LAUSR

Post-operative atrial fibrillation (POAF) is assumed as a complex and multifactorial interaction of different pathogenic factors. Data suggests an inflammatory process as a main trigger of this specific type of atrial fibrillation. CD8+ T lymphocytes that lack the surface protein CD28 were found to be crucially involved in chronic inflammatory processes within the cardiovascular system. Of utmost interest, these so called CD8+CD28null T cells are known to present with auto-aggressive behavior and deleterious cytotoxic effects on human tissue. Therefore, the impact of cellular immunity on the development of POAF was sought to assess. To elucidate the impact of cellular immunity on the development of POAF, we prospectively enrolled 129 patients undergoing elective cardiac valve and/or coronary-artery-bypass-graft surgery. Fluorescein-activated cell sorting (FACS) was performed to investigate lymphocyte subsets. Patients were stratified in two subgroups according to patients developing POAF (n=60) and individuals free of POAF (n=69). Binary logistic regression analysis was performed to assess the impact of cellular immunity on the development of POAF. Comparing patients developing POAF to individuals free of POAF the fraction of CD8+ lymphocytes was significantly higher in individuals developing POAF (30.5% [POAF] vs. 25.7% [non-POAF]; p=0.021) Interestingly, the fraction of CD8+CD28nullT-lymphocytes was significantly higher in the POAF sub-group (66.7% [POAF] vs. 61.6% [non-POAF]; p=0.043). Binary logistic regression further proved that the fraction of CD8+CD28null T cells was a strong prognosticator for the development of POAF with a crude odds ratio per one standard deviation of 3.45 (95% CI 1.11–10.70; p=0.032). The prognostic potential remained stable after adjustment for potential confounders (age, male gender and type of surgery) within the multivariate model with an adjusted odds ratio per one standard deviation of 3.21 (95% CI 1.01–10.18; p=0.048). We found that cytotoxic CD8+CD28null T lymphocytes proved to be a strong and independent predictor for the development of POAF after elective cardiac surgery. Our results potentially indicate an auto-immune impact of this preexisting, highly cytotoxic T cell subset in the pathogenesis of POAF. Verein zur Förderung der Forschung – Atherosclerosis Thrombosis and Vascular Biology (Vienna, Austria)