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Chapter 3. New Method of Patient Selection for Coronary Angiography and
Surgical Treatment of Coronary Artery Disease
3.1 Introduction
Stress testing is the main method of selecting patients for coronary angiography
and revascularization [90, 41]. Determining the tactics of managing each patient
with suspected or proven coronary artery disease (CAD) requires an idea of the
coronary bed condition: the presence of fixed heart artery obstructions and the
degree of change in the function of such arteries. Anatomical and functional data
of changes in the coronary arteries are complementary. It is known that 50-90%
arterial lumen stenosis, according to coronary angiography, is not an indication for
myocardial revascularization without proven dysfunction of this vessel with
functional tests. [133] Even experienced X-ray endovascular surgeons, without
functional information, cannot accurately determine the significance of most
stenoses only on the basis of a visual assessment of coronary angiography. This
approach is optimal for improving patient prognosis, which has been proven in
prospective studies and meta-analyses [41, 42, 90].
However, the most commonly used functional tests – tests with physical activity –
are impossible in a number of patients, for example, those with issues of the
musculoskeletal system, elderly patients, people with obliterating diseases of the
vessels of the lower extremities, etc. It is also known that among the entire cohort
of people who are physically able to perform a stress test, up to 27% do not reach
the required stress level, which qualitatively reduces the prognostic and diagnostic
value of this method. [83] In such cases, world practice provides for the use of
pharmacological stress tests. However, the risk of severe complications during
such tests increases five to tenfold. For example, when conducting dipiridamol or
adenosine tests, myocardial infarction/death is observed in 1:500-1:1,000 cases.
[116]
Inaccurate topical diagnosis of the lesion is also one of the disadvantages of
functional methods based on visual assessment only. It is not always possible to
152
assume which particular coronary artery dysfunction leads to impaired
contractility a certain segment of the left ventricular wall. This is due to the cross
blood supply to the myocardium by arteries of different basins, the dominance of
several branches of a single basin in a certain segment of the left ventricular wall,
and individual features of the coronary artery anatomy.
Coronary artery ultrasound during transthoracic echocardiography makes it
possible to assess changes in the parameters of coronary blood flow in a specific
area of the heart artery. At the same time, the method does not imply the
myocardial ischemia induction, as well as the use of potentially dangerous
pharmacological agents. Previously, studies have demonstrated the possibility of
ultrasound diagnosis of the coronary bed narrowing using changes in the coronary
blood flow velocities. However, these studies did not consider the relationship
between the data of altered blood flow in the coronary artery at rest and functional
disorders of regional contractility of the left ventricle during stress
echocardiography with load. It also remains unclear whether the data of coronary
blood flow ultrasound can refer patients to invasive diagnostic methods without
undergoing a functional stress test.
3.2 Purpose of the research
Thus, the purpose of this part of the research was to determine the relationship
between the coronary blood flow velocity at rest and impaired left ventricular
contractile function during exercise, to select patients for coronary angiography
and revascularization surgery.
3.3 Materials and methods
Two hundred and twelve patients were screened for stress echocardiography from
November 2014 to March 2015. The criterion for was a good visualization of the
left main artery, as well as the proximal and middle portions of the left anterior
descending artery. The exclusion criterion was a previous coronary artery bypass
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153
surgery.
The final study group consisted of 150 patients (48 patients from the original group
had suboptimal artery visualization, and 22 persons had undergone coronary artery
bypass surgery) [140]. Patients had a normal distribution by age given in Figure
3.1.
Fig. 3.1. Distribution by age
Clinical characteristics of patients are given in Table 3.1.
Table 3.1. Baseline characteristics of the study group (n=150)
Age (years)
56.6±10.6
HR, beats/min
70.7±11.7
Sex (M/F)
76/74
BMI (kg/m2)
28.8±4.2
Medical history
Hypertension
89 (59%)
Previous CAD
61 (41%)
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Previous PCI
29 (19%)
Diabetes mellitus
7 (5%)
Previous MI
39 (26%)
BMI, body mass index; CAD, coronary artery disease; PCI, percutaneous coronary
intervention; HR, heart rate; MI, myocardial infarction.
Examination report.
All patients underwent echocardiographic examination supplemented by
ultrasound measurements of coronary blood flow parameters. Then all patients
underwent stress echocardiography on a horizontal bicycle ergometer. All
echocardiographic images were digitally saved for further analysis. The methods
are described in Chapter 2. All coronary blood flow studies were evaluated and
analyzed by an anonymous imaging specialist, and the results of stress tests were
not known to the researcher. The contractility of the left ventricle segments was
analyzed twice: first during stress echocardiography, and then based on digital
clips by an independent expert without information about the clinical pattern and
the coronary blood flow examination results.
3.4 Results
Exercise test. Feasibility of LM/LAD/LCx scanning.
The scanning of coronary arteries in the above mentioned views took 8 min on
average. During screening of patients for the study, we calculated the rate of
visualization LM/LAD/LCx. The complete imaging of the LM/pLAD/mLAD was
achieved in 89%, 85%, and 92% of the patients, respectively. However, acquiring
spectral waves and measuring velocity in proximal and middle portions of LCx
artery was feasible only in 67% of patients.
Comparison groups with negative and positive tests
The main characteristics of the groups with negative and positive stress
echocardiographic tests are presented in Table 3.2.
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Table 3.2. Characteristics of the groups with positive and negative stress
echocardiography by visual assessment.
Positive
Negative
P value
N=87
N=63
Age (years)
60±09
53±11
<0.0001
Sex (M/F)
46/41
30/33
NS
BMI (kg/m2)
29±4
28±4
0.028
Echocardiography
IMM (g/m2)
76±16
70±12
<0.01
EF, %
61±10
65±05
<0.01
EDV, ml
76±16
96±22
0.06
Exercise test
Maximal HR (beats/min)
112±19
142±16
<0.0001
Exercise capacity (W)
75±28
134±42
<0.0001
Maximum blood pressure,
mmHg
167±29
196±26
<0.0001
EF at the peak (%)
55±14
73±06
<0.0001
Coronary artery velocity at rest
Max velocity in LM/proximal
LAD
67±36
42±15
<0.0001
Max velocity in middle LAD
46±30
36±15
0.024
Max velocity in LCx
59±27
33±12
0.022
BMI, body mass index; IMM, index of myocardial mass; EF, ejection fraction;
EDV, end diastolic volume; HR, heart rate; LM, left main artery; LAD, left
anterior descending artery; LCx, left circumflex artery.
Correlation between coronary artery parameters at rest and echocardiographic
exercise test data
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There was a significant positive correlation between the value of the maximum
velocity in the LM/pLAD and the end diastolic volume of the left ventricle at rest
(r ≈ 0.20, p = 0.024). There was no significant correlation between velocity and
ejection fraction. A higher degree of correlation was observed between the value of
the maximum velocity in the LM/pLAD and a positive stress echocardiographic
test (r≈0.35, p<0.0001); as well as the value of the maximum velocity in the
LM/pLAD and the ejection fraction at the peak of the load (r≈-0.39, p<0.0001), Fig.
3.2; the value of the maximum velocity in the LM/pLAD and index of wall motion
abnormalities (IWMA) at the peak of the load (r≈0.44, p<0.0001), Fig. 3.3; and
the value of the maximum velocity in the LM/pLAD and ΔIWMA (r≈0.41, p<0.01).
A significant correlation was observed between the value of the maximum velocity
in LCx and a positive test (r ≈ 0.66, p <0.01); the value of the maximum velocity in
LCx and the ejection fraction at the peak of the load (r ≈ -0.57, p <0.01); the value
of the maximum velocity in LCx and IWMA at the peak of the load (r ≈ 0.56, p
<0.01); and the value of the maximum velocity in LCx and ΔIWMA (r ≈ 0.51, p
<0.01).
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Fig. 3.2. Correlation between the maximum velocity in the LM/pLAD and ejection
fraction at the peak of exercise.
LM/pLAD – Left main coronary artery/proximal left anterior descending artery.
Sensitivity, specificity, positive predictive value (PPV), and negative predictive
value (NPV) of ≥0.70 m/s flow velocity in LM/pLAD/pLCx with regard to a
positive stress test were 26%, 98%, 97%, and 49%, respectively. Sensitivity,
specificity, PPV, and NPV of ≥0.70 m/s flow velocity in any portions of
LM/LAD/LCx with regard to a positive stress test were 30%, 97%, 93%, and 50%,
respectively.
Fig. 3.3. Correlation between the maximum velocity in the LM/pLAD and index of
wall motion abnormalities at the peak of exercise.
LM/pLAD – Left main coronary artery/proximal left anterior descending artery.
Groups with a flow velocity of ≥0.70 m/s
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There were 24 persons with a flow velocity of ≥0.70 m/s. They accounted for 16%
(95%, CI 11-22%) of all tests performed in the study. Ninety-six percent of these
tests were considered ischemic tests with a high risk of adverse cardiovascular
events. Twelve people (50%) had established atherosclerosis of the coronary
arteries, 12 (50%) had a differential diagnosis. Fifteen patients (63%) had no
history of myocardial infarction. Seven people with myocardial infarction had mild
IWMA at rest (1.1-1.5), one patient had moderate IWMA (1.8), and one patient
had severe IWMA (2.5).
With most patients (63%), the exercise test was stopped due to significant
worsening of left ventricle contraction with a decrease in the left ventricular
ejection fraction. In this group, exercise tolerance was low – 67±26 W, tests lasted
127±99 seconds, and the average heart rate was 111±19 beats/min.
Differences between groups with velocities ≥0.70 m/s and <0.70 m/s in LM,
proximal LAD and LCx are given in Table 3.3.
Table 3.3. Stress echocardiography data for groups with velocities of ≥0.70 m/s
and <0.70 m/s in LM, proximal LAD and LCx.
Velocity in LM, proximal LAD and
LCx
P value
≥0.70 m/s
<0.70 m/s
N=24
N=126
Maximal HR
(beats/min)
111±19
127±23
<0.01
Exercise capacity (W)
66±26
107±45
<0.01
Maximal blood
pressure, mmHg
174±33
180±31
Not
significant
EF at rest, %
61±09
63±09
Not
significant
EF at the peak (%)
54±16
64±14
<0.01
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IWMA at rest
1.31±0.51
1.12±0.30
Not
significant
IWMA at the peak
2.30±0.75
1.46±0.66
<0.0001
dIWMA
0.99±0.58
0.34±0.50
<0.0001
EF, ejection fraction; HR, heart rate; LM, left main artery; LAD, left anterior
descending artery; IWMA, index of wall motion abnormality; dIWMA, differences
of the index of wall motion abnormality at the peak and before exercise.
Fourteen patients had high velocities in the middle portions of their LAD or LCx,
and ten of them also had high velocities in pLAD. The data of echocardiography
and exercise data of four patients with high velocities visualized solely in the
middle segment of LAD (three patients) and LCx (one patient) did not significantly
differ from the patients in whom aliased coronary flow was not detected. Three of
the tests were deemed positive by ‘‘blind’’ assessment, in full agreement with the
first interpretation. Further analysis was not performed due to the small number of
this subgroup.
ROC analysis of coronary blood flow velocity parameters in relation to the stress
echocardiography result
The quantitative limit value of the coronary blood flow velocity in LM, which
determined a positive stress test according to the ROC analysis, was 44 cm/s,
sensitivity – 36%, specificity – 85%, area under the curve – 0.63, p<0.03, Fig. 3.4
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Fig 3.4 Prediction accuracy of positive stress echocardiography based on velocity
in LM
The quantitative limit value of the coronary blood flow velocity in pLAD, which
determined a positive stress test according to the ROC analysis, was 54 cm/s,
sensitivity – 58%, specificity – 84%, area under the curve – 0.74, p<0.0001, Fig.
3.5
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