Palpographyfor

Vulnerable Plaque Detection

Mortality

60 - 80% of all myocardial infarctions are caused by

ruptured vulnerable plaques

Constantinides P 1966;J Atheroscler Res, 6, 1

Schaar et al.EHJ 2004

What is a Vulnerable Plaque

Thin Cap Fibroatheroma (TCFA)

• Different tissues deform in a different way

• Deformation of tissue changes the ultrasound signals (rf-signals)

Principle of IVUS palpography

Echosignals of deformed tissue A B C D

DAB

DC’D’ DCD

DCD

DA’B’<DAB

C’ D’A’ B’

DAB - DA’B’

Soft Hard

undeformed

deformed

SOFT

HARD

Sensitivity and Specificityin vitro

Elastogrampositive

Elastogramnegative

Histologypositive

20 3 23

Histologynegative

4 27 31

24 30 54

Sensitivity = 88%Specificity = 89%

Schaar JA, et al. Circulation 2003

Smooth muscle cells

heavymediumminornone

Str

ain

(%)

Sensitivity and SpecificityRelation between strain and tissue components

p < 0.006p < 0.0001

3.0

2.5

2.0

1.5

1.0

.5

0.0

Macrophages

Str

ain

(%)

1312326n =

3,0

2,5

2,0

1,5

1,0

,5

0,0

heavymediumminornone

Schaar JA, et al. Circulation 2003

0

0,5

1

1,5

2

2,5

3

0 100 200 300 400 500 600 700

Cap Thickness in um

Str

ain

(%

)Sensitivity and SpecificityInverse relation between strain and cap thickness

y = 236/xR2 = 0.68p < 0.0001

Based on:Loree HM, et al. Circ Res 1992; 71: 850 - 8 Schaar JA, et al. Circulation 2003

Sensitivity and Specificityin vitro

Schaar JA, et al. Circulation 2003

=

100 μmcapthickness

Schaar et al, Eur Heart J 2003, Herz 2005

1%

0 %Angle

Depth

3 D Palpography

Previous Current

Previous Current

Interpretation

Grades (ROC) Strain (%)

I 0.0 – 0.6

II 0.6 – 0.9

III 0.9 – 1.2

IV > 1.2

ROtterdam Classification (ROC)

Symptomstable unstable post MI

Hig

h S

trai

n S

pots

0.0

0.5

1.0

1.5

2.0

2.5

3.0

p = n.s.p < 0.001

p < 0.0001

In vivo incidence of high strain spotsSymptoms vs. number of high strain spots

n = 55 coronary arteries19 stable angina18 unstable angina18 post MI

Schaar et al, Circulation 2004

SEM

SD

Number of high strain spots

none one two three

CR

P µ

g/dL

0,0

0,5

1,0

1,5

2,0

2,5

3,0

In vivo incidence of high strain spotsRelation to CRP

R2 = 0.60

Schaar et al, Circulation 2004

ConclusionPalpography

• Vulnerable plaque in vitro

• High Strain spots in vivo correlate with symptoms and

inflammation markers

• Reproducible in vivo (animal, human)

• Follow up is possible (IBIS, IBIS II, PROSPECT)