Cardiac Output

Measuring Cardiac Output

Innovative Tools and Techniques

Continuous beat-to-beat measurements of mouse cardiac output (minus coronary flow) can be made directly with the new 1.5PSL Nanorobe positioned on the ascending aorta. The flowmeter displays mean flow; recorded waveform data are used in calculations of stroke volume, peak flow, aortic flow acceleration dF/dt, aortic input impedance, systemic vascular resistance and heart rate. Flow measurements with pressure data are used to determine pressure volume relations in cardiac function and can now be applied in transgenic mouse models.

The 1.5PSL flowprobe is designed specifically for chronic implantation on the ascending aorta of the mouse. The transducer housing is < 5 mm and is easily accommodated in the thoracic cavity of the mouse. The nonconstrictive fit does not interfere with the ascending aorta or pulmonary artery. The probe's flexible cable is easily tunneled under the sking for connector exteriorization.

1.5SL_nano

1.5 PSL

Chronic Ascending aorta implant protocol in the mouse (ppt)

1.5 Specifications

CAT #

VESSEL

BIDIRECTIONAL FLOW

ACCURACY

ULTRA-SO UND

Probe

OD mm
acute

Low Flow Normal Flow Max Range
ml/min ml/min ml/min

Zero Offset Absolute Relative
ml/min % %

Frequency
MHz

1.5PSL

1.0 - 1.5

10 40 200

0.2 ± 15 ± 2

4.8

conscious_aorta_trace

Ascending aortic blood flow and pressure in a conscious mouse 7 days after implantation with a 1.5PSL Nanoprobe. Courtesy of B. Janssen, Univ. Maastricht, The Netherlands

Flowmeter Compatibility

Transonic System's new 400-Series modular flowmeters are compatible with the 1.5PSL probe. Single channel T106 and dual channel T206 flowmeters manufactured in 2001 that display a mouse sticker ("1.5SL Ready") on the front panel are compatible with the 1.5SL. Older flowmeters cannot be upgraded.

Implantation Techniques

The same techniques for implantation of Transonic Systems' flowprobes in rats are applied to vessel isolation and probe placement in the mouse, but on a smaller scale. Surgeries on this scale are performed with the aid of a surgical microscope

Measuring Flow in the Mouse Aorta
T.L. Smith, PhD, Dept. of Orthopedics, Wake Forest University School of Medicine

To obtain the detailed procedural video showing step-by-step surgery for implantation of the Transonic 1.5PSL flowprobe on the ascending aorta of the mouse
To order call: Tel: 607-257-5300; Fax 607-257-7256
See video stills and implantation protocol below

Implantation of the 1.5 SL Flowprobe on the Mouse Ascending Aorta

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Visualization of ascending aorta in 1.5SL probe lumen.

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1.5PSL Flowprobe positioned for closure

Right Thoracotomy

Under anesthesia and after the mouse has been properly ventilated on a respirator, a right thoracotomy is performed in the 3rd intercostal space to expose the lungs in the thoracic cavity. The right lung is packed clear of the surgical field with a small piece of surgical sponge. The ascending aorta lies directly under the thymus gland.

Careful dissection of the ascending aorta is performed by blunt dissection using microsurgical vessel dilators to free the vessel from connective tissue. The vessel can be manipulated most easily by grasping the small fat pad at the base of the pulmonary artery.

After the aorta has been isolated from the pulmonary artery, two pieces of surgical silk are passed under the vessel to aid in placing the vessel within the lumen of the probe. The flowprobe is introduced into the thoracic cavity and the vessel lifted into the probe lumen so that the J-shaped reflector encircles the aorta.

After confirmation of vessel placement, the sutures are removed and the 1.5SL flowprobe is rotated so the probe cable exits laterally to the right. The thoracotomy can be closed over the probe to establish negative pressure in the thoracic cavity and improve venous return & cardiac output.

For acute measurements, an acoustic coupling gel injected into the flowprobe lumen is used to transmit the ultrasound signal. Gel is not required for chronic applications; fibrous tissue encapsulation of the flowprobe will provide good signal transmission after the animal recovers (3-5 days) and is ready for measurement & experimentation.

Summary

Mouse Cardiac Output & Stroke Volume

Species: Mouse
Weight: 20 - 30 grams
Vessel: Ascending Aorta
Surgical Approach: Right Thoracotomy
Duration: Conscious - chronic 3 weeks

Recommended Probe: 1.5SL
Cable Length: 4 cm
Connector: CA4S
Accessories: Anchor Cuff (AAPC105)

Ascending aorta waveform of 37.2 gram mouse, 1.5SL probe, 21
days post-implant. Cardiac output averaged 16.6 ml/min. Heart
rate was 750 beats/min.

Cardiac Output: 16.6 ml/min
Heart Rate: 750 beats/min
Stroke Volume: 22 microL/min

Significance: Stroke volume used to calibrate impednace catheter for left ventricular relations & studies of cardiac function.

Ascending Aorta 1.5PSL Validation

Janssen, B., Debets, J., Leenders, P., Smits, J., Chronic Measurement of Cardiac Output in Conscious Mice," AJP, 2002; 282(3) R928-935. 47V

Gross, V., Luft, FC, "Exercising Retraint in Measuring Blood Pressure in Conscious Mice," Hypertension 2003 41(4) 879-881.