progressive cardiac conduction defect progressive cardiac conduction defect progressive cardiac conduction defect (pccd) is a rare inherited degenerative disease of a heart's electrical conduction system. over time pccd can lead to a complete heart block and might require a pacemaker implantation to treat it. progressive cardiac conduction defectother namesfamilial lenègre disease, familial lev disease, familial lev-lenègre disease, familial pccd, familial progressive heart block, progressive familial heart block, hereditary bundle branch defectspecialtycardiology genetics most commonly pccd is inherited as a autosomal dominant defect and is caused by mutations of chromosome 19q13.3 and in scn5a, scn1b and trpm4 genes.