From Boston Floating Hospital for Infants and Children, New England
Medical Center, Tufts University School of Medicine, Boston, Mass.
Correspondence to Gerald R. Marx, MD, Department of Cardiology, Children's Hospital, 300 Longwood Ave, Boston, MA 02115. E-mail marx{at}cardio.tch.harvard.edu
Methods and Results—Seventeen experimentally created defects of
various locations, sizes, and shapes were imaged and reconstructed in 9
explanted porcine hearts. From an en face projection, major and
minor axis diameters of the defects were measured, and these data were
compared with direct anatomic measurements. Optimal reconstructions of
the VSDs were obtained in all heart specimens, accurately depicting
their positions and shapes. The correlations between 3DE and
anatomy for the VSD major and minor axis diameters were
y=1.0x+0.3 (r=0.88,
P<0.001) and y=1.0x-1.4
(r =0.89, P<0.001), respectively. Good
agreement between the 2 methods was demonstrated for all measurements.
Our experience from the in vitro model was then applied to patient
studies. Optimal LV en face reconstructions were obtained in 45 of 51
patients, permitting detailed assessment of the positions, sizes, and
shapes of the VSDs. In the 25 patients with comparative surgical
measurements, the correlations between 3DE and surgery for the VSD
major and minor axis diameters were y
=0.81x+2.1 (r=0.92,
P<0.001) and y=0.73x+2.0
(r=0.91, P<0.001), respectively. Good
agreement was demonstrated between measurements made by 3DE and those
obtained at surgery.
Conclusions—3DE provides excellent visualization of various types
of VSDs. From an LV en face projection, the positions, sizes, and
shapes of VSDs can be accurately determined. Such precise imaging will
be beneficial for surgical and catheter-based closure of difficult
perimembranous and singular or multiple muscular VSDs.
Recent studies have successfully used 3-dimensional
echocardiography (3DE) to evaluate atrial septal
defects.4 5 The 3D en face reconstructions of the
interatrial septum provide unique views that allow accurate assessment
of the sizes, shapes, and spatial orientations of these defects.
Preliminary experience has demonstrated that 3DE can provide important
information pertaining to the morphological and spatial features of
various types of VSDs.6 7 8 Similar to a
surgeon's perspective, direct visualization of certain membranous and
muscular VSDs from the right ventricular (RV) en face view
is frequently obscured by overlying tissue or cardiac structures. The
3D rendering from the smooth-walled left ventricular (LV)
surface might provide unique, unobstructed views of the
interventricular septum, hence obviating many of the
problems encountered from the RV side. From an LV en face view, the
entire circumference of the VSD might be seen, allowing accurate size
and shape determination.
The objectives of this study were (1) to assess the accuracy of 3DE in
demonstrating the positions, sizes, and shapes of VSDs in an in vitro
model and to determine the optimal operator settings of threshold and
opacification to most accurately obtain VSD measurements; (2) to apply
experience from the in vitro model to determine the feasibility to
render LV en face views of VSDs in pediatric patients; and (3) to
compare findings by 3DE with those obtained at surgery.
Instrumentation and Data Acquisition
Image Processing and Display
Image Analysis
Clinical Study
Instrumentation and Data Acquisition
Image Processing and Display
Image Analysis
Statistical Analysis
An increase in threshold by 10 U led to overestimation of major VSD
diameter size by 6±18% and overestimation of the minor diameter by
6±5%. A decrease in threshold by 10 U resulted in underestimation of
major VSD diameter size by 8±13% and underestimation of the minor
diameter by 6±4%. An increase in the opacity by 10 or 20 U led to no
significant change in the major diameter size. However, an increase in
opacity by 10 and 20 U led to overestimation of VSD minor diameter
measurement by 11±29% and 17±23%, respectively.
Clinical Study
The 3D en face projection depicted a defect immediately beneath the
aortic valve in the perimembranous region of the
interventricular septum in 35 patients (Figure 2B
A VSD was identified entirely within the muscular portion of the
ventricular septum in 10 patients (Figure 4
In 3 patients, a doubly committed subarterial VSD was
visualized. From an LV en face view, the VSD appeared subaortic in
position (Figure 5A
In all 45 patients (52 VSDs), major and minor axis measurements could
be made. The mean 3DE major axis measurement was 7.5±2.4 mm
(range, 3.5 to 12.0 mm), and the mean minor axis measurement was
5.3±1.7 mm (range, 2.8 to 9.6 mm). In the 25 patients with
surgical measurements, the mean major diameter measured at surgery was
8.6±2.2 mm (range, 4.0 to 12.0 mm), and the mean 3DE
measurement was 9.0±2.0 mm (range, 5.0 to 12.0 mm). The mean
difference between the 2 measurements was 0.4±0.09 mm
(P=0.030); the 95% CI was 0.0 to 0.8 mm; and the 95%
limits of agreement for the difference were -1.3 and 2.1 mm
(r=0.92; y=0.81x+2.06;
P<0.001) (Figure 6A
Intraobserver variability was 4.7% for the major axis diameter and
5.9% for the minor axis diameter. The absolute mean difference between
observations was 0.1 mm for both the major and minor axis
diameters. Assuming that the true population mean difference is 0, then
95% of all absolute individual intraobserver differences should be
<1.3 mm for the major diameter and <1.0 mm for the minor
diameter. Interobserver variability was 2.7% for the major axis
diameter and 4.1% for the minor axis diameter. The absolute mean
difference between observations was 0.1 mm for the major axis
diameter and 0.2 mm for the minor axis diameter. Again assuming
that the true population mean difference is 0, 95% of all individual
absolute interobserver major diameter differences should be <0.8
mm, and 95% of all individual absolute interobserver minor diameter
differences should be <0.7 mm.
In the in vitro model, the 3DE images closely resembled the shapes and
positions of anatomic specimens. Moreover, good agreement was found
between major diameter measurements obtained by 3DE and those made
directly on the anatomic specimens. Although 3DE tended to
underestimate the minor diameter measurements, the difference was very
small. From the in vitro model, we found that an increase in either the
threshold or opacity above an "optimum" level led to overestimation
of the VSD minor diameter measurement. This may, in part, explain the
small but consistent overestimation by 3DE in the in vitro
model. In clinical practice, we have learned not to apply large changes
in opacity, even though the appearance of the reconstruction is
slightly smoother.
Enhanced 3D reconstructions were obtained in the explanted hearts,
because neither heart rate nor respiratory cycle gating was required.
No movement artifact was encountered, and the
echocardiographic signal was not attenuated by the
chest wall or other anatomic structures, as would be experienced with
typical clinical studies. Additionally, the acquisition for 3DE
reconstruction was done with parallel scanning. Theoretically, no
divergence of digital information in the far field would be encountered
with parallel scanning, as would be experienced with the rotational or
fanlike scanning. Although we realize that higher-quality 3D
reconstructions were obtained, the in vitro model provided a firm
foundation for the clinical studies.
From the 3DE clinical study, we recognized specific features to
differentiate the anatomy of the various defects. However, we
encountered difficulties in applying standard nomenclature for the
VSDs, in part related to the different terminology used in the
literature. To date, nomenclature established in pathologic specimens
has been adapted to correspond to 2D
imaging.11 12 13 However, because 3D imaging can
provide a better depiction of the true spatial relationships of the
VSDs, future classification may rely on such imaging.
Initially, we chose an RV cutting plane to visualize and measure the
VSDs. We had developed considerable experience in the utility of the
right-sided en face views in previous studies on atrial septal
defects.4 5 Additionally, in designing this
study, we wanted comparative surgical measurements. In most cases, the
surgeon makes comparative measurements from the right side, and we
wanted to simulate that methodology. However, we realized that, as in a
surgeon's view, VSDs were often hidden or difficult to visualize from
the RV cutting plane. In particular, perimembranous VSDs were obscured
by either tricuspid valve tissue or remnants of the membranous septum.
Muscular defects were often hidden by either heavy, course RV
trabeculations or tricuspid valve apparatus.
The LV en face projections provided unobstructed evaluation of the
defects, their borders, and surrounding structures. In juxtaposition to
the smooth-walled LV surface, the perimeters of the muscular defects
could be more clearly defined.
Importantly, from this study, we developed standardized cutting planes
to best evaluate the various VSDs. For example, perimembranous VSDs
were best seen from a 3-chamber view, which included the left atrium,
left ventricle, and aorta. Muscular VSDs were more difficult to render.
Similar to the perimembranous VSDs, the cut plane was initially
oriented parallel to the LV septal surface. However, the cut plane was
then rotated in various directions to better visualize the muscular
defects, dependent on their location within the ventricular
septum. For example, the cut plane was rotated to include the aorta to
best visualize high muscular defects. A 2-chamber view, including only
the left atrium and left ventricle, was used to best depict more
posterior and/or inferior defects. Standardization of
imaging planes should reduce the subsequent reconstruction time.
We discovered specific anatomic characteristics on the basis of
3D imaging to aid in future recognition. All perimembranous VSDs were
either circular or oval and could consistently be seen
immediately below the aortic valve. However, in
Unbeknown to the investigators, en face LV cutting planes showed
the muscular defects to be of complex shapes. In particular, triangular
and crescentic VSDs were identified by 3DE and then subsequently
confirmed at the surgery. This left-sided cut plane could also depict
the positions and sizes of multiple muscular VSDs, including anterior
and apical defects. The curvilinear relationship of the
ventricular septum makes the latter muscular defects
difficult to appreciate by 2D imaging. Vogel et
al8 maintain that a volume-based data set allows
easier recognition of muscular VSDs that might otherwise be missed by
2DE. Furthermore, a volumetric data set allows cut planes to be placed
and rotated in a multitude of directions, allowing en face views of
complex muscular defects.
The LV en face projection showed doubly committed VSDs to be
directly subaortic, albeit slightly more anterior than the typical
perimembranous defect. The RV en face projection portrayed the
defects directly subpulmonic, away from the membranous septum and
adjacent tricuspid valve. Two patients had marked prolapse of the right
aortic cusp through the defect, resulting in significant aortic
insufficiency. The 3D echocardiography not only
allowed accurate assessment of the VSD size and degree of valve
prolapse but also provided enhanced spatial appreciation of the
commitment of the defect to both great arteries.
In a blinded, controlled manner, the 3DE measurements compared well
with those obtained at surgery. Because the en face projection
allows delineation of the entire perimeter, determination and
measurement of the major and corresponding minor diameters could be
made directly in noncircular defects. This advantage of 3D imaging was
even more apparent when measurements were made for the crescentic and
triangular muscular defects. A very good comparison was found for
moderate to large defects. However, anatomic comparisons were not
available for smaller defects, because reliable comparative
measurements were not available from surgery. In our experience,
operator-dependent factors of thresholding and opacification seem to
influence the imaging of smaller defects, and we would expect less
agreement between measurements.
Several problems were encountered in the clinical protocol. Because all
studies were predicated on rendering the 3D displays from 2DE data
sets, the general types and positions of the defects were known to one
of the investigators during both the acquisition and rendering phases.
Nonetheless, actual measurements were done in a blinded manner.
Additionally, the intraobserver variability was done on completely
different rendered images, not just different measurements on the same
image.
Twelve percent of studies were not suitable for 3D rendering because of
a combination of difficulties, including movement artifact, poor
gating, and suboptimal 2D imaging. Our clinical study also lacked a
true gold standard to provide accurate VSD size and shape
determinations. Surgical measurements were done on an empty flaccid
heart after the institution of low-flow bypass. This may account for
the small but consistent overestimation by 3DE compared with
surgical measurements. Furthermore, as already mentioned, our 3DE
measurements were made from the LV side, whereas those made at surgery
were from the RV side. We do realize that the size of the defect
measured from the LV side may not relate to the
hemodynamic importance. For example, flow through a
perimembranous defect may be restricted by membranous septum or
tricuspid valve tissue on the RV side. Furthermore, what may appear as
a singular, large muscular VSD from the LV septum may present as
multiple, smaller muscular VSDs from the RV side. Flow streams may be
divided and restricted by RV trabecular tissue. In the
future, 3D analysis of flow reconstructions may help to further
define multiple muscular defects.
The 3D display of VSDs could have important applications for planning
optimal surgical approaches for defect repair. Residual VSDs are well
recognized as a cause of significant postoperative
hemodynamic compromise.14
Difficulties in visualization of apical and anterior muscular VSDs have
prompted surgeons to perform left
ventriculotomies.15 The 3D
echocardiographic left ventricular en face
views may provide the same information without potential complications
from an LV incision.
These unique left-sided en face views may be distinctly applicable for
device closure in the cardiac catheterization
laboratory.16 17 Precise delineation of the size,
shape, and position of the VSD will help in appropriate preselection of
patients. Accurate measurement will aid in the selection of the
appropriately sized device to better anchor on the LV side. Knowledge
of the precise relationship to other anatomic landmarks will help to
avoid complications from device closure such as damage to the aortic or
tricuspid valves.18 19 The very complex variety
of VSD shapes may culminate in customized production of
occluding devices.
The 3D reconstruction of VSDs may provide an excellent tool for
educational purposes, for standardizing imaging, and for establishing a
more universal nomenclature. Van Praagh et al,20
in a letter to the editor, used a schematic of an LV en face view to
better demonstrate their concept of VSD anatomy. Visualizing
VSDs in a dynamic mode from multiple projections should contribute
to the medical and surgical treatments of this common congenital heart
defect.
Received January 23, 1998;
revision received May 12, 1998;
accepted May 20, 1998.
2.
Cheatham JP, Latson LA, Gutgesell HP.
Ventricular septal defect in infancy: detection with
two-dimensional echocardiography. Am J
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Capelli H, Andrade JL, Sommerville J. Classification
of the site of ventricular septal defect by 2-dimensional
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4.
Marx GR, Fulton DR, Pandian NG, Vogel M, Cao QL,
Ludomirsky A, Delabays A, Sugeng L, Klas B. Delineation of site,
relative size and dynamic geometry of atrial septal defects by
real-time three-dimensional echocardiography.
J Am Coll Cardiol. 1995;25:482–490.[Abstract]
5.
Magni G, Cao QL, Sugeng L, Delabays A, Marx G,
Ludomirsky A, Vogel M, Pandian NG. Volume-rendered three-dimensional
echocardiographic determination of the size, shape, and
position of atrial septal defects: validation in an in vitro model.
Am Heart J. 1996;132:376–381.[Medline]
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6.
Rivera JM, Siu SC, Handschumacher MD, Lethor JP,
Guerrero JL, Vlahakes GJ, Mitchell JD, Weyman AE, King ME, Levine RA.
Three-dimensional reconstruction of ventricular septal
defects: validation studies and in vivo feasibility. J Am
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7.
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three-dimensional echocardiographic findings with
anatomic specimens of various congenitally malformed hearts. Br
Heart J. 1995;73:566–570.
8.
Vogel M, Ho SY, Lincoln C, Yacoub MH, Anderson RH.
Three-dimensional echocardiography can simulate
intraoperative visualization of congenitally malformed hearts.
Ann Thorac Surg. 1995;60:1282–1288.
9.
Salustri A, Roelandt J. Three-dimensional
reconstruction of the heart with rotational acquisition: methods and
clinical applications. Br Heart J. 1995;73:10–15.
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agreement between two methods of clinical measurements.
Lancet. 1986;1:307–310.[Medline]
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Sutherland GR, Godman MJ, Smallhorn JF, Guiterras P,
Anderson RH, Hunter S. Ventricular septal defects:
two-dimensional echocardiographic and morphologic
correlations. Br Heart J. 1982;47:316–328.
12.
Hagler DJ, Edwards WD, Seward JB, Tajik AJ.
Standardized nomenclature of the ventricular septum and
ventricular septal defects, with applications for
two-dimensional echocardiography. Mayo Clin
Proc. 1985;60:741–752.[Medline]
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Baker EJ, Lueng MP, Anderson RH, Fischer DR,
Zuberbuhler JR. The cross sectional anatomy of
ventricular septal defects: a reappraisal. Br
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14.
Kirklin J, Castenada A, Keane J, Fellows K, Norwood W.
Surgical management of multiple ventricular septal defects.
J Thorac Cardiovasc Surg. 1980;80:485–493.[Abstract]
15.
Griffiths SP, Turi GK, Ellis K, Krongrad E, Swift LH,
Gersony WM, Bowman FO, Malm JR. Muscular ventricular
defects repaired with left ventriculotomy. Am J
Cardiol. 1981;48:877–886.[Medline]
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16.
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ventricular septal defect. Br Heart J. 1994;72:368–371.
17.
Sideris EB, Walsh KP, Haddad JL, Chen C-R, Ren SG,
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18.
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V, Meyer JE, Jonas RA, Casteneda AR, Lock JE. Preoperative
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© 1998 American Heart Association, Inc.
Clinical Investigation and Reports
New Insights and Observations in Three-Dimensional Echocardiographic Visualization of Ventricular Septal Defects
Experimental and Clinical Studies
Abstract
Top
Abstract
Introduction
Methods
Results
Discussion
References
Background—The positions, sizes,
and shapes of ventricular septal defects (VSDs) can be
difficult to assess by 2-dimensional
echocardiography (2DE). Volume-rendered
3-dimensional echocardiography (3DE) can provide
unique views of VSDs from the left ventricular (LV) side,
allowing complete assessment of their circumference and spatial
orientations to other anatomic structures.
Key Words: echocardiography • heart septal defects • pediatrics
Introduction
Top
Abstract
Introduction
Methods
Results
Discussion
References
Two-dimensional echocardiography
(2DE) is a well-established method for the diagnosis and management of
ventricular septal defects
(VSDs).1 2 3 Currently, however, 2DE requires
mental integration of composite orthogonal views to conceptualize the
position of the defect within the interventricular septum
and its relationship with other anatomic structures. Accurate
assessment of the size and shape of a VSD is also difficult, because
complete visualization of the borders of a defect cannot be achieved in
a single 2D view. More precise delineation of certain VSDs might be
advantageous for surgical and transcatheter device
closure.
Methods
Top
Abstract
Introduction
Methods
Results
Discussion
References
In Vitro Study
Experimental Preparation
In 9 explanted porcine hearts, portions of the
ventricular septum were directly incised to create 17 VSDs
of various locations, shapes, and sizes (Figure 1
). The hearts were then fixed in
formaldehyde for 2 weeks. With the hearts suspended in a water bath,
3DE was performed by use of parallel scanning. Immediately after 3DE
data acquisition, the RV free wall was removed, and the defect borders
were traced on a transparency placed directly on the defect. Major and
minor orthogonal diameters of the VSDs were then measured for later
comparison with 3DE data.
View larger version (131K):
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Figure 1. A, Anatomic specimen with RV free wall removed to
display large muscular inlet VSD (left) and corresponding
volume-rendered 3D reconstruction depicting en face view of the VSD
(right). B, Anatomic specimen with RV free wall removed to display
outlet VSD (left) and corresponding 3D reconstruction (right).
The 3DE data acquisition was performed on the same day that the
measurements on the anatomic specimens were obtained. The hearts were
suspended in a water bath, and 2D images were acquired with a
commercially available 5-MHz probe located 4 to 5 cm from the heart and
situated within a motor housing unit for parallel scanning. The probe
and ultrasound imaging system (Interspec) were interfaced with a
dedicated 3D image-processing unit (Echo-Scan, TomTec). As the
transducer moved longitudinally from the apex of the heart to the
outflow tracts, a total of 216 image slices were acquired over a length
of 60 mm.
Data processing was performed off-line by the TomTec system. A
cut plane placed in a longitudinal direction through the
ventricular free wall parallel to the
ventricular septum was used to derive an en face view of
the VSD (Figure 1
). Once the appropriate cut plane was chosen, an
optimal threshold value was selected to best identify the borders of
the VSD and to separate cardiac structures from the blood pool and
background. An opacity value was then selected that best distinguished
the solid surface of the interventricular septum from the
transparent area of the septal defect.
The positions and shapes of the VSDs by 3DE were compared with
the anatomic data. With the use of on-line electronic calipers, the
major and minor axis diameters were measured directly on the 3DE image.
Interobserver variability was compared in all hearts.
Operator-dependent image-processing factors of threshold and
opacification were independently altered to determine the effects on
3DE measurements. The 3D reconstructions were again rendered after the
threshold was first increased and then decreased by 10 U, and the
opacity was increased by 10 and then 20 U. After each change, the major
and minor axis diameters were measured with on-line electronic
calipers. These measurements were then compared with the actual
measurements of the pathological specimens.
Subjects
Fifty-one patients, with a median age 3.8 months (range, 1 day
to 16 years) and known to have a VSD by clinical examination and 2DE,
were studied prospectively. In 4 patients, 2DE images were obtained by
a transesophageal approach after probe placement for
intraoperative monitoring. In all others, a transthoracic
approach was used, with the probe placed in a subcostal position. These
studies were performed in conjunction with the patient's standard 2D
Doppler echocardiographic examination. When
clinically indicated, infants and young children received either
chloral hydrate or versed sedation. Diagnoses included perimembranous
VSD in 35 patients, muscular VSDs in 9 patients, both perimembranous
and muscular VSDs in 3 patients, and doubly committed
subarterial VSDs in 4 patients. Associated lesions included
coarctation of the aorta (5 patients), pulmonary valve
stenosis (5 patients), and transposition of the great arteries
(3 patients). Patients with AV septal defects and large malalignment
conoventricular defects were excluded from the study.
Twenty-nine patients underwent surgical closure of their VSDs; in 25 of
these patients, the major and minor axis diameters were determined by
direct measurement for comparison with 3DE data. In nearly all cases,
surgical repair was performed through a right atriotomy with the
patient on cardiopulmonary bypass, and VSD measurements were
made after complete exposure of the defect.
The 2D image acquisition for 3D reconstruction was performed
with a commercially available echocardiographic system
(Vingmed CFM 800, Acuson 128 XP/10, and Hewlett-Packard Sonos 2500)
coupled to a dedicated 3D image-processing unit (Echo-scan, TomTec).
Transthoracic studies were done with rotational scanning
from a subcostal position with a 5-MHz probe mounted on a prototype
rotational device. A stepper motor driven by a steering logic within
the computer allowed rotation of the probe in 2° increments around a
180° arc, thereby acquiring 90 sequential cross-sectional slices of
the heart over an entire scan. ECG and respiratory gating were used to
optimize spatial and temporal resolution.
Transesophageal acquisitions (Vingmed CFM 800) were
obtained in a similar rotational manner with a 5-MHz, 64-element
multiplane probe with its control knob connected by a mechanical
linkage to the stepper motor. During acquisitions, careful attention
was paid to ensure that the resulting conical data set included the
entire interventricular septum and surrounding structures.
Acquisition times were typically 60 to 90 seconds, and 2 to 3
acquisitions were usually performed on each patient.
Storage of the digital images in a volume matrix required 
5
minutes. Manipulation of the data set was performed off-line as
previously described.9 From the postprocessed
data, a cut plane was placed through the LV from base to apex (Figure 2A), parallel to the
ventricular septum, and an en face view of the LV septal
surface was rendered (Figure 2B). Optimal threshold and opacity values
were selected to identify the borders of the VSD. Ultimate
reconstruction time varied considerably, depending on the complexity of
the VSD, and ranged from 10 minutes for many perimembranous VSDs to 60
minutes for more complex defects.
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Figure 2. A, Cut plane used to obtain LV en face image of a
perimembranous VSD. B, Volume-rendered display of a perimembranous
VSD from a 3-chamber LV en face view. C, A 3D reconstruction of a
different perimembranous VSD from LV en face view demonstrating thin
ridge of tissue just beneath aortic valve (arrows). D, LV en face view
of a third perimembranous defect. Tissue can be seen through defect on
RV side, which is either tricuspid valve tissue or remnants of the
membranous septum (arrow). Ao indicates aorta; LA, left atrium; and
AoV, aortic valve.
All echocardiograms were analyzed by 3 experienced
observers. Two observers were blinded to the 2DE findings and any
cardiac catheterization or surgical details. Assessment
of the position, size, and shape of the VSD and observations relating
to surrounding structures were made independently by the blinded
observers. From the volume-rendered display, orthogonal major and minor
axis measurements of the VSD were made with electronic calipers.
Interobserver variability was assessed by comparing measurements made
by 2 observers in 10 patients. In the same 10 patients, the
intraobserver variability was determined by reconstructing the VSD at a
later time and repeating the major and minor diameter measurements.
Results are expressed as mean±SD. The relations between
diameters calculated with 3DE and pathological or surgical measurements
were analyzed by linear regression analysis. The
agreement between the 2 methods was evaluated according to the method
of Bland and Altman.10 Variability was expressed
as a percentage error of each measurement and determined as the
difference between the 2 measurements divided by the mean value of the
2 measurements. Statistical significance was defined as
P<0.05.
Results
Top
Abstract
Introduction
Methods
Results
Discussion
References
In Vitro Study
Optimal reconstructions were obtained in all heart specimens,
accurately depicting the positions and shapes of the VSDs (Figure 1).
The mean major axis VSD diameter measurement in the anatomic specimens
was 10.0±3.8 mm (range, 4.0 to 16.0 mm), and the mean 3DE
measurement was 10.4±4.3 mm (range, 5.0 to 19.0 mm). The
mean difference between the 2 measurements was 0.4±2.0 mm
(P>0.05); the 95% CI was -0.6 to 1.5 mm; and the
95% limits of agreement for the differences were -3.5 and 4.4 mm
(r=0.88; y=1.0x+0.3; SEE=0.14;
P<0.001) (Figure 3A and 3B).
In the same 17 anatomic specimens, the mean minor axis VSD diameter
measurement was 8.9±3.1 mm (range, 4.0 to 15.0 mm), and the
mean 3DE measurement was 7.9±3.6 mm (range, 3.0 to 15.0 mm).
The mean difference between the 2 measurements was -1.0±1.6 mm
(P=0.020); the 95% CI was -1.9 to -0.2 mm; and the
95% limits of agreement for the difference were -4.3 and 2.2 mm
(r=0.89; y=1.0x-1.4; SEE=0.07;
P<0.001) (Figure 3C and 3D). The statistically significant
mean difference reveals a bias of the 3DE measurements toward an
underestimation of the anatomic measurements. Interobserver variability
was 9.8% for the major axis diameter and 7.1% for the minor axis
diameter.
View larger version (33K):
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Figure 3. Regression analysis comparing
anatomic and 3DE measurements of VSD major diameter (A) and
minor diameter (B) from experimental model. Agreement is
shown between anatomy and 3DE measurements of VSD major
diameter (C) and minor diameter (D).10
Optimal 3D LV en face reconstructions permitting assessment of the
position, size, and shape of the defect(s) could be obtained in all 4
of the transesophageal and 41 of the 47
transthoracic studies. Excessive patient or transducer
motion or both prevented adequate reconstruction in 4 infants. In 2
patients, the subcostal 2D images were suboptimal, and the rendered
data sets were unsuitable for 3D reconstruction. In all 45 optimal
reconstructions, the position of the VSD was identified. Twenty-nine of
these patients subsequently underwent surgical closure, at which time
the 3DE diagnosis of the type and position of the VSD was
confirmed. ). The
entire circumference of the defect could be easily identified in
relationship to the smooth-walled LV septal surface. The ratio between
major and minor axis diameter was >1.3 in 20 of the defects, depicting
the defect as oval. In 5 patients, a short ridge of tissue separated
the superior margin of the defect from the aortic valve (Figure 2C).
Certain large defects could be seen extending into the inlet or outlet
regions. In 19 patients, separate echo-dense projections could be
imaged through the defect into the RV, presumably
representing either the septal leaflet of the tricuspid
valve or remnants of the membranous septum (Figure 2D). These
characteristic findings were subsequently confirmed at surgery in 23
patients. ). The relationship of the VSD to the
anterior or posterior muscular septum and toward the base or apex of
the LV could be appreciated by use of this unique en face view. Various
VSD shapes were delineated, including circular, oval, triangular, and
crescentic (Figure 4A through 4C). Multiple muscular VSDs were
identified in 3 patients. The individual defects could be delineated by
3DE but were not apparent by conventional 2DE (Figure 4D). Both
muscular and perimembranous defects could be appreciated by 3DE
reconstruction in 3 patients. In 5 of the patients with muscular VSDs,
the positions of the defects were subsequently confirmed at
surgery.
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Figure 4. A, LV en face view of an oval, midmuscular VSD.
Defect opening is largely obscured by RV muscle bundle, as seen through
VSD. B, Large, triangular muscular VSD. C, Large, crescentic muscular
VSD. D, Multiple muscular VSDs. LA indicates left atrium. ). Further delineation
of the precise position of the defect was achieved with an RV en face
projection. This projection revealed an unobstructed view of
the defect immediately below the pulmonic valve in the supracristal
region of the right-sided interventricular septum (Figure 5B). Two of these patients had prolapse of the right aortic cusp
identified by 3DE before surgery.
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Figure 5. A 3D reconstruction of a doubly committed
subarterial VSD. A, LV en face view demonstrates position
of defect beneath the aortic valve (AoV). B, From RV side,
defect is seen immediately below pulmonic valve (PV), far removed from
the tricuspid valve. Ao indicates aorta; LA, left atrium; RA, right
atrium; PV, pulmonary vein; and PA, pulmonary
artery. and 6B).
The mean minor axis diameter measured at surgery was 5.8±1.8 mm
(range, 3.0 to 11.0 mm), and the mean 3DE measurement was
6.3±1.5 mm (range, 4.0 to 9.6 mm). The mean difference
between the 2 measurements was 0.5±0.8 mm (P=0.007);
the 95% CI was 0.1 to 0.8 mm; and the 95% limits of agreement
for the difference were -1.1 and 2.0 mm (r=0.91;
y=0.73x+2.0; P<0.001) (Figure 6C and 6D). The statistically significant mean difference for both the major
and minor axis diameters reveals a small but observable bias of the 3DE
measurements toward overestimation of the surgical measurements.
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Figure 6. Regression analysis comparing
surgical and 3DE measurements of VSD major diameter (A) and minor
diameter (B) from 25 clinical study patients. Agreement is shown
between surgical and 3DE measurements of VSD major diameter (C) and
minor diameter (D).10
Discussion
Top
Abstract
Introduction
Methods
Results
Discussion
References
This study demonstrates that 3DE accurately depicts the positions,
sizes, and shapes of various types of VSDs. The methodology was
substantiated in an experimental model, and then the basic principles
were extended to a clinical study. Specific cut planes were developed,
and unique images from the LV side were rendered to serve as a future
reference for subsequent studies. 15% of patients, a
small, thin rim of tissue, <2 mm in length, was interposed
between the aortic valve and superior rim of the defect. Additionally,
echo-dense projections could often be imaged through the defect on
the RV side. We assume that this represents either tricuspid
valve tissue or remnants of the membranous septum. From the LV cut
plane, certain large perimembranous defects could be seen extending
posteriorly to the AV septum or inferiorly to the muscular
septum.
References
Top
Abstract
Introduction
Methods
Results
Discussion
References
1.
Bierman FZ, Fellows K, Williams RG. Prospective
identification of ventricular septal defects in infancy
using subxiphoid two-dimensional echocardiography.
Circulation. 1980;62:807–817.
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