Aortic allograft infection risk.

Objective: Intrinsic risk of infection of cryopreserved allograft aortic root replacements remains 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 nonendocarditis indications and infective endocarditis.

Methods: From January 1987 to January 2017, 2042 patients received 2110 allograft aortic valves at a quaternary medical center, 1124 (53%) for nonendocarditis 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 end point was allograft infection in patients with nonendocarditis and endocarditis indications. Risk factors were identified by hazard function decomposition and machine learning.

Results: During follow-up, 30 allografts (26 explanted) became infected in patients in the nonendocarditis group and 49 (41 explanted) in patients with endocarditis. At 20 years, the probability of allograft infection was 5.6% in patients in the nonendocarditis group and 14% in patients with endocarditis. Risk factors for allograft infection in patients in the nonendocarditis group were younger patient age and older donor age. Risk factors for allograft infection in patients with endocarditis were earlier implant year, injection drug use, and younger age. In patients with endocarditis, 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 invasive endocarditis of the aortic root.