Early primary graft failure after heart transplantation in children is associated with significant rates of mortality and morbidity. Extracorporeal membrane oxygenation is widely used and is well established to support circulatory function in children with post-cardiotomy LCOS (4
). On the basis of this experience, ECMO has become a reasonable option for early graft failure in children after cardiac transplantation (4
). Ventricular assist devices (VADs) are better suited for patients expected to require long-term support; therefore, ECMO remains the most commonly used method of mechanical circulatory support after cardiac surgery or in the post-transplantation period of pediatric patients. This article describes the early and late outcome of ECMO support for early cardiac graft failure in children and represents the largest pediatric experience to date.
In our study, primary post-operative graft failure necessitating ECMO was not uncommon (9%). The majority of patients supported with ECMO in this study were infant recipients (86% <1 year of age), reflecting the usual distribution of pediatric heart transplantation recipients, with the majority of heart transplantations occurring in the <1-yearold group (1
). Nevertheless, pediatric heart recipients requiring ECMO support for early graft failure were significantly younger (p < 0.01) and had a lower weight at transplantation (p < 0.001) compared with our overall transplantation population. Moreover, their total ischemic time was significantly longer (p < 0.01), indicating that harvesting technique and time are crucial and that a longer ischemic time is a major risk factor for graft dysfunction.
The indication for ECMO cannulation did not influence the outcome, and the survival rate was not different in patients presenting with biventricular compared with isolated right ventricular failure. In addition, the survival rate was not significantly different for patients with cardiomyopathy compared with patients with CHD. Poor donor graft function has been implicated as a cause of graft dysfunction after transplantation, but this was not considered different in our study, with no difference in the shortening fraction obtained by M-mode echocardiography between ECMO survivors and nonsurvivors. Although the ejection fraction, considered less accurate compared with the shortening fraction when obtained by M-mode echocardiography, was statistically lower in the survivor group, the mean and median values remain within the normal limit, rendering this difference difficult to interpret.
The timing of ECMO cannulation was also not predictive of outcome. Survival was not significantly different between patients started on ECMO in the operating room for failure to wean from cardiopulmonary bypass compared with those cannulated in the first 48 h after transplantation for hemodynamic instability or cardiac arrest in the cardiac intensive care unit. This is in contradiction to the previous report by Galantowicz and Stolar (19
), who reported no chance of survival if the fresh cardiac allograft could not support the patient after cardiopulmonary bypass. Moreover, cardiac arrest before ECMO cannulation was not a negative predictive factor for survival in our series, and all patients who had cardiac arrest survived.
This result clearly differs from survival rates of 33% to 53% for those patients who experience cardiac arrest and then are placed on ECMO as a bridge to transplantation (18
). This finding suggests that the donor’s heart is more likely to recover after cardiac arrest and subsequent ECMO support than the failing ventricle of a patient who is in need of transplantation. Importantly, however, emergent cannulation was associated with a greater risk of neurologic complications, and all survivors with neurological sequelae were either cannulated emergently or experienced cardiac arrest before cannulation. Therefore, anticipating graft failure with elective cannulation before hemodynamic collapse is likely to improve neurologic outcome.
The mean duration of ECMO support in survivors was significantly less than nonsurvivors, and all survivors were decannulated within 4 days of initiation of support. This finding confirms what has been previously reported in the infant population by our institution (6
). In the Mitchell et al. (6
) infant study, ECMO support for >4 days was associated with death and increased risk of morbidity, particularly sepsis, bleeding, and neurologic sequelae. Recovery of ventricular function within 8 days of ECMO support has been reported and may become more common as ECMO and other mechanical support technology progress and improve over time.
However, on the basis of our institutional experience described here, consideration could be given to listing for retransplantation or transition to a VAD if the patient is not decannulated within 4 days of initiation of ECMO support (6
). Of course, the clinical situation for each individual patient must be carefully considered when making the decision to relist for transplantation. The already present challenges of shortage of donor supply and increased risk of transplantation after support with mechanical assistance require that the decision to list for retransplantation should be reserved for those patients deemed to be good candidates for this option. Those individuals requiring ECMO after transplantation who have evidence of severe neurologic injury, irreversible organ injury, hyperacute rejection, and infection would not be appropriate candidates for retransplantation. The only other factor that correlated with survival was a lower donor ejection fraction. This finding suggests that the use of marginal donors, especially for the infant population where donor shortage is a problem, may not compromise outcome even if ECMO rescue is necessary in the early post-transplantation period (24
Overall, 54% of the patients supported with ECMO were successfully weaned and discharged alive, which is comparable to what has been previously reported in the pediatric population (6
). Long-term survival of those surviving to hospital discharge was excellent, with 100% alive at 3 years after transplantation.
Although the number of early (within the first year after transplantation) acute graft rejection episodes was significantly increased in the ECMO survivors compared with our other transplant recipients, there was no difference in the total number of acute graft rejection episodes between these groups. The number of hemodynamic compromising rejections per patient also was significantly increased in the ECMO survivors (1.3 ± 1.9 vs. 0.7 ± 1.2 in the overall transplant population, p < 0.05). In fact, 20% of the ECMO survivors presented with at least 1 episode of hemodynamically significant rejection requiring inotropic support.
The incidence of transplant coronary artery disease in the ECMO survivors (13%) was not increased compared with our overall transplantation population (16%). This finding is somewhat unexpected, because the increased frequency of early and hemodynamic compromising rejection in the ECMO survivors are factors that have been associated with the development of coronary vasculopathy (25
). This finding is not related to timing of follow-up because transplant coronary vasculopathy in our program is diagnosed at a mean time of 6.4 years after transplantation, and the mean follow-up of the ECMO survivors is 8.1 years. Finally, despite increased frequency of early and severe acute graft rejection in the survivors, the graft function at long-term follow-up is normal.
This study is limited by its descriptive nature and the small sample of patients.