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Sick Sinus Syndrome Overview
Sick sinus syndrome also known as sinus node disease or sinus node dysfunction is the name for a group of heart rhythm problems (arrhythmias) in which the sinus node the heart’s natural pacemaker doesn’t work properly.
The sinus node is an area of specialized cells in the upper right chamber of the heart that controls the rhythm of your heart. Normally, the sinus node produces a steady pace of regular electrical impulses. In sick sinus syndrome, these signals are abnormally paced.
A person with sick sinus syndrome may have heart rhythms that are too fast, too slow, punctuated by long pauses or an alternating combination of all of these rhythm problems. Sick sinus syndrome is relatively uncommon, but the risk of developing sick sinus syndrome increases with age.
Many people with sick sinus syndrome eventually need a pacemaker to keep the heart in a regular rhythm.
Various irregular heart rates (arrhythmias) or combinations of arrhythmias can occur in this condition. People with this syndrome can have slow arrhythmias or a combination of fast and slow arrhythmias. These include:
- Periods of time when the sinus node does not fire at all (sinus pauses) and other areas of the heart take over and cause the heart to beat.
- Prolonged periods of time when the heart rate is spontaneously very slow and does not increase as it should with activity (persistent sinus bradycardia).
- Periods of fast arrhythmias (supraventricular tachycardias), especially atrial fibrillation or atrial flutter, alternating with periods of very slow heart rates (“tachy-brady” syndrome).
Treatment of sick sinus syndrome depends on the type of rhythm problem. Treatment typically is a pacemaker, and sometimes medicines is used too.
Types of Sick Sinus Syndrome
Sick sinus syndrome is only a general term for multiple disorders that occur when the sinus node does not work properly. The resulting heart beat or rhythm will be different depending on the specific electrical activity at the sinus node.
The multiple disorders that characterize SSS include:
- sinus bradycardia (the heart beats very slowly)
- sinus arrest (the sinus node temporarily stops working or pauses, causing a change in the heart’s beating)
- sinoatrial block (the sinus node impulse is blocked from reaching the atria- the two upper chambers of the heart)
- bradycardia-tachycardia syndrome (the heart alternates between a very slow and very fast beat)
Sick Sinus Syndrome Symptoms
Most people with sick sinus syndrome initially have few or no symptoms. In some cases, symptoms may come and go.
When they do occur, sick sinus syndrome symptoms may include:
- Slower than normal pulse (bradycardia)
- Dizziness or lightheadedness
- Fainting or near fainting
- Shortness of breath
- Chest pains
- A sensation of rapid, fluttering heartbeats (palpitations)
Many of these signs and symptoms are caused by reduced blood flow to the brain when the heart beats too fast or too slowly.
Risk Factors for Sick Sinus Syndrome
The risk of developing sick sinus syndrome increases with age. Having SSS at birth is called congenital sick sinus syndrome. Congenital heart conditions are the main cause of SSS in young children and adults.
Risk factors for SSS include:
- repaired congenital heart disease (even with repairs, the heart is still weak)
- congenital heart disease (a person is born with heart defects)
- coronary artery disease (the coronary artery becomes clogged, and blood flow to the heart is restricted)
Sick Sinus Syndrome Causes
Your heart is made up of four chambers two upper chambers (atria) and two lower chambers (ventricles). The rhythm of your heart is normally controlled by the sinoatrial (SA) node or sinus node an area of specialized cells located in the right atrium.
This natural pacemaker produces the electrical impulses that trigger each heartbeat. From the sinus node, electrical impulses travel across the atria to the ventricles, causing them to contract and pump blood out to your lungs and body.
If you have sick sinus syndrome, your sinus node isn’t functioning properly, so your heart rate may be too slow (bradycardia) or too fast (tachycardia) or irregular.
Types of sick sinus syndrome and their causes include:
- Sinoatrial block. Electrical signals move too slowly through the sinus node, causing an abnormally slow heart rate.
- Sinus arrest. The sinus node activity pauses.
- Bradycardia-tachycardia syndrome. The heart rate alternates between abnormally fast and slow rhythms, usually with a long pause (asystole) between heartbeats.
Treatment of Sick Sinus Syndrome
Treatment for mild or early cases of SSS involves relieving symptoms. Doctors may adjust or change your medication if that is the problem. They may also prescribe additional medications that may have a direct effect on the heart rhythm. Eventually, however, most individuals with SSS will need an artificial pacemaker implant when the sinus node is no longer able to adequately perform.
A pacemaker is a very small machine that is surgically implanted in the chest or abdomen to regulate your heartbeat. It does this through sending electrical pulses to the heart.
Almost one-half of pacemaker implantations are performed because of problems related to sick sinus syndrome (Herrmann, Fabritz, Layh, Kirchhof, & Ludwig, 2011). Pacemakers are generally tolerated well, and patients experience few complications.
Rare complications of a pacemaker implant include:
- myocardial perforation (accidental hole made in the heart during surgery)
- infection from the implant (bacteria brought in during surgery causes infection)
- venous thrombosis (blood clot within the body’s veins)
- collapsed lung
With modern technology, there is a growing interest in creating a biological pacemaker. This could be done by taking cells containing pace-making genes and implanting them in the heart. The cells would then grow into the heart and become a new pacemaker.
A second approach would be to use stem cells. Stem cells are immature cells capable of developing into any specific type of mature cell. The cells could potentially grow into the same type of heart tissue as the sinus node.