sick sinus syndrome

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Sick Sinus Syndrome



Sick sinus syndrome is a disorder of the sinus node of the heart, which regulates heartbeat. With sick sinus syndrome, the sinus node fails to signal properly, resulting in changes in the heart rate.


The sinus node in the heart functions as the heart's pacemaker, or beat regulator. In sick sinus syndrome, patients normally will experience bradycardia, or slowed heart rate. Also, it is not uncommon to see fluctuations between slow and rapid heart rate (tachycardia). This makes the diagnosis and treatment of sick sinus syndrome more complicated than most other cardiac arrhythmias (irregular heart beats). A sick sinus node may be responsible for starting beats too slowly, pausing too long between initiation of heartbeats, or not producing heartbeats at all.

Causes and symptoms

Sick sinus syndrome may be brought on by the use of certain drugs, but is most common in elderly patients. Cardiac amyloidosis, a condition in which amyloid, a kind of protein, builds up in heart tissue, may affect the sinus node. Other conditions, such as sarcoidosis (round bumps in the tissue surrounding the heart and other organs), Chagas' disease (resulting from the bite of a bloodsucking insect) or certain cardiac myopathies can cause fiber-like tissue to grow around the normal sinus node, causing the node to malfunction.
A patient may not show any symptoms of sick sinus syndrome. In general, however, the common symptoms are those associated with slow heart rate, such as light-headedness, or dizziness, fatigue and fainting. Patients may also experience confusion, heart palpitations, angina or heart failure.


A slow pulse, especially one that is irregular, may be the first indication of sick sinus syndrome. Electrocardiography (ECGs) is a commonly used method of detecting sick sinus syndrome. ECG monitoring for 24 hours is most useful, since with this syndrome, heart rate may alternate between slow and fast, and the determination of this fact can help differentiate sick sinus syndrome from other arrhythmias.


If drugs are causing the problem, their withdrawal may effectively eliminate the disorder. However, the treatment of sick sinus syndrome is normally delayed until a patient shows symptoms. Once treatment is indicated, most patients will receive a pacemaker. This is a permanent treatment involving implantation of a small device under the skin below the collarbone. Small electrodes run from the device to the heart; they deliver and regulate the electrical signals that cause the heart to beat. Patients with sick sinus syndrome should generally receive dual chamber pacing systems to prevent atrial fibrillation (involuntary contraction of the muscles of the atria). Some drugs are used to treat sick sinus syndrome, but digitalis should be used with caution. Often the use of drugs to regulate the heartbeat should be implemented only after the pacemaker has been placed, since these drugs may further worsen the slow heart rate.

Key terms

Arrhythmia — Irregular heart beat.
Atria — Plural for atrium. The atria are the upper chambers of the heart.
Bradycardia — A heart rate slower than normal.
Electrocardiograph (ECG) — A test of a patient's heartbeat that involves placing leads, or detectors, on the patient's chest to record electrical impulses in the heart. This test will produce a strip, or picture record of the heart's electrical functioning.
Myopathy — Weakness of muscle.
Pacemaker — A device implanted under the skin, below the collarbone, to regulate heartbeat. Leads from the device to the heart stimulate the electrical functions of the heart. Pacemakers are often used to control bradycardia and are usually smaller than a silver dollar.

Alternative treatment

The reduction or elimination of certain foods and substances, such as alcohol or caffeine, may be advised to control heart rate. Stress reduction may also assist with changes in rate. Homeopathic treatment can work on a deep healing level, while acupuncture and botanical medicine can offer supportive treatment for symptoms.


Patients with sick sinus syndrome face relatively normal lives if the disorder is controlled by a pacemaker. However, in some patients, the pacemaker does not adequately control the fluctuations in heart rate. Left untreated, or in severe cases, the heart could stop beating.


Elimination of a drug therapy which aggravates sick sinus syndrome is the first line of treatment for some patients. Other causes of the syndrome are not preventable. However, proper treatment of those underlying conditions which affect the tissues of the heart may intervene to prevent sick sinus syndrome from becoming a significant problem.



American Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300.
National Heart, Lung and Blood Institute. P.O. Box 30105, Bethesda, MD 20824-0105. (301) 251-1222.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


not in good health; ill; afflicted with disease.
sick sinus syndrome a complex cardiac arrhythmia usually associated with syncope and manifested as severe sinus bradycardia alone, sinus bradycardia alternating with tachycardia (see bradycardia-tachycardia syndrome), or sinus bradycardia with atrioventricular block. It is a combination of sinoatrial node dysfunction and failure of an escape pacemaker.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

sick si·nus syn·drome

symptoms ranging from dizziness to unconsciousness due to chaotic or absent atrial activity often with bradycardia alternating with tachycardia, recurring ectopic beats including escape beats, runs of supraventricular and ventricular arrhythmias, sinus arrest, and sinoatrial block.

sick si·nus syn·drome

symptoms ranging from dizziness to unconsciousness due to chaotic or absent atrial activity often with bradycardia alternating with tachycardia, recurring ectopic beats including escape beats, runs of supraventricular and ventricular arrhythmias, sinus arrest, and sinoatrial block.
Farlex Partner Medical Dictionary © Farlex 2012

sick sinus syndrome

Bradycardia-tachycardia syndrome, sinus node dysfunction Cardiology A diffuse cardiac conduction system defect characterized by a pathologically slow or erratic rate of sinus depolarization due to impaired automaticity; SSS accounts for up to 50% of pacemaker implantations Intrinsic causes Scarring, degeneration, damage to conduction system–eg, aging, MI; ischemia; infiltrative disease–eg, amyloidosis, hemochromatosis, sarcoidosis; collagen vascular disease–SLE, RA, scleroderma; myotonic muscular dystrophy; heart surgery–valve replacement, transplantation; infections-Chagas' disease, endocarditis Extrinsic causes–autonomic syndromes–eg, carotid hypersensitivity, neurocardiac syncope, vagal stimulation; drugs–CCBs, beta-blockers, digoxin, clonidine, sympatholytics, antiarrhythmics; hypothyroidism; hypothermia; neurologic defects; ↑/↓ K+ Clinical Common in elderly; if severe, associated with vertigo, palpitations, exercise intolerance, syncope, cerebral dysfunction, persistent sinus bradycardia–30–60/min PLUS SVT, hence the trivial name, 'brady-tachy' syndrome Treatment Verapamil, diltiazem, pacemaker Prognosis Mortality at 1, 3, and 10 yr is 5%, 9%, 25% respectively; unaffected by pacemakers
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

sick si·nus syn·drome

(sik sīnŭs sindrōm)
Symptoms ranging from dizziness to unconsciousness due to chaotic or absent atrial activity often with bradycardia alternating with tachycardia, recurring ectopic beats including escape beats, runs of supraventricular and ventricular arrhythmias, sinus arrest, and sinuatrial block.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

sick sinus syndrome

Abnormal functioning of the natural pacemaker, the SINOATRIAL NODE of the heart. This causes episodes of slowing or speeding or even short periods of heart stoppage. An artificial pacemaker may be fitted.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
References in periodicals archive ?
(iii) Patients with sick sinus syndrome complicated by takotsubo cardiomyopathy may benefit from pacemaker implantation.
Occult accessory posteroseptal bypass tracts can become manifest in patients over 60 years of age, coinciding with the development of sick sinus syndrome, thus requiring a step-by-step therapeutic approach.
TABLE 1 Patient, anaesthetic, ECT and pacemaker details, and concomitant cardiac medications Patient Gender Age (y) Treatments Anaesthetic 1 F 86 26 thio/sux 2 M 81 12 thio/sux 3 M 72 8 thio/sux 4 F 78 12 thio/sux 5 F 72 12 thio/sux 21 prop/sux 6 F 83 17 thio/sux 7 F 89 16 thio/sux 8 F 87 6 thio/sux 9 F 87 8 prop/sux 10 M 80 9 thio/sux Patient Pacemaker Reason Medications 1 DDD tachy-brady syndrome amiodarone atenolol 2 DDDR sick sinus syndrome diltiazem 3 DDDR syncope none 4 DDDR heart block perindopril 5 DDDR bradycardia atenolol amlodipine 6 VVI sick sinus syndrome amiodarone digoxin 7 DDDR heart block metoprolol 8 DDDR sick sinus syndrome none 9 DDDR sick sinus syndrome frusemide 10 DDD heart block none thio/sux=tmopentone/suxametnomum.
Sick sinus syndrome (SSS) occurs when the sinoatrial (sinus) node, known as the "heart's pacemaker, " functions improperly and causes the heart to beat too rapidly (tachycardia), too slowly (bradycardia) or both (bradycardia-tachycardia syndrome).
Baroreflex sensitivity measured by the phenylephrine pressor test in patients with carotid sinus syndrome and sick sinus syndrome. Cardiovasc Res 1984;18:752-61.
A 62-year-old male with history of hypertension, coronary artery disease, and sick sinus syndrome presented to outpatient device check clinic to establish care for a pacemaker device.
Sick sinus syndrome is defined as an abnormality of the cardiac impulse formation that can either be of an intrinsic or extrinsic cause, leading to the impairment of its pace making function.
Therefore, we concluded that the patient also has concomitant sick sinus syndrome and we decided to implant a pacemaker.
The bradycardias reported have included sinus bradycardia, sinus arrest, nodal and junctional rhythms, sick sinus syndrome, and all degrees of atrioventricular block.[1,3,7,8,11,18-20] Our patient showed only sinus bradycardia and first-degree atrioventricular block.
Sick sinus syndrome is the collection of clinical conditions that result from an abnormality of the sinoatrial nodal automaticity.
A 33-year-old woman with a history of sick sinus syndrome underwent a dual chamber pacemaker implantation (Ela DR213 Talent, Ela 4068 for atrial, and BT46D for ventricular leads) seven years ago.