The disclosed methods pertain to diagnosing whether a non-ablative, gene therapy is needed for reducing AF fibrosis in a subject, and if so, methods of reducing AF fibrosis in a subject using gene therapy with a dominant negative TGF-β R2 cDNA expression vector. Kits and computer program products are also described, wherein the kits provide materials for diagnosing and treating AF fibrosis, and the computer program products include a computer readable medium having computer readable program code for monitoring the efficacy of therapeutic ablation of fibrosis in a subject using a gene therapy method.