Sick sinus syndrome is not a single disease, but the term used for a group of abnormal heart rhythms caused by problems with a sinus node, also called the sinoatrial, or SA node, in the heart. The sinus node is located in the atrium, or upper chamber, of the heart. The cells within the SA node act as the heart's pacemaker, setting a pace and rhythm for heart contractions. Problems with the SA node can cause bradycardia, a slow heart rate, tachycardia, a rapid heartbeat, or a heartbeat with long pauses in between beats.
Bradycardia
Sick sinus syndrome (SSS) most often causes bradycardia, Medline Plus explains. Bradycardia is defined as a pulse rate less than 60 beats per minute (BPM), but the heart rate may need to fall to 40 to 50 BPM before symptoms are noticed, the Heart Rhythm Society states. Fainting, low blood pressure, weakness and dizziness are symptoms of bradycardia. Shortness of breath from lack of oxygen may occur, along with chest pain. A person with SSS may be confused from lack of oxygen to the brain. Pacemaker placement treats the symptoms by setting a steady pace for the heart.
Tachycardia
When the heart beats too quickly, people may complain that they feel like their heart is pounding in their chest, a symptoms known as palpitations. Tachycardia can also cause fainting, lightheadedness, dizziness and weakness, because the ventricles don't have time to fill up with blood between heart beats. Pacemakers and medications may be used to treat tachycardia in SSS.
Bradycardia-Tachycardia
In bradycardia-tachycardia syndrome, periods of rapid heartbeat alternate with periods of bradycardia. There may be a long pause between heartbeats, according to the Mayo Clinic. People with bradycardia-tachycardia are also at risk of developing blood clots in the heart that can travel to the brain and cause stroke. Blood thinners to decrease the chance of clot formation may be prescribed. Medications to slow tachycardic episodes may be prescribed.
