Medicine
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Functional Assessment of the Donor Heart During Ex Situ Perfusion: Insights from Pressure-Volume Loops and Surface Echocardiography
Chapters
Summary October 11th, 2022
A reliable noninvasive approach for functional assessment of the donor heart during normothermic ex situ heart perfusion (NESP) is lacking. We herein describe a protocol for ex situ assessment of myocardial performance using the epicardial echocardiography and conductance catheter method.
Transcript
Hemodynamic assessment of the heart during isolated Ex situ perfusion is poorly described. This protocol provides a method to evaluate Ex situ cardiac performances in working mode. Our approach co compares invasive PV loop technique to epicardial echocardiography for functional assessment of their heart during isolated Ex situ perfusion.
This approach requires a team experience in Ex situ heart perfusion, along with involvement of a cardiologist trained for transoeosphageal echocardiography. A major concerns in heart transplantation is the risk of primary graft failure. Our approach using epicardial echocardiography provides an assessment of the heart before transplant during Ex situ perfusion.
This non-invasive method could be written applied during Ex situ heart perfusion prior to transplant. Begin by placing four zero polypropylene sutures on the right atrium and on the ascending aorta of the anesthetized animal to secure cannulation with tourniquets. Infuse heparin and carefully dissect the aortic root.
Then insert a double staged venous cannula in the right atrium for blood collection and a single lumen cannula in the ascending aorta for cardioplegia infusion. After isolating the superior and inferior vena cava connect the venous cannula to a blood collecting bag containing 10, 000 units of unfractionated heparin. Place the piglet body in the Trendelenberg position to improve blood drainage into the collecting bag.
Proceed to heart procurement keeping two centimeters of the pulmonary trunk along with the left atrium posterior wall. Place the heart in a four degree Celsius saline solution and separate the ascending aorta from the pulmonary trunk. Verify that the aortic valve and the coronary ostea are not injured.
Insert four pledged four zero polypropylene stitches, five millimeters below the distal section of the ascending aorta and insert the infusion cannula into the aorta. Tighten a hose clamp around the aorta to secure the cannula. Insert a drainage cannula into the pulmonary trunk and secure it with a three zero polypropylene running suture.
Close the inferior and superior vena cava with five zero polypropylene running sutures. Close the left atrium posterior wall with a four zero polypropylene running suture. Insert a left vent cannula through the posterior wall of the left atrium and snare a tourniquet around.
Insert a preloaded cannula into the left atrial appendage and snare a tourniquet around. Decrease the pump flow to 200 milliliters per minute. Connect the heart to the aortic connector after de-airing the connector.
Adjust the aortic pressure to 30 millimeters of mercury at room temperature. During resuscitation, perform a smooth cardiac massage until a sinus rhythm is restored. Slowly increase the pump flow within 15 to 25 minutes by steps of 50 milliliters per minute to achieve an aortic pressure of 65 millimeters of mercury.
At the same time, increase the profused temperature by steps of two to four degrees Celsius to reach 37 degrees Celsius. Once the required aortic pressure and profuse a temperature is reached deliver an electric shock at five joules if needed and repeat until the sinus rhythm is restored. Secure an epicardial electrode to the right ventricular posterior wall and connect to an external pacemaker.
Then connect the pulmonary cannula to the coronary flow line. Open the preload line and adjust the pump flow to ensure stable filling of the preload reservoir. Open the aortic afterload line and clamp the main line of the circuit used for Langandorf perfusion.
The afterload reservoir will be progressively filled up. Ensure the drainage of the reservoir by an overflow line which brings the profused back to the main reservoir of the circuit. Initiate the infusion of dobutamine at 0.04 milligrams per minute.
Then remove the vent. Clean the seven French pigtail conductance catheter with saline solution and connect it to the hardware interface. Gently push the catheter into the introducer 8 French sheath previously inserted through the left atrium roof to be aligned with the mitral valve.
Stop epicardial pacing of the heart to avoid interference with the conductance signal. Record data in a steady state when the signal is stabilized. Select a series of 10 consecutive loops and open the analysis software.
To obtain the end systolic and end diastolic pressure volume relation, record the signal during preload occlusion. Gradually clamp the atrial profusion line until preload reduction is effective. Then slowly release the clamp.
After placing a sterile drape around the heart apply the probe to the upper wall of the left atrium and manually rotate the transducer until a four chamber view is obtained. Then run the ultrasound probe monitor to obtain three and two chamber views. To assess the MWI proceed to the acquisition of four, three, and two chamber views and record simultaneous arterial pressure.
Assess the global longitudinal strain using these views and open MWI software. Use the invasive blood pressure detected by the external sensor on the perfusion circuit using loop acquisition. Manually notify the software of the exact opening and closing times of the aortic and mitral valves.
Echocardiographic assessment during working mode perfusion was performed in the custom setup. All three left ventricular views were obtained at any time point in all experiments. Mean left ventricular ejection fraction global longitudinal strain and M W I was approximately 40.8%minus 8.0%and 65 millimeters of mercury respectively.
Hemodynamic parameters were assessed by either conductance catheter or surface echocardiography during work mode perfusion. During the work mode perfusion a significant decrease was observed in M W I over time in all experiments. A similar decrease was observed in the cardiac output and other parameters related to the end systolic pressure volume relationship.
The echocardiographic probe has to be located on the roof of the left atrium. Stable requisition of at least three to six myocardial cycles must be performed correctly. A metabolic assessment of the myocardial tissue and the endothelial function would bring a complimentary evaluation of the heart graft during ex situ heart perfusion to optimize perfusion settings.
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