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).

Because the heart’s electrical system is complicated, diagnosing abnormal heart rhythm (arrhythmias) can be difficult and requires heart rhythm experts who use special testing equipment. To find the problem, a doctor will take a medical history, ask about symptoms, give a thorough physical exam, and order specific tests. 



Fainting (syncope) is a sudden transient loss of consciousness. It most often happens when the blood pressure is too low (hypotension) and the heart does not pump enough oxygen to the brain. Typically, a fainting spell lasts only a few seconds or minutes, and then the person regains consciousness. Fainting is common and a single spell usually is not serious.