For neonates undergoing cardiac surgery does thymectomy as opposed to thymic preservation have any adverse immunological consequences?

Abstract

A best evidence topic in congenital cardiac surgery was written according to a structured protocol. The question addressed was whether neonatal thymectomy in patients undergoing cardiac surgery has any adverse immunological consequences. Altogether 164 papers were found using the reported search, of which nine papers represented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses were tabulated. The thymus is the major production site of T cells, whose stocks are built-up during foetal and early postnatal life. However, its function diminishes after the first years of life, and although thymic output is maintained into adulthood, the thymus mostly degenerates into fatty tissue in elderly adults. To date, there has been no general consensus with regard to the importance of this organ during childhood and adulthood. As a consequence, during cardiac surgery in neonates, partial or total thymectomy is routinely performed to enable better access to the heart and great vessels to correct congenital heart defects, suggesting that it may be dispensable during childhood and adulthood. Interestingly, current best available evidence from nine case-control studies suggests that neonatal thymectomy affects peripheral T-cell populations both in the short- as well as long-term and results in premature immunosenescence. However, the impact of these changes on the risk of infectious diseases or malignancy has not been thoroughly evaluated by any of these studies. Maintenance of a registry of patients undergoing neonatal thymectomy and further studies to assess the functional or clinical consequences of this practice would be valuable.