Harvard Heart Letter

What is sick sinus syndrome?

Ask the doctor

Q. After I experienced a few fainting episodes, I was diagnosed with sick sinus syndrome. My doctor says I might need a pacemaker. Can you tell me more about this condition?

A. Despite the name, sick sinus syndrome has nothing to do with your nasal passages. Instead, it refers to various heartbeat irregularities that can cause dizziness, fainting, or shortness of breath. Most cases are due to age-related changes in the heart muscle that disrupt the heart’s electrical system. Sometimes, another form of heart disease or medication that slows the heart is to blame. Sick sinus syndrome is most common in people in their 70s and 80s.

Each time your heart beats, a tiny jolt of electrical current triggers the heart muscle to contract. The stimulus is sent by the sinus node (also called the sinoatrial node), a cluster of cells in the upper right portion of your heart that acts as your body’s natural pacemaker. If your heart rate is 60 beats per minute, the sinus node will send out an impulse approximately once per second.

If your sinus node fails to send out signals quickly enough to keep your heart beating at the pace needed to supply your body with fresh blood and oxygen, you will probably notice that something is amiss. When a malfunctioning sinus node shuts down for five or six seconds, your heartbeat is put on pause, which is likely to make you pass out. A fainting episode itself does not cause lasting damage to the heart. But the consequences may be severe if you happen to hit your head as you fall or if you’re driving a car.

Another manifestation of a sinus node abnormality is tachy-brady syndrome, which means the heart rate alternates between a pace that is too fast (tachycardia) and one that is too slow (bradycardia). This heart rhythm pattern often occurs in people with atrial fibrillation, in which the upper chambers of the heart beat in a rapid, disorganized pattern.

In addition to dizziness and fainting, other possible symptoms of sick sinus syndrome include feeling as though your heart is beating too fast, too slow, or skipping beats. Some people have chest pain, trouble breathing, fatigue, weakness, or confusion.

If your doctor has ruled out other treatable conditions or medications as the cause of your sick sinus syndrome, then the standard treatment is placement of a permanent pacemaker. This small, battery-powered device is implanted under the skin in the upper chest during a minor surgical procedure. The device is programmed to stimulate or “pace” your heart as needed to keep it beating normally, and is a very safe and relatively long-lasting solution.

— by Deepak L. Bhatt, M.D., M.P.H.Editor in Chief, Harvard Heart Letter

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