What Do New Trends in Allocation Rules Mean for Heart Transplant Patients?

What Do New Trends in Allocation Rules Mean for Heart Transplant Patients?

April 2020

Patients spend anywhere from days to months to years on the heart transplant waiting list—and many who have advanced heart failure need mechanical circulatory support in order to survive during that time. Several different devices exist for this purpose, and the choice of device generally depends on the patient’s clinical needs. However a 2018 rule change in the U.S. may have affected how U.S. transplant centers choose between devices when a patient is first listed for heart transplant; in a new paper in JAMA Cardiology, researchers investigated this question.

In October of 2018, the Organ Procurement and Transplantation Network (OPTN) changed how we prioritize patients for heart transplantation in the U.S. to make sure the sickest patients were prioritized first. Patients supported by an LVAD (left ventricular assist device), who have been living longer and longer over the years with technological improvements, are now almost always listed at lower-priority tiers than they were previously. Conversely, those supported by VA ECMO (veno-arterial extracorporeal membrane oxygenation), which is used for only very short time windows in the sickest patients, continue to be listed initially at the top tier. The authors showed that, under the new transplant rules, fewer patients are being listed for transplant on LVAD while a growing number of patients are being listed on VA ECMO.

The discovery implies that choice of device is likely influenced in part by allocation incentives, say the authors. “This is occurring in spite of stringent criteria that are in place to justify the use of VA ECMO as a bridge to transplant,” comments co-lead author Dr. Thomas Hanff, MD, MPH, a cardiovascular disease fellow at Penn and a student in the CCEB’s Master of Science in Clinical Epidemiology program. “And we don’t yet fully understand what the downstream clinical implications of changing device strategies will be.”

The authors conducted a retrospective analysis of all adult patients in the OPTN registry listed for isolated heart transplantation from January 1, 2014 to June 30, 2019, excluding re-transplantation. They used a powerful modeling strategy called Interrupted Time Series Analysis, which is sometimes referred to as a "Quasi-Experimental" design—in essence, when a randomized trial can't be performed, these types of designs are often considered the next best thing.

The results suggest that initial support platforms are being used somewhat interchangeably in sicker patients, but it is not clear if outcomes will be affected by greater VA ECMO use and less LVAD use. “These changes could be detrimental to waitlist or post-transplant outcomes if lower-acuity patients are prioritized for transplantation, or if VA-ECMO support in the pre-transplant period is itself directly harmful compared with LVAD,” the authors write. “The increased number of allocation tiers is a major benefit of the new rules, and we expect that wait times and waitlist survival should be improved,” added Dr. Hanff. “At the same time, we have to continue to evaluate for any unintended consequences of the new system that may have an impact on outcomes.”

Read the paper in JAMA Cardiology.

Authors: 

Authors: Thomas C. Hanff, MD, MPH; Michael O. Harhay, PhD, MPH; Stephen E. Kimmel, MD, MSCE; Maria Molina, CRNP, MSN; Jeremy A. Mazurek, MD; Lee R. Goldberg, MD, MPH; Edo Y. Birati, MD

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