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How to Measure
Arterial Function
2005.11.25
서울대학교병원
박진식
Arterial Function
• Endothelial function
• Conduit function
• Dampening function
Endothelial Function
• Vascular tone– Flow Mediated Dilatation
• Coagulation
system– Measuring soluble
markers
Conduit Function
• Ankle-Brachial Index (ABI),
Intima-Media Thickness (IMT)
• Impaired by occlusive lesions
– Atherosclerosis
– Medium sized conduit artery
– Coronary/Cerebral artery
Dampening Function
• Stiffness, Distensibility, Compliance
• Impaired by arterial stiffening
– Arteriosclerosis
– Large sized elastic artery
– Aorta/Carotid artery
Development of Arterial Dysfunction
Impaired Endothelial Function
Impaired Conduit Function
Impaired Dampening Function
How to Measure Arterial Function
• Non-Invasive Methods
Basic Principles
Clinical Implications
Comparison among the Methods
Endothelial Function
Brachial FMD
Endo-PAT
Flow Mediated Dilatation (FMD)
• Basic principles
– Endothelium dependent vasodilation
vs. endothelium independent vasodilationNeurotransmitter
Hormone
Shear Stress
Direct NO Donor
Baseline Measurement
Avascularization
Reactive Hyperemia
Shear Stress
NO release from Endothelium
Vasodilation
L-Arginine-Nitric Oxide Pathway
L-ArgeNOS
Shear Stress
Citrulline
NO
Endothelial
Cell
ROS
Agonist(Ach)
Extracellular
Space
Vascular
Lumen
ecSOD
NO
Peroxynitrite
Ca2+
sGC
GTP
cGMP Relaxation
Ca2+
Ca2+
++
+
+Smooth
Muscle
Cell
Brachial FMD
ameterBaselineDi
ameterBaselineDierPeakDiametFMD
)((%)
Healthy : 10-20%
Endo-PAT
A
C D
B
C
D
A
BPATindexRH
PAT vs. FMD-Correlation
PAT vs. FMD-Clinical Implications
Conduit Function
Ankle Brachial Index
Intima-Media Thickness
Ankle-Brachial Index
• Decreased in arterial
occlusive disease – ABI ≥ 1.0: normal
– ABI 0.8 - 1.0: mild occlusion
– ABI 0.5 - 0.8: moderate
occlusion
– ABI ≤ 0.5: severe occlusion
SBPHighestArm
AnkleSBPABI
Ankle-Brachial Index-ASx
Intima-Media Thickeness
• Carotid IMT • Brachial IMT
Dampening Function
Arterial StiffnessPulse wave velocity
Augmentation Index, Pulse pressure
SPCA, DPCA
Arterial Stiffness-Basic Principles
• Pulse wave travels faster through the stiffer artery.
proximal distalwave
reflection
soft/slow
stiff/fast
soft/slow
stiff/fast
PWV
Applanation Tomometry
• f(Peripheral wave form) ≈ Central wave form
– Generalized transfer function
Gender specific transfer function
– Estimation of
• Central BP
• Augmentation index(AIx) ( r=0.66 )
AoBA )( AoBA )(
Arterial Stiffness & CV Disease
↑ Central wave
Reflection
↑ Aortic stiffness
↑ Vascular endothelial damage
& Mechanical fatigue↑ PP
Atherosclerosis
- Stroke
- Myocardial Infarction
- Renal Failure
↑Myocardial O2 demand
↑LVH
↓Coronary perfusion
↑Myocardial O2 demand
↑LVH
↓Coronary perfusion- LVH and CHF
- Aneurysm formation
and rupture
Association of CV Risk Factors & APWV
7.14
8.38
7.67
8.7
8.03 8.11
8.59
9.72
8.89 8.89 8.72
9.389.74
8.87
5
10
Age(>60)
Male
DM
HTN
SBP>=140
Dyslip
SMK
P<0.0001 p=0.0026
p=0.0166
AP
WV
(m/s
ec)
p=0.0003
Association of APWV and CAD Severity
10.16
8.998.72
7.49
6
9
12
NL 1VD 2VD 3VD
AP
WV
(m/s
ec)
Vessel Score
Pulse wave velocity
• CV Risk factors ass with increased PWV– Increasing age / Hypercholesterolemia
– Type II diabetes / Sedentary lifestyle
• CAD and PWV in hypertensives– ↑ all cause mortality(OR = 1.34 / ↑5m/sec)
– ↑ CV mortality(OR = 1.51 / ↑5m/sec)
– ↑ mortality( PWV > 13m/sec)
• Progression of PWV– ↑ in Cr>8mg/dl
– Normotensive < Controlled HTN < HTN
• Reduction of PWV results in ↓ mortality in ESRF pt– RR of 0.71 for all cause mortality / ↓ 1m/sec PWV
Relating change in diameter (or area) of an
artery to distending pressure
• CV risk factors and Carotid Distensibility– Hypertensives vs Normotensives : CCA
• DistMAP: Hyper > Normo
• Dist100,Dist110 : Hyper = Normo
• Distending pressure alone is determinant
– Aging• ↑ age ↑Dist100
• structural change of arterial wall during aging process
– Dist using IVUS• Age, CHD, Hypertension, Hypercholesterolemia, Acutely after smoking ↓ Dist
– Dist using MRI• Age, diastolic HF ↓ Dist
• Clinical outcome and Carotid Distensibility– ↓ Dist of Carotid a. all cause mortality in ESRF pt
Systolic Pulse Contour Analysis(SPCA)
• CV risk factors and radial AIx
– AIx increased in old age, type I DM,
hypercholesterolemia
• Clinical outcome and Carotid AIx
– ↑ AIx ↓ exercise capacity in CHD pt
– ↑ AIx all-cause & CV mortality in ESRF pt
even in pt with normal PWV
(<11m/sec)
Diastolic Pulse Contour Analysis(DPCA)
• Two component of diastolic wave form
– C1(Large artery compliance) : exponential decay curve
– C2(Small artery compliance) : other component
• Marker for early vascular disease
• CV risk factors and DPCA
– ↓ C1 is ass with
• ↑ SBP
– ↓ C2 is ass with
• Type II DM, Meopaused women with CHD, Smoking
• Reliability ???
Comparison of the Different
Methodologies
Correlations
FMD,IMT,PWV
Correlations - Methods
• Subject
– 168 people (118 men, mean age ; 55YO) who received the ‘carotid ultrasound and vascular function tests’ in ‘SNUH Healthcare System’ during November, 2003 ~ June, 2005
• IMT, FMD ; GE vivid 7, 7.5-10.5MHz probe
• PWV, ABI ; FUKUDA VS-1000
IMT & PWV
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.000.0
2.5
5.0
7.5
10.0
12.5
15.0
17.5
IMT (mean) (mm)
PW
V (
m/s
)
IMT mean & PWV
(r= 0.35, p < 0.0001)
IMT max & PWV
(r= 0.34, p < 0.0001)
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.000.0
2.5
5.0
7.5
10.0
12.5
15.0
17.5
IMT (max) (mm)
PW
V (
m/s
)
IMT & FMD
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.000
5
10
15
20
25
30
35
IMT (mean) (mm)
FM
D (
%)
IMT mean & FMD
(r= -0.16, p = 0.039)
IMT max & FMD
(r= -0.15, p = 0.052)
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.000
5
10
15
20
25
30
35
IMT (max) (mm)
FM
D (
%)
PWV & FMD
PWV & FMD (r= -0.178, p = 0.02)
0 5 10 15 20 25 30 350.0
2.5
5.0
7.5
10.0
12.5
15.0
17.5
FMD (%)
PW
V (
m/s
)
Determinant of Arterial Function
• FMD (functional) ; SBP, Hb A1c, Cr
• IMT (anatomical) ; age, HTN, SBP, DM, FBS,
Hb A1c, LDL, smoking, homocysteine
• ABI (stenosis) ; SBP, Hb A1c
• PWV (mechanical nature) ; age, HTN, SBP
Different Mechanisms
Future
• New parameters to stratify CV risk
• New therapeutic target to reduce CV risk
• Before wide acceptance
– Standardization
– Consider the confounding factors
Recommended