The Total Artificial Heart in End-Stage Congenital Heart Disease

A compact machine perfusion device for whole blood perfusion in isolated rat liver

We established a compact machine perfusion system for whole blood perfusion of rat liver by making use of oxygenation filters as an artificial lung. Livers removed from rats were divided into Krebs-Henseleit (control), 50% blood (hemoglobin: 7 g/dL), and whole blood (hemoglobin: 14 g/dL) groups, then perfused (total perfusate volume: 25 ml) with a small oxygenation filter at 37 °C for 120 min. Blood or perfusate was collected over time, and blood gas and blood cell were measured. In addition, bile volume and portal venous pressure measurements were taken. In all groups, the partial pressure of oxygen was controlled to approximately 400 mmHg. Flow rates were maintained at approximately about 20-30 ml/min according to liver size. Portal venous pressure was normal in the 50% blood and whole blood groups, while lower than the reference value in the Krebs-Henseleit group. Twice as much bile was produced in the 50% blood and whole blood groups relative with the Krebs-Henseleit group. We observed no differences in hemoglobin and red blood cell levels. Lactate levels were normal in the 50% blood and whole blood groups, but were elevated in the Krebs-Henseleit group. Our compact perfusion system using oxygenation filters was able to maintain rat liver function by perfusing a small amount of extracorporeal blood. This system is simple and stable, and may contribute to the future development of machine perfusion systems.

Biventricular assist devices and total artificial heart: Strategies and outcomes

In contrast to the advanced development of the left ventricular assist device (LVAD) therapy for advanced heart failure, the mechanical circulatory support (MCS) with biventricular assist device (BVAD) and total artificial heart (TAH) options remain challenging. The treatment strategy of BVAD and TAH therapy largely depends on the support duration. For example, an extracorporeal centrifugal pump, typically referred to as a temporary surgical extracorporeal right ventricular assist device, is implanted for the short term with acute right ventricular failure following LVAD implantation. Meanwhile, off-label use of a durable implantable LVAD is a strategy for long-term right ventricular support. Hence, this review focuses on the current treatment strategies and clinical outcomes based on each ventricle support duration. In addition, the issue of heart failure post-heart transplantation (post-HT) is explored. We will discuss MCS therapy options for post-HT recipients.

Mechanical circulatory support devices and treatment strategies for right heart failure

The importance of right heart failure (RHF) treatment is magnified over the years due to the increased risk of mortality. Additionally, the multifactorial origin and pathophysiological mechanisms of RHF render this clinical condition and the choices for appropriate therapeutic target strategies remain to be complex. The recent change in the United Network for Organ Sharing (UNOS) allocation criteria of heart transplant may have impacted for the number of left ventricular assist devices (LVADs), but LVADs still have been widely used to treat advanced heart failure, and 4.1 to 7.4% of LVAD patients require a right ventricular assist device (RVAD). In addition, patients admitted with primary left ventricular failure often need right ventricular support. Thus, there is unmet need for temporary or long-term support RVAD implantation exists. In RHF treatment with mechanical circulatory support (MCS) devices, the timing of the intervention and prediction of duration of the support play a major role in successful treatment and outcomes. In this review, we attempt to describe the prevalence and pathophysiological mechanisms of RHF origin, and provide an overview of existing treatment options, strategy and device choices for MCS treatment for RHF.

Impact of mechanical circulatory support on pediatric heart transplant candidates with elevated pulmonary vascular resistance

With the new era of increasing use of mechanical circulatory support (MCS) in children, seemingly more patients with elevated pulmonary vascular resistance (PVR) are having positive outcomes. The purpose of this study was to define the effect of MCS on pediatric patients listed for heart transplant with an elevated PVR. The United Network for Organ Sharing (UNOS) database was used to identify patients aged 0-18 at the time of listing for heart transplant between 2010 and 2019 who had PVR documented (n = 2081). Patients were divided into MCS (LVAD, RVAD, BiVAD, and TAH) and No MCS groups, then divided by PVR (PVR) at the time of listing: <3, 3-6, and >6 Wood units (WU). MCS was used in 20% overall (n = 426); 57% of those with PVR <3, 27% with PVR 3-6, and 16% with PVR >6. MCS, PVR <3 patients had a higher chance of positive waitlist outcome than all No MCS groups (vs. PVR <3, P = .049; vs. PVR 3-6, P = .004; vs. PVR >6, P < .001). MCS, PVR 3-6 patients had a higher chance of positive waitlist outcome than all No MCS groups (vs. PVR <3, P = .048; vs. PVR 3-6, P = .009; vs. PVR >6, P < .001). MCS, PVR >6 patients had a higher chance of positive waitlist outcome than No MCS, PVR >6 patients (P = .012). Within the No MCS group, patients with a PVR >6 had a higher incidence of negative waitlist outcome compared to PVR <3 (17% vs. 10%, P = .002); this was not the case in the MCS group (5% vs. 6%, P = .693). More patients in the MCS group were ventilator dependent (15% vs. 9%, P < .001) at the time of listing and less likely to have a functional status >50% (43% vs. 73%, P < .001). No significant differences in post-transplant survival were found in pairwise comparisons of MCS and No MCS PVR subgroups. Patients supported with MCS had a significantly higher chance of a positive waitlist outcome than those without such support regardless of PVR status. This was most pronounced with a PVR greater than 6 WU. MCS compared to No MCS patients had better waitlist survival and equivalent post-transplant survival. MCS patients, despite being more ill, had better overall survival regardless of PVR.

The total artificial heart in patients with congenital heart disease

Background

While ventricular assist devices (VADs) remain the cornerstone of mechanical circulatory support (MCS), the total artificial heart (TAH-t) has gained popularity for certain patients in whom VAD support is not ideal. Congenital heart disease (CHD) patients often have barriers to VAD placement due to anatomic and physiological variation and thus can benefit from the TAH-t. The purpose of this study is to analyze the differences in TAH application and outcomes in patients with and without CHD.

Methods

The SynCardia Department of Clinical Research provided data upon request for all TAH-t implantations worldwide from December 1985 to October 2019. These patients were divided into two groups by pre-implantation diagnosis of CHD and non-CHD.

Results

A total of 1,876 patients were identified. Eighty (4%) of these patients also carried a diagnosis of CHD. There was a higher proportion of children in the CHD cohort (16.3% vs. 2.1%, P<0.001) and this translated into a lower average age amongst the two groups (34±13 vs. 49±13 years, P<0.001). There were also significantly more females in the CHD group (22.8% vs. 12.8%, P=0.010). CHD patients were more likely to be supported with a 50 cc TAH-t (11.3% vs. 4.5%, P=0.005) while all other support characteristics, including duration of support, were similar between the groups. All measured outcomes were similar between CHD and non-CHD patients including positive outcome (alive on device or transplanted), 1-month conditional survival, and rate of Freedom Driver use.

Conclusions

TAH-t is an effective means to support patients with CHD. Patients with CHD had similar survival, support characteristics, and frequency of discharge compared to patients without CHD. As MCS continues to grow, its indications broadened, and its contraindications narrowed, more patient populations will see the benefit of the TAH's continuously developing technology.

Mechanical circulatory support in children: past, present and future

Rapid advances in the field of mechanical circulatory support (MCS) have dramatically changed the management of pediatric patients with heart failure. There is now emphasis on timely implantation of ventricular assist devices (VADs) to preserve or recover end-organ function, and increased focus on post-implant management to improve the stroke rate. Transplant waitlist mortality has significantly decreased in the era of VAD use. Devices approved for adults are being used off-label in children with excellent outcomes, allowing chronic therapy and discharge home to become part of pediatric VAD therapy.

Cardiac Assist Devices: Early Concepts, Current Technologies, and Future Innovations

Congestive heart failure (CHF) is a debilitating condition that afflicts tens of millions of people worldwide and is responsible for more deaths each year than all cancers combined. Because donor hearts for transplantation are in short supply, a safe and durable means of mechanical circulatory support could extend the lives and reduce the suffering of millions. But while the profusion of blood pumps available to clinicians in 2019 tend to work extremely well in the short term (hours to weeks/months), every long-term cardiac assist device on the market today is limited by the same two problems: infections caused by percutaneous drivelines and thrombotic events associated with the use of blood-contacting surfaces. A fundamental change in device design is needed to address both these problems and ultimately make a device that can support the heart indefinitely. Toward that end, several groups are currently developing devices without blood-contacting surfaces and/or extracorporeal power sources with the aim of providing a safe, tether-free means to support the failing heart over extended periods of time.

Extracorporeal Membrane Oxygenation (ECMO) Support in Special Patient Populations-The Bidirectional Glenn and Fontan Circulations

Extracorporeal membrane oxygenation (ECMO) is a support modality used within the pediatric cardiac ICU population as a bridge to recovery or decision in the setting of acute myocardial decompensation, support for combined cardiopulmonary failure or in the setting of refractory cardiopulmonary arrest. Patients with univentricular physiology are at particular risk for decompensation requiring ECMO support. This review will focus upon current evidence and techniques for ECMO support of single ventricle patients who have undergone a stage II bidirectional Glenn procedure or the stage III Fontan procedure.