All organ transplant programs must continuously review their allocation criteria, prioritizing patients in the most critical clinical condition, provided they maintain a high probability of success after the procedure to prevent futility of such a limited resource.

Each year, all Spanish heart transplant (HT) teams meet with the National Transplant Organization (ONT) to ratify or modify the criteria for the distribution of donor hearts, for both adult and pediatric HT. Over the years, and with the aim of meeting the objective outlined above, several modifications to these criteria have been implemented, the most recent being in 2017.

In June 2022, a consensus conference was held at Casa del Corazón in Madrid, organized by the Heart Failure Association of the Spanish Society of Cardiology (SEC) and the ONT, with the participation of cardiologists, cardiac surgeons, and transplant coordinators from hospitals, regional organizations, and the ONT itself.

The objectives of this consensus conference were:

1. To analyze the current organization and management of patients with advanced heart failure and cardiogenic shock in Spain.
2. To conduct a critical review of HT distribution and urgency criteria applied in other countries.
3. To assess outcomes in Spain concerning patients on the waiting list, donors utilized, and post-HT clinical results, following the 2017 revision of HT urgency criteria.
4. To establish a national protocol for cardiac donation after circulatory death.
5. To propose new prioritization criteria for HT in Spain.

At the conference, for each of these objectives, multidisciplinary working groups were formed with representation from transplant centers and the ONT. These groups developed reports and their conclusions by the end of 2022. A summary of these reports and conclusions will be published in an upcoming issue of Revista Española de Cardiología.

In February 2023, a meeting between Spanish HT groups and the ONT took place at the ONT facilities to discuss the working group’s proposal and agree on the “2023 HT Distribution Criteria in Spain,” which took effect on April 1, 2023.

The prioritization criteria adopted represent the most profound change ever made compared to the previous standards. Notably, there is now an objective definition of “multiorgan failure (MOF),” as its presence leads to either temporary exclusion or inability to be listed for HT. MOF is defined by the presence of any of the following five criteria:

1. A score >11 points on the SOFA (Sepsis-related Organ Failure Assessment) scale for 48 hours. A patient with a creatinine level of 2.1 mg/dL, bilirubin level of 2.1 mg/dL, 90000 platelets/mm³, PaO₂/FiO₂ < 300 mmHg, and norepinephrine dosage of 0.2 mcg/kg/min would meet this criterion.
2. Patients on invasive mechanical ventilation (IMV) for seven consecutive days, except for patients in electrical storm.
3. Acute or chronic renal failure requiring renal replacement therapy (RRT), except cardio-renal transplant candidates and patients with anuric acute tubular necrosis following at least four weeks of short-term mechanical circulatory support, prior glomerular filtration rate >60 mL/min, and a SOFA score <6 points. Ultrafiltration for managing patient volemia is not considered RRT.
4. Patients on IMV for more than five days who, after extubation, exhibit critical illness myopathy, defined by a score <36 points on the Medical Research Council (MRC) scale.
5. Patients on circulatory support and vasoactive drugs with a vasoactive-inotropic score (VIS) >20 points. This score is reached with an isolated dose of 0.2 mcg/kg/min of epinephrine or norepinephrine, or with 5 mcg/kg/min of dobutamine and 0.15 mcg/kg/min of epinephrine or norepinephrine.

The second significant change in the new criteria refers to the classification within the highest prioritization level. In the absence of MOF, Urgency O is divided into two grades: OA for patients supported with veno-arterial ECMO or biventricular mechanical assistance and patients with long-term ventricular assist devices (LVAD) experiencing severe mechanical dysfunction or thromboembolic complications, and grade OB for patients supported with short-term univentricular full-support circulatory assist devices (such as Centrimag®, Impella® 5.0, 5.5, or CP if the patient has a body surface area <1.7 m²) and patients with refractory electrical storm (three or more episodes of at least five minutes within 24 hours, requiring cardioversion or pacing and unresponsive to treatment within four days) without circulatory assist device support.

Thirdly, priority level 1 (third clinical severity level) has been expanded to include not only LVAD dysfunction due to driveline infection, persistent gastrointestinal bleeding, or severe right ventricular dysfunction but also certain uncommon yet challenging clinical situations. These include adult patients with univentricular physiology requiring continuous intravenous treatment, adult Fontan surgery patients with severe protein-losing enteropathy, and patients with cardiomyopathies with reduced cardiac chambers who are not candidates for mechanical assist devices.

As previously mentioned, this is the most profound modification made to date in HT prioritization criteria. Its purpose, developed through a multidisciplinary consensus conference, is to prioritize patients in the most critical clinical situations without reaching the MOF threshold, aiming to optimize the efficient use of the highly limited resource that is the donor heart.

For future analysis of the impact of these new HT prioritization criteria in Spain, it is essential to remember some figures and their evolution over recent years, examining the results of the 2017 changes, which serve as a starting point for future analysis.

According to data from the 2022 Spanish Heart Donation and Transplant Activity Report, the number of HTs in Spain peaked in 2000 with 353 implants (8.9 per million population). The enactment of the new Road Safety Law in Spain, fortunately, led to a significant decline in donors from brain death due to traumatic brain injury, resulting in a decrease in HT numbers, reaching a low in 2011 with 237 implants (5.0 per million population). Since then, activity has slowly but steadily increased due to a greater use of hearts from donors after brain death secondary to stroke and, over the past two years, controlled circulatory death donations. In 2022, 311 procedures were performed (6.6 per million population).

From 2013 to 2018, between 45-49% of heart transplants in Spain were performed on an urgent basis. This figure has decreased significantly since 2019, possibly influenced by the 2017 changes in HT prioritization criteria, dropping to 38%. Although these percentage changes have not significantly altered the likelihood of transplantation for a patient listed as urgent, which has remained between 75-80% over the past 10 years, there has been an increase in the probability of transplantation for a patient listed as elective. This probability has risen from an average of 40% until 2016 to 50-55% since then.

Analyzing the results, survival rates from 2013 to 2022 are 81.4% one year post-transplant and 73.4% at five years, significantly higher than those observed in the earlier series. There has been no statistically significant improvement in survival over the last decade; however, there is a constant numerical improvement in one-year survival: 79.7% in the period 2013-2015, 81.7% in 2016-2018, and 82.2% in 2019-2021.

Clinical outcomes over the coming years will allow us to evaluate whether this modification of HT distribution and prioritization criteria in Spain has been an effective tool in achieving a difficult balance between accessibility and futility for this complex therapy.

REFERENCES:

1. Review of heart transplant distribution criteria in Spain 2023. Consensus document SEC-Heart Failure Association/ONT/SECCE Distribution Criteria 2023. Heart Transplant.
2. Distribution Criteria 2023. Heart Transplant.
3. Spanish Heart Donation and Transplant Activity Report 2022.
4. González-Vílchez F, Hernández-Pérez F, Almenar-Bonet L, Crespo-Leiro MG, López-Granados A, et al.; on behalf of the Spanish Heart Transplant Teams. Spanish heart transplant registry. 34th official report of the Heart Failure Association of the Spanish Society of Cardiology. Rev Esp Cardiol (Engl Ed). 2023 Sep 6(23)00234-7. English, Spanish. doi: 10.1016/j.rec.2023.06.013.