The influence of mechanical Circulatory support on post-transplant outcomes in pediatric patients: A multicenter study from the International Society for Heart and Lung Transplantation (ISHLT) Registry

Background

Mechanical circulatory support (MCS) is increasingly being used as a bridge to transplant in pediatric patients. We compare outcomes in pediatric patients bridged to transplant with MCS from an international cohort.

Methods

This retrospective cohort study of heart-transplant patients reported to the International Society for Heart and Lung Transplantation (ISHLT) registry from 2005-2017 includes 5,095 patients <18 years. Pretransplant MCS exposure and anatomic diagnosis were derived. Outcomes included mortality, renal failure, and stroke.

Results

26% of patients received MCS prior to transplant: 240 (4.7%) on extracorporeal membrane oxygenation (ECMO), 1,030 (20.2%) on ventricular assist device (VAD), and 54 (1%) both. 29% of patients were <1 year, and 43.8% had congenital heart disease (CHD). After adjusting for clinical characteristics, compared to no-MCS and VAD, ECMO had higher mortality during their transplant hospitalization [OR 3.97 & 2.55; 95% CI 2.43-6.49 & 1.42-4.60] while VAD mortality was similar [OR 1.55; CI 0.99-2.45]. Outcomes of ECMO+VAD were similar to ECMO alone, including increased mortality during transplant hospitalization compared to no-MCS [OR 4.74; CI 1.81-12.36]. Patients with CHD on ECMO had increased 1 year, and 10 year mortality [HR 2.36; CI 1.65–3.39], [HR 1.82; CI 1.33-2.49]; there was no difference in survival in dilated cardiomyopathy (DCM) patients based on pretransplant MCS status.

Conclusion

Survival in CHD and DCM is similar in patients with no MCS or VAD prior to transplant, while pretransplant ECMO use is strongly associated with mortality after transplant particularly in children with CHD. In children with DCM, long term survival was equivalent regardless of MCS status.

Introduction

The population of pediatric patients with advanced heart failure is growing and becoming increasingly complex. With major advances in prenatal diagnosis, medical management, and surgical techniques, once fatal forms of congenital heart disease (CHD) and cardiomyopathy have been transformed into new forms of chronic disease, resulting in an increasing number of children being considered for orthotopic heart transplant (OHT).^1,2 While there has been an increase in need for OHT, the donor pool has remained stable, resulting in longer waitlist times.¹ Organ scarcity, in conjunction with technologic and pharmacologic improvements, have led to the increased use of mechanical circulatory support (MCS) as a bridge to transplant (BTT) in pediatric patients.³

Historically, Extracorporeal Membrane Oxygenation (ECMO) has been the modality of MCS most commonly used as BTT in pediatric OHT. However, over the past decade the use of ventricular assist devices (VADs) in pediatric patients has increased dramatically, especially for children with dilated cardiomyopathy (DCM).^3,4 The most recent PediMACS report emphasizes this finding, showing that between September 2012 and December 2019, 1031 durable VAD implants were placed in 856 pediatric patients, a marked increase from the prior 5 years.⁵ With changes in practice, there has rightly been increased attention to the difference in risk profile and survival based on type of pretransplant MCS, with recent studies demonstrating improved waitlist and overall survival in patients supported with VADs compared to ECMO.^6,7 However, there are limited data that focus primarily on post-transplant outcomes in patients treated with MCS prior to transplant, and almost no data comparing outcomes in subgroups of patients described by underlying disease. Furthermore, the vast majority of studies on pediatric MCS report outcomes from North America, and there is a lack of published data on the worldwide experience.

With a growing population of pediatric patients in need of a heart transplant,^1,2 and the proportion of whom have congenital heart disease having increased from 45.0% of candidates in 2007 to 57.5% by the end of 2017, understanding the interaction of MCS with underlying disease, and its impact not only on waitlist survival, but on post-transplant outcomes, is critical to guiding appropriate therapies. Thus, the purpose of this study is to describe outcomes in an international cohort of post-transplant patients who received MCS prior to their transplant compared to those who did not, and to evaluate if patterns differ depending on primary anatomic diagnosis.