Sinus node dysfunction

Sinus node dysfunction (SND), also known as sick sinus syndrome (SSS), is a group of heart rhythm problems (arrhythmias) in which the heart's natural pacemaker (sinus node) doesn't work properly. The sinus node is an area of specialized cells in the upper right chamber of the heart that controls the rhythm of your heart. Normally, the sinus node produces a steady pace of regular electrical impulses. In sick sinus syndrome, these signals are abnormally paced.

A person with sinus node dysfunction may have heart rhythms that are too fast, too slow, punctuated by long pauses — or an alternating combination of all of these rhythm problems. Sinus node dysfunction is relatively uncommon, but the risk of developing it increases with age. Many people with sinus node dysfunction eventually need a pacemaker to keep the heart in a regular rhythm.

Symptoms

Sinus node dysfunction often doesn't cause noticeable symptoms. When symptoms do occur, they may mimic those caused by other health problems, making the condition difficult to diagnose. Symptoms may include:

• Fatigue
• Dizziness
• Lightheadedness
• Fainting or near fainting
• Shortness of breath
• Chest pains
• Trouble sleeping or staying asleep
• Confusion or difficulty remembering things

Causes

Sinus node dysfunction is associated with damage to or degeneration of the sinus node — often the result of underlying conditions or medical treatments. Conditions that can cause or contribute to problems with the sinus node include:

• Aging
• Heart disease
• Medications, including some drugs for heart rhythm disorders, high blood pressure and psychiatric problems
• Sleep apnea
• Hyperkalemia (high potassium levels)
• Previous heart surgery near the sinus node

Treatment

Treatment for sinus node dysfunction usually involves addressing underlying health problems and reducing symptoms. If symptoms are severe or the condition is causing more serious heart rhythm problems, treatment may involve medications to control the heart rate or the implantation of a pacemaker.

See also

• Arrhythmia
• Bradycardia
• Tachycardia
• Pacemaker