Please remember that Millar pressure-volume catheters only record the volume found between electrodes. Therefore, you might see lower stroke volume values because you are underestimating the heart chamber volume due to small electrode spacing.
For example, the spacing of the PVR-1030 is 3mm, but the ventricle of interest may be larger than that. So, you may only measure a fraction of the ventricle volume. For this reason, the 1F mouse catheter has different variants: the 1035 has a spacing of 3.5mm, and the 1045 has a spacing of 4.5 mm. It is recommended that the heart of a control animal be physically excised and the ventricle length measured to determine what catheter is appropriate.
With the conductance method, incorrect calibration processes can also contribute to underestimating or overestimating the volume.
For further technical assistance with this or any other issue, please contact ADInstruments Technical Support by clicking HERE.