Download Noninvasive Separation of Large, Medium, and Small Myocardial

Noninvasive Separation of Large, Medium, and Small
Myocardial Infarcts in Survivors of Reperfused
ST-Elevation Myocardial Infarction
A Comprehensive Tissue Doppler and Speckle-Tracking
Echocardiography Study
Ola Gjesdal, MD; Thomas Helle-Valle, MD; Einar Hopp, MD; Ketil Lunde, MD;
Trond Vartdal, MD; Svend Aakhus, MD, PhD; Hans-Jørgen Smith, MD, PhD;
Halfdan Ihlen, MD, PhD; Thor Edvardsen, MD, PhD
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Background—The objective of the study was to evaluate the ability of established and new parameters of global systolic
left ventricle function to estimate myocardial infarct size.
Increasing infarct extent is associated with impaired prognosis in chronic ischemic heart disease. Systolic myocardial
deformation is a complex 3D process that is mainly influenced by the amount and transmural distribution of viable
myocardium. Speckle-tracking echocardiography (2D-STE) enables deformation assessment along the 3 main cardiac
axes independent of insonation angle.
Methods and Results—Global longitudinal, circumferential, and radial strain and left ventricle twist by 2D-STE, global
longitudinal strain rate and strain by tissue Doppler imaging, and left ventricle ejection fraction and wall motion score
index were assessed in 40 patients 8.5⫾5.4 months after a first myocardial infarct and compared with global myocardial
infarct mass assessed by contrast-enhanced MRI. Longitudinal and circumferential strain by 2D-STE and longitudinal
strain and strain rate by tissue Doppler imaging significantly separated medium-sized infarcts from small or large
infarcts at the global level (P⬍0.05). All deformation indices correlated significantly with global infarct mass (P⬍0.01).
Circumferential and longitudinal strains by 2D-STE demonstrated the best ability to identify medium-sized global
myocardial infarcts.
Conclusions—Circumferential and longitudinal strains by 2D-STE correlate with myocardial infarct mass and
significantly differentiate among large, medium, and small myocardial infarcts. (Circ Cardiovasc Imaging. 2008;
1:189-196.)
Key Words: infarction 䡲 MRI 䡲 myocardial contraction
䡲 tissue Doppler echocardiography 䡲 speckle-tracking echocardiography
M
MRI examinations, however, are time consuming and expensive, and the availability of scanners are limited. Feasible
techniques for the evaluation of myocardial viability are
strongly needed.
Echocardiographic assessment of left ventricular ejection
fraction (LVEF) is easily available and feasible but is
basically a measure of global LV function. Evaluation of
regional function by analyzes of endocardial motion or local
wall thinning and thickening characteristics require welltrained personnel.
Strain and strain rate (SR) are clinical indices of regional
myocardial deformation6 –9 and have been introduced and
ortality after acute myocardial infarction (MI) is
closely related to infarct size and location.1,2 Clinical
improvement from revascularization therapy depends on the
transmural distribution of necrosis, infarct size, and location.3,4 Risk stratification therefore requires reliable and
feasible clinical tools to measure the exact extent and location
of myocardial necrosis.
Clinical Perspective see p 196
Quantification of MI size by contrast-enhanced MRI (CEMRI) has been validated,5 predicts cardiovascular events,1
and is considered the “gold standard” for infarct assessment.
Received April 14, 2008; accepted September 23, 2008.
From the Departments of Cardiology (O.G., T.H.-V., K.L., T.V., S.A., H.I., T.E.) and Radiology (E.H., H.-J.S.), Rikshospitalet University Hospital,
University of Oslo, Oslo, Norway.
The online-only Data Supplement is available at http://circimaging.ahajournals.org/cgi/content/full/1/3/189/DC1.
Correspondence to Thor Edvardsen, MD, PhD, Department of Cardiology, Rikshospitalet University Hospital, N-0027 Oslo, Norway. E-mail
[email protected]
© 2008 American Heart Association, Inc.
Circ Cardiovasc Imaging is available at http://circimaging.ahajournals.org
189
DOI: 10.1161/CIRCIMAGING.108.784900
190
Table 1.
Circ Cardiovasc Imaging
November 2008
Patient Characteristics
Patients
Table 2.
40
Invasive and Imaging Characteristics
Patients
40
Age, years
58⫾10
LV mass by CE MRI, g
Gender, male:female
30:10
LV mass/BSA, g/m2
86⫾21
Heart rate, min⫺1
58⫾10
LVEF, %
49⫾10
Systolic blood pressure, mm Hg
125⫾22
Diastolic blood pressure, mm Hg
79⫾14
172⫾47
LV EDV, mL
137⫾35
WMSI
1.4⫾0.2
Anterior STEMI
33
Significant LAD stenosis
35
Inferior STEMI
7
Significant LCX stenosis
12
Medication
Significant RCA stenosis
9
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␤-blockers
40
Symptoms-to-balloon time, min
253⫾134
ACE inhibitor or ARB
36
TIMI-flow pre-PCI
1.1⫾1.3
Antiplatelet therapy
40
TIMI-flow post-PCI
3.0⫾0.3
Statin
40
Data are presented as mean⫾SD or n. Stenosis was considered significant
if ⱖ50% lumen obstruction. BSA indicates body surface area; LV EDV, left
ventricular end-diastolic volume; LAD, left anterior descending artery; LCX, left
circumflex artery; RCA, right coronary artery; TIMI, thrombolysis in myocardial
infarction.
Data are presented as mean⫾SD or n. STEMI indicates ST-elevation
myocardial infarction; ACE, angiotensin-converting enzyme; ARB, angiotensinreceptor blocker; BSA, body surface area; LVEDV, left ventricular end-diastolic
volume.
validated using tagged MRI and sonomicrometry.10 –12 To
eliminate the problem of angle dependency of Dopplerderived analyses, strain measurement based on 2D speckletracking echocardiography (2D-STE) has been developed.13–16 2D-STE enables regional deformation assessment
in circumferential, longitudinal, and radial directions,17–20 and
furthermore, the ability to assess LV rotation and twist.13
Recently, global longitudinal strain based on the average of
regional deformations have been shown to predict infarct size
better than LVEF,18,20 but global deformation in the other
directions have not been examined. There is a need to clarify
whether any global deformation parameter is superior in the
evaluation of the failing LV function in ischemic heart
disease.
In the present study, we tested the ability of new and
established echocardiographic indices of global LV function
to estimate myocardial infarct mass assessed by CE-MRI.
Methods
Patient Population
after intravenous injection of 0.1 or 0.2 mmol/kg gadopentetate
dimeglumine (Magnevist, Schering, Berlin, Germany) in multiple
short-axis slices covering the LV (slice thickness, 7 mm; interslice
gap, 3 mm; Figure 1). A breath-hold segmented magnetizationprepared turbo gradient echo sequence was used with an inversion
time of 210 to 260 ms.
The LV myocardium was manually divided into 16 segments,21
and the infarcted as well as the total myocardial area of each segment
was drawn (PACS, Sectra, Sweden). Areas with pixel intensities
more than 2 SDs above the mean pixel intensity of normal myocardium of the same slice were considered infarcted.3,22 The total
myocardial volume and the absolute and relative infarct volumes
were calculated for each segment. The myocardial and infarct masses
were converted from volume by multiplying by 1.05 g/mL,23 and the
global infarct mass was calculated as the sum of all segmental values
for each patient.20 Patients were divided into groups depending on
the global infarct mass: small infarcts of ⬍30 g, medium-sized
infarcts of 30 to 50 g, and large myocardial infarcts of ⱖ50 g.1
The transmural infarct extent of each segment was assessed.
Subendocardial infarct was defined as transmural infarct extent
⬍50% of the segmental myocardial area, whereas transmural infarct
was defined when ⱖ50% was involved.3
Echocardiography
Forty patients (age, 58⫾10 years; 9 women) previously treated with
percutaneous coronary intervention (PCI) because of acute STsegment elevation MI were included in the study. Patients with
contraindications to MRI were excluded, but no patients were
excluded because of impaired echocardiographic image quality. The
clinical data are presented in Table 1, and the infarct characteristics
are shown in Table 2. Patients were examined with CE-MRI and
echocardiography 8.5⫾5.4 months after the index MI. The echocardiographic study was typically performed within 4 hours of the MRI.
Patients were hemodynamically stable during the studies. All study
subjects were in sinus rhythm and had a QRS width ⬍120 ms. None
had significant valvular dysfunction as defined by echocardiography.
The study was approved by the Regional Committee for Medical
Research Ethics (REK Sør, Oslo, Norway), and all subjects gave
written informed consent.
Images were obtained in the left lateral decubitus position. The study
examinations were performed with a Vivid 7 scanner (GE Vingmed
Ultrasound, Horten, Norway), using a phased-array transducer.
Three consecutive heart cycles from the 3 standard apical views
(4-chamber, 2-chamber, and long axis) and 3 short-axis views (basal,
midventricular, and apical levels) were obtained by conventional 2D
grayscale echocardiography, as well as tissue Doppler imaging (TDI)
for the 3 standard apical views, using a narrow sector angle with the
ventricular wall parallel to the ultrasound beam. The average frame
rate was 62⫾23 s⫺1 for long axis, 68⫾21 s⫺1 for short axis, and
115⫾21 s⫺1 for TDI analyses. The digital loops were stored and
analyzed by EchoPac software (EchoPac 6.0, GE Vingmed Ultrasound). LVEF was assessed by the modified Simpson rule. A
16-segment LV model21 was used for strain, SR, and wall motion
score in this study.
MRI
Myocardial Deformation
MRI was performed using 1.5-T units (Magnetom Vision Plus or
Magnetom Sonata, Siemens, Erlangen, Germany) and a phased array
body coil. Late enhancement images were obtained 10 to 20 minutes
Segmental longitudinal strain was assessed by 2D-STE in apical
4-chamber, 2-chamber, and apical long-axis projections, and circumferential and radial strain were assessed in 3 short-axis views (basal,
Gjesdal et al
Deformation Indices Correlate With Infarct Mass
191
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Figure 1. CE-MRI images from patients with a large MI (left; 115 of 273 g) and a medium-sized MI (right; 36 of 140 g). The scaling of
the 2 examples is not identical.
midventricular and apical). The endocardial borders were manually
traced in end systole, and adjusted if the automatic tracking was
considered suboptimal by visual or automated assessment. Segmental strain was automatically calculated as the average strain within
each segment. End systole was defined as aortic valve closure in
apical long-axis view. Peak systolic strain, postsystolic strain, and
maximal strain was assessed, and postsystolic shortening index was
calculated as postsystolic strain divided by maximal strain.24
Peak systolic longitudinal strain and SR were measured by TDI
from the standard LV apical projections. The region of interest was
set to 12⫻6 mm, and representative segmental traces were manually
detected from the basal part of each segment. All global deformation
indices were calculated as the average of the observed segmental
values.
Twist
Rotation was analyzed by 2D-STE in basal and apical short-axes
views. Peak systolic twist was calculated as the difference in
maximal rotation between the 2 levels.13
Wall Motion Score Index
Wall motion was visually assessed according to the American
Society of Echocardiography25 by an experienced observer. The
observer evaluated image quality, and segments were discarded if the
quality were found insufficient for analysis. Wall motion score index
(WMSI) was calculated for each patient as the average of analyzed
segmental values.
Statistical Analysis
The data were analyzed using standard statistical software (SPSS
version 14, SPSS Inc, Chicago, Ill). Continuous variables are
expressed as mean⫾SD, when otherwise is not stated. Differences
between the groups were analyzed with 1-way ANOVA at the global
level. Differences between the segmental groups were analyzed with
a mixed-effects linear model, and adjusted for correlations both
within patients and within regions. Bonferroni correction was applied for all post hoc tests.
Associations of global infarct mass with global values were
analyzed by linear regression (stepwise). The 4 longitudinal deformation parameters (longitudinal strain by TDI or 2D-STE, SR, and
postsystolic shortening index) are internally dependant and were
tested separately first. Only the ones who significantly contributed to
the model (2D-STE strain only) were included in the final model.
Receiver-operating characteristic (ROC) curves were constructed,
and areas under curves were measured. Sensitivities and specificities
for all global deformation indices were determined for ability to
identify medium-sized myocardial infarct, because infarct size has
been proved to predict prognosis.1 For all statistical comparisons,
P⬍0.05 was considered significant.
Statement of Responsibility
The authors had full access to the data and take responsibility for its
integrity. All authors have read and agree to the manuscript as
written.
Results
Feasibility
Infarct mass was analyzed in all (640) LV segments by
CE-MRI. By 2D-STE, the feasibility of longitudinal strain
analyses was 93% of the LV segments, 81% for circumferential strain, and 73% for radial strain. Feasibility was 96%
for longitudinal strain and 95% for SR analyses by TDI.
WMS was analyzed in 98% of the segments. Segments were
excluded because of reverberations, valvular interference,
tracking difficulties, or poor image quality. LVEF, WMSI,
twist, and global deformation parameters were analyzed in all
patients.
MRI
Infarct characteristics are displayed in Table 2. The average
infarct mass was 34⫾27 g (19⫾13% of LV mass). By
CE-MRI, 19 of the patients had small MI, 13 patients had
medium-sized MI, and 8 patients had large MI. The total
number of infarcted LV segments per patient was 7.9⫾4.1
when averaged over all patients, and 2.6⫾2.6 of these
segments were transmurally infarcted.
2D-STE and TDI
Global longitudinal and circumferential strain by speckletracking techniques were able to differentiate among the 3
infarct sizes (P⬍0.01; Table 3), and examples of MRI images
and global strain curves from representative patients with
medium and large MI are displayed (Figures 1 and 2). Global
longitudinal strain and SR by TDI also distinguished signif-
192
Table 3.
Circ Cardiovasc Imaging
November 2008
Mean Values by Global Infarct Mass
Small MI
(n⫽19)
Medium MI
(n⫽13)
Large MI
(n⫽8)
Longitudinal strain, %
⫺17.9⫾1.7
⫺15.3⫾1.9*
⫺11.2⫾3.2*†
Circumferential strain, %
⫺21.6⫾2.8
⫺18.0⫾2.2*
⫺12.4⫾4.1*†
Radial strain, %
⫺1
SR by TDI, s
Strain by TDI, %
30.8⫾6.6
27.0⫾6.1
15.5⫾8.1*†
⫺1.2⫾0.1
⫺1.1⫾0.1*
⫺0.9⫾0.2)*†
⫺17.4⫾2.0
⫺14.9⫾1.9*
⫺11.5⫾3.1*†
PSSI
6.3⫾5.3
11.9⫾6.5
25.1⫾10.2*†
Twist
20⫾5
16⫾4
13⫾5*
WMSI
1.2⫾0.1
1.4⫾0.2
1.7⫾0.2*†
LVEF, %
55⫾7
48⫾6
40⫾12*
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Data are presented as mean⫾SD, grouped by global infarct mass as
assessed by CE-MRI. Small infarcts are defined as ⬍30 g; medium-sized
infarcts, 30 –50 g; and large infarcts, ⱖ50 g. PSSI indicates postsystolic
shortening index.
*P⬍0.05 versus small MI.
†P⬍0.05 versus medium MI.
icantly among 3 different sizes of LV infarct mass (P⬍0.05).
Global radial strain and postsystolic shortening index separated large MI from medium or small MI (P⬍0.01) but failed
to separate the smallest infarct groups.
All global strain and SR indices correlated significantly
(P⬍0.01) with infarct mass (Figure 3) but with a lower
correlation coefficient for radial strain and postsystolic shortening index. Global longitudinal strain assessed by speckle
tracking and TDI were strongly related (r⫽0.91; P⬍0.01).
ROC analysis was performed for all global indices to
identify sensitivities and specificities for the detection of
medium-sized MI (Figure 4). The sensitivity and specificity
was generally good for all 2D-STE strain parameters. By
visual comparison, 2D-STE longitudinal and circumferential
strain seems somewhat better than radial strain to detect
medium-sized MI.
At the segmental level, all strain directions by 2D-STE as
well as the TDI indices separated significantly between the
different levels of infarct transmurality (Table 4; P⬍0.01).
Using ROC analysis, longitudinal strain by 2D-STE revealed
the highest sensitivity and specificity for detection of transmural segmental MI.
LVEF, WMS, and LV Twist
WMSI failed to separate small from medium MI (P⫽0.14)
but could differentiate large MI both from small and medium
MI (P⬍0.01). LVEF and LV twist separated significantly
(P⬍0.01) between small and large infarct. Correlations to
global infarct mass were significant both for LVEF, WMSI,
and LV twist (P⬍0.01; Figure 3). By visual assessment, ROC
analysis showed reduced sensitivity and specificity for detecting the smallest infarctions compared with the strain
techniques (Figure 4).
Multivariate Analyses
In a multivariate regression model only longitudinal and
circumferential strain by speckle-tracking echocardiography
contributed significantly to the description of the global
infarct size (Table 5). Including both circumferential and
longitudinal strain in the model increased the correlation
coefficient to 0.88 with a constant of 144⫾10.
Discussion
A number of echocardiographic indices have been introduced
during the last 2 decades for assessment of segmental
myocardial function. Myocardial strain has demonstrated to
be superior compared with myocardial velocity parameters by
TDI.8 The recent development of STE permits assessment of
global myocardial deformation independently of insonation
angle.
The present study is the first to describe and directly
compare global myocardial deformation parameters and to
test their ability to quantify global myocardial infarct mass.
Global shortening strains by 2D-STE and TDI were excellent
markers of global infarct mass as assessed by CE-MRI and
could clearly separate small, middle, and large MI. Radial
strain and the traditional parameters LVEF and WMSI,
however, displayed inferior ability to identify the smallest
infarcts. The global strain methods are probably the best
available tools for assessment of global infarct size in the
clinical setting.
3D Deformation
Myocardial motion is complex. Myocardial fibers orientation
gradually shifts from a counterclockwise oblique longitudinal
direction in the endocardial layer, to near circumferential in
the midmyocardial layer, and clockwise oblique longitudinal
in the subepicardial layer.26 Three main deformation patterns
form perpendicular axes in a local heart coordinate system:27
longitudinal shortening, circumferential shortening, and radial thickening. In addition, shear strains and LV twist caused
Figure 2. Global strain assessment. Global
strain curves from the same patients as in Figure 1. Large MI is shown on the left and
medium-sized MI on the right. Longitudinal
strain (red) was assessed in apical 2-chamber,
4-chamber, and long-axis views; circumferential
strain (black) and radial strain (blue) were
assessed in basal, midventricular, and apical
short-axis views. An ECG trace is displayed
below the strain curves. ES indicates end
systole.
Gjesdal et al
Deformation Indices Correlate With Infarct Mass
193
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Figure 4. ROC analysis set to identify global infarct mass of
ⱖ30 g. TDI indicates tissue Doppler imaging.
Figure 3. Correlation plots with global infarct mass (in grams)
by CE-MRI (y axis) and various indices of global LV function
(x axis). Correlation equations, correlation coefficients (r), and
standard error of the estimate (SEE) are displayed. TDI indicates
tissue Doppler imaging. All correlations
are significant (P⬍0.01).
by deformation variation within the myocardial wall have
been described by MRI.28
A close relationship between infarct transmurality by
CE-MRI and segmental circumferential or radial strain has
previously been demonstrated.17 Similar relations have been
found for longitudinal strain in acute18 as well as in chronic
ischemic heart disease.20 Global strain has been introduced as
an index of global LV function,29 but correlations with global
infarct mass have previously only been assessed for global
longitudinal strain.
In the present study, global longitudinal and circumferential strains both displayed excellent correlations with infarct
mass and ability to correctly classify the amount of MI mass.
Radial strain correlated less well with infarct mass. The
shortening deformation in systole normally occurs along the
longitudinal and circumferential axes. Systolic radial thickening, on the contrary, is because of a combination of
myocyte thickening and shearing forces of the oblique fiber
layers in the subendocardium.30
The feasibility of radial strain was low in the present
study. One explanation for this observation is the presence
of fewer speckles in the radial direction. The distance from
epicardium to endocardium along the radial direction is
approximately 1 cm, whereas the typical distance for a
segment along the circumferential and longitudinal directions are 2.5 and 3 cm, respectively. Therefore, more
speckles are found in circumferential and longitudinal
sample volumes compared with the radial. Moreover, there
is also a great transmural gradient of radial strain in the
normal myocardium.7 Longitudinal deformation is principally parallel to the beam direction, whereas circumferential and radial deformation takes place in a mixture of
directions relative to the beam direction.
Table 4.
Segmental Values
Segmental Values
Normal
Subendocardial
Transmural
Longitudinal strain
⫺18.4⫾4.1
⫺14.1⫾5.6*
⫺9.8⫾6.5*†
Circumferential strain
⫺22.1⫾6.4
⫺17.0⫾7.9*
⫺10.5⫾7.9*†
Radial strain
TDI SR
TDI Strain
31.8⫾19.4
24.7⫾19.7*
12.7⫾16.0*†
⫺1.3⫾0.4
⫺1.0⫾0.4*
⫺0.8⫾0.3*†
⫺17.6⫾4.7
⫺14.0⫾6.0*
⫺10.8⫾6.5*†
PSSI
4.1⫾6.6
14.2⫾19.7*
33.0⫾30.7*†
WMS
1.2⫾0.6
1.4⫾0.5*
1.9⫾0.7*†
Data are presented as mean⫾SD for echocardiographic deformation indices,
grouped by infarct transmurality. PSSI indicates postsystolic shortening index.
*P⬍0.05 versus normal.
†P⬍0.05 versus subendocardial MI.
194
Table 5.
Circ Cardiovasc Imaging
November 2008
Multivariate Correlations to Global Infarct Mass
Regression Coefficient (B)
SE
P
Longitudinal strain
3.51
1.19
0.005
Circumferential strain
2.96
0.86
0.001
2D-STE versus TDI
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The correlation to global infarct mass was better for global
longitudinal strain by 2D-STE than by TDI. This is in
accordance with the results of Cho et al.15 In their study,
segmental strain analyses by 2D-STE displayed superior
ability to differentiate normal and dysfunctional segments
when compared with strain by TDI. Strain analyses by
2D-STE is less angle dependent, and regional strain by
2D-STE is an average of strain from the whole segment.
Strain by TDI, on the contrary, is measured in smaller regions
of interest within the segment and is, thus, more prone to
variation.
In the present study, correlation with infarct mass was
similar for global SR and strain by 2D-STE, and the sensitivities and specificities for identification of MI where excellent by both methods. SR was not analyzed by 2D-STE in the
present study because the frame rate of 2D-STE is still not
sufficiently high for reliable SR-analyses.
SR by Doppler and strain by 2D-STE seems to be equally
good techniques for detecting MI in chronic ischemic heart
disease, but reliable deformation assessment by TDI is
generally limited to the longitudinal direction.
Infarct Size
The experienced cardiologist can easily identify large myocardial infarcts by visual analysis of echocardiograms, but
identification of small MI might be challenging. In the
present study, all global deformation indices were excellent
markers of large myocardial infarct. Identification of
medium-sized infarcts was superior for circumferential and
longitudinal strain by 2D-STE. Postsystolic shortening did
not provide additional information when compared with peak
systolic strain.
WMSI correlated to a lesser extent with myocardial infarct
mass and was unable to differentiate between the smallest
infarct sizes in the present study. Wall motion score has only
one level for description of segmental hypokinesia. Thus,
segmental hypokinesia includes a range of myocardial infarct
transmurality levels. Deformation analyses, on the contrary,
are performed along a continuous scale and display the
potential to better distinguish between the levels of dysfunction. This might explain why strain measurement is better to
identify the smallest infarcts.
Whereas LV twist is a good index of global LV systolic
deformation, LVEF reflects the relative LV volume reduction. Both indices are dependant on function in several
myocardial segments. Therefore, impairment of these indices
requires decreased function in several LV-segments, which
might not be present in patients with relatively limited
myocardial scar. In the present study, these indices were
unable to distinguish between small and medium-sized MI.
Ischemic injury is associated with a regional reduction in
myocardial contraction. Deformation assessment by strain or
SR measurements, therefore, has a theoretical advantage in
describing global LV function in ischemic heart disease.
Infarct Transmurality
Revascularization was in average performed 4 hours after
initiation of symptoms in the present study. This relatively
late reperfusion might explain the large infarcts with a central
transmural infarct surrounded by a zone of spared epicardium
(Figure 1).31 In the present study, all indices of segmental
myocardial function significantly separated among noninfarcted, subendocardial infracted, and transmural infarcted
segments. This is in accordance with previously published
results.9,17,18,20,32,33
Study Limitations
All indices of LV function are load dependent and should be
interpreted with care when there are changes in loading
conditions.10 However, we examined our patients in a stable
condition, verifying the clinical usefulness of the method
under this circumstance.
2D-STE measurements have the advantage of being relatively angle independent. It is, however, like all echocardiographic methods, dependent on image quality. Global strain is
the sum of strain values in all analyzed segments divided by
the number of analyzed segments. When the image quality
generally is low and many LV-segments are discarded, the
global strain value might be misjudged. In the present study,
all efforts were made to obtain high-quality images. Strain
values were obtained in 73% to 93% of the segments,
demonstrating that the 2D-STE technique is feasible in most
patients.
Myocardial deformation is a complex 3D process that is a
composite of regional elastic properties as well as intrinsic
and extrinsic forces. Echocardiographic deformation analyses do not, at the present time, provide information on
shear strains or transmural strain gradients, and this must
be considered when interpreting echocardiographic strain
measurements.
The frame rate of grayscale images is still not sufficiently
high for reliable SR analyses, longitudinal SR was therefore
analyzed by TDI.
In the present study, only 3 echocardiographic LV shortaxis slices were recorded, compared with 8 to 11 short-axis
slices by MRI. Comparison to infarct mass assessed from the
whole LV by MRI is therefore a difficult task and might
represent a problem when assessing the smallest myocardial
infarcts.
Conclusions
Global strain by 2D-STE assessed from circumferential and
longitudinal directions correlated well with global infarct
mass by CE-MRI and could separate among small, medium,
and large myocardial infarcts. Global longitudinal or circumferential strain adds incremental and accurate information
regarding myocardial infarct mass when compared with
LVEF or WMSI analyses. The present study demonstrates
that global strain has the potential to become a clinical
Gjesdal et al
Deformation Indices Correlate With Infarct Mass
bedside tool to quantify global function in regional LV
disease. There is a need for studies designed to evaluate the
deformation indices’ ability to predict prognosis in ischemic
heart diseases.
13.
Acknowledgments
14.
We appreciate the help from A.H. Pripp, MS, PhD, at the Department of Research Services, Biostatistics Unit, Rikshospitalet University Hospital.
15.
Sources of Funding
Drs Gjesdal, Helle-Valle, Lunde, and Vartdal are recipients of
research fellowships from the Norwegian Council on Cardiovascular
Diseases, Oslo, Norway.
16.
Disclosures
17.
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None.
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CLINICAL PERSPECTIVE
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Assessment of myocardial infarct mass and transmural distribution has prognostic and therapeutic implications.
Contrast-enhanced MRI is the gold standard for describing myocardial necrosis, but clinical application is limited by
availability, time factor, and cost. Deformation analysis by tissue Doppler imaging has been validated in the clinical setting,
but the method requires dedicated imaging procedures, and the postprocessing is time consuming. Speckle-tracking
echocardiography is based on conventional grayscale echocardiographic images and is therefore easily implemented in the
present clinical setting. Strain measurement by 2D speckle-tracking echocardiography provides information on regional
and global myocardial deformation and correlates well with infarct mass. There is reason to believe that reduced
contractility secondary to ischemic injury will affect prognosis, and this should be a topic for future investigations. The
present study demonstrates that identification of large myocardial infarcts was feasible by all the deformation indices.
Identification of smaller infarcts is a more difficult clinical task and was found superior by longitudinal and circumferential
strain measurements by 2D speckle-tracking echocardiography. The separation of small and medium-sized infarcts was not
possible by left ventricular ejection fraction or wall motion score index analyses. Longitudinal strain assessment was
feasible in more segments when compared with circumferential strain and is based on echocardiographic projections
already implemented in the daily routine at most hospitals.
Noninvasive Separation of Large, Medium, and Small Myocardial Infarcts in Survivors of
Reperfused ST-Elevation Myocardial Infarction: A Comprehensive Tissue Doppler and
Speckle-Tracking Echocardiography Study
Ola Gjesdal, Thomas Helle-Valle, Einar Hopp, Ketil Lunde, Trond Vartdal, Svend Aakhus,
Hans-Jørgen Smith, Halfdan Ihlen and Thor Edvardsen
Downloaded from http://circimaging.ahajournals.org/ by guest on May 12, 2017
Circ Cardiovasc Imaging. 2008;1:189-196
doi: 10.1161/CIRCIMAGING.108.784900
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1
Table displaying individual patients data:
Patient
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
Infarct Mass (g)
45.3
90.8
5.6
39.5
34.4
66.5
0.0
11.1
41.2
22.1
37.4
13.8
37.9
20.9
0.0
37.1
2.1
5.8
26.1
24.4
49.9
66.2
7.9
0.0
54.2
39.3
73.6
43.7
13.1
121.2
14.5
48.8
59.7
43.5
67.4
0.1
6.0
17.2
35.4
29.2
EDV (ml)
150
199
159
143
102
171
98
115
194
79
146
122
128
79
148
124
99
146
118
102
107
225
105
169
197
132
121
128
150
206
134
118
150
162
97
92
148
176
135
119
LVEF (%)
43
28
52
48
51
57
64
53
53
52
39
54
52
68
63
55
56
49
55
45
43
43
66
66
43
46
43
54
52
23
53
58
51
46
32
52
49
47
37
45
Legend: Table displays individual patient’s characteristics. EDV indicates end diastolic
volume, and LVEF; left ventricular ejection fraction.
2
Correlation matrix:
Infarct
Mass
Longitudinal strain
Circumferential strain
Radial strain
TDI SR
TDI Strain
PSSI
Twist
WMSI
LVEF
0.84
0.85
-0.69
0.82
0.80
0.83
-0.60
0.76
-0.71
Long
strain
0.84
-0.66
0.89
0.91
0.86
-0.50
0.78
-0.78
Circ
strain
-0.74
0.78
0.80
0.76
-0.52
0.81
-0.79
Radial
strain
-0.63
-0.63
-0.65
0.43
-0.75
0.66
TDI SR
0.85
0.77
-0.42
0.75
-0.79
TDI
Strain
0.83
-0.46
0.74
-0.77
PSSI
-0.50
0.79
-0.80
Twist
-0.47
0.46
Legend: Table displays matix of correlation coefficients (r) between global deformation
indices and infarct mass. TDI indicates tissue Doppler imaging, SR; strain rate, PSSI; post
systolic index, WMSI; wall motion score index and LVEF; left ventricular ejection fraction.
WMSI
-0.74