What is Sick Sinus?

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  • Written By: wiseGEEK Writer
  • Edited By: O. Wallace
  • Last Modified Date: 03 October 2019
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Sick Sinus syndrome is a failure of the heartbeat to remain in rhythm. This can create tachycardia, periods of heartbeats that are too quick, or bradycardia, periods where the heartbeat is too slow. There can also be a mix of bradycardia and tachycardia, which is the most dangerous type. In most cases, sick sinus occurs in people over 50, though it can affect people of any age who have undergone heart surgery.

The most common form of sick sinus is bradycardia. The normal heart tends to naturally regulate itself, sending electrical signals along the sinus node in the heart to essentially tell the heart to beat. Dysfunction of this natural pacemaker can lead to improper electrical signals. This may be caused by scar tissue, or gradual degeneration of the sinus node. It is particularly common in children with heart defects who have undergone corrective heart surgery in the upper chambers of the heart. Such surgery can damage the little understood sinus node, and cause immediate sick sinus bradycardia, or bradycardia several years after surgery.

Surgery may also cause sick sinus tachycardia, yet it may also result from damage to the heart through heart medications like beta-blockers or digitalis. Anti-arrhythmia medications may for a short time fix the problem, but they are likely to further damage the heart. Sudden arrhythmias, as caused by tachycardia can cause sudden death as well.


Sick sinus bradycardia may progress more slowly, and at first be completely asymptomatic. As the illness begins to progress, however, it can lead to episodes of fainting, and eventually heart failure. If sick sinus bradycardia is observed, but does not seem to be affecting the patient much, then physicians tend to adopt a wait and see approach.

When sick sinus bradycardia begins to be of significant impact to the patient’s life, a pacemaker is usually implanted to keep the heart beating in normal sinus rhythm. Pacemaker implantation has a high rate of success in treating sick sinus bradycardia, however, in very young children, the pacemaker must be placed in the abdomen, and must be replaced in the shoulder when the child is older.

Symptoms of sick sinus of any type can include fainting, dizziness, a feeling of confusion, angina, shortness of breath, or general fatigue. While sick sinus bradycardia tends to be easy to detect with an EKG, or electrocardiogram, tachycardia may be harder to catch, since tachycardia occurs in events, rather than continuously.

Some cardiologists use a holter monitor, which is like a portable EKG that records all rhythms of the heart for 24 hours. If this fails to catch a tachycardia episode, an event monitor may be worn for several days. If the patient experiences symptoms, he or she presses a button to record the event. Event monitors are more likely to catch an episode of sick sinus tachycardia, yet still may fail to do so. In these cases, the patient will continue to be followed, and may still be scheduled for radiofrequent ablation.

Radiofrequent ablation is done by catheter. The sinus node is carefully tested for areas that seem to be causing arrhythmias, and areas of scar tissue or areas that seem to be responsible for abnormal rhythms are then subjected to high frequency radio waves which essentially kill these areas. This procedure has a good rate of success but patients may still need a defibrillator if there is doubt as to the total effectiveness of the procedure.

Untreated, sick sinus will invariably cause death, though there may be a slow progression from emergence of symptoms to actual failure of the heart. Those being treated for any form of sick sinus need to be careful about what kinds of medications they take. Even some over the counter medications can cause abnormal heartbeats. Children with sick sinus should never be treated with Ritalin or other ADD medications, as these are amphetamines that can severely exacerbate the problem.


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