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

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by Maria Borowski, MA

Definition

Sick sinus syndrome (SSS) is not a specific disease, rather the term is used to describe several heart rhythm disorders. These disorders include bradycardia (abnormally slow heart rate), tachycardia (abnormally fast heart rate), and a combination of the two in which the heart alternates between too fast and too slow, called bradycardia-tachycardia. With sick sinus syndrome, the irregular heartbeat is caused by a problem with the electrical signals of the heart. The problem originates in an area of the heart called the sinoatrial node. Considered to be the heart’s natural pacemaker, when the sinoatrial node is defective, the heart’s rhythms become abnormal.

Whether the heart beats too fast or too slow, or a combination, this disorder can be treated very effectively. If you think you may have this condition, you should contact your doctor to discuss treatment.

Causes

The normal rhythm of the heart is controlled by electrical signals. These signals begin the heart beat and control the speed and cycle of the heart’s rhythm. Sick sinus syndrome results from a breakdown in these electrical signals. The dysfunction originates in the sinus node (or sinoartrial node), which is the part of the heart that initiates these signals. This dysfunction can be due to:

• Intrinsic causes (problems within the heart tissue), such as degeneration of the sinus node, long-term illness, or even surgical injury
• Extrinsic causes (outside factors acting on the heart tissue), such as exposure to toxins or certain pharmacological agents

Risk Factors

Sick sinus syndrome is fairly rare, and mostly occurs in elderly people and those who have had damage to the cardiac tissue. Both men and women seem to be affected equally. The one exception is for infants and children, who very rarely may be found to have sick sinus disorder due to congenital abnormalities in their heart. Some of the risk factors for sick sinus syndrome include:

• Age 50 and older, and especially age 65 and older
• Some medications may worsen symptoms:
• Calcium channel blockers
• Beta-blockers
• Antiarrhythmics
• Digitalis

Symptoms

Often, patients with sick sinus syndrome experience no symptoms at all. Some patients do experience cardiac symptoms, like a period of very rapid heart beats followed by very slow heart rate. However, many of the symptoms of sick sinus disorder are mild and nonspecific. Some symptoms associated with sick sinus syndrome include:

• Heart palpitations
• Chest pain
• Fainting or dizziness
• Confusion or light-headedness
• Facial flushing
• Fatigue

These symptoms may be caused by other, less serious health conditions. If you experience any one of them, see your physician.

Diagnosis

Sick sinus disorder may go undetected for some time because the symptoms of this disorder are similar to the symptoms for many disorders. However, your doctor can perform tests that will help to give a more definitive diagnosis. Most likely, your doctor will ask about your symptoms and medical history, and perform a physical exam. Some additionally tests may include the following::

• Electrocardiogram (ECG)—measures the electrical activity of the heart and can detect abnormal heart rhythms
• Holter monitoring—continuous monitoring to observe episodes of tachycardia and bradycardia over an extended period of time
• Electrophysiology study (EPS)—invasive test where electrical wires are placed into the heart through a small puncture in the veins in the groin. The conduction system of the heart is then evaluated.

Treatment

For people with no symptoms, treatment may not be necessary. However, sick sinus syndrome is a progressive disorder. Sick sinus syndrome can further weaken the muscles of the heart in people with previous cardiac damage and can eventually cause heart failure. For this reason, people with symptoms are treated. Most treatment plans involve separate therapies for bradycardia and tachycardia. Talk with your doctor about the best treatment plan for you.

Treatment options include the following:

Surgery

For people with symptoms of sick sinus disorder, the implantation of a permanent pacemaker provides very effective therapy of the bradycardia or slow heart rates. Electrodes from the pacemaker are placed in the right atrium, or upper chamber of the heart and the right ventricle. The pacemaker is a battery-powered implantable generator that sends signals to the electrodes to stimulate the heart to contract rhythmically and effectively. People with implanted pacemakers have a very good prognosis.

Medication

Medications that control tachycardia are also a treatment option. But in most cases, people who receive medication have already undergone implantation of a pacemaker.

Prevention

Unfortunately, for most people, sick sinus syndrome is not preventable, as it is caused by prior damage or scarring to the heart tissue. However, some strategies for minimizing your chances of developing this condition include:

Making sure that you receive treatment for any cardiac disorders you might have
Ensuring that any doctor you see is aware of your cardiac conditions, as some medications should be avoided with this condition

RESOURCES:
American Heart Organization
http://www.americanheart.org

Heart Rhythm Society
http://www.hrspatients.org

CANADIAN RESOURCES:
Canadian Cardiovascular Society
http://www.ccs.ca/home/index_e.aspx

Heart and Stroke Foundation of Canada
http://ww2.heartandstroke.ca/Page.asp?Pa...

REFERENCES:

Adan V, Crown LA. Diagnosis and treatment of sick sinus syndrome. Am Fam Physician. 2003: 67 (8):1725-1738.

Medline medical dictionary: sick sinus syndrome. Available at: http://nlm.nih.gov.medlineplus/ency/arti.... Accessed July 28, 2005.

Sick sinus syndrome. Heart Rhythm Society website. Available at: http://www.hrspati.... Accessed July 28, 2005.

Sick sinus syndrome. The Merck Manual of Diagnosis and Therapy ; Sec. 16, Ch. 205, Arrhythmias. Available at: http://www.merck.c.... Accessed July 28, 2005.

Last reviewed February 2007 by Craig Clark, DO, FACC, FAHA, FASE

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