We are currently witnessing a period in which, similar to the adult population, the number of pediatric patients requiring heart transplantation is increasing, while the number of donors remains limited. This has made the development of long-term assist devices imperative, primarily aimed at serving as a “bridge to transplantation.”

The article under discussion today addresses the impact on the post-transplant period of using long-term ventricular assist devices as a bridge to transplantation in pediatric patients and/or those with congenital heart disease, compared to those who did not require such devices. Although this is a single-center study, it is quite comprehensive and provides encouraging data for this complex patient group.

The study includes a total of 181 pediatric and/or congenital heart disease patients who underwent 186 transplants over an 11-year period, from January 2011 to January 2022. Among these, 28.5% (53/186) had pre-transplant VAD support: 50 were paracorporeal (Berlin EXCOR®), and 3 were continuous-flow devices (HeartWare HVAD®). Specifically, biventricular assist devices were implanted in 53% of the patients (and in the majority of single-ventricle physiology cases). The authors clearly favor pulsatile-flow devices due to their more physiological performance and more intuitive management compared to continuous-flow devices. Furthermore, they highlight an institutional preference for biventricular over univentricular assist devices, especially in neonates and infants with biventricular physiology, owing to the difficulty in predicting subsequent right ventricular failure in patients supported solely with univentricular devices.

Patients with long-term VAD support were observed to be younger than those without it (4.8 years vs. 12.1 years; p = .0001), had undergone more cardiac surgeries (3 vs. 1.8; p = .0003), and were more likely to receive ABO-incompatible transplants (18.9% vs. 6.8%; p = .028).

In univariate analysis, the following factors were associated with decreased long-term survival: prior cardiac surgery (HR = 6; p = .015), single-ventricle physiology (HR = 2.4; p = .038), congenital vs. acquired heart disease (HR = 5.7; p = .005), and pre-transplant renal failure (HR = 3.4; p = .003). However, multivariate analysis, adjusting for these factors, did not reveal a clear impact of pre-transplant VAD support on long-term survival.

Kaplan-Meier survival curves also showed no significant differences in 5- and 10-year post-transplant survival between patients with and without pre-transplant VAD support.

The authors note a significant statistical limitation due to sample size but emphasize the importance of multicenter studies to confirm and support such promising results for this patient population.

COMMENTARY:

Traditionally, ECMO (Extra-Corporeal Membrane Oxygenation) has been the primary alternative in pediatric populations with refractory heart failure, including as a bridge to transplantation. However, in recent years, long-term ventricular assist devices (VADs) increasingly tailored to pediatric patients have largely displaced ECMO in this role. Moreover, technological advancements in these devices and their management have improved outcomes for more complex patients, such as younger children and those with congenital heart disease, who present unique challenges due to their weight, anatomy, and more complex pathophysiology.

Numerous studies have aimed to evaluate the impact of pre-transplant long-term VAD support on post-transplant outcomes and long-term survival compared to patients who did not require it. Clearly, the former represents a higher-risk group, often in poorer clinical condition and with more negative survival risk factors, some of which can be categorized as “modifiable risk factors” (renal dysfunction, respiratory insufficiency, hepatic failure, critical illness polyneuropathy, etc.). These modifiable risk factors can be effectively mitigated or even improved significantly with VAD support, allowing the patient’s baseline condition to improve over time. VADs have enabled patients who would otherwise not survive on the waiting list to undergo transplantation, often in better condition than when initially listed.

This is likely one of the main reasons why there appear to be no clear differences in post-transplant survival between the two patient cohorts: VAD support allows patients to improve to the point where surgical risk at transplantation is comparable to that of those who did not require prior assistance.

Unlike other studies, such as the Pediatric Interagency Registry for Mechanical Circulatory Support (Pedimacs) report, which indicated that pulsatile biventricular VADs were less frequently used and had worse outcomes compared to continuous-flow devices, our authors preferred the former for the reasons previously explained and achieved very promising results. Both the Pedimacs registry findings and our country’s experience were analyzed in previous blog entries. This underscores that patient management strategies are not uniform, and institutional protocols vary—each potentially valid, as corroborated by these results.

These findings suggest that, with these data in hand, we should consider developing registries and multicenter studies to help standardize the management of these children. This will enable us to continue improving and challenging the natural history of many congenital heart diseases, ultimately shedding light on what would otherwise be a grim prognosis for these patients.

REFERENCE:

Kulshrestha K, Morales DLS. Good things come to those who wait: Single-institution post-heart transplant outcomes after VAD. Ann Thorac Surg. 2023 Apr 21:S0003-4975(23)00403-4. doi: 10.1016/j.athoracsur.2023.03.039.