Sick sinus syndrome usually occurs in people older than 50. The cause is often scar-like damage to the heart's conduction system
In children, a common cause of sick sinus syndrome is heart surgery, especially on the upper chambers.
Coronary artery disease, high blood pressure, and aortic and mitral valve diseases may occur with sick sinus syndrome, although these diseases may have nothing to do with the syndrome.
Sick sinus syndrome is uncommon. Sinus bradycardia occurs more often than the other types.
Tachycardias that start in the upper chambers of the heart may be part of the syndrome. These include atrial fibrillation, atrial flutter, and atrial tachycardia. A period of elevated heart rates is typically followed by very slow heart rates when the tachycardia ends.