79 research outputs found
Einfluss klebstoffspezifischer Eigenspannungs- und Schädigungszustände auf das Festigkeits- und Beständigkeitsverhalten von Metallklebverbindungen
von Christian SchäfersPaderborn, Univ., Diss., 200
The Ross procedure versus repair for treatment of a unicuspid aortic valve in adults
OBJECTIVES
Aortic stenosis or regurgitation in patients with a unicuspid valve morphology requires interventions early in life. We have performed either primary valve repair or the Ross procedure. The goal of this study was to compare the midterm results of repair and pulmonary autograft replacement.
METHODS
Between December 1998 and April 2022, a total of 345 patients (77% male; mean age 34 ± 9.7 years) underwent treatment of a unicuspid aortic valve. Patients were excluded if they were 54 years (n = 3) at the time of the operation. The remaining cohort was divided into 2 groups: 167 (64%) patients underwent valve repair; 91 (36%) patients underwent pulmonary autograft replacement.
The indications for surgery were aortic regurgitation (n = 104), aortic stenosis (n = 45), combined disease (n = 103) and endocarditis (n = 6). Fifty-one patients had root dilatation (>43 mm) with aortic regurgitation (repair n = 23; Ross n = 28). Mean follow-up was 5.9 years (SD: 5 years) [range 0.1–22.3 years].
RESULTS
There were 1 early and 3 late deaths; 47 patients required reintervention. Survival at 10 years was 95% in the Ross group and 97% after valve repair (P = 0.769). Freedom from reintervention at 10 years was 98% in the Ross group and 80% after valve repair (P = 0.012). A receiver operating characteristics curve analysis showed a trend towards better durability in patients < 26 years.
CONCLUSIONS
The ideal treatment of the unicuspid aortic valve remains debatable. Repair of a unicuspid valve can be considered a bridge to pulmonary autograft replacement, at least in younger patients. The appropriate times to replace and to repair require further investigation
Which Aortic Valve Can Be Surgically Reconstructed?
Purpose of Review
Preservation or repair of the aortic valve has evolved dynamically in the past 20 years. It leads to a high freedom from valve-related complications if an adequate valve durability can be achieved; it may possibly also improve survival. To date, little structured information is available about which valves can be repaired and which should better be replaced.
Recent Findings
For surgical decision-making, the size of the aortic root is important and the anatomy of the aortic valve must be considered. In the presence of root aneurysm, most tricuspid and bicuspid aortic valves can be preserved. In aortic regurgitation and normal aortic dimensions, the majority of tricuspid and bicuspid aortic valves can be repaired with good long-term durability. In bicuspid aortic valves, the morphologic characteristics must be taken into consideration. Unicuspid and quadricuspid aortic valves can be repaired in selected cases. Generally, cusp calcification is a sign of a poor substrate for repair; the same is true for cusp retraction and cusp destruction due to active endocarditis. They are associated with limited valve durability.
Summary
Using current concepts, many non-calcified aortic valves can be repaired. Modern imaging, in particular three-dimensional transesophageal echocardiography (TEE), should be able to define repairable aortic valves with a high probability
Suppression of electrical breakdown phenomena in liquid TriMethyl Bismuth based ionization detectors
Organometallic liquids provide good properties for ionization detectors.
TriMethyl Bismuth (TMBi) has been proposed as a detector medium with charge and
Cherenkov photon readout for Positron Emission Tomography. In this work, we
present studies for the handling of TMBi at different electric fields and under
different environmental conditions to find applicable configurations for the
suppression of electrical breakdowns in TMBi at room temperature. A simple
glass cell with two electrodes filled with TMBi was constructed and tested
under different operation conditions. Working at the vapour pressure of TMBi at
room temperature of about 40 mbar and electric fields of up to 20 kV/cm in
presence of a small oxygen contamination we found the formation of a discharge
channel in the liquid and a steady increase in the current. Further reduction
of pressure by pumping caused the TMBi to boil and a spontaneous combustion.
Eliminating the oxygen contamination led the TMBi under the same condition to
only decompose. When operating the setup under an argon atmosphere of 1 bar we
did not observe breakdowns of the electrical potential up to field strengths of
20 kV/cm. Still, in presence of a small oxygen contamination fluctuating
currents in the nA range were observed, but no decomposition or combustion. We
conclude from our experiments that TMBi at room temperature in a pure argon
atmosphere of 1 bar remains stable against electrical breakdown at least up to
electric field strengths of 20 kV/cm, presumably because the formation of
gaseous TMBi was prevented.Comment: 14 page, 8 figure
Late-Onset Prosthetic Endocarditis with Paraaortic Abscess Caused by Cutibacterium acnes
Cutibacterium acnes, an integral component of the skin’s customary bacterial flora, represents
a Gram-positive anaerobic bacterium characterized by its low virulence. Despite its low virulence,
the pathogen can cause profound-seated infections as well as infections linked to medical devices.
We report a case study of a prosthesis endocarditis accompanied by a paraaortic abscess caused by
C. acnes, a development occurring five years prior to composite aortic root and valve replacement. At
the point of admission, the patient presented with a combination of symptoms hinting at a subacute
progression, such as weight loss, chest pain, and limitations of cardiopulmonary functionality. An
anaerobic pathogen, namely C. acnes, was detected in a singular blood culture vial. Since first-line
imaging modalities such as echocardiography did not reveal any signs of inflammation, and in the
case of a suspected diagnosis for IE, did not show high pretest probability, further diagnostic imaging
such as 18F-FDG PET CT was put to use. Here, a highly elevated glucose metabolism around the
aortic valve ring was detected, pointing to an inflammatory process. The patient received adjusted
intravenous antibiotic therapy over a course of six weeks; he then underwent surgical therapy via
re-replacement of the aortic root and valve using a composite conduit. Advanced microbiological
analyses, including the amplification of PCR and valve sequencing via 16S rDNA, mainly detected
one pathogen: C. acnes. Delayed onset with mild symptoms and laboratory findings is characteristic
of infective endocarditis by C. acnes. Due to its high rate of complications, mortality, and morbidity,
an infection should not be disregarded as contamination. Recommendations from different studies
underline a combination of a positive blood culture and microbiological evidence to differentiate
between contamination and true infection in the case of an infection involving C. acnes. Serial blood
cultures with prolonged incubation, advanced microbiological analyses, and modified Duke criteria
including second-line imaging techniques should be utilized for further evaluation
Seebeck Effect in Magnetic Tunnel Junctions
Creating temperature gradients in magnetic nanostructures has resulted in a
new research direction, i.e., the combination of magneto- and thermoelectric
effects. Here, we demonstrate the observation of one important effect of this
class: the magneto-Seebeck effect. It is observed when a magnetic configuration
changes the charge based Seebeck coefficient. In particular, the Seebeck
coefficient changes during the transition from a parallel to an antiparallel
magnetic configuration in a tunnel junction. In that respect, it is the analog
to the tunneling magnetoresistance. The Seebeck coefficients in parallel and
antiparallel configuration are in the order of the voltages known from the
charge-Seebeck effect. The size and sign of the effect can be controlled by the
composition of the electrodes' atomic layers adjacent to the barrier and the
temperature. Experimentally, we realized 8.8 % magneto-Seebeck effect, which
results from a voltage change of about -8.7 {\mu}V/K from the antiparallel to
the parallel direction close to the predicted value of -12.1 {\mu}V/K.Comment: 16 pages, 7 figures, 2 table
Differential expression of microRNAs following cardiopulmonary bypass in children with congenital heart diseases
Background: Children with congenital heart defects (CHDs) are at high risk for myocardial failure after operative
procedures with cardiopulmonary bypass (CPB). Recent studies suggest that microRNAs (miRNA) are involved in the
development of CHDs and myocardial failure. Therefore, the aim of this study was to determine alterations in the
miRNA profle in heart tissue after cardiac surgery using CPB.
Methods: In total, 14 tissue samples from right atrium were collected from patients before and after connection of
the CPB. SurePrint™ 8 × 60K Human v21 miRNA array and quantitative reverse transcription-polymerase chain reac‑
tion (RT-qPCR) were employed to determine the miRNA expression profle from three patients before and after con‑
nection of the CPB. Enrichment analyses of altered miRNA expression were predicted using bioinformatic tools.
Results: According to miRNA array, a total of 90 miRNAs were signifcantly altered including 29 miRNAs with
increased and 61 miRNAs with decreased expression after de-connection of CPB (n = 3) compared to before CPB
(n = 3). Seven miRNAs had been validated using RT-qPCR in an independent cohort of 11 patients. Enrichment
analyses applying the KEGG database displayed the highest correlation for signaling pathways, cellular community,
cardiovascular disease and circulatory system.
Conclusion: Our result identifed the overall changes of the miRNome in right atrium tissue of patients with CHDs
after CPB. The diferentially altered miRNAs lay a good foundation for further understanding of the molecular function
of changed miRNAs in regulating CHDs and after CPB in particula
Thymidine Metabolism as Confounding Factor of 3'-Deoxy-3'-[18F]Fluorothymidine Uptake after Therapy in a Colorectal Cancer Model.
Non-invasive monitoring of tumor therapy response helps in developing personalized treatment strategies. Here, we performed sequential positron emission tomography (PET) and diffusion-weighted magnetic resonance imaging (DW-MRI) to evaluate changes induced by a FOLFOX-like combination chemotherapy in colorectal cancer (CRC) xenografts, to identify the cellular and molecular determinants of these imaging biomarkers. Methods: Tumor bearing CD1 nude mice, engrafted with FOLFOX-sensitive Colo205 CRC xenografts, were treated with FOLFOX (5 fluorouracil, leucovorin and oxaliplatin) in weekly intervals. On d1, d2, d6, d9 and d13 of therapy, tumors were assessed by in vivo imaging and ex vivo analyses. In addition, HCT116 xenografts, which did not respond to the FOLFOX treatment, were imaged on d1 of therapy. Results: In Colo205 xenografts, FOLFOX induced a profound increase in uptake of the proliferation PET tracer 3'-deoxy-3'-[18F]fluorothymidine ([18F]FLT), which was accompanied by increases in markers for proliferation (Ki67, TK1) and for activated DNA damage response (DDR; ÎłH2AX), whereas the effect on cell death was minimal. As tracer uptake was unaltered in the HCT116 model, these changes appear to be specific for tumor response. Conclusion: We demonstrate that [18F]FLT PET can non-invasively monitor molecular alterations induced by a cancer treatment, including thymidine metabolism and DDR. The cellular or imaging changes may not, however, be directly related to therapy response as assessed by volumetric measurements
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