Magnetic resonance imaging of cyanotic and noncyanotic congenital heart disease

Magn Reson Imaging Clin N Am 10 (2002) 209–235

Magnetic resonance imaging of cyanotic and noncyanotic congenital heart disease Fernando R. Gutierrez, MD*, Marilyn J. Siegel, MD, Juliet Howard Fallah, MD, Mehdi Poustchi-Amin, MD Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 South Kingshighway Boulevard, St. Louis, MO 63110, USA

Congenital heart disease (CHD) is a relatively common problem, with an incidence of approximately 5 to 12 per 1000 live births [1]. Over the past two decades, the trend has been to perform more types of surgical repair at earlier ages. Nevertheless, even after operative repair, many of these patients have residual anatomic defects and require close longitudinal follow-up [2,3]. The imaging evaluation of the infant or child with suspected heart disease begins with a chest radiograph followed by transthoracic echocardiography, which is readily available, portable, and noninvasive. The use of echocardiography can obviate or, in many instances, serve as a ‘‘roadmap’’ to guide cardiac catheterization. The echocardiogram is hampered by chest wall deformities, air-filled lung, and sternal wires. In addition, the ability of sonography to evaluate the ventricular chambers, right ventricular outflow tract, and pulmonary arteries may be limited [4]. In these cases, additional diagnostic studies are needed. Transesophageal echocardiography provides better spatial resolution, although it is a more invasive procedure. Cineangiography has been the ‘‘gold standard’’ for evaluating cardiac morphology, but it is expensive and invasive with risks related to arterial puncture and contrast administration. MRI can play an important complementary role to echocardiography and cineangiography in the diagnosis and follow-up of children with CHD [5]. It can provide a wealth of morphologic

* Corresponding author. E-mailaddress: [email protected] (F.R.Gutierrez).

and functional information in an accurate and noninvasive fashion. MRI provides unlimited visualization of the thoracic cavity and can image the patient in any desired plane. The great vessels and pulmonary circulation can be evaluated, and detailed assessment of ventricular anatomy, size, and function can be accurately obtained [3,6]. Flow velocities, shunts, pressure gradients, and ventricular volumes can be reliably calculated. Unlike transthoracic echocardiography, MRI is not limited by surgical changes, such as median sternotomy wires or valvular prostheses. Before performing MRI in patients with CHD, the results of prior studies, including chest radiographs, echocardiography, and cardiac angiography, should be reviewed. This will help to identify evidence of prior surgery, thoracic deformities, and ferromagnetic objects or pacemaker wires, which can influence the quality and safety of the study. In addition, the review of prior imaging examinations can provide information about heart size and position, pulmonary vascularity, and asymmetry of blood flow, which can help to optimize the design of the MR examination. The primary goal of the MR examination in patients with known or suspected CHD is to characterize the lesion and determine its extent, which is important information for surgical planning. This article addresses the current use of MRI in the evaluation of patients with CHD. The general principles and techniques of performing cardiac MR and the MR features of the most common congenital cardiac abnormalities are presented. The MR appearance of the postoperative patient is also discussed.

1064-9689/02/$ - see front matter
2002, Elsevier Science (USA). All rights reserved. PII: S 1 0 6 4 - 9 6 8 9 ( 0 1 ) 0 0 0 0 7 - 1

210

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

General principles Safety considerations Magnetic field strength The primary safety considerations are related to the biologic effects of the static magnetic field and the effects of magnetic radiation on metallic objects. Gradient magnetic fields do not seem to create hazardous biologic effects. Most studies have shown that field strengths up to 2 T produce no substantial harmful biologic effects. Elevation of the T wave on the electrocardiogram (ECG) can be observed as a result of blood flowing through the static magnetic field and generating a biopotential [7]. The degree of elevation is directly proportional to the strength of the magnetic field. No associated biologic risks are believed to accompany these ECG findings. In patients with coronary disease, there may be concern that T-wave abnormalities occurring as a result of myocardial ischemia or infarction may be masked by the MR-induced ECG changes. In these patients, it may be appropriate to perform an ECG before and after the MR examination to assess for interval change. To date, there is no indication that MRI has produced deleterious effects on the fetus. MRI is considered appropriate in pregnant women if other nonionizing forms of radiation are inadequate or if the examination is likely to provide clinically important information that could not otherwise be obtained without exposure to ionizing radiation [8]. The primary biologic effects associated with an exposure to radiofrequency radiation seem to be related to the thermogenic properties of the electromagnetic field. U.S. Food and Drug Administration guidelines concerning safety standards for exposure to radiofrequency radiation should be followed to minimize the risk of local thermal injury.

Metallic objects A biomedical implant or device may be a contraindication to MRI. These objects pose a risk related to movement as well as to induction of electric current, excessive heating, and image artifact production [9]. There are published lists that define the ferromagnetic properties of many implants and devices [10]. If an object is not on the list and its ferromagnetic property is unknown, it is prudent to contact the manufacturer to ensure MR compatibility.

The U.S. Food and Drug Administration requires that any patient with an electric, magnetic, or mechanically activated implant should not undergo MRI, because the electromagnetic fields may interfere with the operation of the device and injure the patient. Examples include cardiac pacemakers and defibrillators, some ocular implants, some cochlear implants, and some penile implants. Also included are external hearing aids, neurostimulators, bone growth stimulators, drug infusion pumps, magnetic dental implants, ventricular shunt connectors, and the Sophy adjustable pressure valve [9,10]. Pellets, bullets, and shrapnel may contain ferrous material, and the risks of imaging (including proximity to vital structures) should be carefully weighed against the potential benefits. Objects that do not pose a risk to the patient but that may cause image distortion include orthopedic implants, breast tissue expanders and mammary implants, dental implants, cervical fixation devices, and halo vests. Many cardiac valve prostheses display measurable attraction to static magnetic fields, but the actual forces are minimal compared with the force of the normal beating heart. MRI is not considered hazardous for most patients with cardiac valvular prostheses. In addition, metallic cardiac occluders used to obliterate shunt lesions, coils, filters, median sternotomy wires, and stents are unlikely to move during MRI because of the tissue ingrowth that occurs within approximately 6 weeks after their placement. Vascular access ports and catheters are generally safe. Those that are constructed entirely from nonmetal materials create the least amount of artifact. The major problem related to the metallic foreign bodies described previously is artifact production. Heating generated during the MR procedure does not seem, in practice, to be a substantial hazard. Image artifacts resulting from the presence of a metallic object occur as a result of disruption of the local magnetic field, which interferes with image reconstruction. The degree of image distortion is a result of the magnetic susceptibility of the object, shape and position of the object, and pulse sequence used. Nonferromagnetic objects result in less image artifact than ferromagnetic objects. Patient preparation/sedation One of the common causes of an inadequate or incomplete study involves dysphoric psychologic reactions, such as claustrophobia and panic

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

attacks. Up to 65% of patients experience sensations of apprehension, anxiety, fear, and panic during MRI [11]. As many as 20% cannot complete the examination because of these feelings. Several strategies can minimize these reactions. Newer MR systems have a more vertical architecture and open design, Unfortunately, these systems are currently limited to a field strength of 0.3 T, making them unsuitable for cardiac evaluation. Additional strategies include thorough patient education about the procedure, verbal contact during the examination, headphones or a movie during the examination, bright lights, and allowing a family member or friend in the room. If these prove unsuccessful, relaxation techniques (eg, deep breathing) or pharmacologic sedation can be employed. Sedation is often required for children less than 6 years of age. It also may be needed in older children with developmental delay in whom mental capacity limits understanding of the procedure and compliance. The form of sedation for MRI is conscious sedation. The use of sedation requires attention to strict standards of care. These are based on the recommendations of the Joint Commission of Accreditation of Health Care Organizations, American Academy of Pediatrics, and American Society of Anesthesiologists Task Force. Before a child is sedated, it is important to have appropriate physiologic monitoring equipment available. This includes at least a pulse oximeter as well as monitors for heart and respiratory rates. Oxygen and equipment for resuscitation also need to be available. The patient must be evaluated by a registered nurse or radiologist before sedation to assess his/her current state of health, existing conditions that may be a contraindication to sedation, allergies, and current medications. Sedation procedures should be discussed with the family, and questions should be clarified. The patient’s vital signs and oxygen saturation are then assessed and documented before the administration of sedating medications. Aspiration is a major clinical concern in sedated children and non per os (nothing by mouth) guidelines should be as stringent as those used for general anesthesia. Based on guidelines for conscious sedation set by the American Academy of Pediatrics, clear liquids are allowed up to 2 hours before the procedure for patients of any age. Semisolid liquids (including breast milk) and solid foods are allowed for up to 4 hours before the procedure for children less than 6 months of age; for up to 6 hours before the proce-

211

dure for children from 6 to 36 months of age; and for up to 8 hours before the procedure for older children. The drugs most frequently used for conscious sedation are oral chloral hydrate and intravenous pentobarbital sodium. Oral chloral hydrate is the drug of choice for children younger than 18 months. Intravenous pentobarbital sodium is advocated in children older than 18 months. It is injected slowly in fractions of one fourth of the total dose and is titrated against the patient’s response. Regardless of the method of sedation, the child must be closely monitored during and after the MR examination. Proper equipment and personnel trained in pediatric resuscitation and cardiorespiratory support must be present throughout and after the procedure. Patient monitoring As noted previously, all patients, sedated and nonsedated, should be monitored during the examination. Nonsedated patients can be visually or verbally monitored. Sedated patients should be monitored physiologically. Physiologic parameters that need to be monitored include oxygenation (measured by pulse oximetry), heart rate, respiratory rate, blood pressure, ECG, and temperature. MR-compatible devices that can be placed at a suitable distance from the magnet are available. Staff personnel should be familiar with the use of these MR-compatible devices as well as with alterations of function that may result from proximity to the magnetic field (eg, ECG changes described previously).

General cardiac MRI techniques The radiologist should be present during the MR examination. This allows expeditious interpretation of findings as well as the capability to tailor the MR technique so that it addresses the specific clinical problem. Before the start of the study, the radiologist should review the clinical problem and prior imaging studies, have a well-defined protocol (preferably programmed into the MR unit), and communicate the imaging plan to the technologists and anesthesiologists involved with the study. Communication between the referring physician and radiologist is important so as to understand the specific clinical question. The patient should be given instructions about breathing before the start of the study. Irregular breathing, cough, and frequent swallowing can degrade image quality.

212

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

Cardiac gating MR images of the heart must be gated to avoid image blurring and to reduce flow and motion artifacts. The most effective gating involves the use of the ECG signal. Gating is triggered to the R wave of the QRS complex of the ECG. If that fails, gating can be triggered to a peripheral pulse. The common configuration for placement of ECG leads for cardiac gating is shown in Fig. 1. Good skin contact can be obtained by wiping the skin with alcohol and using special ECG gels that are placed between the electrodes and skin surface. The objective of ECG gating is to acquire an R wave that is substantially taller than the T or S wave of the ECG. It should be recognized that once the patient enters the magnet or after MRI has started, additional electric noise is added to the signal used for ECG triggering, which can obscure the R wave. Repositioning of the electrodes or the use of newer commercial physiologic monitoring devices with fiberoptic links can help to minimize this problem [12]. Specific sequences and techniques With recent technologic advances in MR hardware and software, there are now many pulse sequences available for cardiac MRI. Pulse sequences currently used for cardiac imaging can be divided into two major groups: dark-blood pool and bright-blood pool techniques. Both sequences provide information about cardiac morphology. The bright-blood pool sequences also

provide information about myocardial function and flow dynamics, especially when viewed in a cine format (ie, cine MRI and velocity-encoded cine MRI). MR angiography is another type of study that can provide morphologic data. Dark-blood pool techniques In the dark-blood pool techniques, fast-flowing blood is black or of low signal intensity. Blackblood techniques include the conventional spinecho (SE) and faster breath-hold techniques that can substantially shorten the duration of a cardiovascular study. The faster acquisition sequences include turbo SE, single-shot fast SE, and halfFourier rapid acquisition with relaxation enhancement (HASTE). These faster sequences are capable of acquiring data over a single heartbeat. These sequences generally have poorer resolution and more blurring compared with the standard SE sequences, however. The black-blood pool techniques provide anatomic information about blood vessels and cardiac chambers [13,14]. Functional abnormalities can only be inferred by analysis of resultant morphologic changes [12]. For example, aortic regurgitation can be inferred by the presence of a dilated left ventricle or dilated aortic root, although the regurgitant flow cannot be directly visualized. The blood pool is black because blood exposed to a 90 pulse has usually moved out of the imaging section before being exposed to a 180 pulse. If blood is traveling fast enough, it is not exposed to a 180 pulse. Some sections obtained with SE

Fig. 1. Cardiac gating. Configuration for echocardiographic lead placement.

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

sequences are acquired at different phases of the cardiac cycle, however. Those acquired during diastole may show increased signal intensity as a result of exposure to both 90 and 180 pulses. In addition, increased signal intensity may be seen within the cardiac chambers and pulmonary arteries as a result of slow blood flow caused by either decreased cardiac output or the Eisenmenger syndrome. Bright-blood pool techniques In the bright-blood pool techniques, flowing blood is white or of high signal intensity. These images are routinely obtained using gradientrecalled-echo sequences (GRE). This technique can be used to obtain anatomic and dynamic information. Cine and fast MRI GRE sequences form the basis for cine MRI, which is the most frequently used imaging tool to study flow dynamics. Unlike SE imaging, where various sections are obtained at different phases of the cardiac cycle, a single section can be evaluated with cine MRI at multiple phases of the cardiac cycle, or multiple sections can be evaluated during a single phase. The individual images are viewed together in a cine loop, which gives a graphic depiction of the beating heart. This information can be used to assess systolic wall thickening, turbulent flow, and the direction of flow in shunt lesions. Volumetric data about ventricular size, stroke volume, ejection fraction, and shunt fraction can also be acquired. Velocity- or phase-encoding imaging is required to actually quantify ventricular or valvular function, however (see below). With conventional SE and cine imaging, a single line of k space is acquired per R-R interval. In segmented acquisition of k space, multiple lines of k space are acquired per R-R interval. If the number of k-space lines is high enough, the acquisition time can be reduced to the duration of a breath hold. In cardiovascular imaging, the segmented k-space technique is most often used with cine MRI and its variations (eg, phase-contrast imaging). This technique has dramatically improved functional studies by allowing a thorough evaluation of the heart in a short span of time. Volumetric studies The cine technique allows a more precise estimate of end systole and end diastole. Ventricular

213

size is assessed by the acquisition of contiguous sections in the short axis. The summation of the product across the whole ventricle (slice thickness · area) provides an estimate of the ventricular volume. Ejection fraction is the ratio of the differences between end-systolic and end-diastolic volumes. Shunt fraction is the ratio of differences in right and left ventricular stoke volume. Stroke volume (in milliliters per beat) is the amount of blood pumped out of the heart in each systole (cardiac output/heart rate). Quantitative cardiac MRI (velocity-encoded cine MRI) Velocity-encoded or phase-mapping cine MRI is a modified GRE technique that is used to quantify blood flow and velocity. It is helpful in the evaluation of shunt lesions as well as regurgitant and stenotic valvular lesions. Valvular regurgitation can also be assessed by quantifying the region of signal void caused by the regurgitation jet. Cine MRI using velocity-encoded phasecontrast MRI allows a direct measurement of antegrade or retrograde flow velocity in a cardiac chamber or across a valve in a manner similar to Doppler echocardiography. The MR signal is composed of two types of information: magnitude and phase. Images reconstructed in magnitude provide anatomic information, whereas images reconstructed in phase provide velocity information [13]. Velocity-encoded cine images are made from phase information. Velocity-encoded MRI is based on the principle that the phase of flowing spins relative to stationary spins along a magnetic gradient changes in direct proportion to the velocity of flow. Two sets of images are acquired simultaneously: one with and one without velocity encoding. The subtraction of the two images allows the calculation of a phase shift that is proportional to the velocity of flow along the direction of the flow compensation gradient. Protons that do not move have a zero velocity or zero phase angle and are assigned to the middle of a gray scale. Protons that move are assigned an increasing positive value (white) as they move in one direction and an increasing negative (black) value as they move in the opposite direction. Velocity values can be integrated during systole to measure systolic flow and during diastole to measure diastolic flow. An actual measurement of velocity is generated by placement of a cursor at any location. If the peak systolic velocity (Vmax) is known, the pressure gradient across a stenosis can be

214

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

calculated by using a modified Bernoulli equation [(DP ¼ 4 · (Vmax)2] [20]. This is done by using slice-select direction and frequency-encoded or phase-encoded direction sequences [13,15]. Contrast-enhanced MR angiography Contrast-enhanced MR angiography is a useful study to improve image quality and reduce signal loss caused by abnormal blood flow patterns. Gadolinium is the agent of choice and is safe to use in the pediatric population. The rationale for using gadolinium is to shorten the T1 weighting of blood to less than that of tissue. As a result, contrast-enhanced MR angiography is not dependent on the inflow of unsaturated blood. The repetition time can also be quite short without degrading the image. Gadolinium-enhanced MR angiography is a three-dimensional GRE sequence with a short repetition time (TR), echo time (TE), and flip angle. Cardiac gating is not needed. This technique can be performed with or without breath holding. The advantage of breath-hold MR angiography is that it negates the effects of respiratory motion and reduces blurring. Spatial resolution can be improved with non-breath-hold MR angiog-

raphy, however. A test bolus injection or bolus tracking system, such as CareBolus (Siemens, NJ) or SmartPrep (General Electric, Milwaukee, WI), should be used to calculate the circulation time and obtain images with maximum arterial enhancement. With a breath-hold technique, the injection of the gadolinium should begin 10 to 15 seconds before data acquisition begins. With the longer non-breath-hold technique, the injection should begin just as data acquisition begins. The dose of gadolinium-diethylentriamine penta-acetic acid (DTPA) is 0.1 mmol/kg. With proper timing, both techniques should provide an arterial phase angiogram with little or no venous contamination. Delayed images should be obtained to evaluate the venous system and to demonstrate slow arterial flow. Images are usually obtained in the coronal plane (Fig. 2). Precontrast images are obtained routinely and serve as a mask for image subtraction. After image acquisition, the source images are postprocessed and reconstructed as three-dimensional maximum intensity projection images. The source images should be viewed in addition to the maximum intensity projection images. The latter display only the brightest pixels and thus, may obscure pathologic findings.

Fig. 2. Three-dimensional gadolinium-enhanced MR angiography. Systemic venous return of both upper lobes of pulmonary veins. The left upper lobe branch drains into left innominate vein (arrowheads), whereas the right upper lobe drains directly into superior vena cava (arrow).

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

The advantage of MR angiography compared with black– or white–blood pool sequences is the preferential enhancement of arteries and veins, leading to their easier identification (see Fig. 2). This can improve the evaluation of stenoses, collateral vessels, and shunts.

Specific imaging planes In this section, a series of imaging planes is described. These should provide a basis from which to prescribe the planes needed to address the particular clinical situation at hand. The planes used for cardiac imaging are the three orthogonal planes of the thorax (transverse, sagittal, and coronal) with the patient placed in a supine position. Slice thickness is usually 5 mm and contiguous with no gap. Because the cardiac axes are not parallel to the axes of the body, sections should also be obtained parallel and orthogonal to the cardiac axes (short-axis and long-axis views of the heart). A phased-array surface coil usually suffices to obtain a good signalto-noise ratio. The MR study should begin with a general anatomic survey of the heart chambers using a dark–blood technique such as HASTE in the axial, coronal, and sagittal planes. If performed properly, these sequences should provide information about the relation of the heart chambers to each other, to their respective venous and arterial connections, and to the rest of the mediastinum [11,14,16]. They also provide information about visceroatrial situs and the nature of previous cardiac operations, whether palliative or definitive. Once the blackblood images are acquired, the bright-blood sequences should be obtained. The choice of a specific plane is delineated in large part by the findings on the black-blood images and is usually selected to further interrogate suspicious findings seen on preliminary images. The entire examination can usually be completed in 30 to 45 minutes.

215

Coronal and sagittal planes The coronal plane (Fig. 4) is effective for demonstrating the aortic valve, the entrance of the upper lobe pulmonary veins into the left atrium, the diaphragmatic surface of the left ventricle, and the extension of pericardium over the proximal portion of the great arteries. Sagittal or oblique/sagittal planes are useful for showing the entire extent of the aorta, the pulmonic (Fig. 5) and aortic (Fig. 6) valves and outflow tracts, the connections of the superior and inferior vena cavae to the right atrium, and the sinuses of Valsalva. Long-axis plane Vertical (two-chamber view) After the three orthogonal views have been acquired, images parallel to the true short and long axes of the heart can be obtained as needed. Because the heart lies obliquely in the thoracic cavity, the true vertical long axis of the heart is oriented approximately 45 to the midsagittal plane of the thoracic spine. Images parallel to this line produce the vertical long-axis plane (Fig. 7). This plane is prescribed from an axial image that shows the largest oblique diameter of the left ventricle. The vertical long-axis plane or two-chamber view is used to evaluate the left heart structures as well as the right ventricular outflow tract. It also reveals information about the anatomic relation of structures superoinferior and anteroposterior to the heart. Horizontal (four-chamber view) The horizontal long-axis plane or four-chamber view is obtained from the two-chamber view. Images are acquired at 90 to the vertical longaxis plane. This plane displays the relation of the four cardiac chambers to each other on a single image (Fig. 8). Cine GRE images obtained in this plane enable an evaluation of mitral, tricuspid, and aortic valve function as well as right and left ventricular contraction.

Transverse or axial plane The axial plane is the standard imaging plane for cardiac and aortic anomalies. Transverse or axial images (Fig. 3) at the base of the heart display the normal relations of the great vessels and cardiac chambers as well as the patient’s situs. Portions of the proximal coronary arteries near their origin and the pericardium can also be identified. Atrial and ventricular septal defects are usually easily identified on axial images.

Short-axis plane The short-axis plane (Fig. 9) is obtained when images are prescribed perpendicular to the long axis of the left ventricle seen on the two-chamber view. This plane shows the true cross-sectional dimensions of the cardiac chambers. This plane can also be used to quantify wall thickening (Fig. 10), left and right ventricular volume and mass, and the ventricular ejection fraction. Differences between right

216

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

Fig. 3. Transverse or axial images. Dark-blood half-Fourier rapid acquisition with relaxation enhancement (A) and bright-blood cine gradient-recalled-echo (B) images. LV¼left ventricle; RV¼right ventricle.

and left ventricular stroke volumes can be used to estimate valvular regurgitation or shunt fractions.

Noncyanotic shunt defects All forms of CHD cannot be discussed in detail in this article. Nevertheless, pertinent MR findings of the more common shunt and obstructive anomalies are reviewed. The differential diagnostic considerations of CHD are often based on the presence or absence of clinical cyanosis. Noncyanotic heart lesions represent most of the congenital heart defects. In general, these lesions can often be diagnosed by the combination of chest radiography and echocardiography. MRI can provide useful information

when there is inadequate acoustic windowing caused by either chest deformities or postoperative metal in the chest wall or sternum or when there are multiple defects. MRI can also provide information about pulmonary vascular resistance [17] and quantitative information about pulmonaryto-systemic flow ratios [18].

Atrial septal defect Atrial septal defect (ASD) represents about 10% of congenital heart defects. There is a femaleto-male ratio of 3:2. ASD can occur in families, and it can be associated with the Holt-Oram syndrome, partial anomalous pulmonary venous return, or mitral valve prolapse. Depending on

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

217

Fig. 4. Coronal images. Half-Fourier rapid acquisition with relaxation enhancement (A) and bright-blood cine gradientrecalled-echo (B) images. RA ¼ right atrium; LV ¼ left ventricle; PA ¼ main pulmonary artery; A ¼ aortic arch.

the anatomic location of the defect, three major types have been described: ostium secundum, sinus venosus, and ostium primum. ASDs are usually easily identified on axial views (Fig. 11). The ostium secundum defect is the most common form of ASD and affects the area of the fossa ovalis. Although echocardiography is the imaging modality of choice for diagnosis, MRI can provide additional information regarding the size, location, and magnitude of the shunt. Particular care must be exercised not to confuse lack of signal at the level of the normal fossa ovalis for a septal defect. As a rule of thumb, the normal fossa ovalis exhibits gradually tapering borders, whereas a true ASD terminates abruptly at the septum.

The sinus venosus form of ASD refers to a defect high in the interatrial septum. It is associated with partial anomalous pulmonary venous return of the right upper lobe branch, which drains directly into the junction of the superior vena cava and right atrium. Occasionally, isolated partial anomalous venous return can produce clinical and hemodynamic features similar to those of an ASD. In this instance, MRI can provide superb anatomic information regarding the correct diagnosis (Fig. 12). The ostium primum form of ASD is characterized by a defect in the lower portion of the atrial septum and is frequently associated with trisomy 21. Affected patients often exhibit associated insufficiency across a cleft mitral valve and left

218

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

Fig. 5. Sagittal turbo spin-echo T1-weighted (A) and cine gradient-recalled-echo (B) images through normal pulmonary trunk. RV ¼ right ventricle; LA ¼ left atrium; PA ¼ main pulmonary artery; arrow ¼ aortic valve.

ventricular-to-right atrial shunting. Both of these anomalies can be recognized on GRE sequences in the long-axis plane. With long-standing left-to-right shunts, resistance in the pulmonary circulation increases, leading to the Eisenmenger syndrome. High signal intensity in the central pulmonary arteries is a hallmark of elevated pressure/resistance in the pulmonary circuit (Fig. 13). Ventricular septal defect Ventricular septal defect (VSD) represents a spectrum of defects of the ventricular septum that can be isolated or can coexist with other complex conditions, such as tetralogy of Fallot, coarctation of the aorta, truncus arteriosus, and tricuspid atresia among others. Isolated VSD is the most common congenital cardiac lesion, accounting for approximately 20% of all CHD. Although most of the time the lesion represents a single defect, it can be multiple in 5% of cases. There is a slight female predominance in the occurrence of VSD. VSDs are classified by their location in the ventricular septum. Given the fact that the septum is a curved partition and not a straight plane, careful

imaging using thin sections in axial, vertical, and horizontal long-axis views is mandatory. These views allow the ventricular septum to be profiled in its entirety (Fig. 14). VSDs are classified into four types based on their location in the ventricular septum: perimembranous VSD, supracristal VSD, canal defect, and muscular or trabecular VSD. The perimembranous VSD is located in the subaortic region just below the crista supraventricularis. This is the most common type of VSD. The supracristal VSD is located below the pulmonary valve. This is a rare defect (5%). The canal defect is located in the inlet portion of the ventricular septum. It is associated with the spectrum of atrioventricular cushion defects frequently seen in trisomy 21 syndrome. The muscular or trabecular VSD can occur along any portion of the muscular ventricular septum and can be single or multiple. As is the case with other septation defects, the MR examination in patients with VSD is complementary to echocardiography and is mostly reserved for difficult cases, such as evaluation of aortic regurgitation as a result of prolapse of one of the aortic cusps into a subpulmonic VSD [13,19]. In addition, in the postoperative patient,

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

219

Fig. 6. Sagittal oblique turbo spin-echo T1-weighted (A) and cine gradient-recalled–echo bright-blood (B) images through aortic valve. These also provide a longitudinal (‘‘candy cane’’) view of the aortic arch. RA ¼ right atrium; RV ¼ right ventricle; LA ¼ left atrium; P ¼ right pulmonary artery; A ¼ ascending aorta.

Fig. 7. Vertical long-axis plane or two-chamber view. Cine gradient-recalled-echo image. LV ¼ left ventricle, LA ¼ left atrium; PA ¼ main pulmonary artery.

220

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

Fig. 8. Horizontal long-axis plane or four-chamber view. Dark-blood turbo spin-echo T1-weighted (A) and bright-blood cine gradient-recalled-echo (B) images. LV ¼ left ventricle; RV ¼ right ventricle; A ¼ aortic valve; LA ¼ left atrium; DA ¼ descending aorta.

the presence of flow across a patched defect can be evaluated effectively. A VSD patch can be difficult to visualize on black-blood images; however, on GRE sequences, it is seen as a flat area of low signal intensity. This represents the fibrous endothelialization of the surgical patch (Fig. 15). Patent ductus arteriosus Patent ductus arteriosus (PDA) represents a persistence of the distal portion of the primitive sixth arch and is an essential component of the fetal circulation. The ductus normally closes soon after birth. The factors responsible for ductus closure in infants are not clear, but it is known that

prostaglandin E1 is a potent dilator and that indomethacin induces ductal closure. Closure is often delayed in premature infants and in those with maternal rubella syndrome. On MRI, the PDA is seen as a tubular structure connecting the proximal descending aorta to the left pulmonary artery near its origin. The size and shape of the PDA are variable, and the direction and magnitude of the flow within it depend on the resistance between the pulmonary and systemic circuits. Even large PDAs can be difficult to image by MRI; thus, it is important to obtain images in multiple planes in the expected location of the defect. Bright-blood pool images can help to identify a small PDA by demonstrating turbulent flow into the pulmon-

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

221

Fig. 9. Short-axis plane. Turbo spin-echo T1-weighted image. RV ¼ right ventricle; LV ¼ left ventricle.

ary artery or aorta. MR angiography can help to estimate the degree of shunting across the defect.

Cyanotic shunt defects Cyanosis occurs when more than 5 g/dL of reduced hemoglobin is present in capillary blood. In central cyanosis, a portion of the systemic venous blood reaches the aorta without passing

through the lungs as a result of CHD. This can be caused by an admixture lesion (ie, univentricular heart) or by right-to-left shunting through a septation defect as a result of elevated pulmonary vascular resistance (Eisenmenger syndrome). Tricuspid atresia Tricuspid atresia is an uncommon congenital heart defect in which the tricuspid valve and

Fig. 10. Short-axis plane. Bright-blood cine gradient-recalled-echo image. RV ¼ right ventricle; LV ¼ left ventricle. Note left ventricular wall thickening.

222

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

Fig. 11. Atrial septal defect. Moderate-sized secundum atrial septal defect (arrow) is seen on this axial gradient-recalledecho image. RA ¼ right atrium; LA ¼ left atrium; A ¼ aortic root; OT ¼ right ventricular outflow tract.

inflow portion of the right ventricle are absent. Thus, there is no communication between the right atrium and right ventricle. Usually, the conus is the only identifiable portion of the right ventricle Blood reaches the right ventricle by means of a VSD. Tricuspid atresia has been classified as type I or II depending on its relation to the great vessels. In type I (70%), the great vessels are normally related, whereas they are transposed in type II (30% of cases) (Fig. 16). MR findings of tricuspid atresia are characteristic and include increased fat deposition in the right atrioventricular groove, absence of flow across the atretic valve, and blood flow across the VSD. Pulmonary stenosis can be an associated finding. The size of the right ventricle, ventricular septum, and pulmonary artery is variable. Tetralogy of Fallot Tetralogy of Fallot accounts for about 10% of congenital heart defects and is the most common congenital heart defect causing cyanosis. This anomaly is caused by conal maldevelopment, resulting in hypoplasia of the right ventricular infundibulum, which causes superior and leftward

displacement of the crista supraventricularis. As a result, there is narrowing of the right ventricular outflow tract associated with an overriding aorta and a perimembranous VSD (Fig. 17) The more severe the degree of pulmonary stenosis, the larger is the aorta. Frequently, the pulmonary valve is bicuspid and underdeveloped. In addition, peripheral pulmonary arterial stenosis and coronary artery origin anomalies can be present. A mirrorimage aortic arch is seen in approximately 25% of cases, and the incidence is higher in those patients with a greater degree of stenosis or pulmonary atresia. The aorta descends on the right, but it generally crosses to the left above the diaphragm. Echocardiography is the preferred modality for the evaluation of the heart chambers and valves. MRI can play an important role in the evaluation of the pulmonary arteries to determine their size and peripheral stenosis. The images should be carefully scrutinized for bronchial collaterals from the aorta to the pulmonary circulation, particularly if total surgical correction is being contemplated. Total repair of tetralogy of Fallot has improved long-term survival. The repair consists of placement of a transannular patch at the right ventricular outflow tract to relieve obstruction and closure

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

223

Fig. 12. Partial anomalous venous return. Patient suspected of having a sinus venosus atrial septal defect (ASD) on echocardiography. (A) Axial gradient-recalled-echo image demonstrates right atrial and right ventricular volume overload but no evidence of ASD. (B, C) Two images from gadolinium-enhanced MR angiography depict the left upper lobe vein draining into the innominate vein (arrow) and the right upper lobe vein draining directly to the superior vena cava (arrow).

224

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

Fig. 12 (continued )

of the VSD (Fig. 18) Refinements in surgical technique and anesthesia allow total repair early in life, obviating palliative shunts in most cases. Postoperative complications after total repair of tetralogy of Fallot include aneurysmal dilatation of the outflow patch, residual pulmonary insufficiency, and residual VSD. Residual VSD appears

as a signal void in the area of the VSD patch. These sequela may lead to volume overload and predispose to right ventricular failure and arrhythmias, which are risk factors for sudden death [3,20,21]. Pulmonary atresia In pulmonary atresia with an intact ventricular septum, there is a discontinuity between the right ventricular outflow tract and the main pulmonary artery. The right and left pulmonary arteries, which may or may not be confluent, are supplied by either a PDA or systemic bronchial and intercostal arteries, which act as collateral vessels to perfuse the lungs. The identification of these collateral vessels as well as the evaluation of their number and size is of crucial importance for surgical planning. The right ventricle is typically small. Truncus arteriosus

Fig. 13. Eisenmenger’s syndrome caused by long-standing shunt from an atrial septal defect. Axial gradientrecalled-echo image demonstrates enlarged central pulmonary arteries and slow turbulent flow manifested by low signal intensity in the central branches.

Truncus arteriosus is the result of the absence of truncoconal septation and represents 1% to 3% of congenital heart defects. Anatomically, it consists of a single truncal vessel arising from the heart and supplying blood to the aorta and pulmonary arteries. The truncal vessel receives blood from both ventricles via a high VSD, which is an integral part of the defect. Frequently, the single semilunar valve or truncal valve may be malformed, with the number of cusps varying from two to six. This can result in stenosis or trun-

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

225

Fig. 14. Muscular ventricular septal defect. (A) Axial T1-weighted image shows the septal defect. (B) Long-axis oblique image depicts the muscular defect (curved arrow) in its entirety.

cal insufficiency. Depending on the anatomy of the pulmonary arteries, several anatomic types have been described. Type I, the most frequently seen, has a common pulmonary trunk arising from the posterolateral aspect of the truncal vessel; the trunk then divides into corresponding left and right pulmonary branches. Type II is characterized by pulmonary arteries that arise adjacent to one another from the truncus. Type III is characterized by a variable origin of the pulmonary arteries. Both arteries can arise separately from the sides of the trunk. Alternatively, one lung

can be perfused by a true pulmonary artery arising from the trunk, whereas the other lung is perfused by a systemic branch that may originate from a patent ductus, aortic arch, or descending aorta. The major hemodynamic consequences of truncus arteriosus are pulmonary hypertension, ventricular volume overload from increased pulmonary flow, truncal insufficiency, and systemic arterial desaturation. The echocardiogram is usually diagnostic, and the presence and degree of truncal insufficiency can be assessed by Doppler echocardiography. MRI imaging can be

226

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

Fig. 15. Ventricular septal defect patch placement. (A) Four-chamber cine gradient-recalled–echo image demonstrating low signal in the subaortic septum from the patch (arrowhead). (B) A small amount of shunting can be seen across the patch at a slightly lower level (arrow). Note marked right atrial enlargement from tricuspid insufficiency.

particularly helpful in identifying the origin and branching pattern of the pulmonary arteries as well as in the postoperative follow-up of these patients (Fig. 19). Dextro-transposition of the great arteries Transposition of the great arteries is characterized by an abnormal origin of the great vessels. The pulmonary artery arises from the left ventricle, and

the aorta arises from the morphologic systemic right ventricle. This anomaly accounts for approximately 8% of congenital cardiac malformations and has a slight male predominance. Dextro (D)transposition implies that the aorta is positioned anterior and to the right of the pulmonary artery. In approximately 40% of patients, there is a septal defect, usually a VSD. As a result of this anatomic arrangement, the two largely independent circulations (pulmonary and systemic) exist in parallel,

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

227

Fig. 16. Type II tricuspid atresia. Axial gradient-recalled-echo image demonstrating large interatrial communication (arrowhead) and single ventricle (SV). Note asymmetry of pulmonary vessel size in this patient with pulmonary atresia and right-sided Blalock-Taussig anastomosis.

and survival depends on bidirectional shunting between the two sides of the heart. Axial MR images easily demonstrate the aorta to the right of the pulmonary artery. Because of its location above the right ventricular infundibulum, the aortic valve is seen residing at a higher level than the pulmonary valve. The morphology of the right and left ventricle can be clearly depicted on oblique images (Fig. 20). In general, MRI has a limited role in the diagnosis of D-transposition. MRI

has a definitive role in the postoperative evaluation of these patients, however. Before the advent of the arterial switch or Jatene operation, patients with dextro-transposition of the great arteries (DTGV) underwent correction at the atrial level. The two techniques used to repair D-TGV were the Mustard technique, which used pericardial tissue in the reparative baffle, and the Senning technique, which was based on infolding of the atrial walls (Fig. 21). Most patients who undergo repair

Fig. 17. Tetralogy of Fallot. (A) Half-Fourier rapid acquisition with relaxation enhancement axial image shows muscular hypertrophy of the right ventricular infundibulum (OT) and a right-sided aorta (DA). (B) Axial cine gradientrecalled–echo image at a lower level depicts a large perimembranous ventricular septal defect (arrow).

228

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

Fig. 18. Repaired tetralogy of Fallot. (A) Long-axis gradient-recalled-echo (GRE) image depicting wide open right ventricular outflow tract (OT) underneath a surgical patch (arrow). (B) GRE image in the vertical long-axis plane in another patient after total repair of tetralogy of Fallot demonstrating patent outflow patch (arrowheads) and mild turbulence across the pulmonary valve (arrow).

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

229

Fig. 19. Truncus arteriosus repair. Axial T1-weighted image in a patient with type I truncus arteriosus status. After surgery, the aortic tract (A) and pulmonary outflow tract (PA) show normal flow.

at the atrial level develop complications. The most common complication is narrowing at the level of the superior limb of the baffle. Leak of the baffle can occur but is less common than stenosis. Both can lead to right ventricular failure. Levo-transposition of the great arteries Levo-transposition of the great arteries (L-TGA) represents a combination of atrioventricular and ventriculoarterial discordance and accounts for approximately 1% of CHD. The pulmonary and systemic circuits are in series and not in parallel as in D-TGV. Uncomplicated L-TGA (totally corrected) is not an admixture lesion; thus, patients may be asymptomatic. Associated intracardiac defects are common with L-TGV, however. A VSD can be seen in up to 75% of cases (Fig. 22). Pulmonary stenosis, either valvular or subvalvular, is also frequently associated. MRI of palliative procedures The most commonly encountered extracardiac palliative shunts are the Glenn and modified Blalock-Taussig shunts. MRI can be used instead of angiography to determine shunt patency.

Fig. 20. Dextro-transposition of the great vessels. (A) Axial half-Fourier rapid acquisition with relaxation enhancement image showing the ascending aorta (AA) anterior and to the right of the main pulmonary artery (PA). (B) Oblique MR angiography (left anterior oblique equivalent) shows the aorta connected to the right ventricle (RV), whereas the posterior pulmonary artery is attached to the left ventricle (LV). Note that the aortic valve lies at a slightly higher level than the pulmonary valve. (Courtesy of Andrew Landes, MD, Maine Medical Center, Portland, ME.)

230

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

Blalock-Taussig shunt The Blalock-Taussig shunt is an end-to-side anastomosis of the subclavian artery and the pulmonary artery. This shunt originally was performed on the side opposite the aortic arch (Fig. 23). The more recent use of Gortex (ie, modified Blalock-Taussig shunt) allows placement of the shunt on either side of the aorta without sacrifice of the subclavian artery. Glenn shunt

Fig. 20 (continued )

The Glenn shunt is an end-to-end anastomosis of the superior vena cava to the right pulmonary artery. The modified or ‘‘bilateral Glenn anastomosis’’ is a variation in which there is an end-toside anastomosis of the superior vena cava to the right pulmonary artery, thereby maintaining continuity of both pulmonary arteries. Several complications have been described in the Glenn anastomosis, most commonly, a progressive decrease in perfusion of the right lung (particularly the right upper lobe) with the development of collateral vessels to other systemic veins.

Fig. 21. Dextro-transposition status after Senning procedure. Half-Fourier rapid acquisition with relaxation enhancement image demonstrates pulmonary veins (arrows) draining into the right side of the baffle, which connects to the systemic right ventricle. The superior vena cava (S) is seen draining into the anatomic left ventricle, which is now the pulmonary ventricle. (Courtesy of Andrew Landes, MD, Maine Medical Center, Portland, ME.)

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

231

Fig. 23. Blalock-Taussig anastomosis for levo-transposition of the great arteries with pulmonary atresia. (A) Frontal aortogram demonstrates a large right subclavian artery (Sc) anastomosed to the right pulmonary artery (RP). Note calcified pulmonary artery walls from longstanding pulmonary arterial hypertension. (B) MR angiography demonstrating the right innominate artery (RIA). (C) At a lower level, the right subclavian artery can be seen as it anastomoses to the right pulmonary artery (arrow). AA ¼ ascending aorta; PA ¼ main pulmonary artery. Fig. 22. Levo-transposition of the great vessels. (A) Gradient-recalled-echo image demonstrating rudimentary right ventricular chamber (rv) underneath aorta. A large ventricular septal defect (arrow) can also be seen. LV ¼ left ventricle. (B) Half-Fourier rapid acquisition with relaxation enhancement coronal image in another patient shows a univentricular heart and left-sided aorta (AA). Note high signal in main pulmonary artery (PA) from pulmonary hypertension.

Because of this complication, the azygous vein is usually routinely ligated at the time the shunt is created. In addition, intrapulmonary arteriovenous fistulas can develop, particularly in the right lower lobe, causing cyanosis and clinical deterioration (Fig. 24) [22]. The Potts’ shunt (descending aorta to left pulmonary artery) (Fig. 25) and Waterston-Cooley

232

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

the aorta is connected to the right pulmonary artery (Fig. 26).

Obstructive lesions Aortic stenosis

Fig. 23 (continued )

anastomosis (ascending aorta to right pulmonary artery) have been largely abandoned because of the frequent development of pulmonary arterial hypertension and architectural distortion of the pulmonary arteries. The Waterston-Cooley shunt is an aortopulmonary anastomosis, where the posterior wall of

Valvular lesions can obstruct either the semilunar or atrioventricular valves. The most common form of valvular heart disease is aortic stenosis, usually caused by a bicuspid aortic valve. Less commonly, it is caused by a unicuspid and unicommissural aortic valve. Most children with bicuspid aortic valves have no symptoms and normal chest radiographs. In some cases, however, an enlarged ascending aorta from poststenotic jetting can be identified. Valvular lesions can occur in isolation, or they can be associated with more complex defects. Black–blood pool images generally demonstrate enlargement of the aortic root as a result of poststenotic dilatation. Unless the valve leaflets are significantly thickened, they are not visible on black-blood imaging techniques. Associated left ventricular hypertrophy may also be visible. Actual visualization of the valve requires GRE sequences, where a ‘‘negative’’ jet is seen crossing

Fig. 24. Glenn shunt for tricuspid atresia status. Note large chest wall and mediastinal (arrows) as well as pulmonary (arrowheads) collaterals.

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

233

Fig. 26. Waterston-Cooley anastomosis in a patient with pulmonary atresia. Gadolinium-enhanced MR angiography depicts stenosis of the anastomotic site between the back of the aorta and the right pulmonary artery (arrow). Fig. 25. Potts’ anastomosis. Gadolinium-enhanced MR angiography demonstrates widely patent anastomosis (arrow) between the descending aorta and left pulmonary artery.

the stenotic valve during systole. (Fig. 27). Quantification of the stenotic lesion can be performed by calculating the Vmax in the stenotic jet in planes either perpendicular or parallel to the direction of flow or by using the velocity-encoded cine MR techniques [23].

Pulmonary valvular stenosis Pulmonary valvular stenosis is the most common form of congenital obstruction of the right heart. As in other forms of valvular heart disease, it can occur in isolation or be associated with complex congenital defects. It is usually the result of a dome-shaped bicuspid valve; rarely, it is caused by a dysplastic valve. The thickened valve restricts the amount of flow during systole because of fusion of the commissures, which form a central orifice that may be eccentric. Changes of right ventricular hypertrophy may develop if there is a large gradient across the stenotic valve orifice. Poststenotic dilatation of the main and left pulmonary arteries is a classic finding that can be seen on plain radiographs, angiography, and cross-sectional imaging, such as MRI.

Fig. 27. Aortic stenosis. Left anterior oblique gradientrecalled-echo image demonstrating turbulence across the aortic valve (arrowhead) as well as poststenotic dilatation of the ascending aorta.

234

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

Fig. 28. Aortic stenosis postoperative complication. Oblique four-chamber gradient-recalled-echo image after aortic valve replacement. Circumferential dehiscence is visible, with separation of the prosthesis from the aortic annulus creating a saccular space (S) that encircles the valve. A ¼ aortic root.

Postoperative evaluation MRI is an ideal method for the noninvasive follow-up of patients after valvuloplasty or valvular surgery. With the exception of the mitral StarrEdwards pre-6000 series cage-and-ball valve, virtually all valvular prosthesis can be safely imaged [10]. Signal loss around the prosthesis on GRE images can degrade the area next to the prosthesis, obscuring small lesions, such as prosthetic vegetations. Visualization of other complications, such as perivalvular abscess and dehiscence, can be accomplished effectively, however (Fig. 28). In addition, velocity mapping proximal and distal to the prosthesis can be performed accurately.

Summary MRI has become an important imaging tool that complements echocardiography in the noninvasive evaluation of congenital heart defects. It can play a crucial role in diagnosis by assessing anatomic and functional features in CHD and identifying complications and postoperative sequelae. The performance and application of cardiac MRI require not only knowledge of the clinical question that needs to be addressed but knowl-

edge of the anatomic characteristics of a variety of congenital heart lesions. A knowledge of the advantages and disadvantages of the different imaging sequences also is important so as to optimize and expedite the examination.

References [1] Hoffman JI. Incidence of congenital heart disease: I. Postnatal incidence. Pediatr Cardiol 1995;16:103–13. [2] Kaplan S. Congenital heart disease in adolescents and adults—neonatal and post-operative history across age groups. Cardiol Clin 1993;11:543–56. [3] Roest AA, Helbing WA, van der Wall EE. Postoperative evaluation of congenital heart disease by magnetic resonance imaging. J Magn Reson Imaging 1999;10:656–66. [4] Hirsch R, Kilner PJ, Connelly MS, Redington AN, St. John Sutton MG, Somerville J. Diagnosis in adults and adolescents with congenital heart disease. prospective assessment of individual and combined roles of MRI and TEE. Circulation 1994;990: 2937–51. [5] Choe YH, Kim YM, Han BK, Park KG, Lee HJ. MR imaging in the morphologic diagnosis of congenital heart disease. Radiographics 1997;17:403–22. [6] Kersting Sommerhoff BA, Seelos KC, Hardy C, et al. Evaluation of surgical procedures for cyanotic

F.R. Gutierrez et al / Magn Reson Imaging Clin N Am 10 (2002) 209–235

[7] [8]

[9]

[10]

[11]

[12] [13]

[14]

[15]

congenital heart disease by using magnetic resonance imaging. AJR Am J Roentgenol 1990;17: 259–66. Mezrich R, Reichek N, Kressel H. ECG effects in high-field MR imaging. Radiology 1985;157:219. Shellock FG, Kamal E. Magnetic resonance procedure and patients with biomedical implants, materials, and devices. In: Magnetic resonance: bioeffects, safety, and patient management. Philadelphia: Lippincott, Williams & Wilkins; 1996. p. 127–8. Shellock FG, Kanal E. Policies, guidelines, and recommendations for MR imaging safety and patient management. J Magn Reson Imaging 1991;1:97–101. Shellock FG. MR imaging of metallic implants and materials: a compilation of the literature. AJR Am J Roentgenol 1988;151:811–4. Higgins CB. Congenital heart disease. In: Higgins CB, Hricak H, Helms CA, editors. Magnetic resonance imaging of the body. 3rd edition. Philadelphia: Lippincott-Raven; 1997. p. 461–518. Boxt LM. How to perform cardiac MR imaging. Magn Reson Imaging Clin North Am 1996;4:191–216. Didier D, Ratib O, Beghetti M, Oberhaensli I, Friedli B. Morphologic and functional evaluation of congenital heart disease by magnetic resonance imaging. Radiographics 2000;20:1279. Gutierrez FR, Canter CE, Mirowitz SA. MR appearance of congenital heart defects. In: Gutierrez FR, Brown JJ, Mirowitz SA, editors. Cardiovascular magnetic resonance imaging. St. Louis: Mosby-Year Book; 1992. p. 72–83. Mohladdin RH, Pennel DJ. MR blood measurement. Clinical application in the heart and circulation. Cardiol Clin 1998;16:161–87.

235

[16] Boxt LM. MR imaging of congenital heart disease. Magn Reson Imaging Clin North Am 1996;4: 327–59. [17] Didier D, Higgins CB. Estimation of pulmonary vascular resistance by MRI in patients with congenital cardiovascular lesions. AJR Am J Roentgenol 1986;146:919–24. [18] Hundley WG, Li HF, Lange RA. Assessment of leftto-right intracardiac shunting by velocity-encoded, phase difference magnetic resonance imaging. A comparison with oximetric and indicator dilution techniques. Circulation 1995;91:2955–60. [19] Rebergen SA, Niezen RA, Helbing WA, van der Wall EE, de Roos A. Cine gradient echo MR imaging and MR velocity mapping in the evaluation of congenital heart disease. Radiographics 1996;16:467–81. [20] Marie PY, Marcon F, Brunotte F, et al. Right ventricular overload and induced sustained ventricular tachycardia in operatively ‘‘repaired’’ tetralogy of Fallot. Am J Cardiol 1992;69:785–9. [21] Rebergen SA, Chin JG, Ottenkamp J, van der Wall EE, de Roos A. Pulmonary regurgitation in the late postoperative follow-up of tetralogy of Fallot. Volumetric quantitation by nuclear magnetic resonance velocity mapping. Circulation 1993;88: 2257–66. [22] Amplatz K, Moller JH. Radiology of congenital heart disease. St. Louis: Mosby-Year Book;1993. [23] Eichenberger AC, Jenni R, von Schultess GK. Aortic valve pressure gradients in patients with aortic valve stenosis: quantification with velocityencoded cine MR imaging. AJR Am J Roentgenol 1993;160:971–7.