Table 1: Summary of the Genes and Electrical Remodelling Involved in Some Causes of Sinus Node Dysfunction.

Causes of SND	Ion channels and genes involved
Idiopathic/ageing	↓Navv1.5,46 ↓Cx43,47 ↓Cav1.2,49 ↓RYR2,50 ↓HCN1,50,51 ↓HCN451
Atrial tachyarrhythmia	↓HCN2,57 ↓HCN457
Inherited	HCN4,58–62 SCN5A (Nav1.5),63 RYR2,66 CASQ2,65,66 ANKB67
Exercise training	↓HCN4,70 ↓Tbx370
Heart failure	↓HCN487

The inherited genes are mutations seen in human families with sinus node dysfunction (SND), whereas in other types of SND electrical remodelling was seen in animal models. Downward arrows mean downregulation.