Biology of the Sinus Node and its Disease.

The sinoatrial node (SAN) is the normal pacemaker of the heart and SAN dysfunction (SND) is common, but until recently the pathophysiology was incompletely understood. It was usually attributed to idiopathic age-related fibrosis and cell atrophy or ischaemia. It is now evident that changes in the electrophysiology of the SAN, known as electrical remodelling, is an important process that has been demonstrated in SND associated with heart failure, ageing, diabetes, atrial fibrillation and endurance exercise. Furthermore, familial SND has been identified and mutations have been characterised in key pacemaker genes of the SAN. This review summarises the current evidence regarding SAN function and the pathophysiology of SND.