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Sick sinus syndrome


Definition:

Sick sinus syndrome is a group heart rhythm disorders that include:

  • Sinus bradycardia: This occurs when the natural pacemaker of the heart does not send out a signal telling the heart to beat often enough. The heart beat rate is slow.
  • Sinus pauses or arrest: This occurs when the natural pacemaker of the heart stops sending out signals telling to heart to beat for periods of time.

People with these disorders may also have other abnormal heart rhythms, such as:

  • Supraventricular tachycardia: This is a fast heart rate that starts in the upper chambers of the heart (atria).
  • Bradycardia-tachycardia: This is a pattern of alternating slow and fast heart rhythms (sometimes called "tachy-brady syndrome").
Alternative Names:

Bradycardia-tachycardia syndrome; Sinus node dysfunction

Causes:

Sick sinus syndrome most often occurs in people older than 50. It is often due to scar-like damage to electrical pathways in the heart muscle tissue.

In children, heart surgery on the upper chambers is a common cause of sick sinus syndrome.

Coronary artery disease, high blood pressure, and aortic and mitral valve diseases may occur with sick sinus syndrome, although these diseases may have nothing to do with the syndrome.

Sick sinus syndrome is uncommon. Sinus bradycardia occurs more often than the other types of the condition.

Tachycardias that start in the upper chambers of the heart may be part of the syndrome. These include atrial fibrillation, atrial flutter, atrial tachycardia, and other types of fast heart rates. A period of fast heart rates is often followed by very slow heart rates immediately after the tachycardia ends.

Some medicines can make abnormal heart rhythms worse. These include digitalis, calcium channel blockers, beta-blockers, and anti-arrhythmics.

Exams and Tests:

The heart rate may be very slow at any time. Blood pressure may be normal or low.

Sick sinus syndrome may cause symptoms of heart failure to start or get worse. Sick sinus syndrome is diagnosed when the symptoms occur only during episodes of arrhythmia. However, this is often hard to prove.

An ECG may show abnormal heart rhythms related to this syndrome.

Holter monitoring is an effective tool for diagnosing sick sinus syndrome. It may pick up very slow heart rates and long pauses, along with episodes of atrial tachycardias. Other forms of long-term electrical monitoring may also be useful.

An intracardiac electrophysiology study (EPS) is a very specific test for this disorder. However, it is not often needed and may not confirm the diagnosis.

Exercise testing has not been shown to work well to detect the problem.

Outlook (Prognosis):

The syndrome is progressive, which means it usually gets worse over time.

The long-term outlook is excellent for people who have a permanent pacemaker implanted.

Possible Complications:

  • Angina
  • Decreased exercise capacity
  • Fainting (syncope)
  • Falls or injury caused by fainting
  • Heart failure
  • Poor heart pumping
When to Contact a Medical Professional:

Call your health care provider if you have:

  • Light-headedness
  • Fainting
  • Palpitations
  • Other symptoms of the condition
Prevention:

Keeping your heart healthy by eating a well-balanced diet and exercising can prevent many types of heart disease.

You may need to avoid some types of medicines. Many times, the condition is not preventable.

References:

Olgin JE, Zipes DP. In: Specific arrhythmias: diagnosis and treatment. In: Bonow RO, Mann DL, Zipes DP, Libby P, Braunwald E, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 9th ed. St. Louis, MO: WB Saunders; 2011:chap. 39.

Zimetbaum P. Cardiac arrhythmias with supraventricular origin. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 64.


Review Date: 5/13/2014
Reviewed By: Michael A. Chen, MD, PhD, Associate Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 2002 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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