New techniques for the “invasive diagnosis” of the vulnerable plaque

New techniques for theNew techniques for the“invasive diagnosis” “invasive diagnosis”

of the vulnerable plaqueof the vulnerable plaque

Antwerp, 17 March 2006

“Invasive” diagnosis “Non-invasive” diagnosis Biomarkers

Coagulation factors

Platelets

History

Stress/ViabilityTests

Vulnerable plaques (or high-risk plaques or thrombosis-

prone plaques):

– Thin- cap fibro-atheroma:

65% of all vulnerable plaques,

lipid core >40% of total plaque,

fibrous cap <100 μm.

– Erosion: 30% of all vulnerable plaques,

erosion/loss of dysfunctional endothelium.

– Calcific nodule: 5% of all vulnerable plaques.

DEFINITIONS

Normal Coronary artery

Asymptomatic atherosclerosis

Vulnerable plaques

During decades can develop

Plaques that develop thrombosis

Can progress, in an unpredictable way, to

Can conduct to

Acute coronary syndromes

Stenosis progression and stable angina symptoms

Asymptomatic progression

During years can lead to

NO RELATIONSHIP

BETWEEN STENOSIS SEVERITY

AND VULNERABILITY

““Standard” techniquesStandard” techniquesCoronary angiography

““Standard” techniquesStandard” techniquesCoronary angiography

Coronary angiographyAngiographically complex plaques:

- Contrast present outside the lumen borders (ulceration)

- Irregular and undermined borders (plaque rupture)

- Intracoronary filling defect (thrombosis)

Issues:

- Visualization of the coronary lumen only

- Often these plaques are already “flow-limiting”

- Complex plaques = vulnerable plaques already at advanced stage!

““Standard” techniquesStandard” techniques

Around 70% of acute coronary

occlusions occurs in

angiographically “normal” areas

IVUS““Standard” techniquesStandard” techniques

Axial resolution: 150 μm Lateral resolution: 300 μm

Morphologic data on the plaques

Echogenicityecho-lucent plaques echo-dense plaques shadow behind calcium

Discrete sensitivity (70%) ed high specificity (90%) for calcifications

Low sensitivity (50%) e specificity (30%) for lipid “core”

No information regarding fibrous cap (low resolution!!)

IVUS““Standard” techniquesStandard” techniques

The majority of available data comes from retrospective studies in patients with known CAD.

In UA patients as compared to SA patients:– The presence of ruptured plaques is more frequent– There are plaques with larger echo-lucent areas– There is more frequently a positive “remodeling”

IVUS““Standard” techniquesStandard” techniques

Several studies have shown

the presence of multiple

plaque ruptures in the

coronary tree,

and most of them were

ASYMTOMATIC!

VIRTUAL HISTOLOGYVIRTUAL HISTOLOGY

Amplitude ee Frequencyare used

to reconstructthe image

UnstableAngina

Recent myocardial

infarction

Stable Angina

Pull-back

ELASTOGRAPHYELASTOGRAPHY

PALPOGRAPHYPALPOGRAPHY

Diffuse and severeconcentric

calcification

Other techniques…Other techniques…Optical Coherence Tomography (OCT)

Measures the intensity of reflected light, as IVUS measures ultrasounds

Quality: - high resolution (20 μm)

Defects: - Bulky devices with very large diameter - need for “removal” of blood (occlusive balloon proximal or continuos flushing with water)

Fibrous Tissue = “signal-rich” Calcium = “signal-poor” with well defined contours

Lipid Tissue = “signal-poor”with hazy contours

EndoluminalThrombosis

Other techniques…Other techniques…Thermography

- Measures the difference in temperaure between a “baseline” area and a “region of interest”

- Index of the inflammatory status of the atherosclerotic plaque

-Most clinical studies performed to date only in one center (Greece)

- “Cool-down” effect of blood

Other techniques…Other techniques…Thermography

A glimpse into the future… Absence of a reliable animal model of vulnerable

plaque

Need for prospective studies (PROSPECT, VIP)

Pan-coronary inflammation syndrome

“Push” from pharmaceutical companies and interventional cardiologists

Every technique offers data on one aspect of the vulnerable plaque more techniques togheter?

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