Measure Cardiovascular Function Non-Invasively in Mice

Indus Doppler Systems for mice use high frequency ultrasound to non-invasively measure cardiovascular parameters such as blood velocity, heart rate, ejection time, pulse wave velocity,

EXPERIMENTAL SETUP TO ACQUIRE DOPPLER BLOOD FLOW VELOCITY DATA FROM MICE
	The overall experimental setup to acquire Doppler blood flow velocity data from mice is shown above. The mouse is anesthetized with Ketamine/Xylazine/Acepromazine cocktail, Nembutal cocktail, or other anesthetics depending on the desired type of study. The mouse is placed in supine position with its four limbs taped to four electrode plates mounted on a board. These electrodes are connected via a cable to the ECG module in a signal processing system that will provide the mouse ECG signal output. A 10 MHz pulsed Doppler probe is used with its tip placed just below the sternum and positioned to obtain a blood flow velocity signal from the aortic outlet or mitral inlet. In addition, blood flow velocities from peripheral arteries of mice can be obtained using a 20 MHz pulsed Doppler probe. These probes are plugged into analog pulsed Doppler signal generators (10 or 20 MHz) such as the “Baylor Multichannel High Frequency Pulsed Doppler Analog Mainframe”. Other equivalent systems such as those from Crystal Biotech / Data Sciences Inc. can also be used. These systems will generate in-phase and quadrature Doppler demodulated audio signals. In the figure above, the Doppler signals are acquired, processed, and displayed as a real-time spectrogram along with the ECG signal using the DSPW. The software also allows the user to perform offline analysis of the data and to generate reports. The DSPW can measure blood velocities in both major and peripheral arteries of small animals, even mice; all without entering the test subject! The spectrograms below are traced to the artery where blood velocity is being measured. Click on each spectrogram to see how the blood velocity signal can be obtained using the DSPW and a topical probe.

Doppler Mainframe Modules 10 OR 20 MHZ PULSED DOPPLER MODULE This module is suitable for most flow velocity measurements in smaller (20 MHz) and larger (10 MHz) vessels of acute and chronically instrumented animals. The output is directional with either advancing or receding flow displayed as positive. Outputs are mean velocity, phasic velocity with selectable damping, and a voltage proportional to the range gate delay. Doppler shifts up to 31.25 kHz can be measured with the standard 62.5 kHz pulse repetition frequency (PRF). This corresponds to a maximum velocity of 166 cm/s using a 20 MHz probe or 330 cm/s using a 10 MHz probe with a beam angle of 45 degrees. These modules can also be used with tubing mounted probes to measure blood flow noninvasively in mice and other animals. HIGH VELOCITY 10 OR 20 MHZ PULSED DOPPLER MODULE This module was designed to overcome the high velocity limitation of the standard module. By "unwrapping" the aliased high frequencies, it can record Doppler shifts up to 62.5 kHz (~300 cm/sec at 20 MHz or ~600 cm/sec at 10 MHz) using the standard 62.5 kHz PRF. Because of these extra features it is trickier to use (more critical controls to set) than the standard module. It has been found it most useful on hepatic, renal, and mesenteric arteries. WIDEBAND TRANSIT-TIME DIMENSION GAUGE MODULE This is the standard transit-time dimension gauge (sonomicrometer) used with paired ultrasonic crystals for measuring myocardial segment length, wall thickness, and diameter and for measuring blood vessel diameter. Dimensions from 2 to 50 mm can be measured from up to 4 sets of crystals (requiring 4 modules) simultaneously without interference. This module can be used with crystals ranging in frequency from 5-20 MHz. 10 OR 20 MHZ SINGLE CRYSTAL DISPLACEMENT MODULE This module is used to measure ventricular thickening from a single epicardial transducer, thus eliminating the need for any intramyocardial crystals. Rather than tracking one layer, it measures thickening at a fixed depth from the epicardial surface as selected by the range gate delay. Thickening fraction is estimated by dividing the measured thickening (in mm) by the range gate depth (also in mm) which can be set to any depth from the subepicardium to the subendocardium. Although it doesn't measure absolute thickness, it is much easier to use than the two crystal method, and has been very useful in evaluating regional ventricular function in studies of ischemia and reperfusion. Resolution is 0.02 (0.01) mm with a maximum measurable thickening of 5 (2.5) mm at a maximum depth of 4 (1.2) cm at 10 (20) MHz. DUAL PRESSURE AMPLIFIER MODULE This non-ultrasound module contains two standard bridge amplifiers suitable for use with pressure transducers such as those made by Gould Statham, Konigsberg, or Millar. Each amplifier is independent with input connector, balance and gain controls, and a phasic/zero/mean output selector switch. The lower amplifier has an additional mean output which is not affected by the selector switch. PRESSURE DIFFERENTIATOR MODULE This module contains a single pressure amplifier as above and also a derivative amplifier and calibrator for dP/dt measurement. Simultaneous outputs are provided for phasic pressure, mean pressure, and dP/dt. A built-in triangle wave generator is used to calibrate the dP/dt output in mmHg/s. ECG/RATE MODULE This module contains a differential ECG amplifier with standard lead switching, an R-wave trigger, and a rate counter. The standard lead set has four limb leads, 2 V leads, and a ground. A cable is also available for direct connection to the “MousePad” ECG board, A simpler module with a 3-lead clip-cable and manual lead switching is also available. Outputs from each module include: ECG, heart rate, and a pulse coincident with the triggered R-wave. TEMPERATURE MODULE This is the Temperature Controller Module that allows for automatic thermal control of the heating pad incorporated on the ECG board, while the temperature of the mouse is monitored with a rectal probe plugged into the port labeled "MOUSE" in blue (see picture to the left). The heating pad uses feedback from either the probe or the heating pad to monitor the temperature and ensure the mouse’s required body temperature is maintained. 5 MHZ MODULE This module is suitable for flow velocity measurements in animals larger than mice (rats, rabbits, guinea pigs, etc.). The output is directional with either advancing or receding flow displayed as positive. Outputs are mean velocity, phasic velocity with selectable PRF, and a voltage proportional to the range gate delay. Doppler shifts depend on PRF selection (low, medium, high). The low setting is ¼ of the mainframe PRF, the medium setting is ½ of the mainframe PRF, and the high setting is equal to the mainframe PRF. The mainframe PRF can be set to either 125kHz or 62.5kHz.

THM100: Temperature & ECG Monitoring in Mice KEEP MICE WARM DURING STUDIES! PROBLEM SOLUTION When mice are anesthetized either for non-invasive studies or for surgery, their temperature regulating mechanisms do not work properly. This can lead to a rapid drop in body temperature in a few minutes and can have fatal results. The conventional solution to this problem is a cumbersome pad with circulating hot water or an overhead heat lamp that can cause electrical interference with ECG monitoring equipment. The Indus Instruments THM100 is a compact tabletop solution that allows you to electronically control a heating element while simultaneously monitoring temperature and ECG activity. ECG MONITORING • Built in ECG electrode contact pads • Electrically isolated ECG amplifier • Monitor ECG activity and obtain heart rate • Audio alert when ECG activity is present/absent • Amplified & filtered analog ECG signal available for chart recorder • Digital ECG trigger signal available TEMPERATURE CONTROL & MONITORING • Complete solution for temperature control and heart rate monitoring • Compact table top design without circulating water • Electronic control of heater to maintain temperature • Monitor either rectal temperature or skin temperature

Sample Mouse ECGs Acquired Using the THM100
		ECG without Lowpass Filter
		ECG with 1 kHz Lowpass Filter
		ECG with 100 Hz Lowpass Filter
		ECG with 30 Hz Lowpass Filter

High Frequency Pulsed Doppler Transducers

Publications:

1. Hartley CJ, Taffet GE, Reddy AK, Entman ML, and Michael LH. “Noninvasive Cardiovascular Phenotyping in Mice”, Institute for Laboratory Animal Research, 43(3):147-158, 2002.

2. Hartley CJ, Reddy AK, Madala S, Martin-McNulty B, Vergona R, Sullivan ME, Halks-Miller M, Taffet GE, Michael LH, Entman ML, and Wang Y. “Hemodynamic Changes in Apolipoprotein E-Knockout Mice”, American Journal of Physiology Heart Circulatory Physiology, 279: H2326-H2334, 2000.

3. Hartley CJ, Lacy JL, Dai D, Nayak N, Taffet GE, Entman ML, Michael LH. “Functional Cardiac Imaging in Mice Using Ta-178”, Nature Medicine, 5:237-239, 1999.

4. Michael LH, Ballantyne CM, Zachariah JP, Gould KE, Pocius JS, Taffet GE, Hartley CJ, Pham TT, Daniel SL, Funk E, Entman ML. "Myocardial Infarction and Remodeling in Mice: Effect of Reperfusion." American Journal of Physiology, 277: H660-H668, 1999.

Other Related Publications:

1. Hartley CJ, Taffet GE, Michael LH, Pham TT, Entman ML. “Noninvasive Determination of Pulse-wave Velocity in Mice”, American Journal of Physiology. 273:H42-47, 1997.

2. Taffet GE, Pham TT, Hartley CJ, "The Age-associated Alterations in Late Diastolic Function in Mice are Improved by Caloric Restriction." Journal of Gerontology A Biol Sci Med Sci 52: B285-B290, 1997.

3. Taffet GE, Hartley CJ, Wen X-Y, Pham TT, Michael LH, Entman ML. “Non-invasive Indices of Cardiac Systolic and Diastolic Function in the Hyperthyroid and Senescent Mouse”, American Journal of Physiology, 270:H2204-H2209, 1996.

Abstracts/Presentations:

1. Madala S, CJ Hartley, and AK Reddy, “Digital Signal Processing in Diagnostic Ultrasound Systems: An Overview”, Houston Society for Engineering in Medicine and Biology, 19th Annual Conference, Houston, Texas, February 2001.

2. Reddy AK, GE Taffet, CJ Hartley, S Madala, TT Pham, LH Michael, and ML Entman, “Measurement of Aortic Input Impedance in Mice”, Houston Society for Engineering in Medicine and Biology, 19th Annual Conference, Houston, Texas, February 2001.

3. Hartley CJ, AK Reddy, S Madala, TT Pham, LN Ochoa, J Pocius, LH Michael, ML Entman, and GE Taffet, “High Resolution Ultrasonic Blood Flow Sensing in Mice”, Houston Society for Engineering in Biology and Medicine, 19th Annual Conference, Houston, Texas, February 2001.

4. Hartley CJ, LN Ochoa, AK Reddy, LH Michael, JS Pocius, TT Pham, CW Scott, ML Entman, J W Clark Jr., and GE Taffet, “Vascular Adaptations to Transverse Aortic Banding in Mice”, IEEE-EMBS conference, Istanbul, Turkey, October 2001.
5. Hartley CJ., AK Reddy, S Madala, B Martin-McNulty, R Vergona, ME Sullivan, M Halks-Miller, LH Michael, GE Taffet, ML Entman, and Y Wang, “Altered Hemodynamics of Atherosclerotic Mice”, Houston Society for Engineering in Medicine and Biology, 18th Annual Conference, Houston, Texas, February 2000.

6. Ochoa LN, TT Pham, J Pocius, CW Scott, DP Doan, AK Reddy, CJ Hartley, LH Michael, and GE Taffet, “Doppler Evaluation of Aortic Constrictions in Mice”, Houston Society for Engineering in Medicine and Biology, 18th Annual Conference, Houston, Texas, February 2000.

7. Reddy AK, GE Taffet, CJ Hartley, S Madala, TT Pham, R Kwun, T Treviño, J Pocius, LH Michael, and ML Entman, “Noninvasive Systolic and Diastolic Blood Pressure Measurement in Mice Using Tail-Cuff Method”, Houston Society for Engineering in Medicine and Biology, 18th Annual Conference, Houston, Texas, February 2000.

8. Hartley CJ, AK Reddy, S Madala, B Martin-McNulty, R Vergona, ME Sullivan, M Halks-Miller, GE Taffet, LH Michael, ML Entman, and Y Wang, “Hemodynamics of Atherosclerotic Mice”, Chicago-2000 World Congress on Medical Physics and Biomedical Engineering, Chicago, July 23-28, 2000.

9. Michael LH, AK Reddy, GE Taffet, TT Pham, J Pocius, ML Entman, and CJ Hartley, “Cardiovascular Physiologic Genomics in Mice”, Houston Society for Engineering in Medicine and Biology, 17th Annual Conference, Houston, Texas, February 1999.

10. Madala S, AK Reddy, and CJ Hartley, “Design of Ultrasonic Doppler Instrumentation for Mice”, Houston Society for Engineering in Medicine and Biology, 17th Annual Conference, Houston, Texas, February 1999.

11. Hartley CJ, JL Lacy, D Dai, N Nayak, AK Reddy, GE Taffet, ML Entman, and LH Michael, “Functional Cardiac Imaging in Mice Using Ta-178”, HIRES 1999, Amsterdam, The Netherlands, September 1999.

12. C. J. Hartley, S. Madala, J. L. Lacy, A. K. Reddy, G. E. Taffet, K. Kurrelmeyer, J. Pocius, T.T. Pham, N. Nayak, M. L. Entman, and L. H. Michael, "Noninvasive Methods to Measure Cardiovascular Function in Mice", National Institutes of Health Bioengineering Symposium, Bethesda, Maryland, USA, February 27-28, 1998.

13. A.K. Reddy, C. J. Hartley, G. E. Taffet, S. Madala, T. T. Pham, and M. L. Entman, "Noninvasive Measurement of Aortic Blood Flow Parameters in Mice", Houston Society for Engineering in Biology and Medicine, 16th Annual Conference, Houston, Texas, USA, April 2-3, 1998.

14. A.K. Reddy, C. J. Hartley, G. E. Taffet, S. Madala, T. T. Pham, and M. L. Entman, "Measurement of Pulse-Wave Velocity in Mice", Houston Society for Engineering in Biology and Medicine, 16th Annual Conference, Houston, Texas, USA, April 2-3, 1998.

15. C.J. Hartley, J. L. Lacy, J. Pocius, S. Daniel, E. Funk, G. E. Taffet, N. Nayak, M. L. Entman, and L. H. Michael, "Characterization of a Murine Model of Heart Failure by Nuclear Angiography", Experimental Biology (FASEB), San Fransisco, California, USA, April 18-22, 1998.

16. C.J. Hartley, J. L. Lacy, G. E. Taffet, S. Madala, A. K. Reddy, M. L. Entman, and L. H. Michael, “Noninvasive Characterization of Heart Failure in a Murine Model of Coronary Occlusion”, XIII Congress of the CSDS; Gent, Belgium, August 27-30, 1998.

17. C.J. Hartley, J. L. Lacy, M. L. Entman, J. Pocius, G. E. Taffet, H. C. Thompson, D. Dai, C. S. Martin, N. Nayak, and L. H. Michael, "Quantitative Left and Right Ventricular Function in Mice with 178Ta Nuclear Angiography", American Heart Association 70th Scientific Sessions, Circulation 96-Supplement I, Orlando, Florida, U.S.A., November 9-12, 1997.

18. C.J. Hartley, G. E. Taffet L. H. Michael, T. T. Pham, L. A. Schildmeyer, G. Karsenty, R.J. Schwartz, and M. L. Entman, "Doppler Assessment of Aortic Pulse-Wave Velocity Velocity in Genetically Altered Mice", American Heart Association 70th Scientific Sessions, Circulation 96-Supplement I, Orlando, Florida, U.S.A., November 9-12, 1997.