Sick sinus syndrome (SSS) is a relatively uncommon heart rhythm disorder. SSS is not a specific disease, but rather a group of signs or symptoms that indicate the sinus node, the heart’s natural pacemaker, is not functioning properly. A person with SSS may have a heart rhythm that is too slow (bradycardia), too fast (tachycardia), or one that alternates between the fast and slow (bradycardia-tachycardia).
The sinus node is a specialized group of cells in the upper chamber of the heart, the atria, that creates electrical signals that regulate the pace and rhythm of the heartbeat. Normally, the sinus node produces a regular, steady pattern of signals. With SSS, the pattern is irregular. Sick sinus syndrome may be due to defects in the heart itself, or it can be related to factors outside the heart.
Most people with sick sinus syndrome have few or no symptoms. In others, symptoms may come and go. These symptoms can include:
While the exact cause of SSS is unknown, some factors, however, often are associated with the condition, such as:
In rare cases, SSS may be associated with conditions such as: