Fig. 2

Immunohistochemical integrated optical density analysis of YKL-40 expression in the adipose tissue of patients with atrial fibrillation (AF, n = 28) and sinus rhythm (SR, n = 36). a Representative sections of three types of adipose tissue in the AF and SR groups. The EAT of AF group was obviously more evident in staining. b Quantitative results of IOD in sections of three types of adipose tissue in the AF and SR groups. *P = 0.007, **P < 0.001. SAT subcutaneous adipose tissue, PAT paracardial adipose tissue, EAT epicardial adipose tissue