Sick Sinus Syndrome. SSS is not a specific disease, but a group of signs or symptoms that indicate the heart's natural electrical pacemaker, the sinoatrial node, is not functioning properly. In SSS, the heart rate can switch back and forth between a slow rate (bradycardia) and a fast rate (tachycardia). A permanent pacemaker, sometimes in combination with medication, is the primary treatment. SSS affects about 3 out of every 10,000 people. It becomes more common as we age.