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What is sick sinus syndrome?

Sick sinus syndrome (SSS) is not a specific disease, but rather a group of signs or symptoms that indicate the sinoatrial node (the heart’s natural pacemaker) is not functioning properly. Some diseases such as coronary artery disease, high blood pressure and aortic and mitral valve diseases may occur along with it, but are not part of the syndrome.

SSS can be caused by damage to electrical pathways in the heart muscle tissue. In children, a common cause is heart surgery on the atria (upper chambers).


  • Bradycardia – The heart’s natural pacemaker does not send a signal telling the heart to beat often enough, therefore the heartbeat rate is slow. Sinus bradycardia occurs more often than other types of SSS.
  • Supraventricular tachycardia – A fast heart rate originates in the upper chambers of the heart (atria), including atrial fibrillation, atrial flutter, atrial tachycardia and other types of fast heart rates. Fast heart rates often are followed by very slow heart rates.
  • Bradycardia-tachycardia – When the heart rhythm alternates between slow and fast (sometimes called “tachy-brady syndrome”).
  • Sinus pauses or arrest – The heart’s natural pacemaker stops sending signals telling the heart to beat for periods of time.

SSS most often occurs in people older than 50. Digitalis, calcium channel blockers, beta-blockers and anti-arrhythmic medicines can make abnormal heart rhythms worse.


Usually, SSS is asymptomatic (it has no symptoms). Some patients with SSS may have normal or low blood pressure, rapid or slow heartbeats, or a heartbeat that alternates between too fast and too slow. Symptoms that do occur often are similar to those of other diseases, such as heart failure. Those symptoms include:

  • Angina (chest pain)
  • Confusion
  • Fainting or near-fainting
  • Fatigue
  • Dizziness or lightheadedness
  • Heart palpitations
  • Shortness of breath
  • Abnormal heart rhythms


  • An electrocardiogram (ECG) may show abnormal heart rhythms related to this syndrome. SSS often is diagnosed only during arrhythmia.
  • Holter monitoring detects very slow heart rates and long pauses, as well as atrial tachycardia. Other types of long-term electrical monitoring also are used as a diagnostic tool.
  • An intracardiac electrophysiology study (EPS) can test for this disease, but is not often necessary and still may not confirm the diagnosis.
  • Exercise testing has not been shown to work well to detect the problem.