Improving patient outcomes

Authored by: Andrew Acker, MD, Marisa Cevasco, MD, MPH, Tsuyoshi Kaneko, MD

There have been several paradigm-shifting breakthroughs in cardiac transplantation since Dr. Christiaan Barnard performed the first orthotopic heart transplant (OHT) in 1967. The current paradigm shift is the use of novel technologies allowing for enhanced organ preservation. They allow heart surgeons to travel further for donor hearts and allow them to utilize donor hearts from deceased circulatory donation (DCD). Here we will review the use of several novel technologies – the Transmedics Organ Care System (OCS), the Paragonix SherpaPak, the XVIVO Heart Assist Transport, and normothermic regional perfusion (NRP).

Transmedics Organ Care System

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The OCS system is a portable, warm-perfusion and monitoring system that can resuscitate, perfuse, and allow for the evaluation of the beating donor heart for greater than four hours making it possible for the transplant teams to expand the donor pool. You can monitor aortic root pressure, coronary blood flow, and lactate levels. To attach the donor heart to the OCS system the SVC and IVC are ligated. There is a reservoir where blood collects from the LV vent and the cannula that is placed in the PA. The blood from the reservoir is pumped through a gas exchanger and a warmer and then returned via a cannula in the ascending aorta. The left atrium is opened. This system was initially FDA approved in extended criteria donors (ECD) that were deemed otherwise unsuitable for transplantation as a result of the EXPAND trial. 

Paragonix SherpaPak

The SherpaPak provides static hypothermic preservation of hearts in a more controlled environment than the cold preservation utilized traditionally, thus preventing both freezing injury that can lead to protein denaturation and irreversible damage to the heart and hypoxic injury if the organ were to get too warm. To attach the donor heart to the SherpaPak system the heart connector and temperature probe are attached to the aorta and the organ cannister is filled with cold cardioplegia. The cannister of the system suspends and cools the donor heart evenly utilizing their proprietary SherpaCool technology - an isolated pressure-controlled cold liquid solution. It continuously monitors the internal and ambient temperatures for the ideal temperature of 4°C to 8°C. Like traditional cold preservation, it's intended to be used for up to four hours. 

XVIVO Heart Assist Transport

The XVIVO system is a hybrid of the previous two systems described in that it is a static hypothermic oxygenated perfusion system. The XVIVO system consists of a heart box, perfusion unit, perfusion solution, and perfusate supplement. The reservoir is primed with the albumin-based hyper-oncotic perfusion solution and O-negative blood. The donor heart sits in the reservoir and the perfusion solution is pumped out through an oxygenator and back into the aorta, which is cannulated. Additionally, there is a LV vent that is placed across the mitral valve. The pressure and temperature of the perfusate is monitored with a goal of 20mmHg at 8°C.  

Normothermic Regional Perfusion

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Normothermic regional perfusion (NRP) is an approach to organ preservation that reanimates the heart in the deceased donor with the use of extracorporeal membrane oxygenation (ECMO) or cardiopulmonary bypass (CPB) and perfuses the donor organs prior to explantation and recovery. The advantage of this approach is that it reduces warm ischemic time and allows for the assessment of the donor organs prior to explantation. Typically, these patients are cannulated via the ascending aorta and the femoral vein or the right atrium before re-establishing circulation the head vessels are clamped or ligated to prevent reanimation of the brain.