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Decellularized homografts
Decellularized homografts are donated human heart valves which have been modified via tissue engineering. Several techniques exist for decellularisation with the majority based on detergent or enzymatic protocols which aim to eliminate all donor cells while preserving the mechanical properties of the remaining matrix.
== Background ==
Aortic valve disease affects the valve between the left ventricle and the aorta, and can be present as a congenital condition at birth or caused by other factors. Several therapeutic options are open to patients once the indication for aortic valve replacement has been confirmed. One option is replacement using a mechanical valve. This, however, necessitates a strict lifelong anticoagulation regime to avoid cerebral thromboembolism. These blood thinners hold an inherent risk for severe bleeding episodes, which affects both professional and leisure activities and the majority of patients opt against mechanical valves for this reason. Biological prostheses, i.e. pericardial heart valves of animal origin (xenogenic), offer a viable alternative. However, in particular for young patients, it has been found that xenogenic valves not provide satisfactory durability and rapid valve degeneration can occur within months.〔Svensson LG, Adams DH, Bonow RO, Kouchoukos NT, Miller DC, O'Gara PT, Shahian DM, Schaff HV, Akins CW, Bavaria JE, Blackstone EH, David TE, Desai ND, Dewey TM, D'Agostino RS, Gleason TG, Harrington KB, Kodali S, Kapadia S, Leon MB, Lima B, Lytle BW, Mack MJ, Reardon M, Reece TB, Reiss GR, Roselli EE, Smith CR, Thourani VH, Tuzcu EM, Webb J, Williams MR. Aortic valve and ascending aorta guidelines for management and quality measures. Ann Thorac Surg. 2013 Jun;95(6 Suppl):S1-66.〕
A further avenue open to patients is a so-called Ross operation, an extensive surgical procedure in which the diseased aortic valve is replaced by the patient`s pulmonary valve (autograft). The pulmonary valve then needs to be replaced by a heart valve prosthesis. A drawback of this method is that it can frequently result in a "two-valve" diseased heart, as almost all autografts are impaired by progressive dilatation in the long term, and the pulmonary valve prosthesis, often a conventional cryopreserved homograft, is subject to the same rate of degeneration as all biological valves. This can thereby leading to frequent reoperations〔Sievers HH, Stierle U, Charitos EI, Takkenberg JJ, Hörer J, Lange R, Franke U, Albert M, Gorski A, Leyh RG, Riso A, Sachweh J, Moritz A, Hetzer R, Hemmer W. A multicentre evaluation of the autograft procedure for young patients undergoing aortic valve replacement: update on the German Ross Registry. Eur J Cardiothorac Surg. 2015 Feb (ahead of print )〕 which have a substantially higher mortality rate due to postoperative adhesions.〔Onorati F et al. Mid-term results of aortic valve surgery in redo scenarios in the current practice: results from the multicentre European RECORD (REdo Cardiac Operation Research Database) initiative. Eur J Cardiothorac Surg. 2014 Mar 30.〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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