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.