SAN DIEGO – A new allocation algorithm that is designed to improve regional sharing of donor hearts with sicker patients before they are allocated locally to less-sick patients appears to be having the intended effects, according to a national cohort study.
In the study of nearly 12,000 adult patients who were wait-listed for primary heart transplantation in 2004-2009 in the United States, those who were wait-listed after the new algorithm was implemented were 17% less likely to die on the waiting list or to become too sick for transplantation, Dr. Tajinder P. Singh reported at the meeting.
Moreover, this benefit was achieved without any increase in the rate of in-hospital mortality in transplant recipients, even though they were sicker on average.
“The risk of dying on the heart transplant [waiting list] or becoming too sick for transplant has declined since the change in allocation algorithm in 2006,” said Dr. Singh, a pediatric cardiologist at Children's Hospital Boston. And reassuringly, “the shift in hearts to sicker transplant candidates has not resulted in higher early posttransplant mortality.”
These findings suggest that the new algorithm has been effective “not only from a utilitarian view, which means most benefit for most people, but even from the fairness or justice perspective,” he commented, because the hearts are goint to sicker people.
“The demand for donor hearts continues to exceed their supply,” he said, giving background to the study. “The United Network for Organ Sharing has periodically modified the allocation algorithm in the United States” to improve waiting list outcomes.
The last such modification, implemented in July 2006, expanded the sharing of these scarce organs across a geographic region, making them available first to the sickest patients (those with status 1A or 1B) in a region before allocating them locally to less-sick patients.
The investigators studied all patients aged 18 years or older who were placed on the waiting list for primary heart transplantationbduring July 1004, ane 30, 2009, and who were undergoing transplantation of only a heart.
For comparison, the patients were split according to when they were listed into “era 1” (before the date of implementation of the new algorithm) and “era 2” (after that date). Study results were based on 11,864 patients in total; 38% were listed in era 1 and 62% were listed in era 2.
Patients in the two eras were similar with respect to most sociodemographic and medical factors, except that those in era 2 were more likely to be aged 60 years or older (32% vs. 28%), to receive mechanical support (14% vs. 13%), and to be sicker, as indicated by having a transplantation status of 1A (20% vs. 19%) or 1B (38% vs. 32%), for instance.
Overall, 13% of the patients studied either died or had a worsening of their condition that prevented transplantation while they were on the waiting list, the study's primary end point, Dr. Singh reported.
Before statistical adjustment, patients in era 2 were 14% less likely than those in era 1 to die or worsen while on the wait list (hazard ratio, 0.86). And this benefit was evident in both status 1A patients and status 1B patients individually.
After adjustment for numerous potential confounders, patients in era 2 were 17% less likely to die or worsen while on the wait list (HR, 0.83). This significant benefit was similar in most subgroups, except that by race, it was mainly limited to white patients.
Other risk-reducing factors included having an implantable cardioverter defibrillator (HR, 0.87) and having a continuous-flow left ventricular assist device (HR, 0.56).
Overall, 65% of the patients ultimately underwent transplantation. Compared with those in era 1, era 2 transplant recipients had a significantly shorter median wait time before receiving a heart (55 vs. 63 days) and were more likely to be status 1A at transplantation (48% vs. 37%).
Dr. Singh reported having no conflicts of interest related to the research.