BackgroundPalliative repair of single ventricle defects involve a series of open-heart surgeries where a single-ventricle (Fontan) circulation is established. As the patient ages, this paradoxical circulation gradually fails, because of its high venous pressure levels. Reversal of the Fontan paradox requires an extra subpulmonic energy that can be provided through mechanical assist devices. The objective of this study was to evaluate the hemodynamic performance of a totally implantable integrated aortic-turbine venous-assist (iATVA) system, which does not need an external drive power and maintains low venous pressure chronically, for the Fontan circulation.MethodsBlade designs of the co-rotating turbine and pump impellers were developed and 3 prototypes were manufactured. After verifying the single-ventricle physiology at a pulsatile in vitro circuit, the hemodynamic performance of the iATVA system was measured for pediatric and adult physiology, varying the aortic steal percentage and circuit configurations. The iATVA system was also tested at clinical off-design scenarios.ResultsThe prototype iATVA devices operate at approximately 800 revolutions per minute and extract up to 10% systemic blood from the aorta to use this hydrodynamic energy to drive a blood turbine, which in turn drives a mixed-flow venous pump passively. By transferring part of the available energy from the single-ventricle outlet to the venous side, the iATVA system is able to generate up to approximately 5 mm Hg venous recovery while supplying the entire caval flow.ConclusionsOur experiments show that a totally implantable iATVA system is feasible, which will eliminate the need for external power for Fontan mechanical venous assist and combat gradual postoperative venous remodeling and Fontan failure.

Introducing a blade curvature enhanced the hydrodynamic and hemolytic performance compared to the straight-blade configuration for the investigated centrifugal blood pump. The findings of this study provide new insights into centrifugal blood pump design by examining the influence of the blade curvature.

In the design of rotary blood pumps, the optimization of design parameters plays an essential role in enhancing the hydrodynamic performance and hemocompatibility. This study investigates the influence of the volute tongue angle as a volute geometric parameter on the hemodynamic characteristics of a blood pump. A numerical investigation on five different versions of volute designs is carried out by utilizing a computational fluid dynamics (CFD) software ANSYS-FLUENT. The effect of volute tongue angle is evaluated regarding the hydrodynamic performance, circumferential pressure distribution, the radial force, and the blood damage potential. A series of volute configurations are constructed with a fixed radial gap (5%), but varying tongue angles ranging from 10 to 50°. The relative hemolysis is assessed with the Eulerian based empirical power-law blood damage model. The pressure-flow rate characteristics of the volute designs at a range of rotational speeds are obtained from the experimental measurements by using the blood analog fluid. The results indicate an inverse relationship between hydraulic performance and the tongue angle; at higher tongue angles, a decrease in performance was observed. However, a higher tongue angle improves the net radial force acting on the impeller. The pump achieves the optimized performance at 20° of the tongue angle with the relatively high hydrodynamic performance and minor blood damage risk.

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Mechanical circulatory support (MCS) is used as a bridge-to-heart transplantation for end-stage failing Fontan patients with single-ventricle (SV) circulation. Donor shortage and complexity of the single-ventricle circulation physiology demands novel circulatory support systems and alternative solutions. An out-of-the-box circulation concept in which the left and right ventricles are switched with each other inspired a novel bi-ventricle MCS configuration for the failing Fontan patients. In the proposed configuration, the systemic circulation is maintained by a conventional mechanical ventricle assist device while the venous circulation is delegated to the native SV. This approach spares the SV and puts it to a new use at the right-side providing the most needed venous flow pulsatility. To analyze its feasibility and performance, 8 realistic Fontan circulation scenarios have been studied via a multi-compartmental lumped parameter cardiovascular model (LPM). Model is developed specifically for simulating the SV circulation and validated against pulsatile mock-up flow loop measurements for the ideal (Fontan), failed (VD) and assisted Fontan (PVR-cmcs) scenarios. The proposed surgical configuration maintained the cardiac index (3-3.5 l/min/m 2) providing a normal mean systemic arterial pressure. For a failed SV with low ejection fraction (EF=26%), representing a typical systemic failure, proposed configuration introduced a venous/pulmonary pulsatility of ~28 mmHg and a drop of 2 mmHg in central venous pressure (CVP) with acceptable pulmonary artery pressures (17.5 mmHg). In the pulmonary vascular resistance (PVR) failure model, it provided approximately 5 mmHg drop in CVP with venous/pulmonary pulsatility reaching ~22 mmHg. For high PVR failure case with a healthy SV (EF = 44%) pulmonary hypertension is likely to occur, indicating a need for precise functional assessment of the failed-ventricle before it is considered for the proposed arrangement. Comprehensive in vitro and in silico results encourage this concept as an economical alternative to the conventional bi-ventricle MCS pending animal experiments.