Sick sinus syndrome most often occurs in people older than 50. It is often due to scar-like damage to electrical pathways in the heart muscle tissue.
In children, heart surgery on the upper chambers is a common cause of sick sinus syndrome.
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 of the condition.
Tachycardias that start in the upper chambers of the heart may be part of the syndrome. These include atrial fibrillation, atrial flutter, atrial tachycardia, and other types of fast heart rates. A period of fast heart rates is often followed by very slow heart rates immediately after the tachycardia ends.
Some medicines can make abnormal heart rhythms worse. These include digitalis, calcium channel blockers, beta-blockers, and anti-arrhythmics.