6th March 2024

Sick sinus syndrome/SA node disease

This is caused by dysfunction of the heart’s natural pacemaker and can manifest on an ECG as sinus bradycardia, SA exit block, or sinus pauses. Causes can be intrinsic or extrinsic. The most common intrinsic cause is idiopathic degenerative fibrosis of the SA node cells. Other causes include ischaemia due to right coronary artery occlusion. 

Extrinsic factors include negatively chronotropic medications such as digoxin or beta-blockers, hypothyroidism and electrolyte abnormalities. Treatment for symptomatic disease is with the implantation of a permanent pacemaker. A common manifestation of sinus node disease is termed tachy-brady syndrome. This is where an SVT such as atrial fibrillation, flutter or atrial tachycardia coincides with the presence of sick sinus disease, resulting in periods of tachycardia alongside periods of bradycardia, pauses, or escape rhythms. This is managed with pacemaker insertion.