Synchronous biventricular pressure‐volume loops in rodents using a closed‐chest approach

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 catheterization 1 . 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 models 2 . 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).

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