024 Cryopreservation management and its impact on graft function with heart valve allograft

Abstract

Cryopreserved aortic valve allograft (homograft) is a graft of choice in managing aortic root replacement (ARR) surgery for critical infective endocarditis (IE). Homografts provide favorable clinical outcome in terms of regulating infection in preoperative period and providing superior hemodynamic performance because of their natural structure, however, long-term graft durability is still a matter of discussion, and reoperation is considered very challenging in those cases. Among the possible factors that may influence long-term graft durability and function, we reviewed homograft-oriented factors including their storage period along with the long-term clinical outcome of the patients receiving homograft ARR for IE cases. Patients undergoing homograft ARR for critical IE were reviewed for recipients’ preoperative profile and postoperative short and long term results including redo aortic valve replacement (AVR). The information of implanted homograft tissue including donor age, gender, blood type, warm ischemic time (WIT), and duration of storage at tissue bank (−180 °C) until use. Long-term results were evaluated among the patients who were able to be discharged home after the surgery. Cryopreserved homografts were prepared using programmable freezer with freezing rate of −1 °C/min until −80 °C, and stored at vapor phase of liquid nitrogen under temperature control between −170 and −180 °C. Before 2006, liquid nitrogen was supplied manually, and it was supplied automatically after 2006. Student t -test was performed to compare 2 groups (DR and HI), and long-term results were evaluated by Kaplan Meier curve, with p < 0.05 being statistical significance. From December 1998 through April 2013, there were 37 consecutive patients including 34 prosthetic valve endocarditis cases (92%). Thirty patients were male (81%), and average age was 55 ± 13 years. Twenty-eight cases (75%) presented annular destruction with abscess formation. In-hospital mortality was 16.2% (6/37) including 3 cases lost within 30 days after surgery (30-day mortality 8.1%). Seven cases underwent redo aortic valve replacement in the late period for degenerative change of the valve leaflets and IE of the homografts. Gender and blood type mismatch were seen in 18 (49%) and 8 cases (22%) respectively, and these factors did not have any impact on valvular impairment requiring redo AVR, and so was WIT. Average storage period of the grafts was 708 days, and there was a significant difference between those who required redo AVR and those who did not (242 days vs. 840 days, p < 0.0001). Six tissues which required redo AVR was stored in the tank with periodical manual supply of liquid nitrogen, and 1 tissue was in the tank with automatic supply. Long-term overall cumulative survival at 1/5/10/14 year were 92.7/74.5/61.2/61.2% respectively. Freedom from redo AVR at1/5/10/14 year were 92.6/79.5/79.5/39.7%. Long-term durability of the homografts was satisfactory, which is almost reaching to the value of bioprosthetic valves. Automatic liquid nitrogen supplying system may be beneficial in quality control of the heart valve tissues. Source of funding: None declared. Conflict of interest: None declared. ayasaitou-ths@umin.ac.jp