First Use of HeartMate 3 in a Failing Fontan Circulation

Use of Intracorporeal Durable LVAD Support in Children Using HVAD or HeartMate 3-A EUROMACS Analysis

Purpose: The withdrawal of HVAD in 2021 created a concern for the pediatric population. The alternative implantable centrifugal blood pump HeartMate 3 has since been used more frequently in children. This paper analyses the outcome of children on LVAD support provided with an HVAD or HM3. Methods: A retrospective analysis of the EUROMACS database on children supported with VAD < 19 years of age from 1 January 2009 to 1 December 2021 was conducted. All patients with an LVAD and either an HVAD or HM3 were included. Patients with missing data on VAD status and/or missing baseline and/or follow up information were excluded. Kaplan-Meier survival analysis was performed to evaluate survival differences. Analyses were performed using Fisher's exact test. Results: The study included 150 implantations in 142 patients with 128 implants using an HVAD compared to 28 implants using an HM3. Nine patients (6%) needed temporary right ventricular mechanical support, which was significantly higher in the HM3 group, with 25% (p: 0.01). Patients in the HVAD group were significantly younger (12.7 vs. 14.5 years, p: 0.01), weighed less (45.7 vs. 60 kg, p: <0.000) and had lower BSA values (1.3 vs. 1.6 m2, p: <0.000). Median support time was 204 days. Overall, 98 patients (69%) were discharged and sent home, while 87% were discharged in group HM3 (p: ns). A total of 123 children (86%) survived to transplantation, recovery or are ongoing, without differences between groups. In the HVAD group, 10 patients (8%) died while on support, whereas in 12% of HM3 patients died (p: 0.7). Conclusions: Survival in children implanted with an HM3 was excellent. Almost 90% were discharged and sent home on the device.

Passive performance evaluation and validation of a viscous impeller pump for subpulmonary fontan circulatory support

Patients with single ventricle defects undergoing the Fontan procedure eventually face Fontan failure. Long-term cavopulmonary assist devices using rotary pump technologies are currently being developed as a subpulmonary power source to prevent and treat Fontan failure. Low hydraulic resistance is a critical safety requirement in the event of pump failure (0 RPM) as a modest 2 mmHg cavopulmonary pressure drop can compromise patient hemodynamics. The goal of this study is therefore to assess the passive performance of a viscous impeller pump (VIP) we are developing for Fontan patients, and validate flow simulations against in-vitro data. Two different blade heights (1.09 mm vs 1.62 mm) and a blank housing model were tested using a mock circulatory loop (MCL) with cardiac output ranging from 3 to 11 L/min. Three-dimensional flow simulations were performed and compared against MCL data. In-silico and MCL results demonstrated a pressure drop of < 2 mmHg at a cardiac output of 7 L/min for both blade heights. There was good agreement between simulation and MCL results for pressure loss (mean difference - 0.23 mmHg 95% CI [0.24-0.71]). Compared to the blank housing model, low wall shear stress area and oscillatory shear index on the pump surface were low, and mean washout times were within 2 s. This study demonstrated the low resistance characteristic of current VIP designs in the failed condition that results in clinically acceptable minimal pressure loss without increased washout time as compared to a blank housing model under normal cardiac output in Fontan patients.

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).

Ventricular assist device for end-stage adult congenital heart disease patients: Current status

As long-term surgical outcome of congenital heart disease has continued to improve, most pediatric patients with congenital heart disease are able to reach adulthood. However, adult congenital heart disease (ACHD) patients have increased risk of arrhythmia, valvular diseases, infectious endocarditis, and heart failure. The end-stage ACHD patients with advanced heart failure may require mechanical circulatory support to improve the heart failure symptoms or to recover from circulatory collapse, and may eventually aim to heart transplant or destination therapy. In general, long-term mechanical support for dilated cardiomyopathy or ischemic cardiomyopathy has been achieved with left ventricular assist device with excellent survival outcomes and improved quality of life. However, the ventricular assist device for end-stage ACHD patients can be challenging due to patient-specific anatomical feature, multiple histories of surgical and catheter-based interventions and possible multiple end-organ dysfunctions, and offered less frequently compared to non-ACHD patients. The Interagency Registry for Mechanically Assisted Circulatory Support data published recently showed that ACHD patients receiving long-term mechanical circulatory support consisted <1 % of all registrants and had higher mortality after mechanical support than non-ACHD patients. However, the ACHD patients supported with left ventricular assist device had similar survival with non-ACHD patients and a large proportion of the mortality difference between ACHD and non-ACHD patients seemed to result from operative and perioperative factors. Therefore, the ventricular assist device therapy can be an excellent treatment for selected ACHD patients. In this paper, we describe the current status of ventricular assist device support for end-stage ACHD patients and consideration to the future.

Case report: Heart Mate III for systemic right ventricular support in a patient with hypoplastic left heart syndrome

Ventricular assist device implantation presents a possible bridge to heart transplantation for patients with failing Fontan physiology. However, evidence regarding outcome and possible pitfalls associated with the Fontan circulation is still insufficient. We describe the course of a 13-year-old male, who was born with hypoplastic left heart syndrome and underwent HeartMate III implantation due to refractory failure of the systemic right ventricle.

Computational Modeling of the Penn State Fontan Circulation Assist Device

To address the increasing number of failing Fontan patients, Penn State University and the Penn State Hershey Medical Center are developing a centrifugal blood pump for long-term mechanical support. Computational fluid dynamics (CFD) modeling of the Penn State Fontan Circulatory Assist Device (FCAD) was performed to understand hemodynamics within the pump and its potential for hemolysis and thrombosis. CFD velocity and pressure results were first validated against experimental data and found to be within the standard deviations of the velocities and within 5% of the pressures. Further simulations performed with a human blood model found that most of the fluid domain was subjected to low shear stress (<50 Pa), with areas of highest stress around the rotor blade tips that increased with pump flow rate and rotor speed (138-178 Pa). However, the stresses compared well to previous CFD studies of commercial blood pumps and remained mostly below common thresholds of hemolysis and platelet activation. Additionally, few regions of low shear rate were observed within the FCAD, signifying minimal potential for platelet adhesion. These results further emphasize the FCAD's potential that has been observed previously in experimental and animal studies.

Considerations in Critical Care and Anesthetic Management of Adult Patients Living with Fontan Circulation

The Fontan procedure is a staged palliation for various complex congenital cardiac lesions, including tricuspid atresia (TA), pulmonary atresia (PA), hypoplastic left heart syndrome (HLHS), and double inlet left ventricle (DILV), all of which involve a functional single-ventricle physiology. The complexity of the patients' original anatomy combined with the anatomical and physiological consequences of the Fontan circulation creates challenges. Teens and adults living with Fontan palliation will need perioperative support for non-cardiac surgery, peripartum management for labor and delivery, interventions related to their structural heart disease, electrophysiology procedures, pacemakers, cardioversions, cardiac surgery, transplant, and advanced mechanical support. This review focuses on the anesthetic and ICU management of these patients during their perioperative journey, with an emphasis on the continuity of pre-intervention planning, referral pathways, and post-intervention intensive care unit (ICU) management. Requests for recipes and doses of medications are frequent; however, as in normal anesthesia and ICU practice, the method of anesthesia and dosing are dependent on the presenting medical/surgical conditions and the underlying anatomy and physiological reserve. A patient with Fontan palliation in their early 20s attending school full-time with a cavopulmonary connection is likely to have more reserve than a patient in their late 40s with an atrio- pulmonary (AP) Fontan at home waiting for a heart transplant. Each case will require an anesthetic and critical care plan tailored to their situation. The critical care environment is a natural extension of the anesthetic management of a patient, with complex considerations for a patient with Fontan palliation.

Computational Investigation of Anastomosis Options of a Right-Heart Pump to Patient Specific Pulmonary Arteries

Patients with Fontan circulation have increased risk of heart failure, but are not always candidates for heart transplant, leading to the development of the subpulmonic Penn State Fontan Circulation Assist Device. The aim of this study was to use patient-specific computational fluid dynamics simulations to evaluate anastomosis options for implanting this device. Simulations were performed of the pre-surgical anatomy as well as four surgical options: a T-junction and three Y-grafts. Cases were evaluated based on several fluid-dynamic quantities. The impact of imbalanced left-right pulmonary flow distribution was also investigated. Results showed that a 12-mm Y-graft was the most energy efficient. However, an 8-mm graft showed more favorable wall shear stress distribution, indicating lower risk of thrombosis and endothelial damage. The 8-mm Y-grafts also showed a more balanced pulmonary flow split, and lower residence time, also indicating lower thrombosis risk. The relative performance of the surgical options was largely unchanged whether or not the pulmonary vascular resistance remained imbalanced post-implantation.

Experimental Hemodynamics within the Penn State Fontan Circulatory Assist Device

For children born with a single functional ventricle, the Fontan operation bypasses the right ventricle by forming a four-way total cavopulmonary connection adapting the existing ventricle for the systemic circulation. However, upon adulthood, many Fontan patients exhibit low cardiac output and elevated venous pressure, eventually requiring a heart transplantation. Despite efforts to develop a Fontan pump or use an existing ventricular assist device for failing Fontan support, there is still no device designed or tested for subpulmonary support. Penn State University is developing a hydrodynamically levitated Fontan circulatory assist device (FCAD) for bridge-to-transplant or destination therapy. The FCAD hemodynamics, at both steady and pulsatile conditions for three pump operating conditions, were quantified using particle image velocimetry to determine the velocity magnitudes and Reynolds normal and shear stresses. Data were acquired at three planes (0 mm and ±25% of the radius) for the inferior and superior vena cavae inlets and the pulmonary artery outlet. The inlets had a blunt velocity profile that became skewed towards the collecting volute as fluid approached the rotor. At the outlet, regardless of the flow condition, a high-velocity jet exited the volute and moved downstream in a helical pattern. Turbulent stresses observed at the volute exit were influenced by the rotor's rotation. Regardless of inlet conditions, the pump demonstrated advantageous behavior for clinical use with a predictable flow field and a low risk of platelet adhesion and hemolysis based on calculated wall shear rates and turbulent stresses, respectively.

Chronic Ventricular Assist Device Support in Adult Congenital Heart Disease Patients: A Children's Hospital Perspective

With improvement in early surgical outcomes in patients with complex congenital heart disease, most patients are now expected to survive to adulthood. As adult congenital heart disease (ACHD) patients age, they are at risk of heart failure, which has become the leading cause of mortality in ACHD. Some who develop advanced heart failure may not be candidates for transplant, and chronic ventricular assist device (VAD) therapy may be the only means of survival. There is limited experience with chronic VAD therapy in ACHD patients, and the outcomes are not well delineated. We describe our center's experience with chronic VAD therapy in ACHD patients receiving care exclusively within our children's hospital.

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.

Systemic ventricular assist device support of the Fontan circulation yields promising outcomes: An analysis of The Society of Thoracic Surgeons Pedimacs and Intermacs Databases

BACKGROUND

Outcomes of ventricular assist device (VAD) support in patients with Fontan circulatory failure (or failing Fontan physiology) are largely unknown.

METHODS

We conducted a retrospective analysis of patients with a Fontan circulation who underwent VAD implant in the Society of Thoracic Surgeons Pedimacs and Intermacs Databases from September 19, 2012, to December 31, 2019.

RESULTS

We identified 55 Fontan patients who had undergone VAD implant with a median age at implantation of 10.2 years (interquartile range, 6.4-16.9 years) and weight, 26.8 kg (interquartile range, 17.7-53.8 years). More VADs were implanted in 2018-2019 than in 2012-2017 (28 vs 27; P = .01). The later era had higher pre-VAD glomerular filtration rate (101.1 ± 48.5 vs 71.2 ± 34.9; P = .02); there was no difference in Interagency Registry for Mechanically Assisted Circulatory Support profile (P = .69). Kaplan-Meier survival on device was 76% at 6 months with no difference by era. Competing outcomes demonstrated a positive outcome of 81% (alive on VAD, transplanted, or recovered) at 6 months, with 58% of mortality occurring during month 1. Median length of support was 3.8 months (interquartile range, 0.6-6.9 months). Five patients were supported for >1 year with no added mortality; the longest support time was 4 years, 7 months. Adverse event rates included pump thrombosis incidence of 4% (3.3 out of 100 patient-months), stroke 5.5% (1.4 out of 100 patient-months), gastrointestinal bleeding of 7% (2.6 out of 100 patient-months), and nongastrointestinal bleeding of 9% (2.3 out of 100 patient-months).

CONCLUSIONS

This is the largest reported analysis of systemic VAD support of Fontan patients. VAD support of the Fontan circulation is becoming more frequent. This analysis demonstrates that VAD use in this growing population can yield promising outcomes.

Transplantation and Arch Repair in Fontan 3 Years after HeartMate 3: Technical Considerations

We previously reported the first successful implantation of the Heartmate 3^TM in a Fontan patient. We now report his successful transplantation after 1,104 days of support, the longest reported bridge to transplantation of a Fontan patient. We describe our operative technique complicated by not only the Fontan anatomy and ventricular assist device (VAD) explanation but also a >10cm ascending and aortic arch aneurysm. Additionally, the post-transplant hemodynamics of this patient appear to demonstrate that effective VAD support may induce reversal of chronic effects of the failing Fontan circulation, which in this case was the elimination of his aorto-pulmonary collateral burden.

Ventricular Assist Device Therapy in the Fontan Circulation

The number of Fontan patients with circulatory failure and systolic dysfunction is growing rapidly. The last decade has demonstrated that ventricular assist device (VAD) is an effective therapy in properly selected patients. Herein, we discuss the current approach to patient selection, implantation, and patient management.

Transplantation for Congenital Heart Disease: Focus on the Impact of Functionally Univentricular Versus Biventricular Circulation

BACKGROUND

Varying single center data exist regarding the posttransplant outcomes of patients with single ventricle circulation, particularly following the Fontan operation. We sought to better elucidate these results in patients with congenital heart disease (CHD) through combining two national databases.

METHODS

The United Network for Organ Sharing (UNOS) transplantation database was merged with the Pediatric Health Information System (PHIS), an administrative database with 71% of UNOS patients matched. Patients undergoing transplantation at a PHIS hospital from 2006 to 2017 were categorized as single ventricle or biventricular strategy based on their diagnoses and procedures in 90% of patients. When known, single ventricle patients were further analyzed by their palliative stage post-Glenn or post-Fontan (known in 31%).

RESULTS

A total of 1,517 CHD transplantations were identified, 67% with single ventricle strategy (1,016). Single ventricle, biventricular, and indeterminate patients had similar survival (log-rank P > .1). Risk factors for mortality in patients with CHD were extracorporeal membrane oxygenation (ECMO) support at transplant (hazard: 2.27), ABO blood type incompatibility (hazard: 1.61), African American recipient (hazard 1.42), and liver dysfunction (hazard 1.29). A total of 130 confirmed Fontan and 185 confirmed bidirectional Glenn patients underwent transplantation, each with survival equivalent to biventricular patients (log-rank P > .500). For Fontan patients, renal dysfunction (hazard: 5.40) and transplant <1 year after Fontan (hazard 2.82) were found to be associated with mortality.

CONCLUSIONS

Single ventricle patients, as a group, experience similar outcomes as biventricular patients with CHD undergoing transplantation, and this extends to Fontan patients. Risk factors for mortality correlate with end-organ dysfunction as well as race and ABO blood type incompatibility in the CHD population.

Transplant and mechanical circulatory support in patients with adult congenital heart disease

Advances in surgery and pediatric care over the past decades have achieved improved survival for children born with congenital heart disease (CHD) and have produced a large, growing population of patients with adult congenital heart disease (ACHD). Heart failure has emerged as the leading cause of death and a major cause of morbidity among the ACHD population, while as little evidence supports the efficacy of guideline-directed medical therapies in this population. It is increasingly important that clinicians caring for these patients understand how to utilize mechanical circulatory support (MCS) in ACHD. In this review, we summarize the data on transplantation and MCS in the ACHD-heart failure population and provide a framework for how ACHD patients may benefit from advanced heart failure therapies like transplantation and MCS.

Ventricular Assist Device Therapy and Fontan: A Story of Supply and Demand

The last 10 years have seen an increase in the number of Fontan patients with heart failure. There has been a coincident rapid evolution in the field of pediatric and congenital heart disease ventricular assist device therapy. Herein, we describe the existing body of literature regarding the use of ventricular assist device therapy in the Fontan circulation as well as the current approach to clinical decision-making and device implantation within the field.

Review on Mechanical Support and Cell-Based Therapies for the Prevention and Recovery of the Failed Fontan-Kreutzer Circulation

Though the current staged surgical strategy for palliation of single ventricle heart disease, culminating in a Fontan circulation, has increased short-term survival, mounting evidence has shown that the single ventricle, especially a morphologic right ventricle (RV), is inadequate for long-term circulatory support. In addition to high rates of ventricular failure, high central venous pressures (CVP) lead to liver fibrosis or cirrhosis, lymphatic dysfunction, kidney failure, and other comorbidities. In this review, we discuss the complications seen with Fontan physiology, including causes of ventricular and multi-organ failure. We then evaluate the clinical use, results, and limitations of long-term mechanical assist devices intended to reduce RV work and high CVP, as well as biological therapies for failed Fontan circulations. Finally, we discuss experimental tissue engineering solutions designed to prevent Fontan circulation failure and evaluate knowledge gaps and needed technology development to realize a more robust single ventricle therapy.

HeartMate III as a Bridge to Transplantation in an Adolescent With Failed Fontan Circulation

HeartMate III is an emerging, small-sized centrifugal ventricular assist device. Its lower pump thrombosis and stroke rates make it favorable for use in pediatrics. We report the use of HeartMate III as a bridge to transplantation in an adolescent with failed Fontan circulation. (Level of Difficulty: Advanced.).