ISHLT Response to OPTN Continuous Distribution of Hearts
Published 24 September 2024
ISHLT Level of Support:
Support the Policy
Read the OPTN Comment
The International Society for Heart and Lung Transplantation (ISHLT) appreciates the opportunity to provide feedback on the “Continuous Distribution of Hearts” OPTN public comment. The International Society of Heart and Lung Transplant (ISHLT) supports the prioritization of attributes provided through the values prioritization exercise (VPE) as part of the development of a continuous allocation framework for donor hearts with a few exceptions.
We noted this is an ongoing, large-scale initiative, building on feedback from the previous proposal. Hence, it would be difficult to provide specific insights into the exact framework without seeing how points are allocated across the various attributes and sub-attributes. ISHLT is looking forward to reviewing next iterations once modeling of the point system to optimize allocation priorities has been finalized and results are accompanied by real-world examples to assess the impact of the proposed continuous distribution algorithm on key allocation metrics.
ISHLT is concerned the weight of the wait time attribute, especially for LVAD recipients, might deserve a higher consideration than the VPE results suggest. We strongly support the previous mention of an annual increase in percentage points for time with an LVAD. This is important for LVAD patients who have had multiple adverse events (stroke, GI bleed, infection, pump malfunction), as survival beyond 1 year post LVAD decreases as the number of these adverse event episodes increases. For each episode of stroke, infections and device malfunction within the first 3 years of LVAD support, there is worse extended survival.1 Therefore, as the Committee models potential approaches attribute weighting, it will be important to ensure that waiting time or a comparable measure of LVAD adverse event impact on waiting list mortality is included in models.
Regarding the proposed attributes, they appear comprehensive for an initial iteration, with the understanding that future revisions will be necessary. The general time interval for review and revision for future iterations should be provided. The decision to exclude post-transplant survival is reasonable, given the absence of an accurate predictive model and the desire to avoid double-penalizing certain groups. However, it would be desirable to work on current era risk prediction models for future iterations of the continues allocation system for both wait list and post-transplant survival.
ISHLT reiterates the importance of a reevaluation of the current medical urgency tier designations. The existing system may place undue emphasis on the use of temporary mechanical circulatory support devices. To better reflect true medical urgency, a revised approach should be considered — one that relies more heavily on objective measures of disease severity. This could involve greater reliance on physiological measurements, serum biomarkers, and laboratory markers, acknowledging trends might have a higher relevance than isolated snapshots in time.
As mentioned in our feedback from the previous public comment period, we ask the committee to consider incorporation of risk models when developing the medical urgency attribute in future iterations of the continuous allocation. One such example is the US-Candidate Risk score. This model has significantly higher sensitivity for predicting waiting list death than the current 6 status system.2
One significant consideration is the prioritization of placement efficiency and the distance between the transplant center and the donor hospital. Although distance was not highly weighted in stakeholder reviews, it has historically been a key attribute for ensuring equity and carries implications for smaller programs. Smaller programs may lack resources necessary to operate ex-vivo perfusion platforms or need to be more conservative to preserve outcomes given their smaller volumes. Therefore, the proposed system must be careful to avoid inadvertently disadvantaging smaller programs, creating a two-class system and ultimately limiting access to cardiac transplant in certain regions.
How changing the weight of the proximity factor will impact post-transplant outcomes (for more vulnerable heart allografts) and overall costs for the transplant centers is not entirely clear and should be explored in more detail before determining the weight of the travel time attribute and balanced with the goal to provide broader access to donor hearts for the most urgent cases.
ISHLT recognizes that de-prioritization of the proximity factor will affect the overall costs of performing cardiac transplant and would require the development of new payment models that take into account travel costs and the use of organ preservation devices.
- Hariri, I. M., Dardas, T., Kanwar, M., et al. Long-term survival on LVAD support: Devicecomplications and end-organ dysfunction limit long-term success. The Journal of heart andlung transplantation: the official publication of the International Society for HeartTransplantation. 2022; 41(2), 161–170. https://doi.org/10.1016/j.healun.2021.07.011
- Zhang KC, Narang N, Jasseron C, et al. Development and Validation of a Risk ScorePredicting Death Without Transplant in Adult Heart Transplant Candidates. JAMA. 2024;331(6):500–509. doi:10.1001/jama.2023.27029