The procedures of the Spanish Heart Transplant Registry have been detailed in previous reports.1,2 Briefly, the most important clinical procedural data, as well as those of outcomes, mainly in terms of survival, are electronically updated each year using an established datasheet, under the supervision of a contract research organization that is in charge of database maintenance and statistical analysis.

For the last 2 years, 19 centers have undertaken transplant activity (table 1), with 2 centers performing pediatric transplants only. Another 4 centers perform both pediatric and adult transplants while 2 centers perform cardiopulmonary transplants. The types of transplants performed in 2021 and in the entire series are summarized in table 2. Overall, the Spanish Heart Transplant Registry has recorded 9362 procedures. In 2021, 302 transplants were performed, 24 (7.9%) in recipients younger than 18 years and 84 (27.8%) in recipients older than 60 years (figure 1). The data corresponding to the transplants performed in 2021 are provided, as well as those from the previous decade stratified by 3-year period (2012-2014, 2015-2017, and 2018-2020). The percentage of urgent transplants, type of pretransplant circulatory support, and donor age in the last decade were analyzed by year.

Figure 1.

Annual number of transplants (1984-2021), total and by age group.

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Continuous variables are expressed as mean±standard deviation while categorical variables are expressed as percentages. Differences among time periods were analyzed using a nonparametric test for temporal trends (Kendall τ) for categorical variables and a Wilcoxon-type test for trends for continuous variables.3 Survival curves were calculated using the Kaplan-Meier estimator and were compared using a log-rank test. P < .05 was considered statistically significant.

In 2021, 302 transplants were performed, 24 (8.6%) more than in the previous year. Thus, transplant activity returned in 2021 to the levels of 2019, after a fall in the first year of the SARS-CoV-2 pandemic (figure 2). The main recipient characteristics in 2021 and in the 2012 to 2020 period are summarized in table 3. In the overall population, the mean recipient age was 49.3 years and 29.3% were women, figures similar to those of previous years. In the adult population (age ≥ 18 years at transplant), the mean age since 2012 was 53.3±11.8 years (52.9±11.8 years in 2021) and 25.5% were women (26.2% in 2021). In recent years, the recipient characteristics have largely remained unchanged, except for a significant trend for a larger proportion of recipients with previous cardiac surgery (P < .01), a significant change in the type of pretransplant circulatory support (P < .001), and a nonsignificant tendency for a higher proportion of female recipients (P=.06) (table 3). These tendencies are confirmed by the data from 2021. Although it is possible to detect a tendency in the last 5-year period toward a decrease in urgent transplants (from 50.2% in 2016 to 38.0% in 2021), the difference is not significant (P=.01) (figure 3). In 2021, the data confirm the changes over time detected in the last decade, particularly since 2017, in the type of pretransplant circulatory assist devices being used by patients (figure 4). The use of a balloon pump has become rare and there have been decreases in the use of extracorporeal membrane oxygenation (ECMO) and pulsatile ventricular assist devices. In contrast, a considerable increase has been seen in transplanted patients with continuous-flow ventricular assist devices, which represented 71.9% of all circulatory assist devices used in 2021 (figure 4).

Figure 2.

Number of transplants per month from 2019 to 2021.

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Figure 3.

Annual percentage of urgent transplants vs the total number (2012-2021).

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Figure 4.

Distribution of the type of pretransplant circulatory support by year (2012-2021). ECMO, extracorporeal membrane oxygenation; VAD, ventricular assist device.

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The characteristics of the donors and surgical procedures are summarized in table 4. Donor age has followed a significantly biphasic trend in the last decade, with an increase until 2017 and a decrease thereafter. A similar finding was seen upon analysis of the proportion of donors older than 45 years of age, although the result is not significant (figure 5). As in previous reports, the trends persist for a high percentage of donors who had a preprocedural cardiac arrest and who died of stroke (table 4).

Figure 5.

Annual changes in donor age and the percentage of donors older than 45 years (2012-2021).

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The average ischemia time significantly decreased from the 2012 to 2014 period (table 4), largely due to the increase in procedures performed with less than 2hours of ischemia. In 2021, as in the previous 3-year period, 3 out of every 4 transplants were performed with the bicaval technique.

As shown in table 5, induction immunosuppression has not changed in the last 4 years. Almost all patients were treated with triple therapy, comprising tacrolimus, mycophenolate or mycophenolic acid, and steroids. Almost 80% of patients received anti-CD25 antibody-based induction therapy (mainly basiliximab).

Survival in the 2012 to 2021 period was about 80.6% in the first posttransplant year and more than 72.5% at 5 years, which was significantly better than that recorded in the entire previous series (figure 6A). In the 3-year period from 2018 to 2020, survival was 81.5% in the first year and 76.2% in the third year. Although the 2015 to 2017 and 2018 to 2020 periods seem to show an improvement vs 2012 to 2014, the difference is not statistically significant (figure 6B). The slight differences seen between the curves are limited to the earliest period, with survival of 78.3%, 80.7%, and 81.5% in the first years of the 2012 to 2014, 2015 to 2017, and 2018 to 2020 periods, respectively. Subsequently, the curves are clearly parallel. table 6 summarizes some of the univariable predictors of mortality. The factors most strongly associated with mortality were those related to the pretransplant clinical status of the recipient (need for advanced circulatory support or mechanical ventilation) and to comorbidity (age, pretransplant infection, diabetes or pretransplant renal failure, ischemic etiology).

Figure 6.

A: comparison of survival curves between the 2012 to 2021 and 1984 to 2011 periods. B: comparison of survival curves from 2012 to 2020 by 3-year period.

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In the first 5 posttransplant years, the most prevalent specific causes of death were infection (24.9%) and primary graft failure (20.6%) (figure 7), which were almost entirely concentrated in the first posttransplant year and in the first posttransplant month, respectively. Acute transplant rejection was an infrequent cause of death, particularly in the first year, although its prevalence was not negligible between the second and fifth posttransplant years (16.3%). Between the second and fifth posttransplant years, the most frequent causes of death were graft vascular disease/sudden cardiac death (23.3%) and cancer (20.7%).

Figure 7.

Main causes of death by time since transplant in the 2012 to 2021 period. GVD/SCD, graft vascular disease/sudden cardiac death.

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The tendencies in the main causes of death during the first posttransplant year (a period in which follow-up data were available for all patients) were not significant, although there was a numerical tendency for a lower prevalence of acute rejection and a higher prevalence of infections (figure 8).

Figure 8.

Changes over time in the main causes of death in the first posttransplant year from 2012 to 2021 by 3-year period.

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To assess the possible influence of the SARS-CoV-2 pandemic on outcomes, we analyzed 30- and 60-day survival by week of transplant from 2019, the year immediately preceding the pandemic, in patients who underwent transplant from 2019 to 2021. In addition, we analyzed the mortality rate during the above period in patients undergoing transplant before 2019 (table 7). Deaths due to a viral infection other than cytomegalovirus or hepatitis (which are the 2 viral causes specifically considered in the Spanish Heart Transplant Registry) increased from 4 in 2019 to 28 and 27 in 2020 and 2021, respectively.