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Interpretation of two-dimensional and tissue Doppler-derived strain (ε) and strain rate data: Is there a need to normalize for individual variability in left ventricular morphology?

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This study examined the relationships between myocardial strain (epsilon) and strain rate (SR) data, derived from both two-dimensional (2D) speckle tracking and tissue Doppler imaging (TDI), and indices of left ventricular (LV) morphology to assess size-(in)dependence of these functional parameters. 2D speckle tracking and TDI echocardiograms were performed in 79 healthy adult male volunteers (age range: 22-76 years). 2D speckle tracking allowed the determination of myocardial epsilon and peak systolic and early diastolic SR in radial, circumferential, and longitudinal planes, whereas TDI provided longitudinal epsilon only. Mean circumferential and radial epsilon and SR were calculated from data collected at six basal myocardial regions, whereas mean longitudinal epsilon and SR derived from both 2D speckle tracking and TDI were calculated from the basal septum and basal lateral walls. Standard 2D echocardiography allowed the assessment of LV morphology including LV length, LV end-diastolic volume, LV end-diastolic diameter, mean wall thickness, and LV mass. The association of myocardial epsilon and SR data with relevant LV morphology indices was determined by adoption of the general, non-linear allometric model (y= ax(b)). The b exponent +/- 95% confidence intervals were reported. The relationships between the measures of LV morphology and myocardial epsilon and SR were highly variable and generally weak. Only two relationships displayed at least a moderate effect size (r > or = 0.30): (i) 2D circumferential peak systolic SR and LV end-diastolic dimension (b = -0.92; -1.35 to 0.5, r = 0.44) and (ii) TDI longitudinal peak systolic SR and LV length (b = -1.39; -2.11 to -0.66, r = 0.41). The empirical relationships derived in this cohort do not support the need to scale myocardial epsilon and SR derived from 2D speckle or TDI for any index of LV morphology.
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Interpretation of two-dimensional and tissue
Doppler-derived strain (
1
) and strain rate data: is
there a need to normalize for individual variability
in left ventricular morphology?
David Oxborough1*, Alan M. Batterham2, Rob Shave3, Nigel Artis1, Karen M. Birch4, Greg Whyte5,
Philip N. Ainslie6, and Keith P. George5
1
Faculty of Medicine and Health, School of Healthcare, University of Leeds, Leeds LS2 9UT, UK;
2
Health and Social Care
Institute, University of Teesside, Middlesbrough, UK;
3
Centre for Sport Medicine and Human Performance, Brunel University,
Uxbridge, London, UK;
4
Faculty of Biological Sciences, University of Leeds, Leeds, UK;
5
Research Institute for Sport and
Exercise Sciences, Liverpool John Moores University, Liverpool, UK; and
6
Department of Physiology, University of Otago,
Dunedin, New Zealand
Received 15 January 2009; accepted after revision 22 March 2009; online publish-ahead-of-print 9 April 2009
Aims This study examined the relationships between myocardial strain (1) and strain rate (SR) data,
derived from both two-dimensional (2D) speckle tracking and tissue Doppler imaging (TDI), and
indices of left ventricular (LV) morphology to assess size-(in)dependence of these functional par-
ameters.
Methods and results 2D speckle tracking and TDI echocardiograms were performed in 79 healthy adult
male volunteers (age range: 22
76 years). 2D speckle tracking allowed the determination of myocardial
1and peak systolic and early diastolic SR in radial, circumferential, and longitudinal planes, whereas TDI
provided longitudinal 1only. Mean circumferential and radial 1and SR were calculated from data col-
lected at six basal myocardial regions, whereas mean longitudinal 1and SR derived from both 2D speckle
tracking and TDI were calculated from the basal septum and basal lateral walls. Standard 2D echocar-
diography allowed the assessment of LV morphology including LV length, LV end-diastolic volume, LV end-
diastolic diameter, mean wall thickness, and LV mass. The association of myocardial 1and SR data with
relevant LV morphology indices was determined by adoption of the general, non-linear allometric model
(y¼ax
b
). The bexponent +95% confidence intervals were reported. The relationships between the
measures of LV morphology and myocardial 1and SR were highly variable and generally weak. Only
two relationships displayed at least a moderate effect size (r0.30): (i) 2D circumferential peak sys-
tolic SR and LV end-diastolic dimension (b¼20.92; 21.35 to 0.5, r¼0.44) and (ii) TDI longitudinal
peak systolic SR and LV length (b¼21.39; 22.11 to 20.66, r¼0.41).
Conclusion The empirical relationships derived in this cohort do not support the need to scale myocar-
dial 1and SR derived from 2D speckle or TDI for any index of LV morphology.
KEYWORDS
Speckle tracking;
Tissue Doppler;
Left ventricle;
Scaling;
Allometry
Introduction
The recent development of strain (1) and strain rate (SR)
echocardiographic measurements has the potential to
provide valuable and discriminating indices of regional and
global ventricular function.
1
A significant benefit afforded
by 1and SR is that they do not suffer from ‘tethering’ and
translational artefact and it is also believed that SR data
in normal human ventricles are less load-dependent than
other regional or global indices of ventricular function.
2,3
Myocardial 1is a measurement of actual deformation of a
specific region of tissue, whereas SR is simply the rate of
that deformation. During ventricular contraction and relax-
ation, deformation occurs in three planes (radial, circumfer-
ential, and longitudinal), as well as producing rotation. The
initial development of 1and SR measurements utilized a
tissue Doppler data set.
4,5
However, 1derived from tissue
Doppler is constrained by the angle dependency of Doppler
*Corresponding author. Tel: þ44 1133437962, Fax: þ44 1133431204.
E-mail address: d.oxborough@leeds.ac.uk
Published on behalf of the European Society of Cardiology. All rights reserved. &The Author 2009.
For permissions please email: journals.permissions@oxfordjournals.org.
European Journal of Echocardiography (2009) 10, 677
682
doi:10.1093/ejechocard/jep037
at Edward Boyle Library on October 16, 2010ejechocard.oxfordjournals.orgDownloaded from
imaging and thus limited to longitudinal and radial measure-
ments. Myocardial or two-dimensional (2D) speckle tracking
is a new ultrasound technique that can be used to calculate
myocardial Lagrangian 1and SR. 2D speckle tracking does
not rely on Doppler imaging, and hence, 1and SR can be
measured throughout the circumferential, radial, and longi-
tudinal planes.
6
1
and SR derived from 2D speckle tracking
have recently been documented as feasible
7
and validated
against tagged magnetic resonance imaging
8
and sonomicro-
metry both in vitro and in vivo
6,9
with the further benefit of
automated segment tracking.
9
As with any index of ventricular function, there is concern
as to how they are influenced by gross cardiac morphology.
Another recently developed measure of regional ventricular
function, tissue Doppler myocardial velocities, has been
suggest to be dependent upon ventricular dimension,
10
left
ventricular (LV) length,
11
or ventricular volume and
mass.
12
Whether 1and SR measurements are independent
of ventricular size is not currently known. Furthermore,
whether 1and SR derived from tissue Doppler or 2D
speckle tracking are similarly (un)related to LV morphology
is also not known. Therefore, the aim of this study was to
quantify the nature of the relationships between the
measures of myocardial 1and peak systolic and early dias-
tolic SR, from multiple planes of movement as well as
through both 2D speckle tracking and tissue Doppler
imaging (TDI), with a range of indices of ventricular mor-
phology. The need to consider allometric scaling of cardiac
functional parameters is clear
13,14
as this may serve to
provide precise interpretation of 1and SR data in clinical
and non-clinical studies.
Methods
Subjects
Seventy-nine healthy adult males with a broad age range [mean +
SD, age (range) ¼41 +16 (22
76) years] volunteered and were con-
secutively enrolled in the study, subject details are provided in
Table 1. All subjects were healthy and free from known cardiovascu-
lar disease, any early family history of cardiovascular disease, and
were not currently taking any form of prescribed medication. All
subjects provided written informed consent to participate and
the study was granted ethics approval by the Ethics Committee of
Liverpool John Moores University.
Procedures
After a full explanation of procedures, subjects lay supine, and after
a 5 min resting period, duplicate brachial artery systolic and dias-
tolic blood pressures were assessed by standard auscultation. At
the end of this period, resting heart rate was recorded.
All echocardiographic images were acquired using a commercially
available ultrasound system (Vivid 7, GE Medical, Horton, Norway)
with a 1.5
4 MHz phased array transducer. All images were acquired
by a single experienced sonographer with the subject lying in the
left lateral decubitas position and recorded to DVD in a raw
DICOM format. Acquisition and analysis were performed by the
same single experienced sonographer.
Two-dimensional myocardial speckle
tracking-derived
1
and strain rate
Radial and circumferential 1and SR data were derived from a para-
sternal short-axis view at the basal level. The focal point was posi-
tioned close to the centre of the LV cavity to provide optimum beam
width, while reducing the effects of divergence. Longitudinal 1and
SR data were obtained from an apical four-chamber view only. The
focal point was positioned at the level of the mitral valve. In both
orientations, frame rates were maximized with acceptable levels
of .40 and ,90 fps. All images were optimized with gain, com-
pression, and dynamic range to enhance myocardial definition.
Analysis of the 2D images was performed offline using commer-
cially available software (2D strain, EchoPac, GE Medical). Three
cardiac cycles were utilized and an average of each parameter
was used for analysis. A region of interest (ROI) was allocated to
the whole of the LV in both of the views ensuring alignment with
the endo- and epicardium. (Figures 1 and 2). Myocardial defor-
mation was determined from continuous frame-by-frame tracking
of the ‘natural acoustic markers’,
6
and 1and SR were calculated
from the displacement and rate of displacement.
15
The analysis
software includes increased averaging capabilities that improve
signal-to-noise ratio
16
as well as automatic grading of the tracking
quality as either acceptable (V) or unacceptable (X). All basal seg-
ments were considered acceptable, whereas a proportion of longi-
tudinal mid- and apical segments were considered unacceptable;
hence, only basal segments were included in the analysis. Mean cir-
cumferential and radial 1, systolic SR, and early diastolic SR were
calculated by the software for each of the basal inferoseptum,
basal anteroseptum, basal anterior, basal lateral, basal posterior,
and basal inferior wall segments and a mean value of all six seg-
ments was used in the analysis. Mean longitudinal 1, systolic SR,
and early diastolic SR were calculated for the basal septum and
basal lateral walls to match the level of the radial and circumferen-
tial data and the mean of both segments was used in the analysis.
Data were collected from a separate subgroup on 20 subjects from
two separate acquisitions, 2 days apart which revealed a coefficient
of variation (%CV) for radial, circumferential, and longitudinal 1of
6.7%, 5%, and 5.5%, respectively. Peak systolic SR %CV were 3.5%,
Table 1 Descriptive data for the cohort
Variable Mean +SD (range)
Age (years) 41 +16 (22
76)
Body mass (kg) 75 +10 (54
100)
Height (m) 1.77 +0.08 (1.50
1.96)
Systolic blood pressure (mmHg) 119 +12 (90
132)
Diastolic blood pressure (mmHg) 71 +11 (48
80)
Resting heart rate (bpm) 59 +9 (39
93) Figure 1 Two-dimensional parasternal short-axis view at the basal
level with region of interest encompassing endo- and epicardium for
two-dimensional strain (1) and strain rate analysis.
D. Oxborough et al.678
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5%, and 8.2% and peak early diastolic SR of 3.7%, 5.1%, and 7.3% for
radial, circumferential, and longitudinal planes.
Tissue Doppler-derived
1
and strain rate
The apical four-chamber view was used to obtain longitudinal 1, sys-
tolic SR, and early diastolic SR data from the basal septum and
lateral walls. The myocardial wall was aligned with the ultrasound
beam and a narrow sector was utilized to obtain frame rates in
excess of 200 fps. A colour tissue Doppler ROI was superimposed
on the segment, whereas gain, filter, pulse repetition frequency,
and depth were adjusted to optimize colour saturation and elimin-
ate aliasing (Figure 3).
All tissue Doppler images were analysed offline using the same
software package and over an average of three cardiac cycles.
A large sample size of 24 mm 9 mm was used to maximize repro-
ducibility and to allow full capture of the basal segment, while
ensuring similar segment size to that used during speckle tracking
analysis. The sample was anchored to the myocardium and adjusted
throughout the cardiac cycle to ensure consistency of its basal pos-
ition. The mean value of both segments of 1, systolic SR, and dias-
tolic SR was reported.
Conventional echocardiography
Conventional echocardiographic parameters were obtained from
parasternal and apical acoustic windows. All settings were
optimized to obtain maximum signal-to-noise ratio and provide
optimal endocardial delineation. Left ventricular end-diastolic
dimension (LVd), mean LV wall thickness, LV length, LV end-diastolic
volume (EDV), and LV mass were measured in accordance with rec-
ommendations from the American Society of Echocardiography.
17
Data analysis and statistics
Allometric scaling of the general form y¼ax
b
was used to analyse
the relationship between (i) indices of longitudinal 1and LV
length, EDV, and LV mass and (ii) indices of both circumferential
and radial 1and LVd, mean LV wall thickness, and LV mass. All allo-
metric regression model parameters were solved by working in the
arithmetic space defined by the original, raw Xand Yvariables
using an iterative, non-linear protocol (Levenberg
Marquardt algor-
ithm).
18
In this procedure, small successive corrections to par-
ameter estimates are made until a global solution converges. Size
exponents (b) together with their 95% confidence intervals (CIs)
were calculated and presented along with the non-linear correlation
coefficient for the model. We define the smallest worthwhile effect
for the allometric relationships as a correlation coefficient of r¼
0.30; a moderate effect size in Cohen’s terms.
19
Finally, we com-
pared, by repeated measures ANOVA and Pearson’s correlation,
longitudinal 1and SR derived from 2D and tissue Doppler. Analyses
were conducted using SPSS statistical software (SPSS v. 15.0, SPSS
Inc., Chicago, IL, USA).
Results
LV morphology parameters are presented in Table 2. The
broad range of LV morphology data befits the age heterogen-
eity of the study cohort. Descriptive cohort data for 2D and
TDI
1
as well as peak systolic SR and early diastolic SR are
contained in Table 3. Subtle differences between LV wall
segments were apparent for both 1and SR data and, inter-
estingly, 2D longitudinal 1and SR data are significantly and
substantially lower than similar data derived from TDI. The
correlation coefficients for TDI and 2D longitudinal 1, systo-
lic SR, and diastolic SR were small and not significant at 0.05
(P¼0.7), 0.20 (P¼0.07), and 0.06 (P¼0.58), respectively.
Data for bexponents and their 95% CIs are presented in
Tables 4 and 5. A range of positive and negative bexponents
(0.33 to 21.39) are presented with generally very broad CI
and small non-linear correlation coefficients for the model.
This suggests weak and unstable relationships between 1and
SR and estimates of LV morphology for both 2D- and TDI-
derived data. An exemplar scatterplot is provided in
Figure 4, showing the relationship between peak radial
Figure 3 Colour tissue Doppler imaging acquisition of the interven-
tricular septum.
Figure 2 Two-dimensional apical four-chamber view of the left
ventricle with region of interest encompassing endo- and epicar-
dium for two-dimensional 1and strain rate analysis.
Table 2 Left ventricular structural and functional data derived
by standard echocardiography
Variable Mean +SD (range)
LV end-diastolic dimension (cm) 5.1 +5.0 (4.1
6.4)
Posterior wall thickness (cm) 1.0 +0.1 (0.7
1.3)
Septal wall thickness (cm) 1.1 +0.2 (0.8
1.8)
Mean LV wall thickness (cm) 1.0 +0.1 (0.7
1.4)
Left ventricular mass (g) 209 +47 (122
397)
Left ventricular length at
end-diastole (cm)
9.1 +0.7 (7.8
10.9)
Left ventricular end-diastolic volume
(mL)
123 +29 (71
217)
Ejection fraction (%) 66 +6 (52
78)
Relationship between myocardial 1and SR with LV morphology 679
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systolic SR and LVd, which highlights the general nature of
the relationship between 1and SR data with LV morphology.
In all, there were non-significant and non-substantial b
exponents in 23 of the 36 relationships assessed, suggesting
that these outcome variables are effectively size-
independent. Of the statistically significant exponents, the
majority were not substantial (Tables 4 and 5) with small
non-linear correlation coefficients for the model. Indeed,
only two allometric relationships exceeded the threshold
of r¼0.30 defining a moderate effect size;
19
(i) peak
circumferential systolic SR and LVd had a bexponent of
20.92 (21.35 to 20.50) with a correlation coefficient of
0.44, and (ii) peak longitudinal systolic SR, derived from
TDI, and LV length had a bexponent of 21.39 (22.11 to
20.66) with a correlation coefficient of 0.41.
Discussion
There is growing evidence to support the use of ultrasound-
derived myocardial 1and SR in the assessment of LV func-
tion.
20
26
This technique allows the assessment of regional
systolic and diastolic function and overcomes some of the
limitations of conventional indices.
1,3,27
In developing the
clinical application of myocardial 1and SR, it is important
that the relationship between LV morphology and 1par-
ameters is established. Such empirical data could facilitate
the production of size-independent 1data and thus aid accu-
rate clinical interpretation. This study, uniquely, provides
allometrically derived relationships for both TDI- and 2D
speckle tracking-derived 1and SR and their associations
with LV morphology. Most relationships were non-significant,
unlike annular myocardial velocities derived from tissue
Doppler, which have recently been shown to require
Table 3 Descriptive cohort data for two-dimensional and tissue
Doppler-derived strain (
1
) and strain rate data
Variable Mean +SD (range)
2D radial
Peak 149 +15 (20
86)
Peak S SR 1.68 +0.50 (0.81
3.34)
Peak E SR 1.86 +0.68 (0.72
4.01)
2D circumferential
Peak 119.4 +3.6 (11.2
29.6)
Peak S SR 1.30 +0.27 (0.82
2.06)
Peak E SR 1.86 +0.50 (0.91
3.87)
2D longitudinal
Peak 117.0 +2.8 (9.1
22.4)
Peak S SR 0.99 +0.21 (0.69
1.53)
Peak E SR 1.24 +0.35 (0.65
2.12)
TDI longitudinal
Peak 120.0 +3.2 (13.6
27.9)*
Peak S SR 1.20 +0.26 (0.75
1.81)*
Peak E SR 1.82 +0.48 (0.30
3.04)*
S, systole; E, early diastole; TDI, tissue Doppler imaging.
*Significance when compared with equivalent parameters obtained
from 2D longitudinal strain—P,0.001.
Table 5 Longitudinal two-dimensional
1
and tissue Doppler imaging 1,bexponents (+95% confidence limits) for the relationships 1and
strain rate data and left ventricular morphology
Variable LV mass LV length LV end-diastolic volume
2D longitudinal
Peak 120.14 (20.32 to 0.29) 0.08 (0.17
0.14) 0.29 (0.01
0.58)
Peak S SR 20.25 (20.47 to 20.03) 0.05 (0
0.10) 20.05 (20.27 to 0.16)
Peak E SR 20.10 (20.42 to 0.21) 0.10 (0.39
0.16) 0.40 (0.12
0.69)
TDI longitudinal
Peak 120.14 (20.19 to 0.16) 20.49 (21.07
0.09) 20.19 (20.35 to 20.03)
Peak S SR 0.05 (20.19 to 0.29) 21.39 (22.11 to 20.66),
a
r¼0.41 20.32 (20.53 to 20.12)
Peak E SR 0.13 (20.15 to 0.40) 20.52 (21.43 to 0.40) 20.09 (20.35 to 0.18)
a
Non-linear correlation coefficients shown for moderate effect sizes.
Table 4 Radial and circumferential two-dimensional 1,bexponents (+95% confidence limits) for the relationships 1and strain rate data
and left ventricular morphology
Variable LV mass Mean LV wall thickness LV end-diastolic dimension
2D radial
Peak 120.27 (20.57 to 0.03) 20.28 (20.79 to 0.23) 20.37 (21.10 to 0.33)
Peak S SR 20.33 (20.62 to 20.04) 20.31 (20.81 to 0.20) 20.53 (21.22 to 0.17)
Peak E SR 20.26 (20.64 to 0.13) 0.17 (20.49 to 0.83) 21.05 (21.91 to 20.19)
2D circumferential
Peak 10.07 (20.12 to 0.26) 0.33 (0.02
0.64) 20.28 (20.71 to 0.16)
Peak S SR 20.22 (20.42 to 20.02) 0.14 (20.21 to 0.49) 20.92 (21.35 to 20.50),
a
r¼0.44
Peak E SR 20.13 (20.41 to 0.15) 0.04 (20.43 to 0.51) 20.43 (21.07 to 0.21)
a
Non-linear correlation coefficients shown for moderate effect sizes.
D. Oxborough et al.680
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scaling for LV length in healthy humans,
11
and 1parameters
appear to be independent of a range of LV morphology
measures.
No previous studies have assessed the strain
LV mor-
phology relationship in human populations. Numerous
studies have, however, documented changes in 1and SR
under various loading conditions using both TDI
28
31
and
from 2D
32
-derived strain. The evidence is contradictory
but 1parameters generally appear much more stable
under different loading conditions when compared with
myocardial velocities.
2,33
Longitudinal SR also appears less
load-dependent than longitudinal 1.
27,28,30
Conversely, a
recent 2D study demonstrated significant changes to radial
and circumferential 1and SR immediately after aortic
valve replacement.
31
In view of the equivocal nature of
the relationship between LV loading and myocardial 1in
past research, this study contributes to the developing
knowledge base and provides some support that 1and SR
derived from both TDI and 2D are size-independent.
There were some statistically significant, moderate corre-
lations noted, for example, 2D circumferential systolic SR
and LV diameter and TDI longitudinal systolic SR and LV
length. Based on the sporadic and limited number of such
relationships, it is possible that these are artefacts based
on the large number of relationships assessed. Certainly on
their own, these isolated findings do not provide substantial
evidence that there is a real need to scale these data. It
does, however, prompt the development of this scaling
approach in different cohorts.
The values of longitudinal 1, systolic SR, and early dias-
tolic SR obtained from TDI and 2D speckle tracking method-
ology are weakly correlated and significantly different with
higher values obtained from TDI (Table 3). This is not con-
sistent with previous findings
15,34,35
where similar values
have been presented. The sample size used for TDI analysis
in this study was large at 24 9 mm in order to cover a
similar region allocated by the software for 2D 1. This
differs from past research where a smaller sample volume
has been used and this may partially explain the current
data with a larger sample volume potentially capable of
capturing regions of the myocardium with higher tissue
velocities. We did adopt published, practical guidance for
analysis of TDI-derived 1,
1
with the recommendation to
ensure that the sample volume was positioned centrally
within the mid-layer. Future study may want to determine
the impact of sample volume size alterations on TDI-derived
1and SR. By the nature of the technique, the ROI for 2D
analysis was slightly different for each subject with the
aim to include both the epi- and endocardium. With a
general variation in wall thicknesses, it is clear that the
sample volume used in TDI-derived 1was not always com-
parable to that used in 2D and this may also contribute to
the consistently lower values obtained by 2D
1
. Further com-
parative work is required to assess the required method-
ology to ensure that these values can be used
interchangeably.
This current data set also acts as a relatively large set of
normative (male, adult, healthy) data across modalities.
There is currently limited evidence to provide adequate
normal ranges and therefore this work further contributes
to this area.
Delimitations
A priori, we constrained statistical analysis to the mean
values of LV basal segments only. Furthermore, longitudinal
1values for both 2D and TDI-derived 1were calculated as a
mean of only two of the six basal segments. Although this
does provide a limited assessment of the 3D nature of the
LV, this methodology was used to ensure standardization
across planes and between TDI- and 2D-derived values.
Also previous work using TDI-derived longitudinal 1has
demonstrated homogenous distribution from base to
apex.
36
This does require further validation and therefore
there is potential benefit from including additional segments
and regional information in subsequent work.
2D speckle-derived 1can also provide velocity, displace-
ment, and rotation/torsion data.
37
There is a lack of
normal data and understanding of their relationship to LV
morphology. Further work would benefit from providing a
statistical analysis of this data particularly in view of their
potential for clinical and physiological application.
This study utilizes male subjects only and would probably
benefit from including females. This would provide a more
inclusive normal range, yet it is extremely unlikely that
gender would have any impact on the scaling relationships
assessed in this study.
Conclusion
Irrespective of the difference and poor correlation between
TDI- and 2D-derived 1and SR data, it is clear that 1values
obtained from LVs of different size and wall thicknesses do
not require normalizing or indexing. Clinical management
based on these parameters should continue with adherence
to local and national guidelines. When using both method-
ologies interchangeably for obtaining 1and SR data, it is
important to be aware of sample size and position with
reference to the underlying myocardium.
Acknowledgements
We are grateful to our subjects and all those at Cardiac Risk in the
Young who helped facilitate this work. We also thank Professor Tim
Noakes at the Research Unit for Exercise Science and Sports Medi-
cine at the University of Cape Town, South Africa, for their assist-
ance and collaboration in data collection. We thank GE Ltd for
providing technical assistance.
Conflict of interest: none declared.
Figure 4 Exemplar scatterplot demonstrating the relationship
between mean systolic radial strain rate and left ventricular dias-
tolic dimension.
Relationship between myocardial 1and SR with LV morphology 681
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at Edward Boyle Library on October 16, 2010ejechocard.oxfordjournals.orgDownloaded from
... Cardiac indices were normalised for body surface area, height and end-diastolic left ventricle long or short axis lengths, as appropriate. [18][19][20] Tissue Doppler imaging (TDI), strain and strain rate indices are given as absolute values. ...
... All of the conventional echocardiographic indices were adjusted for body surface area 17 and all of the tissue Doppler velocity and deformation indices to the end-diastolic left or right ventricle long-axis length. 18 Prespecified subgroup analyses were carried out for co-primary outcomes in view of the changes to definitions of systolic and diastolic dysfunction over the study period. Data analyses were carried out with Stata/SE version 15.1. ...
Article
Background Women whose pregnancies are affected by hypertensive disorders of pregnancy, in particular preterm pre-eclampsia, are at increased risk of long-term cardiovascular morbidity and mortality. Objectives To investigate the hypothesis that prolongation of a pregnancy affected by preterm pre-eclampsia managed by expectant management compared with planned early delivery would result in worse cardiovascular function 6 months postpartum. Design A randomised controlled trial. Setting 28 maternity hospitals in England and Wales. Participants Women who were eligible for the Pre-eclampsia in HOspital: Early iNductIon or eXpectant management (PHOENIX) study were approached and recruited for the PHOEBE study. The PHOENIX (Pre-eclampsia in HOspital: Early iNductIon or eXpectant management) study was a parallel-group, non-masked, multicentre, randomised controlled trial that was carried out in 46 maternity units across England and Wales. This study compared planned early delivery with expectant management (usual care) with individual randomisation in women with late preterm pre-eclampsia who were 34 weeks’ gestation to less than 37 weeks’ gestation and having a singleton or dichorionic diamniotic twin pregnancy. Interventions Postpartum follow-up included medical history, blood pressure assessment and echocardiography. All women had blood sampling performed on at least two time points from recruitment to the 6-month follow-up for assessment of cardiac necrosis markers. Main outcome measures Primary outcome was a composite of systolic and/or diastolic dysfunction (originally by 2009 guidelines then updated by 2016 guidelines, with an amended definition of diastolic dysfunction). Analyses were by intention to treat, together with a per-protocol analysis for the primary and secondary outcomes. Results Between 27 April 2016 and 30 November 2018, 623 women were found to be eligible, of whom 420 (67%) were recruited across 28 maternity units in England and Wales. A total of 133 women were allocated to planned delivery, 137 women were allocated to expectant management and a further 150 received non-randomised expectant management within usual care. The mean time from enrolment to delivery was 2.5 (standard deviation 1.9) days in the planned delivery group compared with 6.8 (standard deviation 5.3) days in the expectant management group. There were no differences in the primary outcome between women in the planned delivery group and those in the expectant management group using either the 2009 (risk ratio 1.06, 95% confidence interval 0.80 to 1.40) or the 2016 definition (risk ratio 0.78, 95% confidence interval 0.33 to 1.86). Overall, 10% (31/321) of women had a left ventricular ejection fraction < 55% and 71% of the cohort remained hypertensive at 6 months postpartum. No differences were observed between groups in cardiorespiratory outcomes prior to discharge from hospital or in systolic or diastolic blood pressure measurements. Variables associated with the primary outcome (2009 definition) at 6 months postpartum were maternal body mass index (adjusted odds ratio 1.33 per 5 kg/m ² , 95% confidence interval 1.12 to 1.59 per 5 kg/m ² ) and maternal age (adjusted odds ratio 2.16, 95% confidence interval 1.44 to 3.22 per 10 years). Limitations include changing definitions regarding systolic and/or diastolic dysfunction. Conclusions Preterm pre-eclampsia results in persistence of hypertension in the majority of women with late preterm pre-eclampsia at 6 months postpartum and systolic dysfunction in 10%. Pre-eclampsia should not be considered a self-limiting disease of pregnancy alone. Future work Interventions aimed at reducing cardiovascular dysfunction. Trial registration Current Controlled Trials ISRCTN01879376. Funding This project was funded by the Efficacy and Mechanism Evaluation (EME) programme, a Medical Research Council and National Institute for Health Research (NIHR) partnership. This will be published in full in Efficacy and Mechanism Evaluation ; Vol. 8, No. 12. See the NIHR Journals Library website for further project information.
... Cardiac indices were normalized for body surface area, height, and end-diastolic left ventricle (LV) long or short axis lengths, as appropriate. [15][16][17] Tissue Doppler imaging, strain, and strain rate indices are given as absolute values. ...
... All of the conventional echocardiographic indices were adjusted for body surface area 14 and all of the tissue Doppler velocity and deformation indices to the enddiastolic left or right ventricle long axis length. 15 Prespecified subgroup analyses were performed for co-primary outcomes in view of changes to definitions of systolic and diastolic dysfunction over the study period. Data analyses and power calculations were performed using STATA/SE version 15.1. ...
Article
This study evaluated whether planned early delivery would ameliorate cardiovascular dysfunction 6 months postpartum, compared with usual care with expectant management, in women with late preterm preeclampsia. We conducted a mechanistic observational study in women with preterm preeclampsia between 34 ⁺⁰ and 36 ⁺⁶ weeks’ gestation, nested within a randomized controlled trial of planned early delivery versus expectant management (usual care), in 28 maternity hospitals in England and Wales. Women were followed up 6 months postpartum with cardiovascular assessments. The primary outcome was a composite of systolic and diastolic dysfunction (by 2009 and 2016 definitions of diastolic dysfunction). Between April 27, 2016, and November 30, 2018, 623 women were found to be eligible, of whom 420 (67%) were recruited. One hundred thirty-three women were randomized to planned delivery, 137 women were randomized to expectant management within the trial, while 150 women received expectant management outside of the trial. 321 (76.4%) completed their 6 month echocardiography assessment. 10% (31/321) had a left ventricular ejection fraction <55% while 71% (229/321) remained hypertensive. There were no differences in the primary outcome between the 2 randomized groups (planned delivery versus expectant management) using either the 2009 (risk ratio, 1.06 [95% CI, 0.80–1.40]) or 2016 definitions (risk ratio, 0.78 [0.33–1.86]). In conclusion, we demonstrated that late preterm preeclampsia results in persistence of hypertension in the majority and systolic LV dysfunction in 10%, of women 6 months postpartum. Planned early delivery does not affect these outcomes. Preeclampsia is not a self-limiting disease of pregnancy alone.
... Nova speckle tracking tehnika (praćenja markiranih tačkica) je dvodimenzionalna i omogućuje merenja u cirkumferencijalnoj, radijalnoj i longitudinalnoj ravni. 13,14 Primena strain ehokardiografije u evaluaciji hipertenzivnih pacijenata omogućuje napredak u ranoj identifikaciji funkcionalnih abnormalnosti koje se ne mogu detektovati konvencionalnim metodama. 15,16 Redukovani maksimalni strain u pojedinim segmentima miokarda sugeriše da je redukovana deformacija leve komore kao posledica strukturnih promena i ima uticaj na globalnu Uvod: Segmentna dijastolna i sistolna disfunkcija leve komore, uzrokovane hipertenzijom i mogu se pravovremeno dijagnostikovati strain rate imaging ehokardiografijom. ...
... Nova speckle tracking tehnika (praćenja markiranih tačkica) je dvodimenzionalna i omogućuje merenja u cirkumferencijalnoj, radijalnoj i longitudinalnoj ravni. 13,14 Primena strain ehokardiografije u evaluaciji hipertenzivnih pacijenata omogućuje napredak u ranoj identifikaciji funkcionalnih abnormalnosti koje se ne mogu detektovati konvencionalnim metodama. 15,16 Redukovani maksimalni strain u pojedinim segmentima miokarda sugeriše da je redukovana deformacija leve komore kao posledica strukturnih promena i ima uticaj na globalnu ...
... What is measured with strain by echo is a substitute for this complex deformation [8,9]. Despite Doppler tissue imaging (DTI), 2DSTE is not influenced by noises or adjacent segment tethering and is also not angle-dependent [10][11][12][13]. ...
Article
Full-text available
Background Coronary artery disease (CAD) is one of the most prevalent diseases around the world; however, finding the best noninvasive, low-cost, and more easily accessible test for its screening has been a challenge for several years. Eighty-nine patients suspected of stable CAD underwent 2D-speckle-tracking echocardiography (2DSTE) at resting position and offline longitudinal myocardial strain analysis, followed by coronary angiography. The correlation of the global longitudinal strain (GLS) and territorial longitudinal strain (TLS) with significant CAD (70% and more stenosis in at least one coronary artery) was then evaluated. Results The statistical analysis showed a significant correlation between low GLS and significant CAD (P=0.0001). The results also showed a significant correlation between low TLS and significant CAD in the left and right coronary artery territories. The optimal cut-off point of GLS for the detection of significant CAD was −19.25, with a sensitivity of 76.5% and specificity of 76.6%. Conclusion This study confirmed the usefulness of 2DSTE myocardial strain analysis in diagnosis of CAD for detecting the affected coronary arteries using GLS and SLS.
... The same abnormal manifestation was observed in this study in T2DM patients. Previous studies have suggested that myocardial interstitial fibrosis and cardiac activity characteristics are closely related to longitudinal strain, which is an important pathophysiological basis of LV remodeling 32,33 Considering a previous finding that longitudinal PS is better than LVEF for predicting cardiac events 34 , we can assume that the early detection of myocardial strain is of great significance to the clinical prognosis of T2DM patients. ROC curve analysis demonstrated that the performance of global radial, circumferential, and longitudinal PS in detecting T2DM was moderate. ...
Article
Full-text available
To quantify the global and regional left ventricular (LV) myocardial strain in type 2 diabetes mellitus (T2DM) patients using cardiac magnetic resonance (CMR) tissue-tracking techniques and to determine the ability of myocardial strain parameters to assessment the LV deformation. Our study included 98 adult T2DM patients (preserved LV ejection fraction [LVEF], 72; reduced LVEF, 26) and 35 healthy controls. Conventional LV function, volume-time curve parameters and LV remodeling index were measured using CMR. Global and regional LV myocardial strain parameters were measured using CMR tissue tracking and compared between the different sub-groups. Receiver operating characteristic analysis was used to assess the diagnostic accuracy. Regression analyses were conducted to determine the relationship between strain parameters and the LV remodeling index. The results show that global radial peak strain (PS) and circumferential PS were not significantly different between the preserved-LVEF group and control group (P > 0.05). However, longitudinal PS was significantly lower in the preserved-LVEF group than in the control group (P = 0.005). Multivariate linear and logistic regression analyses showed that global longitudinal PS was independently associated (β = 0.385, P < 0.001) with the LV remodeling index. In conclusion, early quantitative evaluation of cardiac deformation can be successfully performed using CMR tissue tracking in T2DM patients. In addition, global longitudinal PS can complement LVEF in the assessment of cardiac function.
Chapter
Regular intensive exercise leads to a series of electrical, structural, and functional changes in the heart, collectively named as the “athlete’s heart”. Sporting discipline has an impact on cardiac adaptation to exercise. Endurance athletes tend to exhibit a significant biventricular enlargement and highly trained cyclists can be characterized by a low normal or even reduced left ventricular ejection fraction at echocardiography. Normal left ventricular geometry prevails in most highly trained athletes; however, while female athletes engaged in dynamic exercise show a greater prevalence of eccentric hypertrophy, male athletes may exhibit concentric hypertrophy/remodeling more frequently than female athletes although the absolute numbers are low. Body size is also strongly associated with cardiac dimensions. The interpretation of cardiac dimensions in any athlete should be based on body-size independent cardiac indices as this facilitates the differential diagnosis of physiological versus pathological cardiac adaptation in athlete screening. Historically, scaling of cardiac data in athletes for individual differences in body size has been either entirely ignored or has used simple “ratiometric” scaling such as normalization of LV mass for individual differences in BSA (LV mass/BSA). We argue that this scaling process may not always be theoretically or practically accurate, resulting in cardiac indices that are still body size-dependent. This only confuses clinical decision-making. An “allometric” approach to scaling is theoretically sound in most cases and practically tends to lead to body size-independent cardiac indices. This evidence-based approach should be encouraged wherever possible and specifically within the sphere of sports cardiology and pre-participation screening. A correct understanding of determinants, type and extent of physiological cardiac adaptation is pivotal to correctly differentiate normal findings from potentially fatal cardiac diseases such as cardiomyopathies.
Article
Background: Cardiac size measurements require indexing to body size. Allometric indexing has been investigated in Caucasian populations but a range of different values for the so-called allometric power exponent (b) have been proposed, with uncertainty as to whether allometry offers clinical utility above body surface area (BSA)-based indexing. We derived optimal values forbin normal echocardiograms and validated them externally in cardiac patients.Methods and Results:Values forbwere derived in healthy adult Chinese males (n=1,541), with optimalbfor left ventricular mass (LVM) of 1.66 (95% confidence interval 1.41-1.92). LV hypertrophy (LVH) defined as indexed LVM >75 g/m1.66was associated with adverse outcomes in an external validation cohort (n=738) of patients with acute coronary syndrome (odds ratio for reinfarction: 2.4 (1.1-5.4)). In contrast, LVH defined by BSA-based indexing or allometry using exponent 2.7 exhibited no significant association with outcomes (P=NS for both). Cardiac longitudinal function also varied with body size: septal and RV free wall s', TAPSE and lateral e' all scaled allometrically (b=0.3-0.9). Conclusions: An optimalbof 1.66 for LVM in healthy Chinese was found to validate well, with superior clinical utility both to that of BSA-based indexing and tob=2.7. The effect of allometric indexing of cardiac function requires further study.
Article
Full-text available
Non-invasive imaging plays a growing role in the diagnosis and management of ischemic heart disease from its earliest manifestations of endothelial dysfunction to myocardial infarction along the myocardial ischemic cascade. Experts representing the North American Society for Cardiovascular Imaging and the European Society of Cardiac Radiology have worked together to organize the role of non-invasive imaging along the framework of the ischemic cascade. The current status of non-invasive imaging for ischemic heart disease is reviewed along with the role of imaging for guiding surgical planning. The issue of cost effectiveness is also considered. Preclinical disease is primarily assessed through the coronary artery calcium score and used for risk assessment. Once the patient becomes symptomatic, other imaging tests including echocardiography, CCTA, SPECT, PET and CMR may be useful. CCTA appears to be a cost-effective gatekeeper. Post infarction CMR and PET are the preferred modalities. Imaging is increasingly used for surgical planning of patients who may require coronary artery bypass.
Article
Background: To assess left ventricular myocardial deformation in patients with primary cardiac tumors. Methods: MRI was retrospectively performed in 61 patients, including 31 patients with primary cardiac tumors and 30 matched normal controls. Left ventricular strain and function parameters were then assessed by MRI-tissue tracking. Differences between the tumor group and controls, left and right heart tumor groups, left ventricular wall tumor and non-left ventricular wall tumor groups, and tumors with and without LV enlargement groups were assessed. Finally, the correlations among tumor diameter, myocardial strain, and LV function were analyzed. Results: Left ventricular myocardial strain was milder for tumor group than for normal group. Peak circumferential strain (PCS) and its diastolic strain rate, longitudinal strains (PLS) and its diastolic strain rates, and peak radial systolic and diastolic velocities of the right heart tumor group were lower than those of the left heart tumor group (all p<0.050), but the peak radial systolic strain rate of the former was higher than that of the latter (p=0.017). The corresponding strains were lower in the left ventricular wall tumor groups than in the non-left ventricular wall tumor group (p<0.050). Peak radial systolic velocities were generally higher for tumors with LV enlargement than for tumors without LV enlargement (p<0.050). Peak radial strain, PCS, and PLS showed important correlations with the left ventricular ejection fraction (all p<0.050). Conclusion: MRI-tissue tracking is capable of quantitatively assessing left ventricular myocardial strain to reveal sub-clinical abnormalities of myocardial contractile function.
Article
Objectives: To establish reference intervals for echocardiographic measures of longitudinal left ventricular function in adult English Springer spaniel (ESS) dogs. Animals: This study involved 42 healthy adult ESS. Methods: Animals were prospectively recruited from a general practice population in the United Kingdom. Dogs were examined twice, at least 12 months apart, to exclude dogs with progressive cardiac disease. Mitral annular plane systolic excursion, tissue Doppler imaging mitral annular velocities and two-dimensional speckle-tracking echocardiographic left ventricular longitudinal strain and strain rate were measured. Intraoperator and intraobserver variability were examined and reference intervals were calculated. The potential effects of body weight, age and heart rate on these variables were examined. Results: Intraoperator and intraobserver variability was <10% for all parameters except tissue Doppler imaging E' (the peak velocity of early diastolic mitral annular motion as determined by pulsed wave Doppler) and two-dimensional speckle-tracking echocardiographic variables, which were all <20%. Thirty-nine dogs were used to create reference intervals. Significant (but mostly weak) effects of age, heart rate and body weight on were detected. Reference intervals were similar to previously published values in different breeds. Clinical significance: Breed specific reference intervals for measures of longitudinal left ventricular function in the ESS are presented.
Article
The rationale for employing a nonlinear iterative least-squares technique for fitting the well-known power function to oxygen consumption–body weight data is set forth. Twenty-six sets of routine or standard metabolism data from six authors were used to demonstrate the relative merits of two methods of calculating parameter values for the power function. The conclusion was reached that if accuracy in predicting oxygen consumption over a wide range of values of body weight is desired, an iterative curve fitting method may be superior to the much used technique of performing a linear regression on logarithmically transformed data.
Article
Tissue Doppler imaging (TDI) is a novel method of color-coding myocardial velocity on-line. The objective of the present study was to evaluate endocardial velocity with TDI as a method of objectively quantifying alterations in regional contractility over a wide range induced by inotropic modulation. Myocardial length crystals were used to simultaneously assess regional left ventricular (LV) function, and high-fidelity pressure and conductance catheters were used to assess global LV contractility by pressure-volume relations in nine open-chest dogs. Mid-LV M-mode and two-dimensional color TDI images were recorded during control and inotropic modulation stages with dobutamine and esmolol. Predicted significant increases in TDI indices occurred with dobutamine: peak systolic velocity of 4.41 +/- 1.07 to 6.67 +/- 1.07 cm/s*, systolic time-velocity integral (TVI) of 0.43 +/- 0.12 to 0.62 +/- 0.10 cm*, and diastolic TVI of 0.49 +/- 0.11 to 0.71 +/- 0.17 cm*. Opposing significant decreases occurred with esmolol: peak systolic velocity of 4.46 +/- 0.94 to 2.31 +/- 0.81 cm/s*, systolic TVI of 0.47 +/- 0.12 to 0.19 +/- 0.11 cm*, and diastolic TVI of 0.55 +/- 0.11 to 0.33 +/- 0.11 cm* (*all P < .001 versus control). Changes in TDI peak systolic velocity were correlated with changes in fractional shortening (r = .88) and shortening velocity (r = .87) by sonomicrometry. Changes in TDI peak velocity from multiple mid-LV sites also correlated significantly with maximal elastance (r = .85 +/- .04) from pressure-volume relations. TDI measures reflect directional and incremental alterations in regional and global LV contractility and have the potential to quantify regional LV function.
Article
The regional function of the left ventricle can be visualized in real-time using the new strain rate imaging method. Deformation or strain of a tissue segment occurs over time during the cardiac cycle. The rate of this deformation, the strain rate, is equivalent to the velocity gradient, and can be estimated using the tissue Doppler technique. We present the strain rate as color-coded 2-dimensional cine-loops and color M-modes showing the strain rate component along the ultrasound beam axis. We tested the method in 6 healthy subjects and 6 patients with myocardial infarction. In the healthy hearts, a spatially homogeneous distribution of the strain rate was found. In the infarcted hearts, all the infarcted areas in this study showed up as hypokinetic or akinetic, demonstrating that this method may be used for imaging of regional dysfunction. Shortcomings of the method are discussed, as are some possible future applications of the method.
Article
The goals of this study were to examine peak systolic strain as an index of regional function in an animal model of inotropic stress and ischemia, and to compare these results with peak systolic myocardial tissue Doppler velocity (MDV). Myocardial tissue Doppler velocity is an objective measure of regional left ventricular responses to inotropic stimulation and ischemia, but it is affected by tethering from adjacent segments and translational movement. Myocardial Doppler strain (epsilon, relative change in length) is a more local measure of contractility, which can now be derived noninvasively from MDV. Eight dogs underwent graded dobutamine infusion followed by coronary occlusion. Epicardial 2-dimensional echocardiography and color MDV of the left ventricle were obtained and digitized from the short-axis view at baseline and with dobutamine doses of 2, 4, and 8 microg/kg per minute. These were repeated 0, 10, 20, 45, and 90 seconds after occlusion of the left anterior descending artery (LAD) (n = 3) or circumflex coronary artery (n = 5). Dobutamine was continued at 8 microg/kg per minute during coronary occlusion. The peak systolic radial MDV (cm/s) and systolic strain (epsilon(s), percent thickening) in the anterior and posterior walls were measured off-line at each stage. Dobutamine caused an increase in MDV (P =.0001) and epsilon(s) (P =.09) above baseline values. Coronary occlusion caused a reduction in wall motion; after 45 seconds, all nonperfused segments were hypokinetic. There was a corresponding decrease in MDV and epsilon(s), but this occurred earlier for epsilon(s), and the difference between ischemic and nonischemic segments was greater for epsilon(s) than for MDV (P <. 03). Nonischemic regions trended to an increase in epsilon(s) (compensatory hyperkinesis), whereas MDV trended downward, probably reflecting the global decrease in left ventricular function. Both MDV and epsilon(s) increase with dobutamine and decrease during ischemia. epsilon(s) appears to respond to local ischemia earlier than MDV, perhaps because it is a more local measure. Thus epsilon(s) may prove to be an accurate parameter for the clinical recognition of regional ischemia.
Article
Regional strain rate in the left ventricle can be assessed in real time and color mapped. The method is termed strain rate imaging (SRI), and findings correspond well with 2-dimensional echocardiography. This study addresses SRI as a method for localizing coronary lesions, compared with standard echocardiography. Twenty patients with acute myocardial infarction who underwent coronary angiography for clinical reasons were examined with SRI and standard echocardiography. Wall motion was graded by SRI color and separately by wall thickening. Strain rate imaging and 2-dimensional echocardiography results agreed well. An infarct-related artery was identified from angiograms combined with electrocardiograms. Both methods identified an infarct-related artery in 19 possible cases and had equal sensitivity and specificity for wall segments affected by lesion. Combining the information from both methods did not change accuracy. The study validates SRI as a method for assessing regional wall function in coronary artery disease. The advantages of SRI are discussed and measurements of strain rates are given.
Article
Strain rate imaging is a new modality in echocardiography intended for analysis of left ventricular function. This modality extends ultrasonographic techniques for analysis of tissue velocities by providing information about rates of local myocardial compression and expansion. Cyclic cardiac deformation is a complex process. Precision and accuracy of real-time strain rate (rtSR) measurements have not been studied under controlled laboratory conditions. Using a cyclically compressed tissue-mimicking gelatin phantom, we compared rtSR values to corresponding strain rate values calculated off line from local tissue velocities measured by Doppler echocardiography. We tested a clinically relevant range of strain rates (0.5 - 3.5 sec(-1)) and different angles of insonation. Initial tests showed high precision (r > or = 0.973, P < 0.001), but the assessment of accuracy (bias < or = 0.559 sec(-1)) suggested a trend toward systematic underestimation of the reference values. We suspected a confounding influence of a clutter filter and repeated the tests with the filter inactive. The resulting accuracy improved tenfold (bias < or = 0.045 sec(-1)), and the systematic underestimation was no longer present. We conclude that the rtSR is precise and accurate for a range of the tested values.