Hemodynamical Evaluation of a New Surgically Implanted Pulsatile Right Ventricular Assist Device Driven by a Conventional Intra-Aortic Balloon Pump Console.

Severe right heart failure, often overlooked and challenging to manage, has prompted a growing interest in innovative approaches to provide functional support. This study uses experimentation in large porcine models to introduce a novel prototype of a pulsatile mechanical circulatory support device and document its effects when deployed as a right ventricular assist device (RVAD). The pulsatile ventricular assist platform (pVAP), featuring a membrane pump driven by an intra-aortic balloon pump console, actively generates pulsatile flow to propel right ventricular blood into the pulmonary artery. This novel prototype demonstrates promising potential in addressing the challenges of right heart failure management. After preliminary in vitro assessments, the pVAP was tested on seven porcine models in a healthy state and after the induction of right ventricular failure. During the procedure, a set of standard (ie, standard-of-care) hemodynamic measurements was obtained. Additionally, invasive pressure-volume loop analysis was employed to examine left ventricular hemodynamics. Results indicated that activation of the pVAP during right ventricular failure significantly improved systemic hemodynamics and enhanced left ventricular function. This study sheds light on the potential of the pVAP in managing right heart failure.

Mueller Matrix Analysis of Collagen and Gelatin Containing Samples Towards More Objective Skin Tissue Diagnostics.

Electrospun polycaprolactone:gelatin (PCL:GT) fibre scaffolds are widely employed in the field of tissue implants. Here, the orientation of fibres plays an important role in regard to implantation due to the impact on the mechanical properties. Likewise, the orientation of collagen fibres in skin tissue is relevant for dermatology. State-of-the-art fibre orientation measurement methods like electron microscopy are time consuming and destructive. In this work, we demonstrate polarimetry as a non-invasive approach and evaluate its potential by measuring the Mueller matrix (MM) of gelatin and collagen containing samples as simple skin tissue phantoms. We demonstrate that it is possible to determine the orientation of PCL:GT fibre scaffolds within one MM measurement. Furthermore, we determine the structural orientation in collagen film samples. Currently, the diagnosis of skin diseases is often performed by image analysis or histopathology respectively, which are either subjective or invasive. The method presented, here, provides an interesting alternative approach for such investigations. Our findings indicate that the orientation of collagen fibres within skin lesions might be detectable by MM measurements in the future, which is of interest for skin diagnostics, and will be further investigated during the next step.

An acoustic method for systematic ventricular assist device thrombus evaluation with a novel artificial thrombus model.

BACKGROUND: Pump thrombosis (PT) is still one of the major adverse events in patients supported with left ventricular assist devices. Nowadays, thrombus detection relies on clinical parameters like reoccurring heart failure symptoms, on changes in pump power consumption, and on laboratory parameters such as increased LDH and hemolysis. Once detected PT is most often persistent and refractory to medical therapy. We therefore designed a novel, non-invasive acoustic method for early pump thrombus detection in an in vitro artificial thrombus model. METHODS: The study was performed in vitro using a mock circulation loop, artificial blood (water-glycerin) and artificial thrombus material (silicon) allowing for repeatable and defined testing. Tested ventricular assist device (VAD) type was HVAD (Medtronic). Three different thrombus locations were evaluated: on the tilted pad of the rotor, in the primary flow path, and in the secondary flow path beneath the rotor. After evaluating baseline parameters (no thrombus, n=20 for each pump), the influence of thrombi of seven different masses (no thrombus, 0.5-5.0 mg) on pump power consumption and acoustic emission of four HVAD devices was investigated via a microphone system (Sennheiser) and subsequent frequency spectrum analysis (n=12). The acoustic analysis algorithm included the number of frequency peaks recorded. RESULTS: Measurements with thrombi on the tilted pad showed an increased number of frequency peaks with all thrombus sizes compared to baseline measurements without any thrombus (baseline: 32.7±7.4; 0.5 mg: 45.3±10.4 up to 5 mg: 80.4±5.5). Power consumption was relevantly elevated in 5mg thrombus measurement only (6.3±1.29 W compared to 4.9±0.14 W at baseline). Measurements with thrombi in the primary and secondary showed no relevant alteration in power consumption and frequency peak count. CONCLUSIONS: We present an acoustic method that detects pump thrombi located on the tilted pad of the HVAD rotor requiring ten times less mass compared to thrombi detected by power consumption alterations used in current detection algorithms. Assuming that pump thrombi are growing over several days, the presented method may detect PT much earlier thereby increasing efficacy of medical therapy and helping to avoid pump exchange.

Comparison between three in vitro methods to measure magnesium degradation and their suitability for predicting in vivo degradation.

A lot of research has been done in the field of magnesium-based implant material. This study is focused on finding an explanation for the large disparity in results from similar experiments in literature. The hypothesis is that many different measurement protocols are used to quantify magnesium degradation and this leads to inconsistent results. Cylindrical, pure magnesium samples were used for this study. The degradation took place in revised simulated body fluid at 37°C. Hydrogen evolution was measured to quantify the degradation. Two commonly used experimental protocols were examined: static conditions and a fluid changing method. For static testing, the samples stayed in fluid. For the fluid changing method, the fluid was changed after 2 and 5 days of immersion. In addition, a new method with continuous fluid flow was established. After an initial phase, the results confirm that for all three methods, the degradation behavior differs strongly. The static condition results in a very slow degradation rate. The fluid change method leads to a similar behavior like the static condition except that the degradation was speeded up after the fluid changes. The continuous degradation is linear for a long period after the initial phase. In comparison with in vivo degradation behavior, the degradation process in continuous flow shows the best fitting. The accumulation of degradation products, especially the increasing pH value, has a strong inhibiting effect. This cannot be observed in vivo so that a constant experimental environment realizable by continuous flow is more suitable for magnesium-based implant material testing.