Sinus Node Dysfunction

The sinus node, the natural pacemaker of the heart, is located in the heart's upper chamber, called the atrium. It is responsible for initiating the electrical impulse that travels through the heart, causing it to beat in a regular rhythm and heart rate. This normal transmission is called normal sinus rhythm, with a regular heartbeat of 60 to 100 times per minute. If the sinus node is not functioning normally — due to damage from surgery, drugs, congenital heart defects or other causes — the heartbeat may become very slow with a decrease in blood pressure. Sinus node dysfunction may lead to an abnormally slow heart rhythm called bradycardia.

Sinus Node Dysfunction may cause the following symptoms:

  • Chest pressure or pain
  • Fainting, also known as syncope, or near-syncope
  • Fatigue
  • Lightheadedness or dizziness
  • Palpitations, which can be skipping, fluttering or pounding in the chest
  • Shortness of breath

It is important to note that children with sinus node dysfunction may not know how to describe what they are feeling. They may have trouble keeping up with other children or realize they are having "spells" and want to sit down and rest. Some children do not experience any symptoms at all.

Sinus node dysfunction may occur spontaneously with unpredictable timing. Therefore, in many cases, specialized tests are needed to make an accurate diagnosis. If your doctor suspects that your child has an arrhythmia caused by sinus node dysfunction, he or she will order one or more of the following diagnostic tests to determine the source of your child's symptoms.

  • Electrocardiogram (ECG or EKG) — An ECG records the heart's electrical activity. Small patches called electrodes are placed on your child's chest, arms and legs, and are connected by wires to the ECG machine. The electrical impulses of your child's heart are translated into a graph or chart, enabling doctors to determine the pattern of electrical current flow in the heart and to diagnose arrhythmias.
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Sinus node dysfunction can be treated with the implantation of a permanent pacemaker. A pacemaker is a medical device that regulates the heart beat. It consists of two parts — the generator and the lead. The generator is a small metal container with a battery and tiny computer. The lead is an insulated wire that carries electrical impulses to the heart to ensure a stable heartbeat.

The computer in the pacemaker is constantly monitoring your child's heartbeat. This is called sensing. When the pacemaker senses your child's heartbeat, it continues to "watch" or monitor your child's heart and does not send a signal to stimulate the heart to beat. If no electrical impulse is sensed by the pacemaker, it sends out a signal to stimulate your child's heart to beat.

For information on how a pacemaker is implanted, please see Pediatric Pacemaker Procedure.

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Reviewed by health care specialists at UCSF Benioff Children's Hospital.

Related Information

UCSF Clinics & Centers

Heart Center

Arrhythmia Center
1825 Fourth St., Sixth Floor
San Francisco, CA 94158
Phone: (415) 514-2783
Fax: (415) 353-4144
Appointment information

Pediatric Heart Center Clinic at Mission Bay
1825 Fourth St., Sixth Floor
San Francisco, CA 94158
Phone: (415) 353-2008
Fax: (415) 353-4144
Appointment information

Cardiac Intensive Care Unit
1975 Fourth St., Fourth Floor
San Francisco, CA 94158
Phone: (415) 353-1955
Fax: (415) 353-9144

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