Patient education: Sinus node dysfunction (The Basics)

What is sinus node dysfunction? — Sinus node dysfunction is a heart condition that can cause dizziness, chest pain, and fainting. It is caused by a problem with the heart's electrical system. Doctors used to call this condition "sick sinus syndrome."

Normal heartbeats happen when an electrical signal starts in one spot near the top of the heart. This signal follows a path to spread across the heart. As it spreads, the signal makes the heart muscle squeeze. Each time the heart squeezes ("beats"), it pumps blood all over the body. Normally, the heart beats in a regular way 60 to 100 times a minute.

In sinus node dysfunction, there is a problem with the spot that starts the heartbeat. Heartbeats don't start often enough. As a result, the heartbeat is slower than normal. Doctors use the term "bradycardia" when a heartbeat is slower than normal.

Some people with sinus node dysfunction also have episodes when their heartbeat is too fast, called "tachycardia."

People with sinus node dysfunction can have episodes in which a fast heartbeat quickly changes to a slow heartbeat. Because of this, doctors sometimes use the terms "tachycardia-bradycardia syndrome" or "tachy-brady syndrome" to describe sinus node dysfunction.

Different things can cause sinus node dysfunction, including heart conditions, other medical problems, and certain medicines.

What are the symptoms of sinus node dysfunction? — Some people with sinus node dysfunction have no symptoms.

When symptoms do happen, they can include:

●Feeling light-headed or dizzy

●Fainting or feeling like you are going to faint

●Trouble breathing, especially with exercise

●Chest pain, especially with exercise or when under stress

●Feeling like your heart is beating fast, beating hard, or skipping beats

Is there a test for sinus node dysfunction? — Yes. Your doctor or nurse will ask about your symptoms and do an exam. During the exam, they will check your pulse and listen to your heart. He or she will do an ECG (also called "electrocardiogram"). An ECG measures the electrical activity in your heart (figure 1).

Your doctor might also do other tests. These can help show what's causing the sinus node dysfunction and check for other problems with your heart. These tests can include:

●Longer-term heart monitoring – There are several devices that can be used for this. A "Holter" monitor is a small, portable machine you wear that records all your heart's electrical activity over 1 or 2 days (figure 2). There are also newer types of monitors called "patch monitors." These go directly on the skin, without wires, and can be worn for up to 14 days. You wear these monitors all the time while you go about your usual activities.

●An exercise stress test – During this test, the doctor will record your ECG while you exercise on a treadmill or bike (figure 3).

How is sinus node dysfunction treated? — Treatment depends on whether you have symptoms or not, and what's causing your sinus node dysfunction.

People who have no symptoms usually do not need treatment. But your doctor or nurse will see you for regular follow-ups to monitor your condition.

People who have symptoms usually need treatment. Treatment can include:

●Medicine changes – If a medicine is causing your sinus node dysfunction, the doctor will change or stop that medicine.

●A pacemaker – This is the treatment used most often for sinus node dysfunction. A pacemaker is a device that sits under the skin near a person's heart (figure 4). It sends electrical signals to the heart. These signals help the heart beat at a normal rate.

●Medicines – Doctors sometimes treat sinus node dysfunction with heart medicines, but these don't usually work as well as a pacemaker.

More on this topic

Patient education: Bradycardia (The Basics)
Patient education: Tachycardia (The Basics)
Patient education: Syncope (fainting) (The Basics)
Patient education: Shortness of breath (dyspnea) (The Basics)
Patient education: ECG and stress test (The Basics)
Patient education: Pacemakers (The Basics)

Patient education: Syncope (fainting) (Beyond the Basics)
Patient education: Shortness of breath (dyspnea) (Beyond the Basics)
Patient education: Pacemakers (Beyond the Basics)