Approximately 250,000 patients in the U.S. die from advanced heart failure each year. Cardiac transplantation is the most successful treatment for end stage heart failure, but total transplants in the U.S. number only 2200 a year. Currently, only one of every four donor hearts is used for transplant. Declined donor hearts fall into two categories: i) marginal donor (MD) hearts with borderline ventricular function and ii) hearts donated after cardiac death (DCD). Clinicians fear that transplantation of MD and DCD hearts will result in a high incidence of primary graft dysfunction and death of the recipient though ther is growing evidence for potential use of these donor hearts. Without better methods for evaluation as well as better preservation strategies, MD and DCD hearts will continue to be excluded for transplantation, and heart failure patients will continue to die awaiting a heart. Our long term goal is to expand the donor pool of hearts by developing more accurate evaluations of donor hearts and improving their preservation. Our objective in this proposal is to develop a clinically relevant and reliable protocol that can predict functional recovery of a heart after reperfusion by assessing the heart while in preservation storage. We propose that by perfusing the donor heart and assessing the content of the biomolecules in the perfusate, we will be able to obtain a snapshot of the relative health or dysfunction of the heart non-invasively, in a clinically relevant time frame. Cold static storage, the current standard of care for heart storage does not lend itself to this approach because the storage solution is not exposed uniformly to all aspects of the heart. Through our collaboration with Organ Transport Systems (OTS), the developer of the LifeCradle (LC) cardiac perfusion device, we are currently one of only two academic laboratories in the US with access to the LC and experience in its utilization. Further, through interactions with our local organ procurement organization, we have acquired unused human hearts, placed them onto the LC, and acquired and analyzed perfusate samples. Our preliminary data point to our ability to detect cardiac injury biomarkers, the relative levels of these biomarkers and rates of change during perfusion storage of human hearts in the LC system. We can also determine whether treatments administered to the heart during perfusion storage are useful in minimizing preservation injury and rendering these hearts suitable for transplantation. We will test these concepts in the following two aims:
Specific Aim 1 : To test the hypothesis that the concentration of cardiac injury biomarkers in the perfusate from continuous cold perfusion storage can accurately predict left ventricular functional recovery.
Specific Aim 2 : To test the hypothesis that a novel cardiac preservation strategy will reduce cardiac injury biomarkers during preservation that will correlate with greater functional recovery post-reperfusion. The development of novel methods to evaluate the heart during the storage process and methods to mitigate injury, will ultimately enable clinical use of marginal donor and perhaps even DCD donors, thus expanding the overall cardiac donor pool in the U.S.
The proposed research is relevant to public health because a better understanding of the relative health and dysfunction of unused donor hearts will lead to new strategies to increase their usability and to enable more heart transplants which are currently limited by donor supply. Thus, the proposed research is relevant to the part of the NIH's mission that pertains to fostering fundamental creative discoveries and innovative research strategies to reduce the burdens of illness and disability.