Abnormal function of the sinoatrial node, the heart’s natural pacemaker
- Most common in elderly people
- Smoking, a high-fat diet, lack of exercise, and excess weight are risk factors
- Gender and genetics are not significant factors
In sick sinus syndrome, the sinoatrial node, the heart’s natural pacemaker, becomes faulty, causing the heart to beat too slowly or miss a few beats. Often, the heart rate alternates between runs of slow and fast beats. Sick sinus syndrome is caused by the degeneration of cells in the sinoatrial node and is most common in elderly people. Often, the underlying cause is coronary artery disease. Sick sinus syndrome may also be due to heart muscle disease (see Dilated cardiomyopathy). Typically, it is a progressive condition with episodes becoming more frequent and prolonged over time.
What are the symptoms?
Symptoms have a sudden onset and are intermittent. They may include:
Palpitations (awareness of an irregular, abnormally rapid, or heavy heartbeat).
Brief attacks of light-headedness.
Loss of consciousness.
Shortness of breath.
Many of the symptoms are caused by decreased oxygen levels to the brain due to the reduced efficiency of the heart.
What might be done?
If your doctor suspects sick sinus syndrome, he or she will probably arrange for you to have electrocardiography (see ECG). Since symptoms are intermittent, you may need to have your heartbeat monitored for 24 hours or more while you carry out your everyday activities (see Ambulatory ECG). Your doctor may also recommend that you have further tests, such as echocardiography, to look for signs of cardiomyopathy.
Treatment of sick sinus syndrome usually involves inserting a pacemaker to stimulate the heart when it is beating too slowly (see Cardiac pacemaker). If the heart is alternating between fast and slow rates, antiarrhythmic drugs may also be given in order to slow down the fast heart rate. If a pacemaker has been fitted, you will need regular checkups with a doctor or pacemaker technician, who will check the battery life and make any necessary adjustments to the pacemaker. These checks and adjustments are done from outside the body and so are not invasive or painful.
Sick sinus syndrome can usually be treated successfully with a pacemaker or drugs. However, the general outlook depends on the underlying condition.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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