Adult heart transplantation became a reality on Dec. 3, 1967, a date etched into the minds of cardiac transplant surgeons. On that day, Christiaan Barnard was the first surgeon to perform a human-to-human heart transplant.
Since then, evolution and advancements in the procedure have followed periods of intense exciting activity and growth in the field, followed by periods of relative stagnation. I am happy to report that we are currently in a period of growth.
In fact, as seen by the graph below, the number of heart transplants performed per year in the United States was stagnant for almost three decades. The last decade has seen an unprecedented growth with more than 4,500 heart transplant being performed last year.
This growth has been fueled by several important developments over the last several years.
Hepatitis C Donors
Across the U.S., there has been near global acceptance of utilizing hearts from hepatitis C (HCV) donors. Previously, these donors were generally ignored for cardiac transplant due to the risk of HCV transmission.
However, with the advent of curative HCV therapies, hearts from hepatitis C donors are now routinely used. The post-operative management is adjusted to allow for HCV treatment, if needed, based on the donor HCV status and seroconversion in the recipient.
Pre-Transplant Heart Preservation
Since its inception, donor hearts were preserved in ice static storage, aka ice bucket. In the past few years, new organ preservation techniques have arisen, allowing longer ischemic times as well as utilization of more high-risk or marginal donors.
There are two that are worth mentioning. The SherpaPak by Paragonix is a static cold storage system that maintains sterility and a constant temperature for donor heart preservation. The system keeps the heart suspended in a bath of preservation solution, which is maintained at an optimal temperature between 4 and 8 degrees Celsius to prevent freezing tissue injury. Recent reports have documented excellent graft function after preservation of hearts > 7 hours in this system.
Another preservation system in use is the Transmedics OCSTM, which is a warm perfusion system that uses blood to maintain a beating heart during travel. This is essentially what we refer to as a heart in a box model with a beating heart being perfused with warm, oxygenated blood.
The major advantage of this system is the potential for very long ischemic times. This of course is in quotes, as the heart is actually being perfused and as such, not truly ischemic.
Nevertheless, using the time from donor cross-clamp to recipient cross-clamp off has been the standard for measuring organ ischemic time. With this system, some isolated transplants have been performed with excellent outcomes with > 10 hours of ischemic time. Other advantages of the system include the ability to measure biomarkers in the blood (such as lactate) and the potential for transplantation of a beating heart into a recipient without re-stopping the heart.
Normothermic Regional Perfusion (NRP)
As is commonly known in the medical field, there are two types of organ donors. The first, and most widely used, are donation after brain death, or DBD. These have been the only donors we have utilized for decades.
However, recently, donation after circulatory death (DCD) donors have emerged as potential donors even for cardiac donation. It may seem counterintuitive that one would want to use a heart from a donor suffering cardiac death. However, data has shown, and continues to show, that these hearts perform just as well as DBD hearts.
The preservation technique for this approach is very similar to NRP. Once the donor is declared dead by cardiac standards, there is a 5-minute stand-off period. Subsequently, the chest is opened, and the head vessels are clamped. The donor is then placed on central Extracorporeal Membrane Oxygenation (ECMO), and the heart is reanimated.
There is a period of cardiac rest or recovery that then ensues. After that requisite period, the donor is weaned off ECMO and if the heart has acceptable function, it is procured per standard techniques.
Current estimates suggest that widespread adoption of this technique may lead to 10%-20% increase in heart recovery from the existing donor pool.
Xenotransplants
The panacea of transplant has always been, and likely always will be, xenotransplant. While the first attempts at heart xenotransplant date back to the 1960s, little to no progress has been made on that front.
That is until early 2022 when a patient at the University of Maryland underwent xenotransplant with a pig heart. Unfortunately, that patient only survived for two months. But even that was enough to reignite enthusiasm on this front.
The major limitations of this approach reside on the genetic difference between human and pig tissue. The number of potential sites of immune activation are enormous and likely will take another decade (or more) to discern and control. But there is hope.
All of these techniques have led to a resurgent energy in cardiac transplantation. As an aging cardiac surgeon, I am hopeful that these techniques will aid us in making serious dents into the waitlist of cardiac transplant patients. In addition, I hope these new technologies continue to improve patient outcomes, reduce hospital length of stay and make cardiac transplants more cost effective.
But most of all, I am hoping these technologies will allow for cardiac transplantation to become an elective, 8 a.m. case, rather than an overnight procedure. This too will allow for even better outcomes for our patients and improved longevity of surgeons.
This is an exciting time in the surgical treatment of heart failure. In the past, advanced heart failure had limited options, mostly medical in nature. With the improvement in heart preservation techniques, utilization of more donors and even new technologies in artificial hearts, the discussion of curing advanced heart failure with surgical strategies can finally come to reality.
We are in an era of immense growth in the field that is likely to continue for at least the next decade. It is an exciting time indeed!
Sagar Damle, MD
Dr. Damle is a cardiac surgeon at Piedmont Atlanta Hospital. Dr. Damle’s practice encompasses the entire array of adult cardiac surgery but focuses on heart transplantation and left ventricular assist device implantation.
Karolis Bauza, MD
Dr. Bauza is one of Piedmont Hospital’s newest cardiac surgeons, having joined the program from the Cleveland Clinic. Dr. Bauza’s practice encompasses the entire array of adult cardiac surgery but focuses on heart transplantation and left ventricular assist device implantation.
Ezequiel Molina, MD
Dr. Molina is a cardiac surgeon specializing in heart transplantation and the surgical treatment of heart failure. He serves as the Surgical Director of the Samsky Advanced Heart Failure Center at Piedmont Hospital.
