SHAPE Society

1. Morteza Naghavi MD,
Tania Khan, Babs Soller PhD, Peter Melling PhD,
Mohammad Madjid MD, Ward Casscells MD,
James T. Willerson MD
The University of Texas-HoustonTexas Heart Institute
Functional Evaluation of Atherosclerotic Functional Evaluation of Atherosclerotic
Plaque, Temperature, pH and Lactate Plaque, Temperature, pH and Lactate

2.  Casscells et al have previously
discovered that plaque temperature
correlates with other markers of
vulnerability and that hot plaque may be
a vulnerable plaque
(The Lancet 1996)
Introduction:Introduction:

3. Plaque temperature correlates with number of
macrophages
but not with smooth muscle cells

5. Our ex-vivo findings have been recently
corroborated by others in-vivo, suggesting that
increased plaque temperature compared to
adjacent arterial wall correlates with patients’
clinical presentation. Stefanadis et al
1999

6. Why should vulnerable plaque be Why should vulnerable plaque be hothot??
Vulnerable plaque is inflamed
and inflammation generates
heat

7. What else can be found in a site ofWhat else can be found in a site of
inflammation?inflammation?
Increased metabolic rate namely increased oxygen
and glucose consumption
Free radical formation (ROS and RNS)
Hypoxia
?

8. pHpH
Extra-cellular low pH or acidic environment is
characteristic of an inflamed site
This is mainly because of massive lactate
formation resulted from increased metabolic
activity of inflammatory cells. These cells
normally do not find enough oxygen to burn
glucose therefore, go through anaerobic pathway
and generate a large a mount of lactate

9.  Atherosclerotic plaques are known to be hypoxic due
to:
- Increased oxygen consumption by macrophages
- Decreased oxygen diffusion through plaque fibrous
cap
Both result in anaerobic metabolism.
(Bjornheden et al 1987)
 Macrophages are also known to be metabolically very
active. For example the ATP consumption of every 2
activated macrophages equals to one isolated maximally
loaded cardiomyocyte.
Back to old literature:Back to old literature:

10. ……why plaque pH or lactate?why plaque pH or lactate?
When incubated with Ox-LDL, macrophages are
seen to reduce their environmental pH to as low
as 5.5. (De Vries et al 1998)
Macrophages oxidize LDL in both neutral and
acidic pH, but the LDL oxidation is more
pronounced in an acidic environment.
(Leake et al 1995)

11. What could be the significance ofWhat could be the significance of
an acidic plaque?an acidic plaque?
 Low pH can activate or increase activity of acidic
matrix digesting enzymes resulting in plaque softening,
weakening and rupture.
Others recently reported presence of acidic
enzymes in human atherosclerotic plaques
(Libby et all, 1998)

13. pH
9.00
8.88
8.75
8.63
8.50
8.38
8.25
8.13
8.00
7.88
7.75
7.63
7.50
7.38
7.25
7.13
7.00
6.88
6.75
6.63
Noofpointswiththesameph
140
120
100
80
60
40
20
0
pH Distribution in 48 Human Carotid Plaques
This histogram demonstrates distribution of pH measured in 858
points in 48 carotid plaques of 48 patients. A marked variation
ranging from 6.5 to 8.9 is seen.

14. PH
9.5
9.0
8.5
8.0
7.5
7.0
6.5
6.0
pH Heterogeneity Within and Between Plaques in 48 Human Carotid Specimens
Red box shows the middle quartiles, solid lines shows median, cross-bars show
pH range and circles represents extreme values. This graph shows a significant
pH variation within and between plaques. The variation within the plaque holds
the majority of the total variation.

15. Watanabe Rabbit Aorta
pH
9.5
9.0
8.5
8.0
7.5
7.0
6.5
6.0
5.5
pH Heterogeneity in 9 Watanabe Rabbit Aortas

16. 2220231717191026252428N =
11 human umbilical artery
pH
9.5
9.3
9.1
8.9
8.7
8.5
8.3
8.1
7.9
7.7
7.5
7.3
7.1
6.9
6.7
6.5
6.3
6.1
5.9
5.7
5.5
pH Heterogeneity in 11 Human Umbilical Arteries

17. calcified&thrombosedLipid Rich
pH
9.0
8.5
8.0
7.5
7.0
6.5
pH in Lipid Rich Yellow Areas vs. Calcified areas
Areas with large lipid core exhibit higher temperature and lower pH
p < 0.01

18. Lipid Rich Yellow Areas (A and B) vs. Calcified Areas (C and D)
Lipid core
Calcification
H&E Movat

19. Correlation of pH and Temperature in Human Carotid Plaques Varied by the Areas
We see a marked inverse correlation between temperature and pH of
plaques that varies by macroscopic characteristics of plaques.
p < 0.01

20. Correlation of ph and Temperature in 9 Watanabe Rabbit Aorta
A significant inverse correlation between temperature and pH
is seen these rabbits similar to human carotid plaques
A significant inverse correlation between temperature and pH
is seen these rabbits similar to human carotid plaques
p < 0.01

21. Correlation of pH and Temperature in 11 Human Umbilical Arteries
In contrast to human and rabbit plaques in human umbilical there
is no relationship seen between temperature and pH
p = 0.2

22. Fluorescence Ratio (dual emission) Imaging Microscopy of A
Predominantly Calcified Plaque Shows Significant Microscopic
pH Heterogeneity with Higher pH in Calcified Areas

23. Fluorescence Single-Emission Imaging Microscopy
of a Predominantly Lipid Rich Plaque Shows
Significant Microscopic pH Heterogeneity Mostly
Acidic

24. What else, besides Temp and pH?What else, besides Temp and pH?
Oxidized lipid and proteins
– Ox-LDL
– Ox-collagen
Nitrated proteins
– Nitrosyl hemoglobin
– Nitrosyl tyrosine
?

25. How to measure
Temperature, pH
and the other factors
in plaque invivo?