AJR 2000; 174:242-244
© American Roentgen Ray Society
Focal Hypertrophic Cardiomyopathy Simulating a Mass
MR Tagging for Correct Diagnosis
Philip D. Bergey1 and
Leon Axel1
1
Both authors: Department of Radiology, University of Pennsylvania Medical
Center, 3400 Spruce St., Philadelphia PA 19104-6100
Received November 9, 1998;
accepted after revision May 10, 1999.
Supported in part by National Institutes of Health grant RR02305.
Address correspondence to P.D. Bergey.
Introduction
MR tagging refers to an ensemble of techniques that noninvasively and
magnetically label tissue elements so their positions can be tracked as a
function of time with MR imaging. One such tagging technique—spatial
modulation of magnetization—is useful for the qualitative and
quantitative evaluation of heart wall motion
[1,
2,
3,
4,
5,
6,
7].
A common problem in cardiac MR imaging is the evaluation of a suspected
space-occupying mass in the wall of the heart. Bouton et al.
[8] showed that MR tagging
helps to define the edges of a space-occupying cardiac mass because of the
absence of active contraction in the mass. This report makes the converse
point: namely, that when cardiac hypertrophy is localized and masslike, MR
tagging confirms the presence of contractile function in the suspected mass,
thus helping to make the correct diagnosis. This hypothesis is consistent with
previous work [4,
5] that showed that
hypertrophic cardiomyopathy is characterized by reduced myocardial segment
shortening compared with that of healthy myocardium.
Materials and Methods
Image Acquisition
Cardiac MR imaging was performed on a conventional 1.5-T MR imaging system
(Signa; General Electric Medical Systems, Milwaukee, WI) using spatial
modulation of magnetization pulse sequences developed in house. For the first
patient we examined, an ECG-gated spin-echo sequence was used (data matrix,
256 x 128; slice thickness, 5 mm; TR, equal to the R-R interval; TE, 20
msec; two signals averaged)
[2]. For the second patient we
examined, an ECG-gated segmented K-space, low flip angle gradient-echo
sequence with two-dimensional spatial modulation of magnetization tagging
pulses was used (data matrix, 256 x 128; slice thickness, 8 mm; TR/TE,
6.5/2.6; flip angle, 20°; no signal averaging; eight views per segment)
[7]. In both examinations,
tagging pulses were applied once per cardiac cycle, a few milliseconds after
the R wave of the ECG. Tagged images were captured at several trigger delays
throughout systole, so that tag displacement and deformation indicated
systolic contractile function in the myocardium.
Patient Studies
The first patient we studied was a 51-year-old healthy woman who underwent
ECG and echocardiography because of a cardiac murmur; she had no other
complaints. ECG revealed a left axis and precordial Q waves, raising the
question of prior myocardial infarction. Echocardiography showed a possible
cardiac mass, and MR imaging was performed for further evaluation.
The second patient was a 27-year-old man with dizziness and a cardiac
murmur in whom both transthoracic and transesophageal echocardiograms were
consistent with hypertrophic cardiomyopathy. Both echocardiograms showed a
2-cm discrete pedunculated portion of the interventricular septum bulging in
the right ventricular outflow tract. We thought that this was consistent with
a variant of hypertrophic cardiomyopathy, but a cardiac neoplasm could not be
excluded. MR imaging was performed to obtain greater specificity.
Results
ECG-gated spin-echo images of the first patient in the short-axis plane of
orientation (Fig. 1A) showed
localized masslike thickening of the left ventricular free wall, which was
isointense to the rest of the myocardium. Gadolinium contrast agent
enhancement of the focally thickened region was similar, but not identical, to
that of adjacent myocardium. ECG-gated spin-echo images with two-dimensional
spatial modulation of magnetization (Fig.
1B) showed that throughout systole, tag displacement and
deformation occurred both in the region of localized thickening and in the
adjacent, more healthy myocardium. Moreover, tag deformation varied smoothly
across the observed myocardium, with no obvious interface or discontinuity. In
both the region of focal thickening and the adjacent healthy wall, there was
circumferential shortening and radial elongation during systole, although the
amount of regional contraction was relatively reduced in the focally thickened
area. Clinical suspicion of neoplasm persisted, and the patient had an open
biopsy 10 weeks after MR imaging. The final microscopic diagnosis was
hypertrophied myocardial fibers with interdigitating fibrosis and no evidence
of neoplasm. The patient did well after surgery and had follow-up MR imaging 6
months later, approximately 38 weeks after the first MR imaging was performed;
findings were unchanged at that time.
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Fig. 1 .—51-year-old asymptomatic woman.
A, Short-axis MR image shows localized hypertrophy in left
ventricular free wall, simulating mass. Imaging was performed using ECG-gated
spin-echo sequence (data matrix, 256 x 128; slice thickness, 5 mm;
TR/TE, 600/20; two signals averaged; trigger delay, 188 msec after R
wave).
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Fig. 1 .—51-year-old asymptomatic woman.
B, Short-axis tagged MR images obtained at five successive trigger
delays show active displacement and deformation of tags in region of localized
hypertrophy. Imaging was performed using ECG-gated, spin-echo sequence (data
matrix, 256 x 128; slice thickness, 5 mm, TR/TE, 632/20; two signals
averaged). Trigger delays are indicated in msec.
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ECG-gated spin-echo images of the second patient, in the transverse plane
(Fig. 2A), showed generalized
hypertrophy with marked localized thickening of the interventricular septum,
which was bulging in the right ventricular outflow tract. ECG-gated segmented
gradientecho images with two-dimensional spatial modulation of magnetization,
in the long-axis plane transverse to the septum
(Fig. 2B), showed active
contractile function in the region of septal thickening. The MR imaging
diagnosis was hypertrophic cardiomyopathy with evidence of right ventricular
outflow obstruction. In this patient, the correct diagnosis became apparent in
two ways. First, tagged images revealed that all parts of the septum
contracted actively, excluding a space-occupying mass. Second, we were able to
exclude a tumor on morphologic grounds by moving from the transverse image
plane (Fig. 2A), in which a
lobulated portion of hypertrophied septum was seen bulging in the right
ventricle, to the oblique long-axis plane transverse to the septum
(Fig. 2B), in which the septum
had a configuration typical of hypertrophic cardiomyopathy. The patient did
well with conventional treatment of his condition and was followed for more
than 2 years after the MR imaging study without clinical deterioration.
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Fig. 2 .—27-year-old man with hypertrophic cardiomyopathy.
A, Transverse MR image shows localized hypertrophy in
interventricular septum, simulating mass. Imaging was performed using
ECG-gated spin-echo sequence (data matrix, 256 x 128; slice thickness, 5
mm; TR/TE, 952/11; two signals averaged; trigger delay, 231 msec after R
wave). This image plane shows lobulated pseudomass bulging into right
ventricle. Best practice is to acquire tagged images in same plane, which
preserves worrisome morphology and shows contraction within morphology via
tags. Altering image plane (as in B) may show septal thickening in
characteristic configuration that dispels concern about mass, facilitating
correct diagnosis. Ideally, two strategies complement one another.
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Fig. 2 .—27-year-old man with hypertrophic cardiomyopathy.
B, Long-axis tagged MR images obtained at five successive trigger
delays show active displacement and deformation of tags in region of localized
hypertrophy. Imaging was performed using ECG-gated segmented K-space, low flip
angle gradient-echo sequence (data matrix, 256 x 128; slice thickness, 8
mm; TR/TE, 6.5/2.6; flip angle, 20°; no signal averaging; eight views per
segment). Trigger delays are indicated in msec. Moving from transverse plane
(A) to oblique long-axis plane transverse to septum (B) alters
configuration of septal hypertrophy, which now appears less masslike. It is
probably better to acquire tagged MR images in exact plane that shows
worrisome pseudomass, which facilitates showing that questionable tissue is
contractile.
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Discussion
When using MR imaging to evaluate a possible space-occupying mass,
morphology and signal intensity are often consistent, but on occasion they may
seem to conflict. In both of our patients, localized regions of hypertrophic
myocardium simulated space-occupying masses, but these regions were
approximately isointense to adjacent myocardium, and there was no other sharp
demarcation in regional MR imaging appearance between mass and uninvolved
heart muscle. Contractile function, as revealed with MR tagging, is an
additional property that can be used to characterize the questionable tissue
as either functionally similar to or different from adjacent myocardial
segments. When Bouton et al.
[8] exploited this principle to
characterize a rhabdomyoma by its lack of contractile function, they
implicitly accepted the idea that actively contracting tissue is
nonneoplastic. To our knowledge, the converse point has never been documented
in the literature. MR tagging is a useful adjunct in the clinical imaging of
suspected cardiac masses, and it can be used to help either exclude or
establish the presence of neoplasm. Further work is needed to define the
sensitivity and specificity of the tagging technique and to expose its
possible pitfalls. In theory, infiltrative conditions affecting the myocardium
present a particular challenge. Hypertrophic cardiomyopathy is, in a sense,
such a condition, because the pathologic finding of interstitial fibrosis is
described [9]. Other forms of
infiltrative cardiomyopathy, such as sarcoid or amyloid, or even some cases of
ischemic cardiomyopathy, may masquerade as space-occupying tumors on tagged MR
images if the contraction of residual myocardial tissue is inapparent. Perhaps
more serious, infiltrating lymphoma or metastatic tumor may be misdiagnosed if
the infiltrated myocardium contracts enough to simulate one of the benign
infiltrative cardiomyopathies. These questions emphasize the preliminary
nature of our work and the need for further study.
References
-
Axel L, Dougherty L. MR imaging of motion with spatial modulation
of magnetization. Radiology
1989;171:841-845[Abstract/Free Full Text]
-
Axel L, Dougherty L. Heart wall motion: improved method of spatial
modulation of magnetization for MR imaging. Radiology
1989;172:349-350[Abstract/Free Full Text]
-
Clark NR, Reichek N, Bergey P, et al. Circumferential myocardial
shortening in the normal human left ventricle: assessment by magnetic
resonance imaging using spatial modulation of magnetization.
Circulation
1991;84:67-74[Abstract/Free Full Text]
-
Kramer CM, Reichek N, Ferrari VA, Theobold T, Dawson J, Axel L.
Regional heterogeneity of function in hypertrophic cardiomyopathy.
Circulation
1994;90:186-194[Abstract/Free Full Text]
-
Young AA, Kramer CM, Ferrari VA, Axel L, Reichek N.
Three-dimensional left ventricular deformation in hypertrophic cardiomyopathy.
Circulation
1994;90:854-867[Abstract/Free Full Text]
-
Young AA, Imai H, Chang CN, Axel L. Two-dimensional left
ventricular deformation during systole using magnetic resonance imaging with
spatial modulation of magnetization. Circulation
1994;89:740-752[Abstract/Free Full Text]
-
Fayad ZA, Ferrari VA, Kraitchman DL, et al. Right ventricular
regional function using MR tagging: normals versus chronic pulmonary
hypertension. Magn Reson Med
1998;39:116-123[Medline]
-
Bouton S, Yang A, McCrindle BW, Kidd L, McVeigh ER, Zerhouni EA.
Differentiation of tumor from viable myocardium using cardiac tagging with MR
imaging. J Comput Assist Tomogr
1991;15:676-678[Medline]
-
Anderson KR, Sutton MG, Lie JT. Histopathological types of cardiac
fibrosis in myocardial disease. J Pathol
1979;128:79-85[Medline]
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Introduction
Materials and Methods
