An irregularity in the heart's natural rhythm is called an arrhythmia. Approximately 4 million Americans have recurrent arrhythmias that require medical treatment. The electrical signal that initiates the heartbeat begins in the sinoatrial (SA) node, which is located in the right atrium. The SA node is sometimes called the heart's "natural pacemaker." When an electrical impulse is released from the SA node, it causes the atria to contract.
Sick sinus syndrome is a relatively uncommon arrhythmia that originates in the atria. Its signs and symptoms indicate that the SA node is not working properly. The SA node usually sends electrical impulses at a certain rate; if it is not working properly, the heart may beat too fast, too slow, or both. The rate can also change back and forth from fast to slow.
What Causes Sick Sinus Syndrome?
Sick sinus syndrome often develops slowly over many years. The cause is usually unknown, but disorders that cause scarring, degeneration, or damage to the conduction system of the heart can cause sick sinus syndrome. It occurs more often in people over 50, but children may develop the condition after having open heart surgery.
Many people with sick sinus syndrome do not have symptoms, or they do not think their symptoms are serious enough for them to see a doctor. These symptoms include:
• Dizziness or lightheadedness
• Confusion that comes and goes
• Heart palpitations (the feeling that the heart has skipped a beat)
• Chest pain or angina
• Shortness of breath
• Muscle aches
When sick sinus syndrome is suspected, a complete medical history and physical examination are performed. Additional tests may be ordered to confirm the diagnosis, including a standard electrocardiogram (ECG), Holter monitoring, event monitoring, and electrophysiology studies (EPS).
The treatment for sick sinus syndrome depends on the symptoms. It may include avoiding food, drinks, and medicines that exacerbate the symptoms. Antiarrhythmic medicines may be prescribed, and pacemaker implantation may be needed in some cases.
Texas Heart Institute www.texasheartinstitute.com/HIC/Topics/Cond/sicksinus.cfm
American Heart Association www.americanheart.org/presenter.jhtml?identifier=10
Medline Plus www.nlm.nih.gov/medlineplus/ency/article/000161.htm
Updated December 2009