Prosthetic valves in the pulmonary position

In this thesis the prosthetic heart valve in the pulmonary position has been analyzed. The results in this thesis demonstrate that there is a need for a suitable valve for the pulmonary position, tailored to the physiological circumstances of the right ventricle and the young age of this population. Currently available valve types each have its own limitation that tend to be more prone in the pulmonary position. We have demonstrated that a mechanical prosthetic valve can be a suitable option for pulmonary valve replacement. furthermore, we have demonstrated that the hemodynamic conditions in which the valve is placed influence the functionality of valve. Our results showed that the quality of life of congenital heart disease patients with a prosthetic valve is comparable to the general population. Overall, we can conclude that the use of prosthetic valves in the pulmonary valve is suboptimal, while life expectancy increases and in particular the Quality of Life of patients with a pulmonary prosthetic valve does not seem to be affected

Pulmonary versus aortic pressure behavior of a bovine pericardial valve

Background: The Carpentier Edwards Perimount Magna Ease aortic valvular prosthesis (Edwards Lifesciences, Irvine, Calif) has been among the most frequently and successfully used tissue prosthetic cardiac valves. Furthermore, this prosthesis has been used off-label in the pulmonary position. Until now, there has been a paucity of data regarding the functioning of tissue prosthetic valves under pulmonary conditions. Methods: Using a pulse duplicator, hydrodynamic characteristics of a 21-mm and 25-mm Magna Ease valve were evaluated. Among parameters evaluated were leakage orifice area, closing time (ie, time required to close), and leakage duration. This procedure was performed under different pulmonic pressure conditions (15/5 mm Hg, 28/11 mm Hg, 73/32 mm Hg) and normal aortic pressure (120/80 mm Hg) as a reference. Moving images were obtained using a Phantom MIRO M320S high-speed camera (Vision Research Inc, Wayne, NJ) at 600 frames per second and used to analyze valve area in closed position. Results: Under normal pulmonic conditions (28/11 mm Hg) the leakage orifice area was 0.020 ± 0.012 mm2 for the 21-mm valve and 0.054 ± 0.041 mm2 for the 25-mm valve (P = .03). Hydrodynamic characteristics of the valves differed between pulmonary and aortic testing condition. Valve closing volumes were significantly lower under pulmonary hypotension and normal pulmonary conditions than under normal aortic conditions (P < .05). Conclusions: Under normal pulmonary pressure conditions, the hydrodynamic characteristics of Magna Ease valves are significantly different compared with aortic conditions. Further research is needed to determine whether these results are associated with prosthetic valve failure

Exploring dust around HD142527 down to 0.025" / 4au using SPHERE/ZIMPOL

We have observed the protoplanetary disk of the well-known young Herbig star HD 142527 using ZIMPOL Polarimetric Differential Imaging with the VBB (Very Broad Band, ~600-900nm) filter. We obtained two datasets in May 2015 and March 2016. Our data allow us to explore dust scattering around the star down to a radius of ~0.025" (~4au). The well-known outer disk is clearly detected, at higher resolution than before, and shows previously unknown sub-structures, including spirals going inwards into the cavity. Close to the star, dust scattering is detected at high signal-to-noise ratio, but it is unclear whether the signal represents the inner disk, which has been linked to the two prominent local minima in the scattering of the outer disk, interpreted as shadows. An interpretation of an inclined inner disk combined with a dust halo is compatible with both our and previous observations, but other arrangements of the dust cannot be ruled out. Dust scattering is also present within the large gap between ~30 and ~140au. The comparison of the two datasets suggests rapid evolution of the inner regions of the disk, potentially driven by the interaction with the close-in M-dwarf companion, around which no polarimetric signal is detected.Comment: 11 pages, 7 figures, accepted for publication in A

Shadows cast on the transition disk of HD 135344B. Multiwavelength VLT/SPHERE polarimetric differential imaging

The protoplanetary disk around the F-type star HD 135344B (SAO 206462) is in a transition stage and shows many intriguing structures both in scattered light and thermal (sub-)millimeter emission which are possibly related to planet formation processes. We study the morphology and surface brightness of the disk in scattered light to gain insight into the innermost disk regions, the formation of protoplanets, planet-disk interactions traced in the surface and midplane layers, and the dust grain properties of the disk surface. We have carried out high-contrast polarimetric differential imaging (PDI) observations with VLT/SPHERE and obtained polarized scattered light images with ZIMPOL in R- and I-band and with IRDIS in Y- and J-band. The scattered light images reveal with unprecedented angular resolution and sensitivity the spiral arms as well as the 25 au cavity of the disk. Multiple shadow features are discovered on the outer disk with one shadow only being present during the second observation epoch. A positive surface brightness gradient is observed in the stellar irradiation corrected images in southwest direction possibly due to an azimuthally asymmetric perturbation of the temperature and/or surface density by the passing spiral arms. The disk integrated polarized flux, normalized to the stellar flux, shows a positive trend towards longer wavelengths which we attribute to large aggregate dust grains in the disk surface. Part of the the non-azimuthal polarization signal in the Uphi image of the J-band observation could be the result of multiple scattering in the disk. The detected shadow features and their possible variability have the potential to provide insight into the structure of and processes occurring in the innermost disk regions.Comment: Accepted for publication in A&A, 20 pages, 15 figure