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Updated: Jul 14, 2026
Cardiac Pressure-Volume Loop Analysis Using Conductance Catheters in Mice
Published on: September 17, 2015
Left ventricular volume measurement by the conductance catheter and variations in the hematocrit in small animals
Werner Heimisch1, Hubert Schad, Ralf Günzinger
1Department of Cardiac and Vascular Surgery, Deutsches Herzzentrum München, Clinic at the Technical University, Lazarettstr. 36, 80636 Munich, Germany. heimisch@dhm.mhn.de
Insights
Hematocrit (Hct) significantly impacts blood volume measurements using the conductance catheter technique (CCT). Accurate cardiac performance assessment in small animals requires Hct correction of CCT readings to avoid significant volume misinterpretations.
Area of Science:
- Physiology
- Biomedical Engineering
- Cardiovascular Research
Background:
- The conductance catheter technique (CCT) is vital for assessing cardiac performance via pressure-volume signals, particularly in small animal models.
- Blood conductivity, a key factor in CCT, is directly influenced by hematocrit (Hct).
Purpose of the Study:
- To evaluate the interdependence between hematocrit (Hct) and volume measurements obtained by the conductance catheter technique (CCT).
- To determine the necessity of Hct correction for accurate CCT-derived volume readings in small animals.
Main Methods:
- Conducted isovolumic hemodilution in Wistar rats to progressively lower Hct from 50% to 7%.
- Collected blood samples for Hct measurement and conductance catheter volume measurements (CCV) in calibrated cuvettes.
- Analyzed the relationship between relative volume units (RVU) and Hct levels.
Main Results:
- A strong inverse linear relationship was observed between RVU and Hct (r > 0.96, P < 0.0001).
- CCV output increased by 36% as Hct decreased, indicating significant volume misreading.
- Regression line slopes varied with calibration volumes, highlighting the dependence on cuvette size.
Conclusions:
- Direct interdependence exists between Hct and CCV, necessitating Hct correction for accurate volume measurements.
- Even minor fluid substitutions in small animals can cause substantial Hct decreases, leading to pronounced blood volume misreadings.
- Careful Hct correction is crucial for reliable cardiac performance assessment using CCT in small animal research.
Abstract:
Cardiac performance is quantitatively and continuously assessed from pressure-volume signals by using the conductance catheter technique even in small animals. Conductivity of blood, however, is dependent on hematocrit (Hct). Interdependence between hematocrit and volume measurement by the conductance catheter has been evaluated. In 12 male Wistar rats weighing 400-475 g, anesthetized and artificially ventilated, Hct was gradually lowered by isovolumic hemodilution ranging from 50% to 7%. Heparinized blood samples were drawn at decreasing Hct levels for centrifugation, for automated Hct measurement by a blood gas analyzer, and for conductance catheter volume measurements (CCV) in calibrated cuvettes. Substitution of about 2 ml colloid solution lowered the Hct initially from 47 +/- 2% to 36 +/- 3%; at the same time, CCV output rose by 36 +/- 14% for definite blood volume. There is a strong inverse linear relationship (absolute value of r > 0.96; P < 0.0001) between relative volume units (RVU) displayed by the volume acquisition device and the hematocrit for any calibrated blood cuvette. Slopes of the regression lines increase proportionally to the calibration volumes (28.3 microl: -0.25; 63.6 microl: -0.57; 113.1 microl: -0.92). These data document the direct interdependence between Hct and CCV. Consequently, careful Hct correction of the RVU recordings is necessary especially in small animals where even small amounts of substituted solutions result in a marked decrease in Hct and, thus, in pronounced blood volume misreadings.
