Ein implantierbares Telemetriesystem zur Impedanzspektroskopie

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Die kontinuierliche Überwachung des intrakorporalen Zustandes von Geweben beispielsweise zur Erkennung ischämischer Vorgänge nach gefäßchirurgischen Eingriffen oder im Rahmen der Rejektionsdiagnostik läßt sich durch bisher vorhandene Meßsysteme nur bedingt erreichen. Speziell die direkte Erfassung sensitiver Gewebeparameter über einen längeren Zeitraum ohne Belastung für den Patienten stellt in diesem Zusammenhang ein Problem dar. In der nachfolgenden Arbeit wird das Konzept eines implantierbaren Telemetriesystems vorgestellt, das die Bewertung des Gewebezustandes über die Messung der frequenzabhängigen Bioimpedanz ermöglicht. Besondere Beachtung wird der Auslegung und Umsetzung der einzelnen Systemkomponenten sowie der Vorstellung erster in vitro Messungen zur Evaluierung des Meßsystems geschenkt

Search for charged Higgs bosons decaying to top and bottom quarks in ppbar collisions

We describe a search for production of a charged Higgs boson, q \bar{q'} -> H^+, reconstructed in the t\bar{b} final state in the mass range 180 <= M_{H^+} <= 300 GeV. The search was undertaken at the Fermilab Tevatron collider with a center-of-mass energy sqrt{s} = 1.96 TeV and uses 0.9 fb^{-1} of data collected with the D0 detector. We find no evidence for charged Higgs boson production and set upper limits on the production cross section in the Types I, II and III two-Higgs-doublet models (2HDMs). An excluded region in the (M_{H^+},tan\beta) plane for Type I 2HDM is presented.Comment: Submitted to Phys. Rev. Letter

Ventricular Flow Field Visualization During Mechanical Circulatory Support in the Assisted Isolated Beating Heart

Investigations of ventricular flow patterns during mechanical circulatory support are limited to in vitro flow models or in silico simulations, which cannot fully replicate the complex anatomy and contraction of the heart. Therefore, the feasibility of using echocardiographic particle image velocimetry (Echo-PIV) was evaluated in an isolated working heart setup. Porcine hearts were connected to an isolated, working heart setup and a left ventricular assist device (LVAD) was implanted. During different levels of LVAD support (unsupported, partial support, full support), microbubbles were injected and echocardiographic images were acquired. Iterative PIV algorithms were applied to calculate flow fields. The isolated heart setup allowed different hemodynamic situations. In the unsupported heart, diastolic intra-ventricular blood flow was redirected at the heart's apex towards the left ventricular outflow tract (LVOT). With increasing pump speed, large vortex formation was suppressed, and blood flow from the mitral valve directly entered the pump cannula. The maximum velocities in the LVOT were significantly reduced with increasing support. For the first time, cardiac blood flow patterns during LVAD support were visualized and quantified in an ex vivo model using Echo-PIV. The results reveal potential regions of stagnation in the LVOT and, in future the methods might be also used in clinical routine to evaluate intraventricular flow fields during LVAD support

A Cavopulmonary Assist Device for Long-Term Therapy of Fontan Patients

Treatment of univentricular hearts remains restricted to palliative surgical corrections (Fontan pathway). The established Fontan circulation lacks a subpulmonary pressure source and is commonly accompanied by progressively declining hemodynamics. A novel cavopulmonary assist device (CPAD) may hold the potential for improved therapeutic management of Fontan patients by chronic restoration of biventricular equivalency. This study aimed at translating clinical objectives toward a functional CPAD with preclinical proof regarding hydraulic performance, hemocompatibility and electric power consumption. A prototype composed of hemocompatible titanium components, ceramic bearings, electric motors, and corresponding drive unit was manufactured for preclinical benchtop analysis: hydraulic performance in general and hemocompatibility characteristics in particular were analyzed in-silico (computational fluid dynamics) and validated in-vitro. The CPAD's power consumption was recorded across the entire operational range. The CPAD delivered pressure step-ups across a comprehensive operational range (0–10 L/min, 0–50 mm Hg) with electric power consumption below 1.5 W within the main operating range. In-vitro hemolysis experiments (N = 3) indicated a normalized index of hemolysis of 3.8 ± 1.6 mg/100 L during design point operation (2500 rpm, 4 L/min). Preclinical investigations revealed the CPAD's potential for low traumatic and thrombogenic support of a heterogeneous Fontan population (pediatric and adult) with potentially accompanying secondary disorders (e.g., elevated pulmonary vascular resistance or systemic ventricular insufficiency) at distinct physical activities. The low power consumption implied adequate settings for a small, fully implantable system with transcutaneous energy transfer. The successful preclinical proof provides the rationale for acute and chronic in-vivo trials aiming at the confirmation of laboratory findings and verification of hemodynamic benefit.ISSN:1043-0679ISSN:1876-466