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Sinus Node Dysfunction

The sinus node (SA node) consists of a group of specialized cells within the right atrium and is the heart's natural pacemaker. Normally, the heart's electrical impulse starts in the SA node. This important structure allows the heart rate to increase or decrease in response to the body's activity level. Sinus node dysfunction (SND) can occur in patients with congenital heart disease (CHD), especially those who have had cardiac surgery which results in scarring within the right atrium.

Signs and Symptoms

Symptoms associated with SND vary from no symptoms to:

  • Fatigue
  • Bradycardia (slow heart rate)
  • Dizziness or lightheadedness
  • Syncope (fainting or passing out)
  • Shortness of breath at rest or with exercise
  • Palpitations or irregular heart beat


The diagnosis of SND is made based on specific findings noted on your electrocardiogram (ECG). Specifically, your healthcare team will look at the rate and regularity of the electrical impulse that comes from the SA node.

After a diagnosis of SND has been made, your healthcare team may order additional testing.  This may include a long-term monitor such as a Holter monitor to determine the frequency and severity of the heart block.  Holters or other long-term monitors may be worn again for routine rhythm monitoring, or if there is a concern about worsening symptoms.

Another common test after the diagnosis sinus node dysfunction is an exercise stress test.


Patients with significant symptoms often require and benefit from pacemaker implantation to increase their heart rate and have appropriate heart rate response to activity.

Lifestyle Changes:

Patients with SND are usually not restricted from sports or other activities, but they may experience fatigue or inability to perform activities at the same level as other people their age. If a pacemaker is required to treat the SND, then patients may have some lifestyle restrictions, depending on the type and location of the pacemaker.