Interestingly, in RAA myocardium of the AF + IAA patients the number of CD68-positive histiocytes and TCs-like cells with histiocyte signs was on average 7.04 ± 1.4% (median 7.22%) of cells and significantly exceeded the proportion of these cells in the AF group (4.5 ± 2.5%, median 4.2%) (Mann–Whitney test, p < 0.05) (Fig. 7i). The gene discussed is CD68; the disease is atrial fibrillation.