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Ann Thorac Surg 2007;83:654
© 2007 The Society of Thoracic Surgeons
Department of Cardiovascular Surgery, Medical University Berlin, Luisenstrasse 13, Berlin, D-10117 Germany
(Email: pascal.dohmen{at}charite.de).
Today’s treatment of complex congenital cardiovascular defects of the right ventricular outflow tract, such as hypoplastic, stenotic right ventricular outflow tract, or the pulmonary artery in tetralogy of Fallot, are far from optimal as generally nonviable patch materials are used. This results in repeated surgical intervention for two reasons. First, the patch reconstruction and the absence of a functional pulmonary valve will lead to right ventricular failure, increased tricuspid valve regurgitation, and ventricular arrhythmias. Second, material degeneration will result in obstructive pannus overgrowth and calcification after implantation.
Tissue engineering can overcome these disadvantages using a biodegradable scaffold that can be in vitro or in vivo re-cellularized to allow regeneration, remodeling, and growth potential.
The present study by Fujimoto and colleagues [1] compared an elastomeric, biodegradable polyester urethane urea (PEUU) patch with a generally used expanded polytetrafluoroethylene (e-PTFE) patch implanted into the right ventricular outflow tract. This study, performed in the rat model, showed the superiority of the PEUU patches compared with the e-PTFE patches. The PEUU material showed high elasticity and strength and porous scaffold, allowing host fibroblast to grow into the scaffold and active synthesize collagen. In contrast there was no host cell ingrowth in the e-PTFE patch. Furthermore the PEUU scaffold was nearly completely absorbed after 12 weeks of implantation.
Therefore the authors need to be congratulated for this performed study as the goal of tissue engineering has almost been completely achieved. Regeneration and remodelling potential of this biodegradable patch has been proven. Future studies will be needed, eventually in the larger animal model, to show growth potential as suggested by the authors.
The impact of the biodegradable patch implanted into the right ventricular outflow tract needs to be discussed. At this early stage of right ventricular outflow tract treatment, pulmonary allografts show fast tissue degeneration and (due to the absence of viability) an outgrowth of the valve size by the patient after a short period of time. Therefore patch reconstruction of the right ventricular outflow tract is generally used to bridge the patient until a reasonable valve size can be implanted. Quality of life is limited for the patient until a valve has been implanted not to overestimate the right ventricular function. For this reason, tissue engineering should concentrate on developing a valve with regeneration, remodeling, and growth potential to overcome patch reconstruction and to allowing one-stage surgical treatment.
The area of interests for biodegradable patch use would be more of those complex congenital heart diseases without the need of a valve function such as repair of complete atrioventricular communication, the Fontan procedure, enlargement of the aorta in the Norwood I procedure, or complex repair of coarctation of the thoracic aorta.
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