Cardiac Risk Score—Halfway There

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Jasseron et al described a Cardiac Risk Score (CRS), created from the French National Registry CRISTAL, to predict the risk of death on their cardiac transplant waiting list, or removal because candidates became too ill to transplant within 1 year of listing.1 A Cox proportional hazards model identified 4 factors reported at the time of listing that predicted waitlist death or demise. The French transplant community plans to use this CRS to allocate hearts for transplant. There is substantial impact of geography on allocation in France, first locally, then regionally, then nationally.
A similar approach was used to create the US Lung Allocation Score (LAS),2 which also incorporates predicted 1-year posttransplant survival into allocation, to reduce futile transplants. Inclusion of transplant benefit is the major difference between the LAS and CRS.
Potena and Khush3 note that using candidate characteristics only when listed was a study weakness; we had the same problem with the LAS. Another limitation is that expected posttransplant mortality was not considered. Instead, “access to transplantation will be denied to candidates with an expected 1-year posttransplant survival of 50% or lower,” claiming this is “more pragmatic” than including actual survival probability into their algorithm.
Hearts in the United States are not allocated “primarily based on medical urgency… to candidates at the highest risk of waitlist mortality.” Hearts are allocated to Status 1 patients based on waiting time. Geography plays a critical role in all US organ allocation algorithms, as it does in France. Requiring hearts to be offered to Status 1A recipients within 500 nautical miles before being used locally in 2006 resulted in a substantial decline in US cardiac transplant waiting list deaths (342 ± 30/year [5 years post-2006] vs 541 ± 95 [5 years pre-2006], P < 0.003). More were removed from the list because they were too sick. Significantly more heart transplants were performed (2098 ± 76/year vs 2236 ± 75/year [all mean ± SD], from OPTN data, accessed July 25, 2017). Proposed alterations to the US cardiac algorithm3 will still be based partly on waiting time and substantially on geography. Incorporating posttransplant survival was abandoned because of the “belief that it would take too long to develop and implement”3 was similar to concerns expressed during LAS creation.
The CRS is a major contribution to transplantation in France, and perhaps other countries. The LAS system improved lung transplant in the United States.4 It was adapted by Eurotransplant to distribute lungs between countries. In Germany, the LAS had similar beneficial effects on lung transplant.5
Designing a new allocation system provides a unique opportunity for the French cardiac transplant community to “do it right,” by incorporating both CRS and posttransplant survival, and reducing or eliminating the impact of geography. Ideally, organs should be allocated to the sickest, and avoid futile transplants by incorporating survival. France is small enough that hearts could be transported anywhere with acceptable cold ischemic times; at least eliminating local allocation first. CRS is the first important step toward much better French heart allocation. Adding posttransplant survival and eliminating geography would make it much better.
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