Right ventricular dysfunction in children supported with pulsatile ventricular assist devices

Early Improvement in Clinical Status Following Ventricular Assist Device Implantation in Children: A Marker for Survival

While clinical status at the time of ventricular assist device (VAD) implant can negatively affect outcomes, it is unclear if early improvement after implant can have a positive effect. Therefore, the objectives of this study were to describe the clinical status of pediatric patients supported with a VAD and determine the impact of clinical status on the 1-month follow-up form on survival and ability to discharge. This was a retrospective analysis of data collected prospectively by the Pediatric Interagency Registry for Mechanical Circulatory Support Registry (Pedimacs) Registry. The Pedimacs database was queried for patients implanted between September 19, 2012, and September 30, 2019, who were alive on VAD support at 1-month postimplant on either a paracorporeal pulsatile or intracorporeal continuous device. Four factors on the 1-month follow-up were the focus of this study: mechanical ventilation, supplemental nutritional support, inotropic support, and ambulatory status. These factors were regarded as present if detected between 1-week and 1-month postimplant and were analyzed to determine their impact on survival following 1 month of VAD support and on successful discharge from hospital in patients with implantable continuous-flow devices. The eligible study cohort consisted of 414 patients with a mean age of 9.6 ± 6.2 years, weight of 40.8 ± 32.3 kg with the majority being male (56.7%) and having cardiomyopathy (68%). An isolated left ventricular assist device (LVAD) was the most common implant (85.5%). At implant, 40% were ventilated, 57% required nutritional support, 93% were on inotropes, and 58% were nonambulating. On the 1-month postimplant form, there were significant improvements in all four categories (14% ventilator support, 46% nutritional support, 53% on inotropes, and 25% nonambulating). However, there was no significant early change in the percentage of patients requiring supplemental nutrition in the paracorporeal pulsatile devices (88% vs. 82%; p = 0.2). Presence of these clinical parameters in early follow-up postimplant had a significant negative impact on survival and on the ability of patients with continuous-flow devices to be discharged. Presence of four specific clinical parameters early after VAD placement is associated with worse overall survival and an inability to discharge patients on VAD support. Ongoing work is needed for optimization of patients before implant and aggressive rehabilitation after implant to help improve long-term outcomes.

Pediatric Heart Transplant Recipients Bridged with Biventricular Assist Device Have Worse 1 Year Graft Survival

There are little data on postheart transplant (HT) outcomes for pediatric patients that were supported to HT with biventricular assist device (BiVAD). The United Network for Organ Sharing database was queried for patients <18 years old at time of HT between January 2005 and March 2018, excluding patients bridged with total artificial hearts and right ventricular assist device (VAD). Of 4,904 pediatric HT recipients, patients were grouped by no VAD support (3,934; 80.2%), left ventricular assist device only (736; 15%), and BiVAD (234; 4.8%). Overall graft survival analysis indicates crossing hazard rates between groups over time with the BiVAD group having a significantly lower graft survival at 1 year post-HT. A Cox model adjusted for age, era, diagnosis, and time by group interaction demonstrated increased 1 year hazard ratio (HR) of 8.5 (95% confidence intervals [CI]: 6.15-11.79) comparing BiVAD to no VAD. Comparable hazard between BiVAD and no VAD groups were found at 5 years (HR 1.01; 95% CI: 0.67-1.51), while lower hazard for the BiVAD group was found at 10 years post-HT (HR 0.07; 95% CI: 0.03-0.18). Although pre-HT BiVAD support leads to worse graft survival 1 year post-HT, long-term survival is acceptable.

Right heart failure considerations in pediatric ventricular assist devices

Right heart failure (RHF) is a vexing problem in children after left ventricular assist device (LVAD) implantation that can negatively impact transplant candidacy and survival. Anticipation, prevention, early identification and appropriate medical and device management of RHF are important to successful LVAD outcomes. However, there is limited pediatric evidence to guide practice. This pediatric-focused review summarizes the relevant literature and describes the harmonized approach to RHF from the Advanced Cardiac Therapies Improving Outcomes Network (ACTION). This review seeks to improve RHF outcomes through the sharing of best practices and experience across the pediatric VAD community.

Pediatric Ventricular Assist Device Implantation: An Anesthesia Perspective

Background

Ventricular assist devices (VADs) are increasingly being implanted in children, yet there is little literature to guide anesthetic management for these procedures.

Aims

To describe the pediatric population presenting for VAD implantation and the anesthetic management these patients receive. To compare (a) children under and over 12 months of age and (b) children with and without congenital heart disease.

Methods

Retrospective review of patients aged 0 to 17 years who underwent VAD implantation at a single center between 2014 and 2019.

Results

Seventy-seven VADs were implanted in 68 patients (46 left VADs, 24 biventricular VADs, 6 right VADs, and 1 univentricular VAD). One procedure was abandoned. Preoperatively, 20 (26%) patients were supported with extracorporeal membrane oxygenation and 57 (73%) patients were ventilated. Intraoperative donor blood products were required in 74 (95%) cases. Postimplantation inotropic support was required in 66 (85%) cases overall and 46 (100%) patients receiving a left VAD. Infants under 12 months were more likely to require preoperative extracorporeal membrane oxygenation (42% vs 19%), have femoral venous access (54% vs 28%), receive an intraoperative vasoconstrictor (42% vs 24%), and have delayed sternal closure (63 vs 22%). Mortality was higher in patients under 12 months (25% vs 19%) and in patients with congenital heart disease (25% vs 20%).

Conclusions

Children undergoing VAD implantation require high levels of preoperative organ support, high-dose intraoperative inotropic support, and high-volume blood transfusion. Children under 12 months and those with congenital heart disease are particularly challenging for anesthesiologists and have worse overall outcomes.

Experience with Temporary Centrifugal Pump Bi-ventricular Assist Device for Pediatric Acute Heart Failure: Comparison with ECMO

Though ventricular assist devices (VADs) are an important treatment option for acute heart failure, an extracorporeal membrane oxygenator (ECMO) is usually used in pediatric patients for several reasons. However, a temporary centrifugal pump-based Bi-VAD might have clinical advantages versus ECMO or implantable VADs. From January 2000 to July 2018, we retrospectively reviewed 36 pediatric patients who required mechanical circulatory support (MCS) for acute heart failure. Cases with postoperative MCS were excluded. Since 2016, we have tried to immediately add a right VAD rather than ECMO, when the patients begin to present features of right heart failure after left VAD support started in cases that the patients' respiratory function did not require an oxygenator. Original diagnoses included dilated cardiomyopathy (n = 18), myocarditis (n = 11), and others (n = 7). Eleven patients were supported by Bi-VAD, and 25 patients were supported by ECMO; of these. Four patients were successfully weaned from VAD, and 10 patients were weaned from ECMO. Eleven patients underwent heart transplantation. Overall, we have 15 (41.7%) early mortalities. There were no significant differences in early mortality, morbidity, and weaning rate between the Bi-VAD group and the ECMO group. During the support, patients with Bi-VADs significantly required fewer platelets and showed less hemolysis than ECMO patients. Patients with myocarditis were successfully weaned from Bi-VAD support and bridged to transplantation thereafter. A temporary centrifugal pump-based Bi-VAD was clinically comparable to ECMO for pediatric patients with acceptable pulmonary function.

Pediatric Ventricular Assist Device

There have been great advances in ventricular assist device (VAD) treatment for pediatric patients with advanced heart failure. VAD support provides more time for the patient in the heart transplant waiting list. Augmented cardiac output improves heart failure symptoms, end-organ function, and general condition, and consequently provides beneficial effects on post-transplant outcomes. Miniaturized continuous flow devices are more widely adopted for pediatric patient with promising results. For infants and small children, still paracorporeal pulsatile device is the only option for long-term support. Younger age, congenital heart disease, biventricular support, patient's status and end-organ dysfunction at the time of implantation are risks for poor outcomes. Patient selection, timing of implantation, and selection of device for each patient are critical for optimal clinical outcomes.

Changes in left and right ventricular two-dimensional echocardiographic speckle-tracking indices in pediatric LVAD population: A retrospective clinical study

Echocardiographic strain and strain-rate imaging is a promising tool for the evaluation of myocardial segmental function, for the early detection of myocardial dysfunction, and for the prediction of reverse remodeling. We aimed at studying the changes in left and right ventricular function in pulsatile left ventricular assist device pediatric patients by two-dimensional echocardiography and two-dimensional speckle-tracking echocardiography. Echocardiographic and clinical data of patients implanted with a pulsatile-flow left ventricular assist device from 2011 to 2018 were retrospectively reviewed before and after implantation at 1, 3, and 6 months. A total of 18 patients were enrolled. Median age and weight at implantation were 9 months (5-23 months) and 5.85 kg (4.85-8.75 kg), respectively; median left ventricular assist device support was 181 (114.5-289.5) days. 13 patients (73%) were transplanted and 5 patients (27%) died. At follow-up: left ventricular ejection fraction increase at 1 month (p = 0.001) and 3 months (p = 0.01), left ventricular global longitudinal strain improvement at 1 month (p = 0.0008) and 3 months (p = 0.02), and right ventricular free-wall longitudinal strain increase at 1 month (p = 0.01). At short term after left ventricular assist device implantation, both left ventricular and right ventricular mechanics improved. The temporary benefit seems to decrease over time. The worsening of left ventricular function has been followed by a worsening of right ventricular function probably due to the ventricular interdependence.

Acute and Long-Term Effects of LVAD Support on Right Ventricular Function in Children with Pediatric Pulsatile Ventricular Assist Devices

Right ventricular failure (RVF) is a significant issue when considering left ventricular assist device (LVAD) implantation in pediatrics. The aim of this study was to evaluate the effects of LVAD on right ventricular (RV) function in children. We retrospectively reviewed clinical and echocardiographic data of children who underwent Berlin Heart EXCOR LVAD focusing on RV function before and after implantation (1, 3, and 6 month follow-up). An isolated LVAD was used in 27 patients. Median age was 11 months (interquartile range [IQR]: 5-24 months), with a median weight of 6.3 kg (IQR: 5-9 kg). Median time on ventricular assist device (VAD) support was 147 days (IQR: 86-210 days). Twenty patients were successfully bridged to orthotopic heart transplantation (OHT) (74%), six patients died (22%), and also heart function recovered in one patient (4%). Before LVAD implantation, nine patients (33%) showed a RV fractional area change (RVFAC) less than or equal to 30%. After implantation, mean RVFAC increased up until the 3 month follow-up (43.13%; p = 0.033) and then slightly decreased. In a subgroup of 18 patients, the average strain value increased after the 1 month follow-up (p = 0.022). Right ventricular failure developed in 33% of patients before the 1 month follow-up, and 7.4% experienced RVF at the 6 month follow-up. No patient required biventricular assist device (BiVAD). In our population, pulsatile-flow LVAD in children allows optimal RV decompression and function post-LVAD as measured by improvement in RV function at echo particularly at 1 and 3 month follow-up. At long-term follow-up, the beneficial effects of LVAD on RV function seem to be reduced as signs and symptoms of late RVF may develop in some patients despite LVAD support.

Pulsatile operation of a continuous-flow right ventricular assist device (RVAD) to improve vascular pulsatility

Despite the widespread acceptance of rotary blood pump (RBP) in clinical use over the past decades, the diminished flow pulsatility generated by a fixed speed RBP has been regarded as a potential factor that may lead to adverse events such as vasculature stiffening and hemorrhagic strokes. In this study, we investigate the feasibility of generating physiological pulse pressure in the pulmonary circulation by modulating the speed of a right ventricular assist device (RVAD) in a mock circulation loop. A rectangular pulse profile with predetermined pulse width has been implemented as the pump speed pattern with two different phase shifts (0% and 50%) with respect to the ventricular contraction. In addition, the performance of the speed modulation strategy has been assessed under different cardiovascular states, including variation in ventricular contractility and pulmonary arterial compliance. Our results indicated that the proposed pulse profile with optimised parameters (A_pulse = 10000 rpm and ω_min = 3000 rpm) was able to generate pulmonary arterial pulse pressure within the physiological range (9–15 mmHg) while avoiding undesirable pump backflow under both co- and counter-pulsation modes. As compared to co-pulsation, stroke work was reduced by over 44% under counter-pulsation, suggesting that mechanical workload of the right ventricle can be efficiently mitigated through counter-pulsing the pump speed. Furthermore, our results showed that improved ventricular contractility could potentially lead to higher risk of ventricular suction and pump backflow, while stiffening of the pulmonary artery resulted in increased pulse pressure. In conclusion, the proposed speed modulation strategy produces pulsatile hemodynamics, which is more physiologic than continuous blood flow. The findings also provide valuable insight into the interaction between RVAD speed modulation and the pulmonary circulation under various cardiovascular states.

Evolution of Biventricular Loading Condition in Pediatric LVAD Patient: A Prospective and Observational Study

The aim of this study was to describe the echocardiographic trend of left ventricular (LV) and right ventricular (RV) function after implantation of a pulsatile flow left ventricular assist device (LVAD) in children. From 2013 to 2016, we prospectively evaluated 13 consecutive pediatric Berlin Heart EXCOR LVAD patients. Clinical and echocardiographic data were collected at baseline, within 24 h after implantation and monthly until LVAD explant. Median age and weight at the implantation was 8 (4-23) months and 5 (4.6-8.3) kg at the time of implantation, respectively. All were affected by dilated cardiomyopathy. Average LVAD support time was 226.2 ± 121.2 days. Nine (70%) were transplanted, 4 (30%) died. LV end-systolic and end-diastolic volumes were reduced until the follow up of two months (P = 0.019 and P = 0.001). A progressive increase in RV dimensions was observed. After 4 months of follow up, RV fractional area change worsening was statistically related with the deterioration of LV unloading (P = 0.0036). Four patients needed prolonged inotropic support for RV failure. Pulsatile LVAD in pediatrics is followed by an early and mid-term LV unloading, as expressed by a decrease in LV volumes and diameters at echocardiogram. The effects of unloading do not remain stable at long term follow up. RV function improved in the acute phase, but a progressive dilatation of RV was noted over time. In some patients, RV failure might lead to the need of an increase of inotropic support at long term follow up.

Concomitant Pulsatile and Continuous Flow VAD in Biventricular and Univentricular Physiology: A Comparison Study with a Numerical Model

Introduction

To develop and test a lumped parameter model to simulate and compare the effects of the simultaneous use of continuous flow (CF) and pulsatile flow (PF) ventricular assist devices (VADs) to assist biventricular circulation vs. single ventricle circulation in pediatrics.

Methods

Baseline data of 5 patients with biventricular circulation eligible for LVAD and of 5 patients with Fontan physiology were retrospectively collected and used to simulate patient baselines. Then, for each patient the following simulations were performed: (a) CF VAD to assist the left ventricle (single ventricle) + a PF VAD to assist the right ventricle (cavo-pulmonary connection) (LCF + RPF); (b) PF VAD to assist the left ventricle (single ventricle) + a CF VAD to assist the right ventricle (cavo-pulmonary connection) (RCF + LPF)

Results

In biventricular circulation, the following results were found: cardiac output (17% RCF + LPF, 21% LCF + RPF), artero-ventricular coupling (-36% for the left ventricle and -21.6% for the right ventricle), pulsatility index (+6.4% RCF + LPF, p = 0.02; -8.5% LCF + RPF, p = 0.00009). Right (left) atrial pressure and right (left) ventricular volumes are decreased by the RCF + LPF (by RPF + LCF). Pulmonary arterial pressure decreases in the LCF + RPF configuration. In Fontan physiology: cardiac output (LCF + RPF 35% vs. 8% in RCF + LPF), ventricular preload (+4% RCF + LPF, -10% LCF + RPF), Fontan conduit pressure (-5% RCF + LPF, +7% LCF + RPF), artero-ventricular coupling (-14% RCF + LPF vs. -41% LCF + RPF) and pulsatility (+13% RCF + LPF, - 8% LCF + RPF).

Conclusions

A numerical model supports clinicians in defining and innovating the VAD implantation strategy to maximize the hemodynamic benefits. Results suggest that the hemodynamic benefits are maximized by the LCF + RPF configuration.

Application of a Lumped Parameter Model to Study the Feasibility of Simultaneous Implantation of a Continuous Flow Ventricular Assist Device (VAD) and a Pulsatile Flow VAD in BIVAD Patients

The aim of this work is to develop and test a lumped parameter model of the cardiovascular system to simulate the simultaneous use of pulsatile (P) and continuous flow (C) ventricular assist devices (VADs) on the same patient. Echocardiographic and hemodynamic data of five pediatric patients undergoing VAD implantation were retrospectively collected and used to simulate the patients' baseline condition with the numerical model. Once the baseline hemodynamic was reproduced for each patient, the following assistance modalities were simulated: (a) CVAD assisting the right ventricle and PVAD assisting the left ventricle (RCF + LPF), (b) CVAD assisting the left ventricle and PVAD assisting the right ventricle (LCF + RPF). The numerical model can well reproduce patients' baseline. The cardiac output increases in both assisted configurations (RCF + LPF: +17%, LCF + RPF: +21%, P = ns), left (right) ventricular volumes decrease more evidently in the configuration LCF + RPF (RCF + LPF), left (right) atrial pressure decreases in the LCF + RPF (RCF + LPF) modality. The pulmonary arterial pressure slightly decreases in the configuration LCF + RPF and it increases with RCF + LPF. Left and right ventricular external work increases in both configurations probably because of the total cardiac output increment. However, left and right artero-ventricular coupling improves especially in the LCF + RPF (-36% for the left ventricle and -21% for the right ventricle, P = ns). The pulsatility index decreases by 8.5% in the configuration LCF + RPF and increases by 6.4% with RCF + LPF (P = 0.0001). A numerical model could be useful to tailor on patients the choice of the VAD that could be implanted to improve the hemodynamic benefits. Moreover, a model could permit to simulate extreme physiological conditions and innovative configurations, as the implantation of both CVAD and PVAD on the same patient.

The Use of Berlin Heart EXCOR VAD in Children Less than 10 kg: A Single Center Experience

Objective: Despite the improvement in ventricular assist device (VAD) therapy in adults and in adolescents, in infant population only Berlin Heart EXCOR (BHE) is licensed as long term VAD to bridge children to Heart Transplantation (HTx). Particularly demanding in terms of morbidity and mortality are smallest patients namely the ones implanted in the first year of life or with a lower body surface area. This work aims at retrospective reviewing a single center experience in using BHE in children with a body weight under 10 kg.

Methods: Data of all pediatric patients under 10 kg undergoing BHE implantation in our institution from March 2002 to March 2016 were retrospectively reviewed.

Results: Of the 30 patients enrolled in the study, 53% were male, 87% were affected by a dilated cardiomyopathy with an average weight and age at the implantation of 6.75 ± 2.16 Kg and 11.57 ± 10.12 months, respectively. Three patients (10%) required a BIVAD implantation. After the implantation, 7 patients (23%) required re-intervention for bleeding and 9 patients (30%) experienced BHE cannulas infection. A total of 56 BHE pump were changed for thrombus formation (1.86 BHE pump for patient). The average duration of VAD support was 132.8 ± 94.4 days. Twenty patients (67%) were successfully transplanted and 10 patients (33%) died: 7 for major neurological complication and 3 for sepsis.

Conclusion: Mechanical support in smaller children with end stage heart failure is an effective strategy for bridging patients to HTx. The need for BIVAD was relegated, in the last years, only to restrictive cardiomiopathy. Further efforts are required in small infants to improve anticoagulation strategy to reduce neurological events and BHE pump changes.

Early Biventricular Assist Device Use in Children: A Single-Center Review of 31 Patients

Biventricular assist device (BiVAD) support is considered a risk factor for worse outcomes compared with left ventricular assist device (LVAD) alone for children with end-stage heart failure. It remains unclear whether this is because of the morbidity associated with a second device or the underlying disease severity. We aimed to show that early BiVAD support can result in good survival by analyzing our prospectively collected database for all pediatric patients who underwent BiVAD implantation. From 2005 to 2009, BiVADs were used exclusively. From 2010 to 2014, LVAD alone was considered, maintaining a low threshold for BiVAD support. All BiVADs were pulsatile devices. Thirty-one patients with median age of 3.5 years received BiVAD support. Diagnoses included dilated cardiomyopathy in 17 (55%), myocarditis in 6 (19%), and congenital heart disease in 3 (10%). Survival to transplant was achieved in 27 (87%) with a median duration of 41 days (interquartile range, 15-69). Adverse event rates (per 100 days of support) were bleeding at 0.52, infection at 1.17, and central nervous system dysfunction at 0.78. Of those who survived to transplant, 26 (96%) remain alive with a median follow-up of 55 months. These results show that BiVAD support can bridge patients to transplant with excellent long-term survival.

Simulation of Acute Haemodynamic Outcomes of the Surgical Strategies for the Right Ventricular Failure Treatment in Pediatric LVAD

Background

Right ventricular failure (RVF) is one of the major complications during LVAD. Apart from drug therapy, the most reliable option is the implantation of RVAD. However, BIVAD have a poor prognosis and increased complications. Experiments have been conducted on alternative approaches, such as the creation of an atrial septal defect (ASD), a cavo-aortic shunt (CAS) including the LVAD and a cavo-pulmonary connection (CPC). This work aims at realizing a lumped parameter model (LPM) to compare the acute hemodynamic effects of ASD, CPC, CAS, RVAD in LVAD pediatric patients with RVF.

Methods

Data of 5 pediatric patients undergoing LVAD were retrospectively collected to reproduce patients baseline hemodynamics with the LPM. The effects of continuous flow LVAD implantation complicated by RVF was simulated and then the effects of ASD, CPC, CAS and RVAD treatments were simulated for each patient.

Results

The model successfully reproduced patients' baseline and the hemodynamic effects of the surgical strategies. Simulating the different surgical strategies, an unloading of the right ventricle and an increment of left ventricular preload were observed with an improvement of the hemodynamics (total cardiac output: ASD +15%, CPC +10%, CAS +70% RVAD +20%; right ventricular external work: ASD -19%, CPC -46%, CAS -76%, RVAD -32%; left ventricular external work: ASD +12%, CPC +28%, RVAD +64%).

Conclusions

The use of numerical model could offer an additional support for clinical decision-making, also potentially reducing animal experiments, to compare the outcome of different surgical strategies to treat RVF in LVAD.

Multi-objective optimization of pulsatile ventricular assist device hemocompatibility based on neural networks and a genetic algorithm

PURPOSE

Given the benefit of pulsatile blood flow for perfusion of coronary arteries and end organs, pulsatile ventricular assist devices (VADs) are still widely used as paracorporeal mechanical circulatory support devices in clinical applications. However, poor hemocompatibility limits the service period of the VADs. Most previous improvements on VAD hemocompatibility were conducted by trial-and-error CFD analysis, which does not easily arrive at the best solution.

METHODS

In this paper, a multi-objective optimization method integrating neural networks and NSGA-II (Non-dominated Sorted Genetic Algorithm-II) based on FSI simulation was developed and applied to a pulsatile VAD to optimize its hemocompatibility. First, the VAD blood chamber was parameterized with the principal geometrical parameters. Three hemocompatibility indices including hemolysis, platelet activation, and platelet deposition were chosen as goal functions. The neural networks were built to fit the nonlinear relationship between goal functions and geometrical parameters. Next, a multi-objective optimization algorithm (NSGA-II) was used to search out the Pareto optimal solutions in the built neural networks. Finally, the best compromise solution was selected from the Pareto optimal solutions by a fuzzy membership approach and validated by FSI simulation.

RESULTS

The best compromise solution simultaneously possesses an acceptable hemolysis index, platelet activation index, and platelet deposition index, and the corresponding relative errors between the indices predicted by optimization algorithm and the one calculated by FSI simulations are all less than 5%.

CONCLUSIONS

The results suggest that the proposed multi-objective optimization method has the potential for application in optimizing pulsatile VAD hemocompatibility, and may also be applied to other blood-wetted devices.

High-speed visualization of disturbed pathlines in axial flow ventricular assist device under pulsatile conditions

OBJECTIVE

To investigate potentially prothrombotic flow patterns within an axial flow ventricular assist device under clinically relevant pulsatile hemodynamic conditions.

METHODS

A transparent replica of the HeartMate-II left ventricular assist device (Thoratec, Pleasanton, Calif) was visualized using a high speed camera at both low and high frame rates (125 and 3000 fps). Three steady-state conditions were studied: nominal (4.5 lpm), low flow (3.0 lpm), and high flow (6.0 lpm). Time-varying conditions were introduced with an external pulsatile pump that modulated the flow rate by approximately ± 50% of the mean, corresponding to a pulsatility index of 1.0.

RESULTS

At nominal and high flow rates, the path lines within the upstream region were generally stable, well attached, and streamlined. As the flow rate was reduced below 3.8 lpm, a rapid transition to a chaotic velocity field occurred, exhibiting a large toroidal vortex adjacent to the upstream bearing. The pathlines in the downstream stator section were consistently chaotic for all hemodynamic conditions investigated. It was common to observe tracer particles trapped within recirculation bubbles and drawn retrograde, causing repeated contact with the bearing surfaces. The addition of pulsatility caused the flow field to become periodically chaotic during the diastolic portion of the cardiac cycle depending on the instantaneous flow rate and acceleration.

CONCLUSIONS

The contribution of pulsatility by the native heart may induce a periodic disturbance to an otherwise stable flow field within an axial flow ventricular assist device, particularly during the diastolic and decelerating portion of the cardiac cycle. Potentially prothrombotic flow features were found to occur periodically in the region of the upstream bearing.

Ventricular assist device use in congenital heart disease with a comparison to heart transplant

Despite advances in medical and surgical therapies, some children with congenital heart disease (CHD) are not able to be adequately treated or palliated, leading them to develop progressive heart failure. As these patients progress to end-stage heart failure they pose a unique set of challenges. Heart transplant remains the standard of care; the donor pool, however, remains limited. Following the experience from the adult realm, the pediatric ventricular assist device (VAD) has emerged as a valid treatment option as a bridge to transplant. Due to the infrequent necessity and the uniqueness of each case, the pediatric VAD in the CHD population remains a topic with limited information. Given the experience in the adult realm, we were tasked with reviewing pediatric VADs and their use in patients with CHD and comparing this therapy to heart transplantation when possible.

Current approaches to device implantation in pediatric and congenital heart disease patients

The pediatric ventricular assist device (VAD) has recently shown substantial improvements in survival as a bridge to heart transplant for patients with end-stage heart failure. Since that time, its use has become much more frequent. With increasing utilization, additional questions have arisen including patient selection, timing of VAD implantation and device selection. These challenges are amplified by the uniqueness of each patient, the recent abundance of literature surrounding VAD use as well as the technological advancements in the devices themselves. Ideal strategies for device placement must be sought, for not only improved patient care, but also for optimal resource utilization. Here, we review the most relevant literature to highlight some of the challenges facing the heart failure specialist, and any physician, who will care for a child with a VAD.