and left inferior pulmonary veins receive blood from the right and left lower lobes, respectively.
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Figure 3. Normal pulmonary veins. CT scan shows all the pulmonary veins, including the right superior (RS), right inferior (RI), left superior (LS), and left inferior (LI) pulmonary veins, with a normal venoatrial connection with the left atrium.
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Cardiac Chambers
In the right cardiac chambers, there is a muscular structure (ventriculoinfundibular fold) between the pulmonary and tricuspid valves that manifests as discontinuity between the valves (Fig 4a). In contrast, the left cardiac chambers show fibrous continuity between the aortic and mitral valves (Fig 4b). The right ventricle is characterized by coarse trabeculae and the moderator band (an extension of the anterior limb of the trabecula septomarginalis to the apical free wall). In contrast, the left ventricle shows fine trabeculae and a smooth endocardial surface. The tricuspid valve is slightly more apical in location than the mitral valve. The right atrial appendage is characterized by a wide opening, a triangular shape, and the pectinate muscle, whereas the left atrial appendage is narrow and fingerlike in shape and shows no pectinate muscle (Fig 4c). Among the criteria for determining the laterality of the atrium, the extent of the pectinate muscle from the atrioventricular junction, which is the most accurate criterion, cannot be seen because the spatial resolution of CT is insufficient. The right atrium is divided into the right atrium proper and the right atrial appendage by the crista terminalis (sulcus terminalis) (Fig 4d). The inferior vena cava (IVC) and the coronary sinus have valves at the right atrium that are known as the eustachian and thebesian valves, respectively.
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Figure 4a. Normal cardiac chambers. (a) CT scan of the right cardiac chambers demonstrates a muscular structure (arrowheads) between the tricuspid valve (TV) and the pulmonary valve (PV). The right ventricle shows coarse trabeculae. (b) CT scan of the left cardiac chambers demonstrates fibrous continuity (arrowhead) between the mitral valve (MV) and the aortic valve (AV). The left ventricle shows fine trabeculae. (c) CT scan shows the atrial appendages with a characteristic appearance. The right atrial appendage (RAA) is triangular with a wide opening, whereas the left atrial appendage (LAA) is narrow and fingerlike. (d) CT scan shows the crista (sulcus) terminalis (arrowhead), an anatomic landmark between the right atrium proper and the right atrial appendage.
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Figure 4b. Normal cardiac chambers. (a) CT scan of the right cardiac chambers demonstrates a muscular structure (arrowheads) between the tricuspid valve (TV) and the pulmonary valve (PV). The right ventricle shows coarse trabeculae. (b) CT scan of the left cardiac chambers demonstrates fibrous continuity (arrowhead) between the mitral valve (MV) and the aortic valve (AV). The left ventricle shows fine trabeculae. (c) CT scan shows the atrial appendages with a characteristic appearance. The right atrial appendage (RAA) is triangular with a wide opening, whereas the left atrial appendage (LAA) is narrow and fingerlike. (d) CT scan shows the crista (sulcus) terminalis (arrowhead), an anatomic landmark between the right atrium proper and the right atrial appendage.
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Figure 4c. Normal cardiac chambers. (a) CT scan of the right cardiac chambers demonstrates a muscular structure (arrowheads) between the tricuspid valve (TV) and the pulmonary valve (PV). The right ventricle shows coarse trabeculae. (b) CT scan of the left cardiac chambers demonstrates fibrous continuity (arrowhead) between the mitral valve (MV) and the aortic valve (AV). The left ventricle shows fine trabeculae. (c) CT scan shows the atrial appendages with a characteristic appearance. The right atrial appendage (RAA) is triangular with a wide opening, whereas the left atrial appendage (LAA) is narrow and fingerlike. (d) CT scan shows the crista (sulcus) terminalis (arrowhead), an anatomic landmark between the right atrium proper and the right atrial appendage.
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Figure 4d. Normal cardiac chambers. (a) CT scan of the right cardiac chambers demonstrates a muscular structure (arrowheads) between the tricuspid valve (TV) and the pulmonary valve (PV). The right ventricle shows coarse trabeculae. (b) CT scan of the left cardiac chambers demonstrates fibrous continuity (arrowhead) between the mitral valve (MV) and the aortic valve (AV). The left ventricle shows fine trabeculae. (c) CT scan shows the atrial appendages with a characteristic appearance. The right atrial appendage (RAA) is triangular with a wide opening, whereas the left atrial appendage (LAA) is narrow and fingerlike. (d) CT scan shows the crista (sulcus) terminalis (arrowhead), an anatomic landmark between the right atrium proper and the right atrial appendage.
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Bronchial Branching Pattern
The left lateral wall of the lower trachea is mildly indented by the left aortic arch. The right main bronchus is short and vertical, whereas the left main bronchus is long and horizontal. The relationship between the upper lobe bronchus and the branch pulmonary artery is also characteristic (Fig 5). The right pulmonary artery courses anterior and lateral to the right bronchus. The right upper lobe bronchus is superior to the descending branch of the right pulmonary artery (eparterial bronchus). The left pulmonary artery courses over the left upper lobe bronchus (hyparterial bronchus).
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Figure 5. Normal bronchial branching pattern. Coronal multiplanar reformatted image depicts a normal bronchial branching pattern. Note the mild indentation of the trachea by the left aortic arch (Ar). The relationships between the upper lobe bronchi and the pulmonary arteries are well seen. LPA = left pulmonary artery, LUL = left upper lobe, RPA = right pulmonary artery, RUL = right upper lobe.
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Coronary Artery
Each coronary artery arises from the corresponding aortic sinus (Fig 6a). The left coronary artery is divided into the left anterior descending artery and the left circumflex artery (Fig 6b). The left anterior descending artery courses along the anterior interventricular groove, whereas the left circumflex artery courses along the left atrioventricular groove. The right coronary artery runs along the anterior atrioventricular groove.
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Figure 6a. Normal coronary arteries. (a) On a CT scan, the right coronary artery (RCA) and left coronary artery (LCA) arise from the right (R) and left (L) aortic sinuses, respectively. The origin of the left coronary artery is higher than that of the right coronary artery. (b) CT scan shows how the left coronary artery (LCA) is divided into the left anterior descending artery (LAD) and the left circumflex artery (LCX). The right coronary artery (RCA) is seen in the plane that crosses the atrioventricular groove. CT delineates the proximal portions of the coronary arteries more frequently than the distal portions and the left coronary artery more frequently than the right coronary artery.
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Figure 6b. Normal coronary arteries. (a) On a CT scan, the right coronary artery (RCA) and left coronary artery (LCA) arise from the right (R) and left (L) aortic sinuses, respectively. The origin of the left coronary artery is higher than that of the right coronary artery. (b) CT scan shows how the left coronary artery (LCA) is divided into the left anterior descending artery (LAD) and the left circumflex artery (LCX). The right coronary artery (RCA) is seen in the plane that crosses the atrioventricular groove. CT delineates the proximal portions of the coronary arteries more frequently than the distal portions and the left coronary artery more frequently than the right coronary artery.
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Valves
The main pulmonary artery is normally anterior to and to the left of the ascending aorta. The aortic valve is deeply wedged between the tricuspid and mitral valves and consists of the right, left, and noncoronary cusps, the latter being posterior in location, whereas the pulmonary valve consists of the right, left, and anterior cusps (Fig 7a). The tricuspid valve consists of the septal, anterior, and posterior leaflets, whereas the mitral valve consists of the aortic (anterior) and mural (posterior) leaflets (Fig 7b).
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Figure 7a. Normal valves. (a) CT scan shows the aortic valve with right (R), left (L), and noncoronary (N) cusps and the pulmonary valve with right (R), left (L), and anterior (A) cusps. (b) CT scan shows the tricuspid valve with septal (S), anterior (A), and posterior (P) leaflets and the mitral valve with aortic (A) and mural (M) leaflets.
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Figure 7b. Normal valves. (a) CT scan shows the aortic valve with right (R), left (L), and noncoronary (N) cusps and the pulmonary valve with right (R), left (L), and anterior (A) cusps. (b) CT scan shows the tricuspid valve with septal (S), anterior (A), and posterior (P) leaflets and the mitral valve with aortic (A) and mural (M) leaflets.
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Typical Pathologic Conditions
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Typical appearances of various CHDs are demonstrated on reformatted CT scans tailored to the targeted pathologic conditions. These appearances typically represent a stenosis or obstruction, defect, or connection problem. The findings described in the following sections are seen at catheter cardioangiography (27), MR imaging (4, 28–37), and CT (1–24). All CT findings were confirmed with echocardiography, catheter cardioangiography, or surgery.
Extracardiac Abnormalities
Interrupted Aortic Arch.—
Interrupted aortic arch (IAA) is defined as a separation between the ascending and descending aortas (1,2,27–29) and is classified on the basis of the site of interruption: Type A is distal to the subclavian artery (Fig 8a), type B occurs between the second carotid and theipsilateral subclavian arteries (Fig 8b), and type C occurs between two carotid arteries. Each of these three types is further subdivided as follows: Subtype 1, normal subclavian artery; subtype 2, aberrant subclavian artery; and subtype 3, an isolated subclavian artery that arises from the ductus arteriosus. In addition to the type of IAA, evaluation of the distance between the proximal and distal segments, the size of a patent ductus arteriosus (PDA), the narrowest dimension of the left ventricular outflow tract, and other cardiac structural abnormalities are important for surgical planning. A right-sided descending aorta with aortic interruption is almost always associated with DiGeorge syndrome.
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Figure 8a. (a) Type A1 IAA. VR image (posterior view) shows the left aortic arch with aortic interruption just distal to the left subclavian artery (arrows). (b) Type B3 IAA. VR image (left posterior oblique view) shows interruption between the left common carotid artery and the left subclavian artery (arrowheads). An isolated right subclavian artery is also seen (arrow).
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Figure 8b. (a) Type A1 IAA. VR image (posterior view) shows the left aortic arch with aortic interruption just distal to the left subclavian artery (arrows). (b) Type B3 IAA. VR image (left posterior oblique view) shows interruption between the left common carotid artery and the left subclavian artery (arrowheads). An isolated right subclavian artery is also seen (arrow).
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Coarctation of the Aorta.—
In classic coarctation, the narrowing is located just distal to the left subclavian artery (1–4,27,28). Coarctation at or immediately proximal to the left subclavian artery is rare and compromises that vessel. An aberrant right subclavian artery may arise at or below the coarctation. An external indentation that involves all but the ventral portion of the coarctation corresponds internally to the ridge. The aorta just distal to the coarctation is typically dilated. Uniform narrowing of the aortic arch (tubular hypoplasia) can be more frequently observed in neonates (Fig 9). A localized coarctation and tubular hypoplasia may coexist or may occur independently.
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Figure 9. Coarctation of the aorta. VR image shows diffuse narrowing of the aortic arch and isthmus (tubular hypoplasia). A posterior indentation is seen at the level of the ductus arteriosus (arrowhead).
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Truncus Arteriosus and Aortopulmonary Window.—
In truncus arteriosus, a single arterial trunk arises from the ventricle via a single arterial valve to supply the systemic, pulmonary, and coronary arterial circulations (Fig 10a) (1,5,27,28). Aortopulmonary window is a communication between the ascending aorta and the pulmonary trunk in the presence of separate aortic and pulmonary valves (Fig 10b) (27,30). This defect is classified as proximal, distal, or total depending on its location.
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Figure 10a. (a) Truncus arteriosus. Combined CT scan and VR image show the truncus arteriosus (TA), from which the ascending aorta (aA) and pulmonary trunk (PT) arise. (b) Aortopulmonary window. VR image shows a distal aortopulmonary window (*), through which the ascending aorta (aA) and pulmonary trunk (PT) communicate with each other.
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Figure 10b. (a) Truncus arteriosus. Combined CT scan and VR image show the truncus arteriosus (TA), from which the ascending aorta (aA) and pulmonary trunk (PT) arise. (b) Aortopulmonary window. VR image shows a distal aortopulmonary window (*), through which the ascending aorta (aA) and pulmonary trunk (PT) communicate with each other.
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Anomalous Origin of One Pulmonary Artery from the Ascending Aorta.—
Rarely, one of the two pulmonary arteries arises from the ascending aorta and the other arises from the main pulmonary artery (27). Anomalous origin of the right pulmonary artery is far more frequent than anomalous origin of the left pulmonary artery (Fig 11).
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Figure 11a. Anomalous origin of one pulmonary artery from the ascending aorta. CT scans show anomalous origin of the right pulmonary artery (RPA), which arises from the ascending aorta (aA). In b, the left pulmonary artery (LPA) arises from the main pulmonary artery (MPA).
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Figure 11b. Anomalous origin of one pulmonary artery from the ascending aorta. CT scans show anomalous origin of the right pulmonary artery (RPA), which arises from the ascending aorta (aA). In b, the left pulmonary artery (LPA) arises from the main pulmonary artery (MPA).
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Pulmonary Artery Sling.—
In pulmonary artery sling, an aberrant left pulmonary artery arises from the proximal right pulmonary artery, courses between the trachea and esophagus, and extends to the left hilum (Fig 12) (6,7,27). Pulmonary artery sling may be associated with tracheal anomalies including tracheal bronchus, complete tracheal ring, and localized tracheomalacia.
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Figure 12a. Pulmonary artery sling. (a) On a CT scan, the left pulmonary artery (*) originates aberrantly from the proximal right pulmonary artery and crosses the midline between the trachea (arrow) and the esophagus (arrowhead). An associated tracheal ring is also seen. (b) VR image (posterior view) shows the characteristic course of the aberrant left pulmonary artery (*).
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Figure 12b. Pulmonary artery sling. (a) On a CT scan, the left pulmonary artery (*) originates aberrantly from the proximal right pulmonary artery and crosses the midline between the trachea (arrow) and the esophagus (arrowhead). An associated tracheal ring is also seen. (b) VR image (posterior view) shows the characteristic course of the aberrant left pulmonary artery (*).
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Patent Ductus Arteriosus.—
PDA is defined as persistent patency of the ductus arteriosus beyond functional closure after birth (27). Uncomplicated PDA connects the proximal descending aorta below the origin of the left subclavian artery with the roof of the main pulmonary artery near the orifice of the left pulmonary artery (Fig 13) (8). In right ventricular outflow obstruction, PDA arises from the undersurface of the aortic arch and usually inserts into the proximal left pulmonary artery.
Total Anomalous Pulmonary Venous Connection.—
Total anomalous pulmonary venous connection is characterized by connection of the pulmonary veins from both lungs to form a confluence behind the left atrium and connection of a venous channel from this confluence to a systemic vein, the right atrium, or both (Fig 14) (1,9,10, 27,28,31). Total anomalous pulmonary venous connection is described as supracardiac, cardiac, infracardiac, or mixed depending on the site or sites of connection. Supracardiac and cardiac types are rarely obstructive, but bilateral infracardiac types are almost always obstructive because the blood passes through the hepatic sinusoids.
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Figure 14. Total anomalous pulmonary venous connection. CT scan obtained with subvolume MIP shows a supracardiac type of total anomalous pulmonary venous connection with obstruction (arrowheads). All pulmonary veins are connected to the left brachiocephalic vein via the vertical vein (*).
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Partial Anomalous Pulmonary Venous Connection.—
In partial anomalous pulmonary venous connection, the pulmonary veins from some portions of both lungs show an anomalous connection (1,9,28,31). The usual sites of connection are the SVC and the right atrium (Fig 15) (11). In such cases, an association with the sinus venosus type of atrial septal defect is common. The connection of the right pulmonary vein to the IVC is called "scimitar vein" due to its curved configuration (12,13).
Left SVC.—
Left SVC is a common abnormality that drains into the right atrium via a dilated coronary sinus (Fig 16) (14,27,28,31). The innominate vein is commonly observed communicating between the right and left SVC. Recognition of the presence of a left SVC is important for surgical planning of either a classic right superior cavopulmonary connection or a bidirectional cavopulmonary connection.
Coronary Artery Anomaly.—
Coronary artery anomalies are major anomalies and are classified as anomalies of origin, course, termination or connection, and coronary size (15,27,32). Ap-proximately 20% of these anomalies have clinical consequences such as myocardial ischemia or infarction. Coronary artery anomalies include coronary artery fistula, anomalous left coronary artery from the pulmonary trunk, and anomalous origin from the contralateral facing aortic sinus. Noninvasive imaging is useful for delineating the origin and course of the coronary artery. It is important to determine whether the anomalous artery passes between the aorta and the pulmonary trunk (Fig 17). In addition, recognition of anomalous courses of the coronary artery is important in planning a surgical approach for tetralogy of Fallot or transposition of the great arteries.
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Figure 17. Coronary artery anomaly. Oblique axial CT scan shows an anomalous right coronary artery (arrowheads) that arises from the left aortic sinus and courses between the ascending aorta (aA) and the pulmonary trunk (PT). An anomalous coronary artery may be compressed between the great arteries, a condition that may lead to myocardial ischemia or infarction.
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Cardiac Abnormalities
Tetralogy of Fallot.—
The morphologic features of tetralogy of Fallot include subpulmonary infundibular stenosis, ventricular septal defect (VSD), overriding of the aorta, and right ventricular hypertrophy (Fig 18) (1,4,16,27,28). Anterosuperior deviation of the infundibular septum is considered the developmental cause for subpulmonary infundibular stenosis and VSD in tetralogy of Fallot. Hypertrophy of the infundibular septum and anterior muscle bundles contributes to pulmonary outlet obstruction in tetralogy of Fallot. Hypoplasia of the pulmonary valve and main pulmonary artery is common.
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Figure 18a. Tetralogy of Fallot. (a) CT scan shows a right ventricular outlet obstruction due to hypertrophy and anterosuperior displacement of the infundibular septum (arrows) and to hypertrophy of the anterior muscle bundles (*). (b) On an MIP image (right anterior oblique view) segmented for the right ventricle and pulmonary artery, the hypertrophic anterior muscle bundles (arrows) are seen to encroach on the right ventricular outflow tract, a finding that is best seen on this view.
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Figure 18b. Tetralogy of Fallot. (a) CT scan shows a right ventricular outlet obstruction due to hypertrophy and anterosuperior displacement of the infundibular septum (arrows) and to hypertrophy of the anterior muscle bundles (*). (b) On an MIP image (right anterior oblique view) segmented for the right ventricle and pulmonary artery, the hypertrophic anterior muscle bundles (arrows) are seen to encroach on the right ventricular outflow tract, a finding that is best seen on this view.
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Pulmonary Atresia with VSD.—
When pulmonary atresia with VSD is seen with atrioventricular and ventriculoarterial concordance, the lesion shows the morphologic characteristics of extreme tetralogy of Fallot (16,17,27,28,33). There is no pulmonary blood flow from either ventricle. Detailed morphologic evaluation of the central pulmonary artery and various pulmonary arterial feeding vessels is important for surgical planning (Fig 19). The central pulmonary artery may be either absent or present, and the branch pulmonary arteries may be either confluent or nonconfluent. The source of pulmonary blood flow may be multifocal, with a PDA or major aortopulmonary collateral vessels that supplement or replace primary pulmonary arterial blood flow. This source of pulmonary blood flow significantly affects the condition of the pulmonary vasculature and parenchyma.
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Figure 19a. Pulmonary atresia with VSD. LPA = left pulmonary artery, RPA = right pulmonary artery. (a) CT scan shows the confluent portion of the central pulmonary artery (arrowheads). (b) CT scan shows absence of the confluent portion of the central pulmonary artery (*). Each pulmonary artery was supplied by a corresponding PDA (not shown). (c) CT scans depict the major aortopulmonary collateral vessels that supply the branch pulmonary arteries. These collateral vessels arise from the descending thoracic aorta (dA).
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Figure 19b. Pulmonary atresia with VSD. LPA = left pulmonary artery, RPA = right pulmonary artery. (a) CT scan shows the confluent portion of the central pulmonary artery (arrowheads). (b) CT scan shows absence of the confluent portion of the central pulmonary artery (*). Each pulmonary artery was supplied by a corresponding PDA (not shown). (c) CT scans depict the major aortopulmonary collateral vessels that supply the branch pulmonary arteries. These collateral vessels arise from the descending thoracic aorta (dA).
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Figure 19c. Pulmonary atresia with VSD. LPA = left pulmonary artery, RPA = right pulmonary artery. (a) CT scan shows the confluent portion of the central pulmonary artery (arrowheads). (b) CT scan shows absence of the confluent portion of the central pulmonary artery (*). Each pulmonary artery was supplied by a corresponding PDA (not shown). (c) CT scans depict the major aortopulmonary collateral vessels that supply the branch pulmonary arteries. These collateral vessels arise from the descending thoracic aorta (dA).
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Ebstein Anomaly.—
Ebstein anomaly is defined as displacement of the attachment of the tricuspid valve leaflets from the atrioventricular junction to the right ventricular cavity with resultant atrialization of the inlet of the right ventricle (Fig 20) (27,34). Displacement of the tricuspid valve attachment almost always involves only the septal and posterior leaflets and is maximal at the commissure between these two leaflets. The nondisplaced anterior leaflet is usually large and redundant, with a mobility that varies depending on the degree of tethering to the right ventricular wall.
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Figure 20. Ebstein anomaly. Oblique axial CT scan shows apical displacement of the septal and posterior leaflets of the tricuspid valve (arrowhead) from the atrioventricular junction (arrows). Note the dilated right atrium (RA), atrialized right ventricle (ARV), and functional right ventricle (FRV). Clockwise rotation of the heart and posterior bulging of the ventricles are also seen.
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Tricuspid Atresia.—
In tricuspid atresia, the morphologic right atrium has no direct communication with the right ventricle (27). There are two types of tricuspid atresia. In the more common type, the right atrioventricular connection is absent and areolar sulcus tissue occupies the gap (Fig 21) (18). In the rarer type, an atretic tricuspid valve is present.
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Figure 21. Tricuspid atresia. CT scan shows fatty tissue (arrowheads) between the right atrium (RA) and the right ventricle (RV), which prevents any direct connection between the two compartments. This case represents the more common type of tricuspid atresia.
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Ventricular Septal Defect.—
VSD is a hole or holes of variable size in the interventricular septum (27,35). Because most VSDs are repaired on the right side of the heart, VSDs are classified in terms of their appearance from the lumen of the right ventricle as either perimembranous, muscular, or doubly committed juxtaarterial defects (Fig 22). The ventricular septum has a membranous part and a muscular part. The membranous septum is further subdivided into atrioventricular and interventricular components by the more apical attachment of the septal leaflet of the tricuspid valve. The muscular septum has three components: the inlet, trabecular, and outlet components.
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Figure 22a. VSD. CT scans reformatted along the interventricular septum provide en face views. (a) Normal interventricular septum. (b-e) Various types of VSDs (*). (b) Large perimembranous defect (arrowheads), which typically abuts the fibrous continuity between the tricuspid and mitral valves and the aortic valve ("central fibrous body"). (c) Perimembranous defect with inlet extension (arrowheads). (d) Doubly committed juxtaarterial defect (arrowheads) immediately below the aortic and pulmonary valves. (e) Restrictive defect ("bulboventricular foramen") (arrowheads) in the double inlet ventricle.
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Figure 22b. VSD. CT scans reformatted along the interventricular septum provide en face views. (a) Normal interventricular septum. (b-e) Various types of VSDs (*). (b) Large perimembranous defect (arrowheads), which typically abuts the fibrous continuity between the tricuspid and mitral valves and the aortic valve ("central fibrous body"). (c) Perimembranous defect with inlet extension (arrowheads). (d) Doubly committed juxtaarterial defect (arrowheads) immediately below the aortic and pulmonary valves. (e) Restrictive defect ("bulboventricular foramen") (arrowheads) in the double inlet ventricle.
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Figure 22c. VSD. CT scans reformatted along the interventricular septum provide en face views. (a) Normal interventricular septum. (b-e) Various types of VSDs (*). (b) Large perimembranous defect (arrowheads), which typically abuts the fibrous continuity between the tricuspid and mitral valves and the aortic valve ("central fibrous body"). (c) Perimembranous defect with inlet extension (arrowheads). (d) Doubly committed juxtaarterial defect (arrowheads) immediately below the aortic and pulmonary valves. (e) Restrictive defect ("bulboventricular foramen") (arrowheads) in the double inlet ventricle.
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Figure 22d. VSD. CT scans reformatted along the interventricular septum provide en face views. (a) Normal interventricular septum. (b-e) Various types of VSDs (*). (b) Large perimembranous defect (arrowheads), which typically abuts the fibrous continuity between the tricuspid and mitral valves and the aortic valve ("central fibrous body"). (c) Perimembranous defect with inlet extension (arrowheads). (d) Doubly committed juxtaarterial defect (arrowheads) immediately below the aortic and pulmonary valves. (e) Restrictive defect ("bulboventricular foramen") (arrowheads) in the double inlet ventricle.
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Figure 22e. VSD. CT scans reformatted along the interventricular septum provide en face views. (a) Normal interventricular septum. (b-e) Various types of VSDs (*). (b) Large perimembranous defect (arrowheads), which typically abuts the fibrous continuity between the tricuspid and mitral valves and the aortic valve ("central fibrous body"). (c) Perimembranous defect with inlet extension (arrowheads). (d) Doubly committed juxtaarterial defect (arrowheads) immediately below the aortic and pulmonary valves. (e) Restrictive defect ("bulboventricular foramen") (arrowheads) in the double inlet ventricle.
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Atrioventricular Septal Defect.—
Atrioventricular septal defect is a defect in the atrioventricular septum with variable involvement of the adjacent atrial and ventricular septa (Fig 23) (27,35). There is an abnormal arrangement of the atrioventricular valve leaflets (anterior and posterior bridging leaflets, right and left mural leaflets, anterosuperior leaflet). The aortic valve is anterosuperiorly displaced from its normal wedged position. The left ventricle has a short inlet and an elongated outlet.
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Figure 23. Atrioventricular septal defect. CT scan shows an atrioventricular septal defect (*) and a free-floating common atrioventricular valve with a bridging leaflet (arrowheads) that involves the adjacent atrial and ventricular septa as well as the atrioventricular septum. Dextrocardia and a right descending aorta are also noted.
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Connection Problems
Complete Transposition of the Great Arteries.—
Complete transposition of the great arteries is a combination of atrioventricular concordance and ventriculoarterial discordance (ie, the ascending aorta arises from the right ventricle and the pulmonary artery from the left ventricle) (Fig 24) (1,19,27,28). The systemic and pulmonary circulations are parallel and independent closed circuits. Therefore, the blood between the two parallel circulations should be mixed through the VSD, PDA, or atrial septal defect to prevent severe cyanosis and metabolic acidosis.
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Figure 24. Complete transposition of the great arteries. On a CT scan, the ascending aorta (aA) arises from the right ventricle and courses anterior to the pulmonary trunk (PT), which arises from the left ventricle. Aortic coarctation is also seen. LT = left cardiac chamber, RT = right cardiac chamber.
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Congenitally Corrected Transposition of the Great Arteries.—
Congenitally corrected transposition of the great arteries is a condition in which both the atrioventricular and ventriculoarterial connections are discordant (Fig 25) (19,27,28). Accordingly, it is a hemodynamically normal condition when there is no other cardiac anomaly.
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Figure 25a. Congenitally corrected transposition of the great arteries. (a) On a CT scan, the pulmonary trunk (PT) arises from the left ventricle (LV), which is connected to the right atrium (RA). RV = right ventricle. (b) CT scan shows that the ascending aorta (aA) arises from the right ventricle (RV), which is connected to the left atrium (LA). The ascending aorta courses anterior to and to the left of the pulmonary trunk (PT).
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Figure 25b. Congenitally corrected transposition of the great arteries. (a) On a CT scan, the pulmonary trunk (PT) arises from the left ventricle (LV), which is connected to the right atrium (RA). RV = right ventricle. (b) CT scan shows that the ascending aorta (aA) arises from the right ventricle (RV), which is connecte | |
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Abstract
Learning Objectives for Test...
