Necrosis esofágica aguda en pacientes post trasplante hepático. Un túnel oscuro desde el hígado al esófago

Acute esophageal necrosis is a rare entity endoscopically described as a black appearance of esophageal mucosa, generally of circumferential distribution that extends proximally from the gastroesophageal junction, and affects a variable length of this organ. It has a multifactorial etiology that includes a combination of ischemic mucosal esophageal vascular compromise associated with gastroesophageal reflux in patients with multiple comorbidities. Clinical management focuses on general support measures and treatment of the underlying illness and comorbidities. Although this pathology usually tends to a restitution-ad-integrum in 7-10 days, these patients have a high mortality rate more related to their clinical conditions and not due to this entity itself. Therefore, early diagnosis is crucial to initiate proper treatment. We present two cases of AEN in patients who underwent orthotopic liver transplantation.

Determinants of paravalvular leakage following transcatheter aortic valve replacement in patients with bicuspid and tricuspid aortic stenosis

Aims Paravalvular leakage (PVL) after transcatheter aortic valve replacement (TAVR) is a common complication in patients with bicuspid aortic valve (BAV). However, predictors and mechanisms of PVL are not well understood in this subset. The aim of this study was to analyse determinants and mechanisms of PVL in BAV and tricuspid aortic valve (TAV). Methods and results Of the 2394 consecutive patients undergoing transfemoral TAVR using new-generation valves at our centre, we identified 242 cases with BAV. To adjust for baseline differences, we performed 3 : 1 propensity score matching (TAVPS n = 726). We analysed the aortic root anatomy and calcification as well as the number, circumferential distribution, and predilection sites of PVL using pre-procedural multidetector computed tomography and post-TAVR echocardiography. In the matched cohort, the incidence of PVL ≥mild (BAV 51.9% vs. TAVPS 51.7%; P = 0.955) and PVL ≥moderate (BAV 5.0% vs. TAVPS 3.7%; P = 0.393), the circumferential distribution, and independent predictors were similar between BAV and TAVPS. Both the presence of peri-annular calcium chunks or LVOT calcification were highly associated with PVL in BAV and TAVPS patients, whereas in BAV patients neither the presence of a calcium bridge nor the volume of its calcification was related to PVL. Notably, the spatial localization of these lesions did not necessarily match the circumferential leak position. Conclusion The incidence, circumferential distribution, predilection sites, and predictors of PVL were similar in matched population of BAV and TAVPS patients undergoing transfemoral TAVR using new-generation devices. These novel findings suggest a common underlying mechanism of PVL in both entities.

The Effects of Multiple Swirl Generator Inlets Circumferential Distribution to a Liquid Fuelled Ultra-High Swirl Flameless Combustion Characteristics

This paper presents the experimental results of a simple cylindrical shaped, liquid fuelled flameless combustor which utilizes ultra-high swirl flow in the combustion process. 4 different swirl generator inlet configurations were tested in this work. Ethanol fuel were used during flameless mode. The experiments were conducted at equivalence ratio (F=1), with the flow rate of fuel set at 4.48*104 kg/s, and flow rate of air at 3.854*103 kg/s. The results revealed that by using all 12 tangential air inlets (swirl generator injectors), the swirl strength was reduced through evenly distributing the position of the injectors circumferentially. As a result, the combustor successfully suppressed the emission of NOx and CO to zero ppm for both gasses. It was also reported that flameless mode was established in all configurations, regardless of the swirl strength.

Analysis of Oil-Air Two-Phase Flow Characteristics inside a Ball Bearing with Under-Race Lubrication

Under-race lubrication can increase the amount of lubricating oil entering a bearing and greatly improve lubrication and cooling effects. The oil-air two-phase flow characteristics inside a ball bearing with under-race lubrication play a key role in lubrication and cooling performance. The motions of ball bearing subassemblies are complicated. Ball spin affects the oil volume fraction. In this paper, the coupled level set volume of fluid (CLSVOF) method is used to track the oil-air two-phase flow inside the ball bearing with under-race lubrication. The influence of various factors on the oil volume fraction inside the ball bearing with under-race lubrication is investigated, particularly rotating speeds, inlet velocity and the size of oil supply apertures under the inner ring. The influence of the ball spinning is analyzed separately. The result demonstrates that, on account of the centrifugal force, lubricating oil is located more on the outer ring raceway at rotational speeds of 5000 r/min, 10,000 r/min, 15,000 r/min and 20,000 r/min. The oil volume fraction inside the bearing gradually increases at an oil inlet velocity of 5 m/s, 10 m/s and 15 m/s. The circumferential distribution of oil is also similar. As the diameter of the oil supply aperture increases from 1.5 mm to 2 mm, the oil volume fraction increases inside the ball bearing. However, the oil volume fraction slightly decreases from 2 mm to 2.5 mm of oil supply aperture diameter. Ball spin does not affect the circumferential distribution trend of the lubricating oil, but slightly reduces the oil volume fraction. Furthermore, ball spin causes the surface fluid to rotate around its rotation axis and increases the speed.

Wetness Measurement and Droplet Transport Analysis in Actual Steam Test on a Scaled Low Pressure Turbine

Understanding the phenomenon and quantitative prediction of wet loss, quantitative prediction of erosion are still challenges in ST development. The aim of the actual steam test reported in this paper was to verify the performance of a newly developed ST. Still a comprehensive understanding of the wetness phenomenon is also a significant issue. Therefore, in connection with the actual steam test, efforts were made to develop a method for analyzing the three-dimensional causes of wetness loss and erosion. As the first report on the wet phenomenon analysis performed in this actual steam test, this paper reports wet measurement results and analysis results. In the actual steam testing of a 0.33 scaled steam turbine, wetness measurements were carried out at the third stage (L-1) and the final stage (L-0), and its characteristic wetness distribution was analyzed using our original CFD-code MHPS-NT. This 0.33 scaled steam turbine consists of the final three stages (LP-end) and the inlet steam conditioning stage (total of four stages), and wetness distributions in the blade height-wise were measured using two different wetness probes under several operating conditions. Wetness distribution did not change linearly with changes in ST inlet temperature, but dynamic changes in peak position and shape were observed. From the ST inlet to the exhaust chamber, the generation of fine droplets, the capturing of droplets by the wall surfaces, and the behavior of water films and coarse droplets were comprehensively analyzed using a three-dimensional (3-D) unsteady Eulerian-Lagrangian coupling solver that takes into account non-equilibrium condensation. This CFD code (MHPS-NT) is an improved version of Original-NT developed by Tohoku University. By considering the relative position and structure of the wet probe and blade cascade in CFD, it was found that the wetness is formed remarkable circumferential distribution by the moisture separation of the upstream blade rows and end-walls. The circumferential distribution of wetness can be a factor that makes it difficult to grasp the liquid phase distribution inside the steam turbine as an error factor independent of the accuracy of the optical measurement device. Due to the effects of water droplet capturing, the LP-end outlet wetness at the design point may be underestimated by 21% relative. It is also reported that because the wetness has a distribution in the meridian direction, wetness measurements by the wet probe may contain measurement errors independent of the measurement accuracy.

Influence of vaned diffuser on the potential effect of volute and stall inception of centrifugal compressor

In the automotive turbochargers centrifugal compressor, the volute has a strong potential effect, leading to circumferential nonuniformity of the impeller flow field and compressor stall. In this study, full-annulus unsteady simulations for centrifugal compressors with vaned/vaneless diffusers are carried out. The influence of the diffuser vane on the potential effect of the volute and stall behavior of a centrifugal compressor is studied in detail. Based on the distribution of the casing static pressure, the formation mechanism of the circumferential distribution of static pressure and the reverse propagation process of pressure waves caused by pressure distortion are revealed. The results of this study show that the diffuser vanes can weaken the potential effect of the volute on the impeller flow field by reducing the degree of static pressure distortion. The number of static pressure peaks in the circumferential direction is related to the number of vanes/blades. The diffuser vanes can change the circumferential position of the stall inception, but cannot eliminate the “locking effect” of the volute tongue on the circumferential position of the stall. In other words, the circumferential position of the stall inception is still determined by the volute tongue for a centrifugal compressor with a vaned diffuser. Although the degree of circumferential static pressure distortion inside the impeller is reduced, the stable operating range of the compressor cannot be significantly widened by adjusting the stagger angle of the diffuser vane when the stall first occurs at the impeller inlet.

Effect of Different EndoAnchor Configurations on Aortic Endograft Displacement Resistance: An Experimental Study

Purpose: This study investigated the effect of different EndoAnchor configurations on aortic endograft displacement resistance in an in vitro model. Materials and Methods: An in vitro model was developed and validated to perform displacement force measurements on different EndoAnchor configurations within an endograft and silicone tube. Five EndoAnchor configurations were created: (1) 6 circumferentially deployed EndoAnchors, (2) 5 EndoAnchors within 120° of the circumference and 1 additional, contralateral EndoAnchor, (3) 4 circumferentially deployed EndoAnchors, (4) 2 rows of 4 circumferentially deployed EndoAnchors, and (5) a configuration of 2 columns of 3 EndoAnchors. An experienced vascular surgeon deployed EndoAnchors under C-arm guidance at the proximal sealing zone of the endograft. A constant force with increments of 1 newton (N) was applied to the distal end of the endograft. The force necessary to displace a part of the endograft by 3 mm was defined as the endograft displacement force (EDF). Two video cameras recorded the measurements. Videos were examined to determine the exact moment 3-mm migration had occurred at part of the endograft. Five measurements were performed after each deployed EndoAnchor for each configuration. Measurements are given as the median and interquartile range (IQR) Q1, Q3. Results: Baseline displacement force measurement of the endograft without EndoAnchors resulted in a median EDF of 5.1 N (IQR 4.8, 5.2). The circumferential distribution of 6 EndoAnchors resulted in a median EDF of 53.7 N (IQR 49.0, 59.0), whereas configurations 2 through 5 demonstrated substantially lower EDFs of 29.0 N (IQR 28.5, 30.1), 24.6 N (IQR 21.9, 27.2), 36.7 N, and 9.6 N (IQR 9.4, 10.0), respectively. Decreasing the distance between the EndoAnchors over the circumference of the endograft increased the displacement resistance. Conclusion: This in vitro study demonstrates the influence EndoAnchor configurations have on the displacement resistance of an aortic endograft. Parts of the endograft where no EndoAnchor has been deployed remain sensitive to migration. In the current model, the only configuration that rivaled a hand-sewn anastomosis was the one with 6 EndoAnchors. A circumferential distribution of EndoAnchors with small distances between EndoAnchors should be pursued, if possible. This study provides a quantification of different EndoAnchor configurations that clinicians may have to adopt in clinical practice, which can help them make a measured decision on where to deploy EndoAnchors to ensure good endograft fixation.

Lumen Gain After Endovascular Therapy in Calcified Superficial Femoral Artery Occlusive Disease Assessed by Intravascular Ultrasound (CODE Study)

Purpose: To assess calcium patterns in superficial femoral artery (SFA) disease before and after balloon angioplasty ± stent implantation using fluoroscopy, angiography, and intravascular ultrasound (IVUS) imaging and then correlate calcification severity and midterm clinical outcomes. Materials and Methods: A multicenter investigation was carried out to retrospectively review 130 symptomatic patients (mean age 73.2±8.4 years; 86 men) with de novo SFA lesions who had successfully undergone endovascular therapy (EVT) at 7 centers between January and October 2015. The primary outcome was lumen gain measured as minimum lumen area (MLA) in post-EVT IVUS images according to calcification severity. The secondary outcomes included rates of stent malapposition, restenosis, and clinically-driven target lesion revascularization (TLR). Results: A total of 102 (78.5%) cases had calcification in the lesions over a mean length of 64.3±72.8 mm. Of these, 70 cases were classified as having bilateral calcification according to fluoroscopy and angiography; 50 (49%) lesions had ≥180° calcification according to IVUS. The lumen gain in calcified lesions was significantly smaller than in the 28 noncalcified lesions (14.1±4.4 vs 17.8±5.2 mm2, p<0.001). IVUS-evaluated circumferential distribution of calcium (<180° or ≥180°) was independently associated with lumen gain after EVT (p<0.001). Among the calcification characteristics, a calcification angle ≥180° showed the strongest correlation to postprocedure MLA. Moreover, the restenosis rate was significantly higher in the severe (≥180°) calcification group (p<0.018). The severity of calcification was also associated with the risk of stent malapposition (p=0.022 for trend) but not TLR (p=0.57). Conclusion: IVUS evaluation of calcification in SFA lesions predicted lumen gain after EVT. Severe calcification in a ≥180° arc prevented successful dilation of the lesion with either plain balloon angioplasty or a nitinol stent. Accurate assessment of calcification patterns by IVUS is useful in maximizing the efficacy of endovascular therapy.