In left ventricular assist device era, transplant priority system needs refinement

Seattle, WA - "Many patients on ventricular-assist-device (VAD) support are at such low risk of adverse events that they ought not to be in the highest-priority category for a new heart, according to the authors of a new study published in the July 3, 2012 issue of the Journal of the American College of Cardiology [1].

The current rules of the Organ Procurement and Transplantation Network (OPTN) allow transplant candidates on mechanical support to be placed into the 1A category (highest priority for a donor heart) for 30 days at the transplant center's discretion at any time after the VAD is implanted. Over the past decade, survival rates with implanted left ventricular assist devices (LVADs) have become steadily better as the devices have become more reliable. 'Because LVADs are used more commonly, there is a growing belief that placement of an LVAD is necessary for successful transplantation,' Dr Todd Dardas (University of Washington, Seattle) and colleagues explain. 'Increasing numbers of stable, VAD-supported patients listed status 1A may prevent organ allocation to sicker patients, decreasing survival among those waiting for transplant and leading to an overall reduction in the efficacy of the transplant urgency system.'

Dardas et al analyzed nearly 12 000 patients listed in OPTN status 1A and over 13 000 in status 1B from 2005 to 2010 in the Scientific Registry of Transplant Recipients. They estimated the relative and absolute risk of adverse events—either death or delisting because the patient became too ill—during the time the patients were in status 1A or 1B.

Status 1A registrants on dual inotropes and right heart monitoring had a higher risk of adverse events (hazard ratio 3.2) than patients with implanted LVADs who were in their 30-day window of elective 1A time. The 30-day risk of events was 1% for LVAD patients using their elective 1A time and 6% for patients on dual inotrope support. Patients supported by a paracorporeal ventricular assist device had a higher risk of adverse events (hazard ratio 9.1; p<0.0001) than patients supported by LVADs using their elective 1A time. However, despite their apparently lower risk, the odds of an LVAD patient getting a heart transplant were higher (odds ratio 1.5; p<0.0001) than for patients on dual-inotrope therapy and intra-aortic balloon pump support.

 

We'd like to know . . . who is competing for that organ?

Dardas believes that stable patients with an LVAD should not be categorized as status 1A as long as their devices are working without complication. These patients should be listed as 1B, he told heartwire. 'By the same token, patients who have paracorporeal devices—who are currently treated the same as a patient with an implanted device—could probably all be status 1A as long as they have that device in.'

Dardas said his group is also researching how centers make decisions about their patients' OPTN statuses. 'It doesn't appear that people are commonly given this 30-day elective 1A time in the setting of someone else who is probably sicker at their same center or organ-provision organization [OPO]. But we'd like to know more about when the organs are shared outside of OPOs. We'd like to know, from the standpoint of an organ that is available, who is competing for that organ,' he said. 'Are there patients listed as 1A at one center that another center might not know about who are competing for the same organ as someone with an implanted [LVAD]?'

Who gets what, and when

In an accompanying editorial [2], Dr Sean Pinney (Mount Sinai Medical Center, New York, NY) says that he is not convinced by the study by Dardas et al that patients on LVADs are getting donor hearts ahead of patients who need them more urgently.

He points out that although Dardas et al have found wide disparities in risk among different types of patients in status 1A, there is still no direct evidence that prioritizing stable LVAD patients has prevented any other 1A patients from receiving a timely transplant. Organ wait-list mortality is actually declining, and 'it is likely that centers are exercising good judgment by timing these upgrades to avoid competition with other 1A patients, thereby preserving their exposure to donor hearts,' he says.

He also argues that not allowing LVAD patients to have 1A status, as the rules are currently set up in Europe, effectively eliminates the chances of an LVAD patient getting a transplant unless they have a major complication. So this may create an incentive for those patients to deliberately stay on medical therapy alone without an LVAD in order to increase their chances of getting a transplant while also increasing their chances of dying while they wait for one.

Pinney argues that no organ-allocation system will ever be able to eliminate all disparities in risk within each category, but he agrees with Dardas et al that the current system needs refinement to acknowledge that newer LVADs are 'minimizing the risks of mechanical support and maximizing its beneficial outcomes.' One option would be to create a heart allocation score, similar to those used for lungs or livers, or to expand the list of prioritization categories to match individual risk profiles. 'Regardless of which system emerges, facilitating this change will require robust data collection and analysis,' he concludes."

http://www.theheart.org/article/1419529.do