Current Status of Pediatric Ventricular Assist Device Support

Advances in understanding and managing pediatric heart failure and transplant

PURPOSE OF REVIEW

This article highlights the most recent advances in a review of the current literature in the field of pediatric heart failure and transplantation.

RECENT FINDINGS

Diagnostically, the identification of new genetic factors has contributed to a deeper understanding of cardiomyopathy in children. Novel medications like sacubitril/valsartan and Sodium-Glucose cotransporter-2 (SGLT2) inhibitors, which are now standard in the adult population are being studied in pediatric population and offer new promise of pediatric heart failure treatment. Ventricular assist devices are more commonly used in cardiomyopathy patients and single ventricle patients as a bridge to transplant. Recent pediatric heart transplant society (PHTS) data demonstrated that waitlist survival improved significantly over the past decades (i) and new treatments such as daratumumab and eculizumab have been used in high-risk populations and demonstrate promising results. TEAMMATE trial is the first multicenter randomized clinical trial (RCT) in pediatric heart transplant (HT) to evaluate the safety and efficacy of everolimus (EVL) and low-dose tacrolimus (TAC) compared to standard-dose TAC and mycophenolate mofetil (MMF). It will provide valuable information about the safety and efficacy of EVL, TAC, and MMF (ii).Donor cell-free DNA has been used more in pediatric transplant recipients and has significantly decreased invasive EMB (iii).

SUMMARY

This past 5 years have witness dramatic progress in the field of pediatric heart failure and transplantation including more use of mechanical support in heart failure patients with various underlying etiology, especially use of mechanical support in single ventricle patients and the use of sacubitril/valsartan and SGLT2 inhibitors in the pediatric population. The problem of the highly sensitized transplant recipient remains, although novel therapeutics have been added to our toolbox of options to maintain healthy allograft function. Ongoing research aims to further enhance our understanding and management of pediatric heart failure, emphasizing the need for continued innovation in this complex field.

A Review of Pediatric Cardiomyopathy

Though pediatric cardiomyopathy is rare in children, there is significant associated morbidity and mortality. Etiology varies from inborn errors of metabolism to familial genetic mutations and myocyte injury. Major classes include dilated, hypertrophic, restrictive, and non-compaction. Diagnosis generally involves a combination of clinical history and echocardiography. The use of cross-sectional imaging is gaining popularity. Management varies between subtype and may involve a combination of medical and surgical interventions depending on clinical status.

Intracorporeal LVAD implantation in pediatric patients: A single-center 10 years' experience

BACKGROUND

Mechanical cardiac support is currently an effective strategy to reduce morbidity and mortality in pediatric patients. However, solid evidence regarding the feasibility of intracorporeal devices in children still needs to be provided. We report our 10-year experience with intracorporeal left ventricular assist devices (LVAD) in children.

MATERIALS AND METHODS

We included all patients undergoing intracorporeal, continuous-flow LVAD implantation between 2012 and 2022. Baseline and postoperative data were collected from the institutional database.

RESULTS

Seven HeartWare and 4 HeartMate3 were implanted in 11 patients (median age 13.9 years, median body surface area - BSA - 1.42 m2, IQR 1.06-1.68). The most frequent indication to LVAD implant was dilated cardiomyopathy (72.7%). All candidates underwent a thorough preoperative advanced imaging. Three-dimensional reconstructions and implant fit simulation were performed when BSA was <1.2 m2, weight <30 kg, or internal transverse thoracic diameter <20 cm. There was no operative death. The most common postoperative complication was surgical re-exploration due to bleeding (27.3%). One patient died of severe neurological complications after about 3 months of hospitalization. No late deaths or unplanned re-hospitalizations occurred in the remaining 10, 6 of whom were discharged home. There were no major complications at the follow-up. All survivors underwent successful heart transplantation.

CONCLUSIONS

Intracorporeal LVAD implantation proved to be a potentially feasible and safe option in young teenagers and children whose BSA was >1.0 m2. In borderline cases, the 3D reconstruction with implant fit simulation can effectively help to identify those patients who can safely undergo intrathoracic LVAD implantation.

In vitro hemodynamic performance of a blood pump for self-powered venous assist in univentricular hearts

Univentricular heart anomalies represent a group of severe congenital heart defects necessitating early surgical intervention in infancy. The Fontan procedure, the final stage of single-ventricle palliation, establishes a serial connection between systemic and pulmonary circulation by channeling venous return to the lungs. The absence of the subpulmonary ventricle in this peculiar circulation progressively eventuates in failure, primarily due to chronic elevation in inferior vena cava (IVC) pressure. This study experimentally validates the effectiveness of an intracorporeally-powered venous ejector pump (VEP) in reducing IVC pressure in Fontan patients. The VEP exploits a fraction of aortic flow to create a jet-venturi effect for the IVC, negating the external power requirement and driveline infections. An invitro Fontan mock-up circulation loop is developed and the impact of VEP design parameters and physiological conditions is assessed using both idealized and patient-specific total cavopulmonary connection (TCPC) phantoms. The VEP performance in reducing IVC pressure exhibited an inverse relationship with the cardiac output and extra-cardiac conduit (ECC) size and a proportional relationship with the transpulmonary pressure gradient (TPG) and mean arterial pressure (MAP). The ideal VEP with fail-safe features provided an IVC pressure drop of 1.82 ± 0.49, 2.45 ± 0.54, and 3.12 ± 0.43 mm Hg for TPG values of 6, 8, and 10 mm Hg, respectively, averaged over all ECC sizes and cardiac outputs. Furthermore, the arterial oxygen saturation was consistently maintained above 85% during full-assist mode. These results emphasize the potential utility of the VEP to mitigate elevated venous pressure in Fontan patients.

End-of-Life in Pediatric Patients Supported by Ventricular Assist Devices: A Network Database Cohort Study

OBJECTIVES

Most pediatric patients on ventricular assist device (VAD) survive to transplantation. Approximately 15% will die on VAD support, and the circumstances at the end-of-life are not well understood. We, therefore, sought to characterize patient location and invasive interventions used at the time of death.

DESIGN

Retrospective database study of a cohort meeting inclusion criteria.

SETTING

Thirty-six centers participating in the Advanced Cardiac Therapies Improving Outcomes Network (ACTION) Registry.

PATIENTS

Children who died on VAD therapy in the period March 2012 to September 2021.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of the 117 of 721 patients (16%) who died on VAD, the median (interquartile range) age was 5 years (1-16 yr) at 43 days (17-91 d) postimplant. Initial goals of therapy were bridge to consideration for candidacy for transplantation in 60 of 117 (51%), bridge to transplantation in 44 of 117 (38%), bridge to recovery 11 of 117 (9%), or destination therapy (i.e., VAD as the endpoint) in two of 117 (2%). The most common cause of death was multiple organ failure in 35 of 117 (30%), followed by infection in 12 of 117 (10%). Eighty-five of 92 (92%) died with a functioning device in place. Most patients were receiving invasive interventions (mechanical ventilation, vasoactive infusions, etc.) at the end of life. Twelve patients (10%) died at home.

CONCLUSIONS

One-in-six pediatric VAD patients die while receiving device support, with death occurring soon after implant and usually from noncardiac causes. Aggressive interventions are common at the end-of-life. The ACTION Registry data should inform future practices to promote informed patient/family and clinician decision-making to hopefully reduce suffering at the end-of-life.

Double valve replacement after ventricular assist device implantation in a Fontan patient

Few reports have described the implantation and management of an implantable ventricular assist device in patients with functional uni-ventricular anatomy. We herein report a case who underwent HVAD implantation due to severe cardiac dysfunction and Fontan failure in the remote period following total cavo-pulmonary connection. Double valve replacement was subsequently required one year later due to repeated Fontan failure caused by the progression of aortic and atrioventricular regurgitation. The low-profile and saddle-shaped sewing cuff design of the MITRIS were beneficial for avoiding the HVAD inflow and atrioventricular valve interference in the less-dilated ventricle.

The evolution of long-term pediatric ventricular assistance devices: a critical review

Introduction: The gap between the number of heart failure patients and the number of potential heart donors has never been larger than today, especially among the pediatric population. The use of mechanical circulatory support is seen as a potential alternative for clinicians to treat more patients. This treatment has proven its efficiency on short-term use. However, in order to replace heart transplant, the techniques should be used over longer periods of time.Areas covered: This review aims at furnishing an engineering vision of the evolution of ventricular assistance devices used in pediatrics. A critical analysis of the clinical complications related to devices generation is made to give an overview of the design improvements made since their inception.Expert opinion: The long-term use of a foreign device in the body is not without consequences, especially among fragile pediatric patients. Moreover, the size of their body parts increases the technical difficulties of such procedure. The balance between the living cells of the body is disturbed by the devices, mostly by the shear stress generated. To provide a safe mechanical circulatory support for long-term use, the devices should be more hemocompatible, preserving blood cells, adapted to the patient's systemic grid and miniaturized for pediatric use.

A Cavopulmonary Assist Device for Long-Term Therapy of Fontan Patients

Treatment of univentricular hearts remains restricted to palliative surgical corrections (Fontan pathway). The established Fontan circulation lacks a subpulmonary pressure source and is commonly accompanied by progressively declining hemodynamics. A novel cavopulmonary assist device (CPAD) may hold the potential for improved therapeutic management of Fontan patients by chronic restoration of biventricular equivalency. This study aimed at translating clinical objectives toward a functional CPAD with preclinical proof regarding hydraulic performance, hemocompatibility and electric power consumption. A prototype composed of hemocompatible titanium components, ceramic bearings, electric motors, and corresponding drive unit was manufactured for preclinical benchtop analysis: hydraulic performance in general and hemocompatibility characteristics in particular were analyzed in-silico (computational fluid dynamics) and validated in-vitro. The CPAD's power consumption was recorded across the entire operational range. The CPAD delivered pressure step-ups across a comprehensive operational range (0-10 L/min, 0-50 mm Hg) with electric power consumption below 1.5 W within the main operating range. In-vitro hemolysis experiments (N = 3) indicated a normalized index of hemolysis of 3.8 ± 1.6 mg/100 L during design point operation (2500 rpm, 4 L/min). Preclinical investigations revealed the CPAD's potential for low traumatic and thrombogenic support of a heterogeneous Fontan population (pediatric and adult) with potentially accompanying secondary disorders (e.g., elevated pulmonary vascular resistance or systemic ventricular insufficiency) at distinct physical activities. The low power consumption implied adequate settings for a small, fully implantable system with transcutaneous energy transfer. The successful preclinical proof provides the rationale for acute and chronic in-vivo trials aiming at the confirmation of laboratory findings and verification of hemodynamic benefit.

Cardiac Emergencies in Kids

Encountering a child with congenital heart disease after surgical palliation in the emergency department, specifically the single-ventricle or ventricular assist device, without a basic familiarity of these surgeries can be extremely anxiety provoking. Knowing what common conditions or complications may cause these children to visit the emergency department and how to stabilize will improve the chance for survival and is the premise for this article, regardless of practice setting.

Pediatric ventricular assist device registries: update and perspectives in the era of miniaturized continuous-flow pumps

The success of ventricular assist devices (VADs) in the treatment of end-stage heart failure in the adult population has led to industrial innovation in VAD design, focusing on miniaturization and the reduction of complications. A byproduct of these innovations was that newer generation devices could have clinical applications in the pediatric population. Over the last decade, VAD usage in the pediatric population has increased dramatically, and the newer generation continuous flow (CF) devices have begun to supplant the older, pulsatile flow (PF) devices, formerly the sole option for ventricular assist in the pediatric population. However, despite the increase in VAD implants in the pediatric population, patient numbers remain low, and the need to share data between pediatric VAD centers has become that much more important for the continued growth of VAD programs worldwide. The creation of pediatric VAD registries, such as the Pediatric Registry for Mechanical Circulatory Support (PediMACS), the European Registry for Patients with Mechanical Circulatory Support (EUROMACS) and the Advanced Cardiac Therapies Improving Outcomes Network (ACTION) has enabled the collection of aggregate data from VAD centers worldwide, and provides a valuable resource for clinicians and programs, as more and more pediatric heart failure patients are considered candidates for VAD therapy.

Technical modifications for transplant in the failing Fontan

INTRODUCTION

Heart transplant after Fontan completion poses a unique surgical challenge. Twenty patients are presented, stressing the technical hints performed in the five anastomoses to match the graft in the recipient.

METHODS

Data are collected from 20 Fontan patients between 2013 and 2019. Age (13 years), weight (37 kg.), and time interval between Fontan and transplant (7 years) are presented as median. Extracardiac conduit (size 18/20) was implanted in 15 patients, whereas atrio-pulmonary connection was performed in 4 and lateral tunnel in 1. Six patients developed protein-losing enteropathy. Seventeen stents had been previously deployed.

RESULTS

The five anastomoses underwent some changes. Left atrium once, aorta 9 times, superior vena cava 7 times, pulmonary branches 15 times, and inferior vena cava 12 times. Follow-up was complete for a median of 42 months (range 6-84). Two patients died. ECMO was needed in six cases for pulmonary hypertension. Four patients had collateral vessels occluded in the cath lab, and stents were placed in superior vena cava (1) and aorta (1) post-transplant. Protein-losing enteropathy was resolved in five patients. Interestingly, one patient was on a systemic assist device before transplant (Levitronix) and right assistance (ECMO) afterwards.

CONCLUSIONS

Transplant in Fontan patients is actually challenging. Hints in every of the five proposed anastomoses must be anticipated, including stents removal. Extra tissue from the donor (innominate vein, aortic arch, and pericardium) is strongly advisable. ECMO for right ventricular dysfunction was needed in nearly one-third of the cases. Overall results can match other transplant cohorts.

"Compassionate" Cases of the Jarvik 2015 Ventricular Assist Device

The Jarvik 2015 Ventricular Assist Device (VAD) (Jarvik Inc, New York, NY) is the first and currently only continuous-flow VAD specifically designed for small children, and it is being evaluated in the so-called Pump for Kids, Infants, and Neonates (PumpKIN) trial. Due to the strict inclusion criteria of the trial, there have been a group of patients who failed to meet the criteria and therefore received the Jarvik 2015 VAD under the designation of "compassionate use." This is the same phenomenon seen previously during the Berlin Heart EXCOR trial. While we await the results of the PumpKIN trial, which will report the device performance in a strictly selected population, the compassionate use cases represent actual "real world" experiences. We describe herein our experience of two compassionate use cases. In particular, this report has a special emphasis on the power consumption and hemolysis and inflammatory lab profile of the Jarvik 2015 VAD as hemocompatibility was the primary focus of the developmental and the preclinical phases.

Caregiver experiences of paediatric inpatient cardiac services: A qualitative systematic review

BACKGROUND

Advances in paediatric care have contributed to an increasing survival of children with complex heart disease. Yet, life-saving management demands prolonged inpatient admissions, which contribute to emotional and psychological distress for parents and other caregivers in a role of main custody.

AIM

The purpose of this study was to identify, appraise and synthesise qualitative studies exploring caregivers' experiences of paediatric inpatient cardiac services, generating an understanding of their needs in hospital and informing priorities for change in healthcare delivery.

METHODS

Searches were conducted in Medline, Allied and Complimentary Medicine Database, Cumulative Index of Nursing and Allied Health Literature, EMCARE, Scopus, PsychINFO, Proquest, OpenGrey and ETHOs from 2008-2019, reflecting recent advances in cardiac healthcare. Articles were selected using predetermined eligibility criteria dictating qualitative inquiry into caregiver perspectives whilst their child received hospital-based interventions for heart disease. All eligible studies underwent quality appraisal. Framework synthesis was used to analyse and summarise findings.

RESULTS

Twenty-seven studies involving 689 caregivers from 11 countries were included. Three overarching themes were identified: 'emotional capacity to care', 'practicalities of caring', and 'the bigger picture of caring'.

CONCLUSIONS

Through analysis and summary of qualitative primary research, this review captures the emotional challenges that caregivers face and practicalities of undertaking a caregiver role, whilst looking after their child with heart disease in hospital. The results widen the context of the caregiver role, encompassing the whole family unit beyond the hospital environment. This review exposes the impact of these challenges on caregiver competence, wellbeing and attachment to their unwell child, informing priorities for development of family-centred paediatric inpatient cardiac services.

The failing Fontan

Nearly 50 years back, Francis Fontan pioneered an operation for tricuspid atresia that bears his name today. The operation has since undergone numerous modifications and continues to be widely applied to an array of single ventricles. Despite restoring normal oxygen levels in the body, the operation creates a neoportal system where adequate cardiac output can be generated only at the expense of increased systemic venous congestion. This results in slow but relentless damage to the end organ systems especially the liver. Continuous surveillance of the patient to monitor this circulation, that will ultimately fail, is of paramount importance. Timely medical and cardiac catheterization and surgical intervention can extend the life span of Fontan patients. Ultimately a change of the hemodynamic circuit in the form of heart transplantation or ventricular assist device will be required to salvage the failing Fontan circuit.

Magnetic Resonance Imaging Based Flow Field and Lagrangian Particle Tracking From a Left Ventricular Assist Device

This study explores the optimal left ventricular assist device (LVAD) cannula outflow configuration in a patient-specific replica of the aorta. The volumetric velocity field is measured using phase-contrast magnetic resonance imaging (PC-MRI) under a physiologically relevant steady flow. The effect of the LVAD outflow graft insertion site and anastomosis angle on the transport of embolic particles to cranial vessels is studied by solving the particle equation of motion for spheres in the range of 0.1-1.0 mm using the measured three-dimensional (3D) velocity field. Results show that for a given aorta anatomy, it is possible to design the cannula graft location and terminal curvature so that the probability of embolic transport to the cranial vessels is significantly minimized. This is particularly important since the complex flow pattern in each cannula case affects the embolic trajectories differently, and hence the common assumption that particles distribute by the volumetric flow division does not hold.

Cavopulmonary assist: Long-term reversal of the Fontan paradox

OBJECTIVE

Fontan circulatory inefficiency can be addressed by replacing the missing subpulmonary power source to reverse the Fontan paradox. An implantable cavopulmonary assist device is described that will simultaneously reduce systemic venous pressure and increase pulmonary arterial pressure, improving preload and cardiac output, in a univentricular Fontan circulation on a long-term basis.

METHODS

A rotary blood pump that was based on the von Karman viscous pump was designed for implantation into the total cavopulmonary connection (TCPC). It will impart modest pressure energy to augment Fontan flow without risk of obstruction. In the event of rotational failure, it is designed to default to a passive flow diverter. Pressure-flow performance was characterized in vitro in a Fontan mock circulatory loop with blood analog.

RESULTS

The pump performed through the fully specified operating range, augmenting flow in all 4 directions of the TCPC. Pressure rise of 6 to 8 mm Hg was readily achieved, ranging to 14 mm Hg at highest speed (5600 rpm). Performance was consistent across a wide range of cardiac outputs. In stalled condition (0 rpm), there was no discernible pressure loss across the TCPC.

CONCLUSIONS

A blood pump technology is described that can reverse the Fontan paradox and may permit a surgical strategy of long-term biventricular maintenance of a univentricular Fontan circulation. The technology is intended for Fontan failure in which right-sided circulatory inefficiencies predominate and ventricular systolic function is preserved. It may also apply before clinical Fontan failure as health maintenance to preempt the progression of Fontan disease.

Evaluation and Management of the Child and Adult With Fontan Circulation: A Scientific Statement From the American Heart Association

It has been 50 years since Francis Fontan pioneered the operation that today bears his name. Initially designed for patients with tricuspid atresia, this procedure is now offered for a vast array of congenital cardiac lesions when a circulation with 2 ventricles cannot be achieved. As a result of technical advances and improvements in patient selection and perioperative management, survival has steadily increased, and it is estimated that patients operated on today may hope for a 30-year survival of >80%. Up to 70 000 patients may be alive worldwide today with Fontan circulation, and this population is expected to double in the next 20 years. In the absence of a subpulmonary ventricle, Fontan circulation is characterized by chronically elevated systemic venous pressures and decreased cardiac output. The addition of this acquired abnormal circulation to innate abnormalities associated with single-ventricle congenital heart disease exposes these patients to a variety of complications. Circulatory failure, ventricular dysfunction, atrioventricular valve regurgitation, arrhythmia, protein-losing enteropathy, and plastic bronchitis are potential complications of the Fontan circulation. Abnormalities in body composition, bone structure, and growth have been detected. Liver fibrosis and renal dysfunction are common and may progress over time. Cognitive, neuropsychological, and behavioral deficits are highly prevalent. As a testimony to the success of the current strategy of care, the proportion of adults with Fontan circulation is increasing. Healthcare providers are ill-prepared to tackle these challenges, as well as specific needs such as contraception and pregnancy in female patients. The role of therapies such as cardiovascular drugs to prevent and treat complications, heart transplantation, and mechanical circulatory support remains undetermined. There is a clear need for consensus on how best to follow up patients with Fontan circulation and to treat their complications. This American Heart Association statement summarizes the current state of knowledge on the Fontan circulation and its consequences. A proposed surveillance testing toolkit provides recommendations for a range of acceptable approaches to follow-up care for the patient with Fontan circulation. Gaps in knowledge and areas for future focus of investigation are highlighted, with the objective of laying the groundwork for creating a normal quality and duration of life for these unique individuals.

Current status and future perspectives of the PumpKIN trial

Similar to the adult experience, the use of continuous-flow ventricular assist devices (VADs) has been increasing in the pediatric population. According to the PediMACS registry, continuous-flow VAD currently accounts for >60% of the durable device implantations in the U.S. Nonetheless, the continuous-flow VADs currently in use are designed for adults; this inevitably causes the patient-device size mismatch issue, especially when applied for small children. Pulsatile VADs, therefore, represent the only practical option for this group of patients despite the known risk profile of pulsatile VADs. To address such a frustrating reality, the National Heart, Lung, and Blood Institute (NHLBI) launched the Pediatric Circulatory Support Program in 2004, which is the predecessor of the so-called PumpKIN (Pump for Kids, Infants, and Neonates) program. The goal of this program was to develop mechanical circulatory support devices specifically designed for small children. As a result of extensive efforts of the multi-disciplinary team involving clinicians, scientists, manufactures, and federal agencies, the Infant Jarvik 2015, one of the original devices within the Pediatric Circulatory Support Program, has become the first continuous-flow VAD specifically designed for small children that obtained the Investigational Device Exemption (IDEs) from the U.S. Food and Drug Administration (FDA). This approval is a prerequisite to initiate a clinical trial (i.e., the PumpKIN trial). This article describes the history, current status, and future perspectives of this extremely challenging project, with a focus on the lessons we have learned over the decade.