Pediatric ventricular assist devices: current challenges and future prospects

Nutritional status and cannula infections in pediatric patients on ventricular assist device support

BACKGROUND

Ventricular assist devices (VADs) are used to bridge pediatric patients to heart transplantation. Paracorporeal VADs require the placement of cannulas, which can create an environment for infections. We examined cannula infections in pediatric VAD patients and the role of nutritional status.

METHODS

This retrospective study (2005-2021) included patients <20 years old on VAD support using Berlin Heart EXCOR® cannulas. Cannula infections were defined by a positive culture and need for antibiotic therapy. Malnutrition was defined using the American Society of Parenteral and Enteral Nutrition guidelines as well as the Michigan MTool.

RESULTS

There were 76 patients with a median age at implant of 0.9 years (IQR 0.4, 3.6), 50% male, with 73.7% having non-congenital heart disease. More than one-quarter (26.3%) of patients developed a cannula infection. Higher pre-implant weight (OR = 1.93, p = 0.05), creatinine (OR = 1.02, p = 0.044), and pre-albumin (OR = 15.79, p = 0.025), as well as duration of VAD support (OR = 1.01; p = 0.003) were associated with increased odds of developing a cannula infection. There was no difference in the malnutrition parameters between those with and without an infection.

CONCLUSIONS

Further exploration in a larger cohort is needed to see whether these associations remain and if the incorporation of objective measures of nutritional status at the time of infection are predictive.

Impact of center volume on outcomes after ventricular assist device implantation in pediatric patients: An analysis of the STS-Pedimacs database

BACKGROUND

To date, no pediatric studies have highlighted the impact of center's ventricular assist device (VAD) volumes on post implant outcomes.

METHODS

Children (age <19) enrolled in Pedimacs undergoing initial left ventricular assist device implantation from 2012 to 2020 were included. Center volume was analyzed as a continuous and categorical variable. For categorical analysis, center volumes were divided as: low volume (1-15 implants), medium volume (15-30 implants), and high volume (>30 implants) during our study period. Patient characteristics and outcomes were compared by center's VAD volumes.

RESULTS

Of 44 centers, 16 (36.4%) were low, 11 (25%) were medium, and 17 (38.6%) were high-volume centers. Children at high-volume centers were least likely intubated, sedated, or paralyzed, and most likely ambulating preimplant (p < 0.05 for all). Center's VAD volumes were not a significant risk factor for mortality post implant when treated as a continuous or a categorical variable (p > 0.05). Compared to low volume, children at high-volume centers had fewer early neurological events. Compared to medium volume, those at high-volume centers had fewer late bleeding events (p < 0.05 for all). There were no significant differences in survival after an adverse event by hospital volumes (p > 0.05).

CONCLUSIONS

Although hospital volume does not affect post-VAD implant mortality, pediatric centers with higher VAD volumes have fewer patients intubated, sedated, paralyzed pre implant, and have lower adverse events. Failure to rescue was not significantly different between low, medium, and high-volume VAD centers.

Long-term kidney outcomes in pediatric continuous-flow ventricular assist device patients

BACKGROUND

Continuous-flow ventricular assist devices (CF-VADs) are used increasingly in pediatric end-stage heart failure (ESHF) patients. Alongside common risk factors like oxidant injury from hemolysis, non-pulsatile flow constitutes a unique circulatory stress on kidneys. Post-implantation recovery after acute kidney injury (AKI) is commonly reported, but long-term kidney outcomes or factors implicated in the evolution of chronic kidney disease (CKD) with prolonged CF-VAD support are unknown.

METHODS

We studied ESHF patients supported > 90 days on CF-VAD from 2008 to 2018. The primary outcome was CKD (per Kidney Disease Improving Global Outcomes (KDIGO) criteria). Secondary outcomes included AKI incidence post-implantation and CKD evolution in the 6-12 months of CF-VAD support.

RESULTS

We enrolled 134 patients; 84/134 (63%) were male, median age was 13 [IQR 9.9, 15.9] years, 72/134 (54%) had preexisting CKD at implantation, and 85/134 (63%) had AKI. At 3 months, of the 91/134 (68%) still on a CF-VAD, 34/91 (37%) never had CKD, 13/91 (14%) developed de novo CKD, while CKD persisted or worsened in 49% (44/91). Etiology of heart failure, extracorporeal membrane oxygenation use, duration of CF-VAD, AKI history, and kidney replacement therapy were not associated with different CKD outcomes. Mortality was higher in those with AKI or preexisting CKD.

CONCLUSIONS

In the first multicenter study to focus on kidney outcomes for pediatric long-term CF-VAD patients, preimplantation CKD and peri-implantation AKI were common. Both de novo CKD and worsening CKD can happen on prolonged CF-VAD support. Proactive kidney function monitoring and targeted follow-up are important to optimize outcomes.

Pediatric mechanical circulatory support - a review

The history of mechanical circulatory support began in 1953, as the first heart-lung machine enabled surgeons to perform complex open heart surgery. Heart failure is more prevalent in adults than pediatric patients which has led to the development of devices for adults with end-stage heart failure at a faster pace. Pediatric mechanical circulatory support has been derived from adult durable devices and subsequently applied in the adolescent population. The application of adult devices in children is inherently problematic due to size mismatch, especially in smaller patients. There has been an increasing interest in developing durable pumps that are appropriate for children for several reasons, with the primary factor being the number of children with end-stage heart failure far exceeding the number of potential donors. Mechanical circulatory support (MCS) for children can be divided into short-term temporary support and long-term durable support. The goal of this review is to discuss the devices available for the pediatric population and review the options for support in complex patients including single-ventricle anatomy, biventricular support, and total artificial heart options. We will also briefly discuss the Pumps for Kids, Infants, and Neonates (PumpKIN) Trial and MCS registries, including the Advanced Cardiac Therapies Improving Outcomes Network (ACTION).

Blood-contacting magnetic levitation bearing design using computational fluid dynamics for haemocompatibility

The Hemocompatibility Assessment Platform (HAP) is a testing rig that will allow for the evaluation of blood trauma caused by individual components of rotary blood pumps including the NeoVAD - a proposed paediatric Left Ventricular Assist Device (LVAD). It is important that the HAP itself is only minimally haemolytic such that the plasma free haemoglobin measured can be assumed to come from the test component. In this study, Computational Fluid Dynamics simulations have been carried out to inform the design of a magnetically levitated motor bearing gap. Simulations show that issues with the original design, namely stagnation regions and large recirculation zones can be mitigated with the introduction of a pipe that introduces blood-flow to the centre of the bearing and disrupts the secondary flow patterns that cause these issues.Clinical relevance- The consequent reduction in shear exposure time will reduce heamolsyis from the HAP. The redesign of the bearing will result in reduced baseline blood trauma from the HAP, thus allowing quantification of test component haemolysis and will therefore aid the design of future paediatric LVADs.

Dissipated energy and efficiency as objective functions for the design of the NeoVAD rotary blood pump

Minimising haemolytic blood damage is an important objective when designing rotary blood pumps, however, calculating haemolysis can be computationally expensive and inaccurate. Efficiency and dissipated energy are much more easily calculable hydraulic parameters in the design and analysis of rotary blood pumps and although there is work to suggest that efficiency is not a good indicator of haemocompatibility, i.e. more efficient pumps do not necessarily cause less damage, there is recent speculation that dissipated energy can act as an easily calculable haemolysis analogue.This study shows that for design purposes, optimising for maximum efficiency and minimum dissipated energy are functionally the same as they are inherently and closely linked. Moreover a demonstration of rotary blood pump design has been completed using the NeoVAD paediatric left ventricular assist device optimising for both objective functions. The resulting designs appear similar in rotor blade shape and are similar in hydraulic performance.Clinical relevance- This reinforces the direct link between efficiency and dissipated energy when analysing rotary blood pumps at a given design operating point. This raises questions either of the claim that efficiency cannot be used as an easily calculable analogue for haemolysis or the validity of dissipated energy to act in this same manner.

Machine learning based on computational fluid dynamics enables geometric design optimisation of the NeoVAD blades

The NeoVAD is a proposed paediatric axial-flow Left Ventricular Assist Device (LVAD), small enough to be implanted in infants. The design of the impeller and diffuser blades is important for hydrodynamic performance and haemocompatibility of the pump. This study aimed to optimise the blades for pump efficiency using Computational Fluid Dynamics (CFD), machine learning and global optimisation. Meshing of each design typically included 6 million hexahedral elements and a Shear Stress Transport turbulence model was used to close the Reynolds Averaged Navier-Stokes equations. CFD models of 32 base geometries, operating at 8 flow rates between 0.5 and 4 L/min, were created to match experimental studies. These were validated by comparison of the pressure-flow and efficiency-flow curves with those experimentally measured for all base prototype pumps. A surrogate model was required to allow the optimisation routine to conduct an efficient search; a multi-linear regression, Gaussian Process Regression and a Bayesian Regularised Artificial Neural Network predicted the optimisation objective at design points not explicitly simulated. A Genetic Algorithm was used to search for an optimal design. The optimised design offered a 5.51% increase in efficiency at design point (a 20.9% performance increase) as compared to the best performing pump from the 32 base designs. An optimisation method for the blade design of LVADs has been shown to work for a single objective function and future work will consider multi-objective optimisation.

Perioperative Outcomes in Patients With Failing Single-Ventricle Physiology Undergoing Ventricular Assist Device Placement: A Single Institutional Experience

OBJECTIVE

To address the current lack of specified data existing regarding the perioperative characteristics and outcomes in a novel patient population, which may bridge the current understanding of how patient characteristics and perioperative management may influence the postoperative hospital course before cardiac transplantation.

DESIGN

A retrospective electronic chart review included all patients with failing single- ventricle (SV) physiology receiving ventricular assist device (VAD) support at a high-volume pediatric VAD center between April 5, 2010, and December 1, 2020, using institution-based electronic medical records for retrospective analysis.

SETTING

At a single pediatric hospital.

PARTICIPANTS

Fourteen pediatric patients with failing SV physiology receiving ventricular assist device therapy (SVAD).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Preoperative, intraoperative, and postoperative patient demographic and medical data were obtained from prior inpatient progress notes, laboratory values, anesthetic records, cardiac catheterization reports, echocardiography reports, and postoperative surgical notes entered during inpatient encounters at the time of SVAD placement. Between April 5, 2010, and December 1, 2020, 16 VAD device implants supported 14 pediatric patients with failing SV physiology. Most patients presented with a preoperative diagnosis of hypoplastic left heart syndrome (N = 9, 64.3%). A total of 6 patients expired on VAD therapy (43%), 7 (50%) survived to receive a cardiac transplant, and 1 patient currently remains on device therapy.

CONCLUSION

Although our institutional approach represents a single perspective, we anticipate that our experience institutional experience may prove helpful to others caring for peditric patients with single ventricle physiology undergoing ventricular assist device placement and promote collaborative efforts to improve their care.

An Up-to-Date Literature Review on Ventricular Assist Devices Experience in Pediatric Hearts

Ventricular assist devices (VAD) have gained popularity in the pediatric population during recent years, as more and more children require a heart transplant due to improved palliation methods, allowing congenital heart defect patients and children with cardiomyopathies to live longer. Eventually, these children may require heart transplantation, and ventricular assist devices provide a bridge to transplantation in these cases. The FDA has so far approved two types of device: pulsatile and continuous flow (non-pulsatile), which can be axial and centrifugal. Potential eligible studies were searched in three databases: Medline, Embase, and ScienceDirect. Our endeavor retrieved 16 eligible studies focusing on five ventricular assist devices in children. We critically reviewed ventricular assist devices approved for pediatric use in terms of implant indication, main adverse effects, and outcomes. The main adverse effects associated with these devices have been noted to be thromboembolism, infection, bleeding, and hemolysis. However, utilizing left VAD early on, before end-organ dysfunction and deterioration of heart function, may give the patient enough time to recuperate before considering a more long-term solution for ventricular support.

Numerical and Experimental Analysis for a Magnetic Levitation System in a Hemocompatibility Assessment Platform

Development of pediatric left ventricular assist devices (LVADs) has lagged behind that of adult LVADs, primarily due to the size and hemocompatibility constraints of pediatric anatomy. To quantify sources of blood trauma during LVAD development, we proposed a hemocompatibility assessment platform (HAP) that can evaluate the hemocompatibility of individual components of LVADs. To eliminate the hemolysis induced by the HAP itself, we incorporated passive magnetic (PM) bearings to suspend the rotor radially and an active magnetic bearing (AMB) to control the axial position. In this study, we numerically evaluated AMB forces of 2 geometries and validated the model by comparing its predictions with experimental results. The magnetic forces generated by the AMB were evaluated by increasing the rotor-stator gap from 0.1 mm to 0.5 mm with a 0.1 mm increment and by varying the coil current from -2 A to 2 A with a 1 A increment. The average error of the numerical models was 8.8% and 7.0% for the two geometries, respectively. Higher errors were found at smaller (<0.2mm) rotor-stator gaps. For both biasing ring sizes, the AMB exhibits high magnetic stiffness from -1 A to 1 A, though it saturates for currents of -2 A and 2 A. This region of high current stiffness was identified as the optimal control region. In future work, this function will be used to tune a control algorithm to modulate current supplied to the AMB, ultimately stabilizing the rotor axially. Clinical Relevance- This work furthers the development of a hemocompatibility assessment platform that will enhance and accelerate the development of adult and pediatric LVADs.

Computational Evaluation of Cardiac Function in Children Supported with Heartware VAD, HeartMate 2 and HeartMate 3 Left Ventricular Assist Devices

Heart failure is one of the principal causes of morbidity and mortality in children. Treatment techniques may not work, and heart transplantation may be required as a result. The current state of donor-organ supply means that many patients cannot undergo transplantation. In these patients, ventricular assist devices (VADs) may be used to bridge the time until the transplantation. Continuous-flow VADs are increasingly being implanted to paediatric patients. The aim of this study was to evaluate cardiac function in children supported with Heartware HVAD, HeartMate2 and HeartMate3 devices using computational simulations. A lumped-parameter model simulating cardiac function in children around 12 years of age was used to simulate dilated cardiomyopathy and heart-pump support. The operating speeds in HVAD, HeartMate2 and HeartMate3 were selected as 2600 rpm, 8700 rpm and 5200 rpm constant speed, respectively, while the Lavare cycle and artificial-pulse modes were used to generate mean pump outputs at around 4.40 L/min and mean arterial pressures at around 82 mmHg in each device. Aortic pulse pressure was 11 mmHg, 14 mmHg and 6 mmHg under HVAD, HeartMate2 and HeartMate3 support, respectively. HVAD’s Lavare cycle and HeartMate3’s artificial pulse increased aortic pulse pressure to 15 mmHg and 20 mmHg. HeartMate3 with artificial-pulse mode may be more beneficial in reducing arterial-pulsatility-associated problems.

Development of Inspired Therapeutics Pediatric VAD: Computational Analysis and Characterization of VAD V3

PURPOSE

Pediatric heart failure patients remain in critical need of a dedicated mechanical circulatory support (MCS) solution as development efforts for specific pediatric devices continue to fall behind those for the adult population. The Inspired Pediatric VAD is being developed as a pediatric specific MCS solution to provide up to 30-days of circulatory or respiratory support in a compact modular package that could allow for patient ambulation during treatment.

METHODS

Hydrodynamic performance (flows, pressures), impeller/rotor mechanical properties (torques, forces), and flow shear stress and residence time distributions of the latest design version, Inspired Pediatric VAD V3, were numerically predicted and investigated using computational fluid dynamics (CFD) software (SolidWorks Flow Simulator).

RESULTS

Hydrodynamic performance was numerically predicted, indicating no change in flow and pressure head compared to the previous device design (V2), while displaying increased impeller/rotor torques and translation forces enabled by improved geometry. Shear stress and flow residence time volumetric distributions are presented over a range of pump rotational speeds and flow rates. At the lowest pump operating point (3000 RPM, 0.50 L/min, 75 mmHg), 79% of the pump volume was in the shear stress range of 0-10 Pa with < 1% of the volume in the critical range of 150-1000 Pa for blood damage. At higher speed and flow (5000 RPM, 3.50 L/min, 176 mmHg), 65% of the volume resided in the 0-10 Pa range compared to 2.3% at 150-1000 Pa.

CONCLUSIONS

The initial computational characterization of the Inspired Pediatric VAD V3 is encouraging and future work will include device prototype testing in a mock circulatory loop and acute large animal model.

Trends in Body Mass Index and Association With Outcomes in Pediatric Patients on Continuous Flow Ventricular Assist Device Support

Data are limited regarding body mass index (BMI) in pediatric patients supported by ventricular assist devices (VAD) and associated clinical outcomes and complications. We performed a retrospective single-center cohort study including patients aged ≤21 years on durable continuous-flow VAD support for ≥30 days from 2009 to 2020. Patients were classified based on BMI percentile at implant using the US Centers for Disease Control and Prevention criteria: underweight (<5th percentile), healthy weight (5th-<85th percentile, reference group), overweight (85th-<95th percentile), and obese (≥95th percentile). Primary outcomes were hospital mortality and length of stay (LOS) after implant. Secondary outcomes included infectious complications and pump thrombosis. Seventy-two patients (58 HeartWare, 13 HeartMateII, 1 HeartMate3) were included. At implant, the study cohort comprised 13% underweight, 53% healthy weight, 18% overweight, and 17% obese. BMI increased across all categories during support, with 29% gaining BMI categories. No patients with obesity reduced their BMI category. At explant, the study cohort comprised 1% underweight, 54% healthy weight, 22% overweight, and 22% obese. There was no significant difference in hospital mortality, postoperative LOS, or pump thrombosis. Patients who were overweight had more frequent non-VAD infections. Patients with obesity required longer duration on VAD support and were less likely to be transplanted. We concluded that pediatric patients on VAD support who are overweight or have obesity do not improve their BMI and instead have significant increase. Larger studies are needed to assess the impact of abnormal BMI on VAD complications in pediatric patients.

3D Holographic Virtual Surgical Planning for a Single Right Ventricle Fontan Patient Needing Heartmate III Placement

A 15 year old female with hypoplastic left heart syndrome status post Norwood with Sano modification, bidirectional Glenn and extracardiac conduit Fontan developed severe right ventricular (RV) systolic dysfunction. Due to symptomatic heart failure, she underwent assessment for ventricular assist device (VAD) placement as a bridge-to-cardiac transplantation strategy. To evaluate her atypical anatomy, a chest computed tomography (CT) was uploaded into an EchoPixel True3D (Santa Clara, CA) view portal along with an accurately scaled 3D surface model of the HeartMate III (HM3) device. The surgeon then manipulated the position of the HM3 to evaluate multiple potential device positions in relation to anatomic features such as the intraventricular septum, tricuspid valve annulus, and RV muscle bundles. The patient was taken to the operating room and the HM3 device was placed just anterior to the RV apex as virtually planned. She had an uneventful postoperative course, underwent cardiac transplantation on postoperative day (POD) 63 and is doing well now 19 months post-transplantation.

Ventricular assist devices in paediatric cardiomyopathy and congenital heart disease: An analysis of the German National Register for Congenital Heart Defects

BACKGROUND

Ventricular assist devices (VAD) are increasingly used in patients with end-stage heart failure due to acquired heart disease. Limited data exists on the use and outcome of this technology in children.

METHODS

All children (<18 years of age) with VAD support included in the German National Register for Congenital Heart Defects were identified and data on demographics, underlying cardiac defect, previous surgery, associated conditions, type of procedure, complications and outcome were collected.

RESULTS

Overall, 64 patients (median age 2.1 years; 45.3% female) receiving a VAD between 1999 and 2015 at 8 German centres were included in the analysis. The underlying diagnosis was congenital heart disease (CHD) in 25 and cardiomyopathy in 39 children. The number of reported VAD implantations increased from 13 in the time period 2000-2004 to 27 implantations in the time period 2010-2014. During a median duration of VAD support of 54 days, 28.1% of patients experienced bleeding complications (6.3% intracerebral bleeding), 14.1% thrombotic (10.9% VAD thrombosis) and 23.4% thromboembolic complications (including cerebral infarction in 18.8% of patients). Children with cardiomyopathy were more likely to receive a cardiac transplantation (79.5% vs. 28.0%) compared to CHD patients. Survival of cardiomyopathy patients was significantly better compared to the CHD cohort (p < 0.0001). Multivariate Cox-proportional analysis revealed a diagnosis of CHD (hazard ratio [HR] 4.04, p = 0.001), age at VAD implantation (HR 1.09/year, p = 0.04) and the need for pre-VAD extracorporeal membrane oxygenation (ECMO) support (HR 3.23, p = 0.03) as independent predictors of mortality.

CONCLUSIONS

The uptake of VAD therapy in children is increasing. Morbidity and mortality remain high, especially in patients with congenital heart disease and those requiring ECMO before VAD implantation.

Impact of Age on Emergency Resource Utilization and Outcomes in Pediatric and Young Adult Patients Supported with a Ventricular Assist Device

There are minimal data describing outcomes in ambulatory pediatric and young adult ventricular assist device (VAD)-supported patient populations. We performed a retrospective analysis of encounter-level data from 2006 to 2017 Nationwide Emergency Department Sample (NEDS) to compare emergency department (ED) resource utilization and outcomes for pediatric (≤18 years, n = 494) to young adult (19-29 years, n = 2,074) VAD-supported patient encounters. Pediatric encounters were more likely to have a history of congenital heart disease (11.3% vs. 4.8%). However, Pediatric encounters had lower admission/transfer rates (37.8% vs. 57.8%) and median charges ($3,334 (IQR $1,473-$19,818) vs. $13,673 ($3,331-$45,884)) (all p < 0.05). Multivariable logistic regression modeling revealed that age itself was not a predictor of admission, instead high acuity primary diagnoses and medical complexity were: (adjusted odds ratio; 95% confidence intervals): cardiac (3.0; 1.6-5.4), infection (3.4; 1.7-6.5), bleeding (3.9; 1.7-8.8), device complication (7.2; 2.7-18.9), and ≥1 chronic comorbidity (4.1; 2.5-6.7). In this largest study to date describing ED resource use and outcomes for pediatric and young adult VAD-supported patients, we found that, rather than age, high acuity presentations and comorbidities were primary drivers of clinical outcomes. Thus, reducing morbidity in this population should target comorbidities and early recognition of VAD-related complications.

Virtual reality-guided left ventricular assist device implantation in pediatric patient: Valuable presurgical tool

Virtual reality (VR) is increasingly used for presurgical planning and teaching during surgery. However, VR aided presurgical planning toolbox for left ventricular assist device (LVAD) implantation is not widely available. We investigated the use of a VR environment with wearable headsets and touch controllers in simulating an implant in an 11-year-old boy. The technology played a significant role in the optimal positioning of the LVAD.

Design and Computational Evaluation of a Pediatric MagLev Rotary Blood Pump

Pediatric heart failure (HF) patients have been a historically underserved population for mechanical circulatory support (MCS) therapy. To address this clinical need, we are developing a low cost, universal magnetically levitated extracorporeal system with interchangeable pump heads for pediatric support. Two impeller and pump designs (pump V1 and V2) for the pediatric pump were developed using dimensional analysis techniques and classic pump theory based on defined performance criteria (generated flow, pressure, and impeller diameter). The designs were virtually constructed using computer-aided design (CAD) software and 3D flow and pressure features were analyzed using computational fluid dynamics (CFD) analysis. Simulated pump designs (V1, V2) were operated at higher rotational speeds (~5,000 revolutions per minute [RPM]) than initially estimated (4,255 RPM) to achieve the desired operational point (3.5 L/min flow at 150 mm Hg). Pump V2 outperformed V1 by generating approximately 30% higher pressures at all simulated rotational speeds and at 5% lower priming volume. Simulated hydrodynamic performance (achieved flow and pressure, hydraulic efficiency) of our pediatric pump design, featuring reduced impeller size and priming volume, compares favorably to current commercially available MCS devices.

Outcomes From Three Decades of Infant and Pediatric Heart Transplantation

Infants are a unique transplant population due to a suspected immunologic advantage, in addition to differences in size and physiology. Consequently, we expect infants to have significantly different diagnoses, comorbidities, and outcomes than pediatric transplant recipients. In this study, we compare patterns and trends in pediatric and infant heart transplantation during three decades. The United Network for Organ Sharing (UNOS) database was queried for transplants occurring between January 1990 and December 2018. Patients were categorized as pediatric (1-17) or infant (0-1). Congenital heart disease (CHD) primary diagnoses have increased from 37% to 42% in pediatric patients (p = 0.001) and decreased from 80% to 61% in infants during the 1990s and 2010s (p < 0.001). Those with CHD had worse outcomes in both age groups (p < 0.001). Infants who underwent ABO-incompatible transplants had similar survival as compared to those with compatible transplants (p = 0.18). Overall, infants had better long-term survival and long-term graft survival than pediatric patients; however, they had worse short-term survival (p < 0.001). Death due to rejection or graft failure was less likely in infants (p = 0.034). However, death from infection was over twice as common (p < 0.001). In summary, pediatric and infant heart transplant recipients differ in diagnoses, comorbidities, and outcomes, necessitating different care for these populations.

Ethical and practical dilemmas in cardiac transplantation in infants: a literature review

The waiting time in infants for a cardiac transplant remains high, due to the scarcity of donors. Consequently, waiting list morbidity and mortality are higher than those in other age groups. Therefore, the decision to list a small infant for cardiac transplantation is seen as an ethical dilemma by most physicians. This review aims to describe outcomes, limitations, and ethical considerations in infant heart transplantation. We used Medline and Embase as data sources. We searched for publications on infant (< 1 year) heart transplantation, bridge-to-transplant and long-term outcomes, and waiting list characteristics from January 2009 to March 2021. Outcome after cardiac transplant in infants is better than that in older children (1-year survival 88%), and complications are less frequent (25% CAV, 10% PTLD). The bridge-to-transplant period in infants is associated with increased mortality (32%) and decreased transplantation rate (43%). This is mainly due to MCS complications or the limited MCS options (with 51% mortality in infancy). Outcomes are worse for infants with CHD or in need of ECMO-support.Conclusion: Infants listed for cardiac transplantation have a high morbidity and mortality, especially in the period between diagnosis and transplantation. For those who receive cardiac transplant, the outlook is encouraging. Unfortunately, despite growing experience in VAD, mortality in children < 10 kg and children with CHD remains high. After transplantation, patients carry a psychological burden and there is a probability of re-transplantation later in life, with decreased outcomes compared to primary transplantation. These considerations are seen as an important ethical dilemma in many centers, when considering cardiac transplantation in infants (< 1 year). What is Known: • For infants, waitlist mortality remains high. In the pediatric population, MCS reduces the waiting list mortality. What is New: • Outcomes after infant cardiac transplantation are better than other age groups; however, MCS options remain limited, with persistently high waiting list mortality. • Future developments in MCS and alternative options to reduce waiting list mortality such as ABO-incompatible transplantation and pulmonary artery banding are encouraging and will improve ethical decision-making when an infant is in need of a cardiac transplant.

In vitro Hemocompatibility Evaluation of the HeartWare Ventricular Assist Device Under Systemic, Pediatric and Pulmonary Support Conditions

The development of adult use right ventricular assist devices (RVADs) and pediatric left ventricular assist devices (pediatric LVADs) have significantly lagged behind compared to adult use left ventricular assist devices (LVADs). The HeartWare ventricular assist device (HVAD) intended to be used for adult's systemic support, is increasingly used off-label for adult pulmonary and pediatric systemic support. Due to different hemodynamics and physiology, however, the HVAD's hemocompatibility profiles can be drastically different when used in adult pulmonary circulation or in children, compared to its intended usage state, which could have a direct clinical and developmental relevance. Taking these considerations in mind, we sought to conduct in vitro hemocompatibility testing of HVAD in adult systemic, pediatric systemic and adult pulmonary support conditions. Two HVADs coupled to custom-built blood circulation loops were tested for 6 hours using bovine blood at 37°C under adult systemic, pediatric systemic, and adult pulmonary flow conditions (flow rate = 5.0, 2.5, and 4.5 L/min; differential pressure = 100, 69, and 20 mm Hg, respectively). Normalized index of hemolysis for adult systemic, pediatric systemic, and adult pulmonary conditions were 0.0083, 0.0039, and 0.0017 g/100 L, respectively. No significant difference was seen in platelet activation for these given conditions. High molecular weight von Willebrand factor multimer degradation was evident in all conditions (p < 0.05). In conclusion, alterations in the usage mode produce substantial differences in hemocompatibility of the HVAD. These findings would not only have clinical relevance but will also facilitate future adult use RVAD and pediatric LVAD development.

Kidney replacement therapy in pediatric patients on mechanical circulatory support: challenges for the pediatric nephrologist

The use of mechanical circulatory support (MCS) therapies in children with medically refractory cardiac failure has increased over the past two decades. With the growing experience and expertise, MCS is currently offered as a bridge to recovery or heart transplantation and in some cases even as destination therapy. Acute kidney injury (AKI) is common in patients with end-stage heart failure (ESHF). When severe AKI develops requiring kidney replacement therapy (KRT), these patients present unique challenges for the pediatric nephrology team. The use of KRT has not been adequately described in children with ESHF on the newer MCS. We also present original case series data from our center experience. The purpose of this review is to familiarize the reader with the current MCS technologies, approach to their selection, how they interact when combined with current KRT circuits, and distinguish similarities and differences. We will attempt to highlight the distinctive features of each technology, specifically focusing on growing trends in use of continuous-flow ventricular assist devices (CF-VAD) as it poses additional challenges to the pediatric nephrologist.

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 Support for The Failing Single Ventricle at Pre-Fontan Stage: Current State of The Field and Future Directions

With the substantial growth of pediatric ventricular assist device (VAD) support, there has been an expansion of the target population towards more complex patients, including congenital heart disease (CHD) with single ventricle (SV) physiology. The outcomes of Stage I and Stage II SV-CHD patients on VAD support from the Pedimacs database are poor, with less than 50% survival on VAD by the 3-month mark in both. The primary objective of this article is to describe the current state of VAD support for the failing Stage I and II SV-CHD circulation, to provide insight into potential areas of outcome improvement. We reviewed the published literature in the form of database and registry reports as well as single-center studies to discuss the outcomes of Stage I and Stage II SV-CHD patients on VAD support. Registry-based studies suggest that VAD support for the failing Stage I and Stage II SV-CHD circulations is challenging. However, the more promising outcomes in several single-institutional reports for both Stage I and Stage II SV-VAD indicate that the grim picture from the databases does not reflect the best outcomes that are possible to be achieved, potentially at experienced centers with higher volumes. Areas of future study and potential improvement including timely initiation of VAD support in the cohort of patients expected to not be a candidate for standard SV palliations, pump selection and the benefits of continuous-flow devices, and the decision-making for setting up the optimum circulation for VAD support, be it Fontan completion if feasible or takedown to shunt physiology.

Epidemiology and Outcomes of Acute Decompensated Heart Failure in Children

BACKGROUND

Acute decompensated heart failure (ADHF) is a highly morbid condition among adults. Little is known about outcomes in children with ADHF. We analyzed the Pediatric Cardiac Critical Care Consortium registry to determine the epidemiology, contemporary treatments, and predictors of mortality in critically ill children with ADHF.

METHODS

Cardiac intensive care unit (CICU) patients ≤18 years of age meeting Pediatric Cardiac Critical Care Consortium criteria for ADHF were included. ADHF was defined as systolic or diastolic dysfunction requiring continuous vasoactive or diuretic infusion, respiratory support, or mechanical circulatory support. Demographics, diagnosis, therapies, complications, and mortality are described for the cohort. Predictors of CICU mortality were identified using logistic regression.

RESULTS

Among 26 294 consecutive admissions (23 centers), 1494 (6%) met criteria for analysis. Median age was 0.93 years (interquartile range, 0.1-9.3 years). Patients with congenital heart disease (CHD) comprised 57% of the cohort. Common therapies included the following: vasoactive infusions (88%), central venous catheters (86%), mechanical ventilation (59%), and high flow nasal cannula (46%). Common complications were arrhythmias (19%), cardiac arrest (10%), sepsis (7%), and acute renal failure requiring dialysis (3%). Median length of CICU stay was 7.9 days (interquartile range, 3-18 days) and the CICU readmission rate was 22%. Overall, CICU mortality was 15% although higher for patients with CHD versus non-CHD (19% versus 11%; P<0.001). Independent risk factors associated with CICU mortality included age <30 days, CHD, vasoactive infusions, ventricular tachycardia, mechanical ventilation, sepsis, pulmonary hypertension, extracorporeal membrane oxygenation, and cardiac arrest.

CONCLUSIONS

ADHF in children is characterized by comorbidities, high mortality rates, and frequent readmission, especially among patients with CHD. Opportunities exist to determine best practices around appropriate use of mechanical support, cardiac arrest prevention, and optimal heart transplantation candidacy to improve outcomes for these patients.

Implantation of a HeartMate 3 in a 13-Year-Old Child with Dilated Cardiomyopathy

Left ventricular assist device is a well-established therapy in heart failure adults, but less in children. A 13-year-old-boy with severe left ventricular dysfunction did not improve under medical treatment. A HeartMate 3 (HM3) was implanted as a bridge to transplantation. Despite the size limitation, the HM3 shows promising results and our case supports its feasibility in children.

Paving a Road Home: Developing Education for a Pediatric Home-Going VAD Program

The objective was to create a multidisciplinary education plan for discharge home following implantation of a ventricular assist device (VAD) in pediatrics. Educational program was developed for the local community: emergency department, emergency medical services, medical transport team, as well as, the pediatric patient and their caregivers. Education geared to the individual learner included both lecture and hands-on training. A direct line for family and local providers to speak directly with a VAD-trained physician 24/7 was also created. Patient and caregivers required to 1) perform 10 supervised power exchanges; 2) qualify written quizzes on the controller, battery charger, alarms, and troubleshooting; 3) perform 10 supervised dressing changes; 4) pass simulation session responding correctly to alarm scenarios; and 5) take both an on-campus and off-campus field trip unaccompanied by support staff. Once the education plan is complete and the patient is medically stable, they are considered ready for discharge. From a mechanical support perspective, discharge home of a medically complex pediatric patient on a durable VAD can be accomplished safely, even in a low volume center, with attention to detail, creation of a robust education plan, and close partnership between the VAD team, the family, and the community.

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.

Destination-Therapy Ventricular Assist Device in Children: "The Future Is Now"

Durable ventricular assist devices (VADs) have significantly improved survival to transplantation among children with advanced stages of heart failure. The fundamental goals of VAD therapy include decreasing mortality, minimizing adverse events, and improving quality of life. As the pediatric VAD experience has evolved with reduced device related complications and improved survival, VAD therapy is being considered not only as a bridge to transplantation (BTT) but also as a bridge to decision (BTD) and as destination therapy (DT). Data regarding pediatric DT VAD are limited to anecdotal or case reports of children being supported for long periods with VADs and by default being classified as DT VAD. This article reviews current trends in the use of DT VAD and adverse events in children vs adults on VAD, and provides a framework for patient selection with the use of a multidisciplinary approach including palliative care. The general approach to determining DT VAD candidacy should include: 1) a reasonable success that the patient will survive the peri- and postoperative state; and 2) a high likelihood that the patient will be able to be discharged out of hospital and have adequate caregiver support. Patients with muscular dystrophy and failing Fontan physiology are examples of pediatric populations for whom DT VAD may be considered and which require unique considerations.

Dilated cardiomyopathy in children: moving beyond traditional pharmacologic therapy

PURPOSE OF REVIEW

Dilated cardiomyopathy (DCM) is a rare myocardial disorder characterized by a dilated left ventricle and systolic dysfunction. Globally, it affects around 1 in every 100 000 children. The prognosis is generally poor, with 40% either failing traditional medical therapy within the first 2 years or requiring a heart transplant. This article will address the basic cause, epidemiology, pathobiology, and historical treatment approach of DCM and introduce novel contemporary medical and surgical strategies that may reduce the need for heart transplantation.

RECENT FINDINGS

In the last 15 years, there has been a significant emphasis on identifying alternative treatment strategies in managing the child with a DCM and heart failure symptoms. New therapies have evolved to help bridge these critically ill children to transplant or have these therapeutic modalities serve as end-points in themselves. Thus subsequently, we will highlight contemporary as well as novel medical and procedural therapies that are being used for the treatment of pediatric DCM.

SUMMARY

The child with a DCM and severe left ventricular dysfunction has a number of options available beyond simple diuretics and afterload reduction. Novel pacing strategies and mechanical assist device may provide not only a more stable clinical bridge environment but also may actually serve as an endpoint itself.

A Quality Bundle to Support High-Risk Pediatric Ventricular Assist Device Implantation

Pediatric ventricular assist device (VAD) implantation outcomes are increasingly promising for children with dilated cardiomyopathy and advanced decompensated heart failure (ADHF). VAD placement in patients with clinical features such as complex congenital cardiac anatomy, small body size, or major comorbidities remains problematic. These comorbidities have been traditionally prohibitive for VAD consideration leaving these children as a treatment-orphaned population. Here we describe the quality bundle surrounding these patients with ADHF considered high risk for VAD implantation at our institution. Over a 7-year period, a quality bundle aimed at the peri-operative care for children with high-risk features undergoing VAD implantation was incrementally implemented at a tertiary children's hospital. Patients were considered high risk if they were neonates (< 30 days), had single-ventricle physiology, non-dilated cardiomyopathy, biventricular dysfunction, or significant comorbidities. The quality improvement bundle evolved to include (1) structured team-based peri-operative evaluation, (2) weekly VAD rounds addressing post-operative device performance, (3) standardized anticoagulation strategies, and (4) a multidisciplinary system for management challenges. These measures aimed to improve communication, standardize management, allow for ongoing process improvement, and incorporate principles of a high-reliability organization. Between January 2010 and December 2017, 98 patients underwent VAD implantation, 48 (49%) of which had high-risk comorbidities and a resultant cohort survival-to-transplant rate of 65%. We report on the evolution of a quality improvement program to expand the scope of VAD implantation to patients with high-risk clinical profiles. This quality bundle can serve as a template for future large-scale collaborations to improve outcomes in these treatment-orphaned subgroups.

Characteristics and Outcomes of Pediatric Patients Supported With Ventricular Assist Device-A Multi-Institutional Analysis

OBJECTIVES

The use of ventricular assist devices for pediatric patients with heart failure is increasing, but is associated with significant morbidity and mortality. Our objectives were to describe the admission outcomes and resource utilization of pediatric patients supported with ventricular assist devices, utilizing a multicenter database.

DATA SOURCES

Pediatric Health Information System database (comprising 49 nonprofit children's hospitals).

STUDY SELECTION

Retrospective cohort analysis of the database from January 2006 to September 2015 for all admissions less than or equal to 21 years old with ventricular assist device implantation.

DATA EXTRACTION

The primary outcome was hospital mortality. The secondary outcomes were hospital length of stay and adjusted cost.

DATA SYNTHESIS

We analyzed 744 ventricular assist device implantations (740 patients), 422 (57%) males, and 363 (49%) non-Hispanic white. Median age at admission was 5.9 years (interquartile range, 0.9-13.5 yr), and median length of stay was 69 days (interquartile range, 36-122 d). The overall hospital mortality was 188 (25%), whereas 395 (53%) were transplanted and 141 (19%) were discharged on ventricular assist device. Extracorporeal membrane oxygenation was used, in addition to ventricular assist device, in 340 (46%). The majority of ventricular assist device implantations (453, 61%) were from 2011 to 2015 (compared to 2006-2010). More patients discharged on ventricular assist device from 2011 to 2015 (23% vs 13% in 2006-2010; p = 0.001). There was no difference in median age, mortality, length of stay, or adjusted costs between these time periods. On multivariable analysis, underlying congenital heart disease, renal failure, liver congestion, sepsis, cerebrovascular accident, and extracorporeal membrane oxygenation were associated with hospital mortality. Sepsis and ventricular assist device replacement/repair were associated with higher adjusted cost and longer length of stay.

CONCLUSIONS

The pediatric ventricular assist device experience continues to grow, with a significant increase in the number of patients undergoing ventricular assist device implantation and a higher proportion being discharged from hospital on ventricular assist device support in recent years. Underlying congenital heart disease, renal failure, sepsis, cerebrovascular accident, and extracorporeal membrane oxygenation are significantly associated with hospital mortality.

An introduction to point-of-care testing in extracorporeal circulation and LVADs

There is a delicate balance between bleeding and clotting in patients on circuits such as ventricular assist devices or extracorporeal membrane oxygenation. Traditional coagulation tests, prothrombin time, activated partial thromboplastin time, and anti-factor Xa levels, are used to monitor patients on these devices. However, turnaround times and inability to assess global hemostasis, including platelets and fibrinogen have contributed to a recognition that faster, accurate, and more informative coagulation tests are needed. Activated clotting time is used to monitor heparin in patients on circuits and has the advantages of being a near-patient point-of-care test. However, its utility is limited to heparin monitoring. Viscoelastic tests (thromboelastometry and thromboelastography) are global, whole-blood coagulation tests, and whole-blood platelet aggregometry evaluates platelet function. Ideally, these tests can ensure that patients are within the therapeutic range of their antithrombotic medications, identify patients at risk for hemorrhagic or thrombotic complications, and guide management of acute bleeding complications. This ideal is currently hampered by a lack of studies that delineate clear ranges that are clinically relevant. Future research is needed to better understand the optimal use of point-of-care coagulation testing in patients on extracorporeal circuits and ventricular assist devices.

Is the New Infant Jarvik 2015 Suitable for Patients<8 kg? In Vitro Study Using a Hybrid Simulator

Our aim was to study the feasibility of implanting the Infant Jarvik 2015 in patients weighing less than 8 kg. The Infant Jarvik 2015 left ventricular assist device (LVAD) was tested in a hybrid simulator of the cardiovascular system reproducing specific patients' hemodynamics for different patient weights (2-7 kg). For each weight, the sensitivity of the pump to different circulatory parameters (peripheral resistance, left ventricular elastance, right ventricular elastance, heart rate, and heart filling characteristics) has been tested repeating for each experiment a pump ramp (10 000-18 000 rpm). The increase in the pump speed causes a decrease (increase) in the left (right) atrial pressure, an increase (decrease) in the arterial systemic (pulmonary) pressure, an increase in the right ventricular pressure, a decrease (increase) in the left (right) ventricular volume, a decrease in the left ventricular cardiac output, an increase in the LVAD output and an increase in the right ventricular cardiac output (total cardiac output). Suction was observed for lower weight patients and for higher pump speed in the case of vasodilation, left ventricular recovery, bradycardia, right ventricular failure, and left ventricular hypertrophy. Backflow was observed in the case of left ventricular recovery at lower pump speed. In the hybrid simulator, the Infant Jarvik 2015 could be suitable for the implantation in patients lower than 8 kg because of the stability of the device respect to the cardio/circulatory changes (low frequency of suction and backflow) and because of the capability of the device to maintain adequate patient hemodynamics.

Home Is Where the HeartWare Is: Preparing Pediatric Patients and Caregivers for Discharge to Home and Integration Into the Community

The Cardiac Center at The Children's Hospital of Philadelphia has cared for patients with implanted ventricular assist device (VAD) technology since 1998. Historically, patients requiring VAD support were managed exclusively in the Cardiac Intensive Care Unit with the first medically stable transition to the Cardiac Care Unit (step-down) taking place in 2001. Patient management was confined to the inpatient setting, as the primary device used at the time was paracorporeal and not suitable for home use. Continuous-flow devices, such as the HeartWare HVAD, have gained popularity because of miniaturized size and lower profiles of side effects and adverse events, making them more suitable for home use. This article describes a single-center experience with transitioning the VAD-supported pediatric patient to the outpatient setting, highlighting outcomes, strategies, and lessons learned in order to support VAD patients and their caregivers in the hospital and community setting.

Recommendations on the Indications for RBC Transfusion for the Critically Ill Child Receiving Support From Extracorporeal Membrane Oxygenation, Ventricular Assist, and Renal Replacement Therapy Devices From the Pediatric Critical Care Transfusion and Anemia Expertise Initiative

OBJECTIVES

To present recommendations and supporting literature for RBC transfusions in critically ill children supported with extracorporeal membrane oxygenation, ventricular assist devices, or renal replacement therapy.

DESIGN

Consensus conference series of international, multidisciplinary experts in RBC transfusion management of critically ill children.

METHODS

The panel of 38 experts developed evidence-based, and when evidence was lacking, expert-based clinical recommendations as well as research priorities for RBC transfusions in critically ill children. The extracorporeal membrane oxygenation/ventricular assist device/renal replacement therapy subgroup included six experts. We conducted electronic searches of the PubMed, EMBASE, and Cochrane Library databases from 1980 to May 2017, using medical subject heading terms and text words to define concepts of RBC transfusion, extracorporeal membrane oxygenation, ventricular assist device, and renal replacement therapy. We used a standardized data extraction form to construct evidence tables and graded the evidence using the Grading of Recommendations Assessment, Development, and Evaluation system. Recommendations developed and supporting literature were reviewed and scored by all panel members. Agreement was obtained using the Research and Development/UCLA Appropriateness Method.

RESULTS

For inpatients requiring extracorporeal membrane oxygenation, ventricular assist device, or renal replacement therapy support, there was expert agreement (> 80%) on five good practice statements aimed to improve accuracy and uniform reporting of RBC transfusion data in pediatric extracorporeal membrane oxygenation, ventricular assist device, and renal replacement therapy studies and quality improvement projects; four clinical recommendations of physiologic metrics and biomarkers of oxygen delivery, in addition to hemoglobin concentration, to guide RBC transfusion, acknowledging insufficient evidence to recommend specific RBC transfusion strategies; and eight research recommendations.

CONCLUSIONS

Further research surrounding indications, risks, benefits, and alternatives to RBC transfusion in children on extracorporeal devices is clearly needed. Using a structured literature review and grading process, the Transfusion and Anemia Expertise Initiative panel concluded that there is currently insufficient evidence to recommend specific RBC transfusion variables in children requiring extracorporeal membrane oxygenation, ventricular assist device, or renal replacement therapy support.