Preparation and preservation of aortic valve grafts with special attention to problem areas

Abstract

Summary and conclusions Freeze-drying as a remedy for prolonged storage of homologous aortic valves was abandoned in this laboratory because of the appearance of gross cracks in the grafts and the lengthy time necessary for reconstitution of the graft for surgery. Because of problems involved in valve procurement and the need for avoiding wastage, another method, namely that of freezing to −80° C. has been explored, and the effects of freezing with different concentrations of glycerol in lactated Ringer's solution (LRS), and techniques of preparation, that is, trimming and sizing, on injury have been evaluated histologically in the calf and pig valves. Trimming had a negligible effect on valves, although sizing by Mandarin measurement caused general loss of endothelium over the ventricular leaflet surface, particularly at the level of the annulus. Separation or disruption of the elastic lamellae of the leaflet developed after Mandarin measurement. The use of any obturator type of valve sizer should be avoided. In general, there was less separation of loose connective tissue and shrinkage of surrounding cells with the use of 20 to 30 per cent glycerol. The portion of all specimens responding most dramatically to shrinkage was the myocardium. Because these findings in the calf and pig valves appear to be somewhat accentuated over those observed in human valves, it is recommended that if such heterologous valves are contemplated for clinical use they be stored in glycerol at −80° C. by semi-rapid freezing. The authors wish to thank Mr. Murray P. Sands and Mrs. Marian C. Hunner and the Surgical Chemistry Laboratory for their valuable assistance.