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Development of an Animal Experimental Model for a Bileaflet Mechanical Heart Valve Prosthesis

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      Abstract

      The objective of this study was to develop a pre-clinical large animal model for the in vivo hemodynamic testing of prosthetic valves in the aortic position without the need for cardiopulmonary bypass. Ten male pigs were used. A composite valved conduit was constructed in the operating room by implanting a prosthetic valve between two separate pieces of vascular conduits, which bypassed the ascending aorta to the descending aorta. Prior to applying a side-biting clamp to the ascending aorta for proximal grafting to the aortic anastomosis, an aorta to femoral artery shunt was placed just proximally to this clamp. The heart rate, cardiac output, Vmax, transvalvular pressure gradient, effective orifice area and incremental dobutamine stress response were assessed. A dose dependant increase with dobutamine was seen in terms of cardiac output, Vmax, and the peak transvalvular pressure gradient both in the native and in the prosthetic valve. However, the increment was much steeper in the prosthetic valve. No significant differences in cardiac output were noted between the native and the prosthetic valves. The described pre-clinical porcine model was found suitable for site-specific in-vivo hemodynamic assessment of aortic valvular prosthesis without cardiopulmonary bypass.

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      Most cited references 22

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      Successful prosthetic mitral valve implantation in pigs.

       D Gross,  M Dewanjee,  P Zhai (2016)
      Clotting mechanisms, the coagulation cascade, platelet function, and platelet-leukocyte-endothelial cell interactions are all very similar in humans and pigs. Because of these similarities, the authors concluded that the pig would be an ideal model for the study of thromboembolism resulting from prosthetic heart valves. To date, they have successfully recovered a total of 11 pigs (52.9 +/- 8.1 kg), 3 with bioprosthetic valves and 8 with mechanical valves, all in the mitral position (25 mm od). The normal presence of high numbers of pulmonary endothelial macrophages and other unique aspects of porcine cardiovascular and pulmonary function dictate somewhat different surgical protocols than those normally used for human patients and ruminant species. Some of these special procedures include 1) crystalloid prime without the use of plasma volume expanders, especially those with a starch base; 2) pharmacologic protection against arrhythmias (lidocaine, 4 mg/kg); 3) special attention to adequate hypothermic cardioprotection during the time of cross-clamp; 4) the use of shock doses of corticosteroid (prednisolone sodium succinate, 0.5 mg/kg) before removal of the aortic cross-clamp; and 5) positive inotropic support (dopamine, 0.008 mg/kg) while weaning from cardiopulmonary bypass. Gamma camera images of 111In tagged autologous platelets 24 hours after surgery show most thrombi located on the sewing ring with fewer on the pledgets and anchor sutures. The latter observations were confirmed by quantification of platelet deposition using a gamma counter.
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        Current state of in vivo preclinical heart valve evaluation.

        The use of animals to predict prosthetic valve performance in humans has now been in operation for over 25 years. Studies have focused on improvements in structural integrity, anti-thrombogenicity and anticalcification, and provide extensive in vivo analysis and validation of a valve before its clinical evaluation. Many animal models have been developed for such investigations, including calves, goats, pigs, baboons, dogs and adult sheep. Recent models used to assess prosthetic mitral valves have involved site-specific testing in several species; the present study represents the largest series of orthotopically implanted stentless bioprosthetic aortic valves and the first to utilize a juvenile sheep model for the aortic position.
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          Hemodynamic evaluation of a new bileaflet valve prosthesis: an acute animal experimental study.

           K Terp,  P Paulsen,  C Riis (1996)
          A newly developed heart valve (Medtronic Parallel) was tested in an acute animal experimental model. Five prototype valves were implanted in the aortic position in seven 90 kg pigs to enable acute evaluation of the hemodynamic performance in terms of turbulent stresses and transvalvular pressure drop. Turbulent stresses in the ascending aorta were measured using a 10 MHz perivascular Doppler echocardiographic transducer designed to measure the radical velocity component at 17 different points covering the aortic cross-sectional area. The drop in transvalvular peak pressure measured with fluid-filled catheters showed a non-linear relationship with cardiac output and was always < 12 mmHg. The Reynolds normal stresses were < 60 N/m2 in systole within 50 ms time windows, which is insufficient to cause mechanical damage of the formed elements of the blood. From a hemodynamic point of view the performance of the Medtronic Parallel aortic valve is fully acceptable and within the range of other similar, currently available mechanical valves.
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            Author and article information

            Affiliations
            Department of Thoracic & Cardiovascular Surgery, Asan Medical Center, University of Ulsan, Seoul, Korea.
            [* ]Department of Internal Medicine, Division of Cardiology, Asan Medical Center, University of Ulsan, Seoul, Korea.
            []Department of Anesthesia, Asan Medical Center, University of Ulsan, Seoul, Korea.
            []Department of Mechano-Informatics & Design Engineering, College of Science and Technology, Hongik University, Seoul, Korea.
            [§ ]College of Mechanical and Industrial System Engineering, Kyunghee University, Seoul, Korea.
            Author notes
            Address for correspondence: Jae Won Lee, M.D. Department of Thoracic & Cardiovascular Surgery, Asan Medical Center, University of Ulsan, College of Medicine, 388-1 Poongnap-dong, Songpa-gu, Seoul 138-040, Korea. Tel: +82.2-3010-3580, Fax: +82.2-3010-6966, jwlee@ 123456amc.seoul.kr
            Journal
            J Korean Med Sci
            JKMS
            Journal of Korean Medical Science
            The Korean Academy of Medical Sciences
            1011-8934
            1598-6357
            February 2004
            28 February 2004
            : 19
            : 1
            : 37-41
            2822261
            10.3346/jkms.2004.19.1.37
            14966339
            Copyright © 2004 The Korean Academy of Medical Sciences

            This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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