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 1 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, or beats, it pumps blood throughout 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. These include 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 lightheaded 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. They will do an electrocardiogram ("ECG"), which 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 of 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 30 days. You wear these monitors all of the time while you do your usual activities.

●Exercise stress test – During this test, the doctor records 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 might need treatment. Treatment can include:

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

●Pacemaker – A pacemaker is a device that sits under the skin near your heart (figure 4). It sends electrical signals to your heart. These signals help your heart beat at a normal rate.

More on this topic

Patient education: Overview of heart arrhythmias (The Basics)
Patient education: Bradycardia (The Basics)
Patient education: Tachycardia (The Basics)
Patient education: Syncope (fainting) (The Basics)
Patient education: Shortness of breath (The Basics)
Patient education: ECG and stress test (The Basics)
Patient education: Pacemakers (The Basics)
Patient education: Ambulatory heart monitoring (The Basics)

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