(Circulation. 1995;92:3473-3480.)
© 1995 American Heart Association, Inc.
Articles |
Imaging and Sizing of Atrial Septal Defects by Magnetic Resonance
Presented in part at the 40th Annual Scientific Session, American College of Cardiology, Atlanta, Ga, March 3-7, 1991, and published in abstract form in J Am Coll Cardiol (1991;17:326A).
From the Cardiac Unit (G.H., I.F.P., R.R.L., P.C.B., B.B., H.L.K.), the Department of Radiology (G.H., R.E.D., S.W.M., T.J.B.), and the Department of Surgery (G.J.V.), Massachusetts General Hospital and Harvard Medical School, Boston, Mass.
Correspondence and reprint requests to Godtfred Holmvang, MD, Boston Heart Foundation, 139 Main St, Cambridge, MA 02142.
 |
Abstract |
|---|
 Top Abstract IntroductionMethods Results Discussion References |
|---|
Background Development of techniques for percutaneous closure of atrial septal defects (ASDs) makes accurate noninvasive sizing of ASDs important for appropriate patient selection.
Methods and Results Magnetic resonance (MR) images of ASDs were obtained in 30 patients (mean age, 41±16 years) by both spin-echo and phase-contrast cine MR imaging. Spin-echo images were obtained in two orthogonal views (short-axis and four-chamber) perpendicular to the plane of the ASD. Spin-echo major and minor diameters were measured, and spin-echo defect area was calculated. Phase-contrast cine MR images were obtained in the plane of the ASD, and cine major diameter and defect area were measured from the region of signal enhancement or phase change due to shunt flow across the defect. MR measurements were compared with templates cut during surgery to match the defect or with ASD diameter determined by balloon sizing at catheterization. ASD size measured from cine MR images (y) agreed closely with catheterization and template standards (x). For major diameter, y=0.78x+5.7, r=.93, and SEE=3.4 mm. On average, spin-echo measurements overestimated major diameter and area of secundum ASDs by 48% and 125%, respectively.
Conclusions Phase-contrast cine MR images acquired in the plane of an ASD define the defect shape by the cross section of the shunt flow stream and allow noninvasive determination of defect size with sufficient accuracy to permit stratification of patients to closure of the defect by catheter-based techniques versus surgery. Spin-echo images, on the other hand, are not adequate for defining ASD size, because septal thinning adjacent to a secundum ASD may appear to be part of the defect.
Key Words: heart defects, congenital • magnetic resonance imaging • shunts • transcatheter closure
|
Introduction |
|---|
|
TopAbstractIntroductionMethods Results Discussion References |
|---|
As improved methods for nonsurgical closure of ASDs become available, an accurate noninvasive technique for sizing ASDs will be of value for selecting patients for this procedure. Such a technique will be particularly helpful when a patient with an uncomplicated ASD is a candidate to go directly to surgery without catheterization if the defect size is too large to permit percutaneous closure. Appropriate selection of patients for percutaneous closure also requires evaluation of the proximity of the defect to other cardiac structures such as the atrioventricular valves, the venae cavae, and the pulmonary veins and exclusion of the presence of multiple defects or the presence of associated lesions such as anomalous pulmonary venous drainage.
Visualization of ASDs by MRI with the spin-echo technique is well established,1 as is the use of dynamic imaging with gradient-echo cine techniques to visualize ASD shunt flow.2 Investigators have also compared the apparent ASD size in spin-echo images with measurements obtained during surgery.3 4
Since our early experience, we have seen examples in which spin-echo measurements of ASD diameter gave misleading results. Here we describe and evaluate a different phase-contrast cine MRI method for determining ASD location, shape, and dimensions. A comparative study of these two MRI techniques, with reference to size data obtained during surgery or in the catheterization laboratory, has not been reported.
|
Methods |
|---|
|
TopAbstractIntroductionMethods Results Discussion References |
|---|
Patient Selection
Fifty-one consecutive patients with a known or suspected ASD underwent an MRI study to determine the defect size and location. In one patient, the septum was intact by both MRI and ultrasound (including transesophageal echo). The other 50 patients had either an ASD or a PFO. Two patients had incomplete MRI data for sizing. In 18 patients, no correlative direct measurements of the defect could be obtained because catheterization or surgery was not clinically indicated, the patient chose not to proceed, the surgery was done elsewhere, or planned catheterization for percutaneous ASD closure awaited availability of a modified device. The MRI sizing technique was validated against an independent standard in the remaining 30 patients, who are the subject of this report. Their average age was 41±16 years (range, 10 to 67 years). The average time between MRI and catheterization or surgery was 42±79 days (range, 0 to 270 days; <2 weeks in 20 patients). All patients were informed about the purpose of the study and agreed to the study, which was performed in accordance with protocol guidelines reviewed and approved by the subcommittee on human studies at our hospital.
Magnetic Resonance Imaging
The MRI studies were performed on
a Technicare system operating
at 0.6 T. The cine images were acquired with a pulse sequence that had
been modified in house from the Technicare source code to allow
velocity encoding or compensation. The last two patients were studied
with a 1.5-T GE Signa scanner.
Multislice spin-echo T1-weighted
diagnostic images were
obtained in the four-chamber view (Fig 1A
) as well
as in a modified short-axis view (defined in the legend of Fig
1).
The slice positions, acquisition order, and gate delay from the R wave
for this short-axis view were adjusted to ensure that the slice
through the middle of the ASD (Fig 1B) was acquired during the
early
diastolic filling period when ASD shunt flow was maximum
(
400 ms after the R wave). This allowed optimal planning from this
short-axis slice of subsequent cine imaging of the shunt flow
stream at the orifice by accurately localizing the ASD plane in space
at the time of peak flow.
|
Three immediately adjacent (no gap) or slightly (25%) overlapping cine MRI acquisitions were obtained sequentially, with the middle slice prescribed in the plane of the ASD. The pulse sequence was velocity-compensated for in-plane flow, but through-plane flow across the ASD produced a velocity- induced phase change. Magnitude and phase images were reconstructed for each cine loop. The phase display was set to avoid extremes of windowing, looking for images in which further adjustments within a range of width and level had minimal effect on apparent defect size, consistent with a flat velocity profile with sharp "shoulders" at the orifice. The acquisition with optimal positioning at the orifice was repeated with full velocity compensation in all directions, producing a fourth cine loop in which the through-plane velocity-induced phase changes had been eliminated. In many patients, cine images were also acquired in the four-chamber view at the level that best showed the ASD in the corresponding spin-echo series.
Before the first cine acquisition,
the gradient-echo pulse sequence
was fine-tuned to ensure that the read gradient was balanced,
resulting in a more nearly flat background when phase images were
reconstructed. Because of hardware limitations, the shortest echo time
achieved was 18.4 ms with full velocity compensation in a 36-cm field
of view. An effective repetition time of 45 ms was used in
combination with a steep excitation angle (60° to 90°) to maximize
magnitude contrast at the ASD from flow-related enhancement in the
shunt stream. Velocity encoding set to 80 to 120 cm/s gave satisfactory
phase contrast at the ASD without aliasing in Signa images.
The greatest lengths over which signal was absent in the interatrial septum in the four-chamber and short-axis spin-echo images were taken as the apparent major and minor diameters of the defect. A spin-echo ASD area was calculated from the standard formula for the area of an ellipse. The cine ASD area was measured by planimetry of the circumference of the cross section of the ASD flow stream as seen in selected frames from the en face cine loops. The maximal ASD diameter by cine MRI was measured directly from the same frames. A mean of 9 (range, 2 to 27) cine images (magnitude and/or phase) were analyzed and the measurements averaged for each patient. In 3 of the 30 patients for whom correlative (surgical or catheterization) data were available, only spin-echo MRI measurements were obtained.
Surgical Data
Fourteen patients in the study group (12 with a
secundum ASD, 1
with an ostium primum ASD, and 1 with a sinus venosus ASD) had their
defects closed surgically. In 12 of these patients, a cardboard
template was cut during surgery to match the size and shape of the
defect just before suturing was to begin. The true major diameter of
each defect was measured directly from the templates, and the area of
each defect was determined by planimetry of a tracing of a
projected contour of each template. In 1 patient, the major and
minor diameters of the defect were measured during surgery, but no
template was made. In the patient with the ostium primum defect, a
spin-echo image in the plane of the ASD was used as the reference
standard.
Catheterization Data
In 19 patients, including 3 who later
went to surgery, a defect
diameter was measured in the catheterization laboratory
by a balloon withdrawal technique described elsewhere.5
The shaft of the catheter proximal to the balloon was used as the
magnification standard, with an external size standard as a backup
reference. In several cases, measurements could also be obtained of the
width of the stream of contrast medium crossing the atrial septum
during filming in the cranially angulated left anterior oblique view of
an injection into the right upper lobe pulmonary vein.
The balloon diameter or the angiographic diameter or an average of the two was used as the catheterization measurement of defect size, depending on the reader's assessment of which measurement provided the clearest definition of the defect edges. From the catheterization-derived diameter, the defect area was calculated assuming a circular orifice. In the three patients who went on to surgical closure of the defect, a template was also obtained, which was used in preference to the catheterization measurement as the true standard for comparison with the MRI data.
|
Results |
|---|
|
TopAbstractIntroductionMethods Results Discussion References |
|---|
Fig 2A
shows the defect orifice as defined by the
transseptal flow in a selected magnitude or phase image from a cine
acquisition in the plane of the ASD for each surgical patient in whom
there were matching views of the reference standard; the latter are
seen in Fig 2B, allowing observation of the close
correspondence
between the true defect shapes and the MR images.
|
The correlations of MRI measurements with
catheterization or surgical data are shown for ASD
major diameter in Figs 3A (spin echo) and 3B (cine MRI)
and for defect area in Figs 3C (spin echo) and 3D (cine MRI). The
regression line equations, SEEs, and correlation coefficients
(r) obtained are given in the figures.
|
) or
by balloon sizing during cardiac catheterization
(
). Heavy open circles indicate two overlapping data points. In
B, heavy dashed lines represent 20-mm limit for eligibility for
ASD closure with clamshell occluder, and light dashed line indicates
MRI measurements 2 SD above this cutoff (see
"Discussion").
If a separate correlation is derived from the data in Fig 3B
for the
surgical subgroup, the r value for cine MRI maximum diameter
versus template measurements (the better of the two reference
standards) is r=.93. For the group measured by balloon
sizing, it is r=.75.
If we exclude the two patients in whom no interatrial communication
with shunt flow was demonstrated (the two points on the x
axis in Fig 3B), a more meaningful estimate of the accuracy of
cine MRI
for measuring maximum diameter is obtained, because this MRI method
does not apply to these two cases. (The technique depends on
transseptal flow; the absence of such flow provides no information
about the size of potential defects and does not mean that the size
must be zero.) The equation for the regression line for cine MRI
diameter versus catheterization or surgical data then
becomes y=0.78x+5.7, r=.93, and
SEE=3.4 mm.
The average defect size in this study was 23 mm, as calculated both
from the cine MRI data and from the
surgical/catheterization data. Thus, cine MRI
measurements of the largest diameter of the shunt flow stream across
the septum did not systematically overestimate or underestimate the
defect size. By spin echo, however, the size of secundum ASDs was
larger than the reference standard by an average of 48% for major
diameter and 125% for defect area; the spin-echo area was larger
than the standard in all but 4 of these 28 patients. Overestimation by
spin echo is also suggested by the higher intercepts of the
spin-echo regression lines on the MRI axes in Fig 3. The
dimensions
of secundum ASDs from spin-echo images were larger than those by
cine MRI in all but three measurements of both major diameter and
area.
|
Discussion |
|---|
|
TopAbstractIntroductionMethods Results Discussion References |
|---|
Patients with a clinically suspected ASD first require confirmation of this diagnosis. Secundum ASDs may present diagnostic difficulty because of false-positive diagnoses caused by "signal dropout" commonly observed in the central portion of the interatrial septum in spin-echo images. This is related to the normal thinning of the septum at the fossa ovalis, and direct visualization of the shunt flow with a bright-blood cine MRI technique2 is frequently necessary to diagnose an ASD. This technique may reveal the defect dimension (defined by the transseptal flow) to be significantly smaller than the extent of the signal absence in the septum (Fig 4
). Thus,
spin-echo imaging can give erroneously large measurements of ASD
size and is usually by itself not adequate for evaluating secundum
ASDs. Ostium primum and sinus venosus ASDs, on the other hand, are
located primarily in thicker parts of the septum, and these lesions are
defined more reliably by the septal discontinuity in spin-echo
images.
|
Conventional cine MRI may also be inadequate for defining an ASD,
because in some patients a definite signal void does not develop in the
region of the jet (Fig 5A). This is presumably related
to a low interatrial pressure gradient and to the pulse sequence used.
In such cases, shunt flow can be missed entirely in magnitude images.
One solution to this problem is to apply a spatially selective
presaturation pulse during the cine acquisition.6
Alternatively, phase-reconstructed cine images acquired with
appropriate velocity encoding7 can provide greatly
improved definition of the ASD stream (Fig 5B).
|
-Even when the shunt flow is adequately visualized, a cine acquisition at a single level through an ASD may not fall at its widest diameter. A stack of contiguous cine images across the defect would therefore be needed to define the widest dimension in that view and its orthogonal extent. However, this increases imaging time and/or spin saturation across slices, and the resolution in the stacked direction would be low (determined by the slice thickness). Additional cines of the jet acquired instead in a view orthogonal to the first could again fail to align with the maximal defect diameter. Cine MRI in views that show the long axis of the jet are therefore suboptimal for fully defining the size and shape of ASDs.
Our experience has been that the best strategy for defining ASD shape
and dimensions is to acquire cine images of the shunt stream in a cross
section located precisely in the plane of the orifice, as defined in
"Methods." The ASD is then outlined by flow-related signal
enhancement in the flow crossing the imaging plane through the defect
(magnitude images in Fig 2A); this becomes an effective
additional
contrast mechanism that is not available in views in which the flow
lies within the imaging plane.
Definition of the ASD in this view from flow contrast at the orifice is
further amplified if the cine images are acquired with velocity
encoding in the slice selection direction (ie, in the direction of ASD
flow). In the resulting phase images, the shunt flow is seen as a
velocity-induced phase change relative to the immediate
surroundings (phase images in Fig 2A). This may allow
identification of
an ASD that is not apparent in the magnitude image, or the phase image
may define the ASD circumference more completely or more sharply. Minor
signal intensity variations in a magnitude image can be windowed to
appear deceptively as an ASD, and phase images should always be used to
confirm whether or not an area of questionable flow-related
enhancement is in fact generated by inflow through an ASD.
In this study, a localized phase change was verified as resulting from
ASD shunt flow rather than another cause, by observation of its
disappearance in a second acquisition at the location best positioned
in the orifice, this time with full velocity compensation in the slice
direction (Fig 6). If these two sets of phase images are
subtracted (and in the absence of eddy current effects), all background
phase, including variations related to field inhomogeneity and chemical
shift effects, should cancel out, leaving a phase-contrast image
that shows only phase changes encoded by and proportional to velocity
components orthogonal to the image plane. Although phase-velocity
maps created by such difference images have a "cleaner"
appearance (Fig 2A, top left), we did not routinely perform the
subtractions because the process was not automated on our system, and
the unsubtracted phase images could still be readily interpreted and
ASD dimensions measured without this extra step.
|
Proper selection of cine frames at the orifice is critical to the
accuracy of ASD size measurements. During the cardiac cycle, the jet
structure moves to a limited extent with the orifice in an axial
direction in and out of the en face imaging plane (which is fixed in
space). The cross-sectional images of the shunt flow selected for
measurement must therefore be verified against the known morphology of
the jet (Fig 7). Frames acquired near end systole and
during the early diastolic filling period usually
demonstrate greatest flow (in agreement with echo Doppler
observations8 ) and therefore show the shunt orifice most
clearly, although timing at end diastole may also give good
definition of the flow stream.
|
One might expect the defect size to be overestimated if measured in images acquired upstream of the orifice where the jet converges, as well as downstream where it diverges. In some cases, however, the apparent cross section of flow in front of the orifice was somewhat smaller than the actual orifice size. This is probably because with increasing displacement away from the central axis of flow, the blood converges along trajectories that are progressively less orthogonal to the imaging plane. Consequently, signal from this peripheral zone upstream will not appear bright because the flow-related enhancement mechanism becomes attenuated for these spins, and the reduced component of velocity along the slice selection gradient will result in a less definitive phase change in this zone.
Cine MR magnitude images in the plane of an ASD will frequently exhibit
a halo of low intensity surrounding the bright signal from the coherent
flow at the core of the jet. With shorter echo times, this signal void
becomes less prominent; flow-related signal enhancement or the
phase contrast generated by the selected velocity-encoding gradient
should not be compromised, however. At the orifice (Fig 7 at 0
mm), the
low signal appears as a narrower rim, consistent with shear
effect; this occurs within the borders of the defect, which we
therefore measured to the outer edge of the signal void. Location at
the orifice is confirmed by absence of such shear effect in the
adjacent upstream cine image. A well-developed circumferential
signal void (Fig 7 at +6, +12, and +20 mm)
suggests a level somewhat
downstream from the orifice, where the jet has an enlarging
peripheral zone of turbulence that could lead to
overestimation of defect size. Such a cine acquisition should be
repeated with the slice location shifted upstream as necessary to
position the slice at the orifice.
The spin-echo measurements of diameter or area correlated less well with catheterization or template data than did the cine MRI measurements (r=.70 versus r=.88 for major diameter and r=.62 versus r=.90 for area). The results also show the spin-echo measurements to be significantly larger compared with both cine images and reference standards. We believe that this is because the spin-echo images may show absence of signal where there is septal thinning within the fossa ovalis adjacent to the ASD, thus increasing the apparent defect, whereas the cine images define the real ASD by a cross section of the shunt flow as it is shaped by the orifice.
Cine MRI of shunt flow at the orifice does have some important
limitations. The two PFOs in this study were identified by echo but
were not demonstrated by MRI. Whereas ultrasound studies permit use of
hemodynamic maneuvers such as the Valsalva maneuver to
induce transient transseptal flow detectable with agitated saline
contrast where no such flow is present in the resting state, such
maneuvers cannot be sustained during an MRI acquisition over several
minutes, and significant potential defects may exist at PFOs in the
absence of visible shunt flow at rest in MR cine images. This
limitation of MRI may be overcome in the future by the use of Valsalva
maneuvers during ultrafast MRI acquisitions. Also, if the shunt flow is
not orthogonal to the cine imaging plane (the plane of the atrial
septum), the flow-related enhancement and phase-contrast
effects, which this technique depends on, will be compromised (Fig
8).
|
We have used the Lock Clamshell Occluder (USCI Division, CR Bard Inc)
for percutaneous ASD closure, with the requirement that
the maximal defect diameter must not exceed 50% of the device
diameter.5 The diameter of the largest occluder was 40 mm,
and only patients whose defects measured 
20 mm were therefore
candidates for this procedure. In this study, all but 2 of the 27
patients in Fig 3B were correctly stratified by cine MRI as
candidates
for the clamshell versus requiring surgery (patients 1 and 2). With the
measurement uncertainty for cine MRI found in this study, patients
with MRI diameters from 20 to 27 mm (6 patients in Fig 3B; the
light dotted line is at 2 SD above the 20-mm cutoff, as shown in the
"Results" above) could still be potential nonsurgical candidates.
They could be offered catheterization with a view to
percutaneous closure pending definitive confirmation by
balloon sizing during the procedure that the defect dimension would
allow this.
Other ASD closure devices currently under
evaluation9 10 also typically aim for a 2:1 ratio of
device to defect diameter, and a patient stratification scheme similar
to the above could still be used. MRI can provide an estimate of the
septal rim around a secundum defect from four-chamber and
short-axis as well as from en face views. MRI can also relate the
device size to the space available (width of the interatrial septum
between the arrows in Fig 1B). Together with knowledge of the
orifice
shape (Fig 2A and 2B), including its minor
diameter (which may be
particularly useful with new "self-centering" devices), this
should permit close tailoring of the device to the individual case.
Multiple two-dimensional and color-flow echocardiographic studies have reported correlation coefficients relating ASD dimensions by ultrasound to surgical or balloon measurements. These have ranged from r=.50 to r=.91 for transthoracic echo11 12 13 14 and from r=.73 to r=.92 for TEE studies.14 15 16 17 The correlation coefficient of r=.93 found in this study with phase-contrast cine MRI compares favorably with the best results reported by ultrasound, and the 3.4-mm SEE for MRI is somewhat less than the SEEs reported for echo (4.3 to 4.5 mm).12 14 15 The cine MR images provide a unique en face view, which is valuable because the complete orifice is visualized, thus defining shape as well as dimensions. A similar view of ASDs has recently also been described for three-dimensional reconstructions of the interatrial septum from TEE ultrasound data.18 The role of phase-contrast cine MRI relative to TEE for evaluation of ASDs before closure is yet to be defined. We think that both are strong techniques and that ultimately a number of centers will choose to use MRI for initial stratification to surgical versus catheter intervention because of patient comfort and convenience and the ease with which the entire defect is defined and because MRI in addition allows accurate noninvasive quantification of the shunt,19 20 21 potentially directly from the en face cine images. The TEE study could then be reserved to aid during subsequent percutaneous closure procedures.
We conclude that MRI evaluation of ASDs for nonsurgical closure allows clear localization of the defect in the interatrial septum, with definition of its type as well as its proximity to other cardiac structures. The size of a secundum defect as it appears from the signal loss in the central part of the atrial septum in spin-echo images should not be used as a measure of defect dimensions because of potentially significant overestimation. However, phase-contrast cine MR images of the cross section of the shunt stream at the orifice can yield ASD dimensions and shape with sufficient accuracy to identify patients requiring surgical repair versus those who may be suitable for nonsurgical ASD closure by newly developed catheterization techniques. Small ASDs can be sized as long as transseptal flow is present in the resting state, but cine MRI in the format described here is not a technique for evaluating PFOs; MRI methods may be extended to this application in the future. Careful attention to the multiple details of imaging technique, particularly with respect to localization of the cine imaging plane at the orifice, is required to obtain studies with good image quality from which quantitatively accurate measurements can be made.
|
Selected Abbreviations and Acronyms |
|---|
|
|
Acknowledgments |
|---|
This study was supported in part by a Canadian Heart Foundation fellowship grant. We would like to thank Drs M.E. King, P. Lang, R.S. Lees, R.A. Levine, A.J. Marelli, S.M. Nidorf, and J.D. Thomas for thoughtful discussions of the subject. We would also like to thank Dr H.E. Waldman for help with the balloon sizing and Drs C.W. Akins, M.J. Buckley, and J.C. Madsen for help with obtaining the surgical data. We are grateful to Joe Malysa and the Technicare/Plexar staff for providing the basic version of the gradient-echo pulse sequence source code along with helpful information. Finally, we thank our patients for their participation in this imaging study.
Received February 27, 1995; revision received July 31, 1995; accepted August 6, 1995.
|
References |
|---|
|
TopAbstractIntroductionMethods Results Discussion References |
|---|
1. Diethelm L, Déry R, Lipton MJ, Higgins CB. Atrial-level shunts: sensitivity and specificity of MR in diagnosis. Radiology. 1987;162:181-186.
2. Theissen P, Sechtem U, Mennicken U, Hilger HH, Schicha H. Non-invasive diagnosis of atrial septal defects and anomalous pulmonary venous return by magnetic resonance imaging. Nuklear Medizin. 1989;28:172-180.
3.
Dinsmore RE, Wismer GL, Guyer D, Thompson R, Liu P,
Stratemeier E, Miller S, Okada R, Brady T. Magnetic resonance
imaging of the interatrial septum and atrial septal defects.
AJR Am J Roentgenol. 1985;145:697-703.
4. Sakakibara M, Kobayashi S, Imai H, Watanabe S, Masuda Y, Inagaki Y. Diagnosis of atrial septal defect using magnetic resonance imaging. J Cardiol. 1987;17:817-829. [Medline] [Order article via Infotrieve]
5.
Bridges ND, Hellenbrand W, Latson L, Filiano J,
Newburger JW, Lock JE. Transcatheter closure of
patent foramen ovale after presumed paradoxical embolism.
Circulation. 1992;86:1902-1908.
6. Hartnell G, Sassower M, Finn P. Selective presaturation increases the accuracy of magnetic resonance angiography in the detection of intracardiac shunts. Circulation. 1993;88(suppl I):I-83. Abstract.
7.
Underwood SR, Firmin DN, Klipstein RH, Rees RSO,
Longmore DB. Magnetic resonance velocity mapping: clinical
application of a new technique. Br Heart J. 1987;57:404-412.
8. Lin FC, Fu M, Yeh SJ, Wu D. Doppler atrial shunt flow patterns in patients with secundum atrial septal defect: determinants, limitations, and pitfalls. J Am Soc Echocardiogr. 1988;1:141-149. [Medline] [Order article via Infotrieve]
9. Lloyd TR, Rao S, Beekman RH III, Mendelsohn AM, Sideris EB. Atrial septal defect occlusion with the buttoned device (a multi-institutional U.S. trial). Am J Cardiol. 1994;73:286-291. [Medline] [Order article via Infotrieve]
10. Das GS, Voss G, Jarvis G, Wyche K, Gunther R, Wilson RF. Experimental atrial septal defect closure with a new, transcatheter, self-centering device. Circulation. 1993;88(pt 1):1754-1764.
11. Rao PS, Langhough R, Beekman RH, Lloyd TR, Sideris EB. Echocardiographic estimation of balloon-stretched diameter of secundum atrial septal defect for transcatheter occlusion. Am Heart J. 1992;124:172-175. [Medline] [Order article via Infotrieve]
12. Chen C, Kremer P, Schroeder E, Rodewald G, Bleifeld W. Usefulness of anatomic parameters derived from two-dimensional echocardiography for estimating magnitude of left to right shunt in patients with atrial septal defect. Clin Cardiol. 1987;10:316-321. [Medline] [Order article via Infotrieve]
13. Mehta RH, Helmcke F, Nanda NC, Pinheiro L, Samdarshi TE, Shah VK. Uses and limitations of transthoracic echocardiography in the assessment of atrial septal defect in the adult. Am J Cardiol. 1991;67:288-294. [Medline] [Order article via Infotrieve]
14. Faletra F, Scarpini S, Moreo A, Ciliberto GR, Austoni P, Donatelli F, Gordini V. Color Doppler echocardiographic assessment of atrial septal defect size: correlation with surgical measurements. J Am Soc Echocardiogr. 1991;4:429-434. [Medline] [Order article via Infotrieve]
15.
Hanrath P, Schlüter M, Langenstein BA, Polster J,
Engel S, Kremer P, Krebber HJ. Detection of ostium secundum
atrial septal defects by transesophageal
cross-sectional echocardiography.
Br Heart J. 1983;49:350-358.
16. Morimoto K, Matsuzaki M, Tohma Y, Ono S, Tanaka N, Michishige H, Murata K, Anno Y, Kusukawa R. Diagnosis and quantitative evaluation of secundum-type atrial septal defect by transesophageal Doppler echocardiography. Am J Cardiol. 1990;66:85-91. [Medline] [Order article via Infotrieve]
17. Mehta RH, Helmcke F, Nanda NC, Hsiung M, Pacifico AD, Hsu TL. Transesophageal Doppler color flow mapping assessment of atrial septal defect. J Am Coll Cardiol. 1990;16:1010-1016. [Abstract]
18. Belohlavek M, Foley DA, Gerber TC, Greenleaf JF, Seward JB. Three-dimensional ultrasound imaging of the atrial septum: normal and pathologic anatomy. J Am Coll Cardiol. 1993;22:1673-1678. [Abstract]
19. Holmvang G, Dinsmore RE, Edelman R, Thompson RC, Miller SW, Leavitt M, Brady TJ, Kantor HL. Quantitation of central circulatory shunts by NMR. Circulation. 1986;74(suppl II):II-5. Abstract.
20. Brenner LD, Caputo GR, Mostbeck G, Steiman D, Dulce M, Cheitlin MD, O'Sullivan M, Higgins CB. Quantification of left to right atrial shunts with velocity-encoded cine nuclear magnetic resonance imaging. J Am Coll Cardiol. 1992;20:1246-1250. [Abstract]
21.
Hundley WG, Li HF, Lange RA, Pfeifer DP, Meshack BM,
Willard JE, Landau C, Willett D, Hillis LD, Peshock RM.
Assessment of left-to-right intracardiac shunting by
velocity-encoded, phase-difference magnetic resonance imaging:
a comparison with oximetric and indicator dilution techniques.
Circulation. 1995;91:2955-2960.
This article has been cited by other articles:
 |
|
 |
|
  C. A. Warnes, R. G. Williams, T. M. Bashore, J. S. Child, H. M. Connolly, J. A. Dearani, P. del Nido, J. W. Fasules, T. P. Graham Jr, Z. M. Hijazi, et al. ACC/AHA 2008 Guidelines for the Management of Adults With Congenital Heart Disease: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Develop Guidelines on the Management of Adults With Congenital Heart Disease) Developed in Collaboration With the American Society of Echocardiography, Heart Rhythm Society, International Society for Adult Congenital Heart Disease, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons J. Am. Coll. Cardiol., December 2, 2008; 52(23): e143 - e263. [Full Text] [PDF]
|
|
|
|
 |
|
 C. A. Warnes, R. G. Williams, T. M. Bashore, J. S. Child, H. M. Connolly, J. A. Dearani, P. del Nido, J. W. Fasules, T. P. Graham Jr, Z. M. Hijazi, et al. ACC/AHA 2008 Guidelines for the Management of Adults With Congenital Heart Disease: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Develop Guidelines on the Management of Adults With Congenital Heart Disease): Developed in Collaboration With the American Society of Echocardiography, Heart Rhythm Society, International Society for Adult Congenital Heart Disease, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons Circulation, December 2, 2008; 118(23): e714 - e833. [Full Text] [PDF]
|
|
|
|
 |
|
 L. E.J. Thomson, A. L. Crowley, J. F. Heitner, P. J. Cawley, J. W. Weinsaft, H. W. Kim, M. Parker, R. M. Judd, J. K. Harrison, and R. J. Kim Direct En Face Imaging of Secundum Atrial Septal Defects by Velocity-Encoded Cardiovascular Magnetic Resonance in Patients Evaluated for Possible Transcatheter Closure Circ Cardiovasc Imaging, July 1, 2008; 1(1): 31 - 40. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 O. K. Mohrs, S. E. Petersen, D. Erkapic, C. Rubel, R. Schrader, B. Nowak, W. A. Fach, H.-U. Kauczor, and T. Voigtlaender Diagnosis of Patent Foramen Ovale Using Contrast-Enhanced Dynamic MRI: A Pilot Study Am. J. Roentgenol., January 1, 2005; 184(1): 234 - 240. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Zanchetta, E. Onorato, G. Rigatelli, L. Pedon, M. Zennaro, A. Carrozza, and P. Maiolino Intracardiac echocardiography-guided transcatheter closure of secundum atrial septal defect: A new efficient device selection method J. Am. Coll. Cardiol., November 5, 2003; 42(9): 1677 - 1682. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Lapierre, M.-J. Raboisson, J. Miro, N. Dahdah, and R. Guerin Evaluation of a Large Atrial Septal Occluder with Cardiac MR Imaging RadioGraphics, October 1, 2003; 23(90001): S51 - 58. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Z. J. Wang, G. P. Reddy, M. B. Gotway, B. M. Yeh, and C. B. Higgins Cardiovascular Shunts: MR Imaging Evaluation RadioGraphics, October 1, 2003; 23(90001): S181 - 194. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Beerbaum, H. Korperich, H. Esdorn, U. Blanz, P. Barth, J. Hartmann, J. Gieseke, and H. Meyer Atrial Septal Defects in Pediatric Patients: Noninvasive Sizing with Cardiovascular MR Imaging Radiology, August 1, 2003; 228(2): 361 - 369. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Rickers, M. Jerosch-Herold, X. Hu, N. Murthy, X. Wang, H. Kong, R. T. Seethamraju, J. Weil, and N. M. Wilke Magnetic Resonance Image-Guided Transcatheter Closure of Atrial Septal Defects Circulation, January 7, 2003; 107(1): 132 - 138. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. A. Ferrari, C. H. Scott, G. A. Holland, L. Axel, and M. St. John Sutton Ultrafast three-dimensional contrast-enhanced magnetic resonance angiography and imaging in the diagnosis of partial anomalous pulmonary venous drainage J. Am. Coll. Cardiol., March 15, 2001; 37(4): 1120 - 1128. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Ewert, F. Berger, I. Daehnert, J. van Wees, M. Gittermann, H. Abdul-Khaliq, and P. E. Lange Transcatheter Closure of Atrial Septal Defects Without Fluoroscopy : Feasibility of a New Method Circulation, February 29, 2000; 101(8): 847 - 849. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Lange, M. Walayat, C. M Turnbull, P. Palka, P. Mankad, G. R Sutherland, and M. J Godman Assessment of atrial septal defect morphology by transthoracic three dimensional echocardiography using standard grey scale and Doppler myocardial imaging techniques: comparison with magnetic resonance imaging and intraoperative findings Heart, October 1, 1997; 78(4): 382 - 389. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||