Discussion
Recent studies have highlighted the presence of viable myocardium,
including stunned and hibernating myocardium, within areas of RWMA after
AMI. Viable myocardium refers to myocardial tissue that can recover its
function, either partially or completely, upon restoration of blood
supply. Effective revascularization can lead to functional recovery of
viable myocardium, improving clinical symptoms and prognosis. On the
other hand, non-viable myocardium does not regain its function even with
successful revascularization. Therefore, the assessment of myocardial
viability is crucial for guiding treatment decisions in patients with
STEMI. The improvement of RWMA contraction function after PCI is widely
regarded as the ”gold standard” for determining viable
myocardium[13].
It is important to note that this study had a small sample size and
focused solely on RWMA, which may have limited the detection of viable
myocardium in segments with normal wall motion. To enhance the study’s
validity and generalizability, it is recommended to expand the sample
size in future research. Additionally, the follow-up echocardiography
assessed improvement in wall motion compared to baseline, considering an
improvement of ≥1 grade as indicative of viable myocardium. However,
further analysis comparing improvements of ≥1 grade to improvements of
≥2 grades or more was not conducted due to the limited number of
eligible segments.
Future studies should consider including segments with normal wall
motion to avoid potential underdiagnosis of viable myocardium.
Additionally, exploring more comprehensive criteria for assessing viable
myocardium, such as improvements of ≥2 grades or more, could provide
further insights into the extent of functional recovery. These
considerations would contribute to a more comprehensive understanding of
myocardial viability assessment and its implications for clinical
decision-making.
STE can track the movement of the myocardeum by recognizing the
echo-speckle signal of the myocardeum in the image. This technology can
evaluate the myocardial segmental strain from multiple directions
without angle dependence, and can evaluate the local or global
myocardial function changes . The research showed that longitudinal peak
strain decreased during the acute phase and LS increased after
contraction in patients with ST segment elevation myocardial infarction.
It was concluded that the best indexes for evaluating transmural
infarction in cardiac myotameric segments were longitudinal peak strain
and post-systolic LS, with truncation values of -13% (AUC=0.86) and 8%
(AUC=0.84), respectively, and these two indexes could well predict the
improvement of myocardial function 6 months
later[14]. Meanwhile, some scholars have applied
three-dimensional speckle tracking imaging to evaluate the viable
myocardium of myocardial infarction patients, and found that the cutoff
value, sensitivity, and specificity of segmental radial strain detection
for survival myocardium were 11.1%, 0.951, and 0.534, respectively. The
cutoff value, sensitivity, and specificity of LS were 14.3%, 0.652, and
0.657, respectively. The cutoff value, sensitivity, and specificity of
area strain were 23.2%, 0.915, and 0.828, respectively. Among them, the
sensitivity and specificity of area strain were
higher[15]. However, the current frame rate of 3D
strain imaging is still not high enough, and some useful information may
be lost.
LDDSE is currently internationally recognized as the standard method for
detecting the reserve of viable myocardial contractile function. The
improvement of RWMA segments in resting echocardiography after LDDSE
indicates the presence of viable myocardium in that segment. Dobutamine
(dobu) is a synthetic catecholamine, which has a relative excitatory
effect on β1 receptor, but a weak excitatory effect on β2 receptor and α
receptor. Small dose of dobu(≤10 ug/kg/min) mainly excitates β1
receptor, has little effect on blood pressure and heart rate, enhances
myocardial contractility and induces myocardial ischemia, which has
important value in evaluating myocardial survival. In 1997, the using of
LDDSE to detect myocardial viability in patients with acute myocardial
infarction has been reported to have objective sensitivity and
accuracy[16].
The development of imaging technology has provided an important method
for evaluating the viable myocardium of myocardial infarction patients.
Currently, there are many methods available, and combined with clinical
research, a single method has limited diagnostic value. Therefore,
clinical practice is gradually inclined towards joint diagnostic
evaluation. Both of these methods are non-invasive and highly feasible
methods for detecting viable myocardial muscle. The sensitivity,
specificity and accuracy of SET-LDDSE were significantly improved
compared with the resting state. Studies have demonstrated that STE is
accurate, reliable, and reproducible, with little intra-observer and
inter-observer variation. Compare the diagnostic results with the ”gold
standard”, the study results showed that STE-LDDSE had great value in
the diagnostic accuracy, specificity and sensitivity of viable
myocardium in patients with myocardial infarction, suggesting that
STE-LDDSE should be the first choice in the evaluation of viable
myocardium in patients with myocardial infarction.
In summary, compared to traditional and single examination methods,
STE-LDDSE has higher sensitivity, specificity, and accuracy, which is
more helpful in guiding patients to effectively evaluate viable
myocardium before PCI, and has a certain guiding role in blood vessel
reconstruction and prognosis.