Commentary on “Application of Apical Myocardial Perfusion Quantitative
Analysis by Contrast Enhanced Ultrasound utilizing High-Frequency Linear
Probe”
Liu Ruizhong MD
Department of Cardiology, the First Hospital of Harbin, Harbin, China
Keywords: Apical Myocardial Perfusion, Contrast-Enhanced Ultrasound,
High-Frequency Linear Probe Microvascular Perfusion
A Commentary on
Application of Apical Myocardial Perfusion Quantitative Analysis by
Contrast Enhanced Ultrasound utilizing High-Frequency Linear Probe
by Ruohan Zhao et al
We are grateful to the authors for sharing the results of this very
precise and detailed analysis of the diagnostic performance of apical
myocardial perfusion by combining high-frequency linear probe and
contrast enhanced ultrasound (CEUS) for the detection of left anterior
descending artery (LAD) stenosis. there are many imaging modalities to
assess coronary artery stenosis. For example, invasive coronary
angiography, coronary computed tomography angiography (CCTA), myocardial
nuclear perfusion imaging, cardiac magnetic resonance (CMR)[1], it’s
crucial to choose the most appropriate imaging modality for diagnosis,
treatment and procedural planning. In previous studies, the quantitative
analysis of myocardial perfusion by CEUS were based on 17-segment model
to assess the stenosis of the relevant vessels[2], it is relatively
cumbersome to perform. Since most of the apical LV is supplied by LAD,
the authors quantitative analysis of myocardial blood flow in the apical
LV to evaluate the stenosis of the LAD vessels by combining
high-frequency linear probe and CEUS, overcoming insufficient near-field
resolution and artifacts by the conventional phased-array probe. The
authors found that it is feasible and convenient to to assess apical
perfusion to reflect LAD stenosis by combining high-frequency linear
probe and CEUS with high Area under the curve of β, T, A, and MBF
(0.880, 0.881, 0.761, and 0.880 respectively). And the best cut-off of
β, T, A, and MBF were 10.32, 3.28, 9.39, and 4.99 respectively. What is
more, compared with phased-array probe, the quantitative analysis of
high-frequency linear probe is of high reproducibility and could get
good curve fitting (R2=0.29 vs. R2=0.71, P<0.01). We acknowledge
the precise nature of the work. However, we would like to raise some
points that may be worthwhile considering.
- This study enrolled 91 patients who complained about chest pain,
clinical diagnoses include angina, unstable angina and myocardial
infarction, the criminal artery was LAD, which confirmed by invasive
coronary angiography. To my opoin, the apical myocardial perfusion
could be affected by other factors, such as the site and degree of LAD
stenosis, distal blood flow and whether acute occlusion of LAD,
chronic occlusion with or without collateral circulation[3]. Thus,
it may question the accuracy of evaluating apical myocardial perfusion
to address LAD stenosis. Previous study demonstrated that Quantitative
intravenous MCE has the potential to estimate physiologic severity of
the LAD stenosis in the clinical setting by comparing the results with
those of exercise thallium-201 single-photon emission computed
tomography (SPECT), according to redistribution in the LAD territories
with SPECT or not, which elimination of the effects of the above
factors[4]. With this in mind, it could be better if group with
LAD stenosis manifest as LAD fixed stenosis without collateral
circulation and other coronary artery stenosis. Thus, the apical
myocardial perfusion may have close relation with LAD stenosis, which
can optimize design solutions to eliminate impact bias of apical
myocardial perfusion.
- In this study, High-Frequency Linear Probe was used creatively to
assess myocardial blood flow in the apical region of the heart, which
improved the quality of the images and the accuracy of the
analysis[5]. However, due to the limitations of the High-Frequency
Linear Probe, it is not capable of assessing myocardial blood flow in
other cardiac segments. And, in actual clinical practice, we do not
know what the patient’s crime vessel is, and blindly assessing
myocardial blood flow in the apical region alone has some limitations
for clinical guidance. It greatly limits its clinical application for
the management of patients with suspected or known other coronary
artery disease (CAD).
- However, it may add potential value for the quantitatively assessment
of microvascular perfusion (MVP) for myocardial infarction in patients
with anterior wall myocardial infarction[6]. For patients with
extensive anterior wall myocardial infarction, the infarct-related
artery (IRA) is LAD, early reperfusion therapy of IRA by percutaneous
coronary intervention (PCI) was done within the time window,
restoration of vessel patency in major epicardial arteries, but,
perfusion to the distal coronary microvasculature is not fully resored
as consequence of impairment of MVP[7, 8]. high-frequency line
probe combined with CEUS were used to assess the apical myocardial
blood flow of anterior wall myocardial infarction patients after PCI,
which is used to evaluate whether the MVP of the patients recover or
not after the infarct-related artery is opened[9]. So, it can be a
more sensitive and precise alternative method to distinguish impaired
MVP patients after PCI. Therefore, promptly addressing it can
significantly improve patient prognosis. So, it is promising to assess
the microvascular perfusion of anterior wall myocardial infarction
patients by high-frequency line probe combined with CEUS when
successful PCI is achieved.
- Although, this study demonstrate that observation of apical perfusion
is feasible and quantitative analysis allows an accurate and
convenient identification of LAD stenosis, this study did not evaluate
outcome prediction nor risk stratification. In order to recommend this
method as a diagnostic test to identification of LAD stenosis, further
comparative studies on risk stratification, management and
cost-effectiveness need to be demonstrated.
AUTHOR CONTRIBUTIONS
All authors listed have made a substantial, direct and intellectual
contribution to the work and approved it for publication.
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