Our results revealed that cyclic stretch stimulated rat AF cells, thereby promoting the phosphorylation of IκBα and P65, decreasing the mitochondrial membrane potential, and promoting the overexpression of cleaved caspase-3 and caspase-9, which indicated that cyclic stretch activates the NF-κB pathway and causes apoptosis. This evidence concerns the gene CASP9 and atrial fibrillation.