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Sick sinus syndrome
Definition:
A group of abnormal heartbeats (arrythmias) presumably caused by a malfunction of the sinus node, the heart's "natural" pacemaker.

Alternative Names:
Bradycardia-tachycardia syndrome

Causes, incidence, and risk factors:

Sick sinus syndrome is a relatively uncommon syndrome affecting approximately 3 out of 10,000 people. It can be manifested by many arrhythmias, including sinus arrest, sinus bradycardia (slow heart rate), sinus node exit block, and other similar bradycardias.

Tachycardias (fast heart rate) such as PSVT and atrial fibrillation/flutter may also be associated with sick sinus syndrome. Tachycardias of sick sinus syndrome are characterized by a long pause following the ending of the tachycardia.

Abnormal rhythms are often caused or worsened by medications such as digitalis, calcium channel blockers, beta-blockers, sympatholytic medications, and anti-arrhythmics. Disorders that cause scarring, degeneration, or damage to the conduction system can cause sick sinus syndrome, including sarcoidosis, amyloidosis, Chagas' disease, and cardiomyopathies.

Cardiac surgery, especially to the atria, is a common cause of sick sinus syndrome in children. Non-specific fibrotic (scar-like) degeneration of the conduction system (age-related) is often the cause.

Coronary artery disease, hypertension (high blood pressure), and aortic and mitral valve diseases may be associated with sick sinus syndrome, although this association may only be incidental.

Symptoms:
Note: Usually no symptoms are present.
Signs and tests:

The heart rate may be very slow at any time or after termination of an episode of tachycardia. The blood pressure may be normal or low. The symptoms are non-specific and may mimic other disorders.

The sick sinus syndrome may cause symptoms of heart failure to occur or worsen. The diagnosis of sick sinus syndrome includes a history of symptoms that occur only during arrhythmia episodes. However, this correlation often is difficult to prove.

An ECG shows various arrhythmias characteristic of sick sinus syndrome. Continuous ambulatory (Holter) monitoring may be needed to document the arrhythmia because of the episodic nature of the disorder. An EPS (intracardiac electrophysiology study) may confirm that the arrhythmia is caused by a disorder of the sinus node.

Response of the heart to exercise may demonstrate sick sinus syndrome.

Treatment:

If the disorder is asymptomatic (without symptoms), no treatment is necessary. Medications that worsen symptoms should be stopped.

A permanent implanted pacemaker may be necessary when it has been established that the symptoms are related to bradycardia (slow heart rate).

Associated tachycardia (a fast heart rate) may be treated with medications after the person is protected from symptomatic bradycardia by a pacemaker.

Expectations (prognosis):
This syndrome is slowly progressive. As long as the person remains asymptomatic, no treatment is necessary. There is an excellent long-term prognosis (probable outcome) with the permanent use of a pacemaker, when indicated.
Complications:
Calling your health care provider:
Call for an appointment with your health care provider if you experience light-headed spells, episodes of passing out, palpitations, or other symptoms.
Prevention:
Treatment of related disorders may be helpful. Many times, the condition is not preventable.
Review Date: 2/5/2001
Reviewed By: Elena Sgarbossa, M.D., Department of Cardiology, Rush-Presbyterian St. Luke’s Medical Ctr., Chicago, IL. Review provided by VeriMed Healthcare Network.
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