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Barka N, Bourgoin J, Grassl E, St Cyr JA. Echocardiographic assessment of aortic valve annular and left ventricular outflow tract diameter in conscious and anesthetized adult sheep prior to prosthetic aortic valve implantation. Ther Adv Cardiovasc Dis 2016; 10:185-91. [PMID: 26702146 PMCID: PMC5942622 DOI: 10.1177/1753944715622919] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
OBJECTIVE Prosthetic heart valve implantation is commonly performed in patients that have valvular heart disease. Prior to clinical evaluation of newly developed prostheses, preclinical animal studies are performed for the assessment of both acute and chronic valvular function. Commonly, one size of valve is used in these preclinical studies, which can present difficulties with the implantation procedure and assessing valve function. Due to these potential problems, we developed a preoperative screening assessment in potential ovine candidates for prosthetic aortic valve implantation. By determining if there is a correlation between conscious and anesthetized echocardiographic examinations, an improvement in surgical confidence can predict that the animal is deemed a suitable candidate for a particular size of prosthetic valve for implantation prior to subjecting the animal to anesthesia and surgery. METHODS A total of 53 crossbred sheep (Ovis aries), male and female, 10-37 months of age, weighing between 41 and 77 kg, underwent conscious echocardiography and a subset of 29 of these animals underwent echocardiographic assessment under anesthesia for a preoperative valve size comparison in these animals prior to surgical prosthetic aortic valve implantation. Using 2D echocardiographic assessment, left ventricular outflow tract (LVOT) dimensions were assessed. RESULTS The mean paired difference between anesthetized and conscious LVOT diameter measurement was -0.87 mm (p = 0.0066, standard deviation 1.598, 95% confidence interval, -0.4796, -0.26378, n = 29). CONCLUSION This pilot study evaluation revealed that conscious echocardiographic assessment can play a role preoperatively in selecting potential candidates for surgical prosthetic aortic valve implantation, thereby minimizing the potential in prosthetic-native annular mismatching, which can contribute to altered LVOT function.
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Affiliation(s)
- Noah Barka
- Physiological Research Laboratories, Medtronic PLC, 710 Medtronic Parkway Northeast, Minneapolis, MN 55432, USA
| | - Jason Bourgoin
- Physiological Research Laboratories, Medtronic PLC., Minneapolis, MN, USA
| | - Erin Grassl
- Physiological Research Laboratories, Medtronic PLC., Minneapolis, MN, USA
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Luo J, Korossis SA, Wilshaw SP, Jennings LM, Fisher J, Ingham E. Development and characterization of acellular porcine pulmonary valve scaffolds for tissue engineering. Tissue Eng Part A 2014; 20:2963-74. [PMID: 24786313 DOI: 10.1089/ten.tea.2013.0573] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Currently available replacement heart valves all have limitations. This study aimed to produce and characterize an acellular, biocompatible porcine pulmonary root conduit for reconstruction of the right ventricular outflow tract e.g., during Ross procedure. A process for the decellularization of porcine pulmonary roots was developed incorporating trypsin treatment of the adventitial surface of the scraped pulmonary artery and sequential treatment with hypotonic Tris buffer (HTB; 10 mM Tris pH 8.0, 0.1% (w/v) EDTA, and 10 KIU aprotinin), 0.1% (w/v) sodium dodecyl sulfate in HTB, two cycles of DNase and RNase, and sterilization with 0.1% (v/v) peracetic acid. Histology confirmed an absence of cells and retention of the gross histoarchitecture. Immunohistochemistry further confirmed cell removal and partial retention of the extracellular matrix, but a loss of collagen type IV. DNA levels were reduced by more than 96% throughout all regions of the acellular tissue and no functional genes were detected using polymerase chain reaction. Total collagen levels were retained but there was a significant loss of glycosaminoglycans following decellularization. The biomechanical, hydrodynamic, and leaflet kinematics properties were minimally affected by the process. Both immunohistochemical labeling and antibody absorption assay confirmed a lack of α-gal epitopes in the acellular porcine pulmonary roots and in vitro biocompatibility studies indicated that acellular leaflets and pulmonary arteries were not cytotoxic. Overall the acellular porcine pulmonary roots have excellent potential for development of a tissue substitute for right ventricular outflow tract reconstruction e.g., during the Ross procedure.
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Affiliation(s)
- Ji Luo
- 1 Institute of Medical and Biological Engineering, The University of Leeds , Leeds, United Kingdom
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Substitute Heart Valves. Biomater Sci 2013. [DOI: 10.1016/b978-0-08-087780-8.00067-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Burrows MC, Zamarion VM, Filippin-Monteiro FB, Schuck DC, Toma HE, Campa A, Garcia CRS, Catalani LH. Hybrid Scaffolds Built From PET and Collagen as a Model For Vascular Graft Architecture. Macromol Biosci 2012; 12:1660-70. [DOI: 10.1002/mabi.201200154] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Revised: 07/23/2012] [Indexed: 11/11/2022]
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Mirensky TL, Breuer CK. The development of tissue-engineered grafts for reconstructive cardiothoracic surgical applications. Pediatr Res 2008; 63:559-68. [PMID: 18427302 DOI: 10.1203/01.pdr.0000305938.92695.b9] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Surgical correction of congenital heart defects often requires the use of valves, patches, or conduits to establish anatomic continuity. Homografts, xenografts, or mechanical prosthetic devices are frequently implanted during these surgical procedures. These grafts however lack growth potential, are associated with increased risk of thrombosis and infection and have limited durability, thus increasing the morbidity and mortality of their application in pediatric cardiac surgery. These limitations are being addressed through the development of living, biologic tissue-engineered valves, patches, and conduits. Pilot studies and phase 1 clinical trials are currently underway to evaluate their feasibility, safety, and efficacy. The optimal scaffold, cell source, and conditioning parameters, however, still remain to be determined and are areas of active research.
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Affiliation(s)
- Tamar L Mirensky
- Department of Surgery, Yale-New Haven Hospital, New Haven, CA 06520, USA.
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Khait L, Hecker L, Blan NR, Coyan G, Migneco F, Huang YC, Birla RK. Getting to the Heart of Tissue Engineering. J Cardiovasc Transl Res 2008; 1:71-84. [DOI: 10.1007/s12265-007-9005-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2007] [Accepted: 12/21/2007] [Indexed: 10/22/2022]
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Abstract
It has been hypothesized that repetitive flexural stresses contribute to the fatigue-induced failure of bioprosthetic heart valves. Although experimental apparatuses capable of measuring the bending properties of biomaterials have been described, a theoretical framework to analyze the resulting data is lacking. Given the large displacements present in these bending experiments and the nonlinear constitutive behavior of most biomaterials, such a formulation must be based on finite elasticity theory. We present such a theory in this work, which is capable of fitting bending moment versus radius of curvature experimental data to an arbitrary strain energy function. A simple finite element model was constructed to study the validity of the proposed method. To demonstrate the application of the proposed approach, bend testing data from the literature for gluteraldehyde-fixed bovine pericardium were fit to a nonlinear strain energy function, which showed good agreement to the data. This method may be used to integrate bending behavior in constitutive models for soft tissue.
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Affiliation(s)
- Mark A Nicosia
- Department of Mechanical Engineering, Widener University, Chester, PA, USA.
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Hecker L, Birla RK. Engineering the heart piece by piece: state of the art in cardiac tissue engineering. Regen Med 2007; 2:125-44. [PMID: 17465746 DOI: 10.2217/17460751.2.2.125] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
According to the National Transplant Society, more than 7000 Americans in need of organs die every year owing to a lack of lifesaving organs. Bioengineering 3D organs in vitro for subsequent implantation may provide a solution to this problem. The field of tissue engineering in its most rudimentary form is focused on the developed of transplantable organ substitutes in the laboratory. The objective of this article is to introduce important technological hurdles in the field of cardiac tissue engineering. This review starts with an overview of tissue engineering, followed by an introduction to the field of cardiovascular tissue engineering and finally summarizes some of the key advances in cardiac tissue engineering; specific topics discussed in this article include cell sourcing and biomaterials, in vitro models of cardiac muscle and bioreactors. The article concludes with thoughts on the utility of tissue-engineering models in basic research as well as critical technological hurdles that need to be addressed in the future.
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Affiliation(s)
- Louise Hecker
- Cell and Developmental Biology, The University of Michigan, Ann Arbor, MI 48109, USA
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Breuer CK, Mettler BA, Anthony T, Sales VL, Schoen FJ, Mayer JE. Application of tissue-engineering principles toward the development of a semilunar heart valve substitute. ACTA ACUST UNITED AC 2005; 10:1725-36. [PMID: 15684681 DOI: 10.1089/ten.2004.10.1725] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Heart valve disease is a significant medical problem worldwide. Current treatment for heart valve disease is heart valve replacement. State of the art replacement heart valves are less than ideal and are associated with significant complications. Using the basic principles of tissue engineering, promising alternatives to current replacement heart valves are being developed. Significant progress has been made in the development of a tissue-engineered semilunar heart valve substitute. Advancements include the development of different potential cell sources and cell-seeding techniques; advancements in matrix and scaffold development and in polymer chemistry fabrication; and the development of a variety of bioreactors, which are biomimetic devices used to modulate the development of tissue-engineered neotissue in vitro through the application of biochemical and biomechanical stimuli. This review addresses the need for a tissue-engineered alternative to the current heart valve replacement options. The basics of heart valve structure and function, heart valve disease, and currently available heart valve replacements are discussed. The last 10 years of investigation into a tissue-engineered heart valve as well as current developments are reviewed. Finally, the early clinical applications of cardiovascular tissue engineering are presented.
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Williams TH, Jew JY. Is the mitral valve passive flap theory overstated? An active valve is hypothesized. Med Hypotheses 2004; 62:605-11. [PMID: 15050115 DOI: 10.1016/j.mehy.2003.12.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2003] [Accepted: 12/11/2003] [Indexed: 11/22/2022]
Abstract
The concept that the mitral valve of the heart is a passive flap that opens and closes like a barn door has been emphasized for decades by medical and biology professors to their students. But experimental findings, which are outlined in this report, support the theory of an active valve. We hypothesize that the two leaflets of the mitral valve are actively contractile; that physical forces generated in the valve itself may stabilize and add precision to the sum of forces that regulate valve movement. This precision could be of critical significance both in the moments preceding, and during, valve opening and closing. Evidence supporting our active valve hypothesis includes the profuse innervation of motor and sensory nerves that are present in the mitral valves of all animals studied. In addition, multiple contractile cell types have been found in the mitral valve, including cardiac muscle cells, smooth muscle cells, and cardiac valvular interstitial cells. In vitro work in our laboratories using the rat mitral valve shows that not only are the valves capable of contraction and relaxation, but that the contractions and relaxations are nerve-mediated. We theorize that the rich innervation and contractile cells in the mitral valve work together to modulate fine-tuning of valve movements and tone, thereby ensuring the integrity of the valve seal. Other investigators have reported that the mitral valve demonstrates contractile activity and that denervation localized to the mitral valve affects valve competence. The evidence for an active mitral valve presented by these and other experimental studies warrant a reexamination of the validity of the passive valve concept. An accurate and full understanding of the precise movements of the valve leaflets and the mechanisms that regulate these movements is likely to provide the information needed to understand and develop treatments for many different cardiac valve problems, including mitral valve diseases such as prolapse and myxomatous degeneration. In view of the available experimental evidence, the concept that the mitral valve functions only as a passive structure is challenged by numerous anomalies. A reinterpretation of the concept of valve function that incorporates active as well as passive roles for the valve leaflets and other components of the valve apparatus would have significant implications both for the directions taken in research involving the cardiac valves and for the approaches to treatment.
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Affiliation(s)
- T H Williams
- Department of Anatomy and Cell Biology, University of Iowa, 1-449 Bowen Science Building, Iowa City, IA 52242, USA.
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Abstract
The search for the ideal therapy for valve replacement continues. The major options include mechanical or tissue valves, with an increasing variety of tissue valves becoming available. The key factor continues to be thrombogenicity versus durability. Aortic valve surgery primarily consists of replacement. This is aided by the increased variety of options allowing tailoring of the procedure to the patient's native valve disease. Mitral valve surgery has greater potential for repair, which affords preservation of the native valve, optimizing function and reducing long-term complications. An increasingly popular concept is treatment of secondary or functional mitral valve regurgitation in the setting of depressed left ventricular function. The routine use of intraoperative transesophageal echocardiography and a trend toward the use of minimally invasive procedures are altering the conduct of valve operations.
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Affiliation(s)
- Edward Y Sako
- University of Texas Health Science Center at San Antonio, Mail Code 7841, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA.
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Russell D, Brucher R. Online automatic discrimination between solid and gaseous cerebral microemboli with the first multifrequency transcranial Doppler. Stroke 2002; 33:1975-80. [PMID: 12154248 DOI: 10.1161/01.str.0000022809.46400.4b] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE The aim of this study was to assess the first multifrequency transcranial Doppler system that was specially developed to automatically detect and discriminate between solid and gaseous cerebral microemboli. METHODS The multifrequency transcranial Doppler instrumentation insonates simultaneously with 2.5 and 2.0 MHz. Differentiation between solid and gaseous microemboli is based on the principle that solid microemboli reflect more ultrasound at the higher than at the lower frequency, whereas the opposite is the case for gaseous microemboli. In the in vitro studies, 159 plastic spheres (50 or 80 micro m in diameter) and 105 gas bubbles (8 to 25 micro m) were studied in a pulsatile closed-loop system containing irodinium or pig blood. In vivo studies were carried out for 1 hour in 15 patients with mechanical heart valves and in 45 patients with carotid stenosis. This gave a total of 60 hours of online automatic monitoring in patients. RESULTS In the in vitro studies, 152 of the 159 (95.6%) plastic spheres were classified as solid, and 7 (4.4%) were classified as uncertain solid. Of the 105 gas bubbles, 99 (94.3%) were classified as gaseous and 6 (5.7%) as uncertain gaseous. Thus, correct classification was made for 251 (95.1%) of the 264 embolic events studied. A comparison between the automatic multifrequency discrimination and the known embolic classification gave a kappa value of 0.897 (P<0.0001). The multifrequency Doppler classified 433 (84.2%) of the 514 emboli detected in the mechanical heart valve patients as gaseous, 74 (14.4%) as solid, and 7 (1.4%) as uncertain (3 uncertain solid, 4 uncertain gas). Thirty-two emboli were detected in 17 (38%) of the 45 carotid stenosis patients; 30 (93.7%) were classified as solid and 2 (6.3%) as uncertain solid. CONCLUSIONS This study has shown that multifrequency transcranial Doppler can be used to automatically differentiate between solid and gaseous microemboli online. Most detected microemboli in this initial study of mechanical heart valves were classified as gaseous, whereas most were classified as solid in the patients with carotid stenosis.
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Affiliation(s)
- David Russell
- Department of Neurology, the National Hospital, Oslo, Norway.
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Borovetz HS, Burke JF, Chang TMS, Colas A, Cranin AN, Curtis J, Gemmell CH, Griffith BP, Hallab NJ, Heller J, Hoffman AS, Jacobs JJ, Ideker R, Katz JL, Kennedy J, Lemons JE, Malchesky PS, Morgan JR, Padera RE, Patel AS, Reffojo MF, Roby MS, Rohr TE, Schoen FJ, Sefton MV, Sheridan RT, Smith DC, Spelman FA, Tarcha PJ, Tomapkins RG, Venugopalan R, Wagner WR, Yager P, Yarmush ML. Application of Materials in Medicine, Biology, and Artificial Organs. Biomater Sci 1996. [DOI: 10.1016/b978-012582460-6/50010-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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