sentences:  Cardiovascular diseases represent a major cause of worldwide mortality, and the relevance of the genetic component in these diseases has recently become more apparent.Genetic alterations of HCN4 channels (the molecular correlate of sinoatrial f-channels) coupled to rhythm disturbances have been reported in humans.For example, an inherited mutation of a highly conserved residue in the CNBD of the HCN4 protein (S672R) is associated with inherited sinus bradycardia.