4th vulnerable plaque symposium
TRANSCRIPT
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Plaque temperature heterogeneity is associated with
macrophage accumulation and metalloproteinase activity
R. Krams, LCA van Damme
Dept. Experimental Cardiology, Thoraxcenter, Rotterdam, The Netherlands
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Background
• Plaque rupture has been related to a high MMP activity and macrophage (Mø) accumulation
Galis et al, J. Clin. Invest. 1994
• Recently, regional temperature heterogeneity has been observed in atherosclerotic plaques in vivo
Verheye et al, Circulation 2002
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Aim of this study
• To test the hypothesis that temperature heterogeneity is associated not only with macrophage accumulation but also with MMP-activity in atherosclerotic plaques in vivo.
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MethodsIn 6 NZW rabbits:• Endothelium was removed (denudation) of the infra renal aorta
• 2 months 2% cholesterol diet
• Temperature measurement after 2 months of follow up
• Immunohistochemistry for the detection of mø (RAM11, Dako), smooth muscle cells (1A4), histology for collagen amount (picro-serious red) and lipid contents (oil red o) and MMP activity in a zymogram
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start
end
3F Fogarty
50 mm
Infra renalaorta
Renal artery
Denudation area
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Thermography
• Intravascular thermography
• Catheter: Thermocore Medical Systems
• Accuracy: ± 0.01 °C
• Pullback speed: 0.2 mm/sec
• Measurement of temperature difference from a reference area
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Analysis I
•Thermography with / without blood flow-pull back over 6 cm-mean of 4 thermistors-mean of 2 pull backs-reference area set at 0 °C
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Analysis II• Histological analysis:
-Mø % of plaque area-Lipid % of plaque
area-Collagen % of plaque
area-Smooth Muscle
Cell(SMC) % of plaque area
• Vulnerability Index (VI-index):
VI = Mø% + Lipid% Collagen% + SMC%
Shiomi et al, Atherosclerosis 2001
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Analysis III• MMP activity in a zymogram
-SDS PAGE gel electroforese
-separation on molecular weight
-substrate: gelatin
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ProtocolInducing atherosclerosis
Perform thermography after 2 months
Hot Cold
Isolate area Isolate area
MMP-activity / cel distribution MMP-activity / cel distribution
Compare
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Distance (mm) from renal artery
0 5 10 15 20 25 30 35 40 45 50 55
T (°
C) f
rom
refe
renc
e
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
T (°
C) f
rom
refe
renc
e
-0.2
-0.1
0.0
0.1
length (mm) vs Mean without blood flowlength (mm) vs Mean with blood flow
Results IThermograph (with and without blood flow)
Hot spot 1
Hot spot 2Cold area
Example 1
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Length from renal artery (mm)
0 5 10 15 20 25 30 35 40 45 50 55
T (°
C) f
rom
refe
renc
e ar
ea
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
T (°
C) f
rom
refe
renc
e ar
ea
-0.01
0.00
0.01
0.02
0.03
length (mm) vs Mean without blood flowlength (mm) vs Mean with blood flow
Example 2
Results IThermograph (with and without blood flow)
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T (°C) from reference
0.1 0.2 0.3 0.4 0.5 0.6 0.7
VI-i
ndex
0
1
2
3
VI-indexRegression between VI-index and T R=0.8, p=0.013
Results II
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Results II
T (°C) from reference
0.1 0.2 0.3 0.4 0.5 0.6 0.7
Mø
(%) i
n th
e pl
aque
0
5
10
15
20
25
30
møRegression between mø(%) and T (°C), R = 0.7 p = 0.020
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Results IIIMMP-9
Pro-MMP-2
MMP-2 active
MMP-9
Pro-MMP-2
MMP-2 active
MMP-9
Pro-MMP-2
MMP-2 active
Length (mm) from renal artery0 10 20 30 40 50 60
T (°
C) f
rom
refe
renc
e
0.00
0.25
0.50
0.75
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MMP2activeproMMP2 MMP9
MM
P a
ctiv
ity (p
ixel
s/m
m2 )
0
5000
10000
Hot regionsReference rgeions
*
*
* p<0.05
Results III
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Summary
• We found that temperature has a positive correlation between mø% and VI-index
• We found more pro-MMP2 and active MMP2 inside the hot area’s compared to the cold area’s
•We found almost no rise in temperature in presence of blood flow
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Conclusion I
• Temperature heterogeneity is associated with a VI-index
• The underlying mechanism of this association is mø accumulation
• The high MMP-activity suggests that active mø are detected by temperature changes
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Conclusion II• We have seen in our model that it is almost impossible to measure temperature differences in presence of blood flow
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Discussion
• Blood has a cooling effect on the vessel wall, and blood flow is high in the rabbit’s abdominal aorta (twice human coronary flow).
• Therefore to exclude a dominant flow effect on our measurements, we stopped the flow with a balloon
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Co-operation
• Catherization laboratoryProf. Dr. PW SerruysDr. W. van der Giessen
• Experimental Cardiology Rotterdam L.C.A van Damme
C. van PeltB. Mousavi GourabiW. MaatD. SegersC. ChengDr. R. KramsDr. D.J. Duncker
• Experimental Cardiology UtrechtDr. G. PasterkampC. SnijderA. Schoneveld
• Thermocore Medical SystemsDr. G. Van LangenhoveDr. T. FlintDr. Y. Yianni
• Middelheim Hospital AntwerpenS. Verheye
M. KockxM. Knaapen