Low Pressure Gradient Research Articles

S2193 Splenic Artery Collaterals Masquerading as Gastric Varices: An Uncommon Cause of Massive Upper GI Bleed

INTRODUCTION: Upper gastrointestinal bleeding (UGIB) is most commonly due to peptic ulcer disease (PUD). However in patients with splenic artery thrombosis, collateral arterial vessels can develop. If these abnormal vessels erode into the stomach mucosa, massive UGIB can occur. Here we present a case of UGIB from submucosal splenic collateral arteries. CASE DESCRIPTION/METHODS: A 56 year old male with history of Factor 5 Leiden and antiphospholipid antibody syndrome (APLS) presented with melena and hematemesis. Esophagogastroduodenoscopy (EGD) showed possible gastric varices in the fundus with an area of ulceration (Figure 1). The patient’s prior history of heavy alcohol use and the presence of a nodular liver on CT scan suggested underlying cirrhosis and portal hypertension as the etiology for the gastric varices. However the patient was found to have a low hepatic venous pressure gradient (2 mmHg) and a subsequent liver biopsy did not reveal cirrhosis. The splenic vein was also noted to be patent on CT scan. Several days after admission, the patient experienced another episode of hematemesis with associated hypotension and tachycardia. CT angiogram at the time did not reveal any active bleeding, but did show a splenic artery thrombosis with several collateral vessels. Subsequent angiogram demonstrated large arterial collaterals in the gastric fundus with outflow to the spleen, bypassing the occluded splenic artery (Figure 2). These collateral vessels were embolized successfully and he had no further bleeding. DISCUSSION: This case highlights the importance of multidisciplinary patient care and careful assessment of a patient’s medical history and anatomy to accurately diagnose and treat underlying pathology. While our patient was thought to have varices on EGD, he did not have cirrhosis, splenic vein thrombosis or portal hypertension which made the diagnosis of gastric varices unlikely. However, he did have a splenic artery thrombosis due to underlying APLS which led to the formation of submucosal gastric arterial collateral vessels and UGIB. Submucosal arterial collateral vessels are a rare cause of UGIB and there are only a few cases described in the literature. They can form as a result of splenic artery thrombosis due to underlying coagulopathy, pancreatitis, abdominal trauma or congenital absence of the splenic artery. If these abnormal collateral vessels erode through the stomach mucosa, they can lead to UGIB. Treatment involves surgery (partial gastrectomy and splenectomy) or embolization.Figure 1.: Possible gastric varix in the stomach fundus with an area of ulceration seen on EGD.Figure 2.: Angiogram demonstrating large arterial collaterals in the gastric fundus with outflow to the spleen, bypassing an occluded splenic artery.

Aortic Valve Neocuspidization (Ozaki Procedure) in Patients with Small Aortic Annulus (≤21 mm): A Multicenter Study

ABSTRACT Background Patients with aortic stenosis (AS) and small aortic annulus (SAA) who undergo surgical aortic valve replacement (SAVR) are more likely to receive smaller prostheses, predisposing them to prosthesis patient-mismatch (PPM). Since the Ozaki Procedure (aortic valve neocuspidization – AVNeo) has proved promising, we aimed to assess its immediate results in this scenario. Methods AVNeo was performed in 106 consecutive patients from January 2017 to March 2019 at three centers. The records were prospectively collected and reviewed retrospectively. Most of the patients were older than 60 years and 97.2% had AS. Preoperative echocardiography showed an average peak pressure gradient of 64.9 ± 20.7 mmHg and a mean pressure gradient of 46.0 ± 12.2 mm Hg for patients with AS and an annular diameter of 19.8 ± 1.1 mm for all patients. EOA and indexed EOA (iEOA) averaged 0.7 ± 0.2 cm2 and 0.4 ± 0.2 cm2/m2 before surgery, respectively. Results There was no conversion to SAVR. Four patients needed reoperation for bleeding, but none needed reoperation due to early infective endocarditis. Median intensive care unit and hospital length of stay were 1.5 ± 1.2 and 13.7 ± 5.1 days, respectively. There were two in-hospital deaths due to non-cardiac causes. Postoperative peak pressure gradient averaged 11.8 ± 5.9 mmHg and mean pressure gradient averaged 7.3 ± 3.5 mmHg, which means statistically significant average decreases of 58.1 and 38.7 mmHg, respectively. Postoperative EOA and iEOA averaged 2.5 ± 0.4 cm2 and 1.3 ± 0.3 cm2/m2, which means statistically significant average increases of 1.8 cm2 and 0.9 cm2/m2, respectively. Conclusions AVNeo is feasible and reproducible with good immediate results. Our findings show that AVNeo produces immediate postoperative low-pressure gradients, larger EOA, and minimal regurgitation of the aortic valve.

Effect of stretching parameter in a non-linear MHD flow close to stagnation point

A parametric study exploring the fall out of MHD and stretching parameter on a viscous incompressible fluid through a vertical porous plate with heat absorption is described. The MHD boundary layer equations with low pressure gradient, controlled by a system of non-linear partial differential equations are work out by adopting Homotopy Perturbation method (HPM). The influence of different relevant physical characteristics are presented and discussed graphically.

RP-HPLC METHOD DEVELOPMENT AND VALIDATION FOR THE COMBINATION OF IMIQUIMOD AND SALICYLIC ACID

Objective: The present study was undertaken to develop and validate an RP-HPLC method for the combination of imiquimod and salicylic acid
 Methods: The method was carried out on Nucleodur C18 (250 mm × 4.6 mm I.D., 5 ????m) using low-pressure gradient elution mode. The mobile phase was used as 30M potassium dihydrogen phosphate and acetonitrile (45:55) pH 6.5 adjusted using ortho-phosphoric acid. The concentration of solvents was 1-20 µg/ml and the volume of injection was 20 mcl with the flow rate of 1.0 ml/min. The absorption maxima of salicylic acid and imiquimod were found 234 nm and 226 nm, respectively.
 Results: The method was validated and showed the linearity greater than 0.99% and with precision (RSD%<1). The limit of detection (LOD) and limit of quantification (LOQ) of salicylic acid was found to be 0.09756 µg/ml and 0.2956 µg/ml, respectively, and imiquimod was found to be 0.044031 µg/ml and 0.13334 µg/ml, respectively.
 Conclusion: The method developed in the present study was found to be sensitive, specific, and can be applied for the simultaneous estimation of imiquimod and salicylic acid.

The role of large-scale dynamics in an exceptional sequence of severe thunderstorms in Europe May–June 2018

Abstract. Over 3 weeks in May and June 2018, an exceptionally large number of thunderstorms hit vast parts of western and central Europe, causing precipitation accumulations of up to 80 mm within 1 h and several flash floods. This study examines the conditions and processes that made this particular thunderstorm episode exceptional, with a particular focus on the interaction of processes across scales. During the episode, a blocking situation persisted over northern Europe. Initially, the southwesterly flow on the western flank of the blocking anticyclone induced the advection of warm, moist, and unstably stratified air masses. Due to the low-pressure gradient associated with the blocking anticyclone, these air masses were trapped in western and central Europe, remained almost stationary, and prevented a significant air mass exchange. In addition, the weak geopotential height gradients led to predominantly weak flow conditions in the mid-troposphere and thus to low vertical wind shear that prevented thunderstorms from developing into severe organized systems. Due to a weak propagation speed in combination with high rain rates, several thunderstorms were able to accumulate enormous amounts of precipitation that affected local-scale areas and triggered several torrential flash floods. Atmospheric blocking also increased the upper-level cut-off low frequency on its upstream regions, which was up to 10 times higher than the climatological mean. Together with filaments of positive potential vorticity (PV), the cut-offs provided the mesoscale setting for the development of a large number of thunderstorms. During the 22 d study period, more than 50 % of lightning strikes can be linked to a nearby cut-off low or PV filament. The exceptionally persistent low stability over 3 weeks combined with a weak wind speed in the mid-troposphere has not been observed during the past 30 years.

The electroviscous flow of non-Newtonian fluids in microtubes and implications for nonlinear flow in porous media

This paper aims to interpret the low-velocity nonlinear flow occurring in low-permeability reservoirs based on the theories of electrokinetic transport and non-Newtonian rheology of fluids. To achieve this end, we simulate the steady-state electroviscous flow of Bingham-Papanastasiou (BP) fluids in circular microtubes by simultaneously solving the Poisson-Boltzmann and the modified Navier-Stokes equations. The induced electrical field strength Es, velocity profiles, and the transport capacity of the non-Newtonian fluid under the effects of various factors (such as capillary radius R, zeta potential ζ, yield stress τ0, and stress growth index m) were examined. The results show that the generated Es of the BP fluid is highly affected by the fluid rheology, which is quite different from that of the Newtonian liquid. The velocity profiles become lower and flatter as m or τ0 increases, and this is more remarkable in smaller microtubes. The apparent viscosity of non-Newtonian fluid declines monotonically with increasing c∞, yet non-monotonically with R, m, τ0, and ζ. In addition, the low-velocity nonlinear flow in microtubes can be successfully captured when considering the electrokinetic flow of the non-Newtonian fluid rheology. While for the Newtonian fluid, only involving the electroviscous effect fails to generate the nonlinear flow behavior. The contributions of electrokinetic parameters versus rheological properties to the degree of flow nonlinearity are also discussed. The impact of electrokinetic parameters (ζ, c∞) on the flow characteristics is significant at high-pressure gradients and becomes trivial when the pressure gradient is relatively low. In contrast, the fluid rheological parameters (m, τ0) greatly determine the magnitude of the flow nonlinearity occurring at the low-pressure gradients. In sum, the electroviscous flow of BP fluids in microchannels provides a possible explanation of the low-velocity non-Darcy flow in porous media.

Feedback and Ballooning Instabilities in the Magnetosphere‐Ionosphere Coupling

AbstractA unified model for the feedback and ballooning instabilities in the magnetosphere‐ionosphere (M‐I) coupling is developed by means of the reduced magnetohydrodynamic and two‐fluid equations, involving the local current closure and the ionospheric conductivity change in a scale of auroral fine structures, self‐consistently. In a low pressure gradient case, the Alfvén harmonics are destabilized through the feedback mechanism, while the ballooning instability appears if the magnetospheric pressure gradient exceeds a critical value. Transition of the dominant instability between the feedback and ballooning modes is brought by change of the normalized pressure gradient or the convection electric field in the magnetosphere. The obtained results imply a variety of appearance of auroral arcs and beads in the M‐I coupling system.

Research on Casualty Characteristics of Fish in Tubular Turbine based on IB-LBM method

The IB-LBM numerical method particularly effective at simulating the motion dynamics of individual or more fish in the turbine. Based on this method, the pressure and pressure gradient damage of the fish passing through the tubular turbine are analyzed. From the results, it can be found that the low pressure and excessive pressure gradient in the runner can result in irreversible damage on the swimming bladder and eyes of the fish. So the runner is the main component induces fish casualty, and its minimum pressure and pressure gradient need to be limited in the design process.

Tectonic implications of juxtaposed high- and low-pressure metamorphic field gradient rocks in the Turvo-Cajati Formation, Curitiba Terrane, Ribeira Belt, Brazil

The Turvo-Cajati Formation (TCF) is an important unit forming the Curitiba Terrane, a major segment of the southern Ribeira Belt, SE Brazil. It is composed of rocks of greenschist (LTCF), amphibolite (MTCF) and granulite (HTCF) facies conditions. Previous studies in the HTCF indicate that the unit underwent extensive partial melting under high-pressure conditions (670–810 °C and 9.5–12 kbar), within the kyanite stability field. In this paper, a study of the metamorphic zoning within the LTCF and MTCF is undertaken using pseudosection modeling in the NCKFMASHTO and MnNCKFMASHTO model systems coupled with detrital zircon U–Pb geochronology. Four metamorphic zones are recognized for the LTCF and MTCF: biotite, garnet, staurolite and sillimanite zones, with predominance of sillimanite zone and pressures lower than 8 kbar, as staurolite breaks down straight to sillimanite, without formation of a kyanite zone. Pseudosections yielded metamorphic peak conditions of ~530–560 °C and ~6–7.5 kbar (garnet zone) and ~660–690 °C and ~6–7.5 kbar (sillimanite zone). The metamorphic field gradient is flat and of low to medium pressure, below the typical Barrovian-type baric regime, and different from the HTCF. Available petrological and geochronological data suggest that the TCF comprises a paired low-P and high-P metamorphic belt, associated with a major Ediacaran suture zone in the southern Ribeira Belt. Probability density plots from detrital zircon U–Pb ages indicate late-Cryogenian-Ediacaran arc-related and Rhyacian sources for all TCF sub-units. This scenario suggests that the TCF is made up of a collisional juxtaposition of an accretionary wedge (HTCF) and a back-arc basin (LTCF and MTCF) on the border of a microplate, which includes a Rhyacian basement microcontinent, the Atuba Complex. It is inferred the high metamorphic gradient recorded in the LTCF and MTCF was related with asthenospheric upwelling in the back-arc region, which also produced extensive partial melting in the Atuba Complex basement.

Interannual variability of the summer wind energy over China: A comparison of multiple datasets

AbstractBecause of the increase in the nation's need for wind energy, the impacts of climate change on wind energy have been investigated. In addition to long‐term changes, wind energy also shows robust interannual variations, but little effort has been devoted to understanding the underlying mechanisms. In this study, the impact of El Niño on the summer mean wind power density (WPD) over China is investigated. The abilities of five sets of reanalysis data in measuring the interannual variability of the WPD over China are assessed. Encouraging results are seen for all reanalysis datasets, with the MERRA and ERA‐Interim datasets showing the best performance. The relationship between El Niño and the following summer WPD is identified over China. During El Niño decaying year summers, the WPD over south of the Yangtze River valley increases, whereas the WPD over north of the Yangtze River valley decreases. The WPD changes are dominated by an anomalous anticyclone located in the northwestern Pacific. The anticyclone leads to strong southerly winds in southern China and thereby enhances the WPD. In regions north of the Yangtze River valley, the low surface pressure gradient causes a reduction in wind speed and thereby a weak WPD. Because the year‐by‐year variation in El Niño‐Southern Oscillation (ENSO) is highly predictable, our results shed light on the seasonal prediction of wind power over China.

Deciphering the metamorphic evolution of the Pulo do Lobo metasedimentary domain (SW Iberian Variscides)

Abstract. The Pulo do Lobo domain is one of the units exposed within the orogenic suture zone between the Ossa-Morena and the South Portuguese zones in the SW Iberian Variscides. This metasedimentary unit has been classically interpreted as a Rheic subduction-related accretionary prism formed during pre-Carboniferous convergence and eventual collision between the South Portuguese Zone (part of Avalonia) and the Ossa-Morena Zone (peri-Gondwanan terrane). Discrete mafic intrusions also occur within the dominant Pulo do Lobo metapelites, related to an intra-orogenic Mississippian transtensional and magmatic event that had a significant thermal input. Three different approaches have been applied to the Devonian–Carboniferous phyllites and slates of the Pulo do Lobo domain in order to study their poorly known low-grade metamorphic evolution. X-ray diffraction (XRD) was used to identify the mineralogy and measure crystallographic parameters (illite “crystallinity” and K-white mica b-cell dimension). Compositional maps of selected samples were obtained from electron probe microanalysis, which allowed for processing with XMapTools software, and chlorite semiempirical and thermodynamic geothermometry was performed. Thermometry based on Raman spectroscopy of carbonaceous material (RSCM) was used to obtain peak temperatures. The microstructural study shows the existence of two phyllosilicate growth events in the chlorite zone, the main one (M1) related to the development of a Devonian foliation S1 and a minor one (M2) associated with a crenulation cleavage (S2) developed in middle–upper Carboniferous times. M1 entered well into epizone (greenschist facies) conditions. M2 conditions were at lower temperature, reaching the anchizone–epizone boundary. These data accord well with the angular unconformity that separates the Devonian and Carboniferous formations of the Pulo do Lobo domain. The varied results obtained by the different approaches followed, combined with microstructural analysis, provide different snapshots of the metamorphic history. Thus, RSCM temperatures are higher in comparison with the other methods applied, which is interpreted to reflect a faster re-equilibration during the short-lived thermal Mississippian event. Regarding the metamorphic pressure, the data are very homogeneous: very low celadonite content (0 %–10 %) in muscovite (and low values of K-white mica b-cell dimension; 8.995 Å mean value), indicating a low pressure–temperature gradient, which is unexpected in a subduction-related accretionary prism. Highlights A multidisciplinary approach has been applied to study the metamorphism of the Pulo do Lobo metapelites. Devonian metamorphism entered epizone conditions. Carboniferous metamorphism reached the anchizone–epizone boundary. The inferred low-pressure gradient is incompatible with a subduction-related accretionary prism.

Genesis of Antibiotic Resistance LIX: Fluid Resuscitation Induced Aberrant Intracranial Pressure (“Monroe‐Kellie” Doctrine (MKD) Contort Tethered Leucocytes / Platelets Crest “Critical Closing Pressure” (CCP)

NCT01663701 noted that the median volume of iv fluid administered within 6 hours of presenting to ER in the sepsis intervention group was 3.5 L. The mean volume administered during the similar time interval in prior sepsis resuscitation trials were 5.0 L (EGDT); 5.1 L (ProCESS); and 4.5 L (ARISE). Criticisms of NCT01663701 such as a. the suggested vs administered median volume of fluid administered during the initial phase of resuscitation in the sepsis protocol group (3.5L) may have been higher than the 30 mL/kg recommended by SSC guidelines; b.”Each 1‐hour delay in antibiotic administration was associated with an absolute increase in mortality in the range of 5% to 10%”; and c. the median volume of iv fluid administered between ER presentation and 6 hours for BMI 18.5 kg/m2 ~ 70 mL/kg, here we present a plausible pathophysiological sequel as a contributing factor for mortality rate. Within the six hrs. of fluid resuscitation, a surge of fluid bolus mounted an adverse pressure gradient on the sphincters in metarterioles deregulating the pulsatile blood flow into the capillary bed. Based on the “Whole Brain Fluid and Osmolyte Network Model or” or “The whole brain network” approach a mechanistic model inclusive of major cranial compartments simulated the effect of osmotic therapy predicted that critical intracranial pressure (ICP) increased to >30 mmHg, with insufficient cerebral perfusion, and ventriculomegaly. The ventricular enlargement, in turn, reduces extracellular milieu for fluid exchange lead to a chronic increase in ventricular size shifts attributed to osmolyte administered. It is our hypothesis that after fluid resuscitation blood flows against an adverse pressure gradient in the capillary bed. The fluid particles such as activated and/or aggregating Cellular Aggregates near to the endothelial layer due to their low kinetic energy, “Cellular Aggregates” flows in the opposite direction. Such Cellular Aggregates cannot surmount the adverse pressure, lead to the formation of eddies. Such eddies in the arterial end are likely to cause local flow reversal zone and which retard the velocity concurrently the pressure of the blood flow. Under the low velocity and pressure gradient, the cellular eddies start separating from the endothelium referred to as boundary layer separation causing the blood flow to decelerate against an adverse pressure gradient. Then in the upstream part which is the venous end of the capillary bed, where the cellular eddies achieve boundary layer separation, causing blood pressure to drop from that of the arterial end creating the eddies to drag. At this stage, the pressure distribution in the capillary bed is at the stagnation point, where the velocity becomes zero at which cellular eddies form DIC. Sustained fluid bolus with vasopressor likely to form a non‐pulsatile flow pattern forming turbulent eddies in the venous end and disseminate the coagulated eddies leading to an aberration in the “MKD”. Dysregulated ICP, in turn, alter the ARGR leading to hypoperfusion subsequently coma.Support or Funding InformationSupported by pd funds and in part CME activities of Subburaj Kannan MD PhD for www.aaets.org

Cement slurries for sealing boreholes in conditions of low pressure gradients of rock fracturing and for workover jobs or operations

Cement slurries for sealing boreholes in conditions of low pressure gradients of rock fracturing and for workover jobs or operations

Prediction of high-quality coalbed methane reservoirs based on the fuzzy gray model: An investigation into coal seam No. 8 in Gujiao, Xishan, North China

Coalbed methane (CBM) resources are abundant in the Gujiao block, Xishan coalfield, China. However, few studies have been conducted on the coalbed methane geology of the Gujiao block. In the present study, based on logging responses and numerical simulations, the coal structures of coal seam No. 8 of this block were identified, and the mechanical properties of the coal and its roof/floor were calculated. The geological factors influencing the coalbed methane reservoir were quantitatively characterized according to the fuzzy gray model. High-quality coalbed methane reservoirs in the No. 8 coal were predicted and classified using the model, and some suggestions on rational exploitation were determined. Reservoirs of the No. 8 coal are dominated by the III-type, followed by the II- and IV-types. The III-type reservoirs are the most common, and primarily developed at the Xiqu, Zhenchengdi, Malan, and Tunlan coal mines in the north of the studied area. The III-type reservoirs represent low coalbed methane contents, high thickness proportions of granulated-mylonitized coal, and low burial depths. The II-type reservoirs are primarily developed close to the axis of the Malan syncline and in the south and northwest of the studied area, and have low permeability, less significant differences between the mechanical properties of coals and their roofs and floors, and low reservoir pressure gradients. The IV-type reservoirs have a scattered development, dominance of granulated-mylonitized coal, and low permeability, indicating low potential to improve reservoir permeability. Targeted exploitation technology and drainage systems corresponding to the different types of coal reservoirs should be proposed to improve coalbed methane production.

Effect of stretching parameter in a non-linear MHD flow close to stagnation point

A parametric study exploring the fall out of MHD and stretching parameter on a viscous incompressible fluid through a vertical porous plate with heat absorption is described. The MHD boundary layer equations with low pressure gradient, controlled by a system of non-linear partial differential equations are work out by adopting Homotopy Perturbation method (HPM). The influence of different relevant physical characteristics are presented and discussed graphically.

Modelling and simulation analysis of porous polymeric scaffold for the replacement of Bruch's membrane as a therapy for age-related macular degeneration

Age related macular degeneration (AMD) is a common disease that is prevalent among people of age 50. It is characterised by the loss of retinal pigment epithelial (RPE) cells from the macula of eye due to the deposition of drusen in the Bruch's membrane that supports the RPE cells. Treatment for AMD is to replace Bruch's membrane with scaffolds that provide conducive environment for the RPE cells to adhere and proliferate. In this study, a scaffold made of porous poly (caprolactone) (PCL) was designed using the tool COMSOL Multiphysics and its properties like structural integrity and the fluid flow were analysed using Brinkman's equation. The model has a square geometry with a dimension of 100 × 100 × 4 μm through which blood was allowed to flow from bottom to top across the geometry. The analysis was carried out for scaffolds with different porosity. The results show that the scaffold with higher porosity has a lower pressure gradient which is necessary for RPE cell adherence and is mechanically stable. This proves that a PCL scaffold with higher porosity is a potential replacement for Bruch's membrane.

Modelling and simulation analysis of porous polymeric scaffold for the replacement of Bruch's membrane as a therapy for age-related macular degeneration

Age related macular degeneration (AMD) is a common disease that is prevalent among people of age 50. It is characterised by the loss of retinal pigment epithelial (RPE) cells from the macula of eye due to the deposition of drusen in the Bruch's membrane that supports the RPE cells. Treatment for AMD is to replace Bruch's membrane with scaffolds that provide conducive environment for the RPE cells to adhere and proliferate. In this study, a scaffold made of porous poly (caprolactone) (PCL) was designed using the tool COMSOL Multiphysics and its properties like structural integrity and the fluid flow were analysed using Brinkman's equation. The model has a square geometry with a dimension of 100 × 100 × 4 μm through which blood was allowed to flow from bottom to top across the geometry. The analysis was carried out for scaffolds with different porosity. The results show that the scaffold with higher porosity has a lower pressure gradient which is necessary for RPE cell adherence and is mechanically stable. This proves that a PCL scaffold with higher porosity is a potential replacement for Bruch's membrane.

РЕЗУЛЬТАТЫ БИОПРОТЕЗИРОВАНИЯ СТВОРОК АОРТАЛЬНОГО КЛАПАНА У ПАЦИЕНТОВ СО СТЕНОЗОМ УСТЬЯ АОРТЫ ПРИ УЗКОМ ФИБРОЗНОМ КОЛЬЦЕ

Objective: To evaluate hemodynamic parameters after bioprosthetics of the aortic valve cusps, as well as complications arising in patients in the early and long-term period (6 months). Material and methods: 9 patients underwent bioprosthetics of the valves of the aortic valve with a narrow fibrous ring. The function of the cusps and left ventricle remodeling were evaluated on the 7-10th day and after 6 months. Results: Patients underwent echocardiographic examination before the intervention, in the early and long-term postoperative period. The analysis showed rather low values of pressure gradients on the aortic valve and rather large values of the effective and index area of the valve opening in patients after bioprosthetics of the aortic valve cusps. Conclusions: In the early postoperative period, prosthetics of the aortic valve leaflets with xenopericardium, according to an echocardiographic study, are associated with low average and peak pressure gradients on the aortic valve and a larger effective area and index effective area of the valve opening. The risk of the “patient-prosthesis mismatch” phenomenon with narrow fibrous rings is significantly lower with xenopericardial bioprosthetics than with standard prosthetics.

New Insight in the Assessment of Left Ventricular Function in Paradoxical Low Flow Aortic Stenosis Patients with Normal Left Ventricular Ejection Fraction: A Mini-Review

Paradoxical valvular aortic stenosis (VAS) is a challenging area of clinical cardiology for the practitioners. It involves a small aortic valve area, low flow rate and mean pressure gradient although there is normal left ventricular ejection fraction. The aim of this study was to assess left ventricular (LV) dysfunction in a symptomatic severe aortic valve stenosis which is of crucial importance in identifying patients at risk of heart failure, postoperative complications and increased mortality. There are new insights which are involved in assessment of LV myocardial function including global longitudinal strain (GLS) by two-dimensional speckle tracking echocardiography (2D STE), myocardial performance index (MPI) and maximum rate of LV pressure rise (+dP/dt) during isovolumetric contraction time of the LV. This information can provide both diagnostic and prognostic information in addition to standard echocardiographic and clinical parameters. However, a profound understanding of the complex interaction between loading conditions, chamber geometry and contractility is necessary for the correct interpretation of myocardial deformation in order to draw appropriate conclusions in patients with aortic valve disease. This mini review is related to new and novel insights into the assessment of left ventricular function (LVF) in paradoxical low flow aortic stenosis patients with normal left ventricular ejection fraction (LVEF).

РЕЗУЛЬТАТЫ ИМПЛАНТАЦИИ ПРОТЕЗОВ БЫСТРОГО РАЗВЕРТЫВАНИЯ PERCEVAL У ПАЦИЕНТОВ СО СТЕНОЗОМ УСТЬЯ АОРТЫ ПРИ УЗКОМ ФИБРОЗНОМ КОЛЬЦЕ

Objective: To evaluate hemodynamic parameters after implantation of Perceval prostheses of quick deployment, as well as various complications that arose in patients in the early and long-term postoperative period (6 months).Material and methods: We performed 20 implantations of Perceval prostheses of quick deployment in a narrow fibrous ring. The function of the prosthesis was evaluated in the postoperative period on the 7-10th day and after 6 months. The patients underwent echocardiographic examination before the intervention, in the early and long-term postoperative period.Results: The analysis of the results of echocardiography showed rather low values of pressure gradients on the aortic valve and rather large values of the effective and indexed area of the valve opening in patients after implantation of Perceval prostheses.Conclusions: According to the results of echocardiographic study, implantation of Perceval prostheses is associated with low average and peak pressure gradients on the aortic valve and the effective area and indexed effective area of the valve opening.