Next Generation Development of Hybrid Continuous Flow Pediatric Total Artificial Heart Technology: Design-Build-Test.

To address the unmet clinical need for pediatric circulatory support, we are developing an operationally versatile, hybrid, continuous-flow, total artificial heart ("Dragon Heart"). This device integrates a magnetically levitated axial and centrifugal blood pump. Here, we utilized a validated axial flow pump, and we focused on the development of the centrifugal pump. A motor was integrated to drive the centrifugal pump, achieving 50% size reduction. The motor design was simulated by finite element analysis, and pump design improvement was attained by computational fluid dynamics. A prototype centrifugal pump was constructed from biocompatible 3D printed parts for the housing and machined metal parts for the drive system. Centrifugal prototype testing was conducted using water and then bovine blood. The fully combined device ( i.e. , axial pump nested inside of the centrifugal pump) was tested to ensure proper operation. We demonstrated the hydraulic performance of the two pumps operating in tandem, and we found that the centrifugal blood pump performance was not adversely impacted by the simultaneous operation of the axial blood pump. The current iteration of this design achieved a range of operation overlapping our target range. Future design iterations will further reduce size and incorporate complete and active magnetic levitation.

Channel impeller design for centrifugal blood pump in hybrid pediatric total artificial heart: Modeling, magnet integration, and hydraulic experiments.

BACKGROUND: The purpose of this research is to address ongoing device shortfalls for pediatric patients by developing a novel pediatric hybrid total artificial heart (TAH). The valveless magnetically-levitated MCS device (Dragon Heart) has only two moving parts, integrates an axial and centrifugal blood pump into a single device, and will occupy a compact footprint within the chest for the pediatric patient population. METHODS: Prior work on the Dragon Heart focused on the development of pump designs to achieve hemodynamic requirements. The impeller of these pumps was shaft-driven and thus could not be integrated for testing. The presented research leverages an existing magnetically levitated axial flow pump and focuses on centrifugal pump development. Using the axial pump diameter as a geometric constraint, a shaftless, magnetically supported centrifugal pump was designed for placement circumferentially around the axial pump domain. The new design process included the computational analysis of more than 50 potential centrifugal impeller geometries. The resulting centrifugal pump designs were prototyped and tested for levitation and no-load rotation, followed by in vitro testing using a blood analog. To meet physiologic demands, target performance goals were pressure rises exceeding 90 mm Hg for flow rates of 1-5 L/min with operating speeds of less than 5000 RPM. RESULTS: Three puck-shaped, channel impellers for the centrifugal blood pump were selected based on achieving performance and space requirements for magnetic integration. A quasi-steady flow analysis revealed that the impeller rotational position led to a pulsatile component in the pressure generation. After prototyping, the centrifugal prototypes (3, 4, and 5 channeled designs) demonstrated levitation and no-load rotation. Hydraulic experiments established pressure generation capabilities beyond target requirements. The pressure-flow performance of the prototypes followed expected trends with a dependence on rotational speed. Pulsatile blood flow was observed without pump-speed modulation due to rotating channel passage frequency. CONCLUSION: The results are promising in the advancement of this pediatric TAH. The channeled impeller design creates pressure-flow curves that are decoupled from the flow rate, a benefit that could reduce the required controller inputs and improve treatment of hypertensive patients.

Novel hybrid total artificial heart with integrated oxygenator.

There continues to be an unmet therapeutic need for an alternative treatment strategy for respiratory distress and lung disease. We are developing a portable cardiopulmonary support system that integrates an implantable oxygenator with a hybrid, dual-support, continuous-flow total artificial heart (TAH). The TAH has a centrifugal flow pump that is rotating about an axial flow pump. By attaching the hollow fiber bundle of the oxygenator to the base of the TAH, we establish a new cardiopulmonary support technology that permits a patient to be ambulatory during usage. In this study, we investigated the design and improvement of the blood flow pathway from the inflow-to-outflow of four oxygenators using a mathematical model and computational fluid dynamics (CFD). Pressure loss and gas transport through diffusion were examined to assess oxygenator design. The oxygenator designs led to a resistance-driven pressure loss range of less than 35 mmHg for flow rates of 1-7 L/min. All of the designs met requirements. The configuration having an outside-to-inside blood flow direction was found to have higher oxygen transport. Based on this advantageous flow direction, two designs (Model 1 and 3) were then integrated with the axial-flow impeller of the TAH for simulation. Flow rates of 1-7 L/min and speeds of 10,000-16,000 RPM were analyzed. Blood damage studies were performed, and Model 1 demonstrated the lowest potential for hemolysis. Future work will focus on developing and testing a physical prototype for integration into the new cardiopulmonary assist system.

Challenges of prenatal diagnosis of fetal hypoplastic aortic arch and predication of the need for intervention.

Prenatal diagnosis of hypoplastic aortic arch and coarctation of aorta is still challenging and remains one of the most difficult cardiac defects to diagnose. The results reveal a significant improvement of prenatal diagnosis of hypoplastic arch and coarctation of aorta. The data also shows the significant overlapping of fetal aortic isthmus z score between the infants who need the arch procedure and those who do not.

Development of the Centrifugal Blood Pump for a Hybrid Continuous Flow Pediatric Total Artificial Heart: Model, Make, Measure.

Clinically-available blood pumps and total artificial hearts for pediatric patients continue to lag well behind those developed for adults. We are developing a hybrid, continuous-flow, magnetically levitated, pediatric total artificial heart (TAH). The hybrid TAH design integrates both an axial and centrifugal blood pump within a single, compact housing. The centrifugal pump rotates around the separate axial pump domain, and both impellers rotate around a common central axis. Here, we concentrate our development effort on the centrifugal blood pump by performing computational fluid dynamics (CFD) analysis of the blood flow through the pump. We also conducted transient CFD analyses (quasi-steady and transient rotational sliding interfaces) to assess the pump's dynamic performance conditions. Through modeling, we estimated the pressure generation, scalar stress levels, and fluid forces exerted on the magnetically levitated impellers. To further the development of the centrifugal pump, we also built magnetically-supported prototypes and tested these in an in vitro hydraulic flow loop and via 4-h blood bag hemolytic studies (n = 6) using bovine blood. The magnetically levitated centrifugal prototype delivered 0-6.75 L/min at 0-182 mmHg for 2,750-4,250 RPM. Computations predicted lower pressure-flow performance results than measured by testing; axial and radial fluid forces were found to be <3 N, and mechanical power usage was predicted to be <5 Watts. Blood damage indices (power law weighted exposure time and scalar stress) were <2%. All data trends followed expectations for the centrifugal pump design. Six peaks in the pressure rise were observed in the quasi-steady and transient simulations, correlating to the blade passage frequency of the 6-bladed impeller. The average N.I.H value (n = 6) was determined to be 0.09 ± 0.02 g/100 L, which is higher than desired and must be addressed through design improvement. These data serve as a strong foundation to build upon in the next development phase, whereby we will integrate the axial flow pump component.

Invited commentary: Total anomalous pulmonary venous connection remains a challenging pediatric disease.

Cervantes-Salazar and colleagues report the long-term surgical outcomes of 414 patients with total anomalous pulmonary venous connection (TAPVC) from January 2003 to June 2019. With an overall survival rate of 87.2% from 2003 to 2019, the authors found that an increased mortality risk was associated with infracardiac TAPVC, pulmonary venous obstruction, and postoperative mechanical ventilation. Their comprehensive study with a large sample size of varying age groups, and patients with late referrals for surgery, provide valuable insight into TAPVC surgical outcomes. Improved survival for these patients continues to be a major goal of clinical teams striving to transform treatment paradigms. The promising result of the study reported by Cervantes-Salazar and colleagues gives our field hope for a better future for these patients.

Invited commentary for: Essential role of cardiac computed tomography for surgical decision making in children with total anomalous pulmonary venous connection and single ventricle.

Thousands of neonates are born each year with complex congenital heart defects, such as total anomalous pulmonary venous connection combined with single ventricle physiology. This dual diagnosis with significant vessel and ventricular complexity requires alternative additional imaging to fully visualize the anatomical challenge and devise the appropriate treatment strategy for the patient.

Technology landscape of pediatric mechanical circulatory support devices: A systematic review 2010-2021.

BACKGROUND: Mechanical circulatory support (MCS) devices, such as ventricular assist devices (VADs) and total artificial hearts (TAHs), have become a vital therapeutic option in the treatment of end-stage heart failure for adult patients. Such therapeutic options continue to be limited for pediatric patients. Clinicians initially adapted or scaled existing adult devices for pediatric patients; however, these adult devices are not designed to support the anatomical structure and varying flow capacities required for this population and are generally operated "off-design," which risks complications such as hemolysis and thrombosis. Devices designed specifically for the pediatric population which seek to address these shortcomings are now emerging and gaining FDA approval. METHODS: To analyze the competitive landscape of pediatric MCS devices, we conducted a systematic literature review. Approximately 27 devices were studied in detail: 8 were established or previously approved designs, and 19 were under development (11 VADs, 5 Fontan assist devices, and 3 TAHs). RESULTS: Despite significant progress, there is still no pediatric pump technology that satisfies the unique and distinct design constraints and requirements to support pediatric patients, including the wide range of patient sizes, increased cardiovascular demand with growth, and anatomic and physiologic heterogeneity of congenital heart disease. CONCLUSIONS: Forward-thinking design solutions are required to overcome these challenges and to ensure the translation of new therapeutic MCS devices for pediatric patients.

Invited commentary: A prospective randomized trial on parents' disease knowledge and quality of life. Shall WeChat about telehealth?

WeChat and access to wireless communication may offer a continuum of care following medical and surgical intervention. This cardiac surgery research study evaluates the process of parental education and social support following pediatric cardiac surgery utilizing standard of care compared to telehealth.

Giant coronary artery aneurysm in infantile Kawasaki disease: When to use cardiac computed tomography angiography.

Transthoracic echocardiography is the imaging modality of choice for the detection of coronary artery aneurysms (CAAs) in Kawasaki disease. However, cardiac computed tomography angiography is useful in the diagnosis of distal CAAs.

Left innominate vein creation using left internal jugular vein tunneled to right internal jugular vein.

BACKGROUND: Left innominate vein occlusion is a known complication of pacemaker and central venous catheter placement. For dialysis-dependent patients with an arteriovenous fistula (AVF), this can prevent successful hemodialysis and may require surgical intervention. CASE REPORT: An 8-month-old male was diagnosed with hemolytic uremic syndrome and became dialysis-dependent at 11 months of age. After multiple vascular access and peritoneal dialysis complications, the patient had construction of a brachiobasalic AVF in his left arm at 13 years old. While waiting for the AVF to mature, an attempt to remove a previously placed left subclavian vein port-a-cath was unsuccessful and a follow-up imaging revealed that the vessel had become occluded. The fistula remained patent, but due to arm swelling and venous obstruction, his fistula was not accessible. Multiple attempts to percutaneously cross the left innominate vein were unsuccessful and the patient was referred for surgical intervention. At 15 years old, the patient was taken to the operating room for transposition of the left internal jugular vein (LIJ) to the right internal jugular vein (RIJ). The LIJ was transected under the mandible and anastomosed to the RIJ. Subsequently the patient underwent VWING insertion rather than venous transposition for constant site dialysis. Although he has required frequent transcatheter dilation of the LIJ-RIJ anastomosis, the patient was successfully dialyzed using this fistula for 5 years. The patient received a cadaveric renal transplant at 5 years 20 days. CONCLUSIONS: In cases of left innominate vein stenosis, transposing the LIJ can create a new left innominate vein that can alleviate venous hypertension and preserve fistula function. This procedure avoids sternotomy and only requires one anastomosis.

Adult congenital pulmonary valve insertion using a new bioprosthetic aortic valve: Inspiris.

We describe successful placement of the Inspiris Resilia aortic valve in the pulmonary position. This valve has advantages for immediate benefit and future percutaneous interventions, making it a promising prosthesis for adult congenital patients.

Efficient approach to superior vena cava baffle stenosis following the Mustard procedure: Expanding the role of a mechanical rotating dilator sheath for lead extraction.

INTRODUCTION: In adult congenital patients with transposition of the great arteries originally treated with the Mustard (atrial switch) procedure, the most common reason for re-intervention is baffle stenosis. This may be exacerbated by permanent transvenous pacemaker lead placement across the baffle. CASE REPORT: A 47-year-old female status post Mustard procedure performed at 15 months old presented with a high-grade stenosis of the superior vena cava (SVC) baffle from the SVC to the left atrium, with a nonfunctional permanent pacemaker lead passing through the baffle. A mechanical rotating dilator sheath was used for attempted lead extraction, relieving the baffle stenosis almost completely as a secondary effect, before the placement of a 10 × 27 mm Visipro balloon-expandable stent in the SVC baffle. CONCLUSIONS: Use of the mechanical rotating dilator sheath is an evolving treatment strategy in adult congenital heart disease to minimize the risk of bleeding, trauma to surrounding structures, and death. Its ability to fully alleviate baffle stenosis even when full lead extraction is not feasible or is associated with significant procedural risk, further demonstrates its expanded role in this patient population. A multidisciplinary approach and great diligence must be employed to avoid potential complications.

Fontan procedure: Early outcomes of 87 consecutive patients in a tertiary care center.

Al Absi and colleagues report their early results of the Fontan procedure in 87 consecutive patients between August 2008 and July 2017 in a tertiary care hospital. The use of the intra/extracardiac fenestration is a promising modification because it is unlikely to be occluded by surrounding tissue and may be associated with decreased pleural effusions, length of hospital stay, and incidence of postoperative arrhythmias.

Oblique coronary artery prolongation in anomalous left coronary artery arising from the pulmonary artery: A case series.

BACKGROUND: Anomalous left coronary artery (LMCA) arising from the pulmonary artery (ALCAPA) is a life-threatening congenital birth defect. Prompt surgical correction by reimplantation of the LMCA into the aorta is the treatment of choice, however, unfavorable LCA location or length can make direct reimplantation difficult or even impossible without causing significant stretching or tension on the LMCA. This tension can lead to stenosis of the artery and coronary ischemia and must be avoided if possible. METHODS: A chart review from January 2010 to December 2018 of patients who had ALCAPA repair. Patients were excluded if direct reimplantation was possible. Herein, we describe four cases in which remote LMCA position necessitated the creation of a tubular prolongation of the LMCA. RESULTS: A generous coronary button from the pulmonary artery along with the oblique flap of aorta served as the prolongation of the left main coronary artery. This allowed for a tension-free anastomosis using native tissue with the ability to grow with the patient. The pulmonary artery and the aorta were then patched using pericardial tissue. All four patients had improvement in left ventricular function and degree of mitral regurgitation within weeks of surgery. No patient required extracorporeal membrane oxygenation support. Subsequent long-term angiographic follow-up has revealed excellent durability and patency of these coronary conduits. CONCLUSIONS: The variable nature of ALCAPA requires modification of the surgical approach on a patient by patient basis, and the above described technique adds an alternate and reliable long-term treatment option.

Mechanical Circulatory Support of the Right Ventricle for Adult and Pediatric Patients With Heart Failure.

The clinical implementation of mechanical circulatory assistance for a significantly dysfunctional or failing left ventricle as a bridge-to-transplant or bridge-to-recovery is on the rise. Thousands of patients with left-sided heart failure are readily benefitting from these life-saving technologies, and left ventricular failure often leads to severe right ventricular dysfunction or failure. Right ventricular failure (RVF) has a high rate of mortality caused by the risk of multisystem organ failure and prolonged hospitalization for patients after treatment. The use of a blood pump to support the left ventricle also typically results in an increase in right ventricular preload and may impair right ventricular contractility during left ventricular unloading. Patients with RVF might also suffer from severe pulmonary dysfunction, cardiac defects, congenital heart disease states, or a heterogeneity of cardiophysiologic challenges because of symptomatic congestive heart failure. Thus, the uniqueness and complexity of RVF is emerging as a new domain of significant clinical interest that motivates the development of right ventricular assist devices. In this review, we present the current state-of-the-art for clinically used blood pumps to support adults and pediatric patients with right ventricular dysfunction or failure concomitant with left ventricular failure. New innovative devices specifically for RVF are also highlighted. There continues to be a compelling need for novel treatment options to support patients with significant right heart dysfunction or failure.