|Year : 2018 | Volume
| Issue : 2 | Page : 180-187
Role of cardiac MRI in diagnosis of congenital heart diseases
Mohamed A Nasr1, Medhat M Eldosoky1, Hany H Lotfy2, Noha H Behery3, Shaheen A Dabour4
1 Radiology Department, Faculty of Medicine, Benha University, Egypt
2 Radiology Department, Military Medical Academy
3 Radiology Department, Faculty of Medicine, Cairo University
4 Department of Pediarics, Faculty of Medicine, Benha University, Egypt
|Date of Submission||16-Jul-2016|
|Date of Acceptance||30-Mar-2017|
|Date of Web Publication||17-Aug-2018|
Dr. Mohamed A Nasr
10th El Shaheed Ahmed Hamdy Street, 13772, Begam, Qalyobia, Egypt
Source of Support: None, Conflict of Interest: None
Background Patients with congenital heart disease (CHD) are a challenge for imagers, since CHD requires a profound knowledge of the morphologic and functional characteristics of a broad range of congenital heart defects.
Patients and methods 39 patients with CHD underwent MRI. In all patients, the abnormalities were demonstrated previously by echocardiography and 12 of them underwent CTA before MRI. The true diagnosis was considered to be the findings shown by 2D echocardiography except for extracardiac anomalies.
Results ToF was the commonest CHD evaluated by MRI. The other cases in this study are variety of intra- and extra-cardiac anomalies with some post-operative cases. Cardiac MRI is considered as a valuable modality for evaluation of CHD as compared to other modalities it has much to offer by (a) generating high-resolution morphological images (b) offering quantitative information of the severity of regurgitant or stenotic lesions and (c) quantification of shunt.
Conclusion Cardiac MRI provides a powerful tool, giving anatomic and haemodynamic information that echocardiography and catheterization alone do not provide. Finally, cardiovascular MR surpasses both catheterization and echo in its ability to create high resolution, three-dimentional reconstructions of complex CHD.
Keywords: cardiac MRI, congenital heart diseases, cardiac imaging
|How to cite this article:|
Nasr MA, Eldosoky MM, Lotfy HH, Behery NH, Dabour SA. Role of cardiac MRI in diagnosis of congenital heart diseases. Benha Med J 2018;35:180-7
|How to cite this URL:|
Nasr MA, Eldosoky MM, Lotfy HH, Behery NH, Dabour SA. Role of cardiac MRI in diagnosis of congenital heart diseases. Benha Med J [serial online] 2018 [cited 2018 Nov 19];35:180-7. Available from: http://www.bmfj.eg.net/text.asp?2018/35/2/180/239195
| Introduction|| |
Patients with congenital heart disease (CHD) are a challenge for imagers, as CHD requires a profound knowledge of the morphologic and functional characteristics of a broad range of congenital heart defects. Moreover, complex CHD often involves complex palliative or corrective surgery that alters the ‘normal’ heart anatomy and cardiac function profoundly .
The number of patients reaching adulthood after correction or palliation of complex CHD is increasing significantly, thereby creating a whole new group of patients with complex chronic cardiac disorders .
According to the American Heart Association, ∼35 000 babies are born each year with some type of congenital heart defect. CHD is responsible for more deaths in the first year of life than any other birth defect .
Traditionally, imaging of CHD has been a domain of cardiac catheterizations and echocardiography. The last 10 years have seen the rise of MRI and computed tomography as accepted imaging modalities for CHD. Especially MRI has been the source of important insights into individualized pathophysiologic changes in CHD for both morphologic and functional aspects .
Cardiac MRI has become a clinically useful supplement to echo and conventional radiography angiography in the diagnostic work-up of patients with CHD. Three-dimensional sequences are capable of depicting both intracardiac and extracardiac structures with high accuracy in adults and adolescents .
Echocardiography is currently used as the initial noninvasive imaging study for almost all patients with known or suspected CHD. MRI is unlikely to replace echocardiography as the first diagnostic procedure because of the portability, universal availability, and low cost. MRI can demonstrate cardiovascular anatomy without the limitation of acoustic windows or ultrasound penetration of the body. Therefore, the morphology of some regions, such as the supracardiac region and the posterior aspect of the heart, can be more clearly shown with MRI than with echocardiography. Furthermore, MRI can provide tomographic images in any imaging plane and with a wide field of view. Clearly, in many cases the diagnostic capabilities of MRI and echocardiography are complementary rather than competitive and patients may benefit from having both studies .
As surgical procedures and medical management of CHD improve, more patients are surviving into adulthood. These adult CHD patients may suffer from reduced cardiac function or complications related to their surgical procedure. MRI is particularly well suited to evaluation of adult CHD. Sedation generally is not required, and the slower heart rates of adults compared with those of children allow more images to be obtained per cardiac cycle. Moreover, transthoracic echo in adult CHD patients often suffers from poor acoustic penetration through the thoracic cage and mediastinal scar tissue . CMR already does play an ever-increasing role in the management of CHD patients.
| Materials and methods|| |
Totally, 39 patients with an age range 6 months to 27 years with CHD underwent MRI at El-Qasr El Ainy Hospital, Department of Radiology, Egypt, and Hospital of Gonesse, France, from January 2013 to July 2016. The study was approved by the Research Ethical Committee and an informed consent was obtained from each participant before enrollment in the study. There were 23 male and 16 female patients. In all patients, the abnormalities were demonstrated previously by echocardiography and 12 of them underwent computed tomography angiography before MRI. The true diagnosis was considered to be the findings shown by two-dimensional echocardiography excepting extracardiac anomalies cases. The patients were referred from the Cardiology Department, Kasr El Aini Hospital, The Children Hospital (Abu El Reesh), Egypt, and Hospital of Gonesse, France.
Magnetic resonance imager
A Philips Gyroscan Intera (Philips Healthcare, Amsterdam, Netherlands) (1.5 T) super conducting magnet was used in the Radiology Department, Kasr El Aini Hospital, Cairo University.
A General Electric Optima MR450w 1.5 T conducting magnet (General Electric Healthcare, Chicago, Illinois, USA) was used in the Radiology Department, Hospital of Gonesse, France.
A detailed history was elicited from each patient including principal symptoms and signs, echocardiographic and cardiac catheterization data, and operative status. For all patients in this study, MR-compatible electrocardiographic leads were placed on the anterior chest wall before imaging and attached to the MRI unit for electrocardiographic gating. For most sequences, electrocardiographic triggering was used to synchronize imaging with the onset of systole and offset cardiac motion and match each image to the desired cardiac phase.
The referring physician and anesthetist were consulted for the type of sedation (general anesthetic sedation, deep sedation, or conscious sedation) for every case. The sedation techniques included medication by oral chloral hydrate oral.
The exam started with an integrated body array coil. Scans were performed generally using nonbreath-holding techniques, with adult and old children cases undergoing breath-holding scan techniques based on precise monitoring of diaphragmatic motion.
Cardiac MRI protocol
The MRI protocol commenced with a localizer using Trufi (steady-state free precession) sequence. A list of protocol is given as [Table 1]. Axial and coronal scans of 10 mm thickness using Trufi were obtained with acquisition extending from the level of aortic arch to below the diaphragm including the inferior venal cava and hepatic veins. It was useful in demonstrating ventricular and atrial septal defects (ASDs) as well as providing anatomical landmark for deriving oblique sections, subsequently. From the localizer, vertical long axis, short axis, and horizontal long axis were obtained. The anterior slices during planning of horizontal long axis generated a left ventricular (LV) outflow tract image. Functional analysis was performed using a combination of Cine Trufi (steady-state free precession), Cine Flash (gradient-echo), and Cine phase-contrast sequences. In few cases a three-point technique determined the right ventricular (RV) outflow tract. For evaluation of aorta, pulmonary trunk, coronal view was useful.
|Table 1 Suggested imaging protocols for given conditions for abbreviations see main text |
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| Results|| |
The study comprised 43 cardiac MRI studies performed on 39 patients with CHD; two studies failed due to technical factors. The age range was 6 months to 27 years with average 9.6±6.4 years. There were 23 male and 16 female patients ([Table 2]). Nine studies were performed in seven patients with Tetralogy of Fallot (ToF), including six studies done on cases before and after surgery. In this study, ToF was the commonest CHD evaluated by MRI. The other cases in this study consisted of six cases of transposition of great arteries (D-TGA), two cases of L-TGA, two cases of ventricular septal defect (VSD), four cases of bicuspid aortic valve, one case of hypolastic arch, two cases of single ventricle, three cases of pulmonary stenosis, one case of coarctation of aorta, five cases of ebstien anomaly, five cases of ASD, one case of aberrant right subclavian, and two cases of double outlet RV ([Table 3]). Of 12 patients had pre-post and postoperative studies including rastelli operation, Blalock–Taussig, angioplasty of aortic arch and partial cavopulmonary connection ([Table 4]).
|Table 3 Classification of the patients according to the pathologic diagnosis|
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Data collection and image analysis
MRI were reviewed retrospectively by a panel of two radiologists. The images of each patient were analyzed to define cardiovascular anomalies. The morphological information comprised chamber and valve anatomy, structure and integrity of septum, alignment and caliber of outflow tracts, and atrioventricular connections. The functional information comprised quantification of flow across valves, outflow tract, and defects. Quantification of systemic and pulmonary flow was done in cases of septal defects. Cine imaging in horizontal long-axis provided dynamic information of the cardiac size, valve morphology, leaflet mobility, wall thickness, chamber size, flow jets, and outflow tracts. Cine imaging in vertical long-axis offered information on chambers size, septum anatomy, defect morphology, and aortopulmonary connections.
| Discussion|| |
Cardiac MRI is considered as a valuable modality for evaluation of CHD. Cardiac MRI has much to offer by (a) generating high-resolution morphological images, (b) offering quantitative information of the severity of regurgitant or stenotic lesions with peak velocity and flow measurements, and (c) quantification of shunt. The greatest challenge of cardiac MRI is motion artifact from the heart, adjacent vascular structures, and respiration . With the ongoing developments in gradient hardware and pulse sequence technology, imaging sequences that can ‘freeze’ the motion of the heart during the cardiac cycle is now available. Moreover, with the development of rapid pulse sequences, breath-hold imaging is facilitated, which is necessary to accommodate the wide range of motion the heart undergoes during respiration.
The indications for MRI in the evaluation of patients with CHD have been now determined. The major indications at the moment includes the following: (a) segmental description of cardiac anomalies; (b) evaluation of thoracic aortic anomalies; (c) noninvasive detection and quantification of shunts, stenoses, and regurgitations; (d) evaluation of conotruncal malformations and complex anomalies; (e) identification of pulmonary and systemic venous anomalies; and (f) postoperative studies.
ASD occur in 10% of CHD and are the most common type of CHD to present in adult life. Three main types of ASD are commonly seen: secundum (in middle of atrial septum), which is the commonest; sinus venosus (at junction of superior vena cava and right atrium superiorly); and primum (in inferior portion of atrial septum, near atrioventricular valves). MRI shows a defect on two adjacent axial images or during multiple phases of the cardiac cycle during cine imaging at one anatomic level and effects of left-to-right shunting in form of right atrial and ventricular volume overload. The sensitivity and specificity of MRI for the diagnosis of ASD are both greater than 90%. The defect is best seen in horizontal long axial and oblique sagittal sections, as was evident in this study. To overcome the limitation of normal thinning at region of secundum, the defect should be identified in two or more sections reinforced by correlation with right-sided volume loading. The dilated right chambers rotate the heart into the left chest across the midline with interventricular septum nearly in the coronal plane. An important finding in ASD presenting in adults is pulmonary hypertension, which occurs in 40% cases, mostly due to increased flow. Mitral valve prolapse and mitral regurgitation occurs occasionally.
VSD is a common CHD that is typically classified into membranous (70–80%), muscular (10%), endocrinal cushion defects (5–10%), and conal (5%). MRI findings include a defect in the above locations, increased vascularity with a 2 : 1 or greater shunt, cardiomegaly and enlarged left atrium. While 30–40% of patients close spontaneously, infants can present with congenital heart failure at 2–3 months. Surgical approaches advocated are closure in membranous type and ventriculotomy in muscular type. The defect is best seen in axial and coronal images. Small defects that are difficult to detect can be better delineated by angulated sections and reconstructions. Cine gradient-echo images can differentiate left to right, right to left, and bidirectional shunts. In this study, there were two patients with a VSD. The defect was identified correctly in all two on horizontal and vertical long-axis views. The dilatation and hypertrophy of RV was identified on axial images in all cases ([Figure 1]) .
|Figure 1 Trufi (steady-state free precession) sequence axial and showing membranous ventricular septal defect in 8-year-old male.|
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ToF is the commonest cyanotic CHD. Described first by Stensen, a Danish anatomist in 1671, and subsequently by Fallot, a French physician in 1888, it is a combination of overriding of aorta, VSD, infundibular pulmonary stenosis, and RV hypertrophy. MRI demonstrates all findings in this condition, including infundibular stenosis; VSD ([Figure 2]) , which is either membranous or muscular beneath crista; pulmonary valve anomalies like bi/unicommissural valves, large right pulmonary artery, and right aortic arch. Among the right aortic arch, 90% present with mirror imaging branching of the great vessels, while the remaining 10% have an aberrant left subclavian artery. Associated anomalies that can occur include major aortopulmonary collateral arteries, peripheral pulmonary artery coarctation, and coronary artery anomalies like anomalous left anterior descending artery arising from right coronary artery.
|Figure 2 Tetralogy of Fallot. Cardiac MRI with steady-state free precession showing (a) oblique projection with the aorta overriding a malalignment ventricular septal defect (asterisk), (b) sagittal projection with severe infundibular and pulmonary valve stenosis, and (c) three-dimensional mri angiography (MRA), axial view, with severe hypoplasia of the main and right pulmonary artery, and the presence of right aortic arch .|
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MRI is also excellent for evaluating both palliative and corrective surgical repair that have effectively resulted in improved long-term survival . Palliative shunt corrections between the systemic and pulmonary circulations include Blalock–Taussig shunt (described first in1944) between the subclavian artery to pulmonary artery, Waterston shunt connecting descending aorta to left pulmonary artery, and Pott’s shunt linking ascending aorta to right pulmonary artery. However, due to the fixed size of shunt conduit to right pulmonary artery, children often outgrow them 2 years after the procedure, and definitive repair is usually performed at 5–7 years, which consists of pericardial patching of the VSD and wide reconstruction of the RV outflow tract to relieve the pulmonary outflow obstruction. Corrective repair entails relieving the RV outflow obstruction with reconstruction and patch closure of the VSD in corrective surgery. During follow-up period, MRI can provide useful information on adequacy of pulmonary circulation and the presence of pulmonary regurgitation. Pulmonary regurgitation is a complication of surgical reconstruction of the outflow tract that does not have a valvular apparatus. Consequent to regurgitation, there is an increase in end-diastolic volume (EDV) of the RV, which on MRI is seen as RV outflow dilatation and RV hypertrophy .
Coarctation of the aorta is a congenital narrowing of the aorta, occurring just distal to the left subclavian artery. The narrowing is proximal, adjacent, or distal to the site of entry of the ductus arteriosus, or insertion of the ligamentum arteriosum. There are two presentations: infantile and adult. The infantile type is associated with a VSD in 50% of cases and a patent ductus arteriosus in 30% that supplies blood to the descending aorta beyond the area of narrowing. The adult type presents with systemic hypertension, aortic dissection, stroke, heart failure, and endocarditis. MRI is useful in diagnosis of coarctation, in presurgical planning, and during after surgical follow-up . Preoperatively, MRI offers useful information on location, extent, and severity of the narrowed aortic segment, besides mapping the collateral pathways. The coarctation segment is best seen on oblique coronal and sagittal images. Changes in arch of aorta like hyperplasia of distal aortic arch and proximal descending aorta, shortened AP dimensions, cepahalad extension of arch, and curved and ‘captured’ origin of left subclavian artery can be demonstrated. The collateral circuits of coarctation seen on MRI include dilation of both subclavian, internal mammary, intercostals, dorsal scapular, and epigastric arteries. Cine PC imaging quantifies the pressure gradient across the coarctation.
Single ventricle (SV) belongs to a category of cyanotic malformations, termed admixture lesions, because of mixing of venous and arterial blood within the heart and great arteries. In this condition, both atria and their AV valves communicate with a single ventricle . It is also synonymously called as primitive ventricle, common ventricle, double or single inlet left or RV, cor biloculare and triloculare. There are three cardinal morphologic characteristics of single ventricle: (a) most commonly, of a LV type, (b) RV type, and (c) rarely a common ventricle type with a rudimentary septum in the ventricular cavity.
The Fontan surgical procedure and its modifications are designed to direct total systemic venous return to the lungs. It is used for the treatment of single ventricle, and a number of other complex cardiac malformations like tricuspid atresia . Currently, the most frequently used type of Fontan operation involves the installment of a total cavopulmonary connection, excluding the RV.
Truncus arteriosus (TA) is an uncommon condition, occurs in 2% of CHD, and presents with common aorticopulmonary trunk, due to a failure of splitting of the primitive common TA into aorta and pulmonary artery by a spiral septum. It is associated with a large, high riding VSD and an ASD can occur in about 20% of cases. The common truncal valve typically has three cusps in 70% of cases, but can vary from two to six, with possible stenosis or insufficiency at this valve. Associated cardiac abnormalities include a right aortic arch, coronary artery origin anomalies, and persistent left superior vena cava. The Rastelli procedure is the treatment of choice, with reconstruction of pulmonary outflow tract through a RV to pulmonary artery synthetic graft. TA is classified into four types. Type 1 (pseudopulmonary trunk) is the commonest, accounting for 70% of cases and denotes a common truncal vessel giving off a well formed main pulmonary artery which bifurcates into right and left pulmonary arteries. Type 2 has separate left and right pulmonary arteries arising directly from dorsal surface of the ascending truncal vessel. Type 3 has separate left and right pulmonary arteries arising from lateral surface of the ascending portion of the truncal vessel. Type 4 is essentially called pseudotruncus and occurs due to pulmonary conal agenesis, rather than failure of truncal septation. There is no RV to pulmonary artery communication. In this study, there was one case of TA, exhibiting type 1/pseudopulmonary trunk features B ([Figure 3]).
|Figure 3 Classification of the patients according to the pathologic diagnosis. VSD, ventricular septal defect.|
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In a study done by Liping et al.  a total of 19 healthy children (mean: 10.6±2.8 years, 11 males and nine females) were prospectively enrolled in this study to assess the feasibility, accuracy, and reproducibility of a rapid full volume acquisition strategy using real-time (RT) three-dimensional echocardiography (3DE) for measurement of LV volumes, mass, single ventricle (SV), and ejection fraction in children. It was found that measurements of LV volumes by RT 3DE were slightly but consistently smaller than those of MRI (37.9±12.8 vs. 39.7±13.6 ml for ESV; 97.5±34.6 vs. 104.4±38.9 ml for EDV; and 59.6±22.4 vs. 64.6±26.9 ml for SV]. This prospective study demonstrated that RT 3DE measurements of LV end-systolic volume, EDV, mass, SV, and ejection fraction in children using rapid full volume acquisition strategy are feasible, accurate, and reproducible and are comparable with MRI measurements.
Sandstede et al.  examined possible age-specific and sex-specific differences in the function and the mass of the left and RVs in 36 healthy volunteers (18 men and 18 women, age range between 20 and 60) using steady-state free precession MRI. With age, there was a significant decrease in both absolute and normalized LV and RV chamber volumes (per square meter body surface area). Sex-specific differences were found in RT and LT ventricle volumes (for men and women, respectively: LV EDV, 118±27 and 96±21 ml; LV ESV, 40±13 and 29±9 ml; RV EDV, 131±28 and 100±23 ml; RV ESV, 53±17 and 33±15 ml). MRI shows age-specific and sex-specific differences in cardiac function, and therefore the evaluation of cardiac function in patients should consider age-matched and sex-matched normative values.
In the current research, ventricular function was obtained for 29 patients using breath-hold balanced FFE in the short-axis plane. The white blood images in the adult population being able to withhold their breath yielded very clearly identified subendocardial borders of the ventricles, whereas in the pediatric group of patients, being unable to withhold their breath, the white blood images yielded hazy subendocardial outline in some cases. All the results were normal for age; no normalization to body surface area was done. This was in accordance to the previously mentioned studies done by Gutberlet et al. , Liping et al. , and Sandstede et al. , but in contrast to Hudsmith et al.  who stated that normalization of values to body surface area removed the statistical differences for LV volumes.
Our data showed that patients with septal defects with left-to-right shunt showed increase in the RV cardiac output. This was in agreement with Goitein et al.  who stated that in the presence of a left-to-right shunt, QLVSV will equal the QRVSV+Qshunt. The QLVSV/QRVSV ratio represents the severity of the shunt.
Few areas of difficulties are present inherently in cardiac MRI, which can be overcome by a series of measures . First, a vast number of imaging techniques are available and by experience the radiologist must choose the optimal set of MRI protocols to evaluate specific pediatric cardiac problems. Second, cardiac arrhythmias can interfere in magnetic resonance (MR) acquisition resulting in suboptimal and nonconclusive studies. Third, breath-hold sequences may be difficult to perform in a setting of infants with cyanosis and respiratory distress, adversely affecting the use of Trufi and other cine sequences. Fourth, distal pulmonary artery branch stenosis may not be delineated, a critical information during follow-up of cases with ToF. Notwithstanding the above, cardiac MRI has, however, emerged as an accurate method for the evaluation of structure and function of the heart.
| Conclusion|| |
Technical advances during the last decade have brought cardiovascular MR into the mainstream of noninvasive imaging for adult and pediatric patients with CHD. It provides a powerful tool, giving anatomic and haemodynamic information that echo and catheterization alone do not provide. Extracardiac anatomy can be delineated with high spatial resolution, intracardiac anatomy can be imaged in multiple planes, and functional assessment can be made accurately and with high reproducibility. Finally, cardiovascular MR surpasses both catheterization and echo in its ability to create high resolution, three-dimentional reconstructions of complex CHD. Other well established clinical applications of cardiovascular MR in patients with CHD include measurement of systemic and pulmonary blood flow, quantification of valve regurgitation, identification of myocardial ischemia and fibrosis, and tissue characterization. The most significant limitations of cardiovascular MR for CHD are the time and resources required to run a successful scan. A radiographer trained in CHD is necessary to expedite image planning in the setting of complex disease, often with the added technical challenges of the smaller structures and faster heart rates typical in pediatric patients. During both the acquisition and the reporting stages, a physician with comprehensive experience of the anatomy and physiology of CHD is required, to guide each scan appropriately. However, with this in place, cardiovascular MR gives a noninvasive, nonirradiative, comprehensive assessment of each patient’s morphologic and hemodynamic status, providing valuable decision support for life-long management.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4]