RIGA STRADINS UNIVERSITY
Uldis Strazdiņš
INTRAOPERATIVE QUALITY CONTROL OF
MYOCARDIAL REVASCULARIZATION
Summary
Riga - 2006
Urgency of the Study
Every year the number of those who suffer from cardiac and vascular disorders
becomes higher. Over 50% of deaths in developed countries are associated with
cardiovascular diseases, but coronary heart disease (CHD) accounts for 1/3 of death
causes. About 7 million people in USA are suffering from symptomatic CHD; thereof
about 1.5 million have myocardial infarction (MI).
The situation in Latvia is far from favorable. The Central Statistics Bureau data
show that 55.7% of deaths were caused by cardiovascular disorders. 177 of 100 000
inhabitants under 64 y. o. die of CHD. Myocardial infarction, which is just one of the
manifestations of CHD, is found in 5000 patients every year [Gardovskis et al., 2001].
Taking into consideration both high incidences of CHD and high mortality figures
all over the world, including Latvia, we are to state that the CHD, including its
management and the results thereof, is a great medical and social challenge.
CHD management can be divided into three main lines: drug therapy; invasive
cardiology and surgical myocardial revascularization, which complement each other.
Every year about 1000 cardiac operations under cardiopulmonary bypass (CPB)
per 1 million inhabitants is done in USA, about 800 per 1 million is done in Europe
and 310 such operations were done under CPB per 1 million inhabitants in Latvia in
2005. Myocardial revascularization surgery remains the core part of the activity of
modern cardiac surgery centers: according to National database of Society of
Thoracic Surgeons (STS) in USA myocardial revascularizations account for 89.5% of
all of the cardiac operations. This kind of surgery draws more and more attention due
to its bigger proportion. In order to reduce surgical and CPB-induced trauma the miniinvasive surgery is introduced and successfully used during last decades, which is
done without CPB and via minimized approaches. This kind of surgery is highly
appreciated by patients, although it is associated with extra difficulties and stress for
operating surgeon, which may possibly result in lack of surgical quality.
The major problems, determining extended patient stay in a hospital, disability
and mortality after myocardial revascularization surgery are perioperative myocardial
infarction (PoMI) (directly associated with the quality of the bypass graft,
anastomosis and extent of the surgery), cerebral ischaemia, wound complications and
bleeding. Incidence of PoMI as a cause of mortality during primary coronary artery
bypass grafting (CABG) accounts for 1 - 10.3% [Grover et al, 1996; BARI
investigation, 1996]. The incidence of PoMI varies between cardiac surgery Centers
and depends to a great extent on the definition of PoMI, still remaining the major
cause of death in myocardial revascularization surgery operation group.
During last decades, when the development of mini-invasive surgery emerged all
over the world, specific attention has been drawn to the evaluation of quality of
CABG. More and more new quality evaluation methods are being introduced in
cardiac surgery practice every year, often borrowed from other medical fields
[Reuthebuch et al., 2004]. "Old" techniques are updated; also different combinations
of methods are offered, as well as algorithms of use thereof [Jaber et al., 1998;
D'Ancona et al., 2000; Sanisoglu et al., 2003].
We are to emphasize that intraoperative methods are emerging in particular,
because the correction of defects only found during primary surgery allows avoiding
life dangerous complications. Each of the methods has its own advantages, although
some drawbacks are to be mentioned as well, such as lack of rendered information,
difficult data interpretation and application technique, high costs of instruments and
procedures, patient health risk factors. It is asserted that cardiac surgery all over the
world has no unified approach to this issue.
PoMI is associated with longer postoperative care in Intensive Care Unit (1CU),
use of expensive assisting circulatory devices (intraaortic balloon pumping,
ventricular assisting devices, etc.), longer in-hospital stay, sometimes with necessity
of re-revascularization (invasive cardiology, CABG). This considerably impairs
quality of life and life expectancy of the patient.
Considering the above we can assume that intraoperative evaluation of the quality
of myocardial revascularization using different techniques requires more profound
study, which may contribute to improving outcome of cardiac surgery, quality of life
and life expectancy of the patient, reduce disability as well as patient care costs.
Goal of the study
To develop a technique to evaluate the quality of myocardial revascularization
surgery by measuring blood flow, using videoluminescence angiography and
videoendoscopy methods during the surgery.
Objectives of the study
1. To perform 60 prymary coronary artery bypass grafting operations.
2. To evaluate quality of operation by using floumetry, videoluminescence
angiography and videoendoscopy.
3. To perform statistical analysis of quality control effectivity.
4. To elobaruate methodical guidelines
Novelty of the study, its scientific and applied significance
Assesment of the quality of myocardial revascularization surgery draws higher
attention during last decades as the miniinvasive techniques are developing. When
analyzing one or the other technique the authors often do not try to combine those in
order to complement the drawbacks of one method with the advantages of the other.
There are no printed data available on unified approach to the evaluation of the
quality of myocardial revascularization surgery. Also, common algorithms of the
quality evaluation are not developed. In order to contribute to this issue this study
analyzes both approved techniques (blood flowmetry in grafts) and new ones, which
use in cardiac surgery is considered a novelty (videoluminescence angiography). Also
the study deals with the use of videoendoscopy technique, which is already developed
for cardiac surgery, still it is missing unified attitude as to its importance for cardiac
surgery applications. As the endoscopy equipment is being further developed, the
importance of the technique may increase.
The quality assessment methods were being studied in conjunction to each other,
using all of the techniques, available to us, in order to develop method of
intraoperative quality evaluation.
We hope to have our results implemented into daily practice of cardiac
surgery. By summarizing our findings and printed information we intend to develop
intraoperative technique of assessment of quality of myocardial revascularization, as
well as to improve the outcome of myocardial revascularization surgery by decreasing
and avoiding such dangerous complications as PoMI.
Hypotheses to be defended
1. Blood flowmetry, videoluminescence angiography and videoendoscopy can by
used for the detection of perioperative complications.
2. Intraoperative evaluation of quality helps to improve postoperative period.
3. There is statistically reliable correlation between the results of the used tests
and intraoperative complications.
Design and scope of the study
The promotional thesis is written in Latvian. It comprises 12 chapters:
Introduction, Urgency of the study, Posing a problem, Goal of the study, Novelty and
practical aplication, Description of patients and examination technique, Statistics,
Results, Conclusions, Discussion, Recommendations and Bibliography. Overall size
of the thesis is 102 pages, including 1 diagram, 21 charts, 12 tables and 17 figures.
Bibliography list includes 158 publications.
Aprobation of the study
The promotional thesis was orally presented at 5 international scientific
congresses and conferences. The thesis was presented once at RSU Medical scientific
conference and twice at Paula Stradina University Hospital in Physicians' Scientific
meetings. 18 articles are published in internationally referred medical journals. The
list of publications - see end of the summary.
Matherial
Description of the patients
The study was performed within Cardiac Surgery Center of SJSC Paula
Stradina Clinical University Hospital from year 1999 till 2005. The study was
approved by ethics committee on human research of Riga Stradins University.
Videoendoscopy, videoluminescence angiography and blood flowmetry methods were
used.
Videoendoscopies. 58 grafts asessed in 18 patients 48 to 76 years old (mean
age of 60 in this group), thereof 33% were female patients and 67% - male patients.
Only 22% of the patients had no preoperative history of MI. 88% of the patients had
stable exercise angina. Patients had 3 to 4 grafts created, with the mean of 3.22
grafts per patient. In four cases arterial grafts were used (thereof 3 of internal thoracic
artery, ITA, and one radial artery). In all of the cases the ITA graft was
anastomosed with Left Anterior Descending (LAD) coronary artery, while radial
artery - with diagonal branch of left coronary trunk (RD). Mortality rate was 0%.
Videoluminescence angiography. 92 angiograms were analyzed in 46
patients 39 to 78 years old (mean age of 63 years), thereof 30 male patients (65%)
and 16 female patients (35%). 17.4 % of the patients had no preoperative history of
MI. 10.9 % of all of the patients had unstable angina, the rest had stable exercise
angina. In one case the myocardial revascularization surgery was done by
sternotomy OPCAB, in all of the rest cases - by CABG. 1 to 4 grafts were created.
43 patients in this group (93.48%) underwent just revascularization, 3 patients
(6.52%) had combined surgery, there of 2 had CABG with aortic valve
replacement and 1 had CABG combined with left ventricular thrombectomy at
open left ventricle. All of the patients survived, the mortality rate is 0%.
According to the goal of the study and hypotheses to be defended, we divided
the patients into two groups:
Group A - patients with critical stenoses (>90%) and occlusions of major
coronary arteries, supplying left ventricle;
Croup B - patients with hemodynamically significant stenoses (<90%) of
major coronary arteries, supplying left ventricle (see Table 1).
Table 1. Videoluminescence angiography patient breakdown by groups.
Group A
N
Group B
31
15
57,87
69,4
Unstable angina (%)
6,45
20
No history of MI (%)
9,68
33,33
Mean N of grafts
3,16
3,47
Mean age (yr)
Arterial grafts
26 (83,87%)
11 (73,33%)
All of the videoluminescence and videoendoscopy group’s patients had blood
flow measured (207 measurements).
Methods Flowmetry
Blood flowmetry in grafts was measured by transit time ultrasound flowmeter
by Medi-Stim, BF-2000 in all of the patients. Measurements were taken before
stopping CPB, at normothermy, in order to avoid inaccurate measurements, caused by
hypothermia-induced spasm of arterial grafts and coronary arteries.
The ultrasound transducer was soaked in autologous blood or saline at 37°C in
order to provide better contact with the graft (Fig. 2).
BF 2000 automatically calculated the mean blood flow, which was recorded in
examination log. The PI was calculated as follows:
PI 
V max  V min
;
Vmean
where Vmax is maximum or systolic flow, Vmin is minimum or diastolic
flow, Vmean is calculated mean blood flow. The Vmax and Vmin values were
measured by blood flow curve on the monitor. The derived PI variable was recorded
in the examination log.
Fig. 2. Example of flowmetry with indicated Vmax, Vmin and Vmean,
necessary for PI calculation
Videoluminescence angiography
Videoluminescence angiography was done by IC-VIEW (PULSION Medical
Systems AG) system. Indocyanine green was used as a luminescent dye - ICGPULSION (PULSION Medical Systems AG).
Intraoperative videoluminescence angiography was done in each of the patients
before and after the myocardial revascularization under CPB. The first measurement
was taken after start of CPB at blood temperature of 36°C. Then coronary and central
graft anastomoses were created. The second measurement was taken after connecting
the grafts to the myocardial blood supply. Measurements were taken at blood
temperature ≥ 36°C to avoid hypothermia-induced vsacular reactions. We used
Medtronic DLP elevating mesh to position the heart. Pateints undergoing OPCAB
surgery were examined before and after revascularization at stable hemodynamic
status. The operation field shading was achieved by non-transparent curtains in the OR
(Fig. 3).
Fig. 3 General diagram of videoluminescence angiography
ABCDEFG-
videocamera to sense the luminescence, double light filter (Lambda = 780nm);
Computer to display the course of angiography;
Toens laser;
ICG-PULSION syringe;
Blood serum al lipoproteins;
ICG-PULSION introduced into blood stream;
ICG-protein complex luminesceing under laser light.
Fig. 4. Heart positioning during videoluminescence angiography. Left patient before revascularization; right - patient after connecting grafts to
myocardial blood supply.
ABCDEFG-
Heart elevating mesh;
Left ventricle with CHD-induced impaired myocardial blood supply;
LAD;
Base of right ventricle with intact circulation;
Control syringe with dye;
ITA graft to LAD;
Autovenous graft to distal segment of right coronary artery (RCA).
Videocamera was equipped with laser light source and light filters and placed
above the operation field. The computer was connected to a camera. The dose of
ICG-PULSION was calculated per weight of the patient (0.3 mg/kg). After CPB
was over, the heart was luxated to allow the videocamera visualize left ventricle
and the base of right ventricle (Fig. 4).
To set the starting point of luminescence intensity measurement we
prepared the control syringe (1ml ICG-PULSION mixed with 9 ml of autologous
blood) and placed it in the operation field. While the videocamera was in the
infrared mode, the laser was enabled and ICG-PULSION was injected via
cannula, placed in internal jugular vein. The exact time of the injection was taped
on the video. The monitor displayed the progress of the procedure, which
allowed evaluating myocardial circulation, as the intensity of luminescence is
directly proportional to the blood supply of heart muscle. It was possible to
visualize the course, size and constrictions of coronary arteries. The obtained
angiography data, entered into the computer and processed by IC-CALC
software, rendered us quantitative results, both in table and chart format,
regarding luminescence variations in different parts of myocardium
before and after revascularization (Fig. 5). Also, IC-CALC software allowed to
evaluate inverted colour luminescence image, which helped to visually analyze
myocardial circulation (Fig. 6).
Fig 5. Dynamics of luminescence (obtained by IC-CALC). Upper figure before revascularization; lower figure - the same patient after connecting grafts
to myocardial blood supply.
ABCD-
Start of intravenous injectuion of ICG-PULSION;
Luminescence control curve (control syringe);
Luminescence dynamics in the base of right ventricle after injecting ICG;
Luminescence dynamics in the left ventricle after injecting ICG.
Fig. 6. Inverted luminescence image (obtained by IC-CALC)
Left - blood supply defects in left ventricle before revascularization compared to the
base of right ventricle. Right - the same patient after revascularization with
normalmyocardial blood supply.
The following data, obtained using IC-CALC was analyzed (Fig. 7.):
- Maximum degree of luminescence (mean pixel intensity, relative units) of left
ventricle myocardium before (Y2) and after (Z2) revascularization;
- Maximum degree of luminescence (mean pixel intensity, relative units) of the base
of right ventricle with intact blood supply before (Y1) and after (Z1) revascularization;
- Percentage of the above variables before (X1) and after (X2) revascularization,
showing the intensity of luminescence of the left ventricle expressed in percents to
such of normally supplied myocardium;
- Time from injection ICG to its appearance in the respective parts of myocardium
before (T) and after (T') revascularization.
Considering that intensity of luminescence is directly proportional to
myocardial perfusion, but absolute values, of mean pixel intensity, vary individually
between patients, we analyzed just percentage ratio (hereinafter referred to as
perfusion alterations) between pre and postoperative status.
Fig 7. Analyzed variables.
- Y1
- Y2
-T r
-T 1
Maximum luminescence of the right ventricle;
Maximum luminescence of the left ventricle;
Time to dye appearance in right ventricle;
Time to dye appearance in left ventricle.
In all of the patients in postoperative period we:
- measured Trooping I (Tn1) in 8-16 hours postoperatively;
- analyzed 12-lead ECG on postop Day 1 or Day 2;
- monitored time (hours) from surgery completion to extubation;
- monitored duration (hours) of stay in ICU;
- monitored duration (days) of stay in surgery department;
- verified PoMI by increased Troponine I concentration (0,5 - 0,96 ng/ml) only if
accompanied with new Q-wave or changed "old" Q-wave on ECG.
Intraoperative videoendoscopy
Videoendoscopy of grafts, anastomoses and bypassed arteries was done during
aortic occlusion after creation of all of the coronary anastomoses. The endoscope and
saline supply line were introduced into graft via its proximal end. Then the graft was
occluded proximally by the finger of the assistant. While priming the graft and
coronary artery by saline, the endoscope was entered via graft to anastomosis, then
beyond the anastomosis, when possible, to coronary artery. The videoendoscopy
image could be watched on the monitor and recorded on a videotape (Fig 1). Taking
into account the calibers of the videoendoscope and the graft and in order to avoid
eventual damage of the graft we considered videoendoscopy impossible when internal
diameter of the graft was less than 2 mm. The endoscopy was performed with
Richard Wolf equipment, available at Cardiac Surgery center.
Fig. 1. General diagram of videoendoscopy.
ABCDEFG-
Flexible endoscope introduced into venous graft at LAD;
Syringe with saline to prime the graft;
Assisting finger to occlude the proximal end of the graft:
LAD;
Ascending aorta;
Autologous venous graft at LAD;
Graft anastomosis at LAD.
After the endoscopy procedure the aortic occlusion was released, central
anastomoses created, flowmetry done, CPB stopped and surgery completed. The
diameter of the artery to within 0.5 mm (measured by endovascular probes of
different caliber), the course of endoscopy procedure, flowmetry readings and
pulsation index (PI), duration of the procedure, complications, as well as defects and
elimination of such were recorder in examination log.
The course of endoscopy procedure was ranked to four groups:
0 - Endoscopy impossible (considering graft diameter)
1 - Endoscope reaches anastomosis, but cannot be passed beyond it
2 - Endoscope passes the anastomosis, but distal segment of the bypassed
artery cannot be visualized
3 - Both anastomosis and distal segment of the bypassed artery can be
visualized.
The duration of the endoscopy procedure was taken from the moment the
surgeon takes the endoscope till the moment of removal of the endoscope from the
last examined graft.
Graft, anastomosis or coronary artery visual defects were considered as
complications of the procedure.
Methods of statistical analysis
For blood flow velocity, PI, X, T and other variables analysis we used
descriptive statistics values, such as mean, standard deviation of the population, mean
value standard error, maximum error of confidence interval (usually p = 0.05), where
t is Student distribution or t-test, minimum and maximum values of variance,
dispersion profile, upper and lower limits of 95% confidence area (95% confidence
interval). Student r-test is derived when calculating the identity of mean values of the
two parameters. To calculate the identity of mean values of morphology criteria of
more than two parameters we used dispersion analysis (ANOVA - Analysis of
variance). Correlation of different variances of the population was evaluated using
Pearson correlation coefficient r. To find correlation between two parameters we used
also linear and non-linear regression methods.
The obtained data were processed by software applications SPSS 11.5, MS
Excel 2002 SP-1, CIA.
Results
Results of videoendoscopy
In all of the cases of internal thoracic artery (ITA) graft we did not use
videoendoscopy, as it was assumed to be traumatic and dangerous due to the diameter
of the graft. In cases where endoscopy was available we noticed that the progress of
procedure is directly associated with the diameter of lumen of bypassed artery (See
Chart 1.)
Chart 1. Progress of endoscopy procedure depending on the diameter of
lumen of bypassed artery.
Analysis of mean blood flow velocity and PI in endoscopy group of patients
showed statistically significant linear corelation between these two variables -increase
in blood flow velocity corresponded to decrease in PI (See Chart 2).
Grafting defects found by videoendoscopy were not statistically reliably
confirmed by flowmetry findings and PI calculations.
Pearson correlation analysis showed statistically significant correlation
between mean blood flow velocity in grafts, PI and the diameter of the bypassed artery
(Table 1).
Chart 2. Regression curve of PI dependence of mean blood flow velocity.
Table 1. Results of Pearson correlation calculations.
Statistical criteria
PI
Diameter of bypassed
artery
Pearson correlation
Significance
N
Pearson correlation
Significance
N
** Correlation is significant at p = 0.01 (2-sided).
* Correlation is significant at p = 0.05 (2-sided).
Mean blood
flow velocity
-,545(**)
,004
26
,529(**)
,006
-,418(*)
,033
26
26
PI
Results of videoluminescence angiography
Patients with PoMI were excluded from patient groups primary statistical
analysis to ensure uniformity of Groups A and B. Group A and Group B patients
with uneventful postoperative status were compared, Thereof 31 patient in Group
A and 15 patients in Group B. Group primary analysis was done for 29 patients in
Group A and for 12 patients in Group B.
Chart 3. Changes in left ventricle perfusion after revascularization.
We compared the changes of X1 and X2 in Group A and B patients by group
statistics method and found that baseline perfusion of the left ventricle in Group A
patients was 102,9 ± 5,2% (t=-3,8;p=0,01), while after revascularization it increased
up to 130,4 ± 3,1% (t=3,2; p=0,03); in Group B patients respective values were 136,7
± 5,9% and 112,6 ± 4,2%. Left ventricle perfusion in Group A statistically reliably
increased after revascularization, but decreased in Group B (Chart 3).
Analysis of perfusion difference (X2 - X1) showed it to be reliably positive
in Group A, 27,52 ± 3,5, but reliably negative in Group B -24,17 ± 3,3
(t=8,8;p=0,01) (Chart 4).
Time to dye appearance (T) in left ventricle and right ventricle myocardium
before and after revascularization was analyzed by group statistics methods (Table 2)
We found that T1 and T'1 times to dye appearance in myocardium with non-altered
blood supply are the same for both A and B Groups (p=0,01), T'2 time to dye
appearance in myocardium after myocardial revascularization in Groups A and B
shows statistically significant difference (t=-2,77;p=0,01). T2 time to dye
appearance in myocardium with altered blood supply before revascularization in
Groups A and B does not show statistically significant difference, which confirms
difference between Groups A and B when using videoluminescence method.
Chart 4. Perfusion augmentation after revascularization in Groups A and B.
Table 2. Analysis of time T by group statistics.
Groups
A and
B
A
B
Analyzed
value
Tl
T2
T'l
T'2
Tl
T2
T'l
T'2
N
29
12
Mean
Mean Standard
standard
value (s) deviation
error
26,55
34,59
25,79
22,55
34,67
30,33
31,58
27,08
4,74
8,84
5,89
5,45
7,95
4,27
4,6
2,19
0,88
1,64
1,09
1,01
2.29
1,23
1,33
0,63
t
-4,06
1,58
-3,04
-2,77
-4,06
1,58
-3,04
-2,77
p
0,01
0,12
0,01
0,01
0,01
0,12
0,01
0,01
Analysis for group A
We analyzed 31 patients in Group A, thereof 2 patients (6.45%) had
postoperative PoMI. We analyzed the difference in myocardial perfusion percentage
ratio before and after revascularization in cases of CHD-altered and non-altered
myocardium blood supply and found that Group A had close and statistically
significant correlation between X1 and X2 - X1 difference (r = 0,848; p = 0,01). The
correlation between X1 and X2 - X1 difference can be described by the following
linear regression equation:
X2 -X1 (%) = 91,29 - 0,63 × X1(%).
Determination coefficient of linear regression model is r2 = 0,72. Constant of
equation and independent variable are significant with p = 0,01 (Chart 5).
Chart 5. The linear regression of changes in myocardial perfusion in Group A
patients.
Patients with PoMI after revascularization had decreased left ventricle
myocardial perfusion and the difference in percentage ratio became negative, which
made distinct and statistically significant difference with other Group A patients,
who had positive difference in percentage ratio.
Analysis of T2 un T'2 times, indicating the velocity of dye supply to left
ventricle before and after the revascularization showed that in PoMI patients
No 11 and No 15 the T'2 time exceeded T2 (Chart 6). It is an indicator of altered
blood supply in myocardium.
Chart 6. Changes in T 2 - T'2 before and after revascularization in Group A
patients
When analyzing the difference in times of myocardium dyeing before and
after revascularization we found that in PoMI patients the difference becomes
negative and statistically significantly differs from other Group A patients
(Chart 7). T2 and the difference of T 2 -T'2 have close and statistically significant
correlation (r = 0,757; p = 0,01). The correlation between T2 and T2 -T'2 difference
can be described by the following linear regression equation:
T2 -T'2(s) = -14,79 + 0,75 × T2(s).
Determination coefficient of linear regression model is r2 = 0.57. Constant of
equation and independent variable are significant with p = 0,01.
To prove that PoMI impacts such significant medical criteria as duration of
mechanical lung ventilation (MLV), duration of stay in ICU (hours), total duration of
in-hospital care after the surgery, we analyzed these parameters by descriptive
statistics for Group A patients (no-PoMI) (Table 3).
Chart 7. The linear regression of changes in left ventricle dyeing time for
Group A patients.
Table 3. Results of descriptive statistical analysis of Group A patients (noPoMI).
Hours in
ICU
Hours to extubation
In-hospital days
postop
N
Minimum
Maximum
Mean
Standard error
29
15
76
34,5
3,9
29
3
12
5,5
0,4
29
7
25
11,5
0,7
Standard deviation
20,9
2,4
3,6
Patients with PoMI had considerably longer ICU stay - 123 and 138 hours
compared to the upper limit of mean value in the Group - 97.2 hours (34.5 + 20.9 ×3
=97,2). We did not find that PoMI considerably influences durations of MLV and
postoperative in-hospital treatment.
Analysis for group B
We analyzed 15 patients in Group B, thereof 3 patients (20%) had early
postoperative PoMI. We analyzed the difference in myocardial perfusion percentage
ratio before and after revascularization in cases of CHD-altered and non-altered
myocardium blood supply and found that Group B had close and statistically
significant correlation between X1 and X2 - X1 difference (r = 0,813; p - 0,01). The
correlation between X1 and X2- X1 difference can be described by the following
linear regression equation:
X2 -X1 (%) = 38,47- 0,47 × X1(%).
Determination coefficient of linear regression model is r2 = 0.66. Constant of
equation and independent variable are significant with p = 0,01 (Chart 8).
Chart 8. the linear regression of changes in the left ventricle perfusion dyeing
time for GroupB patients.
In Group B patients with PoMI after revascularization we found decreased
perfusion of left ventricle, the percentage ratio difference became negative, which
made no statistically significant difference with other Group B patients.
Analysis of T2 un T'2 times, indicating the velocity of dye supply to left
ventricle before and after the revascularization showed that in Group B in PoMI
patients Nos 1, 4 and 10 the T'2 time considerably (at least for 5 sec) exceeded T2
time (Chart 9). We are to note that negative T changes in Group B were found also in
patients without PoMI (up to - 2 sec).
Chart 9. Changes in T2 - T'2 before and after revascularization in Group B
patients.
Analysis of the difference in times of myocardium dyeing before and after
revascularization revealed that in PoMI patients the difference becomes considerably
negative and statistically significantly differs from other Group B patients (Chart 10).
T2 and the difference of T2 -T'2 have close and statistically significant correlation (r =
0,791 ; p = 0,01). The correlation between T2 and T2 -T'2 difference can be described
by the following linear regression equation:
T2 -T'2(s) = -29,65 + 1,0 5 ×T2(s).
Determination coefficient of linear regression model is r2 = 0.63. Constant of
equation and independent variable are significant with p = 0,01.
In order to prove that PoMI impacts duration of mechanical lung ventilation
(MLV), duration of stay in ICU (hours), total duration of in-hospital care after the
surgery, we analyzed these parameters by descriptive statistics for Group A patients
(no-PoMI), (Table 4).
The results show us that only one of Group B patients with PoMI had longer
stay in ICU - 115 hours, which is considerably longer than the upper limit of mean
value in the Group - 95.8 hours (37.3 + 19.5 × 3 =95.8). For other patients we did not
find that PoMI considerably influences durations of MLV, ICU stay and postoperative
in-hospital treatment.\
Chart 10. The linear regression of changes in left venricle dyeing time for
Group B patients
Table 4. Results of descriptive statistical analysis of Group B patients (no-PoMI).
Hours in
ICU
12
19
91
37,3
5,6
19,5
N
Minimum
Maximum
Mean
Standard error
Standard deviation
Hours to extubation
12
3
17
7,5
1,2
4,1
In-hospital days
postop
12
8
19
12,1
0,9
3,0
Results of flowmetry
Mean blood flow velocity and PI analyses were done by group statistics
method (Table 5). All of the Group A and Group B patients were analyzed, grouping
the blood flow by respective arterues.
Mostly the LAD was bypassed. Blood flow velocity up to 21.5 ml/min was in
25% of patients, 27.5 ml/min - in 50 %; 39.5 ml/min - in 75%.
In 84.1% of cases we used ITA as a graft, in the rest of cases LAD was
bypassed by venous graft. The difference in blood flow velocity in arterial and venous
grafts had no statistically significant difference.
Table 5. Mean blood flow velocity anf PI in grafts.
Mean blood flow
velocity (ml/min)
LAD
RD
MO
Cx
RCA
PI
(relative units)
LAD
RD
MO
Cx
RCA
61
42
28
23
53
16
9
17
10
10
70
70
62
230
156
31,68
27,79
28,22
39,39
42,89
Standard
deviation
12,60
14,54
11,29
43,01
33,90
61
42
28
23
53
1
1
1
1
1
4,2
4,1
2,8
4,2
3,4
1,85
2,06
1,69
1,97
1,75
0,74
0,82
0,44
0,83
0,66
N
Minimum
Maximum
Mean value
It can be seen from Table 5 that blood flow velocity and PI in LAD grafts are
acceptable, though clinically all of the 5 PoMI developed exactly in left ventricle front
and lateral walls, supplied by LAD. Mean blood flow velocity in LAD patients
without PoMI was 33.13 ± 2.0 ml/min with PI of 1.64 ± 0.1. In PoMI group blood
flow velocity was 20.4 ± 2.2 ml/min with PI of 3.5 ± 0.3. Groups differ by blood flow
velocity with t - 2.22 and p = 0.03 (Table 6). Groups differ by PI with t = 8.79 and
p = 0.01.
Table 6. Group statistics for patient groups with (2) and without (1) PoMI.
(blood flow in ml/min; PI in relative units)
PoMI
Blood flow
LAD
RD
N
Mean
St.
deviation
St. mean
error
in 1
2
56
5
33,13
20,40
12,58
4,83
2,02
2,16
1
2
1
2
39
3
26
2
28,32
23,33
27,38
35,00
15,24
5,86
11,02
15,51
3,05
3,38
2,76
11,00
RCX
1
2
22
1
39,95
27,00
43,94
9,37
RCA
1
2
1
2
1
2
1
2
48
5
56
5
39
3
26
2
40,74
56,20
1,64
3,5
2,02
2,4
1,73
1,35
32,95
40,70
0,42
0,62
,84
0,61
0,43
0,50
5,92
18,20
0,07
0,27
0,17
0,36
0,11
0,35
RCX
1
2
22
1
1,92
3,00
0,82
RCA
1
2
48
5
1,81
1,40
0,69
0,33
MO
PI LAD
RD
MO
t
p
2,222
0,032
0,554
0,584
0,895
0,384
0,288
0,776
0,945
0,351
8,788
0,001
0,761
0,454
1,159
0,264
0,17
1,288
0,212
0,12
0,15
1,295
0,204
Analysis of mean blood flow velocity and corresponding PI in no-PoMI
patient group showed that there is statistically significant correlation between these
two variables. Least squares regression equation is as follows:
PI = 14,32 ×(blood flow velocity (ml/min))-0,63.
Correlation coefficient r is 0.73, which confirms close and confident (p =0.01)
correlation. We can see from determination coefficient (R2) that in this model the
53.2% deviation from the curve can be explained by dispersion of mean blood flow
velocity.
It is more difficult to make necessary calculations using non-linear regression
equation than using linear regression equation. It was necessary to logarithm the PI in
order to obtain linear regression equation (Chart 11).
Lg(PI) = -0,008 × (Blood How velocity (ml/min)) + 0,4899
Chart 11. Correlation between blood flow velocity and lg(PI) based on linear
regression analysis of the data and definition of power function.
Conclusions
1. Combination of videoluminescence angiography, blood flowmetry in grafts
and videoendoscopy renders complete image of quality of myocardial
revascularization, including information on created graft, anastomosis, distal
segment of coronary artery and overall myocardial blood supply. Use of these
techniques allows to detect grafting defect and reveal threatening MI.
2. The blood flow velocity measurements allowed to define the critical PI limit of
3.5 ± 0.27, exceeding of which results in PoMI and requires revision of graft.
3. Correlation between mean blood flow velocity and PI value in functional graft is
determined by linear correlation lg(PI)=-0,008 x (mean blood flow velocity
(ml/min)) + 0,4899, which can be used as a diagnostics criterium in case of
altered graft function.
4. Videoluminescence angiography findings are considerably variable in cases of
critical stenosis, occlusion and hemodynamically significant stenosis of
coronary arteries. The difference between groups should be taken into account
when analyzing quality of operation.
5. Videoluminescence angiography is applicable for detecting myocardial
perfusion complications during CABG operations. The following diagnostics
criteria for threatened MI can be used: alterations in left ventricle blood supply
and myocardial dyeing delay.
6. Videoendoscopy of grafts, anastomoses and coronary arteries renders valuable
information for intraoperative assessment of quality and can be used in
CABG, if the diameter of the graft is > 3 mm. This procedure is indicated in
all cases of unclear condition of distal segment of coronary artery (blind
coronary endarterectomy, occluded and calcified coronary artery).
RECOMMENDATIONS FOR PRACTICE
1. Videoendoscopy
of
grafts,
anastomoses
and
coronary
arteries
is
recommended for CABG if coronary arteries have diameter of more than 3
mm. Specific indications for videoendoscopy are:
- in blind coronary endarterectomy to evaluate the distal segment of coronary
artery;
- in case of occluded calcified coronary artery grafting, when preoperative
cocnarography and intraoperative visual and manual examination does not
provide sufficient information about periphery of the artery.
2. Blood flowmetry in grafts should be done at every CABG with simultaneous
analysis of mean velocity and PI, which can provide better information about graft
function. In our study we considered the PI value of ≥ 3,5 as critical, exceeding
of which requires revision of graft and anastomosis.
3. Algorhitm of flowmetry is proposed (Diagram 1).
4. Videoluminescence angiography is indicated in case of suspected graft
malfunction, the findings are to be evaluated visually.
5. Videoluminescence angiography as sensitive quality evaluation technique is
indicated at every CABG surgery. Specific indication could be evaluation of the
degree of myocardial revascularization in diffuse coronary sclerosis with multiple
coronary stenoses.
PUBLICATIONS
1. U.Strazdiņš, R.Lācis, J.Volkolakovs, A.Ozols, J.J.Volkolakovs. Infekcijas
endokardīta ķirurģiskā ārstēšana. RSU Zinātnisko rakstu krājums. 1999: 59 63.
2. R.Lācis, A.Alks, R.Kolītis, U.Strazdiņš, A.Avots, J.J.Volkolakovs, O.Kalējs,
I.Ozolanta, V.Volkovičs. Koronārās sirds slimības un to komplikāciju
ķirurģiskās ārstēšanas izpēte. RSU Zinātnisko rakstu krājums. 1999: 45 - 48.
3. A.Ozols, R.Lācis, J.Volkolakovs, U.Strazdiņš. Sirds vārstuļu protezēšanas
rezultāti. RSU Zinātnisko rakstu krājums. 1999: 55 - 58.
4. S.Thora, R.Lācis, R.Kolītis, U.Strazdiņš, M.Māliņa, N.Moorlate,
A.Dombrovskis. Artēriju kombinēto bojājumu ķirurģiska ārstēšana koronārās
sirds slimības pacientiem. RSU Zinātnisko rakstu krājums. 1999: 64 - 68.
5. U.Strazdiņš, R.Lācis, A.Avots, J.J.Volkolakovs, J.Pavārs, E.Strīķe.
Intraoperatīvā šuntu un anastamožu kvalitātes kontrole, pielietojot asins
plūsmas ātruma mērījumus un videoendoskopiju. RSU Zinātnisko rakstu
krājums. 2000: 116-118.
6. O.Kalējs, R.Lācis, J.Jirgensons, J.Ansabergs, M.Blumbergs, N.Nesterovičs,
U.Strazdiņš,
M.Sauka,
S.Sakne.
Atrioventrikulārā
savienojuma
radiofrekventā katetrablācija pēc mitrālā vārstuļa protezēšanas - pirmie attālie
rezultāti. RSU Zinātnisko rakstu krājums. 2000: 70 - 76.
7. R.Lācis, R.Kolītis, A.Avots, U.Strazdiņš, J.Volkolakovs, J.Pavārs, P.Stradiņš,
L.Feldmane. Arteriālie konduīti miokarda ķirurģiskajā revaskularizācijā. RSU
Zinātnisko rakstu krājums. 2000: 77 - 80.
8. J.J.Volkolakovs, U.Strazdiņš, R.Lācis. Mazinvazīva ķirurģiska miokarda
revaskularizācijā. RSU Zinātnisko rakstu krājums. 2000: 119 - 123.
9. E.Strīķe, N.Porīte, A.Avots, U.Strazdiņš, J.Volkolakovs, I.Vanags.
Nepārtrauktā neinvazīvā sirds izsviedes tilpuma mērīšana ar transezofageālo
ehodoplera sistēmu pacientiem sirds operācijas laikā. RSU Zinātnisko rakstu
krājums. 2001: 39-41.
10.R.Lācis, A.Alks, U.Strazdiņš, R.Kolītis, J.J.Volkolakovs, L.Feldmane,
A.Avots, V.Volkovičs. Sirds koronāro šuntu agrīnās trombozes novēršanas
izpēte. RSU Zinātnisko rakstu krājums. 2001: 23 - 26.
11.O.Kalējs, R.Lācis, A.Avots, N.Porīte, U.Strazdiņš, E.Strīķe, J.J.Volkolakovs,
S.Sakne. Dažādu pieeju efektivitāte ātriju fibrilācijas ārstēšanā ar katetrablācijas
metodi mitrālā vārstuļa ķirurģijā. RSU Zinātnisko rakstu krājums. 2001:54-62.
12.R.Lācis, P.Stradiņš, U.Strazdiņš, N.Porīte, V.Harlamovs, I.Putniņš,
R.Rozentāls, J.Bicāns, S.Truškovs, U.Kalniņš, A.Ērglis. Pirmā sirds
transplantācijas operācija Latvijā - P.Stradiņa klīniskajā universitātes slimnīcā
2002.gada 11.aprīlī. Acta Chirurgica Latviensis. 2002; 2: 61 - 64.
13.R.Lācis, P.Stradins, V.Kasyanov, A.Ozols, I.Ozolanta, B.Purina L.Feldmane,
U.Strazdins, I.Putnins. Bioprotheses for human heart valves. Acta Chirurgica
Latviensis. 2002; 2:3-1.
14.O.Kalejs, R.Lacis, U.Strazdins, N.Porite, A.Avots , E.Strike, J.Volkolakovs.
Radiofrequency Ablation in Treatment of Atrial Arrhythmias in Valvular Surgery.
Clinical Pacing and Electrophysiology 2003.: Monduzzi Editoriale//p.l43-147.
15.U.Strazdiņš, R.Lācis, J.Pavārs, E.Strīķe, J.J.Volkolakovs, E.Freilibs.
Intraoperatīva
miokarda
revaskularizācijas
kontrole,
pielietojot
videoluminiscences metodi (pirmā pieredze). RSU Zinātnisko rakstu krājums.
2003:207-212.
16.E.Strīķe, I.Vanags, R.Lācis, J.Volkolakovs, N.Porīte, U.Strazdiņš,
V.Harlamovs, O.Kalējs. Nepārtrauktās neinvazīvās un invazīvās sirds izsviedes
mērījumu metožu salīdzinājums koronārās šuntēšanas operācijās bez mākslīgās
asinsrites. RSU Zinātnisko rakstu krājums. 2003: 183 - 187.
17.J.Volkolakovs, R.Lācis, A.Alks, U.Strazdiņš, V.Harlamovs, E.Strīķe,
A.Avots, O.Kalējs. Tiešā ķirurģiskā miokarda revaskularizācija bez mākslīgās
asinsrites. RSU Zinātnisko rakstu krājums. 2003: 164 - 167.
18.E.Strīķe, I.Vanags, R.Lācis, N.Porīte, U.Strazdiņš, V.Harlamovs,
J.J.Volkolakovs. Sirds funkcijas un audu perfūzijas novērtējums pacientiem
sirds operācijās ar mākslīgo asinsriti un agrīnajā pēcoperācijas periodā. Latvijas
Ķirurģijas Žurnāls. 2004; 4: 18 - 21.