Use of extracorporeal life support as a bridge to pediatric cardiac transplantation

The role of ventricular assist device in children

The first and successful implantation of a ventricular assist device in 1990 has allowed an 8-year-old child with an end-stage heart failure to undergo a heart transplantation. This milestone paved the way to consider support with ventricular assist in the armamentarium of heart failure management in infants, children and adolescents. Several systems have evolved and faded owing to unacceptable complications. Indications and contraindications to implantation have been established. Anticoagulation management is still on its way to impeccability. Despite the challenges, issues and concerns revolving around ventricular assist devices, the system definitely supports pediatric patients with end-stage heart failure until heart transplantation and could allow recovery of the myocardium.

Mechanical circulatory support in paediatric population

Extra-corporeal membrane oxygenation is a life-saving modality to support the cardiac and/or pulmonary system as a form of life support in resuscitation, post-cardiotomy, as a bridge to cardiac transplantation and in respiratory failure. Its use in the paediatric and neonatal population has proven incredibly useful. However, extra-corporeal membrane oxygenation is also associated with a greater rate of mortality and complications, particularly in those with co-morbidities. As a result, interventions such as ventricular assist devices have been trialled in these patients. In this review, we provide a comprehensive analysis of the current literature on extra-corporeal membrane oxygenation for cardiac support in the paediatric and neonatal population. We evaluate its effectiveness in comparison to other forms of mechanical circulatory support and focus on areas for future development.

Pediatric ventricular assist devices: what are the key considerations and requirements?

Introduction: The development of ventricular assist devices (VADs) have enabled myocardial recovery and improved patient survival until heart transplantation. However, device options remain limited for children and lag in development.Areas covered: This review focuses on the evolution of pediatric VADs in becoming to be an accepted treatment option in advanced heart failure, discusses the classification of VADs available for children, i.e. types of pumps and duration of support, and defines implantation indications and explantation criteria, describes attendant complications and long-term outcome of VAD support. Furthermore, we emphasize the key considerations and requirements in the application of these devices in infants, children and adolescents.Expert opinion: Increasing use of VADs has facilitated a leading edge in management of advanced heart failure either as a bridge to transplantation or as a bridge to myocardial recovery. In newborns and small children, the EXCOR Pediatric VAD remains the only reliable option. In some patients ventricular unloading may lead to complete myocardial recovery. There is a strong need for pumps that are fully implantable, suitable for single ventricle physiology, such as the right ventricle.

Mechanical circulatory support in children: past, present and future

Rapid advances in the field of mechanical circulatory support (MCS) have dramatically changed the management of pediatric patients with heart failure. There is now emphasis on timely implantation of ventricular assist devices (VADs) to preserve or recover end-organ function, and increased focus on post-implant management to improve the stroke rate. Transplant waitlist mortality has significantly decreased in the era of VAD use. Devices approved for adults are being used off-label in children with excellent outcomes, allowing chronic therapy and discharge home to become part of pediatric VAD therapy.

Prognostic Risk Analyses for Postcardiotomy Extracorporeal Membrane Oxygenation in Children: A Review of Early and Intermediate Outcomes

We evaluated the morbidity and mortality of children requiring postcardiotomy extracorporeal membrane oxygenation (ECMO) to determine independent factors affecting early and intermediate outcomes. Between January 2002 and December 2015, 79 instances of ECMO after cardiac surgery in 73 children were retrospectively reviewed. Follow-up was completed in December 2016. Predictive risk analyses were employed concerning weaning of ECMO, hospital discharge, and mortality after discharge. Age and weight were 14.9 ± 25.6 months and 7.0 ± 5.3 kg, respectively. Median support time was 8.3 ± 4.4 days. Sixty-seven (85%) were successfully weaned off ECMO and 48 (61%) survived to hospital discharge. Multi-variate logistic regression analysis identified the first day to obtain negative fluid balance after initiation of support (adjusted odds ratio = 0.42), high serum lactate levels (0.97), and high total bilirubin (0.84) during support as significant independent factors associated with successful separation from ECMO. The first day of negative fluid balance (0.65) after successful decannulation was an independent risk factor for survival to hospital discharge. After hospital discharge, actuarial 1-year, 5-year, and 10-year survival rates were 94%, 78%, and 78%, respectively. Low weight increased the risk of death after hospital discharge by a multi-variate Cox hazard model. High serum lactate, high serum bilirubin, and unable to obtain early negative fluid balance during support impacted mortality of decannulation. Obtaining a late negative fluid balance in post-ECMO were independent risk factors for death after successful weaning. Low weight affected intermediate outcomes.

Extracorporeal membrane oxygenation in pediatric cardiac surgery: A retrospective review of trends and outcomes in Scotland

Introduction:

Around 3.2%–8.4% of patients receive venoarterial (VA) extracorporeal membrane oxygenation (ECMO) support after pediatric cardiac surgery. The desired outcome is “bridge-to-recovery” in most cases. There is no universally agreed protocol, and given the associated costs and complications rates, the decisions as of when and when not to institute VA ECMO are largely empirical.

Methods:

A retrospective review of the ECMO database at the Scottish Pediatric Cardiac Services (SPCS) was undertaken. Inclusion criterion encompassed all children (<16 years of age) who were supported with VA ECMO following cardiac surgery between January 2011 and October 2016. The timing of ECMO support was divided into three distinct phases: “endofcase” or intheatre ECMO for patients unable to effectively wean from cardiopulmonary bypass (CPB), ECMO for cardiopulmonary resuscitation (“ECPR”), and Intensive Care Unit ECMO for “failing maximal medial therapy” following cardiac surgery. The patients were analyzed to identify survival rates, adverse prognostic indicators, and complication rates.

Results:

We identified 66 patients who met the inclusion criterion. 30day survival rate was 45% and survival rate to hospital discharge was 44% (the difference represents one patient). On followup (median: 960 days, range: 42–2010 days), all survivors to hospital discharge were alive at review date. “End-of-case” ECMO showed a trend toward better survival of the three subcategories (“end of case,” ECPR, and ECMO for “failing maximal medical therapy” survival rates were 47%, 41%, and 37.5%, respectively, P = 0.807). The poorest survival rates were in the younger children (<6 months, P = 0.502), patients who had prolonged CPB (P = 0.314) and aortic crossclamp times (P = 0.146), and longer duration of ECMO (>10 days, P = 0.177).

Conclusions:

Allcomers VA ECMO following pediatric cardiac surgery had survival to discharge rate of 44%. Elective “end-of-case” ECMO carries better survival rates and therefore ECMO instituted early maybe advantageous. Prolonged ECMO support has a direct correlation with mortality.

Improved Survival While Waiting and Risk Factors for Death in Pediatric Patients Listed for Cardiac Transplantation

Our aim is to determine (a) the effect of changes in pre-transplant management and era of listing on survival of children listed for HTx and (b) risk factors for death while waiting. This retrospective study included all children listed between 1/1993 and 12/2009 at our center. Survival was determined using survival analysis and competing outcomes modeling. There were 254 listed patients of whom 144 (57%) had congenital heart disease, 208 (82%) were status 1, 52 used ECMO (20%), and 28 used ventricular assist device support (VAD) (11%) beginning in 2005. Overall mortality while waiting was 17% at 6 months, and 69% underwent transplant. Seven of 95 patients (7%) died waiting after 2004 compared to 36 of 159 (23%) before. ECMO and earlier year of listing were significant risk factors (p < 0.001) for wait-list mortality, whereas mortality was significantly lower (p = 0.002) after availability of VADs. Race, gender, blood type, and congenital diagnosis were not significant risk factors for death. Survival in pediatric patients listed for HTx has improved significantly in the current era at our institution. The availability of pediatric VADs has had a significant impact on survival while waiting in children listed for transplantation.

Desfechos clínicos de pacientes pediátricos tratados com oxigenação por membrana extracorpórea

Resumo Objetivo Identificar os fatores relacionados à mortalidade e avaliar a sobrevida de pacientes pediátricos tratados com oxigenação por membrana extracorpórea. Métodos Estudo de coorte retrospectivo, que incluiu pacientes pediátricos que utilizaram o dispositivo nos últimos cinco anos. Os grupos foram divididos com base naqueles que sobreviveram ou não após a terapia. Para avaliar os fatores preditivos de morte, foi utilizada análise multivariada com regressão logística e, para a sobrevida, o método de Kaplan-Meier e Log-Rank. Resultados A fração de ejeção do ventrículo esquerdo era maior no grupo de sobreviventes (74%+14,6% vs 56,2% + 22%, p=0,038) e o número de pacientes que necessitaram de diálise foi maior no grupo de não sobreviventes (52,4% vs. 12,5%, p=0,039), sendo a sobrevida significativamente menor neste grupo (log-rank=0,020). Conclusão Disfunção ventricular prévia, evidenciada pela fração de ejeção do ventrículo esquerdo <55%, e necessidade de terapia de substituição renal concomitante aumentaram o risco de morte.

Extracorporeal Life Support in Pediatric and Neonatal Critical Care: A Review

Extracorporeal life support (ECLS) is a modified form of cardiopulmonary bypass used to provide prolonged tissue oxygen delivery in patients with respiratory and/or cardiac failure. The first large-scale success of ECLS was achieved in the management of term newborns with respiratory failure. ECLS has become an accepted therapeutic modality for neonates, children, and adults who have failed conventional therapy and in whom cardiac and/or respiratory insufficiency is potentially reversible. The use of ECLS allows one to reduce other cardiopulmonary supports and apply a gentle ventilation strategy in a population of severely compromised critical care patients. ECLS has now been employed in more than 26,000 neonatal and pediatric patients with an overall survival rate of 68%. ECLS has evolved significantly over 25 years of clinical practice; patient selection for this complex and highly invasive therapy, as well as how ECLS is employed in different patient groups, is constantly changing. Generally, ECLS is used more liberally now than in the past. The number of patients requiring this support, however, is declining yearly, and those patients who receive ECLS compose a more severe subset of an intensive care population. This review provides an overview of the development of ECLS and the equipment and techniques employed. The use of ECLS for neonatal respiratory failure, pediatric respiratory failure, and cardiac support are outlined. Management of the ECLS patient is discussed in detail, and outcome of these patients is reviewed. Finally, current trends and future implications of ECLS in neonatal and pediatric critical care are addressed.

Extracorporeal Life Support for Pediatric Heart Failure

Extracorporeal life support (ECLS) represents an essential component in the treatment of the pediatric patient with refractory heart failure. Defined as the use of an extracorporeal system to provide cardiopulmonary support, ECLS provides hemodynamic support to facilitate end-organ recovery and can be used as a salvage therapy during acute cardiorespiratory failure. Support strategies employed in pediatric cardiac patients include bridge to recovery, bridge to therapy, and bridge to transplant. Advances in extracorporeal technology and refinements in patient selection have allowed wider application of this therapy in pediatric heart failure patients.

ECLS in Pediatric Cardiac Patients

Extracorporeal life support (ECLS) is an important device in the management of children with severe refractory cardiac and or pulmonary failure. Actually, two forms of ECLS are available for neonates and children: extracorporeal membrane oxygenation (ECMO) and use of a ventricular assist device (VAD). Both these techniques have their own advantages and disadvantages. The intra-aortic balloon pump is another ECLS device that has been successfully used in larger children, adolescents, and adults, but has found limited applicability in smaller children. In this review, we will present the "state of art" of ECMO in neonate and children with heart failure. ECMO is commonly used in a variety of settings to provide support to critically ill patients with cardiac disease. However, a strict selection of patients and timing of intervention should be performed to avoid the increase in mortality and morbidity of these patients. Therefore, every attempt should be done to start ECLS "urgently" rather than "emergently," before the presence of dysfunction of end organs or circulatory collapse. Even though exciting progress is being made in the development of VADs for long-term mechanical support in children, ECMO remains the mainstay of mechanical circulatory support in children with complex anatomy, particularly those needing rapid resuscitation and those with a functionally univentricular circulation. With the increase in familiarity with ECMO, new indications have been added, such as extracorporeal cardiopulmonary resuscitation (ECPR). The literature supporting ECPR is increasing in children. Reasonable survival rates have been achieved after initiation of support during active compressions of the chest following in-hospital cardiac arrest. Contraindications to ECLS have reduced in the last 5 years and many centers support patients with functionally univentricular circulations. Improved results have been recently achieved in this complex subset of patients.

Risk factors for specific causes of death following pediatric heart transplant: An analysis of the registry of the International Society of Heart and Lung Transplantation

We sought to determine temporal changes in COD and identify COD-specific risk factors in pediatric primary HTx recipients. Using the ISHLT registry, time-dependent hazard of death after pediatric HTx, stratified by COD, was analyzed by multiphasic parametric hazard modeling with multivariable regression models for risk factor analysis. The proportion of pediatric HTx deaths from each of cardiovascular cause, allograft vasculopathy, and malignancy increased over time, while all other COD decreased post-HTx. Pre-HTx ECMO was associated with increased risk of death from graft failure (HR 2.43; p < 0.001), infection (HR 2.85; p < 0.001), and MOF (HR 2.22; p = 0.001), while post-HTx ECMO was associated with death from cerebrovascular events/bleed (HR 2.55; p = 0.001). CHD was associated with deaths due to pulmonary causes (HR 1.78; p = 0.007) or infection (HR 1.72; p < 0.001). Non-adherence was a significant risk factor for all cardiac COD, notably graft failure (HR 1.66; p = 0.001) and rejection (HR 1.89; p < 0.001). Risk factors related to specific COD are varied across different temporal phases post-HTx. Increased understanding of these factors will assist in risk stratification, guide anticipatory clinical decisions, and potentially improve patient survival.

Extracorporeal Membrane Oxygenation as a Bridge to Pediatric Heart Transplantation: Effect on Post-Listing and Post-Transplantation Outcomes

BACKGROUND

Current organ allocation algorithms direct hearts to the sickest recipients to mitigate death while waiting. This may result in lower post-transplant (Tx) survival for high-risk candidates mandating close examination to determine the appropriateness of different technologies as a bridge to Tx.

METHODS AND RESULTS

We analyzed all patients (<18 years old) from the Pediatric Heart Transplant Study (PHTS) database listed for heart Tx (1993-2013) to determine the effect of extracorporeal membrane oxygenation (ECMO) support at the time of listing and the time of Tx on waitlist mortality and post-Tx outcomes. Eight percent of patients were listed on ECMO, and within 12 months, 49% had undergone Tx, 35% were deceased, and 16% were alive waiting. Survival at 12 months after listing (censored at Tx) was worse in patients on ECMO at listing (50%) compared with ventricular assist device at listing (76%) or not on ECMO or ventricular assist device at listing (76%; P<0.0001). Two hundred three (5%) patients underwent Tx from ECMO; 135 (67%) had been on ECMO since listing, and 67 (33%) had deteriorated to ECMO support while waiting. Survival after Tx was worse in patients who underwent Tx from ECMO (3 years: 64%) versus on ventricular assist device at Tx (3 years: 84%) or not on ECMO/ventricular assist device at Tx (3 years: 85%; P<0.0001). Patients transplanted from ECMO at age <1 year had the worst survival.

CONCLUSIONS

Pediatric patients requiring ECMO support before heart Tx have poor outcomes. Prioritization of donor hearts to children waitlisted on ECMO warrants careful consideration because of ECMO's high pre- and post-Tx mortality.

Outcomes and risk factors for heart transplantation in children with end-stage cardiomyopathy†

OBJECTIVES

Heart transplantation (HT) is the treatment of choice in children with end-stage cardiomyopathy. Several clinical, morphological, demographic, donor and recipient transplant factors have been demonstrated to affect survival in those patients following listing for HT and following HT. We aim to report our single institution results of HT in children with cardiomyopathy, and explore variables affecting survival and the need for heart retransplantation (RHT).

METHODS

Between 1988 and 2013, 125 children with cardiomyopathy underwent HT. Competing risks analysis modelled events after HT (RHT, death without RHT). Multivariable regression analysis examined risk factors affecting outcomes and parametric models were used to compare survival between diverse groups of patients.

RESULTS

There were 62 males (50%). Cardiomyopathy types were dilated (n = 104, 83%), restrictive (n = 10, 8%), chemotherapy-induced (n = 7, 6%), and other (n = 4, 3%). Median age at listing was 6.9 years and median age at HT was 7.0 years with median waiting list duration of 29 days. Thirty-four patients were infants <1 year. At time of HT, 106 patients (85%) were at United Network for Organ Sharing status-1, 25 (20%) were ventilated and 17 (14%) had mechanical circulatory support. There was 1 operative death. Competing risks analysis showed that at 10 years following HT, 10% of patients have undergone RHT, 32% have died without RHT and 58% of patients were alive without RHT. On multivariable analysis, risk factors for death following HT were panel-reactive antibodies >10% {hazard ratio [HR]: 4.1 [95% confidence interval (CI): 1.7-9.9], P = 0.002}, age group >10 years [HR: 3.2 (95% CI: 1.4-8.1), P = 0.009] and pre-HT mechanical circulatory support [HR: 2.9 (95% CI: 1.1-7.7), P = 0.033]. Additionally, earlier era <2000 was a significant risk factor for early phase mortality [HR: 8.7 (95% CI: 1.8-42.5), P = 0.017] but not for constant or late phase mortality [HR: 0.8 (95% CI 0.3-1.8), P = 0.6]. Following RHT, 6/11 (55%) expired yielding overall parametric survival estimates of 92, 77 and 57% at 1, 5 and 15 years, respectively.

CONCLUSIONS

Despite remarkable improvement in operative mortality and 1-year survival of children undergoing HT for cardiomyopathy in the current era, that advantage is reduced at the later follow-up, especially in teenagers indicating ongoing compliance and chronic management challenges. In children requiring pre-HT mechanical support, mid-term attrition is higher despite low operative mortality.

Peri-operative kidney injury and long-term chronic kidney disease following orthotopic heart transplantation in children

Significant advances in cardiac intensive care including extracorporeal life support have enabled children with complex congenital heart disease and end-stage heart failure to be supported while awaiting transplantation. With an increasing number of survivors after heart transplantation in children, the complications from long-term immunosuppression, including renal insufficiency, are becoming more apparent. Severe renal dysfunction after heart transplant is defined by a serum creatinine level >2.5 mg/dL (221 μmol/L), and/or need for dialysis or renal transplant. The degree of renal dysfunction is variable and is progressive over time. About 3-10 % of heart transplant recipients will go on to develop severe renal dysfunction within the first 10 years post-transplantation. Multiple risk factors for chronic kidney disease post-transplant have been identified, which include pre-transplant worsening renal function, recipient demographics and morbidity, peri-transplant haemodynamics and long-term exposure to calcineurin inhibitors. Renal insufficiency increases the risk of post-transplant morbidity and mortality. Hence, screening for renal dysfunction pre-, peri- and post-transplantation is important. Early and timely detection of renal insufficiency may help minimize renal insults, and allow prompt implementation of renoprotective strategies. Close monitoring and pre-emptive management of renal dysfunction is an integral aspect of peri-transplant and subsequent post-transplant long-term care.

Mechanical circulatory support for infants and small children

The number of children in need of mechanical circulatory support has increased substantially over the last two decades, due to the technological progress made in surgery and intensive care, leading to improved survival of patients with congenital heart disease. In addition, primary myocardial dysfunction related to myocarditis or dilated cardiomyopathy may cause end-stage cardiac failure in children or infants, although not as frequently as in adults. The need for mechanical circulatory support may be either temporary until spontaneous myocardial recovery, as in postcardiotomy cardiac failure, or prolonged until heart transplantation in the absence of recovery. Two types of mechanical circulatory devices are suitable for the paediatric population: extracorporeal membrane oxygenation for short-term support; and ventricular assist devices for long-term support as a bridge to transplantation. The aim of this review is to describe the specific issues related to paediatric mechanical circulatory support and the different types of devices available, to report on their rapidly growing use worldwide and on the outcomes for each indication and type of device, and to provide a perspective on the future developments and remaining challenges in this field.

Extracorporeal membrane oxygenation versus counterpulsatile, pulsatile, and continuous left ventricular unloading for pediatric mechanical circulatory support

OBJECTIVES

Despite progress with adult ventricular assist devices, limited options exist to support pediatric patients with life-threatening heart disease. Extracorporeal membrane oxygenation remains the clinical standard. To characterize (patho)physiologic responses to different modes of mechanical unloading of the failing pediatric heart, extracorporeal membrane oxygenation was compared to intra-aortic balloon pump, pulsatile-flow ventricular assist device, or continuous-flow ventricular assist device support in a pediatric heart failure model.

DESIGN

Experimental.

SETTING

Large animal laboratory operating room.

SUBJECTS

Yorkshire piglets (n = 47; 11.7 ± 2.6 kg).

INTERVENTIONS

In piglets with coronary ligation-induced cardiac dysfunction, mechanical circulatory support devices were implanted and studied during maximum support.

MEASUREMENTS AND MAIN RESULTS

Left ventricular, right ventricular, coronary, carotid, systemic arterial, and pulmonary arterial hemodynamics were measured with pressure and flow transducers. Myocardial oxygen consumption and total-body oxygen consumption were calculated from arterial, venous, and coronary sinus blood sampling. Blood flow was measured in 17 organs with microspheres. Paired Student t tests compared baseline and heart failure conditions. One-way repeated-measures analysis of variance compared heart failure, device support mode(s), and extracorporeal membrane oxygenation. Statistically significant (p < 0.05) findings included 1) an improved left ventricular blood supply/demand ratio during pulsatile-flow ventricular assist device, continuous-flow ventricular assist device, and extracorporeal membrane oxygenation but not intra-aortic balloon pump support, 2) an improved global myocardial blood supply/demand ratio during pulsatile-flow ventricular assist device and continuous-flow ventricular assist device but not intra-aortic balloon pump or extracorporeal membrane oxygenation support, and 3) diminished pulsatility during extracorporeal membrane oxygenation and continuous-flow ventricular assist device but not intra-aortic balloon pump and pulsatile-flow ventricular assist device support. A profile of systems-based responses was established for each type of support.

CONCLUSIONS

Each type of pediatric ventricular assist device provided hemodynamic support by unloading the heart with a different mechanism that created a unique profile of physiological changes. These data contribute novel, clinically relevant insight into pediatric mechanical circulatory support and establish an important resource for pediatric device development and patient selection.

Efficacy and safety of strategies to preserve stable extracorporeal life support flow during simulated hypovolemia

Aim:

Without volume-buffering capacity in extracorporeal life support (ELS) systems, hypovolemia can acutely reduce support flow. This study aims at evaluating efficacy and safety of strategies for preserving stable ELS during hypovolemia.

Material & Methods:

Flow and/or pressure-guided servo pump control, a reserve-driven control strategy and a volume buffer capacity (VBC) device were evaluated with respect to pump flow, venous line pressure and arterial gaseous microemboli (GME) during simulated normovolemia and hypovolemia.

Results:

Normovolemia resulted in a GME-free pump flow of 3.1±0.0 L/min and a venous line pressure of −10±1 mmHg. Hypovolemia without servo pump control resulted in a GME-loaded flow of 2.3±0.4 L/min with a venous line pressure of −114±52 mmHg. Servo control resulted in an unstable and GME-loaded flow of 1.5±1.2 L/min. With and without servo pump control, the VBC device stabilised flow (SD = 0.2 and 0.0 L/min, respectively) and venous line pressure (SD=51 and 4 mmHg, respectively) with near-absent GME activity. Reserve-driven pump control combined with a VBC device restored a near GME-free flow of 2.7±0.0 L/min with a venous line pressure of −9±0 mmHg.

Conclusion:

In contrast to a reserve-driven pump control strategy combined with a VBC device, flow and pressure servo control for ELS show evident deficits in preserving stable and safe ELS flow during hypovolemia.

Intensive care of the pediatric ventricular assist device patient

Utilization of ventricular assist devices (VADs) in children is increasing, as is the complexity of patients supported. We review the intensive care management of pediatric patients with VAD in the perioperative and rehabilitation phases, highlighting the technical aspects and physiology of VADs which impact care. Indications for VAD placement and the preoperative assessment of risk are discussed. Specific aspects of postoperative and long-term care including device troubleshooting, hemostasis and anticoagulation, support of the right ventricle, incidence and prevention of neurologic injury, and other complications are reviewed.

Outcomes following extracorporeal membrane oxygenation in children with cardiac disease

Extracorporeal membrane oxygenation is a commonly used form of mechanical circulatory support in children with congenital or acquired heart disease and cardiac failure refractory to conventional medical therapies. In children with heart disease who suffer cardiac arrest, extracorporeal membrane oxygenation has been successfully used to provide cardiopulmonary support when conventional resuscitation has failed to establish return of spontaneous circulation. Survival to hospital discharge for children with heart disease support is approximately 40% but varies widely based on age, indication for support, and underlying cardiac disease. Although extracorporeal membrane oxygenation is lifesaving in many instances, it is associated with many complications and is expensive. Thus, a clear understanding of survival to discharge and long-term functional and neurologic outcomes are essential to guide the use of extracorporeal membrane oxygenation now and in the future. This review, part of the Pediatric Cardiac Intensive Care Society/Extracorporeal Life Support Organization Joint Statement on Mechanical Circulatory Support, summarizes current knowledge on short- and long-term outcomes for extracorporeal membrane oxygenation used to support children with cardiac disease.

Mechanical circulatory support in children: bridge to transplant versus recovery

The number of children and adolescents suffering from heart failure is increasing dramatically. Some of these patients will progress to need advanced therapies in the form of mechanical circulatory support (MCS). Over the past few years, increased attention has been focused on clinical use of existing devices as well the development of pediatric-specific ventricular assist devices (VADs). As in adult populations, these devices offer unique opportunities to successfully support children as a bridge-to-transplant, but increasing data suggest that bridge-to-recovery and bridge-to-destination are also viable options in select pediatric populations. Herein, we will review existing approaches as well describe future potential MCS options.

Pediatric outcomes after extracorporeal membrane oxygenation for cardiac disease and for cardiac arrest: a review

We reviewed reported survival and neurological outcomes, and predictors of these outcomes for pediatric cardiac extracorporeal membrane oxygenation (ECMO) and extracorporeal cardiopulmonary resuscitation (ECPR). We searched PubMed from 2000 to April 2011. Cumulative survival after cardiac ECMO in children was 788/1755 (45%); renal dysfunction, dialysis, neurologic complication, lactate, and ECMO duration consistently predicted this outcome, whereas single ventricle and ECPR did not. Neurological outcomes after cardiac ECMO were based on poorly described telephone questions in two studies for 47 patients with 51% significantly impaired and detailed follow-up testing for 42 patients in three studies with mental delay in 38% and mental score >85 (average or above) in 33%. Cumulative survival after ECPR in children was 371/762 (49%); noncardiac disease, renal dysfunction, neurologic complication, and pH on extracorporeal life support consistently predicted this outcome, whereas duration of CPR did not. Neurological outcomes after ECPR were based predominantly on the pediatric cerebral performance category (PCPC) score by chart review, with 161/181 (79%) having PCPC <2. No study reported detailed follow-up testing for survivors of ECPR. Survival outcomes of most cardiac subgroups were similar, except for concerning mortality in cavopulmonary connection patients. Priority areas for study include identification of potentially modifiable predictors of long-term outcomes.

Outcomes of infants weighing three kilograms or less requiring extracorporeal membrane oxygenation after cardiac surgery

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is the most common form of cardiac support for postcardiotomy cardiac failure in children. While its benefits have been thoroughly explored in infants weighing more than 3 kg, similar analyses are lacking in lower weight neonates. This single-center study investigated outcomes and risks for poor survival among infants weighing 3 kg or less.

METHODS

A retrospective review of infants 3 kg or less who required postcardiotomy ECMO support was performed (January 1, 1999 to December 31, 2010). Primary outcome was 30-day survival after decannulation. Factors analyzed for association with poor outcome included demographics, cardiac anatomy, bypass and circulatory arrest times, total ECMO support time, postoperative lactate, inotrope use, and need for renal replacement therapy.

RESULTS

During the study period, 64 patients weighing 3 kg or less required postcardiotomy ECMO. Median gestational age and age at ECMO initiation were 38 weeks (interquartile range, 36 to 39) and 7 days (interquartile range, 4 to 9), respectively, with median ECMO support time of 164 hours (interquartile range, 95 to 231). Overall 30-day survival after decannulation was 33%. Factors associated with poor outcome were longer duration of support (231 hours or more, 12% survival, versus less than 231 hours, 40% survival; p = 0.05) and renal replacement therapy (n = 36, survival 17% versus 54%; p = 0.002). Multivariable regression analysis identified renal replacement therapy as the only independent factor associated with poor survival (odds ratio 4.3, 95% confidence interval: 1.3 to 14.9, p = 0.02).

CONCLUSIONS

For infants weighing 3 kg or less, 30-day survival after decannulation after cardiac ECMO is poor. Factors associated with poor prognosis were need for renal replacement therapy and longer duration of ECMO support. These findings may provide a useful guide for medical decision making among this unique, high-risk patient group.

Ventricular-assist device therapy in children

Mechanical circulatory support is an important modality in the management of paediatric patients with circulatory failure. The field of ventricular assist device (VAD) is particularly evolving. We review the currently available and developing VADs in the paediatric population, and the anaesthetic management of patients presenting for VAD implantation and with VADs for non-cardiac surgery.

20-year experience of prolonged extracorporeal membrane oxygenation in critically ill children with cardiac or pulmonary failure

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is a rescue therapy for life-threatening respiratory or circulatory failure. Although outcomes are favorable with short-term ECMO therapy, data on the outcomes of prolonged ECMO therapy in children are very limited. This study aimed to study morbidity and mortality associated with prolonged ECMO therapy (≥28 days) in children with refractory cardiac or pulmonary failure.

METHODS

We conducted a retrospective review of all children≤18 years supported with ECMO for ≥28 days between January 1991 and September 2011 at the Arkansas Children's Hospital. The data collected in our study included patient demographic information; diagnosis; indication for ECMO; ECMO support details; medical and surgical history; laboratory, microbiologic, and radiographic data; information on organ dysfunction; complications; and patient outcomes. The outcome variables evaluated in this report included survival to ECMO decannulation, survival to hospital discharge, and current survival with emphasis on neurologic, renal, pulmonary, and other end organ function.

RESULTS

During the study period, 984 events in 951 patients were supported with ECMO with a 30-day survival of 666 events (68%). Only 22 ECMO runs were ≥28 days and were eligible for inclusion in this report. The longest ECMO run in our series was 1,206 hours (50 days). The average length of ECMO run in this cohort was 855±133 hours, with a mean intensive care unit length of stay of 56±27 days. Ten patients (45%) were successfully decannulated from ECMO. Six patients (27%) were alive 30 days after decannulation, and only 4 patients (19%) survived to hospital discharge. Of the 4 survivors, only 3 patients (14%) are living to date. Of the 3 living children, 2 have significant neurologic issues with brain atrophy and developmental delay, and 1 is awaiting renal transplant; all 3 survivors have chronic lung disease.

CONCLUSIONS

This case series highlights that the prolonged use of ECMO in children with refractory cardiac failure, respiratory failure, or both is associated with low survival. Furthermore, it suggests that the survivors of prolonged ECMO runs have significant long-term sequelae.

Management of the postoperative pediatric cardiac surgical patient

OBJECTIVE

To review the salient aspects and latest advances in the management of the postoperative pediatric cardiac patient.

DATA SOURCE

A Medline-based literature source.

CONCLUSION

The practice of pediatric cardiac intensive care has evolved considerably over the last several years. These efforts are the result of a collaborative effort from all subspecialties involved in the care of pediatric patients with congenital heart disease. Discoveries and innovations that are representative of this effort include the extension of cerebral oximetry from the operating room into the critical care setting; mechanical circulatory devices designed for pediatric patients; and surgery in very low birth weight neonates. Advances such as these impact postoperative management and make the field of pediatric cardiac intensive care an exciting, demanding, and evolving discipline, necessitating the ongoing commitment of various disciplines to pursue a greater understanding of disease processes and how to best go about treating them.

Berlin Heart EXCOR Pediatric ventricular assist device Investigational Device Exemption study: study design and rationale

BACKGROUND

Currently, there are no Food and Drug Administration-approved devices available that can provide long-term mechanical circulatory support to smaller children with severe heart failure as a bridge to heart transplant (HT). In recent years, the Berlin Heart EXCOR Pediatric ventricular assist device (VAD) has emerged as a potential treatment option. Systematic data on the safety and efficacy of the EXCOR are limited.

METHODS

The Investigational Device Exemption (IDE) clinical study is designed to evaluate the safety and probable benefit of the EXCOR to support regulatory review of the device under the Humanitarian Device Exemption regulation. The study design and rationale are reviewed in light of the well-described challenges inherent in small population studies.

RESULTS

The Berlin Heart EXCOR IDE clinical study is a prospective, multicenter, single-arm, clinical cohort study. Children aged 0 to 16 years with severe heart failure (Interagency Registry for Mechanically Assisted Circulatory Support profile 1 or 2) due to 2-ventricle heart disease and actively listed for HT comprise the primary study cohort. The control population is a propensity-matched retrospective cohort of children supported with extracorporeal membrane oxygenation, the only bridge device available to smaller children before the EXCOR. The primary efficacy end point is survival to heart transplantation or recovery. The primary safety end point is the incidence of serious adverse events as defined by pediatric Interagency Registry for Mechanically Assisted Circulatory Support criteria. The study will enroll a total of 48 subjects in 2 cohorts based on body surface area (cohort 1 <0.7 m(2), cohort 2 0.7-1.5 m(2)) and is powered to show safety superiority to a prespecified performance goal of 0.25 serious adverse events per day of support. Children ineligible for the primary cohort will still have access to the device in a third compassionate-use cohort where adverse event data will be collected for additional safety characterization of the device.

CONCLUSION

The Berlin Heart IDE clinical study will be the first bridge-to-HT VAD study designed exclusively for children. It is anticipated that the study will provide important information on the safety and efficacy of the Berlin Heart EXCOR Pediatric in children while providing valuable lessons into the design and conduct of future VAD studies in children.

Mechanical circulatory support of the critically ill child awaiting heart transplantation

The majority of children awaiting heart transplantation require inotropic support, mechanical ventilation, and/or extracorporeal membrane oxygenation (ECMO) support. Unfortunately, due to the limited pool of organs, many of these children do not survive to transplant. Mechanical circulatory support of the failing heart in pediatrics is a new and rapidly developing field world-wide. It is utilized in children with acute congestive heart failure associated with congenital heart disease, cardiomyopathy, and myocarditis, both as a bridge to transplantation and as a bridge to myocardial recovery. The current arsenal of mechanical assist devices available for children is limited to ECMO, intra-aortic balloon counterpulsation, centrifugal pump ventricular assist devices, the DeBakey ventricular assist device Child; the Thoratec ventricular assist device; and the Berlin Heart. In the spring of 2004, five contracts were awarded by the National Heart, Lung and Blood Institute to support preclinical development for a range of pediatric ventricular assist devices and similar circulatory support systems. The support of early development efforts provided by this program is expected to yield several devices that will be ready for clinical trials within the next few years. Our work reviews the current international experience with mechanical circulatory support in children and summarizes our own experience since 2005 with the Berlin Heart, comparing the indications for use, length of support, and outcome between these modalities.

Extracorporeal Membrane Oxygenation for Bridge to Heart Transplantation Among Children in the United States

Background—

Extracorporeal membrane oxygenation (ECMO) has served for >2 decades as the standard of care for US children requiring mechanical support as a bridge to heart transplantation. Objective data on the safety and efficacy of ECMO for this indication are limited. We describe the outcomes of ECMO as a bridge to heart transplantation to serve as performance benchmarks for emerging miniaturized assist devices intended to replace ECMO.

Methods and Results—

Data from the Extracorporeal Life Support Organization Registry and the Organ Procurement Transplant Network database were merged to identify children supported with ECMO and listed for heart transplantation from 1994 to 2009. Independent predictors of wait-list and posttransplantation in-hospital mortality were identified. Objective performance goals for ECMO were developed. Of 773 children, the median age was 6 months (interquartile range, 1 to 44 months); 28% had cardiomyopathy; and in 38%, a bridge to transplantation was intended at ECMO initiation. Overall, 45% of subjects reached transplantation, although one third of those transplanted died before discharge; overall survival to hospital discharge was 47%. Wait-list mortality was independently associated with congenital heart disease, cardiopulmonary resuscitation before ECMO, and renal dysfunction. Posttransplantation mortality was associated with congenital heart disease, renal dysfunction, ECMO duration of >14 days, and initial ECMO indication as a bridge to recovery. In the objective performance goal cohort (n=485), patients with cardiomyopathy had the highest survival to hospital discharge (63%), followed by patients with myocarditis (59%), 2-ventricle congenital heart disease (44%) and 1-ventricle congenital heart disease (33%).

Conclusion—

Although ECMO is effective for short-term circulatory support, it is not reliable for the long-term circulatory support necessary for children awaiting heart transplantation. Fewer than half of patients bridged with ECMO survive to hospital discharge. More effective modalities for chronic circulatory support in children are urgently needed.

Mechanical support in childhood heart failure

Despite optimization of standard medical therapy, some patients with chronic heart failure will deteriorate to the point that they require hospitalization for intravenous therapies and inpatient monitoring. Once the condition is recognized, the therapeutic goals are to reverse hemodynamic derangements, correct metabolic abnormalities, and provide symptomatic relief. Achievement of these goals requires individualized care and a familiarity with the risks and benefits of particular therapies.

The evolution of patient selection criteria and indications for extracorporeal life support in pediatric cardiopulmonary failure: next time, let's not eat the bones

Bill James, baseball statistician and author, tells the story of hungry cavemen sitting about a campfire, waiting for tomatoes to ripen. One has the inspiration to throw an ox on the fire, and the first barbecue ensued and was endured. After eating, the conversation goes something like this. "There were some good parts." "Yeah, but there were some bad parts." And the smart one says, "This time, let's not eat the bones." The evolution of patient selection criteria for the use of extracorporeal support (ECLS) is a bit like those cavemen and their first barbecued ox. Extracorporeal life support technology and application to patient care is the unique result of a long standing history of ambitious attempt, evaluation, debate, collaboration and extension.

Mechanical circulatory support for infants and small children

The development of mechanical circulatory support devices for infants and small children with heart failure has significantly lagged behind the development of devices for adults. In the United States, there was really very little activity focused on the development and implementation of durable mechanical assist devices for small children until the early part of this millennium. At present, the Berlin Heart EXCOR Pediatric ventricular assist device (Berlin Heart Inc., The Woodlands, TX) is currently the only device available to provide long-term support to small children awaiting cardiac transplantation; this device is only available through either compassionate use solicitation or within the confines of an ongoing investigation device exemption trial. There are several other devices being developed at this time, but it will be years before they are tested in clinical trials. In this article, we will review the current status of mechanical circulatory support devices and therapy strategies for infants and small children presenting in acute heart failure.

Extracorporeal life support in pediatric cardiac dysfunction

BACKGROUND

Low cardiac output (LCO) after corrective surgery remains a serious complication in pediatric congenital heart diseases (CHD). In the case of refractory LCO, extra corporeal life support (ECLS) extra corporeal membrane oxygenation (ECMO) or ventricle assist devices (VAD) is the final therapeutic option. In the present study we have reviewed the outcomes of pediatric patients after corrective surgery necessitating ECLS and compared outcomes with pediatric patients necessitating ECLS because of dilatated cardiomyopathy (DCM).

METHODS

A retrospective single-centre cohort study was evaluated in pediatric patients, between 1991 and 2008, that required ECLS. A total of 48 patients received ECLS, of which 23 were male and 25 female. The indications for ECLS included CHD in 32 patients and DCM in 16 patients.

RESULTS

The mean age was 1.2 ± 3.9 years for CHD patients and 10.4 ± 5.8 years for DCM patients. Twenty-six patients received ECMO and 22 patients received VAD. A total of 15 patients out of 48 survived, 8 were discharged after myocardial recovery and 7 were discharged after successful heart transplantation. The overall mortality in patients with extracorporeal life support was 68%.

CONCLUSION

Although the use of ECLS shows a significantly high mortality rate it remains the ultimate chance for children. For better results, ECLS should be initiated in the operating room or shortly thereafter. Bridge to heart transplantation should be considered if there is no improvement in cardiac function to avoid irreversible multiorgan failure (MFO).

In vivo experience of the child-size pediatric Jarvik 2000 heart: update

Data from early in vivo experiments demonstrated that the child-size Jarvik heart was capable of providing partial to nearly complete circulatory support with acceptable adverse effects on blood. However, bearing thrombosis was responsible for device malfunction in most cases. To overcome this problem, original pin bearings were replaced with novel conical bearings. This study evaluated chronic in vivo performance of the modified child-size Jarvik heart in the pediatric setting. Six juvenile sheep were implanted with the modified child-size Jarvik heart. Cardiac and pump output were measured daily. Serial blood samples were drawn to evaluate hematology, biocompatibility, and end-organ function. End-organ damage and device thrombosis were examined at necropsy. No device malfunction occurred during animal experiments up to 70 days. Mean cardiac output of the animals was 3.4 L/min. The child-size Jarvik heart was able to deliver a blood flow ranging from 1.4 to 2.5 L/min at speed from 10,000 rpm to 14,000 rpm. Mean plasma-free hemoglobin was 9.8 +/- 5.6 mg/dl, indicating no hemolysis. Acute elevation occurred in some organ function tests after the implant surgery but returned to normal range thereafter. These indices and necropsy showed no end-organ damage. No device thrombosis was observed. The current in vivo experience shows that the modified child Jarvik 2000 heart retained its hemodynamic function and excellent biocompatibility, and the conical bearings permitted it to remain free of thrombus.

Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS)-defined morbidity and mortality associated with pediatric ventricular assist device support at a single US center: the Stanford experience

BACKGROUND

The use of ventricular assist devices (VADs) to bridge pediatric patients to heart transplantation has increased dramatically over the last 15 years. In this report, we present the largest US single-center report of pediatric VAD use to date. We present detailed descriptions of morbidity and mortality associated with VAD support, using standard Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) criteria for pediatrics to facilitate the comparison of these results to other studies.

METHODS AND RESULTS

We retrospectively identified 25 patients younger than 18 years with 27 episodes of mechanical circulatory support using VADs as bridge to heart transplantation from January 1998 to December 2007. Survival to transplant for the entire cohort was 74%. The most common major morbidities, as defined by INTERMACS criteria for a pediatric population, were respiratory failure, major localized infections, major bleeding events, hepatic dysfunction, and right heart failure. Major neurological events occurred in 48% of the study population. The median time to the first occurrence of an adverse event was less than 14 days for respiratory failure, right heart failure, major localized infection, and major bleeding. Patients who died before transplantation had significantly more adverse events per day of support than did those who were successfully transplanted. Episodes of major bleeding, tamponade, acute renal failure, respiratory failure, and right heart failure were all associated with increased risk of mortality.

CONCLUSIONS

INTERMACS criteria can be successfully used to analyze pediatric VAD outcomes. These data serve as a baseline for future studies of VAD support in children and indicate good survival rates but considerable morbidity.

Pediatric heart transplantation bridged with ventricular assist devices

Heart transplantation (HTx) is indicated in children with end-stage heart failure or complex inoperable congenital defects. Because of the shortage of pediatric donor hearts, various bridge techniques have been used in pediatric patients to prolong patient survival until a suitable heart becomes available. We reviewed medical records of several pediatric patients in whom bridging with ventricular assist devices was used. All of the patients survived HTx, and are alive and well with no neurologic sequelae. They are NYHA functional class I. Thus, morbidity and mortality were acceptable in this high-risk group of pediatric patients with a ventricular assist device bridging to HTx.

Extracorporeal membrane oxygenation for the treatment of children with severe hemodynamic alteration in perioperative cardiovascular surgery

BACKGROUND

This article summarizes the use of extracorporeal membrane oxygenation (ECMO) for the treatment of children with severe hemodynamic alteration in perioperative cardiovascular surgery.

METHODS

Four children with congenital heart disease (CHD) (3 boys and 1 girl, aged 6 days to 4 years and weighing 2.8-15 kg) associated with severe heart failure and/or hypoxemia were treated with ECMO cardiopulmonary support in perioperative cardiovascular surgery between July 2007 and July 2008. We retrospectively analyzed the medical records of the 4 children.

RESULTS

Of the 4 children, 2 survived and 2 died. The survivors were treated with venoarterial (VA) ECMO due to severe low output syndrome after arterial switch operation. They were weaned successfully from 22-hour and 87-hour ECMO support, and discharged 20 days and 58 days after ECMO explantation, respectively. The other boy treated with venovenous ECMO died of severe hypoxemia and metabolic acidosis. The other girl with VSD, treated with VA ECMO because of failure to wean from cardiopulmonary bypass, died from irreversible heart failure 11 hours after ECMO explantation. The main complications in this series included pulmonary hemorrhage, blood tamponade, surgical site bleeding, hemolysis and hyperbilirubinemia.

CONCLUSIONS

ECMO is an effective therapy for patients with severe heart failure in the perioperative cardiovascular surgery. The keys to successful ECMO are selection of indications, time to set up ECMO, and good management of complications during ECMO.

Preoperative extracorporeal membrane oxygenation as a bridge to cardiac surgery in children with congenital heart disease

BACKGROUND

The efficacy of extracorporeal membrane oxygenation (ECMO) in bridging children with unrepaired heart defects to a definitive or palliative surgical procedure has been rarely reported. The goal of this study is to report our institutional experience with ECMO used to provide preoperative stabilization after acute cardiac or respiratory failure in patients with congenital heart disease before cardiac surgery.

METHODS

A retrospective review of the ECMO database at Children's Hospital Boston was undertaken. Children with unrepaired congenital heart disease supported with ECMO for acute cardiac or respiratory failure as bridge to a definitive or palliative cardiac surgical procedure were identified. Data collection included patient demographics, indication for ECMO, details regarding ECMO course and complications, and survival to hospital discharge.

RESULTS

Twenty-six patients (18 male, 8 female) with congenital heart disease were bridged to surgical palliation or anatomic repair with ECMO. Median age and weight at ECMO cannulation were, respectively, 0.12 months (range, 0 to 193) and 4 kg (range, 1.8 to 67 kg). Sixteen patients (62%) survived to hospital discharge. Variables associated with mortality included inability to decannulate from ECMO after surgery (p = 0.02) and longer total duration of ECMO (p = 0.02). No difference in outcomes was found between patients with single and biventricular anatomy.

CONCLUSIONS

Extracorporeal membrane oxygenation, used as a bridge to surgery, represents a useful modality to rescue patients with failing circulation and unrepaired complex heart defects.

Bridge to cardiac transplant in children: Berlin Heart versus extracorporeal membrane oxygenation

BACKGROUND

For small children requiring mechanical circulatory support as a bridge to transplantation (BTT), extracorporeal membrane oxygenation (ECMO) has been the only option until the recent introduction of the Berlin Heart EXCOR ventricular assist device (Berlin Heart AG, Berlin, Germany). We reviewed our recent experience with these two technologies with particular focus on early outcomes.

METHODS

Data for 55 consecutive children undergoing BTT between 2001 and 2008 were abstracted from an institutional database. The analysis excluded 13 patients because EXCOR was not used for acute postcardiotomy BTT. Patients were divided into ECMO (n = 21) and EXCOR groups (n = 21). Specific end points included survival to transplant, overall survival, and bridge to recovery. Incidences of adverse events and the duration of support were determined.

RESULTS

Groups were similar in weight, age, and etiologies of heart failure. Likewise, the incidences of stroke and multisystem organ failure were similar. Survival to transplant, recovery, or continued support was 57% in ECMO and 86% in EXCOR (p = 0.040). EXCOR patients had overall significantly better survival (p = 0.049). Two ECMO patients and 1 EXOR patient were bridged to recovery. The mean duration of support was 15 +/- 12 days in the ECMO group and 42 +/- 43 days in the EXCOR group (p < 0.001).

CONCLUSIONS

In children requiring BTT, EXCOR provided substantially longer support times than ECMO, without significant increase in the rates of stroke or multisystem organ failure. Survival to transplant and long-term survival was higher with EXCOR.