To begin set the peristaltic pump's flow to 1.0 milliliters per minute. Weigh the isolated rat's heart and cannula before attaching them to the system. Connect the cannula to the system's connector and start a timer.
Once the heart contracts fully increase the flow in 0.2 milliliters per minute increments while monitoring the pressures, stop increasing the flow when the desired pressures are reached, or when a minimum flow of 3.5 milliliters per minute is achieved. Four pressures between 30 and 35 millimeters of mercury. Set the flow to 4.5 milliliters per minute.
Then start the Adenosine syringe pump. Using a Luer lock connector, connect the catheter to a pressure sensor and secure the entire setup to a clamp stand. After that, attach a small latex balloon to a balloon catheter with a tapered tip.
Using a syringe attached to the top end of the pressure sensor. Fill the balloon, catheter, and pressure sensor with approximately 200 microliters of saline. Then with the help of a sphygmomanometer calibrate the pressure sensor.
Next, make a small horizontal incision above the left atrium. Deflate the balloon by drawing back the syringe at the top of the pressure sensor and inserting it into the left ventricle. Afterward start data acquisition and inflate the balloon until the diastolic pressures indicate zero millimeters of mercury.
A clear correlation was established between heart rate and perfusion pressures. Notably, heart rate was significantly higher in high pressure hearts compared to low pressure hearts throughout the study with the exception of the initial measurement. There was a significant disparity in left ventricular pulse pressure or LVPP between the groups with high pressure hearts displaying statistically higher LVPP across all time points.
Over time high pressure hearts exhibited a progressive decline in function with a noticeable decrease in LVPP after two hours. Conversely, low pressure hearts maintained consistent LVPP throughout the perfusion. High pressure hearts demonstrated superior cardiac function compared to low pressure hearts.
