3.6 Repeatability test of 3D strain parameters
The intra-observer and inter-observer parameters showed that the
intra-group repeatability test intraclass correlation coefficient
(ICC ) of the left ventricular Tor and MCI were 0.868 and 0.899,
respectively, and the inter-group repeatability test ICCs were
0.878 and 0.894, respectively; this indicated that the reliability and
repeatability of the above parameters were relatively high (Figure
6).
Figure 6: 3D strain Parameters: Left ventricular Tor and MCI
repeatability test (Bland–Altman diagram)
Discussion
As an autoimmune disease with the ability to impart chronic damage to
multiple organs, SLE is characterized by remission and deterioration.
Moreover, cardiovascular damage is an important cause of death and is
becoming increasingly serious [5]. However, heart
damage is often hidden in the early stage and can be easily ignored; if
it can be detected earlier, prevention will be of great significance to
the prognosis of the disease [6]. At the point
when heart damage in SLE can be detected by two-dimensional ultrasound,
the myocardium is seriously damaged, and the possibility of recovery is
low. The 3D-STI technique eliminates the plane limitation of
two-dimensional ultrasound and allows for comprehensive analysis of left
ventricular wall motion such that the actual situation of the left
ventricle is accurately reflected [7].
Compared with the control group,
this study showed that LVEF and LVEDV in the mild-to-moderate and the
severe groups decreased significantly, LV EDmass, and LV ESmass
increased significantly. There was no statistically significant
difference in terms of LVESV in the three studied groups. Moreover,
although SPI reflected left ventricular geometry, there was no
significant difference in the three studied groups, indicating that the
early left ventricular systolic function may be locally impaired in SLE;
however, the decline in function is not obvious, and the overall
function is still within the normal range [8]. At
the same time, there was a statistically significantly decrease in GLS,
GCS and LVtw in the mild-to-moderate and severe groups compared to the
control group, indicating that the left ventricular systolic function is
damaged in the early stage. This may be due to fact that SLE can lead to
the deposition of immune complexes in the cardiovascular system or
inflammatory changes after complement activation that result in the
degeneration of collagen fibers in the myocardial interstitium.
Ultimately, this leads to damage to myocardial systolic function, which
is consistent with the findings of Huang et al[9].
The results also showed that the sensitivity, specificity, and AUC of
Tor were higher than those of GLS and GCS, indicating that LVtw may be a
better index to reflect the changes in left ventricular systolic
function than the three-dimensional strain GLS and GCS, whereas GLS is
more sensitive in the three-dimensional strain[10]. This may be due to the high sensitivity of
subendocardial myocardium to ischemia, so coronary artery lesions,
endocarditis and myocardial metabolic disorders occur in patients with
SLE. These lesions are the first to cause longitudinal myocardial
injury, which lead to a decrease in systolic motor function along the
long axis of the myocardium. Therefore, we conclude that the overall
longitudinal strain of the left ventricle should be more sensitive to
changes in ventricular systolic function than the circumference. Left
ventricular torsion is also affected by the degree of myocardial
contraction, the arrangement of endomyocardial muscle fibers, and the
contraction balance. This is because the outer myocardial torque is
larger and the contraction torque is greater. The left ventricular
torsion direction is consistent with the outer myocardial rotation
direction. SLE leads to a decrease in left ventricular myocardial
elastic deformation ability, torsion abnormality, and amplitude, thus
reflecting a decrease in left ventricular systolic function more
accurately [11].
However, during collection, we found that the lack of clear anatomical
reference in the apical part of the left ventricle led to differences in
the location of LVtw in different patients, resulting in measurement
errors. Therefore, the left ventricular Tor, which avoids this error,
can be introduced as another index to evaluate left ventricular systolic
function [12]. It was found that there was a
statistically significantly decrease in Tor in the mild-to-moderate and
severe groups compared to the control group, indicating that Tor can be
used as an effective index to reflect the myocardial damage caused by
SLE in the early stage. The ROC curve also showed that the sensitivity,
specificity, and AUC of Tor were higher than those of LVtw, indicating
that left ventricular Tor may reflect changes in left ventricular
systolic function better than LVtw, with higher repeatability. At the
same time, we found that myocardial deformation in the three-dimensional
space is caused by myocardial strain and torsional motion. Thus, the new
parameter MCI, which is composed of GLS and LVtw, may be used to
evaluate left ventricular systolic function more comprehensively. The
results showed that there was a statistically significantly decrease in
MCI in the mild-to-moderate and severe groups compared to the control
group, and the repeatability was high. The ROC curve showed the highest
area and sensitivity under the left ventricular MCI curve, which was
consistent with the results of Mornos et al, indicating that no single
form of exercise can fully reflect the movement of the left ventricular
myocardium [13]. At the same time, correlation
analysis showed that there was a good correlation between MCI and
hs-TropT [14]. Therefore, MCI can be used as a new
sensitive index for the early detection of SLE heart injury and provide
a basis for clinical intervention, timely adjustment, or change of drugs
to avoid aggravation of myocardial damage, resulting in irreversible
myocardial injury.
PSD is the standard deviation of the peak time of the longitudinal
strain in 17 segments of the left ventricle. There was a statistically
significantly increase in PSD in the mild-to-moderate and severe groups
compared to the control group, indicating that the dispersion of
myocardial mechanical motion is increased, that is, myocardial systolic
synchronization is worse [15]. It has been
suggested that the deposition of SLE-associated immune complexes in the
cardiovascular system may lead to degeneration of cardiomyocytes and
myocardial sympathetic nerves, which directly leads to the damage of the
normal function of cardiomyocytes and the dysfunction of nerve fibers in
the myocardial layer; this, in turn, has a serious impact on myocardial
synchronous movement.
Limitations
The limitations of this study are as follows: (1) the image must be
clear and of high quality; (2) the inspection operation and image
post-processing greatly depend on the accuracy of human operation; (3)
the sample size is small; (4) there are individual differences.
Conclusion
SLE can cause left ventricular systolic function damage in the early
stage, and 3D-STI can be used to monitor myocardial subclinical injury
at the early stage. The new parameters, including MCI and Tor, are
particularly relevant as they can provide an objective imaging basis for
early clinical diagnosis of left ventricular myocardial involvement and
guide prognosis in patients with SLE.
Conflict of interest
disclosure statement
The authors declare that they have no conflict of interest.