An 11-year assessment of 93 flash-frozen homograft valves in the aortic position.

Flash-frozen homograft aortic valves were used for isolated aortic valve replacement at the National Heart Hospital between 1968 and 1971. This study of 93 patients with an average follow-up of 8.5 years complements a previous report on 30 patients but shows a higher incidence of degeneration. There was an early mortality of 4.8% and a late mortality of 15.9% over 11 years. Only five of the 15 late deaths were directly attributable to valve malfunction. There were no episodes of thromboembolism during the 11 year follow-up and only three cases of infective endocarditis. Despite the late onset of valve degeneration there is a 77% probability of patient survival at 11 years. The use of frozen valves delayed the time of onset of degenerative changes when compared over an 11-year period with the earlier use of freeze-dried valves. The evaluation of replacement cardiac valves is thus seen to be time-dependent and needs a long follow-up and an adequate number of patients in the sample for a meaningful assessment. There was no significant difference in the long-term performance between the frozen valves sterilized in ethylene oxide or sterilized with gamma irradiation.