Integrated strategy for in vitro characterization of a bileaflet mechanical aortic valve
© The Author(s) 2017
Received: 23 July 2016
Accepted: 17 January 2017
Published: 16 February 2017
Haemodynamic performance of heart valve prosthesis can be defined as its ability to fully open and completely close during the cardiac cycle, neither overloading heart work nor damaging blood particles when passing through the valve. In this perspective, global and local flow parameters, valve dynamics and blood damage safety of the prosthesis, as well as their mutual interactions, have all to be accounted for when assessing the device functionality. Even though all these issues have been and continue to be widely investigated, they are not usually studied through an integrated approach yet, i.e. by analyzing them simultaneously and highlighting their connections.
An in vitro test campaign of flow through a bileaflet mechanical heart valve (Sorin Slimline 25 mm) was performed in a suitably arranged pulsatile mock loop able to reproduce human systemic pressure and flow curves. The valve was placed in an elastic, transparent, and anatomically accurate model of healthy aorta, and tested under several pulsatile flow conditions. Global and local hydrodynamics measurements and leaflet dynamics were analysed focusing on correlations between flow characteristics and valve motion. The haemolysis index due to the valve was estimated according to a literature power law model and related to hydrodynamic conditions, and a correlation between the spatial distribution of experimental shear stress and pannus/thrombotic deposits on mechanical valves was suggested. As main and general result, this study validates the potential of the integrated strategy for performance assessment of any prosthetic valve thanks to its capability of highlighting the complex interaction between the different physical mechanisms that govern transvalvular haemodynamics.
We have defined an in vitro procedure for a comprehensive analysis of aortic valve prosthesis performance; the rationale for this study was the belief that a proper and overall characterization of the device should be based on the simultaneous measurement of all different quantities of interest for haemodynamic performance and the analysis of their mutual interactions.
KeywordsPulse duplicator Image velocimetry Valve leaflets dynamics Haemolysis index
Incidence of heart valve diseases is growing in western countries with population age and life expectancy increasing [1, 2]. Satisfactory transvalvular haemodynamic conditions and heart pump function are usually restored at the short- and mid-term after valve replacement. Nevertheless, current prostheses are still quite far from representing the ‘optimum prosthetic valve’. Mechanical heart valves (MHVs) express high durability but induce flow patterns different from those observed in healthy subjects [3, 4]. Also, MHVs studies highlighted a sharp tendency to thrombus formation, which requires life-long anticoagulant therapy , as well as to haemolysis . On the other hand, biological prostheses haemodynamics is usually nearly physiological but they show short durability mainly due to leaflets stiffening caused by shear stresses and calcification phenomena [6–8]. In both cases the fluid–structure interaction plays a fundamental role in determining prosthesis functionality, hence a thorough analysis of flow characteristics close to the valve is essential to assess its overall performance . The work by Dasi et al. , who described the interaction between vorticity and leaflet kinematics of a bileaflet mechanical heart valve (BMHV), is a first important step in that direction. However, literature usually focuses on either global functionality, to assess whether the artificial valve overloads heart work, or local functionality, to quantify the shear stress field and its potential effects in terms of blood cells damage and leaflets degeneration. Several in vitro and in vivo studies were aimed at the experimental estimation of global haemodynamic parameters as the transvalvular pressure drop, the effective orifice area (EOA) or the regurgitant and leakage volumes (see e.g. [11–16]). As for valve dynamics, attention has been most devoted to study the behavior in time of the valve area for both biological and mechanical prosthesis [17–20], while the leaflets motion of bileaflet mechanical heart valve (BMHV) has been somehow less investigated despite the importance of the issue [10, 21–23]. Several numerical studies focused on the occluders dynamics using fluid–structure interactions approach [22, 24–27]. Flow patterns and shear stress distribution in correspondence of the valve have been extensively investigated both numerically [6, 24, 28, 29] and in vitro [20, 30–34]. Moreover, several literature works deal with red blood cells (RBCs) or platelets damage, providing haemolysis laws to characterize the dangerousness of the flow through the prosthetic device [35–39] or of the valve itself .
Even though these studies provide a solid and recognized base as single interpretation of a complex phenomenon, a unique strategy to characterize the valve overall hydrodynamic performance is still vacant. To this aim, this study proposes an integrated approach able to provide simultaneous in vitro measurements of (1) pressure and flow waves across a prosthetic valve; (2) leaflets position in time; (3) flow field and shear stress distribution (near and far fields) downstream of the valve (notice that all these quantities are required by international standards), and to highlight mutual interactions between all investigated mechanisms. The tests were performed in a mock loop simulating the human systemic circulation in a model of healthy ascending aorta.
Two piezoelectric sensors (PCB Piezotronics® 1500 series, Fig. 1a -P1 and P2-) located respectively 3,5D upstream and 6,25D downstream the aortic valve, provided aortic (pa) and ventricular (pv) pressure. An electromagnetic flowmeter (501D Carolina Medical Electronics, Fig. 1a -F-) recorded the aortic flow rate during cardiac cycle. An example of recorded forward flow rate Q in non-dimensional time t/T, where T is the dimensional period of the cycle, is reported in Fig. 1c. Positive Q gives the systolic outflow rate while the grey area equals the ejected stroke volume (SV). The time law of the ventricle volume change was assigned to mimic a physiological behavior (the flow curve used in the commercial, FDA approved, ViVitro® mock loop system). To fulfill the geometric similarity a geometric aspect-ratio 1:1 was set on the investigated area. Farther, since water (whose viscosity is about one-third of that of the blood) was used as working fluid, to respect the dynamic similarity, for a given physiological SV, the period of the cardiac cycle adopted in the experiments was set equal to three times the physiologic one. In the considered settings of the flow control parameters the peak velocity varied in the range 0.15–0.25 m/s and non-dimensional parameters, Reynolds and Womersley numbers, resulted respectively 2500 < Re < 4500 and 14 < Wo < 17. The similarity with respect to the leaflet motion is also matched since scale effects are not expected .
Pressure and EOA measurements
Equivalent beat rate (bpm)
An Additional file 1 containing the pressure fields across the valve is included [see pressure_data.xls].
Haemodynamic input conditions SV and T adopted in PD sensitivity analysis tests. Fundamental global haemodynamic parameters calculated as averages over 100 non-consecutive cycles are also reported; Δpm: mean transvalvular pressure drop over the ejection period; Qrms: root mean square aortic flow rate over the ejection period; EOA. Recall that to ensure dynamic similarity between the in vitro model and the real environment, experimental flow rate was set to 1/3 of the physiological one.
Leaflets dynamics was investigated through a semi-automatic image analysis technique. Pictures of aortic longitudinal mid-plane perpendicular to leaflets pivots were acquired by a high speed camera (Mikrotron Eosens MC1362) with spatial resolution 1280 × 1024 pixels and at 500 fps placed at an angle of 30° with respect to the valvular ring plane. Angles αL and αR between the valve ring plane and leaflets were measured, assuming each occluder as a line going from the leaflet top to the hinge (Fig. 1c, left). Ten instants in the ejection period were chosen as relevant to sample the tilting angles (Fig. 1c, right).
Global flow characteristics and prosthetic valve haemodynamic performance
Local transvalvular flow
Potential damage to blood particles
In biomedical devices, such as MHVs, shear stress distribution is usually quite far from the physiological condition both for spatial distribution and amplitude, thus demanding the quantification of shear-induced blood trauma to assess the safety and efficacy of the device prior to its marketing [1, 53].
Global haemodynamic performance of a BMHV in aortic position was tested measuring simultaneously different metrics varying the hydrodynamic working conditions, allowing an all-around view of the valve behaviour. In particular, we considered transvalvular pressure drop and EOA, leaflets opening/closing angle, local velocity and shear stresses, potential damage of blood cells. Results allowed to appreciate the asynchronous behaviour of the two leaflets, possibly due to their different orientation with respect to the sinuses of Valsalva and to even minor differences in leaflets design. The local flow field analysis showed the presence of asymmetric fluid structures particularly evident in the shear stress distribution. The shear stress in the region close to the valve allowed a first estimate of the potential damage of red blood cells due to mechanical action; also variations in the HI were found as the bulk flow conditions were varied.
both the EOA and the HI were found to be affected by bulk flow conditions; in particular, they both increase with SV and as T decreases, thus suggesting that the global and the local performance of the prosthesis show opposite trend with changes in the haemodynamic regime. In other words, the optimization of the overall prosthetic valve performan*ce results from the best possible compromise in the control of heart work overload and blood cells damage due to the valve itself. Moreover, also the leaflets dynamics was found to improve (in both leaflets synchronicity and maximum opening angle) with a SV increasing. We can hence speculate that flow dependence of the EOA (i.e. of the global performance of the prosthesis) actually is a consequence of the response of valve dynamics to flow changes. On the contrary the local performance, or at least the haemolytic potential, seems to appear more sensitive to flow intensity variations per se than to geometrical orifice area, although improved as a consequence of larger flow.
A strong asymmetry in the shear stress distribution was observed. A relevant clinical implication can be seen in that result, which can possibly explain the asymmetric distribution of pannus/thrombotic deposits that is sometimes reported for explanted BMHV [38, 63]. Whether local flow dynamics asymmetry is related to the asynchronous behaviour of valve leaflets and/or vice versa, and the latter to valve implant orientation with respect to the sinuses of Valsalva, deserves further investigation. A promising approach might be seen in a combination of in vitro tests like those here presented and in silico tests able to predict blood particles trauma [10, 40].
Availability of data and materials
The dataset supporting this study—in which results and discussion sections are based—are included within the article as additional files: one spreadsheet for the pressure fields across the valve (pressure_data.xls) and 8 for the velocity fields (2 for each of the 4 experiments performed, corresponding to the horizontal and vertical components) within the investigated domain.
As far as the pressures are concerned, the reported tests are labelled following Table 1. Each test columns report: the experiment time, the ventricular pressure, the aortic pressure, and the displacement acquired by the LVDT sensor placed at the bellow. Each acquisition is composed by 1200 samples.
SV = 64 ml; T = 2.4 s T = 2.6 s (U_64_2_4.dat, V_64_2_4.dat; U_64_2_6.dat, V_64_2_6.dat)
SV = 80 ml; T = 2.4 s T = 2.6 s (U_80_2_4.dat, V_80_2_4.dat; U_80_2_6.dat, V_80_2_6.dat) have included. Each file represent the time history of the corresponding velocity component: the number of rows corresponds to the size of the velocity field (50 × 51) while the number of columns corresponds to the number of acquired frames (1118 for experiments @T = 2.6 s, 1132 for experiments @T = 2.4 s).
mechanical heart valve
bileaflet mechanical heart valve
effective orifice area
red blood cells
left ventricle outflow tract
FS and GQ conceived the study; all authors participated in its design and coordination and helped to draft the manuscript; SE, RT and SF performed the pressure and flow measurements and the data analysis. All authors read and approved the final manuscript.
The authors declare that they have no competing interests.
This work was partially supported by MIUR Grant No. PRIN-2012HMR7CF.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
- Dasi LP, Simon HA, Sucosky P, Yoganathan AP. Fluid mechanics of artificial heart valves. Clin Exp Pharmacol. 2009;36(2):225–37.View ArticleGoogle Scholar
- Roger VL, Go AS, Lloyd-Jones DM, Adams RJ, Berry JD, Brown TM, Carnethon MR, Dai S, De Simone G, Ford ES, Fox CS, Fullerton HJ, Gillespie C, Greenlund KJ, Hailpern SM, Heit JA, Ho PM, Howard VJ, Kissela BM, Kittner SJ, Lackland DT, Lichtman JH, Lisabeth LD, Makuc DM, Marcus GM, Marelli A, Matchar DB, McDermott MM, Meigs JB, Moy CS, Mozaffarian D, Mussolino ME, Nichol G, Paynter NP, Rosamond WD, Sorlie PD, Stafford RS, Turan TN, Turner MB, Wong ND, Wylie-Rosett J. Heart disease and stroke statistics—2011 update: a report from the American Heart Association. Circulation. 2011;123(4):18–209.View ArticleGoogle Scholar
- Faludi R, Szulik M, D’hooge J, Herijgers P, Rademakers F, Pedrizzetti G, Voigt JU. Left ventricular flow patterns in healthy subjects and patients with prosthetic mitral valves: an in vivo study using echocardiographic particle image velocimetry. J Thorac Cardiovasc Surg. 2010;139:1501–10.View ArticleGoogle Scholar
- von Knobelsdorff-Brenkenhoffa F, Trauzeddela R, Barkerb A, Gruettnera H, Marklb M, Schulz-Mengera J. Blood flow characteristics in the ascending aorta after aortic valve replacement—a pilot study using 4D-flow MRI. Int J Cardiol. 2010;170:426–33.View ArticleGoogle Scholar
- Ismeno G, Renzulli A, Carozza A, De Feo M, Iannuzzi M, Sante P, Cotrufo M. Intravascular haemolysis after mitral and aortic valve replacement with different types of mechanical prostheses. Int J Cardiol. 1999;69:179–83.View ArticleGoogle Scholar
- Ge L, Sotiropoulos F. Direction and magnitude of blood flow shear stresses on the leaflets of aortic valves: is there a link with valve calcification? J Biomech Eng. 2010;132(1):014505.View ArticleGoogle Scholar
- Sabbah HN, Hamid MS, Stein PD. Estimation of mechanical stresses on closed cups of porcine bioprosthetic valves: effects of stiffening, focal calcium and focal thinning. Am J Cardiol. 1985;65(8):1091–6.View ArticleGoogle Scholar
- Raghav VR, Okafor I, Quach M, Dang L, Marquez S, Yoganathan AP. Long-term durability of Carpentier-Edwards Magna Ease valve: a one billion cycle in vitro study. Ann Thorac Surg. 2016;101(5):1759–65.View ArticleGoogle Scholar
- Yoganathan AP, Chandran KB, Sotiropulos F. Flow in prosthetic heart valves: state-of-the-art and future directions. Ann Biomed Eng. 2005;33(12):1689–94.View ArticleGoogle Scholar
- Dasi LP, Ge L, Simon HA, Sotiropoulos F, Yoganathan AP. Vorticity dynamics of a bileaflet mechanical heart valve in an axisymmetric aorta. Phys Fluids. 2007;19(067105–1):17.MATHGoogle Scholar
- Gerosa G, Tarzia V, Rizzoli G, Bottio T. Small aortic annulus: the haemodynamic performances of 5 commercially available tissue valves. J Thorac Cardiovasc Surg. 2006;131(5):1058–64.View ArticleGoogle Scholar
- Grigioni M, Daniele C, D’Avenio G, Morbiducci U, Del Gaudio C, Abbate M, Di Meo D. Innovative technologies for the assessment of cardiovascular medical devices: state-of-the-art techniques for artificial heart valve testing. Expert Rev Med Devices. 2004;1(1):81–93.View ArticleGoogle Scholar
- Guivier C, Deplano V, Pibarot P. New insights into the assessment of the prosthetic valve performance in the presence of subaortic stenosis through a fluid–structure interaction model. J Biomech. 2007;40(10):2283–90.View ArticleGoogle Scholar
- Leo HL, Prasad D, Carberry J, Simon AH, Yoganathan AJ. Fluid dynamic assessment of three polymeric heart valves using particle image velocimetry. Ann Biomed Eng. 2006;34(6):936–52.View ArticleGoogle Scholar
- Lim WL, Chew YT, Chew TC, Low HT. Steady flow dynamics of prosthetic aortic heart valves: a comparative evaluation with PIV techniques. J Biomech. 1998;31(5):411–21.View ArticleGoogle Scholar
- Sodian R, Hoerstrup SP, Sperling JS, Daebritz S, Martin DP, Moran AM, Kim BS, Schoen FJ, Vacanti JP, Mayer JE Jr. Early in vivo experience with tissue-engineered trileaflet heart valves. Circulation. 2000;102(19 Suppl 3):III22–9.Google Scholar
- Blais C, Burwash IG, Mundigler G, Dumesnil JG, Loho N, Rader F, Baumgartner H, Beanlands RS, Chayer B, Kadem L, Garcia D, Durand LG, Pibarot P. Projected valve area at normal flow rate improves the assessment of stenosis severity in patients with low-flow, low-gradient aortic stenosis the multicenter TOPAS (Truly or Pseudo-Severe Aortic Stenosis) study. Circulation. 2006;113:711–21.View ArticleGoogle Scholar
- Clavel MA, Burwash IC, Mundigler G, Dumesnil JG, Baumgartner H, Bergler-Klein J, Sénéchal M, Mathieu P, Couture C, Beanlands R, Pibarot P. Validation of conventional and simplified methods to calculate projected valve area at normal flow rate in patients with low flow, low gradient aortic stenosis: the multicenter TOPAS (True or Pseudo Severe Aortic Stenosis) study. J Am Soc Echocardiogr. 2010;23(4):380–6.View ArticleGoogle Scholar
- Poh KK, Levine RA, Solis J, Shen L, Flaherty M, Kang YJ, Guerrero JL, Hung J. Assessing aortic valve area in aortic stenosis by continuity equation: a novel approach using real-time three-dimensional echocardiography. Eur Heart J. 2008;29:2526–35.View ArticleGoogle Scholar
- Scotten LN, Walker DK. New laboratory technique measures projected dynamic area of prosthetic heart valves. J Heart Valve Dis. 2004;13(1):120–33.Google Scholar
- Shipkowitz T, Ambrus J, Kurk J, Wickramasinghe K. Evaluation technique for bileaflet mechanical valves. J Heart Valve Dis. 2002;11(2):275–82.Google Scholar
- Arjunon S, Ardana PH, Saikrishnan N, Madhani S, Foster B, Glezer A, Yoganathan AP. Design of a pulsatile flow facility to evaluate thrombogenic potential of implantable cardiac devices. J Biomech Eng. 2015;137:045001–9.View ArticleGoogle Scholar
- Nobili M, Morbiducci U, Ponzini R, Del Gaudio R, Balducci A, Grigioni M, Montevecchi FM, Redaelli A. Numerical simulation of the dynamics of a bileaflet prosthetic heart valve using a fluid–structure interaction approach. J Biomech. 2008;41:2539–50.View ArticleGoogle Scholar
- Astorino M, Gerbeau JF, Pantz O, Traoré KF. Fluid–structure interaction and multi-body contact: application to aortic valves. Comput Methods Appl Mech Eng. 2009;198:3603–12.MathSciNetView ArticleMATHGoogle Scholar
- De Hart J, Peters GWM, Schreurs PJG, Baaijens FPT. A three-dimensional computational analysis of fluid–structure interaction in the aortic valve. J Biomech. 2013;36(1):103–12.View ArticleGoogle Scholar
- De Tullio MD, Nam J, Pascazio G, Balaras E, Verzicco R. Computational prediction of mechanical haemolysis in aortic valved prostheses. Eur J Mech B Fluids. 2012;35:47–53.MathSciNetView ArticleGoogle Scholar
- Van Loon R. Towards computational modelling of aortic stenosis. Int J Numer Methods Biomed Eng. 2010;26:405–20.MathSciNetView ArticleMATHGoogle Scholar
- Krafczyk M, Cerrolaza M, Schulz M, Rank E. Analysis of 3D transient blood flow passing through an artificial aortic valve by Lattice–Boltzmann methods. J Biomech. 1998;31(5):453–62.View ArticleGoogle Scholar
- Smadi O, Hassan I, Pibarot P, Kadem L. Numerical and experimental investigations of pulsatile blood flow pattern through a dysfunctional mechanical heart valve. J Biomech. 2010;43:1565–72.View ArticleGoogle Scholar
- Grigioni M, Daniele C, Romanelli C, Barbaro V. Report ISTISAN 03/21, 2003. ISSN: 1123–3117.
- Hasenkam JM, Westphal D, Wygaard H, Reul H, Giersiepen M, Stodkilde H. In vitro stress measurements in the vicinity of six mechanical aortic valves using hot-film anemometry in steady flow. J Biomech. 1988;21(3):235–47.View ArticleGoogle Scholar
- Simon HA, Dasi LP, Leo HL, Yoganathan AP. Spatio-temporal flow analysis in bileaflet heart valve hinge regions: potential analysis for blood element damage. Ann Biomed Eng. 2007;35(8):1333–46.View ArticleGoogle Scholar
- Yap CH, Saikrishnan N, Yoganathan AP. Experimental measurement of dynamic fluid shear stress on the ventricular surface of the aortic valve leaflet. Biomech Model Mechanobiol. 2012;11:231–44.View ArticleGoogle Scholar
- Yoganathan AP, Woo Y, Sung H. Turbulent shear stress measurements in the vicinity of aortic heart valve prostheses. J Biomech. 1986;19(6):433–42.View ArticleGoogle Scholar
- Alemu Y, Bluestein D. Flow-induced platelet activation and damage accumulation in a mechanical heart valve: numerical studies. Artif Organs. 2007;31:677–88.View ArticleGoogle Scholar
- Dumont K, Vierendeels J, Kaminsky R, Van Nooten G. Comparison of the haemodynamic and thrombogenic performance of two bileaflet mechanical heart valves using a CFD/FSI model. J Biomech Eng. 2007;129:558–65.View ArticleGoogle Scholar
- Fraser KH, Zhang T, Taskin ME, Griffith BP, Wu ZJ. A quantitative comparison of mechanical blood damage parameters in rotary ventricular assist devices: shear stress, exposure time and haemolysis index. J Biomech Eng. 2012;129(081002):1–11.Google Scholar
- Goubergrits L. Numerical modeling of blood damage: current status, challenges and future prospects. Expert Rev Med Devices. 2006;3(5):527–31.View ArticleGoogle Scholar
- Morbiducci U, Ponzini R, Nobili M, Massai D, Montevecchi FM, Bluestein D, Redaelli A. Blood damage safety of prosthetic heart valves. Shear-induced platelet activation and local flow dynamics: a fluid–structure interaction approach. J Biomech. 2009;42:1952–60.View ArticleGoogle Scholar
- Toninato R, Fadda G, Fortini S, Espa S, Querzoli G, Susin FM. Coupling PIV Measurements and numerical modelling of RBCs mechanics to predict thrombogenicity of mechanical prosthetic heart valves, WCB 2014, Boston 1–7 July 2014. ISBN: 978-1-63439-381-2.
- Cenedese A, Del Prete Z, Miozzi M, Querzoli G. A laboratory investigation of the flow in the left ventricle of a human heart with prosthetic, tilting disk valves. Exp Fluids. 2005;39(2):322–35.View ArticleGoogle Scholar
- Espa S, Badas MG, Fortini S, Querzoli G, Cenedese A. A Lagrangian investigation of the flow inside the left ventricle. Eur J Mech B Fluids. 2012;35(1):9–19.View ArticleGoogle Scholar
- Fortini S, Querzoli G, Espa S, Cenedese A. Three-dimensional structure of the flow inside the left ventricle of the human heart. Exp Fluids. 2013;54:1609–19.View ArticleGoogle Scholar
- Querzoli G, Fortini S, Cenedese A. Effect of the prosthetic mitral valve on vortex dynamics and turbulence on the left ventricular flow. Phys Fluids. 2010;22(4):041901–10.View ArticleMATHGoogle Scholar
- Vukicevic M, Fortini S, Querzoli G, Espa S, Pedrizzetti G. Experimental study of the asymmetric heart valve prototype. Eur J Mech B Fluids. 2012;35:54–60.View ArticleGoogle Scholar
- Querzoli G, Fortini S, Espa S, Costantini M, Sorgini F. Fluid dynamics of aortic root dilation in Marfan syndrome. J Biomech. 2014;47:3120–8.View ArticleGoogle Scholar
- Fortini S, Espa S, Querzoli G, Cenedese A. Turbulence investigation in a laboratory model of the ascending aorta. J Turbul. 2015;16(3):208–24.View ArticleGoogle Scholar
- Isnard RN, Pannier BM, Laurent S, London GM, Diebold B, Safar ME. Pulsatile diameter and elastic modulus of the aortic arch in essential hypertension: a noninvasive study. J Am Coll Cardiol. 1989;13(2):399–405.View ArticleGoogle Scholar
- Baumgartner D, Baumgartner C, Mátyás G, Steinmann B, Löffler-Ragg J, Schermer E, Schweigmann U, Baldissera I, Frischhut B, Hess J, Hammerer I. Diagnostic power of aortic elastic properties in young patients with Marfan syndrome. J Thorac Cardiovasc Surg. 2005;129:730–9.View ArticleGoogle Scholar
- Josa M, Castellá M, Paré C, Bedini JL, Cartañá R, Mestres CA, Pomar JL, Mulet J. Haemolysis in mechanical bileaflet prostheses: experience with the Bicarbon valve. Ann Thorac Surg. 2006;81(4):1291–6.View ArticleGoogle Scholar
- Misawa Y, Saito T, Konishi H, Oki S, Kaminishi Y, Sakano Y, Morita H, Aizawa K. Clinical experience with the Bicarbon heart valve prostheses. J Cardiothoracic Surg. 2007;25:2–8.Google Scholar
- ISO 5840-2:2015 Cardiovascular implants—Cardiac valve prostheses—Part 2: Surgically implanted heart valve substitutes. http://www.iso.org/iso/catalogue_detail.htm?csnumber=51314.
- Taskin ME, Fraser KH, Zhang T, Wu C, Griffith BP, Wu ZJ. Evaluation of Eulerian and Lagrangian models for haemolysis estimation. ASAIO J. 2012;58:363–72.View ArticleGoogle Scholar
- Grigioni M, Morbiducci U, D’Avenio G, Di Benedetto G, Del Gaudio C. A novel formulation for blood trauma prediction by a modified power-law mathematical model. Biomech Model Mechanobiol. 2005;4:249–60.View ArticleGoogle Scholar
- Giersiepen M, Wurzinger LJ, Opitz R, Reul H. Estimation of shear stress-related blood damage in heart valve prostheses—in vitro comparison of 25 aortic valves. Int J Artif Organs. 1990;13(5):300–6.Google Scholar
- Grigioni M, Daniele C, D’Avenio G, Barbaro V. Evaluation of the surface-averaged load exerted on a blood element by the Reynolds shear stress field provided by artificial cardiovascular devices. J Biomech. 2002;35:1613–22.View ArticleGoogle Scholar
- Guyton AC, Hall JE. Textbook of medical physiology. 11th ed. Philadelphia: Elsevier Saunders; 2006.Google Scholar
- Garcia D, Pibarot P, Durand P. Analytical modeling of the instantaneous pressure gradient across the aortic valve. J Biomech. 2005;38(6):1303–11.View ArticleGoogle Scholar
- Walker DK, Brendzel AW, Scotten LN. The new St. Jude Medical regent mechanical heart valve: laboratory measurements of haemodynamic performance. J Heart Valve Dis. 1999;8(6):687–96.Google Scholar
- Borazjani I, Sotiropoulos F. The effect of implantation orientation of a bileaflet mechanical heart valve on kinematics and haemodynamics in an anatomic aorta. J Biomech Eng. 2010;132(11):111005.View ArticleGoogle Scholar
- Toninato R, Salmon J, Susin FM, Ducci A, Burriesci G. Physiological vortices in the sinuses of Valsalva: an in vitro approach for bio-prosthetic valves. J Biomech. 2016;49:2635–43.View ArticleGoogle Scholar
- Akutsu T, Matsumoto A. Influence of three mechanical bileaflet prosthetic valve designs on the three-dimensional flow field inside a simulated aorta. J Artif Organs. 2010;13:207–17.View ArticleGoogle Scholar
- Chan J, Marwan M, Schepis T, Ropers D, Du L, Achenbach S. Cardiac CT Assessment of prosthetic aortic valve dysfunction secondary to acute thrombosis and response to thrombolysis. Circulation. 2009;120:1933–4.View ArticleGoogle Scholar