PWV & PWA Parameter Extraction / Transfer Function.

PWV & PWA

Parameter Extraction / Transfer

Function

Dorsalis

Carotid

Radial

Femoral

Pulse waves from superficial arteries

Different shapes of waveforms

PWV

PWA

Diagnosis of vascular Disease using pulse waves

Diagnosing Cardiovascular Disease

Old stiff aorta

Young normal aorta

- flow wave : flow of the blood itself - doppler

- diameter wave : diameter change (volume change) of the artery – Infrared

- pressure wave : waveform through the arterial wall – pressure sensor

PWV (Pulse Wave Velocity)

High PWV reflects arterial agingcaused by decreasing arterial elasticity and increasing systolic pressure

High PWV reflects arterial agingcaused by decreasing arterial elasticity and increasing systolic pressure

PWV (Pulse Wave Velocity)

: Velocities of Pulse waves traveling through the arterial wall between two

recording sites provides useful noninvasive index for diagnosing arterial aging and stiffness

PTT2PTT1

Distance

PTT1

PWV =

ECG Electrode

PCG Sensor

Femoral artery

Dorsalis Pedis artery

Carotid artery

Radial artery

PWV (Pulse Wave Velocity)

Algorithm for detecting upstroke point

– Assign threshold

– 1st differential maximum amplitude

– 2nd differential maximum amplitude

– intersecting tangent method

Feature Extraction

Patient’s DB

PWV values

Feature extraction

Calculation of PWV Values

A Study for the comparison of newly developed medicines

• Atenolol/Bendroflumethiazide vs. Amlodipine/Perindopril

• New medicine reduced the fatal and non-fatal Stroke up to 23%

• New medicine reduced the death rate caused by cardiovascular disease and

myocardial infarction up to 16%

• However, there were no differences in the Brachial Blood Pressure values

CAFE

(conduit artery function evaluation)

ASCOT

(Anglo-Scandinavian Cardiac Outcomes Trial)

Importance of Central Blood Pressure

forward wavefrom the heart reflected

from bifurcation

Forward and Reflected Pressure Pulse

Resistanceartery

Central Aortic Pulse (Young Elastic Artery)

Resistanceartery

Central Aortic Pulse (Old Stiff Artery)

• Increased Left Ventricular Load (LV)

• The area under the pressure-time curve during systole is by definition of LV load

• Increase in LV load accelerates increase in LV mass and increases risk of LV hypertrophy

• Reducing the Coronary Artery Pressure

• The pressure that is perfusing the coronary arteries during the

critical diastole period is reduced

• increasing the risk of myocardial ischemias

(mm

Hg

)

0 100 200 300 400 500 600 700 800 900 1000

Aortic

Systole Diastole(msec)

70

80

90

100

110

120

130

140

150

(mm

Hg

)

0 100 200 300 400 500 600 700 800 900 1000

Aortic

Systole Diastole(msec)

70

80

90

100

110

120

130

140

150

Central Aortic Pulse

• Definition : Aix(%) = AG/PP*100

• Algorithm : Augmentation Index is defined as the first zero

crossing from positive to negative of the fourth derivative and occurs 55ms after onset of systolic pressure

AG : Augmentation

PP : Pulse Pressure

AIx (Augmentation Index)

Negative slope and zero-crossing55msec after the upstroke point

Extraction of AIx Point

4th Derivatives

a: systolic peakb: augmentation pointd: dicrotic notch

1st Derivatives after the systolic peak

Clinical Evaluation

Transfer Function

Data Select Model

Characterization

Modeling

Verification/Validation

Applications

System Characterization & ARX Model

General-linear polynomial model

ARX model

)(),()(),()( 11 neqHnuqGqny k

),(),(

),(),( 1

qFqA

qBqG

),(),(

),(),( 1

qDqA

qCqH

1)()()( qFqDqC

)()()()()()()()( neknuqBnenuqBqnyqA k

RADI pressure wire

Analysis systemSBP

PP

Clinical Evaluation