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At least 235 records · Page 13Linked to original sources
PubMed1984

In vitro hydrodynamic performance of various cardiac prosthetic valves tested in a modified nonpulsatile flow system.

Hydrodynamic studies were performed in a modified nonpulsatile flow system to compare the efficiency of various prosthetic cardiac valves in vitro. Apart from direct flow/pressure relations across the valves the effective orifice area available for forward flow was determined by derivations of the Bernoulli hydrodynamic equation. By defining the relationship between calculated effective orifice area and known orifice area of the valves a more precise appraisal of the hydrodynamic characteristics of the various valve designs was possible.

Heart Valve Prosthesis↗
PubMed2003

Acute superior mesenteric artery embolism: rapid reperfusion with hydrodynamic thrombectomy and pharmacological thrombolysis.

PURPOSE: To report a case of acute superior mesenteric artery (SMA) embolism successfully treated with hydrodynamic thrombectomy and pharmacological thrombolysis. CASE REPORT: A 67-year-old man was admitted to the hospital with acute severe abdominal pain. Selective angiography via a femoral puncture revealed a complete embolic occlusion distal to the first jejunal branch of the SMA. Hydrodynamic thrombectomy resolved the severe abdominal pain of the patient in approximately 10 minutes after the start of thrombectomy. Local continuous thrombolysis with urokinase resulted in near complete restoration of the mesenteric flow after 24 hours. The patient made an uneventful recovery and continues to do well on warfarin therapy 8 months after treatment; he has shown no evidence of malabsorption. CONCLUSIONS: Although insertion of the device into the SMA via a femoral puncture is a difficult approach, we propose that hydrodynamic thrombectomy followed by local thrombolysis is a useful treatment for acute superior mesenteric artery embolism.

Acute Disease↗
PubMed2006

In vitro hydrodynamic properties of the Miethke ProGAV hydrocephalus shunt.

BACKGROUND: Adjustable shunts are very popular in the management of hydrocephalus and are believed to help in minimizing the number of surgical revisions. The drawback with almost all constructions is that they may be accidentally readjusted in relatively weak magnetic fields (around 30-40 mTesla) MATERIALS AND METHODS: The ProGav Miethke shunt is composed of an adjustable balloon-spring valve unit and an integrated over-drainage compensating gravitational device (known as the shunt assistant). A mechanical 'brake' is intended to prevent changes to the valve's performance level in a strong magnetic field. We evaluated the performance and hydrodynamic properties of a sample of three valves in the UK Shunt Evaluation Laboratory. RESULTS: All the shunts showed good mechanical durability over the three-month period of testing, and good stability of hydrodynamic performance over a one-month period. The pressure-flow performance curves, operating, opening and closing pressures fell within the limits specified by the manufacturer, and changed according to the programmed performance levels. The operating pressure increased when the shunt assistant was in the vertical position, as specified. The valve has a low hydrodynamic resistance (0.53 mm mmHg ml(-1) min(-1)). External programming proved to be easy and reliable. Strong magnetic fields from a 3 Tesla MR scanner were not able to change the programming of the valve. CONCLUSION: The ProGAV shunt is an adjustable, low resistance valve that is able to limit posture-related over-drainage. Unlike other adjustable valves, the ProGAV cannot be accidentally re-adjusted by external magnetic field such as a 3T MR scanner.

Journal Article↗
PubMed2002

Hydrodynamics of the new Medos aortic cannula.

BACKGROUND: Postoperative neurologic complications in cardiac surgery patients are considered to be associated with the design of an aortic cannula and its hydrodynamic profile. To gain knowledge about the hydrodynamics of a new cannula type, based on the integration of a helical stator in its tip, was the aim of the present study. METHODS: Pressure gradients and back pressures of the new Medos aortic cannula were measured and compared with a commonly used single-stream cannula at varying flow rates in a mock circulation. Additionally, flow visualization was performed by ink injection. RESULTS: Pressure gradients across the Medos cannula were 25.5-31.8% lower at all flow rates measured when compared to the reference cannula. Back pressures of the Medos cannula were 64.1-67.9% lower than reference back pressures. CONCLUSIONS: The Medos cannula provides improved hydrodynamic characteristics, probably reducing the risk of atherosclerotic embolism and cerebral malperfusion by avoidance of high back pressures and sandblasting effect.

Aorta↗
PubMed2003

Can the USP paddle method be used to represent in-vivo hydrodynamics?

Experiments in-vitro and in dogs were conducted to find in-vitro hydrodynamic conditions that can be used to represent gastrointestinal motility patterns. Specifically, the dissolution performance of micronised and coarse-grade felodipine (a poorly soluble, neutral, lipophilic drug) was studied in a biorelevant medium in the USP paddle apparatus at various paddle speeds. Ratios of percentage dissolved (slower:faster rev min(-1)) were calculated pairwise. These ratios were then compared with AUC ratios obtained in a corresponding pharmacokinetic study in Labradors, in which the absorption of both the micronised and coarse-grade felodipine had been compared under two gastrointestinal hydrodynamic conditions. Using a paddle speed combination of 75 and 125 rev min(-1) to represent the motility patterns in response to administration of normal saline and 5% glucose, respectively, the in-vitro ratios (75:125 rev min(-1) dissolution ratio was 91% for the micronised and 46% for the coarse-grade powder) showed good agreement with the pharmacokinetic data (saline-to-glucose absorption ratio was 98% for the micronised and 46% for the coarse-grade powder). It was concluded that, provided an appropriate composition is chosen for the dissolution test, the USP paddle apparatus can be used to reflect variations in hydrodynamic conditions in the upper gastrointestinal tract.

Animals↗
PubMed2003

Hydrodynamic properties of extraventricular drainage systems.

OBJECTIVE: Extraventricular drains (EVDs) are intended to control intracranial pressure for patients with acute disorders of the cerebrospinal fluid circulation. We tested five commercially available EVDs to assess their fundamental hydrodynamic properties, which determine the quality of this control. METHODS: The five most frequently used drainage systems were tested. The pressure responses to water flow from a computer-controlled infusion pump were studied in the rig constructed in the UK Shunt Evaluation Laboratory (Cambridge, England). EVDs were studied under normal conditions and after brief (20-s) contact of the vent located in the drip chamber with the test reagent. Pure water and water with 10% rat blood content were used for testing. RESULTS: All of the tested EVDs demonstrated low hydrodynamic resistance [<3.5 mm Hg/(ml/min)], indicating their ability to control intracranial pressure. When the drip chamber vents were in brief contact with the reagent, the hydrodynamic properties of two models were unaffected. For the three other EVDs, blockage of the drip chamber was observed, leading to increases in the inlet pressure to more than 150 mm Hg. All three models that demonstrated obstruction have the same vent configuration, which allows cerebrospinal fluid to accumulate close to the filter when the drip chamber is held horizontally. This feature was confirmed to be the cause of the blockage. CONCLUSION: In clinical practice, special care should be taken to avoid contact of the drip chamber vents with cerebrospinal fluid, which causes obstruction and may lead to the development of gross intracranial hypertension. Specific configurations, as identified in this testing program, are safer than others in this respect.

Animals↗
PubMed2004

The hydrodynamic trails of Lepomis gibbosus (Centrarchidae), Colomesus psittacus (Tetraodontidae) and Thysochromis ansorgii (Cichlidae) investigated with scanning particle image velocimetry.

The hydrodynamic trails of fish belonging to the families Centrarchidae, Tetraodontidae and Cichlidae were investigated. Water movements were measured in six horizontal planes, spaced 10-12 mm apart, for up to 5 min after the passage of a fish, using a computer controlled array of modulated laser diodes. We measured continuously and non-continuously swimming fish. Water velocities decayed rapidly in the leading seconds after the passage of a fish, but could still be measured for a period considerably longer than that. In still water (median water velocity <0.5 mm s(-1)), the hydrodynamic trails of Lepomis gibbosus lasted for more than 5 min. The trails of Colomesus psittacus and Thysochromis ansorgii could be detected for more than 30 s and more than 3 min, respectively. The water disturbance left behind by these fish was sufficient to be sensed by a piscivorous predator at a distance where vision or hearing frequently fail. Acoustic stimuli estimated from a dipole model in a distance that would be covered by the tested fish in 1 min (4-25 m) were 1.5 x 10(-7) to 3.1 x 10(-10) m s(-2), while the hearing threshold of a perch is three orders of magnitude above that. By contrast, the fish wakes after 1 min (except for one Colomesus wake) contained water velocities between 0.95 and 2.05 mm s(-1), which are within the detection range of hydrodynamic sensory systems. The three species differed with respect to water velocities, the spatial extent of the fish-generated water disturbances and the structure of the wake.

Animals↗
PubMed2000

A hydrodynamic analysis of fish swimming speed: wake structure and locomotor force in slow and fast labriform swimmers.

Past study of interspecific variation in the swimming speed of fishes has focused on internal physiological mechanisms that may limit the ability of locomotor muscle to generate power. In this paper, we approach the question of why some fishes are able to swim faster than others from a hydrodynamic perspective, using the technique of digital particle image velocimetry which allows measurement of fluid velocity and estimation of wake momentum and mechanical forces for locomotion. We investigate the structure and strength of the wake in three dimensions to determine how hydrodynamic force varies in two species that differ markedly in maximum swimming speed. Black surfperch (Embiotoca jacksoni) and bluegill sunfish (Lepomis macrochirus) swim at low speeds using their pectoral fins exclusively, and at higher speeds switch to combined pectoral and caudal fin locomotion. E. jacksoni can swim twice as fast as similarly sized L. macrochirus using the pectoral fins alone. The pectoral fin wake of black surfperch at all speeds consists of two distinct vortex rings linked ventrally. As speed increases from 1.0 to 3.0 L s(-)(1), where L is total body length, the vortex ring formed on the fin downstroke reorients to direct force increasingly downstream, parallel to the direction of locomotion. The ratio of laterally to downstream-directed force declines from 0.93 to 0.07 as speed increases. In contrast, the sunfish pectoral fin generates a single vortex ring per fin beat at low swimming speeds and a pair of linked vortex rings (with one ring only partially complete and attached to the body) at maximal labriform speeds. Across a biologically relevant range of swimming speeds, bluegill sunfish generate relatively large lateral forces with the paired fins: the ratio of lateral to downstream force remains at or above 1.0 at all speeds. By increasing wake momentum and by orienting this momentum in a direction more favorable for thrust than for lateral force, black surfperch are able to swim at twice the speed of bluegill sunfish using the pectoral fins. In sunfish, without a reorientation of shed vortices, increases in power output of pectoral fin muscle would have little effect on maximum locomotor speed. We present two hypotheses relating locomotor stability, maneuverability and the structure of the vortex wake. First, at low speeds, the large lateral forces exhibited by both species may be necessary for stability. Second, we propose a potential hydrodynamic trade-off between speed and maneuverability that arises as a geometric consequence of the orientation of vortex rings shed by the pectoral fins. Bluegill sunfish may be more maneuverable because of their ability to generate large mediolateral force asymmetries between the left- and right-side fins.

Animals↗
PubMed2003

Hydrodynamic delivery of DNA.

Hydrodynamic delivery is an efficient and inexpensive procedure to deliver a wide range of nucleic acids to hepatic tissues and other organs in vivo. The successful application of hydrodynamic delivery is dependent on the rapid injection of a large aqueous volume containing DNA, RNA or other molecules into the vasculature of the liver. In this review, the development of the procedures for hydrodynamic delivery will be described and the parameters necessary for attaining maximal gene expression will be highlighted. A review of the mechanisms for transfecting hepatocytes, as well as potential uses of this approach in various research and clinical applications, will also be discussed.

Animals↗
PubMed2004

Neutrophil string formation: hydrodynamic thresholding and cellular deformation during cell collisions.

Neutrophils unexpectedly display flow-enhanced adhesion (hydrodynamic thresholding) to L-selectin in rolling or aggregation assays. We report that the primary collision efficiency (epsilon) of flowing neutrophils with preadhered neutrophils on intercellular adhesion molecule-1 (ICAM-1) or fibrinogen also displayed a maximum of epsilon approximately 0.4-0.45 at a wall shear rate of 100 s(-1), an example of thresholding. Primary collision lifetime with no detectable bonding decreased from 130 to 10 ms as wall shear rate increased from 30 to 300 s(-1), whereas collision lifetimes with bonding decreased from 300 to 100 ms over this shear range using preadhered neutrophils on ICAM-1, with similar results for fibrinogen. Antibodies against L-selectin, but not against CD11a, CD11b, or CD18, reduced epsilon at 100 s(-1) by >85%. High resolution imaging detected large scale deformation of the flowing neutrophil during the collision at 100 s(-1) with the apparent contact area increasing up to approximately 40 microm(2). We observed the formation of long linear string assemblies of neutrophils downstream of neutrophils preadhered to ICAM-1, but not fibrinogen, with a maximum in string formation at 100 s(-1). Secondary capture events to the ICAM-1 or fibrinogen coated surfaces after primary collisions were infrequent and short lived, typically lasting from 500 to 3500 ms. Between 5 and 20% of neutrophil interactions with ICAM-1 substrate converted to firm arrest (>3500 ms) and greatly exceeded that observed for fibrinogen, thus defining the root cause of poor string formation on fibrinogen at all shear rates. Additionally, neutrophils mobilized calcium after incorporation into strings. Static adhesion also caused calcium mobilization, as did the subsequent onset of flow. To our knowledge, this is the first report of 1). hydrodynamic thresholding in neutrophil string formation; 2). string formation on ICAM-1 but not on fibrinogen; 3). large cellular deformation due to collisions at a venous shear rate; and 4), mechanosensing through neutrophil beta(2)-integrin/adhesion. The increased contact area during deformation was likely responsible for the hydrodynamic threshold observed in the primary collision efficiency since no increase in primary collision lifetime was detected as shear forces were increased (for either surface coating).

CD11a Antigen↗
PubMed2004

The hydrodynamics of DNA electrophoretic stretch and relaxation in a polymer solution.

Theories of DNA electrophoretic separations generally treat the DNA as a free draining polymer moving in an electric field at a rate that depends on the effective charge density of the molecule. Separations can occur in sieving media ranging from ultradilute polymer solutions to tightly cross-linked gels. It has recently been shown that DNA is not free-draining when both electric and nonelectric forces simultaneously act on the molecule, as occurs when DNA collides with a polymer during electrophoretic separations. Here we show that a semidilute polymer solution screens the hydrodynamic interaction that results from the application of these forces. Fluorescently labeled DNA tethered at one end in a semidilute solution of hydroxyl-ethyl cellulose stretch more in an electric field than they stretch in free solution, and approach free-draining behavior. The steady stretching behavior is predicted without adjustable parameters by a theory developed by Stigter using a hydrodynamic screening length found from effective medium theory. Data on the relaxation of stretched molecules after the electric field is removed agree with the Rouse model prediction, which neglects hydrodynamic interactions. The slowest relaxation time constant, tau(R), scales with chain length as tau(R) approximately L(1.9+/-0.17) when analyzed by the data collapse method, and as tau(R) approximately L(2.17+/-0.17) when analyzed by multiexponential fit.

Cellulose↗
PubMed2006

Treatment of acute pulmonary embolism: local effects of three hydrodynamic thrombectomy devices in an ex vivo porcine model.

PURPOSE: To report an ex vivo study on the local effects of hydrodynamic thrombectomy for the treatment of acute pulmonary embolism (off-label use). METHODS: Three devices (6-F AngioJet Xpeedior and 6-F and 8-F Oasis) were used for hydrodynamic thrombectomy inside the arteries of 24 inflated and perfused porcine lung explants. Each system was used at multiple positions inside 4 intact and 4 embolized lungs in vessels measuring 2 to 4 mm, 4 to 6 mm, 6 to 8 mm, and 8 to 10 mm. Angiograms prior to, during, and after catheter positioning and system operation were used to detect arterial wall trauma and to measure local clot removal per 30-second cycle. A total of 21 vessel wall samples were subjected to scanning electron microscopy (SEM) to evaluate non-perforating lesions. RESULTS: All systems were able to remove clot material. The average recanalized vessel length normalized to 30 seconds for vessel diameters of 2 to 4 and 8 to 10 mm, respectively, was 1.17 and 1.75 cm (AngioJet), 0.97 and 0.25 cm (6-F Oasis), and 2.2 and 1.05 cm (8-F Oasis). Perforations occurred during positioning of the 6-F Oasis (4/78 maneuvers) and 8-F Oasis (13/60), but not the AngioJet (0/89); perforations were also seen during system operation (AngioJet: 21/89 activations, 6-F Oasis: 4/78, and 8-F Oasis: 9/60; all lesions inside vessels <6 mm in diameter). SEM showed 35 lesions, 14 with perforation (contrast extravasation) and 21 without perforation (induced by the tip of the guidewire). CONCLUSION: The AngioJet was most efficient in clot removal, followed by the 8-F Oasis. The 6-F Oasis was least efficient, but had fewest complications. According to these experiments, the tested hydrodynamic thrombectomy devices may cause perforations in vessels <6 mm in diameter. Changes in catheter design to reduce system-specific complication rates or to improve the efficacy of clot removal are warranted.

Acute Disease↗
PubMed2000

Role of hydrodynamic processes in the pathogenesis of peritumoral brain edema in meningiomas.

OBJECT: In a prospective study, 28 patients with 32 intracranial meningiomas were examined to determine the role of hydrodynamic interaction between tumor and surrounding brain tissue in the pathogenesis of peritumoral brain edema. METHODS: Gadolinium-diethylenetriamine pentaacetic acid (Gd-DPTA), an extracellular contrast agent used for routine clinical imaging, remains strictly extracellular without crossing an intact blood-brain barrier. Therefore, it is well suited for investigations of hydrodynamic extracellular mechanisms in the development of brain edema. Spin-echo T1-weighted magnetic resonance images were acquired before and after intravenous administration of 0.2 mmol/kg Gd-DPTA. Additional T1-weighted imaging was performed 0.6, 3.5, and 6.5 hours later. No significant Gd-DPTA diffused from tumor into peritumoral brain tissue in 12 meningiomas without surrounding brain edema. In contrast, in 17 of 20 meningiomas with surrounding edema, contrast agent in peritumoral brain tissue was detectable after 3.5 hours and 6.5 hours. In three of 20 meningiomas with minimum surrounding edema (<5 cm3), contrast agent effusion was absent. After 3.5 hours and 6.5 hours strong correlations of edema volume and the maximum distance of contrast spread from the tumor margin into adjacent brain parenchyma (r = 0.84 and r = 0.87, respectively, p < 0.0001) indicated faster effusion in larger areas of edema. CONCLUSIONS: The results of this study show that significant contrast agent effusion from the extracellular space of the tumor into the interstitium of the peritumoral brain tissue is only found in meningiomas with surrounding edema. This supports the hypothesis that hydrodynamic processes play an essential role in the pathogenesis of peritumoral brain edema in meningiomas.

Adult↗
PubMed2001

Cerebrospinal fluid hydrodynamics after placement of a shunt with an antisiphon device: a long-term study.

OBJECT: Few studies have been performed to investigate the cerebrospinal fluid (CSF) hydrodynamic profile in patients with idiopathic adult hydrocephalus syndrome (IAHS) before and after shunt implantation. The authors compared the in vivo CSF hydrodynamic properties, including the degree of gravity-induced CSF flow, of a shunt with an antisiphon device with a standard shunt. METHODS: Twelve patients with IAHS underwent insertion of shunts with Delta valves. Clinical testing, magnetic resonance imaging, and CSF hydrodynamic investigations were conducted with intracranial pressure (ICP), gravity effect, and pressure-flow curve of the shunt estimated at baseline and at 3 and 12 months postoperatively. No shunt was revised. Despite postoperative clinical improvement in all patients who received Delta valves, the mean ICP was only moderately reduced (mean decrease at 3 months 0.3 kPa [p = 0.02], at 12 months 0.2 kPa [not significant]). Patients with the greatest increase in ICP preoperatively had the most pronounced decrease postoperatively. The hydrostatic effect of the Delta valves was significantly lower than with the Hakim shunts (0.1-0.2 kPa compared with 0.6 kPa). The increased conductance (that is, lowered resistance) was up to 14 times higher with the Delta valves compared with preoperative levels. CONCLUSIONS: The function of a CSF shunt may be more complicated than previously thought; the subcutaneous pressure acting on the antisiphon device can modify the shunt characteristics. A compensatory increase in CSF production may counteract the increased outflow through the shunt. The improved CSF outflow conductance may increase the intracranial compliance and thereby dampen a pathological ICP waveform.

Aged↗
PubMedDate not supplied

Hydrodynamic properties of nucleosomal fibers and chromatin higher-order structure.

We studied the comparative hydrodynamic properties of chromatins differing in transcriptional activity and in linker DNA length. Chromatins were prepared from the nuclei of pigeon brain cortical neurones, rat thymus and sea urchin sperm. The sizes of linker DNA are 20, 50 and 100 base pairs (b.p.), respectively. Oligonucleosomes of different chain length were isolated from micrococcal nuclease-digested nuclei and studied by the method of sedimentation velocity. Rheological behavior of nucleosome oligomers depends on the number of nucleosomes in the chain and on the ionic strength in the range between 5 and 85 mM was analyzed on the basis of a cylinder model using different hydrodynamic theories. It is shown that hydrodynamic properties of oligonucleosomes from all types of investigated chromatins at low ionic strength can be well described by the model of a three-dimensional zig-zag chain with a diameter of about 20 nm, the DNA packing ratio growing with the increase of linker DNA length. Increasing ionic strength induces condensation of the zig-zag-shaped chain of nucleosomes into a two-start double superhelix with densely packed nucleosomes. Linkers are arranged inside the superhelix, which is bent or folded into a loop, depending on its size.

Animals↗
PubMedDate not supplied

Application of spatial modulation of magnetization to cervical spinal stenosis for evaluation of the hydrodynamic changes occurring in cerebrospinal fluid.

OBJECTIVE: To evaluate the hydrodynamic changes occurring in cerebrospinal fluid (CSF) flow in cervical spinal stenosis using the spatial modulation of magnetization (SPAMM) technique. MATERIALS AND METHODS: Using the SPAMM technique, 44 patients with cervical spinal stenosis and ten healthy volunteers were investigated. The degree of cervical spinal stenosis was rated as low-, intermediate-, or high-grade. Lowgrade stenosis was defined as involving no effacement of the subarachnoid space, intermediate-grade as involving effacement of this space, and high-grade as involving effacement of this space, together with compressive myelopathy. The patterns of SPAMM stripes and CSF velocity were evaluated and compared between each type of spinal stenosis and normal spine. RESULTS: Low-grade stenosis (n = 23) revealed displacement or discontinuity of stripes, while intermediate- (n = 10) and high-grade (n = 11) showed a continuous straight band at the stenotic segment. Among low-grade cases, 12 showed wave separation during the systolic phase. Peak systolic CSF velocity at C4-5 level in these cases was lower than in volunteers (p <.05), but jet-like CSF propulsion was maintained. Among intermediate-grade cases, peak systolic velocity at C1-2 level was lower than in the volunteer group, but the difference was not significant (p >.05). In high-grade stenosis, both diastolic and systolic velocities were significantly lower (p <.05). CONCLUSION: Various hydrodynamic changes occurring in CSF flow in cervical spinal stenosis were demonstrated by the SPAMM technique, and this may be a useful method for evaluating CSF hydrodynamic change in cervical spinal stenosis.

Cervical Vertebrae↗
PubMed1999

The new St. Jude Medical regent mechanical heart valve: laboratory measurements of hydrodynamic performance.

BACKGROUND AND AIM OF THE STUDY: The St. Jude Medical (SJM) mechanical heart valve was the first bileaflet valve with leaflets and orifice all fabricated from pyrolytic carbon. In 1992, a supra-annular cuff configuration, the SJM mechanical heart valve Hemodynamic Plus Series (HP), was introduced, which gave a one-size gain in orifice area over the standard valve. In a continuing effort to improve hydrodynamic performance, a new enhanced configuration of the mechanical valve - the SJM Regent valve - has been developed. The blood-contacting components of the SJM Regent valve have the same design features as those of the standard or HP valve, but the orifice lumen area has been increased, without compromising structural integrity, by a shift in the cuff-retaining orifice rims. METHODS: Valve performance has been measured using a laboratory simulation of the left heart system. Three samples of both valve types (SJM Regent, HP) for sizes 17 mm to 27 mm, were tested at a cardiac output of 5 l/min. Supplementary steady-flow measurements were made at flow rates between 5 and 30 l/min. Pressure and flow signals were recorded and several performance parameters, including pressure gradient, effective orifice area (EOA), insufficiency (regurgitant volume as a percent of forward flow volume) and energy loss, were computed. RESULTS: All sizes of the SJM Regent valve showed improved hydrodynamic performance compared with the HP valve. For the small sizes (17, 19, 21 mm), the pressure gradient of the SJM Regent decreased by 37%, 36% and 39%, respectively; the EOA increased by 22%, 22% and 21%; and the total transaortic energy loss decreased by 33%, 31% and 31% compared with the HP valve. The regurgitation for both valves ranged between 4% and 8% of forward flow volume over the 17-27 mm size range. CONCLUSIONS: Hydrodynamic measurements confirm the gain of the SJM Regent valve over the HP valve that is expected based on the increased geometric orifice area. Given its basic similarity of design, but with an increased EOA as demonstrated in vitro, the SJM Regent valve is anticipated to provide an increased level of clinical benefit.

Biocompatible Materials↗
PubMedDate not supplied

[Experimental study of the hydrodynamics of modern artificial heart valves].

The paper presents the results of experimental studies of the hydrodynamics of currently available artificial cardiac valves (ACV). Photo chromatographic visualization was used to study the hydrodynamics of ACV. The hydrodynamic characteristics of a MIX discal valve (Russia) and a St. Jude two-leaflet one (USA), which have been clinically applied for more than 15 years, are presented.

Equipment Design↗