What is Sick Sinus Syndrome?
Sick sinus syndrome (SSS) is a relatively uncommon heart rhythm disorder. It is also
known as "sinus node dysfunction". Sick sinus syndrome is not a specific rhythm, rather
it's an umbrella term for a group of abnormal rhythms that are caused by a malfunction
of the sinoatrial node (SA node). Sick sinus syndrome is not a specific disease, but
rather a group of signs or symptoms that indicate the sinus node is not functioning
properly. A person with Sick sinus syndrome may have a heart rhythm that is too slow
(bradycardia), too fast (tachycardia), or one that alternates between the fast and slow
(Bradycardia-tachycardia syndrome). Bradycardia-tachycardia syndrome is a variant of
sick sinus syndrome in which slow and fast arrhythmias alternate, and is often associated
with ischemic heart disease and heart valve lesions. Typically, the rhythm appears erratic
and irregular (see below). Sick sinus syndrome may be due to defects in the heart itself,
or it can be related to factors outside the heart. Sick sinus is most often found in older
adults above the age of 50.
Symptoms of Sick Sinus Syndrome
Most people with sick sinus syndrome have few or no symptoms.
In other people, symptoms may come and go. These symptoms can include:
- Slower than normal pulse (bradycardia)
- Fainting (syncope)
- Feeling tired all the time
- Weakness or fatigue
- Shortness of breath (dyspnea)
- Chest pain (angina)
- Disturbed sleep
- Confusion
- Heart palpitations
Diagnosis
EKG/ telemetry monitoring may be necessary because arrhythmias are transient.
The ECG may show any of the following:
- Sinus Bradycardia
- Sinus arrest
- Sinoatrial block
- Atrial Fibrillation with slow ventricular response
- A prolonged period of asystole following periods of tachycardia
- Atrial flutter
- Ectopic atrial tachycardia or multifocal atrial tachycardia
- Sinus node reentrant tachycardia
- Wolf-Parkinson-White syndrome
Risk Factors for Sick Sinus Syndrome
While the exact cause of SSS is unknown, some factors
often are associated with a condition, such as:
- Age +50
- Previous heart attack (myocardial infarction)
- Medications to treat High Blood Pressure and other heart diseases
- Hyperkalemia (too much potassium in the blood)
- Thyroid disease
- Sleep apnea
- Heart surgery
Treatment and causes
- Pacemakers are the most used treatment of sick sinus syndrome.
- Bradycardia arrhythmias are well controlled with pacemakers, while tachycardia arrhythmias
respond well to medical therapy.
- When both bradycardia and tachycardia are present, drugs to control tachycardia may exacerbate
the bradycardia arrhythmia. Therefore, a pacemaker is implanted before drug therapy is utilized.
- Abnormal rhythms are often caused or worsened by medications such as digitalis, calcium channels,
beta-blockers, sympatholytic medications.
- Disorders that cause scarring, degeneration, or damage to the conduction system can cause Sick
sinus syndrome, including sarcoidosis, amyloidosis, hemochromatosis, Chagas' disease, cardiomyopathies,
and scar-like degeneration of the cardiac conduction system.
- Cardiac surgery, especially to the atria, is a common cause of sick sinus syndrome in children.
- Coronary artery disease, high blood pressure, aortic and mitral valve diseases may be associated
with sick sinus syndrome.
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