First Results of a Stented Completely Tissue-Engineered Pulmonary Valve Replacement for Transcatheter Implantation in an Intermediate-Term Sheep Model

Background: Many congenital heart defects require pulmonary valve replacement in early childhood and reoperation due to valve-to-body mismatch during adolescence. Thus, a pulmonary valve replacement with growth potential is desirable.

Methods: Over the past 4 years in a European consortium, an autologous decellularized tissue-engineered heart valve (dTEHV) was produced on the basis of a bioresorbable polymeric scaffold and sewn into a self-expandable stent. To implant this pulmonary valve prosthesis transcutaneously, a catheter delivery system was designed and custom made.

Fifteen adult sheep underwent computed tomography prior to implantation for assessment of native valve and vessel diameters. At implantation day, angiography and intracardiac echocardiography were performed via jugular vein access to monitor native pulmonary valve function and size. The same access was used to advance the dTEHV stent to the pulmonary valve position. After deployment, intracardiac echocardiography and angiography were applied again to report on position and function of the dTEHV stent. Animals were grouped for 8-, 16-, and 24-week survival. During that period, CT and intracardiac echocardiography were repeated on a 4-week interval.

Results: The prototype delivery system worked at first attempt in three-fourths of the implantations. In the rest, minor changes were required. In all animals, the stented dTEHV was implanted successfully. Nevertheless, only approximately 25% of the valves were fully competent directly after implantation. The main part of the valves showed mild-to-moderate insufficiency from the beginning with aggravation over time. Three-dimensional scaffolds, namely, valve design and active ongoing changes in the tissue structure of the valve caused by recipients' cell invasion seem to be the major causes for valve failure. A redesign is required.