CASP3 and atrial fibrillation: Immunofluorescence study revealed a significant co-localization and juxtaposition of the expression of ROCK2 and the expression of cleaved caspase-3 in the left atrial myocytes both in the MR AF group (Pearson’s coefficient = 0.74 ± 0.03) and the MR sinus group (Pearson’s coefficient = 0.73 ± 0.02) (Fig. 5), indicating the existence of potential interaction between ROCK2 and cleaved caspase-3 and confirmation of caspase-dependent activation of ROCK2 in the left atrial myocytes of MR patients, and this interaction might be involved in the pathogenesis of left atrial myolysis in MR patients.