Sick Sinus Syndrome
Sick sinus syndrome (SSS) is a set of symptoms caused by abnormal electrical activity in a part of the heart called the sinus node.
What is going on in the body?
A collection of nerves in the heart form the heart's electrical system. This system is what keeps the heart beating. A part of this system, called the sinus node, usually generates the signal that causes the heart to beat.
When the sinus node is damaged or doesn't function correctly, the heart may beat too slowly or even stop beating for a period of time. Irregular heartbeats, called arrhythmias, can also occur. Sick sinus syndrome refers to the symptoms seen when the sinus node fails to work properly.
What are the causes and risks of the condition?
In most cases, no cause can be found for sick sinus syndrome. SSS is usually seen in middle-aged and elderly people. Possible causes of sick sinus syndrome include:
- blockages in the heart arteries caused by coronary artery disease
- high blood pressure
- almost any condition affecting the heart
- medications, such as beta blockers (atenolol, metoprolol, propranolol, carvedilol), and certain calcium channel blockers (diltiazem or verapamil). These medications may "bring out" or worsen this condition in a person who before had few or no symptoms.
What can be done to prevent the condition?
Most cases of sick sinus syndrome cannot be prevented. Careful selection of blood pressure and heart medications may avoid symptoms. Treatment of heart disease may help prevent the development of this syndrome in some cases.
How is the condition diagnosed?
Diagnosis of sick sinus syndrome begins with a history and physical exam. A heart tracing, called an electrocardiogram (ECG), can confirm the diagnosis. This test records the electrical activity in the heart, which is abnormal when symptoms occur.
Because symptoms come and go, a Holter monitor is often used to track the electrical activity of the heart over a longer period of time. This monitor can be worn for 24 hours or more, so that a heart tracing can be obtained during symptoms. If the abnormal electrical activity of sick sinus syndrome is seen on the heart tracing when symptoms occur, the diagnosis can be made.
Newer adaptations of this technology may also be used. These include an "event monitor", which may be worn for several weeks. When the patient has symptoms, he or she pushes a button on the device and it records the electrical activity of the heart at that very moment. This device allows the patient to "playback" the signal over a telephone and the recording center can convert this signal to an ECG tracing. This will then be sent to the cardiologist for review.
Technology is now available to implant a monitor under the patient's skin and record every beat for as long as six months. The electrophysiologist (a cardiologist who specializes in heart rhythms) can capture data from this implanted monitor with a special device that is placed on top of the patient's chest. This device may reveal subtle events that other methods miss.
Long Term Effects
What are the long-term effects of the condition?
A person with sick sinus syndrome can injure himself or herself during a fainting episode. An individual with certain arrhythmias has an increased risk of blood clots, which can cause a stroke.
Rarely, a person dies suddenly because the heart stops beating for a long period of time. Treatment can avoid most of these long-term effects if the diagnosis is made in time.
What are the risks to others?
Sick sinus syndrome is not contagious and poses no risks to others. Those who pass out may injure others if they are driving or performing other potentially dangerous activities.
What are the treatments for the condition?
If a person with sick sinus syndrome is having significant symptoms, a permanent device to help control the heartbeat is often used. This device is called a pacemaker. This device causes the heart to beat by creating tiny bursts of electricity that are sent to the heart. It only "fires" when it is needed, but can be lifesaving.
What are the side effects of the treatments?
The device can occasionally misfire and cause heartbeat problems. The pacemaker or the pacemaker wires may rarely become infected and the entire device will need to be replaced by a temporary pacemaker until the infection is cured. At that point a new pacemaker (essentially a battery, a computer chip, and wiring) will be inserted.
What happens after treatment for the condition?
Most people do very well after they receive a pacemaker. The pacemaker helps prevent dangerous symptoms, such as dizziness and fainting. Someone with other heart disease or arrhythmias usually needs lifelong treatment for these conditions.
How is the condition monitored?
The healthcare provider will recommend regular visits to monitor symptoms and treat any heart disease. Pacemakers need to be checked periodically to make sure they are working properly. Pacemakers also have a battery that needs to be replaced from time to time. Other medications may also need monitoring, sometimes with blood tests. Any new or worsening symptoms should be reported to the healthcare provider.
Cardiac Arrhythmias An integrated approach for the clinician, Prystowsky, E and Klein, G, 1994
Merck Manual, 1999
Current Medical Diagnosis and Treatment, 1996