Sinus Node Dysfunction

Excerpt

The sinoatrial node (SA) node is the dominant pacemaker of the heart. It is a complex compact region in the junction of superior vena cava and the right atrium. The SA node depolarizes and produces action potential almost synchronously.

Sinus node dysfunction, also known by its historical name sick sinus syndrome, is the inability of the SA node to produce an adequate heart rate that meets the physiologic needs of the individual. Per definition, sinus node dysfunction should include symptoms and EKG findings simultaneously such as sinus bradycardia, sinus pauses or arrest, sinus exit blocks, or chronotropic incompetence (inadequate heart rate response to activity). Or the failure of the return of SA nodal activity after electrical cardioversion. Sinus node dysfunction can be associated with atrial tachycardia as part of the tachycardia-bradycardia syndrome.