Magnetic resonance imaging at a high field strength of ventricular septal defects in infants

Magnetic resonance imaging at a high field strength has potential benefits for the study of the heart in infants, which is when most congenital heart disease presents. Seventeen infants with various anatomical types of ventricular septal defect were studied by this technique. Good quality, high resolution, images were obtained in every case. There were no major practical problems. The morphology of the defects in all 17 hearts was displayed in great detail. In some instances, the interpretation of the images resembled that of equivalent images from cross sectional echocardiography. But this new technique allowed imaging in planes that cannot be obtained by echocardiography. One particularly valuable plane gave a face on view of the inlet and trabecular components of the septum. This allowed very precise localisation of defects in these areas. The relation between the defects and the atrioventricular and arterial valves was exceptionally well shown in various different imaging planes. One patient in the series had multiple trabecular defects that were clearly shown. Magnetic resonance imaging gives detailed morphological information about ventricular septal defects.     

Morphological evaluation of atrioventricular septal defects by magnetic resonance imaging.

Twelve patients aged between 2 weeks and 22 months (median 6 weeks) with atrioventricular septal defects were examined with a 1.5 T, whole body, magnetic resonance imaging system. Ten patients had a common atrioventricular orifice (complete defect) while two patients had separate right and left valve orifices (partial defect). Associated cardiac malformations included the tetralogy of Fallot in two, isomerism of the right atrial appendages and pulmonary atresia in two, and right isomerism and double outlet right ventricle in one. All had previously been examined by cross sectional echocardiography. Eight subsequently had angiography and six underwent surgical correction. There was one operative death and three other deaths. Three of these patients underwent postmortem examinations. Small children and infants were scanned inside a 32 cm diameter head coil. Multiple electrocardiographically gated sections 5 mm thick, separated by 0.5 mm, were acquired using a spin echo sequence with echo time of 30 ms. A combination of standard and oblique imaging planes was used. Magnetic resonance imaging was more accurate than echocardiography in predicting the size of the ventricular component of the defect. It was also better than either echocardiography and angiography in identifying the presence of ventricular hypoplasia. All these findings were confirmed by surgical or postmortem examinations or both. Magnetic resonance imaging is capable of providing detailed morphological information in children with atrioventricular septal defects which is likely to be of value in their management.     

Morphological evaluation of atrioventricular septal defects by magnetic resonance imaging

Twelve patients aged between 2 weeks and 22 months (median 6 weeks) with atrioventricular septal defects were examined with a 1.5 T, whole body, magnetic resonance imaging system. Ten patients had a common atrioventricular orifice (complete defect) while two patients had separate right and left valve orifices (partial defect). Associated cardiac malformations included the tetralogy of Fallot in two, isomerism of the right atrial appendages and pulmonary atresia in two, and right isomerism and double outlet right ventricle in one. All had previously been examined by cross sectional echocardiography. Eight subsequently had angiography and six underwent surgical correction. There was one operative death and three other deaths. Three of these patients underwent postmortem examinations. Small children and infants were scanned inside a 32 cm diameter head coil. Multiple electrocardiographically gated sections 5 mm thick, separated by 0.5 mm, were acquired using a spin echo sequence with echo time of 30 ms. A combination of standard and oblique imaging planes was used. Magnetic resonance imaging was more accurate than echocardiography in predicting the size of the ventricular component of the defect. It was also better than either echocardiography and angiography in identifying the presence of ventricular hypoplasia. All these findings were confirmed by surgical or postmortem examinations or both. Magnetic resonance imaging is capable of providing detailed morphological information in children with atrioventricular septal defects which is likely to be of value in their management.     

Nuclear magnetic resonance in congenital cardiopathies in adults

Magnetic resonance imaging is a newly developed diagnostic technique recently used for the study of the cardiovascular system. One of the most promising fields of application for magnetic resonance is the study of congenital heart diseases. Since it offers high contrast and resolution tomographic images of the heart, this technique appears particularly suitable for the anatomic assessment of cardiovascular malformations. In order to evaluate the potential of magnetic resonance imaging in the evaluation of congenital heart diseases, we reviewed 21 cases of cardiac malformations (age: 9-81, mean: 48 +/- 23). Two dimensional echo-cardiography was performed on all of them. Out of the 21 patients, 13 were imaged to confirm previous diagnoses based on echocardiographic (8) or angiographic (5) data. Four more patients underwent a cardiac angiography after the magnetic resonance study. The remaining eight patients were imaged due to a poor echocardiographic examination (4) and for other reasons (4). Eight patients had an atrial septal defect, 1 had a patent foramen ovale, 2 had a ventricular septal defect, 1 had a corrected transposition of the great vessels, 2 had an aortic coarctation, 2 had a developmental venous abnormality, 5 had different congenital diseases of the aorta or of the pulmonary valve or artery. Image quality was optimal in 18 out of the 21 patients studied (85.7%). In the remaining 3 subjects image quality enabled a diagnosis. In all patients magnetic resonance imaging correctly depicted the cardiac malformation and in some cases furnished data on the severity of the disease. In 9 cases (4 atrial septal defects, 2 developmental venous abnormalities, 2 aortic aneurysms, 1 right pulmonary artery atresia) magnetic resonance imaging provided the diagnosis. These data indicate that magnetic resonance imaging may represent an important non-invasive diagnostic tool capable of offering valuable information on adult patients with suspected congenital heart disease. It is also possible to foresee that this technique will play an outstanding role as a non invasive alternative imaging technique whenever echocardiography cannot be performed is not satisfactory. Furthermore, magnetic resonance imaging should be considered a major diagnostic technique to be used for the anatomic study of the heart prior to resorting to angiography.     

Magnetic resonance imaging in patients with congenital heart disease

Magnetic resonance imaging (MRI) was conducted with use of the spin-echo technique (0.35 Tesla) in 22 patients with a variety of congenital and cardiovascular anomalies and in 16 normal volunteers. Electrocardiographic (ECG) synchronization of the data acquisition produced transverse, parasagittal, and coronal tomograms that were used to define size and relationship of the great vessels and internal cardiac structures. MRI findings were corroborated by angiography and sector-scan echocardiography. In most patients the diagnosis had been established before the MRI study. MRI detected all of 11 abnormalities at the level of the great vessels, all of six atrial septal abnormalities, and 10 of 11 ventricular septal defects. Images of poor quality resulting from patient motion were obtained in the one instance in which a small ventricular septal defect was not imaged. Of two patients with Ebstein's anomaly, the displacement of the tricuspid leaflets was shown in one patient but was not evident in another. Complex anomalies such as double-outlet right ventricle, uncorrected L-transposition, single atrioventricular valve, single ventricle, and common ventricle were clearly shown by MRI. Initial experience with MRI has indicated the effectiveness of this technique for defining great vessel and internal cardiac anatomy in patients with congenital heart disease. This is accomplished without the use of contrast media and is thus a completely noninvasive technique for cardiovascular diagnosis.     

Delineation of site,relative size and dynamic geometry of atrial septal defects by real-time three-dimensional echocardiography

Objectives. This study attempted to determine the site, relative size and dynamioc geometry of atrial septal defects using dynamic three-dimensional echocardiography.Background. Recent studies have demonstrated the feasibility of dynamic three-dimensional echocardiography. Images are acquired from computerized reconstruction of sequential, tomographic ultrasound “slices” of the heart. Ultrasound images can be obtained by linear progression of a transducer within a transesophageal imaging probe. In small infants and children the large transducer size has not allowed transesophageal placement, and the probe has been place on the thorax or in the subcostal position. Other scaning devices, housed in plastic containers, acquire images in a rotational format and can also be placed in a transthoracic or subcostal position.Methods. Specially desiged transesophageal probes and a dedicated computer unit were used for two-dimensional image retrieval and reconstruction of three-dimensional images. Sixteen patients with atrial septal defects were studied (median age 18 months, range 1 day to 18 years). In the one patient, images were obtained by transesophageal probe placement; in the other 15 patients, the probe was placed in the transthoracic or subcostal position.Results. A dynamic three-dimensional echocardiogram of the atrial septal defect could be obtained in 13 of the 16 patients. The distinguishing features of the atrial septal defects and their spatial orientation could be visualized in unique three-dimensional views.Conclusions. Dynamic three-dimensional imaging could be applied to the specific evaluation of atrial septal defects. Unique views of the heart allowed for spatial comprehension of the defects, rendering potentially important clinical information.     

Ventricular septal defects. Two dimensional echocardiographic and morphological correlations.

To evaluate the ability of two dimensional echocardiography to identify and classify ventricular septal defects, 280 infants and children with clinically significant ventricular septal defects were studied. Multiple precordial and subcostal echocardiographic planes were scanned in each patient in an attempt to identify the defects. Defects visualised were classified on the basis of the structures which formed their margins. Subsequent correlation of this information with angiographic (280 patients), surgical (130 patients), and pathological (31 patients) data confirmed that defects in the following sites produced a specific two dimensional echocardiographic pattern. (a) Perimembranous inlet, (b) perimembranous outlet, (c) muscular inlet, (d) single trabecular, (e) muscular outlet, and (f) doubly committed subarterial. A defect was identified and correctly classified in 252 patients. Individual defects were identified with varying degrees of accuracy. All subarterial (24 patients) defects were correctly identified and classified, as were muscular defects of the inlet (18 patients) and outlet (six patients) septa. Of the 185 perimembranous defects, 182 were identified. Only 23 of the 43 single trabecular defects were identified. Small multiple ("Swiss cheese") defects (four patients) were not identified. We conclude that two dimensional echocardiography provides a reliable non-invasive method of identifying and classifying the following ventricular septal defects: (a) perimembranous defects, (b) doubly committed subarterial defects, and (c) muscular defects of the inlet and outlet septa. In our experience it fails consistently to visualise defects in the trabecular septum.     

An unusual diagnosis of atrial shunt defect by magnetic resonance imaging

Paroxysmal atrial arrhythmias especially atrial fibrillation are frequently encountered in adult patients with atrial septal defect. However, the diagnosis of atrial defect can be difficult. Thransthoracic echocardiography, the mostly utilized cardiac technique, has shown a limited ability to identify small atrial defects. Transesophageal echocardiography has shown high accuracy to identify but it isn't well tolerated of the patients. Recently, the utility of multislice computed tomography in the evaluation of direction, location, and size of shunt flow in congenital heart disease has been demonstrated. Cardiac magnetic resonance imaging (MRI) is a recent imaging technique that permits with high spatial resolution and without ionising radiation an accurate identification of many cardiovascular diseases. We report an unusual detection of an atrial defect by phase-contrast cine MRI in a patient clinically suspected of arrhitmogenic right ventricular displasia.     

Localisation of ventricular septal defects by simultaneous display of superimposed colour Doppler and cross sectional echocardiographic images

Precise non-invasive localisation of the site of a small ventricular septal defect was attempted using a new technique that simultaneously combines conventional cross sectional echocardiography with a Doppler system by superimposing the colour coded direction and velocity of blood flow directly on to real time ultrasound images. Twenty three patients with unoperated ventricular septal defects and a further eight after surgical closure were studied; 12 children with normal hearts served as controls. A colour coded blood flow jet entering the right ventricle during systole was identified in all 23 unoperated patients, in 11 of whom the defect was too small to be visualised by conventional cross sectional echocardiography. The colour Doppler technique precisely located 19 perimembranous and five trabecular defects (one patient had two defects). Five of the postoperative patients were without clinical evidence of a significant shunt but had pansystolic murmurs. In each of these five, trans-septal shunt blood flow as demonstrated by colour Doppler images whereas in only three of these patients was the residual defect large enough to be visualised by conventional cross sectional echocardiography. Three postoperative patients had no murmurs and showed no residual shunt on colour Doppler images. This was confirmed at cardiac catheterisation. There were no false positive results among the controls. This technique is useful for the more accurate diagnosis and location of ventricular septal defects and may help in assessing their natural or surgical closure.     

Localisation of ventricular septal defects by simultaneous display of superimposed colour Doppler and cross sectional echocardiographic images.

Precise non-invasive localisation of the site of a small ventricular septal defect was attempted using a new technique that simultaneously combines conventional cross sectional echocardiography with a Doppler system by superimposing the colour coded direction and velocity of blood flow directly on to real time ultrasound images. Twenty three patients with unoperated ventricular septal defects and a further eight after surgical closure were studied; 12 children with normal hearts served as controls. A colour coded blood flow jet entering the right ventricle during systole was identified in all 23 unoperated patients, in 11 of whom the defect was too small to be visualised by conventional cross sectional echocardiography. The colour Doppler technique precisely located 19 perimembranous and five trabecular defects (one patient had two defects). Five of the postoperative patients were without clinical evidence of a significant shunt but had pansystolic murmurs. In each of these five, trans-septal shunt blood flow as demonstrated by colour Doppler images whereas in only three of these patients was the residual defect large enough to be visualised by conventional cross sectional echocardiography. Three postoperative patients had no murmurs and showed no residual shunt on colour Doppler images. This was confirmed at cardiac catheterisation. There were no false positive results among the controls. This technique is useful for the more accurate diagnosis and location of ventricular septal defects and may help in assessing their natural or surgical closure.     

Cine magnetic resonance imaging for evaluating flow dynamics in congenital heart diseases with left-to-right shunts]

Cine magnetic resonance imaging (cine MRI) was used to evaluate the cardiac structures and blood flow in congenital heart diseases with left-to-right shunts. Fifteen children with left-to-right shunts which were confirmed by echocardiography or angiography were investigated in the present study. Five children each had atrial septal defect, ventricular septal defect, and complete endocardial cushion defect. Their ages ranged from 4 months to 13 years (mean 5.5 years). Prior to cine MRI, the ECG-gated cardiac imaging using multi-slice acquisition was performed in all the children to localize the optimal slice for cine MRI. To select the optimal imaging planes for various cardiac structures, we used axial, coronal, sagittal and four-chamber views. Cine MRI was demonstrated by a fast low 30 degree flip angle imaging technique, with a 15 msec echo time, a 30-40 msec pulse repetition time, and a 256 x 256 or 128 x 128 acquisition matrix. Abnormalities of cardiac structures were defined extremely well in all the children using ECG-gated cardiac imaging. In 14 of the 15 children (93%), cine MRI clearly detected a left-to-right shunt flow, which was visualized as a low signal intensity area compared to the surrounding blood flow. Noninvasively, cine MRI provides accurate images of the anatomy of the cardiac structures, makes functional assessments of the cardiac chambers and walls, and flow relationships. It has no limitations of imaging planes imposed bones and lung, and is not associated with technical difficulties as required with echocardiography which has small cardiac window.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intraoperative echocardiography in infants and children with congenital cardiac shunt lesions: transesophageal versus epicardial echocardiography

To determine the utility and limitations of intraoperative transesophageal echocardiography in infants and children with congenital intracardiac shunts, intraoperative transesophageal (n = 50) and epicardial (n = 49) echocardiograms were performed before and after cardiopulmonary bypass in children from 4 days to 16 years old and 3 to 45 kg in body weight. A miniaturized transesophageal probe (6.9 mm maximal diameter) was used in 36 patients weighting less than or equal to 20 kg. Epicardial imaging was performed with a 5 MHz precordial probe. The intraoperative transesophageal echocardiographic findings before and after cardiopulmonary bypass were correct and complete in 94% of patients. Transesophageal echocardiography correctly identified atrial septal defects, most types of ventricular septal defects, anomalous pulmonary veins, atrioventricular septal defects, tetralogy of Fallot, truncus arteriosus and double inlet ventricles. It failed to provide a correct diagnosis in only three patients, all of whom had doubly committed subarterial ventricular septal defects. Epicardial echocardiography identified all cases that had a doubly committed subarterial ventricular septal defect. A correct and complete intraoperative diagnosis was obtained with the use of epicardial imaging in 92% before and after cardiopulmonary bypass, but this technique required interruption of surgery and could not be completed in three patients because of induced arrhythmias and hypotension. These results demonstrated that intraoperative transesophageal echocardiography consistently defined important morphologic, color and pulsed Doppler ultrasound features of most congenital shunt lesions. Lesions that involved the right ventricular outflow tract are sometimes difficult to image with uniplane transesophageal echocardiography. There were no complications in any of the 50 subjects.     

Colour flow imaging in the diagnosis of multiple ventricular septal defects.

Thirty one patients with multiple ventricular septal defects were studied by cross sectional echocardiography, conventional pulsed and continuous wave Doppler, colour flow imaging, and left ventriculography to determine the relative diagnostic benefits and pitfalls of each technique. The patients studied had a wide range of congenital heart defects with 19 patients having isolated multiple ventricular septal defects, three with associated tetralogy of Fallot, five with double outlet right ventricle, three with complete transposition and ventricular septal defect, and one with a complete atrioventricular septal defect. In 23 patients the defects were inspected at operation. Cross sectional imaging with integrated pulsed and continuous wave Doppler correctly identified multiple defects in only 12 (39%) patients. In contrast, colour flow imaging was accurate in 24 (77%) patients and left ventriculography in 20 (65%) patients. When patients were subdivided on the basis of relative peak systolic ventricular pressures into restrictive defects (18 patients) and non-restrictive defects (13 patients) the diagnostic value of colour flow imaging was different for each group. Colour flow mapping correctly identified multiple ventricular septal defects in 16/18 (89%) patients with restrictive defects but only 8/13 (62%) with non-restrictive defects. The comparative diagnostic accuracy of left ventriculography was 15/18 (83%) in the restrictive group and 5/13 (38%) in the non-restrictive group. Colour flow imaging was the single investigative technique with the greatest diagnostic accuracy in the diagnosis of multiple ventricular septal defects. It failed to be consistently accurate in defined subgroups with non-restrictive defects as did left ventriculography. The greatest overall diagnostic accuracy in this series was obtained when both colour flow imaging and ventriculography techniques were used in combination in a complementary fashion.     

Three-dimensional echocardiography of the atrial septum

This article details the important contribution of three-dimensional echocardiography for catheterization device closure of secundum atrial septal defects. Aspects presented include three-dimensional echocardiographic application in preselection of patients and in selection of the type and size of the atrial septal occluder devices. Unique three-dimensional echocardiographic imaging planes are shown that depict the size and shape of the defect, the important rim tissue surrounding the defect, and the images that demonstrate successful device placement. Details of the acquisition phase, digital reformatting, and the eventual rendering of standard three-dimensional echocardiographic imaging planes of the atrial septum are shown. Three-dimensional echocardiography not only provides important additional information, but also enhances understanding of standard two-dimensional studies.     

Colour flow imaging in the diagnosis of multiple ventricular septal defects

Thirty one patients with multiple ventricular septal defects were studied by cross sectional echocardiography, conventional pulsed and continuous wave Doppler, colour flow imaging, and left ventriculography to determine the relative diagnostic benefits and pitfalls of each technique. The patients studied had a wide range of congenital heart defects with 19 patients having isolated multiple ventricular septal defects, three with associated tetralogy of Fallot, five with double outlet right ventricle, three with complete transposition and ventricular septal defect, and one with a complete atrioventricular septal defect. In 23 patients the defects were inspected at operation. Cross sectional imaging with integrated pulsed and continuous wave Doppler correctly identified multiple defects in only 12 (39%) patients. In contrast, colour flow imaging was accurate in 24 (77%) patients and left ventriculography in 20 (65%) patients. When patients were subdivided on the basis of relative peak systolic ventricular pressures into restrictive defects (18 patients) and non-restrictive defects (13 patients) the diagnostic value of colour flow imaging was different for each group. Colour flow mapping correctly identified multiple ventricular septal defects in 16/18 (89%) patients with restrictive defects but only 8/13 (62%) with non-restrictive defects. The comparative diagnostic accuracy of left ventriculography was 15/18 (83%) in the restrictive group and 5/13 (38%) in the non-restrictive group. Colour flow imaging was the single investigative technique with the greatest diagnostic accuracy in the diagnosis of multiple ventricular septal defects. It failed to be consistently accurate in defined subgroups with non-restrictive defects as did left ventriculography. The greatest overall diagnostic accuracy in this series was obtained when both colour flow imaging and ventriculography techniques were used in combination in a complementary fashion.     

Double-outlet right ventricle: morphologic demonstration using nuclear magnetic resonance imaging

Sixteen patients with double-outlet right ventricle, aged 1 week to 29 years (median 5 months), were studied with a 1.5 tesla nuclear magnetic resonance (NMR) imaging scanner. Two-dimensional echocardiography was performed in all patients. Thirteen patients underwent angiography, including nine who underwent subsequent surgical correction. Three patients underwent postmortem examination. Small children and infants were scanned inside a 32 cm diameter proton head coil. Multiple 5 mm thick sections separated by 0.5 mm and gated to the patient's electrocardiogram were acquired with a spin-echo sequence and an echo time of 30 ms. A combination of standard and oblique imaging planes was used. Imaging times were less than 90 min. The NMR images were technically unsuitable in one patient because of excessive motion artifact. In the remaining patients, the diagnosis of double outlet right ventricle was confirmed and correlated with surgical and postmortem findings. The NMR images were particularly valuable in demonstrating the interrelations between the great arteries and the anatomy of the outlet septum and the spatial relations between the ventricular septal defect and the great arteries. Although the atrioventricular (AV) valves were not consistently demonstrated, NMR imaging in two patients identified abnormalities of the mitral valve that were not seen with two-dimensional echocardiography. In one patient who had a superoinferior arrangement of the ventricles, NMR imaging was the most useful imaging technique for demonstrating the anatomy. In patients with double-outlet right ventricle, NMR imaging can provide clinically relevant and accurate morphologic information that may contribute to future improvement in patient management.     

Assessment of muscular ventricular septal defect closure by transcatheter or surgical approach: a three-dimensional echocardiographic study.

AIMS: Previous classification of muscular ventricular septal defects (VSDs) visualized on two-dimensional echocardiography relied on artificial divisions of the septum. New visualization of the ventricular septum integrating the third dimension would facilitate communication between cardiologists and surgeons. The objectives of this study were (1) to assess in patients with muscular ventricular septal defects the accuracy of left ventricular three-dimensional echocardiographic reconstructions in demonstrating the position, the size and the tissue rims of the defects; (2) to compare findings by three-dimensional echocardiography with those obtained by surgical and transcatheter approaches. METHODS AND RESULTS: Twenty-six patients, aged from one month to 40 years, with muscular ventricular septal defects underwent three-dimensional echocardiographic study. From the left ventricular three-dimensional echocardiographic reconstructions, the localization, the maximal diameter and the tissue rim of the defect were analysed and compared with surgical or transcatheter findings. Optimal three-dimensional echocardiographic reconstructions were obtained in 22 patients. Nineteen had a single muscular ventricular septal defect and three had multiple muscular ventricular septal defects. The muscular ventricular septal defect localizations were the inlet septum in three, the outlet septum in three, the mid-muscular septum in 14 and the apex in eighth. In 10 patients who underwent surgical closure, the correlation between three-dimensional echocardiography and surgery for muscular ventricular septal defect maximal diameter was y=0 x 95 x +0.13 (r=0.98; P<0.001). The agreement between three-dimensional echocardiographic and intraoperative findings on muscular ventricular septal defect localization were complete. In five patients who underwent transcatheter closure, the mean difference between three-dimensional echocardiographic maximal diameter and stretched diameter was 1 x 8+/-0 x 5 mm. CONCLUSION: The three-dimensional echocardiographic left ventricular views provide a new and easily communicated visualization of various muscular ventricular septal defects. Such new imaging should contribute to the surgical and transcatheter treatments of muscular ventricular septal defects.