The Spanish heart transplant registry is a voluntary registry of heart transplant procedures performed in Spain. Although voluntary, the registry encompasses all procedures conducted in all centers with transplant activity in Spain since 1984 (table 1). The registry includes variables related to the demographic and clinical characteristics of recipients, donors, surgical procedures, immunosuppression protocols, and posttransplant complications, including mortality and its causes. The registry has been continually active for more than 30 years. The main changes in its structure are related to, first, the adoption of electronic data submission, second, the addition or change of variable definition or coding, and, finally, the incorporation of centers initiating transplant activity. Structurally, the Spanish heart transplant registry consists of a management team including a medical director and an assessment committee that is in charge of evaluating and approving the suitability of the use of registry data for research purposes and of an external contract research organization that is responsible for database maintenance and statistical analysis, activities that also involve comparisons with other international registries.

The total numbers and types of transplant conducted in 2023 and in the entire series are summarized in table 2. In 2023, 325 transplants were performed; most (n=311) were isolated heart transplants. There were 11 retransplants (3.4%) and 3 combined transplants (2 heart-kidney transplants and 1 heart-lung transplant). In terms of age, 10.2% of recipients (33 patients) were younger than 18 years and 28.9% (94 patients) were older than 60 years. Since the beginning, the Spanish heart transplant registry has recorded 9998 procedures (figure 1). The present report updates the information with the introduction of data related to the transplants performed in 2023. In addition, we analyzed the changes over time in the characteristics and outcomes of the procedures in the previous decade (since 2014). To do so, the period was stratified into triennia (2014-2016, 2017-2019, and 2020-2022). Some variables were analyzed on an annual basis (urgent transplants, circulatory assist devices).

Figure 1.

Annual number of transplants (1984-2023), total and by age group.

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Continuous quantitative variables are presented as mean±standard deviation, while categorical variables are expressed as percentages. The nonparametric Kendall tau test and the Wilcoxon test for trends were used to assess temporal trends in the categorical and quantitative variables, respectively.2 Cumulative survival was estimated using the Kaplan-Meier method and differences between groups were determined using the log-rank test. Differences were considered statistically significant at a 2-tailed P<.05.

In total, 325 transplants were performed in 2023, marking a 4.5% increase compared with the previous year (figure 1). The principal recipient characteristics in 2023 and from 2014 to 2023 are summarized in table 3. The main changes in the last decade include the relative increase in female recipients, who represented 30% of all recipients in 2023. Related to this tendency is the percentage decrease in ischemic etiology as the leading cause of the heart disease prompting the transplant and the increase in other etiologies that are percentually more frequent in women than in men (hypertrophic cardiomyopathy, 12.6% in women vs 6.1% in men; restrictive cardiomyopathy, 8.4% vs 4.1%; and congenital heart disease, 11.1% vs 5.7%). As in the previous report,3 a trend was seen toward recipients with better clinical status. This was inferred from a significant trend for fewer recipients with elevated pretransplant bilirubin levels (as an indicator of better congestive status and lower ischemic kidney disease) and for the need for pretransplant intubation, which was required in less than 10% of patients in 2023. In addition, the previous tendency toward a decrease in urgent transplants was broken in 2023, with an uptick to 44% in 2023 (P for trend=.02) (figure 2). As in previous years, there was widespread use of pretransplant circulatory support in 2023 (191 recipients [39.7%]). Since 2014, 1815 patients (38.5%) have undergone transplantation with previous circulatory support. However, the most relevant finding in 2023 was the relative increase in the pretransplant use of extracorporeal membrane oxygenation (from 23.2% in 2022 to 36.5% in 2023) at the expense of ventricular assist devices (from 75.0% in 2022 to 61.1% in 2023) (figure 3).

Figure 2.

Annual percentage of urgent transplants vs the total number (2014-2023). The dotted line indicates the linear adjustment line of the temporal trend.

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Figure 3.

Distribution of the type of pretransplant circulatory support by year (2014-2023). ECMO, extracorporeal membrane oxygenation; VAD, ventricular assist device.

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Donor and surgical procedure characteristics are summarized in table 4. There was a significant trend toward a lower use of suboptimal donors, defined as those older than 45 years, which fell to 47.4% of all transplants in 2023 vs 54.3% from 2014 to 2016 (figure 4). The trend for transplants with a recipient-donor sex mismatch (male recipient-female donor) was also significant, falling from 24.9% in the triennium from 2014 to 2016 to 15.4% in 2023.

Figure 4.

Annual changes in donor age (continuous red line) and the percentage of donors older than 45 years (2014-2023) (blue bars). The dotted lines indicate the linear adjustment lines of the temporal trend. This figure is shown in color in the online version of the article.

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The most significant data regarding the donation process, consolidated in 2023, concerned donation after circulatory death (asystole). The first such procedure was conducted in January 2020 in Hospital Universitario Puerta de Hierro-Majadahonda. By December 2023, a total of 110 such transplants had been performed in 14 programs, 98 in adult recipients and 12 in pediatric patients. In 2023, transplants with donation after circulatory death comprised almost 18% of all procedures and 24% of all transplants performed at centers with an active circulatory death donation program. In addition, in 2023, 3 ABO-incompatible transplants were performed, a technique restricted to pediatric recipients. Since the initiation of these programs in 2018, this technique has represented 13.4% of all procedures performed in accredited centers.

Regarding the remaining characteristics, the last decade showed a highly significant trend toward ensuring recipient-donor sex concordance to avoid the unfavorable matching of a female donor with a male recipient (15.4% of patients in 2023 vs 24.9% in the triennium from 2014 to 2016). Equally, the use of the bicaval technique increased to almost 84% of all procedures. Although the difference was not statistically significant, ischemia time showed a slight tendency toward a decrease, with an average of slightly longer than 3hours in 2023.

Induction immunosuppression trends are summarized in table 5. Over the past decade, there have been no significant new developments. Except in rare situations, patients receive triple therapy consisting of tacrolimus, mycophenolate mofetil/mycophenolic acid, and steroids. Induction therapy, often involves the use of antibodies (82.5% of patients), generally basiliximab.

From 2014 to 2023, survival was 81.4% in the first posttransplant year and 74.0% at 5 years, which was significantly better than in the 1984 to 2013 period (figure 5A). In the pediatric population (recipients younger than 18 years at transplant), posttransplant survivals at 1 and 5 years were 83.6% and 80.4%, respectively, in the last decade.

Figure 5.

A: comparison of survival curves between the 2014 to 2023 and 1984 to 2013 periods. B: comparison of survival curves from 2014 to 2023 by triennium.

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The trend for improved survival in recent years was statistically significant (figure 5B). Survival in the first posttransplant year increased from 79.0% in the triennium from 2014 to 2016 to 83.0% from 2020 to 2022. Some of the univariable predictors of mortality are summarized in table 6. As already noted in the previous report,3 the main factors associated with mortality were related to clinical characteristics or variables associated with the recipient's pretransplant clinical status.

The specific causes of death in the first 5 posttransplant years remained infection (25.8%) and primary graft failure (19.5%) (figure 6). As expected, primary graft failure was the leading cause of death in the first posttransplant month (37.8% of all deaths). Infection was by the far the leading cause of death after the first month and until the 1-year posttransplant point (44.5% of deaths), although the risk subsequently remained high (21% of deaths until the fifth posttransplant year). Acute rejection was a nonnegligible cause of death, particularly in the period between 1 and 5 posttransplant years (13% of deaths). Even so, in this period, the most frequent causes of death were graft vascular disease/sudden cardiac death (22.8%), infection (21%), and cancer (18.5%). Primary graft failure (14.6%) and particularly infection (25.0%) were also the most frequent causes of death in the first 5 posttransplant years in the pediatric population.

Figure 6.

Main causes of death by time since transplant in the 2014 to 2023 period. GVD/SCD, graft vascular disease/sudden cardiac death. Each cause of death is reported as a percentage of total patient deaths in the specific period.

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To assess changes in the main causes of death over time, we studied the same causes in the first posttransplant year to ensure a comparable follow-up among triennia. Acute rejection significantly decreased as a cause of death during the last decade. In contrast, primary graft failure and infection remained statistically stable in the same period (figure 7).

Figure 7.

Changes over time in the main causes of death in the first posttransplant year in the 2014 to 2023 period by triennium.

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This study has the limitations inherent to a registry of unaudited procedures.