Ann Thorac Surg 1995;60:1282-1288
© 1995 The Society of Thoracic Surgeons
Original Articles: Cardiovascular
Three-Dimensional Echocardiography Can Simulate Intraoperative Visualization of Congenitally Malformed Hearts
Michael Vogel, MD,
Siew Yen Ho, PhD,
Christopher Lincoln, FRCS,
Magdi H. Yacoub, FRCS,
Robert H. Anderson, MD
National Heart and Lung Institute, Royal Brompton Hospital, London, United Kingdom
Accepted for publication June 15, 1995.
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Abstract
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Background. The new technique of three-dimensional echocardiography can display the studied anatomy in any desired view plane. We sought to establish whether the reconstructions produced could provide views of the heart comparable with those obtained by the surgeon in the operating room.
Methods. Ninety-four patients, aged 1 day to 19 years (mean, 4.3 years), were examined. The ultrasound probe was placed either on the chest or subcostally and acquired 80 to 100 perpendicular parallel images of the heart with electrocardiographic and respiratory gating. Any plane, in particular oblique planes, within the data set can be analyzed. Whenever possible, the arrangement as seen by the surgeon was photographed, or heart specimens with similar intracardiac lesions were cut to simulate the view of the surgeons, to validate the echocardiographic reconstructions.
Results. Three-dimensional reconstruction of perimembranous ventricular septal defects, atrial septal defects, or anomalies of the atrioventricular valves could be displayed as viewed through an atriotomy. In similar fashion, reconstructions of muscular or doubly committed ventricular septal defects, along with obstruction of the right ventricular outflow tract, could be prepared as seen through a right ventriculotomy. Obstruction of the left ventricular outflow tract was shown as viewed through an aortotomy. Transthoracic three-dimensional echocardiography provided additional information in the prospective diagnosis of supravalvar mitral membrane, doubly committed subarterial ventricular septal defect, and subaortic stenosis caused by a restrictive ventricular septal defect in double inlet left ventricle.
Conclusions. Three-dimensional echocardiography can simulate the display of the heart as seen by the surgeon in the operating room, and therefore can aid in better planning of surgical repair.
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Introduction
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Conventional cross-sectional echocardiography is frequently used as the noninvasive diagnostic method of choice for delineation of the presence and nature of congenital heart defects [1]. This technique has proved sufficiently successful that many patients now undergo operation based on echocardiographic findings alone [2]. Although the presence and the anatomy of many congenital heart defects can be diagnosed readily by cross-sectional echocardiography, the anatomy is rarely displayed in views that are similar to the ones encountered intraoperatively. Three-dimensional echocardiography by computer-controlled acquisition of multiple sequential cross-sectional echocardiographic scans [3] has the potential of displaying the intracardiac anatomy in views that are similar to the ones encountered during operations [4]. The purpose of this study was (1) to determine the usefulness of three-dimensional echocardiography in displaying the anatomy of congenital heart defects in views simulating intraoperative visualization and (2) to compare the echocardiographic views with anatomic specimens of similar heart lesions or direct photographs of the intraoperative arrangement.
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Material and Methods
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A commercially available Vingmed 800 (Vingmed Inc, Horten, Norway) annular array sector scanner was used interfaced with a Tomtec (Tomtec Inc, Munich, Germany) computer to generate three-dimensional reconstructions derived from multiple two-dimensional echocardiographic cross-sectional images. The extra cost of the Tomtec system used as an add-on machine to the standard ultrasound scanner is about $100,000 (US$). A standard ultrasound transducer is mounted inside a scan frame and moved longitudinally over a distance of up to 5.9 cm in 0.5-mm increments. A cross-sectional echocardiographic scan is performed at each step, thus generating one tomographic slice of the data set (Fig 1
). Electrocardiographic and respiratory gating is achieved with standard electrodes [3]. The external scan frame containing the transducer was positioned either in the subcostal area or on the chest [4]. After performing a complete conventional cross-sectional echocardiographic scan, including Doppler interrogation of all cardiac valves from various transthoracic positions, images suitable for three-dimensional reconstruction were acquired within 3 to 5 minutes. Two or three data acquisitions were usually performed in each patient. The temporally and spatially aligned cross-sectional images were digitally reformatted and subsequently, stored as a volume element or voxel [5] on a 486 33-MHz personal computer with a hard drive capacity of 500 MB.
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Fig 1. . How multiple sequential parallel cross-sections of the heart are acquired suitable for three-dimensional reconstruction. The scanframe with the transducer is positioned over the heart. The transducer is pulled back from the apex to the outflow tract by the stepper motor in 0.5-mm increments. The steering logic of the stepper motor is fed with information on the heart rate (RR interval) and respiratory phase, ensuring that the motor moves the transducer only during expiration and when the RR interval is within the preset limits.
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In addition, during acquisition of data each of the multiple sequential cross-sections of the heart is displayed in real-time on the monitor of the ultrasound scanner as with a conventional cross-sectional echocardiogram. All these cross-sections are recorded using the videorecorder of the ultrasound scanner and are reviewed before reconstruction, as this has proven to facilitate analysis of the data set. Three-dimensional reconstruction, performed off-line, took between 20 and 240 minutes. The cross-sections of the three-dimensional data set, which were displayed on the computer monitor as two-dimensional images, could be rotated in any of the three orthogonal planes. Depending on the experience of the operator, and the anatomy of the congenitally malformed heart, the selection of the optimal cross-sections to display the anatomy took about 15 minutes for a relatively simple lesion, such as isolated discrete subaortic obstruction, approximately 1 hour for atrioventricular valvar malformations, and from 2 to 3 hours for complex anatomy, such as tetralogy of Fallot, particularly if searches were made for additional views such as the one displaying the stenosed pulmonary valve ``en face.'' The selection of the optimal planes is dependent on the operator and requires both knowledge of the anatomy as well as expertise in cross-sectional echocardiography. This process of selection is the most important step in the three-dimensional reconstruction and is the one that largely determines the time required for reconstruction. When a desired cross-section has been found, the computer begins three-dimensional reconstruction, which takes between 5 and 30 minutes depending largely on how many views are selected of the cut plane and these can be rotated around any axis. Three-dimensional effects were achieved by a combination of distance, gradient, and texture shading [6]. Distance shading assigns gray-scale values according to the distance of the object from the cut plane. Gradient shading assigns gray values by comparison with surrounding surfaces, and their angle to each other. Texture shading assigns the gray scale according to the intensity of the reflected signal. In all patients with anatomy suitable for surgical correction, view planes were then reconstructed to resemble the perspective of the surgeon in the operating room. The three-dimensional reconstructions can be displayed dynamically and subsequently stored on magneto-optical disk. The malformations studied in the 94 patients are as follows: ventricular septal defect (VSD), 28 patients (perimembranous VSD, 12; perimembranous VSD with pulmonary stenosis, 1; muscular VSD, 9; doubly committed juxtaarterial VSD with pulmonary stenosis, 1; multiple VSDs, 5); subaortic stenosis, 21; atrioventricular septal defect, 20; tetralogy of Fallot, 13; Ebstein`s malformation, 6; parachute mitral valve, 2; supramitral membrane, 2; and double inlet left ventricle, 2 patients. Thus far, 75 of the 94 patients examined have undergone operative repair. Autopsied examples of selected lesions were cut to correspond to the surgical view plane obtained. In 2 patients, the intraoperative arrangement was photographed directly during operative repair. Restless patients were sedated with 70 mg/kg of chloralhydrate. In 33 patients who had undergone general anesthesia for operation and 16 who had undergone routine general anesthesia for a cardiac catheterization, the technique was performed while the patient remained anesthetized.
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Results
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Three-dimensional reconstruction was possible in 84 (89%) of the patients. Movement of the patient during acquisition of data (4 patients) or the finding of an unsuitable transthoracic echocardiographic window (6 patients), rendered 10 data sets unsuitable for three-dimensional reconstruction. The oldest patient in whom three-dimensional reconstruction proved possible was a 16-year-old boy with Ebstein's malformation of the tricuspid valve. Reconstruction of the heart to simulate the surgical views was not possible in 6 of the patients with atrioventricular valvar abnormalities. Gray structures produced by valvar reverberations obstructed the view of the valve. Thus, reconstruction of intraoperative views proved possible in 78 of the 94 patients.
Specifically, the mitral valve could be presented as viewed through a left atriotomy by achieving ``electronic removal'' of the roof of the left atrium. The observer, like the surgeon, is then able to look down on the atrial aspect of the mitral valve (Fig 2). The three-dimensional reconstruction is compared to a photograph obtained during surgical repair in the same patient. In patients with subaortic stenosis, it proved possible to present the narrowing as might be viewed through an aortotomy. The ``electronic cut'' is made immediately beneath the hinge points of the valvar leaflets so as to provide a view of the subaortic area as would be obtained by the surgeon using retractors to move the leaflets of the aortic valve. The subaortic stenosis can then be seen from its superior aspect (Figs 3, 4). In this particular patient, the subaortic stenosis was caused by a restrictive VSD divided by a muscle bar in the setting of double inlet left ventricle, rudimentary right ventricle, and discordant ventriculoarterial connections (transposition). This diagnosis had not been made either by conventional cross-sectional echocardiography or by angiography. The three-dimensional echocardiographic findings were confirmed during subsequent operation.
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Fig 2. . (A) Cross-sectional image (right) and three-dimensional reconstruction (left) in a patient with supravalvar mitral membrane. The cross-section of the data set resembles a conventional four-chamber view. The arrows point to the membrane. (B) Intraoperative photography in the same patient. (ao = aorta; LA = left atrium; lv = left ventricle; MV = mitral valve.)
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Fig 3. . Display of one cross-section of the three-dimensional data set of a patient with double-inlet left ventricle, rudimentary right ventricle, discordant ventriculoarterial connection, and subaortic stenosis. The cross-section is similar to a conventional four-chamber view. The black square surrounds the part of the data set that was subsequently reconstructed to produce Fig 4 . (Ao = aorta; DILV = double-inlet left ventricle; rud RV = rudimentary right ventricle.)
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Fig 4. . (A) Cross-section (right) and three-dimensional reconstruction (left). The arrows indicate the position of the observer who looks down through the aortic root into the rudimentary right ventricle and onto the ventricular septal defect. The division of the defect (VSD) by a muscle bar can be appreciated. (B) Anatomic specimen of a heart with similar anatomy. The aortic root and the free wall of the rudimentary right ventricle has been opened to expose the subaortic area and permit viewing of the ventricular septal defect from the rudimentary right ventricle (RV). The stars indicate the two parts of this ventricular septal defect divided by a muscle bar.
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Perimembranous VSDs can be displayed as if seen through the right atrium. The right atrial free wall and roof are electronically removed, thus permitting the observer to look down onto the atrial aspect of the tricuspid valve and see those parts of the defect that normally are partially hidden by the septal leaflet of the tricuspid valve (Fig 5). Muscular VSDs were displayed as seen through a right ventriculotomy with the observer looking from the right ventricular cavity onto the ventricular septum (Fig 6). In this patient, conventional cross-sectional echocardiography and angiography had both suggested the presence of two VSDs. Three-dimensional reconstruction showed a singular large defect partitioned by the septomarginal trabeculation. This finding was confirmed at operative repair, which required cutting away the septomarginal trabeculation to expose the entirety of the VSD. In 1 patient, thought to have tetralogy of Fallot, reconstruction revealed a doubly committed juxtaarterial VSD and valvar pulmonary stenosis. The three-dimensional echocardiographic diagnosis was confirmed at operation (Fig 7).
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Fig 5. . (A) Display of one cross-section of a small perimembranous ventricular septal defect (right) and a three-dimensional reconstruction (left). The arrow inside the left ventricle (LV) points to the ventricular septal defect. The three-dimensional reconstruction demonstrates that the view of the ventricular septal defect is partially occluded by the septal tricuspid valve leaflet (STVL). (B) Anatomic specimen of a heart with similar anatomy. The septal valve leaflet is indicated by the closed black arrow. The open arrow points to the small part of the perimembranous ventricular septal defect that can be seen from the right side of the heart. (Ao = aorta; LA = left atrium; RA = right atrium; RV = right ventricle; VS = ventricular septum.)
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Fig 6. . (A) Display of one cross-section of the three-dimensional data set (right) and three-dimensional reconstruction (left) of a large muscular ventricular septal defect (VSD) showing how the data set was electronically cut to generate a surgical view. The arrows indicate the position of the observer in the right ventricle (RV) and the direction of view toward the septum. The boundaries of the ventricular septal defect are marked by arrows. The septomarginal trabeculation (smt) is partially obstructing the view onto the defect. (B) Anatomic specimen of a heart with similar anatomy. The rather prominent septomarginal trabeculation (SMT) divides the ventricular septal defect (stars). (LV = left ventricle; RA = right atrium.)
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Fig 7. . (A) Intraoperative arrangement and (B) three-dimensional reconstruction of a heart with doubly committed juxtaarterial ventricular septal defect (VSD). The three leaflets of the aortic valve can be seen in continuity with those of the pulmonary valve.
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Comment
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Our study has demonstrated that processing of transthoracically acquired multiple sequential echocardiographic cross-sectional scans can provide three-dimensional images of congenital cardiac malformations that simulate the perspective of the surgeon working in the operating room. Comparison either with autopsy specimens or direct intraoperative inspection confirmed that the reconstructions reflect accurately the anatomy present [7]. Indeed, the reconstructions of a heart under normal workload, which can be displayed dynamically on videotape, may offer information that more accurately reflects the anatomy of the beating heart as compared to the surgical inspection of the nonbeating heart during operation. Structures that may potentially interfere with the field of vision can be removed electronically during the reconstruction of the data set [8]. The relevant anatomic features may also be displayed in views offering even more information than intraoperative inspection. Acquisition of echocardiographic tomographic data suitable for reconstruction was feasible in most infants and children either through the transthoracic window or using a subcostal approach [4, 7, 9].
Although we used this technique in some patients undergoing general anesthesia for reasons other than acquisition of the echocardiographic data, three-dimensional echocardiography remains essentially a noninvasive technique. Nonetheless, to provide data suitable for three-dimensional reconstruction, the cross-sectional echocardiographic data must be of the highest quality. It cannot be used if there is significant motion of the patient during acquisition [4, 5, 7]. To provide optimal reconstruction of the echocardiographic scans, we routinely performed at least two, and usually three, acquisitions of data, each of 3 to 5 minutes duration. The main drawback of our present method is not the time needed to acquire the multiple sequential cross-sections that form a three-dimensional data set, but the extensive time needed for reconstruction. Most of this time is spent on choosing the adequate plane for reconstruction. Although increasing experience with three-dimensional echocardiography [10, 11] and recent advances in the software packaging have decreased the time needed for reconstruction, currently we still need hours rather than minutes to obtain satisfactory reconstructions. We remain far from on-line three-dimensional echocardiography [12].
Transthoracic three-dimensional echocardiography, because it depends on the data acquired, has exactly the same limitations as cross-sectional echocardiography. Thus, extracardiac structures or cardiac structures hidden in part by lung tissue, such as conduits placed from the right ventricle to pulmonary arteries, cannot be imaged properly [13]. Modification of the hardware used sequentially to steer the transducer and the use of rotational scanning with a transducer in a fixed position rotated 180 degrees around its vertical axis [14], have recently allowed for imaging through the suprasternal window to evaluate the aortic arch. The major advantage of three-dimensional reconstruction is that it displays the intracardiac anatomy in the fashion routinely used by the surgeon for viewing intracardiac structures. Therefore, the technique functions not only as a tool to improve communication between cardiologists and surgeons, but also as an aid for teaching cardiac anatomy. In the future, we anticipate that it will prove invaluable in planning surgical procedures. With our present computer, we can already remove electronically cardiac structures to improve visualization [11]. In the future, with the development of interactive software, we anticipate the potential to simulate operative procedures and view their effect on the cardiac anatomy. Display of the three-dimensional structures of the heart as holograms may still further enhance our understanding of the cardiac anatomy [15].
The current acquisition of data as well as the three-dimensional reconstructions were performed by the same person who had expertise in cross-sectional echocardiography and was working full-time in applying and evaluating this new technique. As the cross-sections were displayed on the monitor during acquisition and were available for review, it proved impossible to blind the observer performing reconstructions from the raw data obtained by conventional cross-sectional scanning. As with all new technology in the initial phase of its application, the results are highly dependent on the skill of the operator and may not be universally reproducible. The current system of three-dimensional reconstruction from multiple cross-sectional echocardiographic scans is certainly still cumbersome and time-consuming to use, and the process of reconstruction requires a substantial learning curve. Another limitation is the current high additional cost of the off-line computer, which is largely due to the high cost of development of the dedicated software. As with all new computer technology, this cost, today in a range similar to the additional costs of color Doppler when initially introduced about 10 years ago, will eventually decrease. The high expenditure is similar to, or less than, that of alternative imaging techniques such as magnetic resonance, which require a longer time for data acquisition and equally skilled technicians to obtain three-dimensional reconstructions. The full benefits of three-dimensional echocardiography can only be evaluated if this technique is used by many centers, which will lead to competition among software and ultrasound companies to produce easier and more rapid reconstructions.
Therefore, we conclude that this new technology, despite its current limitations, warrants further use and development. It provides the surgeon with useful information on the anatomy of congenital cardiac malformations and may be an important step to achieving instant real-time three-dimensional display of cardiac anatomy.
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Acknowledgments
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Doctor Vogel was supported by a grant from the European Society of Cardiology.
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Footnotes
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Doctor Vogel's present address is Deutsches Herzzentrum Berlin, Augustenburger Platz 1, D-13305 Berlin, Germany.
Address reprint requests to Dr Ho, Department of Paediatrics, National Heart and Lung Institute, Dovehouse St, London SW3 6LY, England.
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References
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- Gutgesell HP, Huhta JC, Latson LA, Huffines D, McNamara DG. Accuracy of 2-dimensional echocardiography in the diagnosis of congenital heart defects. Am J Cardiol 1985:55:514–8.[Medline]
- Huhta JC, Glasow P, Murphy DJ, et al. Surgery without catheterization for congenital heart defects: management of 100 patients. J Am Coll Cardiol 1987;9:823–9.[Abstract]
- Wollschläger H, Zeiher AM, Klein HP, Kasper W, Geibel A, Wollschläger S. Transesophageal echo computer tomography: a new method for dynamic 3-D imaging of the heart [Abstract]. Circulation 1989;80(Suppl 2):569.
- Vogel M, Lösch S. Dynamic three-dimensional echocardiography with a computed imaging probe (echo-CT). Initial clinical experience with transthoracic application in infants and children with congenital heart defects. Br Heart J 1994;71:462–7.[Abstract/Free Full Text]
- Marx GR, Fulton Dr, Pandian NG, et al. Delineation of site, relative size and dynamic geometry of atrial septal defects by real-time three-dimensional echocardiography. J Am Coll Cardiol 1995;25:482–90.[Abstract]
- Cao Q-L, Pandian NG, Azevedo J, et al. Enhanced comprehension of dynamic cardiovascular anatomy by three-dimensional echocardiography with the use of mixed shading techniques. Echocardiography 1994;11:627–33.[Medline]
- Vogel M, Ho SY, Anderson RH. Comparison of three-dimensional echocardiographic findings with anatomic specimens of various congenitally malformed hearts. Br Heart J 1995;73:566–70.[Abstract/Free Full Text]
- Pandian N, Roelandt JR, Nanda NC, et al. Dynamic three-dimensional echocardiography: methods and clinical potential. Echocardiography 1994;11:237–59.
- Vogel M, Lösch S, Bühlmeyer K. The application of transthoracic dynamic three-dimensional echocardiography by computer-controlled parallel slicing in patients with fixed subaortic obstruction. Cardiology in the Young 1994;4:7–14.
- Schwartz SL, Cao QL, Azevedo J, Pandian N. Simulation of intraoperative visualization of cardiac structures and study of dynamic surgical anatomy with real-time three-dimensional echocardiography in patients. Am J Cardiol 1994;73:501–7.[Medline]
- Pandian NG, Cao QL, Erbel R, et al. A comprehensive approach for image segmentation, cutting planes and display projections in three-dimensional echocardiography: suggested guidelines for clinically useful projections based on multicenter experience in 300 adults and pediatric patients [Abstract]. J Am Coll Cardiol 1994;23(Suppl):9A.
- Sheikh KH, Smith SW, von Ramm O, Kisslo J. Real-time, three-dimensional echocardiography: feasibility and initial use. Echocardiography 1991;8:119–25.[Medline]
- Kandah, T, Kimball TR, Daniels SR, et al. When is echocardiography unreliable in patients undergoing catheterization for pediatric cardiovascular disease? J Am Soc Echocardiogr 1991;4:51–6.[Medline]
- Ludomirsky A, Vermillion R, Nesser J, et al. Transthoracic real time 3-dimensional echocardiography using rotational scanning approach for data acquisition. Echocardiography 1994;11:599–606.[Medline]
- Vannan M, Pandian N, Dalton M, et al. Ultrasound holography of the heart and great vessels: a new direction in 3-dimensional echocardiography using volumetric multiplexed registration and transmission holography—methods and feasibility [Abstract]. Circulation 1993;88(Suppl 1):1837.
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Top
Abstract
Introduction
