A Detailed Fluid Mechanics Study of Tilting Disk Mechanical Heart Valve Closure and the Implications to Blood Damage

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Keefe B. Manning ◽  
Luke H. Herbertson ◽  
Arnold A. Fontaine ◽  
Steven Deutsch
Keyword(s):  
Heart Valve ◽  
Heart Valves ◽  
Mechanical Heart Valve ◽  
In Vitro Study ◽  
Mechanical Heart Valves ◽  
Single Shot ◽  
Flow Measurements ◽  
Blood Damage ◽  
Disk Valve

Hemolysis and thrombosis are among the most detrimental effects associated with mechanical heart valves. The strength and structure of the flows generated by the closure of mechanical heart valves can be correlated with the extent of blood damage. In this in vitro study, a tilting disk mechanical heart valve has been modified to measure the flow created within the valve housing during the closing phase. This is the first study to focus on the region just upstream of the mitral valve occluder during this part of the cardiac cycle, where cavitation is known to occur and blood damage is most severe. Closure of the tilting disk valve was studied in a “single shot” chamber driven by a pneumatic pump. Laser Doppler velocimetry was used to measure all three velocity components over a 30ms period encompassing the initial valve impact and rebound. An acrylic window placed in the housing enabled us to make flow measurements as close as 200μm away from the closed occluder. Velocity profiles reveal the development of an atrial vortex on the major orifice side of the valve shed off the tip of the leaflet. The vortex strength makes this region susceptible to cavitation. Mean and maximum axial velocities as high as 7m∕s and 20m∕s were recorded, respectively. At closure, peak wall shear rates of 80,000s−1 were calculated close to the valve tip. The region of the flow examined here has been identified as a likely location of hemolysis and thrombosis in tilting disk valves. The results of this first comprehensive study measuring the flow within the housing of a tilting disk valve may be helpful in minimizing the extent of blood damage through the combined efforts of experimental and computational fluid dynamics to improve mechanical heart valve designs.

scholarly journals Near Valve Flows and Potential Blood Damage During Closure of a Bileaflet Mechanical Heart Valve

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
L. H. Herbertson ◽  
S. Deutsch ◽  
K. B. Manning
Keyword(s):  
Heart Valve ◽  
Heart Valves ◽  
Mechanical Heart Valve ◽  
In Vitro Study ◽  
Blood Damage ◽  
Bileaflet Mechanical Heart Valve ◽  
Fluid Velocities ◽  
Design Characteristics ◽  
Valve Housing

Blood damage and thrombosis are major complications that are commonly seen in patients with implanted mechanical heart valves. For this in vitro study, we isolated the closing phase of a bileaflet mechanical heart valve to study near valve fluid velocities and stresses. By manipulating the valve housing, we gained optical access to a previously inaccessible region of the flow. Laser Doppler velocimetry and particle image velocimetry were used to characterize the flow regime and help to identify the key design characteristics responsible for high shear and rotational flow. Impact of the closing mechanical leaflet with its rigid housing produced the highest fluid stresses observed during the cardiac cycle. Mean velocities as high as 2.4 m/s were observed at the initial valve impact. The velocities measured at the leaflet tip resulted in sustained shear rates in the range of 1500–3500 s−1, with peak values on the order of 11,000–23,000 s−1. Using velocity maps, we identified regurgitation zones near the valve tip and through the central orifice of the valve. Entrained flow from the transvalvular jets and flow shed off the leaflet tip during closure combined to generate a dominant vortex posterior to both leaflets after each valve closing cycle. The strength of the peripheral vortex peaked within 2 ms of the initial impact of the leaflet with the housing and rapidly dissipated thereafter, whereas the vortex near the central orifice continued to grow during the rebound phase of the valve. Rebound of the leaflets played a secondary role in sustaining closure-induced vortices.

Alternative mechanical heart valves for the developing world

2019 ◽  
Vol 28 (7) ◽  
pp. 431-443
Author(s):  
Elsmari Wium ◽  
Christiaan Johannes Jordaan ◽  
Lezelle Botes ◽  
Francis Edwin Smit
Keyword(s):  
Heart Valve ◽  
Computer Aided Design ◽  
Heart Valves ◽  
Developing World ◽  
Mechanical Heart Valve ◽  
Mechanical Heart Valves ◽  
Design Approach ◽  
Element Analysis ◽  
Mechanical Valves

Due to the prevalence of rheumatic heart disease in the developing world, mechanical heart valves in the younger patient population remain the prostheses of choice if repair is not feasible. Despite their durability, mechanical valves are burdened by coagulation and thromboembolism. Modern design tools can be utilized during the design process of mechanical valves, which allow a more systematic design approach and more detailed analysis of the blood flow through and around valves. These tools include computer-aided design, manufacturing, and engineering, such as computational fluid dynamics and finite element analysis, modern manufacturing techniques such as additive manufacturing, and sophisticated in-vitro and in-vivo tests. Following this systematic approach, a poppet valve was redesigned and the results demonstrate the benefits of the method. More organized flow patterns and fewer complex fluid structures were observed. The alternative trileaflet valve design has also been identified as a potential solution and, if a similar design approach is adopted, it could lead to the development of an improved mechanical heart valve in the future. It is imperative that researchers in developing countries continue their search for a mechanical heart valve with a reduced thromboembolic risk, requiring less or no anticoagulation.

Argatroban and bivalirudin compared to unfractionated heparin in preventing thrombus formation on mechanical heart valves

2009 ◽  
Vol 101 (06) ◽  
pp. 1163-1169 ◽  
Author(s):  
Torsten Linde ◽  
Thomas Michel ◽  
Kathrin Hamilton ◽  
Ulrich Steinseifer ◽  
Ivar Friedrich ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Unfractionated Heparin ◽  
Continuous Infusion ◽  
Valve Replacement ◽  
Heart Valves ◽  
Thrombus Formation ◽  
Mechanical Heart Valve ◽  
Mechanical Heart Valves ◽  
Valve Prostheses

SummaryPrevention of valve thrombosis in patients after prosthetic mechanical heart valve replacement and heparin-induced thrombocytopenia (HIT) is still an open issue. The aim of the present in-vitro study was to investigate the efficacy of argatroban and bivalirudin in comparison to unfractionated heparin (UFH) in preventing thrombus formation on mechanical heart valves. Blood (230 ml) from healthy young male volunteers was anticoagulated either by UFH, argatroban bolus, argatroban bolus plus continuous infusion, bivalirudin bolus, or bivalirudin bolus plus continuous infusion. Valve prostheses were placed in a newly developed in-vitro thrombosis tester and exposed to the anticoagulated blood samples. To quantify the thrombi, electron microscopy was performed, and each valve was weighed before and after the experiment. Mean thrombus weight in group 1 (UFH) was 117 + 93 mg, in group 2 (argatroban bolus) 722 + 428 mg, in group 3 (bivalirudin bolus) 758 + 323 mg, in group 4 (argatroban bolus plus continuous infusion) 162 + 98 mg, and in group 5 (bivalirudin bolus plus continuous infusion) 166 + 141 mg (p-value <0.001). Electron microscopy showed increased rates of thrombus formation in groups 2 and 3. Argatroban and bivalirudin were as effective as UFH in preventing thrombus formation on valve prostheses in our in-vitro investigation when they were administered continuously. We hypothesise that continuous infusion of argatroban or bivalirudin are optimal treatment options for patients with HIT after mechanical heart valve replacement for adapting oral to parenteral anticoagulation or vice versa.

Modifying a Tilting Disk Mechanical Heart Valve Design to Improve Closing Dynamics

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Luke H. Herbertson ◽  
Steven Deutsch ◽  
Keefe B. Manning
Keyword(s):  
Heart Valves ◽  
Liquid Core ◽  
Mechanical Heart Valve ◽  
Blood Damage ◽  
Mechanical Valves ◽  
Mitral Position ◽  
Disk Valve ◽  
Cavitation Intensity ◽  
The Moment ◽  
The One

The closing behavior of mechanical heart valves is dependent on the design of the valve and its housing, the valve composition, and the environment in which the valve is placed. One innovative approach for improving the closure dynamics of tilting disk valves is introduced here. We transformed a normal Delrin occluder into one containing a ”dynamic liquid core” to resist acceleration and reduce the moment of inertia, closing velocity, and impact forces of the valve during closure. The modified occluder was studied in the mitral position of a simulation chamber under the physiologic and elevated closing conditions of 2500 mm Hg/s and 4500 mm Hg/s, respectively. Cavitation energy, detected as high-frequency pressure transients with a hydrophone, was the measure used to compare the modified valve with its unaltered counterpart. The cavitation potential of tilting disk valves is indicative of the extent of blood damage occurring during valve closure. Initial findings suggest that changes to the structure or physical properties of well established mechanical valves, such as the one described here, can reduce closure induced hemolysis by minimizing cavitation. Compared with a normal valve, the cavitation intensity associated with our modified valve was reduced by more than 66% at the higher load. Furthermore, the modified valve took longer to completely close than did the standard tilting disk valve, indicating a dampened impact and rebound of the occluder with its housing.

scholarly journals Statistical Characteristics of Flow Field through Open and Semi-Closed Bileaflet Mechanical Heart Valve

2020 ◽  
Vol 2 (4) ◽  
pp. 184-196
Author(s):  
Oleksandr Voskoboinyk ◽  
Lidiia Tereshchenko ◽  
Vladimir Voskoboinick ◽  
Gabriela Fernandez ◽  
Andrey Voskoboinick ◽  
...  
Keyword(s):  
Heart Valve ◽  
Heart Valves ◽  
Mechanical Heart Valve ◽  
Pressure Sensors ◽  
Jet Flow ◽  
Operating Conditions ◽  
Mechanical Heart Valves ◽  
Statistical Characteristics ◽  
Diagnostic Tools ◽  
Bileaflet Mechanical Heart Valve

The formation of thrombi on the streamlined surface of the bileaflet mechanical heart valves is one of the main disadvantages of such valves. Thrombi block the valve leaflets and disrupt the cardiovascular system. Diagnosis of thrombosis of the bileaflet mechanical heart valves is relevant and requires the creation of effective diagnostic tools. Hydroacoustic registration of the heart noise is one of the methods for diagnosing the operation of a mechanical heart valve. The purpose of the research is to determine the statistical characteristics of the vortex and jet flow through the open and semi-closed bileaflet mechanical heart valve, to identify hydroacoustic differences and diagnostic signs to determine the operating conditions of the valve. Experimental studies were conducted in laboratory conditions on a model of the left atrium and left ventricle of the heart between which there was the bileaflet mechanical heart valve. Hydrodynamic noise was recorded by miniature pressure sensors, which were located downstream of the valve. The vortex and jet flow behind the prosthetic heart valve were non-linear, random processes and were analyzed using the methods of mathematical statistics and probability theory. The integral and spectral characteristics of the pressure field were obtained and the differences in the noise levels and their spectral components near the central and side jets for the open and semi-closed mitral valve were established. It was shown that hydroacoustic measurements could be an effective basis for developing diagnostic equipment for monitoring the bileaflet mechanical heart valve operation. Doi: 10.28991/SciMedJ-2020-0204-1 Full Text: PDF

Effect of Blood Pressure on Closing Dynamics of Bileaflet Mechanical Heart Valves

2012 ◽  
Author(s):  
Marcio H. Forleo ◽  
Brennan M. Johnson ◽  
Lakshmi P. Dasi
Keyword(s):  
Blood Pressure ◽  
Heart Valve ◽  
Heart Valves ◽  
Mechanical Heart Valve ◽  
Mechanical Heart Valves ◽  
Thromboembolic Complications ◽  
Stress Gradients ◽  
Bileaflet Mechanical Heart Valve ◽  
Sharp Stress ◽  
Rigid Design

Implantation of a bileaflet mechanical heart valve (BMHV) continues to be associated with a risk of thromboembolic complications despite anti-coagulation therapy1. This has been attributed to the structurally rigid design of the leaflets and valve mechanics combined with an intricate hinge mechanism for the rigid leaflets. The lack of a built in compliance within the valve mechanics presumably leads to sharp stress gradients within the flow as well as a violent closure of the valve often associated with the audible impact of the leaflets to the housing, and a potential for momentary cavitation of blood in the wake of leaflet impact.

Factor Xa Inhibitors for Patients after Mechanical Heart Valve Replacement?

2021 ◽  
Author(s):  
Stephen Gerfer ◽  
Maria Grandoch ◽  
Thorsten C.W. Wahlers ◽  
Elmar W. Kuhn
Keyword(s):  
Heart Valve ◽  
Heart Valves ◽  
Oral Anticoagulants ◽  
Mechanical Heart Valve ◽  
Factor Xa ◽  
Mechanical Heart Valves ◽  
Factor Xa Inhibitors ◽  
Current Evidence ◽  
Small Scale ◽  
Number Of Patients

AbstractPatients with a mechanical heart valve need a lifelong anticoagulation due to the increased risk of valve thrombosis and thrombo-embolism. Currently, vitamin K antagonists (VKA) are the only approved class of oral anticoagulants, but relevant interactions and side effects lead to a large number of patients not achieving the optimal therapeutic target international normalized ration (INR). Therefore, steady measurements of the INR are imperative to ensure potent anticoagulation within a distinctive range. Direct oral anticoagulants (DOACs) with newer agents could serve as a possible alternative to VKAs in this patient cohort. DOACs are approved for several indications, e.g., atrial fibrillation (AF). They only have a minor interaction potential, which is why monitoring is not needed. Thereby, DOACs improve the livability of patients in need of chronical anticoagulation compared with VKAs. In contrast to dual platelet inhibition using aspirin in combination with an ADP receptor antagonist and the direct thrombin inhibitor dabigatran, the oral factor Xa inhibitors apixaban and rivaroxaban show promising results according to current evidence. In small-scale studies, factor Xa inhibitors were able to prevent thrombosis and thrombo-embolic events in patients with mechanical heart valves. Finally, DOACs seem to represent a feasible treatment option in patients with mechanical heart valves, but further studies are needed to evaluate clinical safety. In addition to the ongoing PROACT Xa trial with apixaban in patients after aortic On-X valve implantation, studies in an all-comer collective with rivaroxaban could be promising.

scholarly journals Mechanical heart valves and pregnancy: Issues surrounding anticoagulation. Experience from two obstetric cardiac centres

2020 ◽  
pp. 1753495X2092493
Author(s):  
Francois Dos Santos ◽  
Lucia Baris ◽  
Alice Varley ◽  
Jerome Cornette ◽  
Joanna Allam ◽  
...  
Keyword(s):  
Heart Valve ◽  
Heart Valves ◽  
Mode Of Delivery ◽  
Mechanical Heart Valve ◽  
Significant Risk ◽  
Mechanical Heart Valves ◽  
Cardiac Complications ◽  
Anticoagulation Management ◽  
Valve Thrombosis ◽  
Heart Valve Thrombosis

Background Pregnant women with mechanical heart valves are at significant risk of obstetric/cardiac complications. This study compares the anticoagulation management in two obstetric cardiac centres. Methods Retrospective case-note review from Chelsea and Westminster/Royal Brompton Hospitals (CR) and Erasmus Medical Centre (EMC). Main outcome measure was mechanical heart valve thrombosis. Results Nineteen pregnancies from CR and 25 pregnancies from EMC were included. Most women were on low-molecular-weight heparin (LMWH) throughout pregnancy at CR, whereas at EMC most had LMWH in the first trimester and vitamin K antagonists in subsequent trimesters. Peak anti-factor Xa were performed monthly at CR, levels 0.39–1.51 IU/mL (mean 0.82 IU/mL). Anticoagulation management peri-partum was inconsistent. Delivery was mainly by Caesarean section at CR (74%) and vaginal delivery at EMC (64%). No maternal deaths and only one mechanical heart valve thrombosis at CR. Two mechanical heart valve thromboses and one maternal death at EMC. Conclusion Peri-partum anticoagulation strategies, anticoagulation monitoring and mode of delivery inconsistencies reported.

scholarly journals Potentially inappropriate prescribing of DOACs to patients with mechanical heart valves: a federated analysis of 57.9 million patients' primary care records in situ using OpenSAFELY

2021 ◽  
Author(s):  
◽  
Louis Fisher ◽  
Victoria Speed ◽  
Helen J Curtis ◽  
Christopher T Rentsch ◽  
...  
Keyword(s):  
Heart Valve ◽  
Heart Valves ◽  
Oral Anticoagulants ◽  
Direct Oral Anticoagulants ◽  
Inappropriate Prescribing ◽  
Mechanical Heart Valve ◽  
Mechanical Heart Valves ◽  
Audit And Feedback ◽  
National Guidance

National guidance was issued during the COVID-19 pandemic to switch patients on warfarin to direct oral anticoagulants (DOACs) where appropriate as these require less frequent blood testing. DOACs are not recommended for patients with mechanical heart valves. We conducted a retrospective cohort study of DOAC prescribing in people with a record of a mechanical heart valve between September 2019 and May 2021, and describe the characteristics of this population. We identified 15,457 individuals with a mechanical heart valve recorded in their records, of whom 1058 (6.8%) had been prescribed a DOAC during the study period. 767 individuals with a record of a mechanical heart valve were currently prescribed a DOAC as of May 31st 2020. This is suggestive of inappropriate prescribing of DOACs in individuals with mechanical heart valves. Direct alerts have been issued to clinicians through their EHR software informing the issue. We show that the OpenSAFELY platform can be used for rapid audit and feedback to mitigate the indirect health impacts of COVID-19 on the NHS. We will monitor changes in prescribing for this risk group over the following months.

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