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 patient’s 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 (6–10) 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 patient’s 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 patient’s 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 weight–based low-dose protocol (120 kV, 30–80 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 patient’s 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 1–1.5 mL/kg body weight and a rate of 3–4 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 patient’s 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 patient’s 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 patient’s 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) (25–29).
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 (25–29). 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 veins—the 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 veins—the 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 veins—the 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 veins—the 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 veins—the 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 veins—the 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 veins—the 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 veins—the 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 connections—venoatrial, atrioventricular, and ventriculoarterial—must 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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Abstract
LEARNING OBJECTIVES FOR TEST...
