HCN4 and cardiac arrhythmia: Thus, myocardial structural abnormalities could be closely associated with HCN4 mutations, leading to the development of cardiac arrhythmias via phosphatidyl-inositol 3,4,5-trisphosphate (PIP3) signal transduction mechanism; regulating the function of funny current, controlling the pacemaker activity and heart rate in the myocardium (Difrancesco, 2019).