Where the Heart Goes: Transplant Community Tackles Tough Choices to Achieve Equitable Organ Sharing

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The law of supply and demand translates into life and death for thousands of people in the United States who are desperate for a new heart. Because of a severe shortage of organs to meet the growing need, some 350 people died last year while waiting for a heart transplant. Aware of the inequities and disparities in the current system of adult heart allocation, the Organ Procurement and Transplantation Network (OPTN) and United Network for Organ Sharing (UNOS) have proposed significant changes that are being debated by the transplant community. Will the new rules provide a fresh lifeline for the sickest of the sick, or simply add another layer of complexity and cost to a system that struggles to achieve fairness and efficiency?

Cracks in the nation’s program for organ sharing have grown deeper and more disturbing as the number of candidates for a heart transplant has soared in recent years. Take, for example, a patient with ventricular arrhythmia in New York City who is given months to live without a new heart. Suddenly, a suitable organ becomes available from a trauma victim just across the Hudson River, in Newark, N.J. The distance between the two might as well be the Atlantic Ocean since the heart is offered instead to a less urgent, relatively stable candidate who happens to reside closer to the heart donor. Chalk that decision up to current OPTN/UNOS rules governing the geographic sharing of organs—rules that favor less needy candidates in the local donation service area (DSA) vs. patients on the brink who might live 25 miles away but, sadly, outside the relatively small DSA.

Source: Thoracic Organ Transplantation Committee. National Webinar: Proposed Modification of the Adult Heart Allocation System (https://www.transplantpro.org/news/education/heart-allocation-system-web...), presented Feb. 2, 2016; reprinted with permission of Organ Procurement and Transplantation Network and United Network for Organ Sharing.
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Other imperfections in the system have surfaced with the increased use of mechanical circulatory support devices (MCSD). According to OPTN/UNOS, nearly 36 percent of heart transplant candidates were registered while on these devices in 2014, up from 16 percent in 2007, resulting in “more complications…often requiring urgent transplantation.” In the view of many, however, the heart allocation system has failed to keep pace with technology through better stratification of candidates based on the type of MCSD support they have and the risks associated with specific device complications. Not surprisingly, status 1A (the most urgent) candidates supported by mechanical ventilation or extracorporeal mechanical oxygenation (ECMO) have the highest waiting list mortality rates, up to 36 percent.

These deficiencies and others have not been lost on OPTN and UNOS, which jointly manage the unified organ transplant network for the U.S. Department of Health and Human Services. For the first time since 2006, they have proposed sweeping changes to the adult heart allocation system designed to improve its equity and access by patients across the country. “The practice of medicine has changed in the last decade, and we now have a better idea how to risk-stratify patients and help the sickest people get transplanted quicker by offering them organs from a broader geography,” says Joseph Rogers, MD, interim chief of the Division of Cardiology at Duke University School of Medicine, and chair of the OPTN/UNOS Thoracic Organ Transplantation Committee, which drafted the proposed heart allocation guidelines. “Our modeling suggests that we can reduce for patients the risk of either dying while on the transplant waiting list or being removed from it because they became too sick to be successfully transplanted.”

A new stratification formula

To improve timely access to transplantation by the sickest on the waiting list, OPTN/UNOS has developed a new status hierarchy along with more liberal sharing of organs between geographic zones. Specifically, the guidelines would replace existing statuses 1A, 1B and 2 with a numbered scheme, 1 through 6, based on medical urgency. The notion behind increasing the number of statuses is to allow for better stratification of heart transplant candidates as well as quicker movement up or down the prioritization scale as the patient’s condition worsens or improves. To facilitate broader organ sharing, the proposed rules recommend that statuses 1 and 2 be given first consideration when a suitable donor heart becomes available. Thus, the most urgent candidates within the donor hospital’s DSA would have top priority, as the current system mandates, but the next in line would no longer be a less needy 1B candidate within the DSA. Instead, the heart would be offered to a status 1 or 2 patient within surrounding Zone A, then Zone B (which extend 500 miles and 1,000 miles, respectively, from the donor hospital).

“We have a mandate to make the best use of a scarce resource,” emphasizes Rogers, “and we believe this new system accomplishes that by giving [transplant] centers an opportunity to look at organs further away from very sick people.”

The expanded range, however, also may have a downside—one that could impact the cost, effectiveness and operational logistics around heart implantation. A large part of the issue revolves around ischemic time—the amount of time a donor heart in transit can be preserved outside the body through static cold storage, the current standard of care. Ischemic time is roughly four hours. Thus, distribution of a donor heart to a transplant center three or four hours away “may increase the time the organ would be nonviable, and could potentially lead to increased risk of post-transplant mortality,” warns Robert Higgins, MD, director of the Comprehensive Transplant Center at Ohio State University College of Medicine, and treasurer of The Society of Thoracic Surgeons (STS), which is involved in the discussion of the proposed allocation changes. 

Another “trade-off” with broader organ sharing is the issue of finances, adds Higgins. “It’s certainly more costly to use a Lear jet to transport a heart four hours from point A to point B than it is by ambulance within a local region,” he points out. Rogers, with OPTN/UNOS, also is mindful of the potential “operational complications” from greater distance sharing, such as timely arrival of transplant teams to hospitals and completion of necessary donor–recipient graft matching within the required window. “There is always the potential for adding to the overall cost of transplantation,” he says, “but that has to be weighed against reducing the risk of dying for the very sickest people on the waiting list.”

Source: Thoracic Organ Transplantation Committee. National Webinar: Proposed Modification of the Adult Heart Allocation System (https://www.transplantpro.org/news/education/heart-allocation-system-web...), presented Feb. 2, 2016; reprinted with permission of Organ Procurement and Transplantation Network and United Network for Organ Sharing.
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The challenge of ECMO

ECMO is another sharp-edged issue among transplantation professionals. While no one disputes the life-sustaining advantages of this device while a patient is waiting for a heart, there are concerns over assigning it the highest status (along with mechanical ventilation, non-dischargeable BiVAD or RVAD and MCS for life-threatening ventricular arrhythmia). In a March 2016 letter to UNOS, the STS argued that “without requiring medical justification to limit the use of ECMO as a bridge to transplantation, we fear this strategy will have a significant adverse effect on both wait-list mortality and post-transplant mortality.” That fear is rooted in the belief that the new guidelines would drive even greater numbers of physicians to use ECMO over other MCS options that “exist in the overwhelming majority of cases.”

ECMO also comes with a cost. “It becomes very expensive at a time when we need to find ways to deliver healthcare cheaper and more efficiently,” observes Aditya Bansal, MD, a transplant surgeon with Ochsner Health System in New Orleans, where between 70 and 80 percent of heart waiting list patients depend on MCS, including ECMO. “It also brings a significant potential and bias for rigging the system to your needs.”

What Bansal and others favor in lieu of adding more statuses is a heart allocation score (HAS) based on a patient’s health, waiting time and medical urgency. While the OPTN/UNOS Thoracic Organ Transplantation Committee in fact studied and acknowledged the potential benefit of such a system, it opted to shelve HAS for now out of concern it might not have the flexibility to accommodate rapidly changing technology. 

Source: J Am Coll Cardiol 2012;60:36-43; reprinted with permission.
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The potential of warm blood perfusion

Beyond hierarchical schemes, the future of organ allocation could be impacted by a promising innovation: warm blood perfusion systems that extend the time for safe organ transport. Indeed, the limitations of current cold ischemic storage are evidenced by the fact that two-thirds of donor hearts and lungs are never used, according to the ECRI Institute, because the process of harvesting, preserving and transporting can damage their suitability. One device under clinical review, the OCS Heart System (TransMedics) perfuses harvested organs with a warm blood-based solution that replenishes oxygen and essential nutrients. The system also allows for constant clinical evaluation.

“Hopefully, this device will expand the donor pool and therefore provide more hearts to patients on the waiting list who might otherwise die,” notes Fardad Esmailian, MD, a principal investigator for the International EXPAND Heart Pivotal Trial and surgical director for the heart transplant program at Cedars-Sinai Medical Center in Los Angeles, which is studying the effectiveness of OCS Heart. But the cost of the device—$250,000 for the portable console and about $45,000 for each single-use perfusion module—could be a major obstacle for many hospitals (harvesting a donor heart for transplantation using conventional cold-storage is estimated at $70,000, according to the ECRI Institute).

While the EXPAND trial proceeds at 15 sites worldwide, OPTN/UNOS also is engaged this summer reassessing and reworking sections of its heart allocation proposal based on concerns voiced by the public.  A revised document is expected this fall for further discussion.      

“This is a good-faith effort to try and enhance the basic principles of saving lives of people waiting for transplants,” says the STS’s Higgins of the OPTN/UNOS initiative. But with 4,211 heart candidates on the waiting list as of December 2015, he hastens to add, “The only thing that will really save more lives is more organs available for transplantation. Without that, we have to make choices—and those choices are often difficult.”