GEOMETRY OF HOMOGRAFT VALVE LEAFLETS - EFFECT OF DILATION OF THE AORTA AND THE AORTIC ROOT

With the increasing interest in aortic homografts as either a free-sew n valve or whole-root replacement, the effect of internal pressure and dilation of the aorta and aortic root on valve leaflet geometry has b een studied. Seven aortic homograft roots were studied, six that had b een stored in antibiotics and one that had been cryopreserved. The dia meter of the aorta was determined as a function of internal pressure a nd correlated with the stress-strain characteristics of the aortic wal l. Three-dimensional leaflet surface geometry was measured in the ''ne utral'' position, and the leaflet was characterized by its radius of c urvature and angle of inclination, using a cylindrical model. The diam eter of the aorta increased by between 30% and 50% as the dilation pre ssure increased from 0 to 120 mm Hg. This was consistent with the stre ss-strain data obtained from strips of the aortic wall in the circumfe rential direction. The angle of inclination of the leaflet increased f rom 20 to 80 degrees and the radius of curvature increased from 4 to 1 7 mm as the internal pressure increased from 0 to 80 mm Hg. The open l eaflet configuration showed a triangular orifice with low bending stra ins for a dilated root, but increased bending strains with reduced dil ation pressure. These are important considerations when implanting a f ree-sewn homograft into the aortic root.