scholarly journals Effects of Bileaflet Mechanical Mitral Valve Rotational Orientation on Left Ventricular Flow Conditions

2015 ◽  
Vol 9 (1) ◽  
pp. 62-68 ◽  
Author(s):  
John C Westerdale ◽  
Ronald Adrian ◽  
Kyle Squires ◽  
Hari Chaliki ◽  
Marek Belohlavek
Keyword(s):  
Velocity Field ◽  
Measurement Techniques ◽  
Angular Position ◽  
Mechanical Heart Valve ◽  
Mechanical Valve ◽  
Left Ventricular ◽  
Shear Stresses ◽  
Elastic Model ◽  
Intraventricular Flow ◽  
Particle Imaging

We studied left ventricular flow patterns for a range of rotational orientations of a bileaflet mechanical heart valve (MHV) implanted in the mitral position of an elastic model of a beating left ventricle (LV). The valve was rotated through 3 angular positions (0, 45, and 90 degrees) about the LV long axis. Ultrasound scans of the elastic LV were obtained in four apical 2-dimensional (2D) imaging projections, each with 45 degrees of separation. Particle imaging velocimetry was performed during the diastolic period to quantify the in-plane velocity field obtained by computer tracking of diluted microbubbles in the acquired ultrasound projections. The resulting velocity field, vorticity, and shear stresses were statistically significantly altered by angular positioning of the mechanical valve, although the results did not show any specific trend with the valve angular position and were highly dependent on the orientation of the imaging plane with respect to the valve. We conclude that bileaflet MHV orientation influences hemodynamics of LV filling. However, determination of ‘optimal’ valve orientation cannot be made without measurement techniques that account for the highly 3-dimensional (3D) intraventricular flow.

Intraventricular flow visualization in different heart failure stages with blood pump support in a mock circulatory loop

2021 ◽  
pp. 039139882110214
Author(s):  
Guang-Mao Liu ◽  
Fu-Qing Jiang ◽  
Jiang-Ping Song ◽  
Sheng-Shou Hu
Keyword(s):  
Heart Failure ◽  
Standard Deviation ◽  
Aortic Valve ◽  
Left Ventricle ◽  
Left Ventricular ◽  
Blood Pump ◽  
Blood Damage ◽  
Intraventricular Flow ◽  
Pump Inlet ◽  
Strong Vorticity

The intraventricular blood flow changed by blood pump flow dynamics may correlate with thrombosis and ventricular suction. The flow velocity, distribution of streamlines, vorticity, and standard deviation of velocity inside a left ventricle failing to different extents throughout the cardiac cycle when supported by an axial blood pump were measured by particle image velocimetry (PIV) in this study. The results show slower and static flow velocities existed in the central region of the left ventricle near the mitral valve and aortic valve and that were not sensitive to left ventricular (LV) failure degree or LV pressure. Strong vorticity located near the inner LV wall around the LV apex and the blood pump inlet was not sensitive to LV failure degree or LV pressure. Higher standard deviation of the blood velocity at the blood pump inlet decreased with increasing LV failure degree, whereas the standard deviation of the velocity near the atrium increased with increasing intraventricular pressure. The experimental results demonstrated that the risk of thrombosis inside the failing left ventricle is not related to heart failure degree. The “washout” performance of the strong vorticity near the inner LV wall could reduce the thrombotic potential inside the left ventricle and was not related to heart failure degree. The vorticity near the aortic valve was sensitive to LV failure degree but not to LV pressure. We concluded that the risk of blood damage caused by adverse flow inside the left ventricle decreased with increasing LV pressure.

scholarly journals Mechanics of intraventricular filling: study of LV early diastolic pressure gradients and flow velocities

1998 ◽  
Vol 275 (3) ◽  
pp. H1062-H1069 ◽  
Author(s):  
Otto A. Smiseth ◽  
Kjetil Steine ◽  
Gunnar Sandbæk ◽  
Marie Stugaard ◽  
Tor Ø. Gjølberg
Keyword(s):  
Pressure Gradient ◽  
Diastolic Pressure ◽  
Time Derivative ◽  
Left Ventricular ◽  
Outflow Tract ◽  
Transmitral Flow ◽  
Intraventricular Flow ◽  
Artery Disease ◽  
Lv Volume ◽  
Flow Velocities

This study investigates mechanisms of left ventricular (LV) intracavitary flow during early, rapid filling. In eight coronary artery disease patients with normal LV ejection fraction we recorded simultaneous LV apical and outflow tract pressures and intraventricular flow velocities by color M-mode Doppler echocardiography. In five anesthetized dogs we also recorded left atrial pressure and LV volume by sonomicrometry. In patients, as the early diastolic mitral-to-apical filling wave arrived at the apex, we observed an apex-outflow tract pressure gradient of 3.5 ± 0.3 mmHg (mean ± SE). This pressure gradient correlated with peak early apex-to-outflow tract flow velocity ( r = 0.75, P < 0.05). The gradient was reproduced in the dog model and decreased from 3.1 ± 0.3 to 1.7 ± 0.5 mmHg ( P < 0.05) with caval constriction and increased to 4.2 ± 0.5 mmHg ( P < 0.001) with volume loading. The pressure gradient correlated with peak early transmitral flow (expressed as time derivative of LV volume; r = 0.95) and stroke volume ( r = 0.97). In conclusion, arrival of the early LV filling wave at the apex was associated with a substantial pressure gradient between apex and outflow tract. The pressure gradient was sensitive to changes in preload and correlated strongly with peak early transmitral flow. The significance of this gradient for intraventricular flow propagation in the normal and the diseased heart remains to be determined.

Laser Velocimeter Measurements in the Turbine of an Automotive Torque Converter: Part II—Unsteady Measurements

1997 ◽  
Vol 119 (3) ◽  
pp. 655-662 ◽  
Author(s):  
K. Brun ◽  
R. D. Flack
Keyword(s):  
Velocity Field ◽  
Turbine Blades ◽  
Angular Position ◽  
Torque Converter ◽  
Speed Ratio ◽  
Velocity Data ◽  
Velocity Fluctuations ◽  
Blade Passage ◽  
Turbine Pump ◽  
Output Torque

The unsteady velocity field found in the turbine of an automotive torque converter was measured using laser velocimetry. Velocities in the inlet, quarter, mild, and exit planes of the turbine were investigated at two significantly different turbine/pump rotational speed ratios: 0.065 and 0.800. A data organization method was developed to visualize the three-dimensional, periodic unsteady velocity field in the rotating frame. For this method, the acquired data are assumed to be periodic at synchronous and blade interaction frequencies. Two shaft encoders were employed to obtain the instantaneous angular position of the torque converter pump and turbine at the instant of laser velocimeter data acquisition. By proper “registration” of the velocity data, visualizing the transient interaction effects between the turbine, pump, and stator was possible. Results showed strong cyclic velocity fluctuations in the turbine inlet plane as a function of the relative turbine-pump position. These fluctuations are due to the passing of upstream pump blades by the slower rotating turbine blades. Typical fluctuations in the through flow velocity were 3.6 m/s. Quarter and midplane velocity fluctuations were seen to be lower; typical values were 1.5 m/s and 0.8 m/s, respectively. The flow field in the turbine exit plane was seen to be relatively steady with negligible fluctuations of less than 0.03 m/s. From the velocity data, the fluctuations of turbine performance parameters such as flow inlet angles, root-mean-square unsteadiness, and output torque per blade passage were calculated. Incidence angles were seen to vary by 3 and 6 deg for the 0.800 and 0.065 speed ratios, respectively, while the exit angles remained steady. The turbine output torque per blade passage fluctuated by 0.05 Nm for the 0.800 speed ratio and 0.13 Nm for the 0.065 speed ratio.

scholarly journals Characteristics and long-term outcomes of aortico-left ventricular tunnel

2020 ◽  
Author(s):  
Jing Sun ◽  
Hongxia Qi ◽  
Hongyuan Lin ◽  
Wenying Kang ◽  
Shoujun Li ◽  
...  
Keyword(s):  
Aortic Valve ◽  
Valve Replacement ◽  
Surgical Repair ◽  
Mechanical Valve ◽  
Left Ventricular ◽  
Ascending Aorta ◽  
Aortic Orifice ◽  
The Right

Abstract OBJECTIVES Aortico-left ventricular tunnel (ALVT) is an extremely rare, abnormal paravalvular communication between the aorta and the left ventricle. Few studies have identified the characteristics and long-term prognosis associated with ALVT. METHODS The data of 31 patients with ALVT from July 2002 to December 2019 were reviewed. Echocardiography was performed in all patients during the follow-up period. RESULTS The median age of the patients was 11.5 years. Bicuspid aortic valve and dilatation of the ascending aorta were found in 13 patients, respectively. The aortic orifice in 20 patients showed a close relation to the right sinus and the right–left commissure. Of the 31 patients, 26 were operated on. Mechanical valve replacement was performed in 4 patients and aortic valve repair, in 6 patients. Ascending aortoplasty was performed in 5 patients and aortic replacement was done in 2 patients. One patient died of ventricular fibrillation before the operation. Follow-up of the remaining 30 patients ranged from 1 to 210 months (median 64 months). There were 4 deaths during the follow-up period: 1 had mechanical valve replacement and 3 did not undergo surgical repair. In the 26 patients without aortic valve replacement, 6 had severe regurgitation and 2 had moderate regurgitation. In the 28 patients without replacement of the ascending aorta, 11 had continued dilatation of the ascending aorta, including those who had aortoplasty. CONCLUSIONS The aortic orifice of ALVT showed an association with the right sinus and the right–left commissure. For patients who did not have surgery, the long-term survival rate remained terrible. Surgical closure should be done as soon as possible after ALVT is diagnosed. The main long-term complications after surgical repair included aortic regurgitation and ascending aortic dilatation.

scholarly journals Anticoagulation for the Pregnant Patient with a Mechanical Heart Valve, No Perfect Therapy: Review of Guidelines for Anticoagulation in the Pregnant Patient

2017 ◽  
Vol 2017 ◽  
pp. 1-5 ◽  
Author(s):  
Aaron Richardson ◽  
Stuart Shah ◽  
Ciel Harris ◽  
Garry McCulloch ◽  
Patrick Antoun
Keyword(s):  
Heart Valve ◽  
Thrombotic Event ◽  
Alternative Therapy ◽  
Mechanical Heart Valve ◽  
Mechanical Valve ◽  
Pregnant Patient ◽  
First Trimester ◽  
Subsequent Pregnancy ◽  
Mechanical Valves ◽  
Increased Risk

Heart valve replacement with a mechanical valve requires lifelong anticoagulation. Guidelines currently recommend using a vitamin K antagonist (VKA) such as warfarin. Given the teratogenic effects of VKAs, it is often favorable to switch to heparin-derived therapies in pregnant patients since they do not cross the placenta. However, these therapies are known to be less effective anticoagulants subjecting the pregnant patient to a higher chance of a thrombotic event. Guidelines currently recommend pregnant women requiring more than 5 mg a day of warfarin be switched to alternative therapy during the first trimester. This case report highlights a patient who was switched to alternative therapy during her first pregnancy and suffered a devastating cerebrovascular accident (CVA). Further complicating her situation was during a subsequent pregnancy; this patient continued warfarin use during the first trimester and experienced multiple transient ischemic attacks (TIAs). This case highlights the increased risk of thrombotic events in pregnant patients with mechanical valves. It also highlights the difficulty of providing appropriate anticoagulation for the pregnant patient who has experienced thrombotic events on multiple anticoagulants.

Patient-Specific Approach to Mitral Valve Replacement in Infants Weighing 10 kilograms or less

2019 ◽  
Vol 10 (3) ◽  
pp. 304-312
Author(s):  
Kathryn Mater ◽  
Julian Ayer ◽  
Ian Nicholson ◽  
David Winlaw ◽  
Richard Chard ◽  
...  
Keyword(s):  
Mitral Valve ◽  
Valve Replacement ◽  
Mitral Valve Replacement ◽  
Surgical Techniques ◽  
Somatic Growth ◽  
Mechanical Valve ◽  
Left Ventricular ◽  
Patient Specific ◽  
Mechanical Prostheses

Background: Mitral valve replacement (MVR) is the only option for infants with severe mitral valve disease that is not reparable; however, previously reported outcomes are not always favorable. Our institution has followed a tailored approach to sizing and positioning of mechanical valve prostheses in infants requiring MVR in order to obtain optimal outcomes. Methods: Outcomes for 22 infants ≤10 kg who have undergone MVR in Sydney, Australia, from 1998 to 2016, were analyzed. Patients were at a mean age of 6.8 ± 4.1 months (range: 0.8-13.2 months) and a mean weight of 5.4 ± 1.8 kg at the time of MVR. Most patients (81.8%) had undergone at least one previous cardiac surgical procedure prior to MVR, and 36.4% had undergone two previous procedures. Several surgical techniques were used to implant mechanical bileaflet prostheses. Results: All patients received bileaflet mechanical prostheses, with 12 receiving mitral prostheses and 10 receiving inverted aortic prostheses. Surgical technique varied between patients with valves implanted intra-annularly (n = 6), supra-annularly (n = 11), or supra-annularly with a tilt (n = 5). After a mean follow-up period of 6.2 ± 4.4 years, the survival rate was 100%. Six (27.3%) patients underwent redo MVR a mean of 102.2 ± 10.7 months after initial MVR. Four (18.2%) patients required surgical reintervention for development of left ventricular outflow tract obstruction and three (13.6%) patients required permanent pacemaker placement during long-term follow-up. Conclusions: The tailored surgical strategy utilized for MVR in infants at our institution has resulted in reliable valve function and excellent survival. Although redo is inevitable due to somatic growth, the bileaflet mechanical prostheses used displayed appropriate durability.

Measurement of Residual Stresses within a PWR Swaged Heater Tube

2011 ◽  
Vol 70 ◽  
pp. 279-284 ◽  
Author(s):  
D.M. Goudar ◽  
Ed J. Kingston ◽  
Mike C. Smith ◽  
Sayeed Hossain
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Stress Measurement ◽  
Measurement Techniques ◽  
Residual Stress Distribution ◽  
Hole Drilling ◽  
Shear Stresses ◽  
Outer Diameter ◽  
Near Surface ◽  
Heater Tube

Frequent failures of the pressuriser heater tubes used in Pressurised Water Reactors (PWRs) have been found. Axial cracks initiating from the tube outer diameter have been detected in some tubes as well as the resulting electrical problems. Replacement of the heater tubes requires an undesirably prolonged plant shutdown. In order to better understand these failures a series of residual stress measurements were carried out to obtain the near surface and through-thickness residual stress profiles in a stainless steel pressuriser heater tube. Three different residual stress measurement techniques were employed namely, Deep-Hole Drilling (DHD), Incremental Centre Hole Drilling (ICHD) and Sachs’ Boring (SB) to measure the through thickness residual stress distribution in the heater tubes. Results showed that the hoop stresses measured using all three techniques were predominantly tensile at all locations, while the axial stresses were found to be tensile at the surface and both tensile and compressive as they reduce to small magnitudes within the tube. The magnitude of the in-plane shear stresses was small at all measurement depths at all locations. The various measurement methods were found to complement each other well. All the measurements revealed a characteristic profile for the through-thickness residual stress distribution.

scholarly journals Stereoscopic PIV of Steady Flow Through a Bileaflet Mechanical Heart Valve

2008 ◽  
Author(s):  
C. Hutchison ◽  
P. E. Sullivan ◽  
C. R. Ethier
Keyword(s):  
Steady Flow ◽  
Heart Valve ◽  
Heart Valves ◽  
Mechanical Heart Valve ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Shear Stresses ◽  
Stereoscopic Piv ◽  
Bileaflet Mechanical Heart Valve ◽  
Component Particle

Each year over 180,000 mechanical heart valves are implanted worldwide, with the bileaflet mechanical heart valve (BiMHV) accounting for approximately 85% of all valve replacements [1,2]. Although much improved from previous valve designs, aortic BiMHV design is far from ideal, and serious complications such as thromboembolism and hemolysis often result. Hemolysis and platelet activation are thought to be caused by turbulent Reynolds shear stresses in the flow [1]. Numerous previous studies have examined aortic BiMHV flow using LDA and two component Particle Image Velocimetry (PIV), and have shown the flow to be complex and three-dimensional [3,4]. Stereoscopic PIV (SPIV) can obtain all three velocity components on a flow plane, and hence has the potential to provide better understanding of three dimensional flow characteristics. The objective of the current study was to use SPIV to measure steady flow, including turbulence properties, downstream of a BiMHV in a modeled aorta. The resulting dataset will be useful for CFD model validation, and the intent is to make it publicly available.

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