Heart transplantation remains the gold standard treatment for end-stage heart failure. The limited availability of donors and the complexity of post-transplant postoperative management require careful selection of candidates for this therapy. In this setting, mechanical support devices have been transformative, allowing patients to recover and/or remain in adequate clinical condition while awaiting a potential transplant.
One of these devices is extracorporeal membrane oxygenation, or ECMO, which has proven to be a valuable option for stabilizing patients with cardiogenic shock. Despite these favorable results, ECMO is not free from complications, some of which are related to the sedation and mechanical ventilation that are frequently required. For this reason, the authors of the present article asked whether keeping patients extubated while supported with ECMO and listed for heart transplantation could improve posttransplant outcomes. To address this question, they reviewed the UNOS (United Network for Organ Sharing) database and analyzed patients transplanted from ECMO between October 2018, when the US allocation criteria were updated, and September 2023, according to whether they were extubated at the time of transplant.
This was therefore a retrospective observational study based on the US national database, ultimately including 857 patients who underwent heart transplantation from ECMO between 2018 and 2023. Of these, 198 patients (23.1%) were intubated at transplant (ECMO+VENT group), whereas 659 were extubated (ECMO-only group, 76.9%). The authors analyzed and compared baseline donor and recipient characteristics, the incidence of acute rejection, stroke, and dialysis in the postoperative period, and survival at 90 days, 1 year, and 3 years.
Although the number of patients in the ECMO+VENT group remained fairly stable over the study period (35-40 patients per year), the number of patients in the ECMO-only group increased progressively, from 102 patients in 2019 to 148 in 2022, when they accounted for 80.5% of all patients transplanted from ECMO. Preoperatively, patients in the ECMO+VENT group had more frequently required dialysis (14.2% vs. 7.6%; p = .005) and intra-aortic balloon pump support (30.3% vs. 18.8%; p < .001). By contrast, patients in the ECMO-only group more often had a temporary ventricular assist device in addition to ECMO (26.6% vs. 19.2%; p = .04) and reached transplant with better functional status (patients with progressive deterioration despite support, 32.9% vs. 51.3%; p < .001).
After transplantation, patients in the ECMO-only group had fewer strokes (6.2% vs. 10.7%; p = .04), required dialysis less often (24.7% vs. 35.5%; p = .003), and had a shorter hospital stay (22 vs. 26 days; p < .001), with no differences in rejection episodes. Finally, during follow-up, patients in the ECMO-only group showed higher survival at 90 days (95.1% vs. 91.1%; HR = 0.48; p = .02), at 1 year (91.2% vs. 85.7%; HR = 0.59; p = .04), and at 3 years (86.0% vs. 77.6%; HR = 0.61; p = .03).
On the basis of these findings, the authors concluded that patients bridged to heart transplantation with ECMO who are extubated at the time of transplant have better peritransplant outcomes and better survival than those who remain intubated.
COMMENTARY:
Despite the growing momentum of durable ventricular assist devices, heart transplantation remains the best therapeutic option for end-stage heart failure once medical treatment has been exhausted, provided that no contraindications are present. Its main limitation lies in the shortage of donors, which has a double consequence. On the one hand, some patients deteriorate while waiting and require some form of support until a suitable graft becomes available. On the other, it forces us to be extremely selective when offering a heart to a patient, because avoiding futility and thereby “wasting” an organ is essential.
The adverse effects of prolonged intubation are well described in the literature, including higher risks of infection, lung injury, deconditioning, and myopathy. Indeed, in Spain, the latest update of the allocation criteria, which came into force in 2024, considered remaining intubated for more than 7 days as evidence of multiorgan failure and, therefore, a major exclusion criterion, with the exception of patients with electrical storm. In parallel, and perhaps related to this, poorer outcomes after transplantation following ECMO support have also been well documented. I say related because patients supported with ECMO are often intubated, sedated, and confined to bed. This raises the question of whether those results would be different if we were able to wake, extubate, and mobilize patients during ECMO support. This is precisely what the present article analyzes.
The first striking findings are, on the one hand, the increase in the number of patients transplanted from ECMO, from 16 in 2015 to 185 in 2022, and, on the other, the proportion of these patients who reached transplant extubated. They represented almost 77%, and this proportion increased over the 5-year study period. The authors do not specify whether these patients had been intubated at any point, which is an important limitation of the study. Nevertheless, it is likely that a substantial proportion were initially intubated and subsequently extubated before being listed. In any case, being able to keep 3 of every 4 of these patients awake and extubated is highly commendable.
Regarding baseline characteristics, one might interpret that patients in the ECMO-only group were “healthier” or, perhaps more accurately, “less sick,” given their lower rates of intra-aortic balloon pump support and dialysis and their better functional status. In my opinion, it is not necessarily that they were better at baseline, but rather that the acute management strategy that enabled extubation, for example the more frequent use of another temporary support device, allowed them to progress more favorably and reach transplant with less deterioration. In fact, the greater use of temporary support in addition to ECMO could indicate a more compromised clinical situation in which ECMO alone was insufficient. Instead, the greater unloading provided by this additional support may have been what allowed these patients to improve, avoiding the need to keep them intubated.
The postoperative benefits were unquestionable, with less need for dialysis, fewer strokes, and a shorter hospital stay in the ECMO-only group. These benefits translated directly into survival, both in the short term (90 days) and in the mid-term (1 and 3 years). In the comparative survival curve, the curves separate early, with a slight further widening of this difference over the 3-year follow-up. Finally, the favorable survival results in the ECMO-only group should be emphasized, with 1-year survival exceeding 90%. To put this figure into context, overall 1-year survival in Spain currently stands slightly above 85%.
Several limitations should be considered. First, this is a retrospective observational study, with all the inherent biases this design entails. In addition, because the analysis was based on a database not specifically designed for this study, several potential confounders could not be assessed because they were not recorded, such as ECMO cannulation strategy, duration of support, or ECMO-related complications. Third, it is noteworthy that the authors did not analyze the incidence of primary graft failure, given its importance in transplant outcomes and the fact that some studies have identified pretransplant mechanical support as a risk factor. Finally, another important limitation is that the study does not clarify whether patients in the ECMO-only group had never been intubated or, alternatively, had been intubated at some point but were extubated before transplant. Nor does it analyze ventilation-related factors that may have influenced outcomes, such as duration of ventilation or the need for reintubation.
In summary, this is a very interesting study that once again highlights the importance of bringing patients to transplantation in the best possible condition. In patients with cardiogenic shock who require ECMO support to reach transplant, this is difficult but particularly important. The study shows that, when this can be achieved, it has a clear impact on outcomes. In other words, the goal is not only to find a good heart for the patient, but also a good patient for the heart.
REFERENCE:
Akbar AF, Zhou AL, Kalra A, Oak A, Ruck JM, Whitman GJR, Cho SM, Kilic A. National Outcomes of Nonintubated Extracorporeal Membrane Oxygenation as a Bridge to Heart Transplantation. Ann Thorac Surg. 2026 Feb;121(2):439-446.
