Download Experimental set-up for evaluating left ventricular pressure (Millar)

Measurement of Left Ventricular
Performance in Mice
Mouse Physiology Core
Department of Molecular and Cellular Physiology
University of Cincinnati College of Medicine
Scientific Director: John N. Lorenz, Ph.D.
1) Measurement of LV pressure and dP/dt in the
closed-chest mouse using a high-fidelity Millar
pressure transducer
Experimental set-up for evaluating left ventricular pressure
(Millar) and systemic arterial pressure (COBE) in a mouse.
Data are processed and recorded using a PowerLab system
from ADInstruments
Close-up view of a high-fidelity Millar catheter the tip
diameter is about 0.5 mm. The pressure-sensing surface is
shown at the tip of the catheter
Sample tracing of left ventricular pressure and femoral artery
pressure in a mouse. Arrow shows the point where the Millar
catheter crosses the aortic valve and enters the ventricle. The
inset show stability of the recording over time.
Ventricle
Femoral Pressure
Ventricular Pressure
100
Pressure (mmHg)
80
60
100
80
40
60
40
20
0
20
100
80
60
40
0
5 sec
20
0
0.5 sec
-20
0.0
0.5
1.0
1.5
Time
2.0
2.5
3.0
Sample results of ventricular performance showing incremental enhancement
of baseline contractility (as evidenced by the lower dP/dt tracing) in
heterozygous and homozygous phospholamban-deficient mice. This model
provide a clear demonstration of the sensitivity of this approach
Phospholamban Knockout
BP (mmHg)
120
100
80
60
40
20
0
LVP (mmHg)
120
100
80
60
40
20
0
dP/dt (mmHg/s)
Wild Type
20k
Heterozygous
Homozygous
10k
0
-10k
0.1 sec
-20k
HR = 480
HR = 431
HR = 457
Summary data showing the effect of β-adrenergic
stimulation in wild type, and phospholamban-deficient mice.
Effect of Iso on Cardiac Contraction
Max dP/dT (mmHg/s)
24,000
22,000
20,000
18,000
16,000
14,000
12,000
10,000
PLB (+/+) (n=7)
PLB (+/-) (n=8)
PLB (-/-) (n=5)
8,000
6,000
Cont
0.01
0.02
0.04
0.08
0.16
0.32
Isoproterenol Dose (ng/min/gBW)
2) Force frequency analysis using an intracardiac, bipolar pacing electrode
Bipolar pacing electrode – about 0.3 mm diameter - shown in
comparison to the Millar transducer. Electrode is introduced
via the right jugular vein, and advance to the right atrium.
Pacing is accomplished using a Grass stimulator.
Left: Sample tracings of LV pressure and dP/dt before and during
electrical capture of the SA nodal rhythm. Bottom tracings show
heart rate increasing from 400 – 500 when the stimulating pulses
are initiated; an immediate increase in dP/dt is evident. Right:
Summary of the force frequency relationship in closed–chest mice.
LV Pressure (mmHg)
Femoral BP (mmHg)
140
120
100
80
60
40
20
0
160
140
120
Force-Frequency Relationship
100
80
60
40
10k
20
0
10,000
5,000
0
-5,000
-10,000
Heart Rate (BPM)
500
400
300
200
100
0
Pacing
Stimulus
1 sec
LV dP/dt (mmHg/sec)
LV dP/dt (mmHg/s)
15,000
9k
8k
7k
6k
5k
400
450
500
550
600
Heart Rate (BPM)
650
700
3) Pressure-Volume analysis in the closed chest
mouse: Impedance measurements.
Combination Millar Pressure-Volume catheter (~0.5mm
diameter). Flanking the central pressure transducer (circle)
are a pair of excitation electrodes (red arrows), which apply a
constant oscillating current, and a pair of signal electrodes
(blue arrows) to sense volume-dependent changes in voltage.
Original recording of LV pressure (top, green tracing) and LV
volume (bottom, blue tracing).
Recording of femoral blood pressure (red) LV pressure (green) and LV
volume (blue) under steady state conditions and during a momentary
increase in afterload. Afterload was increased by inflating a small
balloon positioned in the descending aorta (aortic constriction, AC).
Inset shows the resulting family of pressure-volume loops during
aortic constriction-induced elevation of afterload (shown in the
highlighted section of the main recording). The end-systolic pressure
volume relation is indicated.
Sample pressure-volume loops obtained from a wild type mouse
under baseline conditions (blue) and during β–adrenergic
stimulation with dobutamine (red).
LV Pressure (mmHg)
100
80
60
40
20
0
0
5
10
15
LV Volume
20
25
30
3) Two-dimensional, M-mode echocardiography
and pulse-Doppler flow analysis the intact
mouse.
Two-dimensional image of the mouse heat showing clearly
defined borders of the left ventricular chamber. The aortic
out-flow tract can also be seen.
M-Mode image (“ice-pick view”) of LV contraction. Entire span of
the image is one second of recording, showing six consecutive
ventricular contractions along a one-dimensional, short-axis view.
Pulse-Doppler recording of aortic outflow (one second
recording). By convention, movement away from the transducer
(during systole) results in a negative deflection.
Pulse-Doppler recording of mitral inflow during diastole (one
second recording). The end-diastolic atrial contraction is clearly
represented. By convention, movement toward the transducer
results in a positive deflection.
4) Measurement of cardiac output by
thermal dilution.
Set-up for measurement of
thermal dilution measurement
ofSet
cardiac output. Cold saline
is injected into the flow of
blood leaving the left
ventricle via a catheter
introduced in the right
carotid artery. The resulting
“temperature-dilution” curve
is monitored via a
temperature probe positioned
in the abdominal aorta via the
femoral artery. In contrast
to the conventional approach,
this configuration avoids the
substantial loss of indicator
(ie temperature) that would
occur if the cold saline were
injected into the right
atrium, necessitating transit
through the pulmonary
circulation.
Arterial
pressure
Cold saline
Bolus 10-20ul
Temperature Probe
0.23 mm OD
Venous Infusion
Sample recording of a thermal dilution curve – the injected bolus of
cold saline passes the temparature probe, there is a transient
decrease in temparature that is proportional to cardiac output.
Original tracing of three consecutive thermal dilution curves (15-20
seconds apart). Upper tracing is blood pressure and shows the
artifactual increase that occurs during injection of the salin bolus.
Lower tracing shows the resulting transient decrease in temperature.
The range of the measurements is less than 10%.
Results of an experiment in which cardiac output was measured by
thermal dilution (yellow) and total peripheral resistance derived from
CO and MAP. Three measurements (indicated by the blue symbols)
were taken under each of the conditions shown (baseline,
isoproterenol infusion, saline volume expansion and hemorrhage).
5
35
Cardiac Output (ml/min)
30
4
25
3
20
15
2
10
1
5
Isoproterenol
0
Baseline
SVE
Baseline
0
Hemorrhage
Peripheral Reisistance (mmHg/ml/min)
Thermal Dilution