HCN4 and heart conduction disease: CHB might have the background of complex pathophysiological processes related to certain genetic variants of genes and gene network coding ion channels, including SCN5A, SCN1B, SCN10A, TRPM4, KCINK17, CAVB, KCNJ2, HCN4, LMNA, ANKB, NKX2-5, TBX5, and cardiac connexin proteins, leading to isolated AV block or to progressive cardiac conduction disease with various intraventricular conduction disturbances [1,16,17].