A Noninvasive Alternative to +dP/dtmax: Peak Aortic Blood Acceleration

A webinar for cardiovascular researchers interested in using noninvasive blood flow velocity measurements to quantify cardiac contractile and relaxation function in rodents.

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Evaluation of Cardiac Contractile and Relaxation Function Using Noninvasive Blood Flow Velocity Measurements

Anilkumar K. Reddy, PhDAssistant Professor Medicine - Cardiovascular SciencesBaylor College of MedicineConsultant – Indus Instruments

Methodology• Pulsed Doppler ultrasound

• Why is it needed?

• How does it work?

Applications• Cardiac systolic function

• Cardiac diastolic function

• Coronary flow reserve

• Pressure overload - cardiac hypertrophy

Presentation Outline

5

Advantages

• Noninvasive - longitudinal studies

• Short signal acquisition times

• Can be measured at various locations

• Possible to achieve small angles

Know-how

• Knowledge of anatomy

• Shapes and timing of waveforms

Pulsed Doppler Ultrasound

“Not an echocardiography system”

Most CV measurements and parameters are functions of time, so we need waveforms

“Have a nice day

at the lab, dear?”

But, the challenge is to be Noninvasive

• Rodents are animals of choice in basic research

• Genetic, surgical, pharmacological manipulations

• Alterations in cardiovascular system

• Need cardiovascular phenotyping

Small Animal Noninvasive Cardiovascular Phenotyping

Methodology – Doppler Flow Velocity

Pulsed Doppler Ultrasound: How does it work?

Relationship between blood velocity & Doppler shift is given as:

V = (c Δf)/(2fo cos θ)

where…

V = flow velocity (cm/sec)

c = velocity of sound (cm/sec)

Δf = Doppler shift (Hz)

fo = transmission frequency (Hz)

θ = angle between velocityvector & beam vector

θ artery

Why Blood Velocity ?

Scaling in mammals from elephants to mice

General allometric equation: Y = a.BWb

Parameter Relationship to BW (kg)* Value (BW=0.025kg)

Heart weight (mg) a BW1 4.3 BW 112 mgLV volume (μl) a BW1 2.25 BW 56 mlStroke volume (μl) a BW1 0.95 BW 24 mlHeart rate (bpm) a BW-1/4 230 BW-1/4 578 bpmCardiac output (ml/min) a BW3/4 224 BW3/4 14 ml/minAortic diameter (mm) a BW3/8 3.6 BW3/8 0.9 mmArterial pressure (mmHg) a BW0 100 100 mmHgAortic velocity (cm/s) a BW0 100 100 cm/sPW velocity (cm/s) a BW0 500 500 cm/s

*T.H. Dawson, “Engineering design of the cardiovascular system of mammals,” Prentice Hall, 1991.

Doppler Flow Velocity and

Rodent Monitoring Systems

[click to learn more]

Set-up for Noninvasive Doppler

Measurements in Mice

• Maintain anesthesia

• Monitor ECG and respiration

• Monitor body temperature

• Maintain board or body temperature

• Perform noninvasive measurements

• Perform surgery

• Perform invasive measurements

ECG

Respiration

With this configuration we can:

RA LA

LLRL

ECG/RespElectrodes

Mouse ECG &Warming Pad

WarmingZone

ECG/Resp Amplifier Temp Control

• Cardiac systolic function

• Cardiac diastolic function

• Coronary flow reserve

• Cardiac pressure overload

Challenge is to acquire signals with high spatial and temporal resolution

Mouse Heart Mouse Aorta

Cardiac Applications of Pulsed Doppler Ultrasound

Challenge is to be noninvasive

• Small size – short distances

• High heart rates – faster times

10 MHzpulsed

Doppler

ECG

Car

dia

c D

op

ple

r M

easu

rem

ents

in M

ice

+90

+60

+30cm/s-0

-30

-60

Aortic

Mitral

A----

mo|

mc|

|ao

------P

Accel

------E

|ao

|ac

+12-

+8-

+4-kHz

0-

-4-

-8- R|

ECG

Cardiac Signals and Timing

Probe

The magnitude and shapes of the inflow and outflow velocities in mice are identical to humans.

380 ms

Application – Cardiac Systolic Function

Mouse cardiac Doppler signals - Aortic velocity

Using 10 MHzDoppler Probe

ECG

Aortic Velocity

Cardiac systolic parameters

ao ac

R-R Interval = 156 ms

Aop

Systole Diastole

t1

Aop – Peak aortic flow velocityt1 – Pre-ejection timet2 – Aortic ejection Tine t3 – Time to peak velocity (Rise time)

Aortic Outflow Waveform

ao – Aortic valve opens ac – Aortic valve closes

t2

ECG

t3

Measurements/parameters:• Heart Rate (from R-R)

• Pre-ejection time

• Rise time

• Ejection time

• Peak Velocity

• Mean Velocity

• Peak Acceleration

• Mean Acceleration

• Stroke Distance

Mouse Cardiac Contractility and Relaxation

Aortic Velocity

LV Pressure (P) First Derivative of LV Pressure - dP/dt

dP+―dtmax

dP– ―dtmax

“Invasive & Terminal”

Hunt et al., Cathet Cardiovasc Diagn 23, 1991

Peak dP/dt = 74.2V2/T + 847R = 0.772500

2000

1500

10000 5 10 15 20 25

Pea

k d

P/d

t(m

mH

g s

-1)

V2/T (m2 s-3)

Not evaluated for various loading conditions

Noninvasive assessment of LV contractility - Dogs & Patients

Harada et al., Heart Vessels 3, 1987

Dogs800

600

400

200

00 200 400 600 800

ρc

Max

du

/dt

(kP

a/s)

Max dP/dt (kPa/s)

Y = 1.01X - 2R = 0.97

Patients

Noninvasive assessment of LV contractility - Sheep

Bauer et al., JACC 40, 2002

Aortic acceleration (LVOTAcc) vs. LV maximal elastance ( Em) - various loading conditions; - acute coronary occlusion

Good correlation between LVOTAcc and LV +dP/dt (r = 0.62)

LV maximal elastance ( Em)

Aortic acceleration (LVOTAcc)

Aortic outflowvelocity

waveform

LV pressure waveform

ECG waveform

Simultaneous measurement of aortic flow velocity and left ventricular pressure along with ECG

Aortic OutflowVelocity (V)

Left VentricularPressure (P)

dV/dt

dP/dt

Aortic outflow velocity (V) & its derivative (dV/dt) andLeft ventricular pressure (P) & its derivative (dP/dt)

Noninvasive surrogate measurements for peak +dP/dtderived from Doppler aortic blood flow velocity waveform

Peak aortic acceleration Mean aortic acceleration

Mouse Studies: Acceleration Examples

Vincelette et al., Translational

Research, vol.148, 2006

Weisleder et al., PNAS, 101, 2004

Bcl-2 overexpression prevents decline incardiac function in desmin null mice

At 8 months of age des-/-Tg(bcl2)BCap+/+ peak aortic velocity and mean acceleration are restored to normal levels.

Cieslik et al., J Molec Cell Cardiol, 63, 2013

Cardiac Systolic Function: Acceleration Examples

Saline AICAR

Example 1 Example 2

TAC in SRC-2 KO mice results in greater decline of cardiac function (WT-n=16; KO-n=14)

100

80

60

40

20

0

pea

k a

ort

ic v

elo

city

(cm

/s) 7000

6000

5000

4000

3000

2000

1000

0

mea

n a

ccel

erat

ion

(cm

/s2 )

Rieneke et al., PLoS ONE, 7:e53395, 2012

Cardiac Systolic Function: Acceleration Examples

Example 3

Cardiac Systolic Function: Aortic Velocity Examples

Robinson et al., BioMed Res Intl, #645153, 2015

Sham AprepitantPreteated

Kelsey et al., PLoS Genetics, 9, 2013

Wild type Klf3H275R/+ mice

cm/s

Cieslik et al., J Molec Cell Cardiol, 63, 2013

Saline AICAR

Cardiac Systolic Function: Peak Aortic Velocity

Taffet et al., J GeronBiol Sci 52A, 1997.

Reddy et al., J GeronBiol Sci 62A, 2007.

Taffet et al., Am J Physiol 270, 1996.

Mayr et al., PhysiolRep 4, e12765, 2016.

Reddy et al., IEEE TBME 52, 2005.

DeLaughter et al., FASEB J 13, 1999.

Hartley et al., Am J Physiol 279, 2000.

Application – Cardiac Diastolic Function

Mouse Cardiac Doppler Signals – Mitral Velocity

Using 10 MHzDoppler Probe

ECG

Mitral Velocity

Cardiac Diastolic Function

mc

ao ac

mo mc

R-R Interval = 161 ms

Ep

Ap

Systole Diastole

t1 t2 t3

t5

t6

t4

t8

Ep – Peak early flow velocityAp – Peak atrial flow velocity t1 – Isovolumic contraction timet2 – Isovolumic relaxation time t3 – Duration of early flow velocity (EFV) t4 – Acceleration time of EFV t5 – Deceleration time of EFV t6 – Time from Ep-½Ep

t7 – Linear deceleration time of EFVt8 – Duration of atrial flow velocity

mc – mitral valve closesao – Aortic valve opens ac – Aortic valve closesmo – Mitral valve opens

t7

ECG

Mitral Inflow Waveform

Cardiac Diastolic Function

mc

ao ac

mo mc

R-R Interval = 161 ms

Ep

Ap

Systole Diastole

t1 t2 t3

t5

t6

t4

t8

Mitral Inflow Waveform

t7

ECG

Measurements/parameters:• E-Time Duration

• E-Acceleration Time

• E-Deceleration Time

• E-Peak to ½ E-Peak Time

• E-Linear Deceleration Time

• A-Time Duration

• Isovolumic Contraction Time

• Isovolumic Relaxation Time

• E-Peak Velocity

• E-Stroke Distance

• E-Linear Deceleration Rate

• A-Peak Velocity

• A-Stroke Distance

• E-A Peak Velocity Ratio

Cardiac Diastolic Function

÷ =

Application – Coronary Flow Reserve

Problems:

1. Coronary arteries are small, ≈200μm

2. They are close to many other vessels

3. They move along with the heart

4. Seems impossible to measure ....

Coronary Blood Flow in Mice?

Method to sense coronary blood flow noninvasively in mice

20 MHz Doppler Probe(((

-50cm/s

Hartley et al., Ultrasound Med Biol 33, 2007

Noninvasive coronary Doppler signals from a mouse anesthetized at low and high levels of isoflurane gas

-90-

-

-

-60-

-

-

-30-

-

cm/s

- 0 -

| 400 ms |

24-

16-

8-

kHz

0-

ECG HR = 450

Vlow

low =1.0% high =2.5%

CFR = H/B = Vhigh/Vlow = 4.2

HR = 465

Vhigh

Co

ron

ary

Res

erve

(H

/B)

in y

ou

ng,

ad

ult

, old

an

d A

po

E-/-m

ice

0

20

40

60

80

100

120

140

6 wk 3 mo 2 yr ApoE

Base

Hyper

H/Bx

140-

120-

100-

80-

60-

40-

20-cm/s

0-

H/B-4

-3

-2

-1

-06 wk 3 mo 2 yr 2 yr ApoE-/-

B

H

H/B

B - Baseline Peak Diastolic Velocity (1.0 % Iso) H - Hyperemic Peak Diastolic Velocity (2.5 % Iso)

Mean±SEM

Hartley et al., Ultrasound Med Biol 33, 2007

Application – Pressure Overload (Hypertrophy)

Aorticband

-500

cm/s

-0

-20

-0-160

cm/s

-0

ECG

Aortic Arch Jet Velocity - 10 MHz Doppler

Left Carotid Artery Velocity - 20 MHz Doppler

Right Carotid Artery Velocity - 20 MHz Doppler

msec

ΔP~75 mmHg

mm scalePe

rip

her

al V

ascu

lar

Do

pp

ler

Sign

als

Fro

m a

Ban

ded

(TA

C)

Mo

use

Hartley et al., Ultrasound Med Biol 34, 2008

RightCarotidVelocity

LeftCarotidVelocity

StenosisJet

Velocity

Effe

cts

of

Tran

sver

se A

ort

ic B

and

ing

on

Blo

od

Flo

w P

atte

rns

in M

ice

-100--50cm/s-0

-100--50cm/s-0

-300--150cm/s-0

| 0.5 sec |

P=4V2 =49mmHgP=4V2 =15mmHg

No band Loose Band Tight Band

PI=5.6; RI=1.1; M=9.1

PI=6.7; RI=1.1; M=8.4

PI=11.8; RI=1.3; M=10.3

PI=0.8; RI=0.5; M=7.2

PI=8.3; RI=1.1; M=9.6

PI=3.6; RI=0.8; M=7.8

P=4V2 =4mmHg

Co

ron

ary

Blo

od

Vel

oci

ty in

a B

and

ed M

ou

se Hartley et al., Ultrasound Med Biol 34, 2008

0

20

40

60

80

Pre 1 d 7 d 14d 21dPre 1 day 7 day 14 day 21 day

80-

60-

40-

20-

mmHg

0-

-4

-3

-2

-1

H/B

-02 3.2 51 2.2 62 1.7 67 1.4 74 1.1P

CFR(H/B)

Pre

ssu

re D

rop

an

d H

/B A

fter

Ao

rtic

Ban

din

g

Hartley et al., Ultrasound Med Biol 34, 2008

Summary

✓ Cardiac systolic function (aortic FV- LV contractility)

✓ Cardiac diastolic function (mitral FV - LV relaxation)

✓ Myocardial perfusion index (coronary FV - CFR)

✓ Pressure overload by TAC (cardiac and coronary reserve)

▪ Noninvasive - allows for serial studies

▪ Measurements at very small angles

▪ Can be measured at various locations

▪ Short signal acquisition times

▪ Replaces invasive measurements

▪ Not echocardiography

Acknowledgements

Craig HartleyLloyd Michael George TaffetMark Entman

Yong Xu

Thuy PhamCelia Pena Heredia

Jennifer PociusJim Brooks

Ross Hartley

Technicians: Faculty Collaborators:

Sridhar Madala - Indus Instruments

Yi-Heng Li - NCK University, Taiwan

Jim Wang - Berlex Biosciences (now at Crown Biosciences)

Rochelle Buffenstein - UT San Antonio (now at Calico Labs)

Anilkumar K. Reddy, PhDAssistant Professor

Medicine - Cardiovascular SciencesBaylor College of MedicineConsultant – Indus Instrumentsareddy@bcm.edu

Thank YouFor additional information on the products and applications presented during this webinar please visit, www.indusinstruments.com