MMLV-mediated Cx43 overexpression (MMLV-Cx43) in FB increased the formation of functional gap junctions in vitro and substantially lowered post-cryo-injury ventricular tachycardia incidence (by 50%), as demonstrated by in vivo electrophysiological testing 2 and 8 weeks after MMLV/MNP injection into the lesion. The gene discussed is GJA1; the disease is ventricular tachycardia.