Ruptured Abdominal Aortic Aneurysm.ppt - Ruptured Abdominal Aortic ...
A unifying explanation of the aortic pulse waveform in humans
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A unifying explanation of the aortic pulse waveform in humans
Dr Justin Davies International Centre for Circulatory HealthImperial College & St Mary’s Hospital
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A unifying explanation of the aortic pulse waveform in humans
Dr Justin Davies International Centre for Circulatory HealthImperial College & St Mary’s Hospital
No conflicts of interest to declare
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Adolescent Middle-aged Elderly
What accounts for the change in shape of the pressure wave form?
McDonald’s Blood Flow in Arteries,4th Edition (1998), Arnold.
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Morphological features of the arterial pressure wave
1
23
Systolicupstroke
Inflectionpoint
Elastic recoil of the aortic
windkessel
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Arterial Windkessel
Systole
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Arterial Windkessel
Systole
Diastole
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Morphological features of the arterial pressure wave
1
23
Systolicupstroke
Inflectionpoint
Elastic recoil of the aortic
windkessel
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Apparentforwardpressure
Apparentbackwardpressure
Simple separation of pressure waveform
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Apparentbackwardpressure
Apparentforwardpressure
Simple separation of pressure waveform
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Apparentbackwardpressure
Apparentforwardpressure
Aortic valve closure
When the aortic valve is closed….
Where does forward pressure come from in diastole?
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Apparentbackwardpressure
Apparentforwardpressure
Artefacts of simple separation of pressure waveform
Total pressure = Forwards originating + Reflected pressure
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Study Aims
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Study Aims
1. Use the combined windkessel-separation technique to explain the arterial pressure waveform
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Study Aims
1. Use the combined windkessel-separation technique to explain the arterial pressure waveform
2. Assess the relative contributions forward and backward pressure and the arterial windkessel make to augmentation pressure
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Study Aims
1. Use the combined windkessel-separation technique to explain the arterial pressure waveform
2. Assess the relative contributions forward and backward pressure and the arterial windkessel make to augmentation pressure
3. Assess how the arterial windkessel relates to pulse wave velocity
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Study Design
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Study Design
Subjects undergoing diagnostic coronary angiography
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Study Design
Subjects undergoing diagnostic coronary angiography
Simultaneous haemodynamic measurements were made at aortic root
Doppler Flow wire(Flowire, Volcano Therapeutics)
Pressure wire(Wavewire, Volcano Therapeutics)
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Patient demographics
• 19 subjects
• 54 ±13 years old
• 9 Female
• 145/80 mmHg
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Pressure separation following windkessel subtraction
Time (ms)
Pres
sure
abo
ve d
iast
olic
(mm
Hg)
Simple wave separation
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Pressure separation following windkessel subtraction
Time (ms)
Pres
sure
abo
ve d
iast
olic
(mm
Hg)
Simple wave separation
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Time (ms)
Pressureabove diastolic(mmHg)
Effects of windkessel subtraction to pressure separation
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Time (ms)
Pressureabove diastolic(mmHg)
Effects of windkessel subtraction to pressure separation
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Time (ms)
Pressureabove diastolic(mmHg)
Effects of windkessel subtraction to pressure separation
dPwk (t) = dPwk x dVwk(t) = flowin(t) – flowout(t)
dt dtdVwk(t) C
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Time (ms)
Pressureabove diastolic(mmHg)
Effects of windkessel subtraction to pressure separation
dPwk (t) = dPwk x dVwk(t) = flowin(t) – flowout(t)
dt dtdVwk(t) C
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Time (ms)
Pressureabove diastolic(mmHg)
Effects of windkessel subtraction to pressure separation
dPwk (t) = dPwk x dVwk(t) = flowin(t) – flowout(t)
dt dtdVwk(t) C
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Time (ms)
Pressureabove diastolic(mmHg)
Effects of windkessel subtraction to pressure separation
dPwk (t) = dPwk x dVwk(t) = flowin(t) – flowout(t)
dt dtdVwk(t) C
'd)'(Q
)PP(P)(P'1
0
0
teC
teet RC
tt
t
inRC
t
RCWk
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Time (ms)
Pressureabove diastolic(mmHg)
Effects of windkessel subtraction to pressure separation
WindkesselPressure
ExcessPressure
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Pressure separation following windkessel subtraction
Time (ms)
Pres
sure
abo
ve d
iast
olic
(mm
Hg)
Simple wave separation Separation after windkessel subtraction
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Pressure separation following windkessel subtraction
Time (ms)
Pres
sure
abo
ve d
iast
olic
(mm
Hg)
Time (ms)
Pres
sure
abo
ve d
iast
olic
(mm
Hg)
Simple wave separation Separation after windkessel subtraction
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Contributors to augmentation pressure
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Augmentationpressure
Contributors to augmentation pressure
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Augmentationpressure
Forward pressure wave
Contributors to augmentation pressure
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Augmentationpressure
Reflected pressure wave
Forward pressure wave
+
Contributors to augmentation pressure
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Augmentationpressure
Reflected pressure wave
+
Windkessel pressure
Forward pressure wave
+
Contributors to augmentation pressure
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Contributors to augmentation pressure
windkessel 82%
forward pressure 15%
reflected pressure 3%
Augmentationpressure
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Contributors to augmentation pressure
windkessel 82%
forward pressure 15%
reflected pressure 3%
Augmentationpressure
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Windkessel: a major determinate of the augmentation pressure
0
20
40
60
80
0 20 40 60 80
Augmentation pressure (mm Hg.s)
Win
dkes
sel p
ress
ure
(mm
Hg.
s)r = 0.98p < 0.001
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Windkessel increases with gold standard of arterial compliance
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0
20
40
60
0 5 10 15 20
r=0.7p<0.001
Pea
k w
indk
esse
lP
ress
ure
(mm
Hg)
Wave speed (m/s)
Windkessel increases with gold standard of arterial compliance
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What accounts for the change in shape of the pressure wave form?
Adolescent Middle-aged Elderly
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What accounts for the change in shape of the pressure wave form?
Adolescent Middle-aged Elderly
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What accounts for the change in shape of the pressure wave form?
Adolescent Middle-aged Elderly
• Explains shape of pressure wave
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What accounts for the change in shape of the pressure wave form?
Adolescent Middle-aged Elderly
• Explains shape of pressure wave
• Biological plausibility
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What accounts for the change in shape of the pressure wave form?
Adolescent Middle-aged Elderly
Close correlation between windkessel and pulse wave velocity
0
20
40
60
0 5 10 15 20
r=0.7p<0.001
Peak windkesselPressure (mmHg)
Wave speed (m/s)
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What accounts for the change in shape of the pressure wave form?
Adolescent Middle-aged Elderly
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Dr Jamil Mayet Prof Alun Hughes
British HeartFoundation
CoronaryFlowTrust
Key Findings
• Waves and windkessel make up pressure waveform• Windkessel greatest contributor to augmentation
pressure • Windkessel highly correlated with PWV
Dr Darrel Francis Prof Kim Parker
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Can the result of the Café study be explained by the arterial windkessel?
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Parameter Atenolol Amlodipine Difference
(Atenolol-Amlodipine)
Statistics t-test (p)
Augmentation
Index (%)
31.9
(29.6, 34.2)
25.5
(23.4, 27.7)
6.4
(4.1, 8.7)
<0.001
Augmentation (mmHG)
16.1 (14.4, 17.7)
12.4 (10.9, 13.9)
3.7 (2.0, 5.3)
0.001
PWVCF
(msec-1) 10.7
(10.0, 11.4)
10.2 (9.7, 10.7)
0.5 (-0.2, 1.2)
0.3
Can the result of the Café study be explained by the arterial windkessel?
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Peripheral pressure
Derived central pressure
Can the result of the Café study be explained by the arterial windkessel?
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Peripheral pressure
Derived central pressure
Can the result of the Café study be explained by the arterial windkessel?
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Peripheral pressure
Derived central pressure
Can the result of the Café study be explained by the arterial windkessel?
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Wave Intensity Analysis
Separation of forward pressure wave using wave intensity analysis and Fourier methods gives identical results
Fourier technique
Start with p(t) and u(t) Differentiate to get dp(t) and du(t) Forward pressure(t) = (1/2)dp(t) + (1/2)rho c du(t) Integrate it to get pplus(t)
Start with p(t) and u(t) Fourier transform to get P(f) and U(f) Forward pressure) = (1/2) P(f) + (1/2) rho c U(f) Reverse Fourier transform to getpplus(t)
Time (ms)
Pre
ssur
e (P
a)
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Measured blood pressure Measured blood pressure
Windkessel
Measured blood pressure
Proximal-originating wave
Distal-originating wave
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140
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Pre
ssur
e(m
mH
g)
Time (ms) Time (ms) Time (ms)
Measured blood pressure Measured blood pressure
Windkessel
Measured blood pressure
Proximal-originating wave
Distal-originating wave
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Pre
ssur
e(m
mH
g)
Time (ms) Time (ms) Time (ms)
Determination of the start of the windkessel inflection point
Start of change of windkessel gradient
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What accounts for the change in shape of the pressure wave form?
Adolescent Middle-aged Elderly
Windkessel 82% of augmentation pressure
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Shape of pressure waveform determined by timing and magnitude of forward and backward waves and windkessel
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Windkessel
Forward Pressure
Reflected Pressure
Video to show the effect of windkessel subtraction on pressure separation
Total pressure
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What accounts for the change in shape of the pressure wave form?
Adolescent Middle-aged Elderly
0
20
40
60
80
0 20 40 60 80
Augmentation pressure (mm Hg.s)
Win
dkes
sel p
ress
ure
(mm
Hg.
s)
r = 0.98p < 0.001