An 11-Year Assessment of 93 Flash-frozen Homograft Valves in the Aortic Position

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Abstract
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 followup 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.