共查询到13条相似文献,搜索用时 0 毫秒
1.
New dynamic particle image velocimetry (PIV) technology was applied to the study of the flow field associated with prosthetic
heart valves. Four bileaflet prostheses, the St. Jude Medical (SJM) valve, the On-X valve with straight leaflets, the Jyros
(JR) valve, and the Edwards MIRA (MIRA) valve with curved leaflets, were tested in the mitral position under pulsatile flow
conditions to find the effect of the leaflet shape and overall valve design on the flow field, particularly in terms of the
turbulent stress distribution, which may influence hemolysis, platelet activation, and thrombus formation. Comparison of the
time-resolved flow fields associated with the opening, accelerating, peak, and closing phases of the diastolic flow revealed
the effects of the leaflet shape and overall valve design on the flow field. Anatomically and antianatomically oriented bileaflet
valves were also compared in the mitral position to study the effects of the orientation on the downstream flow field. The
experimental program used a dynamic PIV system utilizing a high-speed, high-resolution video camera to map the true time-resolved
velocity field inside the simulated ventricle. Based on the experimental data, the following general conclusions can be made.
High-resolution dynamic PIV can capture true chronological changes in the velocity and turbulence fields. In the vertical
measuring plane that passes the centers of both the aortic and mitral valves (A-A section), bileaflet valves show clear and
simple circulatory flow patterns when the valve is installed in the antianatomical orientation. The SJM, the On-X, and the
MIRA valves maintain a relatively high velocity through the central orifice. The curved leaflets of the JR valve generate
higher velocities with a divergent flow during the accelerating and peak flow phases when the valve is installed in the anatomical
orientation. In the velocity field directly below the mitral valve and normal to the previous measuring plane (B-B section),
where characteristic differences in valve design on the three-dimensional flow should be visible, the symmetrical divergent
nature of the flow generated by the two inclined half-disks installed in the antianatomical orientation was evident. The SJM
valve, with a central downward flow near the valve, is contrasted with the JR valve, which has a peripherally strong downward
circulation with higher turbulent stresses. The On-X valve has a strong central downward flow attributable to its large opening
angle and flared inlet shape. The MIRA valve also has a relatively strong downward central flow. The MIRA valve, however,
diverts the flow three-dimensionally due to its peripherally curved leaflets. 相似文献
2.
Toshinosuke Akutsu Jun Saito Ryota Imai Tomoyuki Suzuki Xiu Dong Cao 《Journal of artificial organs》2008,11(2):75-90
The characteristics of mechanical bileaflet valves, the leaflets of which open at the outside first, differ significantly from those of natural valves, whose leaflets open at the center first, and this fact affects the flow field down-stream of the valves. The direction of jet-type flows, which is influenced by this difference in valve features, and the existence of the sinus of Valsalva both affect the flow field inside the aorta in different ways, depending on the valve design. There may also be an influence on the coronary circulation, the entrance to which resides inside the sinus of Valsalva. A dynamic particle image velocimetry (PIV) study was conducted to analyze the influence of the design of prosthetic heart valves on the aortic flow field. Three contemporary bileaflet prostheses, the St. Jude Medical (SJM) valve, the On-X valve (with straight leaflets), and the MIRA valve (with curved leaflets), were tested inside a simulated aorta under pulsatile flow conditions. A dynamic PIV system was employed to analyze the aortic flow field resulting from the different valve designs. The two newer valves, the On-X and the MIRA valves, open more quickly than the SJM valve and provide a wider opening area when the valve is fully open. The SJM valve's outer orifices deflect the flow during the accelerating flow phase, whereas the newer designs deflect the flow less. The flow through the central orifice of the SJM valve has a lower velocity compared to the newer designs; the newer designs tend to have a strong flow through all orifices. The On-X valve generates a simple jet-type flow, whereas the MIRA valve (with circumferentially curved leaflets) generates a strong but three-dimensionally diffuse flow, resulting in a more complex flow field downstream of the aortic valve. The clinically more adapted 180 degrees orientation seems to provide a less diffuse flow than the 90 degrees orientation does. The small differences in leaflet design in the bileaflet valves generate noticeable differences in the aortic flow; the newer valves show strong flows through all orifices. 相似文献
3.
Toshinosuke Akutsu PhD Ryota Imai BE Yuuki Deguchi BS 《Journal of artificial organs》2005,8(3):161-170
Antianatomically installed Jyros (JR) and ATS valves were compared with the St. Jude Medical (SJM) valve in the mitral position
to study the effects of valve design on the downstream flow field and associated closing sounds using a particle image velocimetry
(PIV) method utilizing a high-speed video flow visualization technique to map the velocity field and sound measurement to
confirm claims by the manufacturer. Based on the experimental data, the following general conclusions can be made: in the
velocity field directly below the mitral valve, where distinct characteristic differences in valve design can be seen, symmetrical
twin circulations were observed because of the divergent nature of the flow generated by the two inclined half-disks installed
in the antianatomical orientation; the SJM valve, which produced central downward circulation, is contrasted to the two other
valves, which produced peripheral downward circulation. These differences may play an important role in the closing behavior
of the valve leaflets, thus affecting the generation of the valve closing sound. 相似文献
4.
The Jyros (JR) and the Advancing The Standard (ATS) valves were compared with the St. Jude Medical (SJM) valve in the mitral
position to study the effects of design differences, installed valve orientation to the flow, and closing sounds using particle
tracking velocimetry and particle image velocimetry methods utilizing a high-speed video flow visualization technique to map
the velocity field. Sound measurements were made to confirm the claims of the manufacturers. Based on the experimental data,
the following general conclusions can be made: On the vertical measuring plane which passes through the centers of the aortic
and the mitral valves, the SJM valve shows a distinct circulatory flow pattern when the valve is installed in the antianatomical
orientation; the SJM valve maintains the flow through the central orifice quite well; the newer curved leaflet JR valve and
the ATS valve, which does not fully open during the peak flow phase, generates a higher but divergent flow close to the valve
location when the valve was installed anatomically. The antianatomically installed JR valve showed diverse and less distinctive
flow patterns and slower velocity on the central measuring plane than the SJM valve did, with noticeably lower valve closing
noise. On the velocity field directly below the mitral valve that is normal to the previous measuring plane, the three valves
show symmetrical twin circulations due to the divergent nature of the flow generated by the two inclined half discs; the SJM
valve with centrally downward circulation is contrasted by the two other valves with peripherally downward circulation. These
differences may have an important role in generation of the valve closing sound.
Received: October 3, 2002 / Accepted: March 18, 2003 相似文献
5.
Two groups of typical contemporary mechanical heart valves, the Advancing the Standard (ATS) and the Carbomedics (CM) valve
(of bileaflet design) and the Bjork-Shiley (BS) mono and Bicer-Val (BV) valves (of tilting-disc design), were tested in the
mitral position under the pulsatile-flow condition. This study extends a previous report studying the effect of orientation
of the St. Jude Medical (SJM) valve, representing bilcaflet valve design, and the Meditronic-Hall (MH) valve, representing
mono-leaflet valve design. The test program utilized a flow visualization technique to map the velocity field inside the simulated
ventricle. The study was carried out using a sophisticated cardiac simulator in conjunction with a high-speed video system
(200 frames·s−1). The continuous monitoring of velocity-vector time histories revealed useful details about the complex flow and helped establish
the locations and times of the peak parameter values. Comparison of the velocity profiles at corresponding flow phases reveals
the effects of the differences in valve design and orientation. Based on precise examination of the data, the following general
conclusions can be made: pulsatile flow creates three distinct flow phases consisting of accelerating, peak, and decelerating
flow; the bileaflet CM and ATS valves in the antianatomical orientation generally create a single, large circulatory flow;
the ATS valve scems to offer smoother flow patterns, similar to the SJM valve; and the monoleaflet BV valve and the BS monostrut
valve seem to affect the flow characteristics more dramatically, with the posterior orientation exhibiting simple and stable
circulatory flow. 相似文献
6.
Ever since the first introduction of the ball-type valve by Hufnagel in 1952, which was installed in the descending aorta
to correct aortic valve insufficiency, great efforts have been aimed to produce a hemodynamically and structurally superior
prosthetic heart valve. Bileaflet valves, commercially initiated by the St. Jude medical (SJM) valve, perform satisfactorily,
and now the majority of the mechanical-type prosthetic heart valves used clinically are of this type. The recent trend in
bileaflet valve design seems to be concentrated on the hinge mechanism and leaflet design to improve performance against thromboembolic
complications and hemolysis. This paper studied the effects of hinge location, leaflet configuration, valve opening angle,
and valve installed orientation to the flow field inside the simulated ventricle using laser Doppler anemometry. As a model
prosthetic valve, the SJM valve was selected as a reference, and newer bileaflet valves, including the ATS, the Carbomedics
(CM), and the Jyros (JR) valves, were selected for comparison. The test program also utilized a flow visualization technique
to map the velocity field inside the simulated ventricle to complement the information obtained using the LDA system. Comparison
of the velocity profiles at corresponding flow phases revealed the effects of the differences in valve design and orientation.
Based on precise examination of the data, the following general conclusions can be made: all valves (SJM, ATS, CM, and JR)
show distinct circulatory flow patterns when the valve is installed in the antianatomical orientation. The small differences
in hinge location and leaflet configuration can generate noticeable differences, particularly during the accelerating flow
phase of the valve. The ATS and the CM valves open less during the forward flow phase, and this results in generally diverse
and less distinct flow patterns and slower velocity. This is particularly noticeable for the flow through the central orifice.
The SJM valve maintains a relatively higher velocity through the central orifice. The curved leaflet JR valve generates higher
but divergent flow during the accelerating and peak flow phases. 相似文献
7.
Toshinosuke Akutsu Ryota Imai Jun Saito Tomoyuki Suzuki 《Journal of artificial organs》2008,11(2):67-74
The Jyros (JR) valve and the newer On-X and MIRA valves, all installed antianatomically, were compared with the St. Jude Medical (SJM) valve in the mitral position to study the effects of valve design differences on the down-stream flow field and the associated valve closing sound. The dynamic particle image velocimetry method utilizing a high-speed video flow visualization technique was used to map the velocity field, and wavelet analysis of the sound was used to find the correlation between the ventricular flow field and the valve closing sound. Based on the experimental data, the following general conclusions can be made. In the velocity field directly below the mitral valve, where the distinct characteristic differences of the valve designs will be evident, twin symmetrical circulations were observed due to the divergent nature of the flow generated by the two inclined half-disks with the valve installed in the anti-anatomical orientation; the SJM, the On-X, and the MIRA valves generated a centrally downward circulation that opposed the valve leaflet closing movement, and resulted in relatively loud valve closing sounds. 相似文献
8.
Two typical contemporary mechanical heart valves, with different designs (St. Jude Medical and Medtronic-Hall), were tested in the mitral position under pulsatile flow conditions. The test program used the flow visualization technique to map the velocity field inside the simulated ventricle. The study was carried out using a sophisticated cardiac simulator in conjunction with a highspeed video system (200 frames/s). The continuous monitoring of velocity vector time histories revealed useful details about the complex flow and helped establish the location and time of the peak parameter values. We conclude that (1) the SJM valve with antianatomical position creates a large single circulatory flow; and (2)the configuration of the MH valve seems to affect the flow characteristics more dramatically, and the posterior orientation exhibits a simple and stable circulatory flow. 相似文献
9.
Hwansung Lee Yoshiaki Ikeuchi Eiki Akagawa Eisuke Tatsumi Yoshiyuki Taenaka Takao Yamamoto 《Journal of artificial organs》2009,12(2):98-104
Our group is currently developing a pneumatic ventricular assist device (PVAD). In this study, in order to select the optimal
bileaflet valve for our PVAD, three kinds of bileaflet valve were installed and the flow was visualized downstream of the
outlet valve using the particle image velocimetry (PIV) method. To carry out flow visualization inside the blood pump and
near the valve, we designed a model pump that had the same configuration as our PVAD. The three bileaflet valves tested were
a 21-mm ATS valve, a 21-mm St. Jude valve, and a 21-mm Sorin Bicarbon valve. The mechanical heart valves were mounted at the
aortic position of the model pump and the flow was visualized by using the PIV method. The maximum flow velocity was measured
at three distances (0, 10, and 30 mm) from the valve plane. The maximum flow velocity of the Sorin Bicarbon valve was less
than that of the other two valves; however, it decreased slightly with increasing distance it the X-Y plane in all three valves.
Although different bileaflet valves are very similar in design, the geometry of the leaflet is an important factor when selecting
a mechanical heart valve for use in an artificial heart. 相似文献
10.
Richard S. Meyer Steven Deutsch Juan-Carlos Maymir David B. Geselowitz John M. Tarbell 《Annals of biomedical engineering》1997,25(6):1081-1091
Three-dimensional laser Doppler velocimetry measurements were acquired in a mock-circulatory loop proximal to a Björk-Shiley monostrut valve in the mitral position, and synchronous ensemble-averaging was applied to form an “average” beat. Two axial locations in the regurgitant flow region of the valve (in the minor orifice) were mapped, and maximum Reynolds shear stresses were calculated. A large spike in regurgitant flow was noted at the beginning of systole, which may be thesqueeze flow phenomenon computed by other researchers. A region of sustained regurgitant flow 50 msec later was the focus of this study. Maximum velocities of ~3.7 mps were noted, and maximum Reynolds shear stresses of ~10,000 dyne/cm2 were calculated. Comparisons were made of two-dimensional (ignoring tangential component)versus three-dimensional shear stresses, and, in this case, in regions of high stress, the differences were insignificant. This suggests that the tangential component of velocity can probably be ignored in similar measurements where the tangential velocity is likely to be small. 相似文献
11.
The spiral vortex pump (SV), an innovative, penumatically driven ventricular assist device, was tested using the flow visualization
technique and laser Doppler anemometry to study the effect of inlet valve orientation under steady and pulsatile flow conditions
in a purposely constructed flow circuit aimed at obtaining flow field data. Qualitative information was obtained using the
flow visualization technique. The slit-lighting technique and fluorescent bees provided a clear flow field view at the desired
location, and a 200 frames/s high-speed video camera was used, capturing the vortex nature of the flow field. Mean velocity
and fluctuating velocity profile were obtained using a Kanomax single-channel FLV system. Three diametrically transverse locations
and three vertical locations were selected for measurements. The particle-tracking method was also incorporated to obtain
velocity vectors. Based on the experimental data, the following general conclusions can be drawn: (1) The SV pump created
a vortex flow field under steady and pulsatile flow conditions. (2) The inlet valve orientation sharply influenced the flow
inside the SV pump. (3) A relatively strong circulatory flow field was observed when the major orifice was oriented toward
the HD junction under steady flow. (4) A relatively weak circulatory flow field was observed when the major orifice was oriented
toward the center under steady flow. (5) The directional flow field was more accentuated under pulsatile flow conditions.
(6) A relatively stable flow field was observed when the major orifice was oriented upward (pump outlet direction). (7) Directional
flow toward the diaphragm was observed when the major orifice was oriented downward. (8) A strong circulatory flow with possible
colliding flow toward the peripheral area was observed when the major orifice was oriented outward. (9) A relatively weak
circulatory flow was observed when the major orifice was oriented inward. (10) The strength of the circulatory flow during
the peak flow phase under pulsatile conditions was not affected by the orientation of the inlet valve. 相似文献
12.
Eiki Akagawa PhD Hwansung Lee PhD Eisuke Tatsumi MD PhD Akihiko Homma PhD Tomonori Tsukiya PhD Nobumasa Katagiri MS Yukihide Kakuta BE Tomohiro Nishinaka MD PhD Toshihide Mizuno DVM PhD Kei Ota MD Rei Kansaku MD Yoshiyuki Taenaka MD PhD 《Journal of artificial organs》2007,10(2):85-91
We have been developing a pneumatic ventricular assist device (PVAD) system consisting of a diaphragm-type blood pump. The
objective of the present study was to evaluate the flow pattern inside the PVAD, which may greatly affect thrombus formation,
with respect to the inflow valve-mount orientation. To analyze the change of flow behavior caused by the orifice direction
(OD) of the valve, the flow pattern in this pump was visualized. Particle image velocimetry was used as a measurement technique
to visualize the flow dynamics. A monoleaflet mechanical valve was mounted in the inlet and outlet ports of the PVAD, which
was connected to a mock circulatory loop tester. The OD of the inlet valve was set at six different angles (OD = 0°, 45°,
90°, 135°, 180°, and 270°, where the OD opening toward the diaphragm was defined as 0°) and the pump rate was fixed at 80 bpm
to create a 5.0 l/min flow rate. The main circular flow in the blood pump was affected by the OD of the inlet valve. The observed
regional flow velocity was relatively low in the area between the inlet and outlet port roots, and was lowest at an OD of
90°. In contrast, the regional flow velocity in this area was highest at an OD of 135°. The OD is an important factor in optimizing
the flow condition in our PVAD in terms of preventing flow stagnation, and the best flow behavior was realized at an OD of
135°. 相似文献
13.
Yos Morsi PhD. FIEAust Masahisa Kogure MEng Mitsuo Umezu PhD 《Journal of artificial organs》1999,2(1):62-73
Thrombus formation and hemolysis have both been linked to the dynamic flow characteristics of heart valve prostheses. To enhance our understanding of the flow characteristics past the mitral position of a jellyfish (JF) valve in the left ventricle under physiological pulsatile flow conditions, in vitro laser Doppler anemometry (LDA) measurements were carried out. The hydrodynamic performance of the JF valve was compared with that of a Bjork-Shiley tilting-disk valve (BS mono). The results indicated that both valves created disturbed flow fields and turbulence shear stress levels in the immediate vicinity and up to 1D (diameter of the valvering) downstream from the valve that were capable of causing lethal damage to blood elements. At a location further downstream, the JF valve showed better hydrodynamic performance than the BS in terms of back flow properties and velocity and turbulence stress characteristics. However, any imperfection in the manufacturing of the valve structure, particularly membrane thickness, adversely affected the performance of the JF valve. 相似文献