Sick sinus syndrome

Overview

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

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).

Symptoms

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, such as:

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

Types

  • 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.

Diagnosis

  • 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.

Treatment

Asymptomatic SSS may not require treatment. Your doctor will review any medications you take regularly to ensure that they don’t negatively affect your condition. If you display bradycardia symptoms, a permanent implanted pacemaker may be necessary. Sometimes, medicine to control fast heart rate are used with a pacemaker to prevent slow heart rate. Tachycardia may be treated with medicine or, occasionally, radiofrequency ablation.

 

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