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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4048_Библиотеки_им_академика_М_И_Перельмана
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Fig 3.5 Prediction accuracy of positive stress echocardiography based on velocity
in pLAD
The quantitative limit value of the coronary blood flow velocity in pLCx, which
determined a positive stress test according to the ROC analysis, was 35 cm/s,
sensitivity – 92%, specificity – 71%, area under the curve – 0.9, p<0.0001, Fig. 3.6
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Fig 3.5 Prediction accuracy of positive stress echocardiography based on velocity
in pLCx
3.5 Discussion
In the present study, we found a significant correlation between echocardiography,
exercise test data, and rest coronary blood flow velocities in two main coronary
arteries. A velocity of ≥0.70 m/s in LM and proximal portions of LAD/ LCx had
high specificity and prognostic value for positive stress tests, due to the direct
relationship between high local coronary flow velocity and ischemia in the zones
supplied by this artery.
The blood flow velocities in the coronary artery at rest correlated better with
hemodynamic data during exercise than with the same at rest. This evidenced the
possibility of detecting coronary artery dysfunction at rest using transthoracic
ultrasound, which, in turn, may be a reliable precursor of impaired contractility of
the left ventricular myocardial walls associated with functional changes in blood
flow in these vessels.
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Among the sequential group of patients with proven or suspected coronary artery
disease, referred to stress echocardiography, 16% (95%, CI 11-22%) had a blood
flow velocity higher than 0.70 m/s in LM and proximal LAD and LCx before
exercise. These patients then underwent an exercise test. All of their results were
positive and were considered severe according to echocardiographic criteria.
Consequently, coronary angiography was recommended for all of these patients.
During physical exercise in this group, the average IWMA was 2.3. The sensitivity
of research data to all positive ischemic tests was low. This is due to the inability to
visualize all segments of all coronary arteries at this stage of ultrasound
development. Therefore, alterations in small coronary arteries (diagonal arteries,
septal branches, obtuse marginal arteries, etc.), as well as stenoses of the right
coronary artery, could lead to ischemia and, accordingly, to a positive stress test
with normal coronary blood flow in proximal LM.
Thus, ultrasound of LM, LAD, and LCx at rest cannot replace stress
echocardiography in all patients. However, when registering high velocities of
coronary blood flow in LM, proximal LAD and LCx at rest in patients, it is
inappropriate to provoke ischemia during exercise tests, knowing that, with a
probability of 96-100%, the test will have a severe positive result. As is known,
severe complications during stress tests can occur just in patients with lesions of
the proximal regions of the coronary basin. Considering that a severe positive
stress echocardiographic test is an indication for invasive diagnostics, the resulting
data make it possible to recommend direct coronary angiography without stress
tests in this category of patients.
Therefore, while coronary blood flow ultrasound is not a substitute for stress
echocardiography, it can identify high-risk patients in a safer way without the
added risk of provocative testing. It will also save resources by reducing the
number of stress echocardiography tests made by about 16%.
In conclusion, ultrasonography of coronary blood flow at rest in LM and proximal
LCx can predict extensive ischemia during stress echocardiography. A significant
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correlation was observed between the value of the maximum velocity in these
portions of the arteries and the results of stress echo tests.
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165
Chapter 4. Comparing the Data of the Coronary Angiography and
Non-Invasive Measurement of Heart Artery Blood Flow Velocities
4.1 Introduction
Several recent studies have shown the possibility of diagnosing significant
narrowing of the coronary arteries without exercise testing, measuring coronary
blood flow velocities, as well as determining the ratio of velocities at the stenosis
site and upstream it [8, 63, 139, 4, 54, 56, 71, 91, 112, 74]. These studies showed a
high specificity of the coronary blood flow velocity at the stenosis site, as well as
when the ratio of velocities is greater than 2. Despite a number of studies
comparing the narrowing of the coronary arteries and the coronary bed ultrasound,
there is still no consensus on the limit values of coronary blood flow velocities
indicating a significant lesion. In addition, all previous studies involved cohorts of
patients with past indications for coronary angiography.
4.2 Purpose of the research
Comparing the coronary artery ultrasound results with the coronary angiography
data. Identifying the criteria for the coronary blood flow ultrasound, which are
indications for coronary angiography.
4.3 Materials and methods
This part of the work sequentially included patients from the general cohort of all
patients referred for routine echocardiography supplemented by transthoracic
ultrasound of the coronary arteries – see Chapter 2. The final analysis included a
group of 100 consecutive patients with determined indications for coronary
angiography.
The following scheme was used to compare the data of non-invasive and invasive
coronary studies: Fig. 4.1
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Fig. 4.1. Scheme of the coronary bed evaluation regions. 1-LMCA and LAD
ostium, 2-pLAD, 3-bifurcation of LAD/DA, 4-mLAD, 5-pLCx and mLCx
Coronary blood flow velocities were measured in the above segments according to
Scheme 4.1.
Coronary angiography was made by independent specialists in X-ray endovascular
surgery. The coronary angiograms were analyzed by one specialist who was not
informed about the clinical, functional data and non-invasive parameters of
coronary blood flow. Artery stenosis was determined visually as a percentage in
the worst projection, according to the recommendations of the European Society of
Cardiology.
The data was compared after independent measurement of the velocities in the
coronary blood flow ultrasound and evaluation of the percentage of narrowing by
coronary angiography segment by segment, according to the scheme in Fig. 4.1.
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167
4.4 Results
The average age of patients in the main group was 62±11, including 53 men and 47
women.
4.4.1 Correlation analysis
The 253 segments of the left coronary artery were juxtaposed side to side. A
significant positive correlation was determined between the coronary blood flow
velocities according to ultrasound data and the percentage of coronary artery
stenosis in the corresponding segment – R=0.52; p<0.0000001. Fig. 4.2.
The correlation between blood flow velocity and percentage of stenosis in LM was
R=0.40; p<0.02; at the LAD ostium, the correlation between the blood flow
velocity and the percentage of stenosis was R=0.49; p<0.0005; in the middle
proximal LAD – R=0.58; p<0.00001, Fig. 4.3; in the point of bifurcation with the
first diagonal artery – R=0.44; p<0.005; in the middle LAD – R=0.34; p<0.009; in
the proximal LCx – R=0.47; p<0.05.
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Fig. 4.2 Correlation between coronary blood flow velocities and the percentage of
the stenosis segment.
Fig. 4.3 Correlation between coronary blood flow velocities in proximal LAD and
the percentage of the stenosis segment.
4.4.2 Determining limit value, ROC analysis
The limit value blood flow velocity in LM for visual detecting of ≥50% stenosis
was 67 cm/s. Sensitivity was 69%, specificity – 89%, accuracy – 79%, p<0.0004.
Fig. 4.4.
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Fig. 4.4. Accuracy of detecting ≥50% stenosis in LM.
The limit value blood flow velocity at the LAD ostium for visual detecting of
≥50% stenosis was 77 cm/s. Sensitivity was 57%, specificity – 88%, accuracy –
70%, p<0.02. Fig. 4.5.
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Fig. 4.5. Accuracy of detecting ≥50% stenosis at the LAD ostium.
The limit value blood flow velocity in the middle proximal LAD segment for
visual detecting of ≥50% stenosis was 70 cm/s. Sensitivity was 62%, specificity –
88%, accuracy – 82%, p<0.0001. Fig. 4.6.
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