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Li K, Sun W. Simulated transcatheter aortic valve deformation: A parametric study on the impact of leaflet geometry on valve peak stress. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2017; 33:10.1002/cnm.2814. [PMID: 27327357 PMCID: PMC5177542 DOI: 10.1002/cnm.2814] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 05/18/2016] [Accepted: 05/19/2016] [Indexed: 05/10/2023]
Abstract
In this study, we developed a computational framework to investigate the impact of leaflet geometry of a transcatheter aortic valve (TAV) on the leaflet stress distribution, aiming at optimizing TAV leaflet design to reduce its peak stress. Utilizing a generic TAV model developed previously [Li and Sun, Annals of Biomedical Engineering, 2010. 38(8): 2690-2701], we first parameterized the 2D leaflet geometry by mathematical equations, then by perturbing the parameters of the equations, we could automatically generate a new leaflet design, remesh the 2D leaflet model and build a 3D leaflet model from the 2D design via a Python script. Approximately 500 different leaflet designs were investigated by simulating TAV closure under the nominal circular deployment and physiological loading conditions. From the simulation results, we identified a new leaflet design that could reduce the previously reported valve peak stress by about 5%. The parametric analysis also revealed that increasing the free edge width had the highest overall impact on decreasing the peak stress. A similar computational analysis was further performed for a TAV deployed in an abnormal, asymmetric elliptical configuration. We found that a minimal free edge height of 0.46 mm should be adopted to prevent central backflow leakage. This increase of the free edge height resulted in an increase of the leaflet peak stress. Furthermore, the parametric study revealed a complex response surface for the impact of the leaflet geometric parameters on the peak stress, underscoring the importance of performing a numerical optimization to obtain the optimal TAV leaflet design. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Kewei Li
- Tissue Mechanics Laboratory, Biomedical Engineering Department and Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269
| | - Wei Sun
- Tissue Mechanics Laboratory, Biomedical Engineering Department and Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, GA 30313
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Folliguet T, Dibie A, Laborde F. Future of cardiac surgery: minimally invasive techniques in sutureless valve resection. Future Cardiol 2009; 5:443-52. [DOI: 10.2217/fca.09.35] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Aortic valve replacement with mechanical or biological heart valves is the treatment of choice for aortic valve stenosis when it is symptomatic or with severe aortic stenosis (≤ 0.6 cm2/m2) or with left ventricular dysfunction. In an effort to improve the outcomes of patients with stented biological valves, stentless valves were introduced to clinical practices in the early 1990s. Theses valves were designed to be less obstructive, and thus result in a lower transvalvular gradient. Technically the implantations of these valves are more demanding resulting in longer cross clamp and bypass times. However, important comorbid conditions in elderly patients referred for aortic valve replacement require alternative treatment options with possible reductions of the extracorporeal bypass time and reliable hemodynamic features. In order to comply with these requirements, percutaneous valves and sutureless surgical valves have been developed. The percutaneous technique has the advantage of being performed without circulatory bypass but leaving the aortic calcifications in place, thereby resulting in a high degree of paravalvular insufficiency, atrioventricular block and strokes. The surgical approach has the advantage of removing all calcifications and the valves can be optimally implanted, resulting in minimal paravalvular leak with a low incidence of atrioventricular block and strokes; however, it requires cardiopulmonary bypass. In addition, it can be performed with a low mortality (<3% in isolated aortic replacement, even in older patients). This article reviews the various techniques, strength and limitations of these sutureless valves implanted in the aortic position.
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Affiliation(s)
- Thierry Folliguet
- Department of Cardiovascular Surgery, L’institut Mutualiste Montsouris, 42 Boulevard Jourdan, Paris 75014, France
| | - Alain Dibie
- L’institut Mutualiste Montsouris, 42 Boulevard Jourdan, Paris 75014, France
| | - François Laborde
- L’institut Mutualiste Montsouris, 42 Boulevard Jourdan, Paris 75014, France
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Borowiec JW, Dubiel TW, Hansson HE, Landelius J, Nyström SO. Pericarbon pericardial valve prosthesis: midterm results of the aortic valve replacement. Angiology 1998; 49:1-11. [PMID: 9456159 DOI: 10.1177/000331979804900101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
This clinical study was undertaken to verify the encouraging results of experimental studies regarding a new pericardial bioprosthesis. From May 1989 to November 1993, 204 patients underwent an aortic valve replacement with the Pericarbon (Sorin Biomedica Cardio S.p.A., Saluggia, Italy) prosthesis. A follow-up was 100% complete and extended to 65 months (total 408 patient-years, average 2.0+/-1.4 years). Mean age at the operation was 75.1+/-5.5 years and 96% were in NYHA clinical stage III or IV. There were 86 men and 118 women; 73 patients had an isolated aortic valve disease, 131 had a concomitant cardiosurgical procedure (coronary artery bypass grafting in 106 patients). The operative mortality (30-day mortality) rate was 11.8% (24/204). There were 24 late deaths (5.9+/-1.2% patient-year). The actuarial probability of survival was 68+/-5% at 5 years. Four patients died of valve-related causes (one thromboembolic complication, two endocarditis, one anticoagulant-related hemorrhage). Actuarial rate of freedom from valve-related death was 95+/-3% at 5 years. Valve-related morbidity included seven thromboembolic episodes (1.7% patient-year), four anticoagulant-related complications (0.9% patient-year), three endocarditis (0.7% patient-year) and one reoperation (0.2% patient-year). After 5 years freedom from thromboembolic events was 83+/-7%, from anticoagulant-related hemorrhage 96+/-2%, from endocarditis 97+/-2%, and from reoperation 99+/-1%. Echocardiographic study performed in 30 patients showed a paraprosthetic leak in four patients, a central leak in two, and cusp thickening in another three. The clinical data showed that the Pericarbon prosthesis has valve-related morbidity. The echocardiographic results suggest that the prosthesis can undergo a pathologic process during the first 5 years after implantation. This makes it necessary to continue the follow-up and include the larger number of patients in the echocardiographic investigation.
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Affiliation(s)
- J W Borowiec
- Department of Thoracic and Cardiovascular Surgery, University Hospital, Uppsala, Sweden
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Waszyrowski T, Kasprzak JD, Krzemińska-Pakuła M, Dziatkowiak A, Zasłonka J. Early and long-term outcome of aortic valve replacement with homograft versus mechanical prosthesis--8-year follow-up study. Clin Cardiol 1997; 20:843-8. [PMID: 9377820 PMCID: PMC6655983 DOI: 10.1002/clc.4960201010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/1997] [Accepted: 07/21/1997] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Aortic valve disease is an important and frequent clinical problem with a mortality rate as high as 50-80% in a 5-year natural history of patients with severe aortic valve disease. Biological or mechanical prosthesis implantation is the only way to improve prognosis. HYPOTHESIS The aim of our study was to assess the clinical outcome of aortic valve replacement according to the underlying valve pathology and the type of replacement device, that is, aortic homografts versus mechanical prostheses. METHODS The study group consisted of 143 patients with a mean follow-up period of 4.1 +/- 2.7 years. All patients had annual clinical and Doppler echocardiographic evaluation. RESULTS Total 8-year mortality was 4.9% (7/143) including early mortality of 1.4%. Eight-year survival probability was not significantly higher in the homograft than in the mechanical prosthesis recipients. No differences were found among subgroups with aortic stenosis, insufficiency, and combined disease. Overall early and late complication rate (13.3 and 24.8%, respectively) was similar in homograft and mechanical valve recipients. The most common late complications were ventricular arrhythmia (10%) (Lown class I-III), predominantly in the homograft recipients (17.7 vs. 3.7%), and heart failure (9.2%), more frequent in mechanical valve recipients (14.8 vs. 1.6%). Thromboembolic events occurred in 6.3%, infective endocarditis in 4.2% (more common in mechanical valve recipients), serious bleeding in 3.7% (only in mechanical valve recipients). There was no significant difference in early and late complication rate among subgroups (aortic stenosis, insufficiency, and combined disease). Of the patients studied, 91.6% improved in functional status after surgery, with significantly better outcome in homograft recipients. The type of preexisting valve disease did not influence clinical improvement. CONCLUSION Early and late mortality as well as estimated probability of survival and hemodynamic improvement at 8-year follow-up after aortic valve replacement are independent of the type of implanted valve. Complication rate does not depend upon the type of preexisting valve pathology, but severe late complications are more common after mechanical valve implantation than after homograft implantation.
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Affiliation(s)
- T Waszyrowski
- Department of Cardiology and Cardiac Surgery, Medical University of Lódz, Poland
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Talman EA, Boughner DR. Glutaraldehyde fixation alters the internal shear properties of porcine aortic heart valve tissue. Ann Thorac Surg 1995; 60:S369-73. [PMID: 7646190 DOI: 10.1016/0003-4975(95)00250-o] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Glutaraldehyde fixation noticeably alters the mechanical properties of porcine aortic valve tissue, subsequently affecting the function and durability of these tissues when used as prosthetic heart valves. Traditional uniaxial tensile testing techniques do not fully define the mechanical properties and we have devised a new approach to examine the important shear properties of the tissue. Altered shear properties would change the response of the valve tissue as it flexes open and closed. An apparatus combining a high-precision linear actuator with a gram-sensitive load cell was used to measure the shear characteristics of circular punch specimens taken from the center of each valve cusp. The tissue parameters measured showed significant differences between the fixed and fresh tissues. Glutaraldehyde-fixed tissue (n = 16) was about 100 times as stiff as fresh tissue (n = 32) between shear strain values of 0 and 0.2. The fixed tissue also had stress relaxation rates about 60% those of the fresh cusps and had about 70% of the hysteresis loss seen in fresh tissue. These results demonstrated the significant effects of glutaraldehyde fixation on the properties of porcine aortic valve cusp when tested in shear. Such changes could lead to altered tissue function and may increase internal stresses during opening and closing, contributing to valve fatigue.
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Affiliation(s)
- E A Talman
- John P. Robarts Research Institute, University of Western Ontario, London, Canada
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Dahm M, Husmann M, Prüfer D, Groh E, Oelert H. Relevance of immunologic reactions for tissue failure of bioprosthetic heart valves. Ann Thorac Surg 1995; 60:S348-52. [PMID: 7646186 DOI: 10.1016/0003-4975(95)00291-r] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The use of biologic heart valve prostheses is decreasing because of the high incidence of failure of these bioprostheses resulting from tissue degeneration or tearing. Immunologic reactions might play a decisive role in this process. The present experimental and clinical studies were conducted to investigate the relevance of immunologic reactions to the tissue failure of glutaraldehydetanned bovine pericardial and porcine valves. Specimens of the two different types of valve material were implanted in the abdominal muscles of rats. Enzyme-linked immunosorbent assays and tritiated thymidine incorporation tests were performed to detect specific antibodies and activated T cells. All specimens were studied histologically. Identical enzyme-linked immunosorbent assays and tritiated thymidine incorporation tests were performed in 29 patients with bioimplants and in 48 controls. Twenty explanted bioprostheses were investigated using histologic and immune histologic methods. The results of the enzyme-linked immunosorbent assays and lymphocyte proliferation tests showed that glutaraldehyde-tanned bovine pericardial valves can provoke cellular and humoral immunologic reactions in rats and human beings. In explanted bovine valves, macrophages were found invading and degrading implant collagen, starting from surface lesions. The combination of the formation of mechanical lesions, the development of cellular infiltrates, and collagen disruption strongly indicates that initial surface lesions initiate the immunologic reactions in bovine pericardial valves as the result of the exposure of incompletely tanned collagen. These immune responses might accelerate tissue degeneration. Porcine valves do not provoke immunologic reactions.
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Affiliation(s)
- M Dahm
- Department of Cardiovascular and Thoracic Surgery and Microbiology, University Hospital Mainz, Germany
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González-Juanatey JR, Garcia Acuña JM, Amaro A, Castelo V, Pedreira M, Garcia Bengoechea J, Gil M. Doppler echocardiographic comparison of small (19 mm) bileaflet and pericardial heart valve prostheses in aortic position. SCANDINAVIAN JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY 1995; 29:29-35. [PMID: 7644906 DOI: 10.3109/14017439509107198] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The resting haemodynamics of five types of small (19 mm) aortic valve prosthesis (2 bileaflet, 3 pericardial) were evaluated with Doppler echocardiography in 43 patients. Two received St Jude Medical and six CarboMedics bileaflet valves and 35 were given bioprostheses--16 Ionescu-Shiley, four Mitroflow and 15 Labcor-Santiago. No significant differences in peak or mean transvalvular pressure drop or in effective valve area were found between the bileaflet and the pericardial valves or among the three types of bioprosthesis. All but one of the bileaflet prostheses showed a characteristic regurgitation pattern, with two lateral and one central jet, and 16 (46%) of the bioprostheses showed central regurgitation, but in no case were these jets haemodynamically significant. Thus the 19 mm bileaflet and the studied pericardial prostheses all have satisfactory resting haemodynamics, and all are suitable for implanting in small aortic roots.
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Affiliation(s)
- J R González-Juanatey
- Department of Cardiology, Hospital General de Galicia, School of Medicine, Santiago de Compostela, Spain
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Moggio RA, Pooley RW, Sarabu MR, Christiana J, Ho AW, Reed GE. Experience with the Mitroflow aortic bioprosthesis. J Thorac Cardiovasc Surg 1994. [DOI: 10.1016/s0022-5223(94)70003-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Loisance DY, Mazzucotelli JP, Bertrand PC, Deleuze PH, Cachera JP. Mitroflow pericardial valve: long-term durability. Ann Thorac Surg 1993; 56:131-6. [PMID: 8328843 DOI: 10.1016/0003-4975(93)90416-f] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Isolated aortic (n = 107), mitral (n = 63), and tricuspid (n = 1) valve replacement and 28 double-valve replacements were performed with a second generation of pericardial valves, the Mitroflow valve, in 199 patients from March 1983 to December 1986. Follow-up (total, 1,058 patient-years) was extended to 106 months and 91.5% complete. Mean age was 58 +/- 13 years. The operative mortality included 22 deaths, non-cardiac-related in 7. The actuarial probability of survival for all patients was 66% +/- 4% at 8.5 years. There were no significant differences between patients with aortic valve replacement, mitral valve replacement, or double-valve replacement. The rate of thromboembolic events, antithromboembolic therapy-related hemorrhage, periprosthetic leak, and endocarditis is extremely minimal. Structural valve dysfunction occurred at a rate of 3.2% +/- 0.5%/patient-year. Actuarial freedom from the event was 94.6% +/- 1.7% at 5 years and 63.7% +/- 6.5% at 8.5 years for all valves. There were no difference in structural valve dysfunction rate between patients having aortic, mitral, or double-valve replacement. Thirty-five patients were reoperated on (3.4 +/- 0.6%/patient-year for all). The rate of all valve-related morbidity and mortality was 5.6% +/- 0.7%/patient-year for all patients, actuarial freedom from the event being 44% +/- 7% at 8.5 years. These data suggest that the excellent hemodynamic characteristics of the valve are balanced by a risk of valve failure that is slightly increased when compared with porcine valves.
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Affiliation(s)
- D Y Loisance
- Department of Surgical Research, URA CNRS 1431, Hôpital Henri Mondor, Faculté de Médecine, Créteil, France
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10
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Butany J, Vanlerberghe K, Silver MD. Morphologic findings and causes of failure in 24 explanted Ionescu-Shiley low-profile pericardial heart valves. Hum Pathol 1992; 23:1224-33. [PMID: 1427752 DOI: 10.1016/0046-8177(92)90289-f] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
From 1981 to 1987 just over 608 Ionescu-Shiley low-profile bovine pericardial bioprostheses were implanted at the Toronto Hospital. Twenty-four prostheses (11 aortic and 13 mitral) were surgically explanted from 1988 to 1990 from 20 adults (10 men and 10 women). Prosthesis failure was caused by primary tissue failure in 17 valves or by other mechanisms in seven valves. Variable degrees of tissue failure were also seen in four of the seven valves from the latter group. Primary tissue failure was characterized by fluid insudation between collagen bundles, para stent post tears (alignment stitch related, 20 valves), cusp perforation with prolapse, and calcification. The earliest cusp tears occurred at 28 months. Calcification (10 of 24 cases) was minimal in seven of 10 valves (occurring primarily at the margins of the torn cusp), moderate in two, and severe in one. Tissue overgrowth (pannus) was seen in all but three prostheses. Like its predecessor, the Ionescu-Shiley standard pericardial valve, this prosthesis failed at 2 to 5 years largely due to design-related (alignment stitch) causes and tissue degeneration. Calcification was less prominent, while tissue overgrowth (pannus) was more marked.
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Affiliation(s)
- J Butany
- Department of Pathology, Toronto Hospital, Ontario, Canada
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Walley VM, Keon CA, Khalili M, Moher D, Campagna M, Keon WJ. Ionescu-Shiley valve failure. I: Experience with 125 standard-profile explants. Ann Thorac Surg 1992; 54:111-6. [PMID: 1610221 DOI: 10.1016/0003-4975(92)91153-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A group of standard-profile Ionescu-Shiley valve implants, 357 aortic and 190 mitral, was reviewed for cases of failure requiring surgical explantation. To date, 90 (25.2%) of the aortic and 35 (18.4%) of the mitral valves have failed, and are the subject of this analysis. Observations of these explants confirm previous suggestions about the clinical and pathologic patterns of the Ionescu-Shiley valve's failure, but are extended in this study to allow more confident statistical analyses. Cusp tear with insufficiency remains the most important reason for explantation, precipitating removal to date of 19.1% of the aortic and 10.0% of the mitral valves implanted. This difference, aortic versus mitral, is significant (p less than 0.006) and the reverse of observations made in other studies of pericardial valves. In this review there is no significant difference in the proportion of aortic and mitral valves that failed with calcification (2.2% and 3.1%, respectively). Aortic Ionescu-Shiley valves failing with tears had a mean of 3.1 tears per valve, whereas mitral valves had 1.2. Aortic valves also showed considerably more pretear wear than did mitral valves. Although the large number of these Ionescu-Shiley valve failures has been a profound clinical disappointment, it has provided an opportunity to observe and detail the pathology of their failure.
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Affiliation(s)
- V M Walley
- Department of Pathology, University of Ottawa, Canada
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