espessamento medio intimal carótidal trials
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Carotid IMT as a Surrogate of
Cardiovascular Disease Risk
Allen J. Taylor MDCOL, Medical CorpsProfessor of Medicine, USUHSChief, Cardiology ServiceWalter Reed Army Medical
Center
What Is IMT ?
IMT is the distance between the lumen-intima interface and the media-adventitia interface
First described by Pignoli et al when imaging, with ultrasound, the wall of the abdominal aorta
Pignoli et al. Circulation. 1986;74:1399
Ultrasound Image of the Aorta in Vitro
near wall
far wall
Media-adventitia Interface
Lumen-Intima Interface
B-Mode Image of theCarotid Artery Wall
5 mm5 mmcarotid artery wall
plaque
Courtesy of W. Riley
mediamedia
adventitiaadventitia
intimaintima
plaqueplaque
What is Carotid Intima–Media Thickness (CIMT)?
Common Carotid
Internal CarotidExternal Carotid
FlowDivider
10 mm
Internal
10 mm
10 mm
Bifurcation
Common
Normal and DiseasedNormal and DiseasedArterial HistologyArterial Histology
Normal and DiseasedNormal and DiseasedArterial HistologyArterial Histology
SkinSurface
Portable Ultrasound for CIMT
•B mode ultrasound:•Frequency: broadband
•Newest device 13 MHz•Device cost: $40K +
•Specific advantages•Clinical
•Noninvasive•No radiation exposure•No incidental findings
•Research•Scalable•Low entry costs for multicenter investigations•Understood by clinicians
Carotid Intima-media Thickness
•Far wall•Acoustic shadowing in near wall
•Which site?
•CCA most reproducible
•ICA/Bulb: more difficult
•Plaque more common
•Greater magnitude of change
•Measurement
•ABD or manual, 1cm length
•Easy- takes minutes
•Accurate- .0x mm
Mean CIMT 1.174 mm
BulbLumen
Far wall IMT
Selection of end-diastolic images
Systolic expansion/IMT thinning
CIMT to Detect Atherosclerosis
and CV Risk
CIMT and Outcomes: Meta-analysis
Circulation. 2007;115:459-467
•Meta-analysis based on random effects models
•The age- and sex-adjusted overall estimates of the relative risk of myocardial infarction was 1.15 (95% CI, 1.12 to 1.17) per 0.10-mm common carotid artery IMT difference.
•The relationship between IMT and risk was nonlinear, but the linear models fitted relatively well for moderate to high IMT values.
1 2 3 4 50
10
20
30
40
4.8
12.8 1
6
21.2
29
6.2
10.4
16.1 2
0.6
29
5.6
12.2
18.1
19.5
28
Combined IMTCCA IMTICA IMT
Quintiles of IMTInci
den
ce R
ate
s (1
00
0 p
ers
on
-years
)
The Cardiovascular Health StudyIMT and Outcomes
• Relationship to CV prognosis:
O’Leary. NEJM 1999:340:14
•4476 pts, 65yrs+
•Risk-factor adjusted data
•MAXIMAL IMT
•CIMT and MI/stroke:
•Absolute risk exceeds 2% at 1.06 mm
•Risk is continuous:
•RR 1.27 per 0.2 mm of CIMT increase
•Pooled gender
•6698 adults aged 45 to 84 years •23 735 person-years of follow-up•222 incident CVD events (159 CHD events)•59 stroke events•50% had detectable CAC•1.07 mm for max internal CIMT•0.87 mm for max common CIMT
Arch Intern Med. 2008;168(12):1333-1339
Am J Cardiol. 2008 January 15; 101(2): 186–192
•CAC and CCA-IMT had similar hazard ratios for total cardiovascular disease and coronary heart disease. The CCA-IMT was more strongly related to stroke than was CAC
0
1%
2%
3%
4%
0 1% 2% 3%
Iden
tity
Iden
tity
Line
Line
Initial Event Probability (%)
4%
Post-
test
Even
tP
rob
ab
ilit
y (
%)
Low Middle High
• Focus: Intermediate risk group
• Greatest likelihood of therapeutic impact
• Use imaging to select for treatments guided by evidence based medicine
CHD equivale
nt
An abnormal imaging study should meaningful shift upwards a patient’s predicted CHD risk
IMT as a marker of “vascular age”
83 patients– Mean age 55– ARIC data used
to adjust age• Mean
vascular age 65
15% (1 in 7) reclassified to higher risk– Intermediate
risk patients• 5/14 to high
risk• 2/14 to low
risk
Black
White
Stein et al., University of Wisconsin- Presented
35.7%
14.3%0.0%
20.0%
40.0%
Reclassification rates
To high risk To low risk
Prevention V GuidelinesCirculation 2000;101:e3-22
•Secondary prevention guidelines:
•Known CAD, and…
•CAD-equivalents: DM, ASPVD, Plaque burden
•Plaque burden measurement techniques:
•ABI, Carotid IMT
•EBCT, MRI
Behavioral change: Potential within factorial trials
• Lausanne, Switzerland
• Randomized trial in smokers
• N=153
• Counseling ± imaging
• Smokers with plaque present and shown their images were 6-fold more likely to quit smoking
• Absolute 22.2% quit rate
• NNT 6
0%
5%
10%
15%
20%
25%
6 month quit rate
Control
No plaque
Plaque
Bovet. Prev Cardiol 2002;34:215
Progression of CIMT
Atherosclerosis: a progressive disease
“Typical” IMT:– Baseline- 0.60 to 1.00 mm– Typical progression rates .01 mm/year
Interventions affect the rate of progression of atherosclerosis This is measurable with carotid IMT
– Variability- protocol dependent• Site• Frequency of measurement• Image quality• Image interpretation
− Reader− Methods
Progressive Improvements in Imaging
5 MHz: 19958 MHz: 199910 MHz: 1999
Baldassarre et al. Baldassarre et al. StrokeStroke. 2000;31:1104. 2000;31:1104
Ab
solu
te D
iffe
ren
ces
Ab
solu
te D
iffe
ren
ces
Bet
wee
n R
epli
cate
Sca
ns
Bet
wee
n R
epli
cate
Sca
ns
0.20.2
0.150.15
0.10.1
0.050.05
00
0.130.13
0.10.1 0.090.090.080.08
0.060.06 0.060.060.040.04 0.040.04
0.0270.027 0.0220.022 0.020.02 0.0120.012 0.0070.007
ReferenceReference
Perss
on 9
2
Perss
on 9
2
Bal
dass
arre
Bal
dass
arre
(ana
log
syst
em)
(ana
log
syst
em)
Bal
dass
arre
Balda
ssar
re (d
igita
l sys
tem
)
(dig
ital s
yste
m)
Rile
y 92
Rile
y 92
O’L
eary
91
O’L
eary
91
Toub
oul
92 (s
tand
ard)
Toub
oul
92 (s
tand
ard)
Salon
en 9
1
Salon
en 9
1
Toub
oul 9
2 (s
oftw
are)
Toub
oul 9
2 (s
oftw
are)
Selze
r 94
Selze
r 94
Wen
delh
ag 9
7 (M
anua
l M
etho
d)
Wen
delh
ag 9
7 (M
anua
l M
etho
d)
Wen
delh
ag 9
7
Wen
delh
ag 9
7
(aut
omat
ed M
etho
d)
(aut
omat
ed M
etho
d)
Smild
e 97
(lef
t & ri
ght)
Smild
e 97
(lef
t & ri
ght)
Gar
iepy
93
Gar
iepy
93
IMT and Progression of Atherosclerosis
Sources of variability for Sources of variability for measuring changes in measuring changes in IMT progressionIMT progression
Proposed solutionsProposed solutions– ReplicatesReplicates– Increase time intervalIncrease time interval
Implicit solutionImplicit solution– Increase sample sizeIncrease sample size
Espeland et al. Espeland et al. StrokeStroke. 1996;27:480. 1996;27:480
0.0070.007
0.0060.006
0.0050.005
0.0040.004
0.0030.003
0.0020.002
0.0010.001
0.0000.000SingleSingle DuplicateDuplicate SingleSingle DuplicateDuplicate SingleSingle DuplicateDuplicate SingleSingle DuplicateDuplicate
2 years2 years 3 years3 years 6 years6 years 8 years8 years
Var
ianc
e of
Mea
sure
d P
rogr
essi
on R
ate
Var
ianc
e of
Mea
sure
d P
rogr
essi
on R
ate ReadersReaders NoiseNoise SubjectsSubjects
IMT Variability: Improving signal:noise
Present Protocol
•13 MHz
•ECG gated, diastolic images
•Common carotid
•2 views
•2 full sets
•Analysis
•Single observer, masked
•Manual and ABD
•All measurements performed twice on each image set
•Mean CC IMT, Max CC IMT
CIMT Progression Rate: Marker of Increased Risk for Events
Secondary Prevention, Men, Colestipol/Niacin vs Placebo: CLAS
Demonstrated value of changes in CIMT as an intermediate endpoint
Showed that rate of common CIMT progression was directly associated with higher risk for future MI and CHD death
Hodis HN et al. Ann Intern Med 1998;128:262-269.
0
1
2
3
CH
D R
isk
1
1.6
2.3
2.8P< 0.001
<0.011 mm/y
0.018–0.033 mm/y
0.0011–0.017 mm/y
>0.033 mm/y
Carotid IMT…Modestly related to cardiovascular risk
factorsand Age (a surrogate of exposure
duration)
Carotid IMT- Broadly related to risk factors
Related to risk factors Relationship varies across
carotid segments Relationships modest
Junyent et al. ATVB 2006;26:1107Junyent et al. ATVB 2006;26:1107
CIMT Progression: Relationship to risk factors
Am J Epidemiol 2002;155:38–47.
CIMT progression associated with:-baseline or new diabetes-smoking-high density lipoprotein cholesterol-pulse pressure, new HTN-change in low density lipoprotein -change in triglycerides
age 45–64 years
n = 15,792
CIMT Progression: Relationship to risk factors
Am J Epidemiol 2002;155:38–47.
age 45–64 years
n = 15,792
DM (yes/no) 1.97 microns
Smoker 1.82 microns
HDL (17.1 mg/dL) -.59 microns
LDL (39.4 mg/dL) .22 microns
Triglycerices (90 mg/dL)
.43 microns
Systolic BP 19 mm Hg .36 microns
Therapeutics and IMT
•Lifestyle interventions- exercise, diet
•Lipid modifying agents-
•Binding resins, Niaspan, statins, CETPi
•Anti-hypertensives
•CCB’s, blockers
•Anti-diabetic agents
•Metformin, TZD’s, tight diabetic control
Torcetrapib/atorvastatin*Torcetrapib/atorvastatin*
Atorvastatin dose titrationAtorvastatin dose titrationTarget: LDL-C to CV risk goalTarget: LDL-C to CV risk goal
Atorvastatin*Atorvastatin*
SSCCRREEEENNIINNGG
B-mode USB-mode US B-mode US/6 monthsB-mode US/6 months
24-month double-blind treatment24-month double-blind treatment*Same as atorvastatin dose at end of titration period*Same as atorvastatin dose at end of titration period
RADIANCE 1: starts at 20 mg; no wash-out periodRADIANCE 1: starts at 20 mg; no wash-out periodRADIANCE 2: 4 week wash-out, 4RADIANCE 2: 4 week wash-out, 4––16 week titration16 week titration
Study Name Clinical Sites Patient Population NPrimary
End Point
RADIANCE 1PIs: J Kastelein, M Bots, W Riley
Core Labs: Julius Center; Wake Forest
~25 imaging sites; 8 countries (US, CAN, FRA, ITA, NL, FIN, CZ, S.AFR)
HeFH; eligible for statin treatment as per NCEP ATP III; no HDL-C criteria
907ΔIMT
(mm/year)
RADIANCE 2Mixed hyperlipidemia, TG >150 mg/dL; eligible for statin treatment as per NCEP ATP III; no HDL-C criteria
758ΔIMT
(mm/year)
Dose titration (mg): 10 20 40 80Dose titration (mg): 10 20 40 80
RR
RADIANCE 1 and 2: Carotid Imaging Program
Rating Atherosclerotic Disease change by Imaging with A New CETP inhibitor
Torcetrapib and CIMT
N Engl J Med 2007;356:1620-30.
Torcetrapib and CIMT
N Engl J Med 2007;356:1620-30.
Torcetrapib and CIMT: RADIANCE 2
?Net Biomarker Impact
Lancet 2007; 370: 153–60
•Systolic blood pressure increased by 6·6 mm Hg in the combined-treatment group and 1.5 mm Hg in the atorvastatin-only group (difference 5.4 mm Hg, 95% CI 4.3–6.4, p<0·0001).
ENHANCE: Effect of Simvastatin ENHANCE: Effect of Simvastatin with or without Ezetimibe on with or without Ezetimibe on
Carotid IMTCarotid IMT
N Engl J Med 2008;358:1431-43
Simva Simva + Ezetimibe
EzetimibeEzetimibe Licensed by the FDA in 2002 for
treatment of:– Hypercholesterolaemia– Homozygous sitosterolemia
ENHANCE: Effect of Simvastatin ENHANCE: Effect of Simvastatin with or without Ezetimibe on with or without Ezetimibe on
Carotid IMTCarotid IMT
Lipid and CIMT resultsLipid and CIMT results
Subgroup DataSubgroup Data
N Engl J Med 2008;358:1431-43
N Engl J Med 2008; 359:1343
•Hard ischemic events:NFMI, stroke, hospitalized USA, CV death
Placebo: 119/929- 12.8%Simva/ezetimibe: 102/944- 10.8%
Chi-square: P = .21
SEAS:15.6% RRR*63% LDL reduction
* NFMI, USA, Stroke, CV death
Limitation of CIMT
• Greater understanding of change in CIMT progression and outcomes would be useful
• Definitive outcomes testing remains necessary
• Early in vivo “probe” to athero-biologic potential
• One surrogate doesn’t have all the answers
• Surrogates exist in potentially complementary fashion
• ? BP and HDL with CETP
• Will not likely provide any data on adverse effects
Assessing IMT as a Biomarker
PRO
•Scalable, widely used
•Noninvasive, no incidental findings, predicts outcomes
•Quantitative relevance
•Atherosclerosis extent
•All atherosclerosis (not just a single component)
•Changes in IMT definitively linked to clinical outcomes
•Broad track record of success in clinical trials
•Modifiable with wide range of therapeutic interventions
CON
•Geared for groups of patients vs. individuals
•Segmental response (CCA vs. ICA; IT vs. MT) may vary
•Requires quality imaging protocols to ensure inter-test variability is low enough to detect changes in IMT across reasonable time horizons
•Trials utilizing IMT not likely to identify adverse effects
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