Download `kinetic energy index` assessed by vector flow mapping in patients

European Heart Journal – Cardiovascular Imaging (2013) 14, 253–260
doi:10.1093/ehjci/jes149
Abnormal early diastolic intraventricular flow
‘kinetic energy index’ assessed by vector flow
mapping in patients with elevated filling pressure
Yoshie Nogami, Tomoko Ishizu*, Akiko Atsumi, Masayoshi Yamamoto,
Ryo Kawamura, Yoshihiro Seo, and Kazutaka Aonuma
Faculty of Medicine, Division of Clinical Medicine, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8575, Japan
Received 17 April 2012; accepted after revision 26 June 2012; online publish-ahead-of-print 20 July 2012
Aims
Recently developed vector flow mapping (VFM) enables evaluation of local flow dynamics without angle dependency.
This study used VFM to evaluate quantitatively the index of intraventricular haemodynamic kinetic energy in patients
with left ventricular (LV) diastolic dysfunction and to compare those with normal subjects.
.....................................................................................................................................................................................
Methods
We studied 25 patients with estimated high left atrial (LA) pressure (pseudonormal: PN group) and 36 normal suband results
jects (control group). Left ventricle was divided into basal, mid, and apical segments. Intraventricular haemodynamic
energy was evaluated in the dimension of speed, and it was defined as the kinetic energy index. We calculated this
index and created time-energy index curves. The time interval from electrocardiogram (ECG) R wave to peak index
was measured, and time differences of the peak index between basal and other segments were defined as DT-mid and
DT-apex. In both groups, early diastolic peak kinetic energy index in mid and apical segments was significantly lower
than that in the basal segment. Time to peak index did not differ in apex, mid, and basal segments in the control group
but was significantly longer in the apex than that in the basal segment in the PN group. DT-mid and DT-apex were
significantly larger in the PN group than the control group. Multiple regression analysis showed sphericity index, E/E′
to be significant independent variables determining DT apex.
.....................................................................................................................................................................................
Conclusion
Retarded apical kinetic energy fluid dynamics were detected using VFM and were closely associated with LV spherical
remodelling in patients with high LA pressure.
----------------------------------------------------------------------------------------------------------------------------------------------------------Keywords
Vector flow mapping † Angle independency † Pseudonormalization † Suction
Introduction
Doppler echocardiography is widely used as a non-invasive
method to evaluate left ventricular (LV) diastolic filling. However,
transmitral inflow is affected by several factors, such as ventricular
relaxation, suction, chamber compliance, left atrial (LA) pressure,
and cardiac preload and afterload.1,2 These factors have made it
difficult to distinguish a pseudonormal pattern from a normal
pattern.
Increasing LV chamber stiffness and elevated LA pressure lead to
a pseudonormal filling pattern that appears normal.3 A diastolic
intraventricular pressure gradient pulls blood to the apex in the
normal heart, whereas increased LA pressure leads to pushing
of blood from the base to apex in the pseudonormal filling
pattern.4 Because it is difficult to distinguish between a normal
and pseudonormal pattern, we use a combination of transmitral
inflow and a number of indices to evaluate these patterns. Primarily, pulmonary venous flow, transmitral annular motion measured
by tissue Doppler imaging, and propagation velocity of early diastolic mitral inflow (Vp) are often used in pattern evaluation.5 – 7
Although in patients with pseudonormal pattern, intraventricular
filling delay with abnormal vortex formation has been reported,8 it
is limited by qualitative assessment. Bolger et al.9 have been suggested using cardiac MRI that LV diastolic vortical flow may help
conserve the kinetic energy of diastolic mitral flow to ensuing ejection. Phase contrast velocity mapping of cardiac MRI has been
* Corresponding author. Tel: +81 29 853 3143; fax: +81 29 853 3143, Email: [email protected]
Published on behalf of the European Society of Cardiology. All rights reserved. & The Author 2012. For permissions please email: [email protected]
254
validated and is reproducible and useful in research setting;10
however, it is very time consuming and not appropriate to apply
for the patients with heart failure. Recently developed vector
flow mapping (VFM), which provides the velocity component in
the perpendicular direction to the echocardiographic Doppler
beam, enables evaluation of local flow dynamics and structures
without angle dependency.11 Because VFM was based on the twodimensional (2D) colour Doppler echocardiography, it can easily
be performed as a part of the routines echocardiography. Therefore, VFM may be suitable for quantification and assessment
of intraventricular circulatory flow during diastole in abnormal
human left ventricle. The accuracy of the velocity vector derived
from VFM has been validated only by computer-simulated
phantom;12 however, not yet validated in vivo. Therefore, the
present study based on the preliminarily setting to assess
whether the VFM method, which is under development, can
reveal the abnormal flow dynamics quantitatively in human heart.
Accordingly, the purpose of this study was to assess flow kinetic
energy index quantitatively in both normal subjects and patients
with estimated high LA pressure using VFM.
Methods
Study population
This study included 25 patients with estimated high LA pressure aged
64 + 15 (range 21 – 85) years [pseudonormal LV filling (PN) group].
Diagnosis of high LA pressure was performed based on their ejection
fraction (EF) preserved (≥50%) or impaired (,50%) according to the
recommendation of EAE/ASE.13 Thirty-six subjects aged 43 + 15
(range 22 – 68) years with normal echocardiographic studies were
also enrolled as control subjects (control group). Exclusion criteria
were non-sinus rhythm, aortic regurgitation, significant mitral valvular
disease, and insufficient quality of echocardiographic images. Subjects
with E/A , 1 were also excluded to eliminate the influence of mitral
inflow velocity in the comparison of intraventricular haemodynamics.
Echocardiography
Echocardiographic examination was performed in the left lateral decubitus position using a ProSound a10TM (Hitachi-Aloka Medical,
Ltd., Tokyo, Japan) equipped with multifrequency probe (2.5 MHz
transducer). Left ventricular end-diastolic dimension (Dd), intraventricular septum wall thickness diameter at end-diastole (IVSTd), posterior
wall thickness diameter at end-diastole (PWTd), and LV end-systolic
dimension (Ds) were measured on M-mode images obtained in
the parasternal long-axis view. Left ventricular end-diastolic volume
(EDV) and end-systolic volume (ESV) were calculated by Teichholz’s
method.14 In addition, the sphericity index was calculated as the
ratio of short- to long-axis dimension in the four-chamber view at enddiastole. The long-axis dimension was measured from the apex to the
middle of the mitral valve annulus, and the short-axis dimension was
measured at the point where it perpendicularly intersects the midpoint
of the long axis.15,16
In the apical four-chamber view, pulsed-wave Doppler indices were
obtained with the sample volume set at the tip of the mitral valve leaflets. E and deceleration time of E (DcT), A, and the E/A ratio were
measured. Using colour Doppler imaging with an M-mode cursor
placed through the centre of the apical view, we measured Vp as
the slope of the first aliasing velocity during early filling from the
mitral valve. Aliasing velocity was set to 40 – 50% of the peak
Y. Nogami et al.
transmitral E wave velocity.17 The ratio of E to Vp (E/Vp) was directly
proportional to LA pressure and can be used to predict LV filling pressures.13,18 Tissue Doppler imaging of mitral annular motion was
recorded at the septal and lateral annular borders from the apical fourchamber view. Early transmitral annular velocity (E′ ) was obtained
from the average of septal and lateral E′ values and was used as the
index of LV relaxation.19 The ratio of E to E′ (E/E′ ) was used as the
index of LV filling pressure.19
Elevated LA pressure was defined which diagnostic values are
recommended in the consensus statement of the Heart Failure
and Echocardiography Association of the European Society of
Cardiology.13,18,20 – 22
Twist
Peak twist, twisting rate, and untwisting rate of the left ventricle were
measured as the difference between basal and apical rotation and rotational velocities, respectively, in the short-axis view by 2D speckle
tracking.23 – 25
Vector flow mapping
Intraventricular flow images were recorded in the apical threechamber view with colour Doppler imaging. In VFM, the flow
vectors are found by analysing the spatial distribution of the 2D
flow.12 The velocity component of the orthogonal echo beam (v)
was estimated from the velocity component of echo beam direction
(u) by VFM. Then, the vector component (U ) was calculated as
p
U ¼ (u 2 + v 2). Vector flow mapping-derived velocity vector has
been validated using computer phantom and has been reported the
good agreement.12 We defined this vector component as the kinetic
energy index. The kinetic energy index is proposed in the present
study to investigate of intraventricular haemodynamics. The index, Ik,
is defined as equation (1).
√
s u2 + v 2
rs =
Ik =
u2 + v 2
N i=N
s
r
i=N
(1)
i=N
where u and v are velocity in x and y direction. The blood density, r, is
a constant of 1.05 g/cm3. The number, N, represents the number of
pixels in the segment of interest. Other symbols are detailed in the
sections below. Note that the kinetic energy index is the linear to
the velocity magnitude although the dimension of kinetic energy is proportional to the velocity squared as described in equation (2) because
of three reasons.
Ik / |V|
1 2
2
/ |V|
Ek = m|V|
2
(2)
Firstly, this can be regarded intuitively linear relationship between the
measured velocity and the proposed index. Secondly, the noise tolerance of the index is considered to be better than that of the kinetic
energy, because the high-order quantities such as velocity squared
are easily contaminated by unexpected measurement errors such as
Doppler spike noises. Thirdly, the behaviour of the index is similar
to the kinetic energy. Ek: kinetic energy, Ik: kinetic energy index,
s: area each pixcel [cm2].
In the present study, the sum of the absolute value of the kinetic
energy index in each vector unit was calculated as equivalent to
kinetic flow energy in the region of interest. Spatial resolution of
X and Y direction is 0.05 cm. Therefore, minimum unit has been
255
Flow kinetic energy assessed by vector flow mapping
Figure 1 Images of vector flow mapping. Velocity vectors were identified without angle-dependency (left panel). The left ventricle was
divided into three segments: base, mid, and apex (right panel).
calculated by 0.05 × 0.05 cm. The apical long-axis image consists of
multiple vector units, each with a size of 0.05 by 0.05 cm. The left ventricle was divided into the basal, mid, and apical segments, and use the
calculation of the kinetic energy index to correct for each segment
area. Then, the sum of the absolute value of each unit of the kinetic
energy index was obtained (Figure 1). The sum of the kinetic energy
index was calculated frame by frame at a frame rate in the range of
25 –40 frames/s, and time-energy curves were created. A schematic
of the time-energy index curve during one cardiac cycle is shown in
Figure 2. There were three peaks: systole and early and late diastole.
In the present study, we focused on the second peak during early diastole. The time interval from the R wave of the ECG to the second
peak kinetic energy index was measured in the basal, mid, and apical
segments and was corrected for RR interval (T-base, T-mid, and
T-apex, respectively). Furthermore, the time differences of the peak
kinetic energy index between the basal and the other two segments
were defined as DT-mid and DT-apex.
Figure 2 Schema of time-flow analysis. The Y-axis indicates the
Statistical analysis
All data are presented as mean + SD. Intergroup comparisons were
conducted with the Student t-test. One-way ANOVA was used for
intragroup comparison. When analysis revealed a significant difference,
a post hoc comparison test was performed with Bonferroni’s test. The
relation between two parameters was analysed by the linear regression
method, and stepwise multiple regression analysis was used to study
the independent factors correlating with kinetic energy. A receiver
operating characteristic (ROC) curve was operated to determine
sensitivity and specificity for discriminating between normal and
impaired diastolic function. Values of P , 0.05 were considered to
indicate significant difference. Statistical analysis was performed using
JMP 9 (SAS, Inc., Cary, NC, USA).
sum of the absolute value of kinetic energy index in each
segment, and the X-axis indicates time from the QRS wave.
The black solid line indicates the basal, dotted line the mid, and
grey solid line the apical segment.
Results
Subject background
Clinical characteristics are shown in Table 1. Patients in the PN
group were significantly older than subjects in the control group.
256
Table 1
Y. Nogami et al.
Characteristics of subjects
Characteristics
PN group
...............................................................................................
All (n 5 25)
Preserved EF (n 5 14)
Control group (n 5 36)
Low EF (n 5 11)
...............................................................................................................................................................................
Age (years)
64 + 15**
66 + 14**
62 + 17**
43 + 15
Sex (male/female)
16/9
7/7
9/2
24/12
Height (cm)
Weight (kg)
160 + 11**
58 + 14
157 + 11**
57 + 14
164 + 9
61 + 13
167 + 8
63 + 11
BMI (kg/m2)
23 + 4
23 + 4
22 + 4
22 + 4
SBP (mmHg)
120 + 18
123 + 10
117 + 25
120 + 22
DBP (mmHg)
HR (bpm)
69 + 15
67 + 15
64 + 12
63 + 8
75 + 16
72 + 20
70 + 15
65 + 12
NYHA class
I (n ¼ 9)
II (n ¼ 8)
III (n ¼ 6)
IV (n ¼ 2)
I (n ¼ 6)
II (n ¼ 5)
III (n ¼ 1)
IV (n ¼ 2)
I (n ¼ 3)
II (n ¼ 3)
III (n ¼ 5)
IV (n ¼ 0)
Data are shown as means + SD.
PN, pseudonormal; BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure; HR, heart rate; NYHA, New York Heart Association.
*P , 0.05.
**P , 0.01 vs. control group
Table 2
Echocardiographic parameters
Parameters
PN group
..............................................................................................
All (n 5 25)
Preserved EF (n 5 14)
Control group (n 5 36)
Low EF (n 5 11)
...............................................................................................................................................................................
IVSTd (cm)
0.97 + 0.3*
1.03 + 0.3*
0.89 + 0.2
0.82 + 0.2
PWTd (cm)
Dd (cm)
0.92 + 0.2**
5.4 + 1.2**
0.99 + 0.2**
4.7 + 0.9
0.85 + 0.2
6.3 + 0.9**,‡
0.81 + 0.1
4.8 + 0.3
Ds (cm)
4.0 + 1.5**
2.9 + 0.7
5.4 + 0.9**,‡
3.0 + 0.4
LVEF (%)
52 + 20**
68 + 8
32 + 9**,‡
68 + 8
EDV (mL)
ESV (mL)
151 + 77**
83 + 72**
107 + 44
35 + 22
208 + 74**,‡
144 + 66**,‡
109 + 18
35 + 11
SV (mL)
68.4 + 23.4
72.1 + 25.9
63.6 + 20.0
74.4 + 13.9
Sphericity index
Twist (8)
1.67 + 0.26**
9.0 + 10.0
1.77 + 0.24
11.7 + 11.7
1.55 + 0.24**
4.6 + 4.3
1.93 + 0.22
12.6 + 6.7
Twisting rate (8/s)
50.5 + 44.6*
64.4 + 51.5
27.3 + 13.1**
79.3 + 29.7
Untwisting rate (8/s)
63.8 + 43.7*
77.6 + 49.7
40.8 + 16.1*
95.4 + 39.2
Data are shown as means + SD.
PN, pseudonormal; IVSTd, intraventricular septum wall thickness diameter at end-diastole; PWTd, posterior wall thickness diameter at end-diastole; Dd, left ventricular
end-diastolic dimension; Ds, left ventricular end-systolic dimension; LVEF, left ventricular ejection fraction; EDV, end-diastolic volume; ESV, end-systolic volume; SV, stroke volume.
*P , 0.05.
**P , 0.01 vs. control group.
†
P , 0.05.
‡
P , 0.01 vs. preserved EF.
However, body mass index, blood pressure, and heart rate did not
differ significantly between the two groups.
Conventional echocardiography
Echocardiographic parameters are shown in Table 2. In the PN
group, wall thickness was significantly greater, luminal diameter,
EDV, and ESV were larger, and the sphericity index was lower
than those values in the control group. Particularly, luminal
diameter and LV volume were significantly greater and the sphericity index was lower in patients with low EF group compared with
other two groups. Although LVEF in the PN group with low EF was
lower than that in other two groups, stroke volume (SV) did not
differ significantly between these three groups. Peak systolic
twist did not differ significantly between the PN and control
groups. However, twisting rate and untwisting rate in the PN
group with low EF were significantly lower than those in the
257
Flow kinetic energy assessed by vector flow mapping
Table 3
Doppler echocardiographic indices
Parameters
PN group
.................................................................................................
All (n 5 25)
Preserved EF (n 5 14)
Control group (n 5 36)
Low EF (n 5 11)
...............................................................................................................................................................................
E (cm/s)
91.3 + 26.9**
90.4 + 26.0
92.5 + 29.1
76.2 + 16.7
A (cm/s)
57.3 + 24.8
63.9 + 22.4
48.9 + 26.2
53.3 + 14.4
E/A
DcT (ms)
1.80 + 0.7*
200.2 + 86.3
1.51 + 0.5
211.2 + 97.5
2.2 + 0.8**,‡
186.3 + 71.6
1.46 + 0.3
201.6 + 54.2
A duration (ms)
145.5 + 32.5
144.4 + 36.9
147.2 + 26.9
136.0 + 20.2
E′ (cm/s)
6.0 + 2.0**
7.1 + 1.7**
4.7 + 1.4**,†
11.9 + 2.8
E/E′
Vp (cm/s)
16.5 + 6.8**
33.3 + 13**
13.0 + 3.1**
39.6 + 11.9*
21.0 + 7.6**,‡
26.3 + 10.1**,‡
6.6 + 1.8
48.4 + 8.9
3.1 + 1.4**
2.5 + 1.4*
3.9 + 1.1**,‡
1.6 + 0.4
E/Vp
Data are shown as means + SD.
PN, pseudonormal; E, early diastolic mitral inflow velocity; A, late diastolic mitral inflow velocity; E/A, transmitral flow early to late diastolic velocity ratio; DcT, deceleration time of
E; E′ , early transmitral annular velocity; E/E′ , ratio of early transmitral flow velocity to early diastolic transmitral annular velocity; Vp, propagation velocity of early diastolic mitral
inflow.
*P , 0.05.
**P , 0.01 vs. control group.
†
P , 0.05.
‡
P , 0.01 vs. preserved EF.
control group (Table 2). Doppler echocardiographic indices are
shown in Table 3. In the PN group, E, E/A, E/E′ , and E/Vp values
were significantly higher, and E′ and Vp values were significantly
lower than those in the control group. Further, E′ and Vp in
patients with low EF were significantly lower, and E/A, E/E′ , and
E/Vp were higher than those of other two groups.
Peak kinetic energy index
In the PN and control groups, early diastolic peak kinetic energy
indices in the mid and apical segments were significantly lower
than those in the basal segment (Figure 3A). Per cent change of
decline in the kinetic energy index from base to apex was similar
between the PN group (44 + 22%) and the control group (48 +
21%). The early diastolic peak kinetic energy values of the basal,
mid, and apical segments were not significantly different between
the two groups. Additionally, per cent change of decline from
base to apex was not significantly difference between the PN
group with low EF (39 + 26%) and other two groups (preserved
EF; 48 + 18, control; 48 + 21%) (Figure 3B).
Timing of peak kinetic energy index
In the control group, T-mid and T-apex did not differ from T-base.
In contrast, in the PN group, T-mid (701 + 159 ms) and T-apex
(771 + 195 ms) were significantly longer than T-base (635 +
132 ms) (P , 0.01) (Figure 3A). Furthermore, T-mid (793 +
171 ms) and T-apex (889 + 201 ms) in the PN group with low
EF were significantly longer compared with other two groups
(control: T-mid; 638.0 + 128.0 ms, T-apex; 635 + 136 ms, preserved EF: T-mid; 628 + 107 ms, T-apex; 678 + 135 ms) (P ,
0.01). On the other hand, these times were not significant
between the PN group with preserved EF and the control
group. Moreover, DT-mid and DT-apex in the PN group were significantly longer than those in the control group (DT-mid; 65 + 66
vs. 5 + 22 ms, DT-apex; 135 + 123 vs. 2 + 45 ms, P , 0.01)
(Figure 4A). Subjects with a DT-apex , 0 ms comprised 12% of
the PN group and 58% of the control group (P , 0.01). Additionally, in the PN group, DT-apex was significantly longer compared
with DT-mid (P , 0.01).
DT-mid and DT-apex in patients with low EF (DT-mid; 119 +
61, DT-apex; 214 + 128 ms) were significantly longer than those
of in patients with preserved EF (DT-mid; 23 + 28, DT-apex;
73 + 78 ms, P , 0.01) and control group (DT-mid; 5 + 22,
DT-apex; 2 + 45 ms, P , 0.01) (Figure 4A).
In univariate analysis, DT-apex showed significant negative correlation with the sphericity index (r ¼ 20.50, P , 0.01)
(Figure 5A), LVEF (r ¼ 20.61, P , 0.01) (Figure 5B), E′ (r ¼
20.56, P , 0.01), twisting rate (r ¼ 20.40, P , 0.01), and untwisting rate (r ¼ 20.38, P , 0.01) (Figure 5C) and significant positive
relation with EDV (r ¼ 0.57, P , 0.01), ESV (r ¼ 0.62, P , 0.01),
LV short-axis dimension at end-diastole (r ¼ 0.63, P , 0.01), and
E/E′ (r ¼ 0.71, P , 0.01) (Figure 5D). Multiple regression analysis
indicated the variables of the sphericity index, and E/E′ to be
significant independent determinants of DT-apex.
Receiver operating characteristic curve analysis revealed that
DT-apex was the significant index with which to distinguish
the PN group from the normal group (Table 4). DT-apex
.0 ms showed 96% sensitivity and 42% specificity for the detection of pseudonormalization (area under the curve, 0.86; accuracy, 64%).
Discussion
A novel finding of the present study was that peak kinetic energy
during the early diastolic phase was significantly delayed from
base to apex in the PN group using VFM; however, the attenuation
in intraventricular energy was similar between groups.
258
Figure 3 Intraventricular peak magnitude of kinetic energy
index and timing. The scatter chart shows the absolute value of
peak kinetic energy index in each segment and time to peak
kinetic energy index from the QRS wave in descending order
from base, mid, to apex. Open symbols indicate data from the
control group, and grey symbols indicate data from the PN
group (A). Bar graph shows the per cent change of decline
from base to mid and apex. White bar indicates control group,
grey bar indicates preserved EF, and black bar is low EF (B).
**P , 0.01 vs. control group, †P , 0.05, ‡P , 0.01 vs. base.
In the present study, DT-apex correlated with the short-axis dimension but not with the long-axis dimension and sphericity index.
In other words, an enlarged LV short-axis dimension and spherical
cardiac chamber related to timing of peak kinetic energy delay at
the apex. This result was consistent with that of the previous
study in which LV spherical remodelling was related to delayed
apical relaxation.26 Left ventricular geometry was found to be an
important index of ventricular remodelling in patients with cardiovascular disease,27 and the untwisting rate is related to the
maximum rate of developed LV pressure (dP/dtmax).28 Diminished
LV torsion has been reported to be associated with reduced LV
suction.24,29,30 In the present study, reduced untwisting rate was
associated with delayed DT-apex. Thus, this would suggest that
rapid untwisting was the critical mechanism for prompt distribution
of flow kinetic energy in the diastolic intraventricular flow field.
DT-apex could be obtained easily with VFM software and the
colour Doppler 2D video image data set.
Receiver operating characteristic analysis showed the cut-off
value for DT-apex to be 0 ms. A DT-apex of ,0 ms means that
Y. Nogami et al.
Figure 4 Comparison of DT-mid and DT-apex. Upper line
chart shows comparison of the time difference from base to
mid and apex between PN and control groups. White circles indicate the control group, and grey circles indicate the PN group
(A). Lower line chart shows comparison of these time difference
between three groups. White symbols indicate the control group,
grey symbols indicate preserved EF, and black symbols show low
EF (B). **P , 0.01 vs. control, ‡P , 0.01 vs. preserved EF.
the time to peak kinetic energy index occurred earlier in the
apex than in the base. We considered this kinetic energy present
at the apex in early diastole to be the result of suction flow and,
therefore, that VFM-derived kinetic energy can be used to quantitatively assess suction flow at the apex.
The magnitude of the kinetic energy index at the apex in both
the PN group was maintained at a level comparable with that of
the control group. There was no difference in the magnitude of
the intraventricular kinetic energy index from the base to the
apex between groups, but the time of arrival from base to apex
varied. Particularly, DT-apex became gradually longer from
control to the PN group with preserved EF, low EF. Then, the
change of time delay in apex could be affected by enlarged LV
volume and spherical chamber geometry. Consequently, this suggested that lost intraventricular flow kinetic energy index could
be absorbed through the wall of the left ventricle and converted
into heat energy because kinetic energy index was lost from the
left ventricle, which is reflected by SV, at approximately the
same level in both groups.
259
Flow kinetic energy assessed by vector flow mapping
Figure 5 Scatterplots showing correlation between left ventricular geometry (A) and cardiac function (B – D) and DT-apex. White circles
indicate data from the control group, and grey circles indicate data from the PN group.
Table 4
ROC curve analysis
Variable
Cut-off value
AUC area
E/A
.1.5
0.62
DcT
E′
,192
,8.0
0.53
0.97
E/E′
.10.0
Vp
Untwisting rate
,45
,71
LVEF
EDV
ESV
P-value
Sensitivity
Specificity
Accuracy
0.03
56
50
52
0.94
,0.01
52
88
42
94
46
92
0.98
,0.01
94
94
95
0.82
0.74
,0.01
0.03
81
75
55
66
66
70
,65
0.73
,0.01
60
61
61
.112
.35
0.70
0.68
,0.01
,0.01
72
68
56
56
62
61
...............................................................................................................................................................................
Sphericity index
,1.78
0.77
,0.01
73
78
75
DT-apex
.0
0.86
,0.01
96
42
64
ROC, receiver operating characteristic; AUC, area under the curve; CI, confidence interval; E/A, transmitral flow early to late diastolic velocity ratio; DcT, deceleration time of E;
E′ , early transmitral annular velocity; E/E′ , ratio of early transmitral flow velocity to early diastolic transmitral annular velocity; Vp, propagation velocity of early diastolic mitral
inflow; LVEF, left ventricular ejection fraction; EDV, end-diastolic volume; ESV, end-systolic volume; DT-apex, time difference of peak kinetic energy index between basal and apical
segments.
Limitations
While Uejima et al.12 have reported that the flow vector derived
from VFM was in good agreement with a computer-simulated
phantom, in vivo validation of energy has not been performed.
Moreover, the low frame rate is another limitation of the
VFM technique. An improvement to the software algorithm is currently in progress, and this limitation should be overcome in the
future.
260
This study was the preliminary study using with VFM in the
clinical settings. Hence, the study population was heterogeneity
and sample size was small in this study. Additionally, subjects
with normal EF and with low EF were mixed and included
only the patients with the ratio of E/A . 1; therefore, the transition of transmitral inflow pattern cannot evaluate in this study.
Evaluation in the patients with E/A , 1 was required in the
future research.
Ageing is an important factor affecting the LV diastolic function,
and also the intraventricular haemodynamics. The lack of agematched healthy control is another limitation of the present
study. To elucidate the abnormal haemodynamics in impaired LV,
characteristics of normal LV flow kinetic energy index should be
described in different age group in the future.
Conclusion
Retarded intraventricular apical flow velocity was detected in using
VFM and the retarded flow propagation were closely associated
with LV spherical remodelling in patients with elevated filling pressure. Left ventricular early diastolic function could be quantitatively
assessed from haemodynamic variables using VFM.
Acknowledgements
The authors thank the technologists in the clinical laboratory in
Tsukuba University Hospital for their help with the data collection.
In particular, special thanks to Takashi Okada in Hitachi-Aloka and
Tomohiko Tanaka in Hitachi central research laboratory.
Funding
This study was supported by a grant from Hitachi-Aloka Medical, Ltd.
Conflict of interest: none declared.
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