a noninvasive alternative to +dp/dtmax: peak aortic blood acceleration
TRANSCRIPT
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 [email protected]
Thank YouFor additional information on the products and applications presented during this webinar please visit, www.indusinstruments.com