A Volume-Adjustable Artificial Womb for Extremely Preterm Infants.

More than 13 million children are born preterm annually. Prematurity-related mortality accounts for 0.9 million deaths worldwide. The majority of those affected are Extremely Preterm Infants (gestational age less than 28 weeks). Immaturity causes organ failure and specific morbidities like germinal matrix hemorrhage, bronchopulmonary dysplasia, and necrotizing enterocolitis. Artificial womb and placenta technologies address these issues. As a bridge-to-life technology, they provide a liquid environment to allow organ maturation under more physiological conditions. The proposed artificial womb can adapt to fetal growth. Volume adjustment is achieved by removing fluid from the interspace between an inner and outer chamber. Results of the in vitro tests showed a temperature constancy of 36.8°C ± 0.3°C without pressure loss over 7 days. The volume of the inner sac was variable between 3.6 and 7.0 L. We designed a filtration and disinfection system for this particular purpose. This system has proven strong disinfection capabilities, effective filtering of metabolic waste, and the ability to avoid phospholipid washout. The presented artificial womb has sufficient volume variability to adapt to the physiologic growth of an extremely preterm neonate over a 4-week period. We regard this as an important step in the development of this bridge-to-life technology.

Toward an Adjustable Blood Pump for Wide-Range Operation: In-Vitro Results of Performance Curve and Hydraulic Efficiency.

Rotary blood pumps in Extracorporeal Life Support (ECLS) applications are optimized for a specific design point. However, in clinical practice, these pumps are usually applied over a wide range of operation points. Studies have shown that a deviation from the design point in a rotary blood pump leads to an unexpected rise of hemolysis with corresponding clinical complications. Adjustable pumps that can adapt geometric parameters to the respective operation point are commonly used in other industrial branches, but yet not applied in blood pumps. We present a novel mechanism to adjust the impeller geometry of a centrifugal blood pump during operation together with in-vitro data of its hydraulic performance and efficiency. Three-dimensionalprinted prototypes of the adjustable impeller and a rigid impeller were manufactured and hydraulic performance and efficiency measured (n = 3). In a flow range of 1.5-9.5 L/min, the adjustable pump increased pump performance up to 47% and hydraulic efficiency by an average of 7.3 percentage points compared with a fixed setting. The adjustable pump allows customization of the pump's behavior (steepness of performance curve) according to individual needs. Furthermore, the hydraulic efficiency of the pump could be maintained at a high level throughout the complete flow range.

Multiphoton Imaging of Maturation in Tissue Engineering.

Donor cell-specific tissue-engineered (TE) implants are a promising therapy for personalized treatment of cardiovascular diseases, but current development protocols lack a stable longitudinal assessment of tissue development at subcellular resolution. As a first step toward such an assessment approach, in this study we establish a generalized labeling and imaging protocol to obtain quantified maturation parameters of TE constructs in three dimensions (3D) without the need of histological slicing, thus leaving the tissue intact. Focusing on intracellular matrix (ICM) and extracellular matrix (ECM) networks, multiphoton laser scanning microscopy (MPLSM) was used to investigate TE patches of different conditioning durations of up to 21 days. We show here that with a straightforward labeling procedure of whole-mount samples (so without slicing into thin histological sections), followed by an easy-to-use multiphoton imaging process, we obtained high-quality images of the tissue in 3D at various time points during development. The stacks of images could then be further analyzed to visualize and quantify the volume of cell coverage as well as the volume fraction and network of structural proteins. We showed that collagen and alpha-smooth muscle actin (α-SMA) volume fractions increased as normalized to full tissue volume and proportional to the cell count, with a converging trend to the final density of (4.0% ± 0.6%) and (7.6% ± 0.7%), respectively. The image analysis of ICM and ECM revealed a developing and widely branched interconnected matrix. We are currently working on the second step, that is, to integrate MPLSM endoscopy into a dynamic bioreactor system to monitor the maturation of intact TE constructs over time, thus without the need to take them out.

Towards Realistic 3D Models of Tumor Vascular Networks.

For reliable in silico or in vitro investigations in, for example, biosensing and drug delivery applications, accurate models of tumor vascular networks down to the capillary size are essential. Compared to images acquired with conventional medical imaging techniques, digitalized histological tumor slices have a higher resolution, enabling the delineation of capillaries. Volume rendering procedures can then be used to generate a 3D model. However, the preparation of such slices leads to misalignments in relative slice orientation between consecutive slices. Thus, image registration algorithms are necessary to re-align the slices. Here, we present an algorithm for the registration and reconstruction of a vascular network from histologic slices applied to 169 tumor slices. The registration includes two steps. First, consecutive images are incrementally pre-aligned using feature- and area-based transformations. Second, using the previous transformations, parallel registration for all images is enabled. Combining intensity- and color-based thresholds along with heuristic analysis, vascular structures are segmented. A 3D interpolation technique is used for volume rendering. This results in a 3D vascular network with approximately 400-450 vessels with diameters down to 25-30 µm. A delineation of vessel structures with close distance was limited in areas of high structural density. Improvement can be achieved by using images with higher resolution and or machine learning techniques.

Vessel Delineation Using U-Net: A Sparse Labeled Deep Learning Approach for Semantic Segmentation of Histological Images.

Semantic segmentation is an important imaging analysis method enabling the identification of tissue structures. Histological image segmentation is particularly challenging, having large structural information while providing only limited training data. Additionally, labeling these structures to generate training data is time consuming. Here, we demonstrate the feasibility of a semantic segmentation using U-Net with a novel sparse labeling technique. The basic U-Net architecture was extended by attention gates, residual and recurrent links, and dropout regularization. To overcome the high class imbalance, which is intrinsic to histological data, under- and oversampling and data augmentation were used. In an ablation study, various architectures were evaluated, and the best performing model was identified. This model contains attention gates, residual links, and a dropout regularization of 0.125. The segmented images show accurate delineations of the vascular structures (with a precision of 0.9088 and an AUC-ROC score of 0.9717), and the segmentation algorithm is robust to images containing staining variations and damaged tissue. These results demonstrate the feasibility of sparse labeling in combination with the modified U-Net architecture.

Novel Size-Variable Dedicated Rodent Oxygenator for ECLS Animal Models-Introduction of the "RatOx" Oxygenator and Preliminary In Vitro Results.

The overall survival rate of extracorporeal life support (ECLS) remains at 60%. Research and development has been slow, in part due to the lack of sophisticated experimental models. This publication introduces a dedicated rodent oxygenator ("RatOx") and presents preliminary in vitro classification tests. The RatOx has an adaptable fiber module size for various rodent models. Gas transfer performances over the fiber module for different blood flows and fiber module sizes were tested according to DIN EN ISO 7199. At the maximum possible amount of effective fiber surface area and a blood flow of 100 mL/min, the oxygenator performance was tested to a maximum of 6.27 mL O2/min and 8.2 mL CO2/min, respectively. The priming volume for the largest fiber module is 5.4 mL, while the smallest possible configuration with a single fiber mat layer has a priming volume of 1.1 mL. The novel RatOx ECLS system has been evaluated in vitro and has demonstrated a high degree of compliance with all pre-defined functional criteria for rodent-sized animal models. We intend for the RatOx to become a standard testing platform for scientific studies on ECLS therapy and technology.

Influence of Aerosolization on Endothelial Cells for Efficient Cell Deposition in Biohybrid and Regenerative Applications.

The endothelialization of gas exchange membranes can increase the hemocompatibility of extracorporeal membrane oxygenators and thus become a long-term lung replacement option. Cell seeding on large or uneven surfaces of oxygenator membranes is challenging, with cell aerosolization being a possible solution. In this study, we evaluated the endothelial cell aerosolization for biohybrid lung application. A Vivostat® system was used for the aerosolization of human umbilical vein endothelial cells with non-sprayed cells serving as a control. The general suitability was evaluated using various flow velocities, substrate distances and cell concentrations. Cells were analyzed for survival, apoptosis and necrosis levels. In addition, aerosolized and non-sprayed cells were cultured either static or under flow conditions in a dynamic microfluidic model. Evaluation included immunocytochemistry and gene expression via quantitative PCR. Cell survival for all tested parameters was higher than 90%. No increase in apoptosis and necrosis levels was seen 24 h after aerosolization. Spraying did not influence the ability of the endothelial cells to form a confluent cell layer and withstand shear stresses in a dynamic microfluidic model. Immunocytochemistry revealed typical expression of CD31 and von Willebrand factor with cobble-stone cell morphology. No change in shear stress-induced factors after aerosolization was reported by quantitative PCR analysis. With this study, we have shown the feasibility of endothelial cell aerosolization with no significant changes in cell behavior. Thus, this technique could be used for efficient the endothelialization of gas exchange membranes in biohybrid lung applications.

Detection of physiological control inputs preload and afterload from intrinsic pump parameters in total artificial heart.

BACKGROUND: In the total artificial heart (TAH), the inputs to the physiological control unit, preload, and afterload, are detected from intrinsic pump parameters (e.g., motor current). Within this study, their detection techniques are developed, and their reliability in pre- and afterload prediction is mapped for a broad range of cardiovascular system states. METHODS: We used ReinHeart TAH which is a fully implantable TAH with a plunger coil drive that is alternately emptying the left and right chambers. From the coil currents we first derived a force generated by the piston with respect to its position and then analyzed its pattern to detect (1) preload-chamber filling, found as piston position at begin ejection and (2) afterload-mean outflow pressures, determined as linearly calibrated average piston force during ejection. TAH is then integrated into a mock loop circulation (MLC) which is set to 135 different steady operating points varying in chamber filling (0%-100%, five steps), mean outflow pressures (system circulation: 60-90-120 mm Hg, pulmonary circulation: 15-30-45 mm Hg), and heart cycle duration (171-600 ms in seven non-equidistant steps). The detected preload and afterload are compared to MLC set values, and the errors are mapped. RESULTS: Respectively for the left and right chambers, the preload was detectable in 134 and 118 operating points and the mean error was ±3% and ±2%. The afterload was detectable in 135 and 87 operating points and the mean error was 37% and 30% respectively for left and right circulation. The operational points that are further away from homeostatic equilibrium values generally yielded larger errors. The largest errors were observed for right circulation at long cycle duration, low afterload, and low filling. CONCLUSIONS: The study yields reliable preload estimation in a broad range of physiological states, particularly for left circulation. Detection of afterload needs further improvements. The study revealed a need for piston movement optimization within the ReinHeart TAH during the early phase of systole.

Two-Photon Endoscopy: State of the Art and Perspectives.

In recent years, the demand for non-destructive deep-tissue imaging modalities has led to interest in multiphoton endoscopy. In contrast to bench top systems, multiphoton endoscopy enables subcellular resolution imaging in areas not reachable before. Several groups have recently presented their development towards the goal of producing user friendly plug and play system, which could be used in biological research and, potentially, clinical applications. We first present the technological challenges, prerequisites, and solutions in two-photon endoscopic systems. Secondly, we focus on the applications already found in literature. These applications mostly serve as a quality check of the built system, but do not answer a specific biomedical research question. Therefore, in the last part, we will describe our vision on the enormous potential applicability of adult two-photon endoscopic systems in biological and clinical research. We will thus bring forward the concept that two-photon endoscopy is a sine qua non in bringing this technique to the forefront in clinical applications.

Development and evaluation of a variable, miniaturized oxygenator for various test methods.

BACKGROUND: Extracorporeal membrane oxygenation (ECMO) became an accepted therapy for the treatment of severe acute respiratory distress syndrome and chronic obstructive pulmonary disease. However, ECMO systems are still prone to thrombus formation and decrease of gas exchange over time. Therefore, it is necessary to conduct qualified studies to identify parameters for optimization of ECMO systems, and especially the oxygenator. However, commercially marketed oxygenators are not always appropriate and available for certain research use cases. Therefore, we aimed to design an oxygenator, which is suitable for various test conditions such as blood tests, numerical simulation, and membrane studies, and can be modified in membrane area size and manufactured in laboratory. METHODS: Main design criteria are a homogeneous blood flow without stagnation zones, low pressure drop, manufacturability in the lab, size variability with one set of housing parts and cost-efficiency. Our newly designed oxygenator was tested comparatively regarding blood cell damage, gas transfer performance and pressure drop to prove the validity of the design in accordance with a commercial device. RESULTS: No statistically significant difference between the tested oxygenators was detected and our new oxygenator demonstrated sufficient hemocompatibility. Furthermore, our variable oxygenator has proven that it can be easily manufactured in the laboratory, allows to use various membrane fiber configurations and can be reopened easily and non-destructively for analysis after use, and the original geometry is available for numerical simulations. CONCLUSION: Therefore, we consider this newly developed device as a valuable tool for basic experimental and numerical research on the optimization of oxygenators.

Towards technically controlled bioreactor maturation of tissue-engineered heart valves.

Bioreactors are important tools for the pre-conditioning of tissue-engineered heart valves. The current state of the art mostly provides for timed, physical and biochemical stimulation in the bioreactor systems according to standard protocols (SOP). However, this does not meet to the individual biological variability of living tissue-engineered constructs. To achieve this, it is necessary to implement (i) sensory systems that detect the actual status of the implant and (ii) controllable bioreactor systems that allow patient-individualized pre-conditioning. During the maturation process, a pulsatile transvalvular flow of culture medium is generated within the bioreactor. For the improvement of this conditioning procedure, the relationship between the mechanical and biochemical stimuli and the corresponding tissue response has to be analyzed by performing reproducible and comparable experiments. In this work, a technological framework for maturation experiments of tissue-engineered heart valves in a pulsating bioreactor is introduced. The aim is the development of a bioreactor system that allows for continuous control and documentation of the conditioning process to increase reproducibility and comparability of experiments. This includes hardware components, a communication structure and software including online user communication and supervision. Preliminary experiments were performed with a tissue-engineered heart valve to evaluate the function of the new system. The results of the experiment proof the adequacy of the setup. Consequently, the concept is an important step for further research towards controlled maturation of tissue-engineered heart valves. The integration of molecular and histological sensor systems will be the next important step towards a fully automated, self-controlled preconditioning system.

In vitro thrombogenicity evaluation of rotary blood pumps by thromboelastometry.

In vitro thrombogenicity tests for rotary blood pumps (RBPs) could benefit from assessing coagulation kinematics, as RBP design improves. In this feasibility study, we investigated if the method of thromboelastometry (TEM) is able to assess coagulation kinematics under the in vitro conditions of RBP tests. We conducted in vitro thrombogenicity tests (n=4) by placing Deltastream® DP3 pumps into test loops that were filled with 150 mL of slightly anti-coagulated porcine blood, adjusted to an activated clotting time (ACT) well below clinically recommended levels. Blood samples were taken at certain time points during the experiment until a continuous decrease in pump flow indicated major thrombus formation. Blood samples were analyzed for ACT, platelet count (PLT), and several TEM parameters. While visible thrombus formation was observed in three pumps, ACT indicated an ongoing activation of coagulation, PLT might have indicated platelet consumption. Unexpectedly, most TEM results gave no clear indications. Nonetheless, TEM clotting time obtained by non-anticoagulated and chemically non-activated whole blood (HEPNATEM-CT) appeared to be more sensitive for the activation of coagulation in vitro than ACT, which might be of interest for future pump tests. However, more research regarding standardization of thrombogenicity pump tests is urgently required.

Bone Marrow Derived Mesenchymal Stromal Cells Promote Vascularization and Ciliation in Airway Mucosa Tri-Culture Models in Vitro.

Patients suffering from irresectable tracheal stenosis often face limited treatment options associated with low quality of life. To date, an optimal tracheal replacement strategy does not exist. A tissue-engineered tracheal substitute promises to overcome limitations such as implant vascularization, functional mucociliary clearance and mechanical stability. In order to advance a tracheal mucosa model recently developed by our group, we examined different supporting cell types in fibrin-based tri-culture with primary human umbilical vein endothelial cells (HUVEC) and primary human respiratory epithelial cells (HRE). Bone marrow-derived mesenchymal stromal cells (BM-MSC), adipose-derived mesenchymal stromal cells (ASC) and human nasal fibroblasts (HNF) were compared regarding their ability to promote mucociliary differentiation and vascularization in vitro. Three-dimensional co-cultures of the supporting cell types with either HRE or HUVEC were used as controls. Mucociliary differentiation and formation of vascular-like structures were analyzed by scanning electron microscopy (SEM), periodic acid Schiff's reaction (PAS reaction), two-photon laser scanning microscopy (TPLSM) and immunohistochemistry. Cytokine levels of vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), interleukin-6 (IL6), interleukin-8 (IL8), angiopoietin 1, angiopoietin 2, fibroblast growth factor basic (FGF-b) and placenta growth factor (PIGF) in media supernatant were investigated using LEGENDplex™ bead-based immunoassay. Epithelial morphology of tri-cultures with BM-MSC most closely resembled native respiratory epithelium with respect to ciliation, mucus production as well as expression and localization of epithelial cell markers pan-cytokeratin, claudin-1, α-tubulin and mucin5AC. This was followed by tri-cultures with HNF, while ASC-supported tri-cultures lacked mucociliary differentiation. For all supporting cell types, a reduced ciliation was observed in tri-cultures compared to the corresponding co-cultures. Although formation of vascular-like structures was confirmed in all cultures, vascular networks in BM-MSC-tri-cultures were found to be more branched and extended. Concentrations of pro-angiogenic and inflammatory cytokines, in particular VEGF and angiopoietin 2, revealed to be reduced in tri-cultures compared to co-cultures. With these results, our study provides an important step towards a vascularized and ciliated tissue-engineered tracheal replacement. Additionally, our tri-culture model may in the future contribute to an improved understanding of cell-cell interactions in diseases associated with impaired mucosal function.

TPMS-based membrane lung with locally-modified permeabilities for optimal flow distribution.

Membrane lungs consist of thousands of hollow fiber membranes packed together as a bundle. The devices often suffer from complications because of non-uniform flow through the membrane bundle, including regions of both excessively high flow and stagnant flow. Here, we present a proof-of-concept design for a membrane lung containing a membrane module based on triply periodic minimal surfaces (TPMS). By warping the original TPMS geometries, the local permeability within any region of the module could be raised or lowered, allowing for the tailoring of the blood flow distribution through the device. By creating an iterative optimization scheme for determining the distribution of streamwise permeability inside a computational porous domain, the desired form of a lattice of TPMS elements was determined via simulation. This desired form was translated into a computer-aided design (CAD) model for a prototype device. The device was then produced via additive manufacturing in order to test the novel design against an industry-standard predicate device. Flow distribution was verifiably homogenized and residence time reduced, promising a more efficient performance and increased resistance to thrombosis. This work shows the promising extent to which TPMS can serve as a new building block for exchange processes in medical devices.

In Vitro and In Vivo Feasibility Study for a Portable VV-ECMO and ECCO2R System.

Extracorporeal membrane oxygenation (ECMO) is an established rescue therapy for patients with chronic respiratory failure waiting for lung transplantation (LTx). The therapy inherent immobilization may result in fatigue, consecutive deteriorated prognosis, and even lost eligibility for transplantation. We conducted a feasibility study on a novel system designed for the deployment of a portable ECMO device, enabling the physical exercise of awake patients prior to LTx. The system comprises a novel oxygenator with a directly connected blood pump, a double-lumen cannula, gas blender and supply, as well as control and energy management. In vitro experiments included tests regarding performance, efficiency, and blood damage. A reduced system was tested in vivo for feasibility using a novel large animal model. Six anesthetized pigs were first positioned in supine position, followed by a 45° angle, simulating an upright position of the patients. We monitored performance and vital parameters. All in vitro experiments showed good performance for the respective subsystems and the integrated system. The acute in vivo trials of 8 h duration confirmed the results. The novel portable ECMO-system enables adequate oxygenation and decarboxylation sufficient for, e.g., the physical exercise of designated LTx-recipients. These results are promising and suggest further preclinical studies on safety and efficacy to facilitate translation into clinical application.

An accelerometer-based guidance device for CT-guided procedures: an improved wireless prototype.

INTRODUCTION: The aim of the study was to demonstrate the feasibility of a prototype for accelerometer-based guidance for percutaneous CT-guided punctures and compare it with free-hand punctures. MATERIAL AND METHODS: The prototype enabled alignment with the CT coordinate system and a wireless connectivity. Its feasibility was tested in a swine cadaver model: 20 out-of-plane device-assisted punctures performed without intermittent control scans (one-step punctures) were evaluated regarding deviation to target and difference between planned and obtained angle. Thereafter, 22 device-assisted punctures were compared with 20 free-hand punctures regarding distance to target, deviation from the planned angle, number of control scans and procedure time. Differences were compared with the Mann-Whitney U-test (p < .05). RESULTS: The one-step punctures revealed a deviation to target of 0.26 ± 0.37 cm (axial plane) and 0.21 ± 0.19 cm (sagittal plane) and differences between planned and performed puncture angles of 0.9 ± 1.09° (axial plane) and 1.15 ± 0.91° (sagittal planes). In the comparative study, device-assisted punctures showed a significantly higher accuracy, 0.20 ± 0.17 cm vs. 0.30 ± 0.21 cm (p < .05) and lower number of required control scans, 1.3 ± 1.1 vs. 3.7 ± 0.9 (p < .05) compared with free-hand punctures. CONCLUSION: The accelerometer-based device proved to be feasible and demonstrated significantly higher accuracy and required significantly less control scans compared to free-hand puncture.

Comparison of Aspiration Catheters with Modified Standard Catheters for Treatment of Large Pulmonary Embolism Using an In-vitro Patho-Physiological Model.

PURPOSE: The presented in-vitro study provides a comparison of various catheters for mechanical treatment of large-burden pulmonary embolism (PE) under standardized conditions, using a new test rig. Dedicated aspiration catheters (JETi®, Penumbra Indigo®, Aspirex®) were compared with standard catheters (Pigtail, Multi-Purpose, Balloon Catheter) applied for embolus fragmentation. MATERIALS AND METHODS: Emboli prepared from porcine blood were washed into the test rig which consists of anatomical models of the pulmonary artery (PA) and of the right heart in combination with a pulsatile drive system. For all catheters, the duration of the recanalization procedure and the weight percentage (wt%) of the remaining, removed and washed-down clot fractions were evaluated. For aspiration catheters, the aspirated volume was measured. RESULTS: All catheters achieved full or partial recanalization. The aspiration catheters showed a significantly (p < 0.05) lower procedure time (3:15 min ± 4:26 min) than the standard fragmentation catheters (7:19 min ± 4:40 min). The amount of thrombus removed by aspiration was significantly (p < 0.001) higher than that by fragmentation, averaging 86.1 wt% ± 15.6 wt% and 31.7 wt% ± 3.8 wt%, respectively. Nonetheless, most of the residue was fragmented into pieces of ≥ 1 mm and washed down. Only in 2 of 36 tests, a residual thrombus of 11.9 wt% ± 5.1 wt% remained in the central PA. CONCLUSION: Comparison under standardized in-vitro patho-physiological conditions showed that embolus fragmentation with standard catheters is clearly inferior to aspiration with dedicated catheters in the treatment of large-burden PE, but can still achieve considerable success. LEVEL OF EVIDENCE: No level of evidence, experimental study.

Three-dimensional membranes for artificial lungs: Comparison of flow-induced hemolysis.

BACKGROUND: Membranes based on triply periodic minimal surfaces (TPMS) have proven a superior gas transfer compared to the contemporary hollow fiber membrane (HFM) design in artificial lungs. The improved oxygen transfer is attributed to disrupting the laminar boundary layer adjacent to the membrane surface known as main limiting factor to mass transport. However, it requires experimental proof that this improvement is not at the expense of greater damage to the blood. Hence, the aim of this work is a valid statement regarding the structure-dependent hemolytic behavior of TPMS structures compared to the current HFM design. METHODS: Hemolysis tests were performed on structure samples of three different kind of TPMS-based designs (Schwarz-P, Schwarz-D and Schoen's Gyroid) in direct comparison to a hollow fiber structure as reference. RESULTS: The results of this study suggest that the difference in hemolysis between TPMS membranes compared to HFMs is small although slightly increased for the TPMS membranes. There is no significant difference between the TPMS structures and the hollow fiber design. Nevertheless, the ratio between the achieved additional oxygen transfer and the additional hemolysis favors the TPMS-based membrane shapes. CONCLUSION: TPMS-shaped membranes offer a safe way to improve gas transfer in artificial lungs.

In-Vitro Visualization of Thrombus Growth in Artificial Lungs Using Real-Time X-Ray Imaging: A Feasibility Study.

PURPOSE: Extracorporeal membrane oxygenation has gained increasing attention in the treatment of patients with acute and chronic cardiopulmonary and respiratory failure. However, clotting within the oxygenators or other components of the extracorporeal circuit remains a major complication that necessitates at least a device exchange and bears risks of adverse events for the patients. In order to better predict thrombus growth within oxygenators, we present an approach for in-vitro visualization of thrombus growth using real-time X-ray imaging. METHODS: An in-vitro test setup was developed using low-dose anticoagulated ovine blood and allowing for thrombus growth within 4 h. The setup was installed in a custom-made X-ray setup that uses phase-contrast for imaging, thus providing enhanced soft-tissue contrast, which improves the differentiation between blood and potential thrombus growth. During experimentation, blood samples were drawn for the analysis of blood count, activated partial thromboplastin time and activated clotting time. Additionally, pressure and flow data was monitored and a full 360° X-ray scan was performed every 15 min. RESULTS: Thrombus formation indicated by a pressure drop and changing blood parameters was monitored in all three test devices. Red and white thrombi (higher/lower attenuation, respectively) were successfully segmented in one set of X-ray images. CONCLUSION: We showed the feasibility of a new in-vitro method for real-time thrombus growth visualization by means of phase contrast X-ray imaging. In addition, with more blood parameters that are clinically relevant, this approach might contribute to improved oxygenator exchange protocols in the clinical routine.

In-vitro performance of a single-chambered total artificial heart in a Fontan circulation.

An in-vitro study was conducted to investigate the general feasibility of using only one pumping chamber of the SynCardia total artificial heart (TAH) as a replacement of the single ventricle palliated by Fontan circulation. A mock circulation loop was used to mimic a Fontan circulation. The combination of both ventricle sizes (50 and 70 cc) and driver (Freedom Driver and Companion C2 Driver) was investigated. Two clinical relevant scenarios (early Fontan; late Fontan) as derived from literature data were set up in the mock loop. The impact of increased transpulmonary pressure gradient, low atrial pressure, and raised central venous pressure on cardiac output was studied. From a hemodynamic point, the single-chambered TAH performed sufficiently in the setting of the Fontan circulation. Increased transpulmonary pressure gradient, from ideal to pulmonary hypertension, decreased the blood flow in combinations by almost 2 L/min. In the early Fontan scenario, a cardiac output of 3-3.5 L/min was achieved using the 50 cc ventricle, driven by the Companion C2 Driver. Even under pulmonary hypertension, cardiac outputs greater than 4 L/min could be obtained with the 70 cc pump chamber in the late Fontan scenario. In the clinically relevant Fontan scenarios, implementation of the single chambered TAH performed successfully from a hemodynamic point of view. The replacement of the failing univentricular heart by a single chamber of the SynCardia TAH may provide an alternative to a complex biventricular repair procedure or ventricular support in Fontan patients.