Sick Sinus Syndrome

(SSS; Bradycardia-Tachycardia Syndrome; Sinus Node Dysfunction)


Sick sinus syndrome is a group of symptoms due to faulty sinus node. The sinus node is a cluster of cells in the heart. These cells make the heart beat normally. When the sinus node does not work well, it can lead to:

  • Bradycardia—abnormally slow heartbeats
  • Tachycardia—abnormally fast heartbeats
  • Bradycardia-tachycardia—the heart switches between fast and slow beats
  • Missed or skipped beats

Sick sinus syndrome usually gets worse. Over time, it can lead to serious heart problems.

Anatomy of the Heart

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The sinus node sets the pace of the heart. It creates and sends signals that make the heart beat in a regular pattern. The sinus node's function may be disrupted by:

  • Problems within the heart tissue
  • Toxins, drugs, medicines, or trauma that affects heart tissue

Risk Factors

Sick sinus syndrome is fairly rare. It is more common in older people. Other things that may raise the risk are:

  • Family history of sinus node problems
  • Certain heart problems, such as:
  • Other conditions that can affect the heart such as:
  • Trauma to the heart from surgery
  • Certain medicines, such as:
    • Digoxin
    • Antiarrhythmics
    • Calcium channel blockers
    • Lithium
  • Vasovagal syncope


At first, sick sinus syndrome may not have symptoms, or the symptoms may come and go.

When symptoms happen, they may be:

  • Heart flutters
  • Fast, skipped, or pounding heartbeats
  • Feeling faint or fainting
  • Dizziness
  • Tiredness


Sick sinus syndrome is often not found unless there are symptoms. The doctor will ask about symptoms and past health. A physical exam will be done. To diagnose the condition, heart tests may be done, such as:

  • ECG—tests electrical activity of the heart
  • Holter monitoring—a device worn to measure heart activity over 24 to 48 hours
  • Electrophysiology study (EPS)—wires are passed into the heart to measure activity— used more often with severe problems


For those with no symptoms, treatment may not be needed. Over time, sick sinus syndrome can raise the risk of atrial fibrillation, heart failure, heart attack, or stroke. As a result, the doctor will need to monitor heart health.

Treatment may be needed if uneven heart patterns disrupt blood flow through the heart. Options may be:

  • Pacemaker —A device may be inserted to send signals to the heart. This will make the heart create a normal rhythm when needed. It is often used with slow heartbeats.
  • Medicine—May help to control fast heartbeats or speed up slow heartbeats.

Underlying conditions may also need to be treated.


There are no guidelines to prevent sick sinus syndrome.


American Heart Association

Heart Rhythm Society


Canadian Heart Rhythm Society

Heart and Stroke Foundation of Canada


De Ponti R, Marazzato J, et al. Sick sinus syndrome. Card Electrophysiol Clin. 2018;10(2):183-195.

Sick sinus syndrome. EBSCO DynaMed website. Available at: Accessed September 13, 2021.

Sick sinus syndrome. Heart Rhythm Society website. Available at: Accessed September 13, 2021.

Sinus node dysfunction. Merck Manual Professional Version website. Available at: Accessed September 13, 2021.

Last reviewed July 2021 by EBSCO Medical Review Board Nicole Meregian, PA  Last Updated: 9/13/2021