Introduction: The assessment of left- and right-sided cardiac function via closed-chest pressure-volume loops is important to understanding and diagnosing a wide range of cardiovascular pathologies. In the vast majority of pre-clinical studies, either left- or right-sided heart function is assessed in isolation, or, more recently, by sequentially right- and left-sided catheterization1. Synchronous biventricular catheterization would offer a significant advancement for pre-clinical research. To date, closed-chest synchronous biventricular pressure-volume loops have only been obtained in a few studies, limited to porcine models2. Here, we describe initial results from what we believe to be the first synchronous biventricular pressure-volume loops obtained in the rodent using a closed-chest approach.
Aim: To obtain biventricular pressure-volume loops in the anesthetized rat using a closed-chest approach
Methods: A total of 8 Wistar rats were anesthetized with urethane (1.5mg/kg), tracheotomised, ventilated, and subsequently had a solid state catheter placed in the femoral artery to measure blood pressure, and admittance pressure-volume catheters placed in the right- and left-ventricle to obtain synchronous biventricular pressure-volume loops. Admittance probes were set to different frequencies to avoid cross-talk. All catheters were left to stabilize for a minimum of 10 min after which we extracted and averaged 1 minute of basal pressure-volume indices.
Results: Reliable ventricular pressure waveforms were obtained from both the left (i.e., left-ventricular end-systolic pressure = 106±12mmHg) and right (i.e., right-ventricular end systolic pressure = 28±8mmHg) side in all eight animals, and we were able to obtain standard left-sided pressure-volume loops from all eight animals (i.e., stroke work = 22±5mmHg/ml). We were only able to obtain reliable right-sided pressure-volume loops in two of eight animals, due to poor volume signals in the remaining 6 animals. In the two animals we were able to obtain synchronous pressure-volume loops there was clear evidence of ventricular dependence across the respiratory cycle (Fig.1).
Conclusions: Obtaining synchronous biventricular pressure-volume loops using a closed-chest approach in rats is possible but technically challenging. Further work is needed to better obtain right-sided ventricular volumes.
References: Potus F. et al., J. Vis. Exp (160), e61088, doi:10.3791/61088 (2020). Lyhne MD. et al., J. Vis. Exp.(171), e62661, doi:10.3791/62661 (2021).
We acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC), [RGPIN-2020-06240]
Fig 1. Left- and right-ventricular (LV/RV) pressure-volume (PV) traces along with arterial blood pressure (BP) over time. Note the significant ventricular dependence in the LV-RV volume traces. Also shown is an inset segment of four PV loops for both the LV (tall) and RV (short).
