Aortic Allograft Infection Risk

ABSTRACT Objective Intrinsic risk of infection of cryopreserved allograft aortic root replacements remain poorly understood despite their long history of use. The objective of this study was to determine this intrinsic risk of allograft infection and its risk factors when allografts are implanted for both non-endocarditis indications and infective endocarditis. Methods From January 1987 to January 2017, 2,042 patients received 2,110 allograft aortic valves at a quaternary medical center, 1,124 (53%) for non-endocarditis indications and 986 (47%) for endocarditis indications (670 [68%] prosthetic valve endocarditis). Staphylococcus aureus caused 193 of 949 cases of endocarditis (20%), 71 (7.3%) in persons who injected drugs. Periodic surveillance and cross-sectional follow-up achieved 85% of possible follow-up time. The primary endpoint was allograft infection in non-endocarditis and endocarditis patients. Risk factors were identified by hazard function decomposition and machine learning. Results During follow-up, 30 allografts (26 explanted) became infected in non-endocarditis patients and 49 (41 explanted) in endocarditis patients. At 20 years, the probability of allograft infection was 5.6% in non-endocarditis patients and 14% in endocarditis patients. Risk factors for allograft infection in non-endocarditis patients were younger patient age and older donor age, and in endocarditis patients, earlier implant year, persons who inject drugs, and younger patient age. In endocarditis patients, 18% of allograft infections were caused by the original organism. Conclusions The low infection rates, both in patients without and with endocarditis, support continued use of allografts in the modern era, in particular for the treatment of patients with invasive endocarditis of the aortic root.