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Sick sinus syndrome

Medically reviewed on February 15, 2018.

Overview

Sick sinus syndrome — also known as sinus node disease or sinus node dysfunction — is a group of heart rhythm problems (arrhythmias) in which the heart's natural pacemaker (sinus node) doesn't work properly.

The sinus node is an area of specialized cells in the upper right chamber of the heart that controls the rhythm of your heart. Normally, the sinus node produces a steady pace of regular electrical impulses. In sick sinus syndrome, these signals are abnormally paced.

The heart rhythms of a person with sick sinus syndrome can be too fast, too slow, punctuated by long pauses — or an alternating combination of these rhythm problems. The syndrome is relatively uncommon, but the risk of developing it increases with age.

Many people with sick sinus syndrome eventually need a pacemaker to keep the heart in a regular rhythm.

Symptoms

Most people with sick sinus syndrome initially have few or no symptoms. In some cases, symptoms come and go.

When they occur, sick sinus syndrome signs and symptoms might include:

  • Slower than normal pulse (bradycardia)
  • Fatigue
  • Dizziness or lightheadedness
  • Fainting or near fainting
  • Shortness of breath
  • Chest pains
  • Confusion
  • A sensation of rapid, fluttering heartbeats (palpitations)

When to see a doctor

If you have lightheadedness, dizziness, fainting, fatigue, shortness of breath or palpitations, talk to your doctor. Many medical conditions can cause these signs and symptoms — including sick sinus syndrome — and it's important to identify the problem.

Causes

Your heart is made up of four chambers — two upper (atria) and two lower (ventricles). The rhythm of your heart is normally controlled by the sinus node, an area of specialized cells in the right atrium.

This natural pacemaker produces the electrical impulses that trigger each heartbeat. From the sinus node, electrical impulses travel across the atria to the ventricles, causing them to contract and pump blood to your lungs and body.

If you have sick sinus syndrome, your sinus node isn't functioning properly, causing your heart rate to be too slow (bradycardia), too fast (tachycardia) or irregular.

Types of sick sinus syndrome and their causes include:

  • Sinoatrial block. Electrical signals move too slowly through the sinus node, causing an abnormally slow heart rate.
  • Sinus arrest. The sinus node activity pauses, causing skipped beats.
  • Bradycardia-tachycardia syndrome. The heart rate alternates between abnormally fast and slow rhythms, usually with a long pause (asystole) between heartbeats.

What makes the sinus node misfire?

Diseases and conditions that cause scarring or damage to your heart's electrical system can be the reason. Scar tissue from a previous heart surgery also can be the cause, particularly in children. Rarely, the cause can be genetic.

Sick sinus syndrome can be unmasked by medications, such as calcium channel blockers or beta blockers used to treat high blood pressure, or by other conditions causing the heartbeat to be slower or faster than normal. In most cases, the sinus node doesn't work properly because of age-related wear and tear to the heart muscle.

Normal heartbeat

In a normal heart rhythm, a tiny cluster of cells at the sinus node sends out an electrical signal. The signal then travels through the atria to the atrioventricular (AV) node and then passes into the ventricles, causing them to contract and pump out blood.

Risk factors

Sick sinus syndrome can occur at all ages, even infancy. Because it usually develops over many years, it's most common in people over age 65.

In rare cases, sick sinus syndrome can be associated with certain conditions such as muscular dystrophy and other diseases that may affect the heart.

Complications

When your heart's natural pacemaker isn't working properly, your heart can't perform as efficiently as it should. This can lead to:

  • Atrial fibrillation, a chaotic rhythm of the upper chambers of the heart
  • Heart failure
  • Stroke
  • Cardiac arrest

Diagnosis

Symptoms of sick sinus syndrome — such as dizziness, shortness of breath and fainting — are symptoms of numerous conditions. However, in sick sinus syndrome, these symptoms only occur when the heart is beating abnormally.

To diagnose and treat sick sinus syndrome, your doctor will conduct a physical exam and gather a medical history. He or she will seek to connect your symptoms to an abnormal heart rhythm.

Testing for sick sinus syndrome might include:

  • Electrocardiogram (ECG). During this test, sensors (electrodes) are attached to your chest and limbs to create a record of the electrical signals traveling through your heart. The test might show patterns that indicate sick sinus syndrome, including fast heart rate, slow heart rate or a long pause in the heartbeat (asystole) after a fast heart rate.
  • Holter monitor. This portable device is carried in your pocket or in a pouch on a belt or shoulder strap. It automatically records your heart's activity for 24 to 72 hours, which provides your doctor with an extended look at your heart rhythms.
  • Event recorder. This portable electrocardiogram device can also be carried in your pocket or worn on a belt or shoulder strap for home monitoring of your heart's activity. You might be asked to use this device to use for up to a month.

    When you feel symptoms, you push a button, and a brief ECG recording is saved. This allows your doctor to see your heart rhythm at the time of your symptoms, which can help pinpoint sick sinus syndrome.

  • Implantable loop recorder. This small device is implanted just under the skin of your chest and is used for continuous, long-term monitoring of your heart's electrical activity. An implantable loop recorder may be worn from months to years.

    This device is automatically triggered by an irregular heart rhythm (arrhythmia) or you can trigger it when you feel symptoms.

Electrophysiologic testing

This test is rarely used to screen for sick sinus syndrome. However, in some cases, it can help check the function of your sinus node, as well as other electrical properties of your heart.

During this test, thin, flexible tubes (catheters) tipped with electrodes are threaded through your blood vessels to various spots along the electrical pathways in your heart. Once in place, the electrodes can precisely map the spread of electrical impulses during each beat and may identify the source of heart rhythm problems.

Electrocardiogram

An electrocardiogram monitors your heart rhythm for problems. Electrodes are taped to your chest to record your heart's electrical signals, which cause your heart to beat. The signals are shown as waves on an attached computer monitor or printer.

Holter monitor

A Holter monitor uses electrodes and a recording device to track your heart's rhythm for 24 to 72 hours. Your doctor can print an electrocardiogram strip using the data on the recording device to see your heart's rhythm during the period you wore the monitor.

Treatment

Treatment for sick sinus syndrome focuses on eliminating or reducing unpleasant symptoms. If you aren't bothered by symptoms, you may only need regular checkups to monitor your condition. For people who are bothered by symptoms, the treatment of choice is usually an implanted electronic pacemaker.

Medication changes

Your doctor will likely check your current medications to see if any could be interfering with the function of your sinus node. Medications used to treat high blood pressure or heart disease — such as beta blockers or calcium channel blockers — can worsen abnormal heart rhythms. In some cases, adjusting these medications can relieve symptoms.

Pacing the heart

Most people with sick sinus syndrome eventually need a permanent artificial pacemaker to maintain a regular heartbeat. This small, battery-powered electronic device is implanted under the skin near your collarbone during a minor surgical procedure. The pacemaker is programmed to stimulate or "pace" your heart as needed to keep it beating normally.

The type of pacemaker you need depends on the type of irregular heart rhythm you have. Some rhythms can be treated with a single chamber pacemaker, which uses only one wire (lead) to pace one chamber of the heart — in this case, the atrium. However, most people with sick sinus syndrome benefit from dual chamber pacemakers, in which one lead paces the atrium and one lead paces the ventricle.

You'll be able to resume normal or near-normal activities after you recover from pacemaker implantation surgery. The risk of complications, such as swelling or infection in the area where the pacemaker was implanted, is small.

Additional treatments for fast heart rate with images

If you have a rapid heart rate as part of your sick sinus syndrome, you may need additional treatments to control these rhythms:

  • Medications. If you have a pacemaker and your heart rate is still too fast, your doctor may prescribe anti-arrhythmia medications to prevent fast rhythms.

    If you have atrial fibrillation or other abnormal heart rhythms that increase your risk of stroke, you may need a blood-thinning medicine, such as warfarin (Coumadin, Jantoven) or dabigatran (Pradaxa).

  • AV node ablation. This procedure can also control fast heart rhythms in people with pacemakers.

    It involves applying radiofrequency energy through a long, thin tube (catheter) to destroy (ablate) the tissue around the atrioventricular (AV) node between the atria and the ventricles. This stops fast heart rhythms from reaching the ventricles and causing problems.

  • Radiofrequency ablation of atrial fibrillation. This procedure is similar to AV node ablation. However, in this case, ablation targets the tissue that triggers atrial fibrillation. This actually eliminates atrial fibrillation itself, rather than just preventing it from reaching the ventricles.
AV node ablation

In atrioventricular (AV) node ablation, doctors use radiofrequency energy to destroy the electrical connection between the upper and lower heart chambers (AV node), blocking the heart's electrical impulses. Once the AV node is destroyed, doctors then implant a small medical device to maintain a heart rhythm (pacemaker).

Cardiac ablation

Cardiac ablation is a procedure to scar or destroy tissue in your heart that's allowing incorrect electrical signals to cause an abnormal heart rhythm. Diagnostic catheters are threaded through blood vessels to your heart where they are used to map your heart's electrical signals. Ablation catheters transmit heat or cold to scar or destroy tissue. This illustration shows ablation catheters being applied near the pulmonary veins in a type of cardiac ablation called pulmonary vein isolation.

Lifestyle and home remedies

To keep your heart as healthy as possible and to treat or eliminate risk factors that can lead to heart disease:

  • Exercise and eat a healthy diet. Live a heart-healthy lifestyle by exercising regularly and eating a healthy, low-fat diet that's rich in fruits, vegetables and whole grains and low in saturated fats and simple sugars.
  • Maintain a healthy weight. Being overweight increases your risk of developing heart disease.
  • Keep blood pressure and cholesterol under control. Make lifestyle changes and take medications as prescribed to correct high blood pressure (hypertension) or high cholesterol.
  • Don't smoke. If you smoke and can't quit on your own, talk to your doctor about strategies or programs to help you break a smoking habit.
  • If you drink, do so in moderation. For some conditions it's recommended that you completely avoid alcohol. Ask your doctor for advice specific to your condition. If you can't control your alcohol use, talk to your doctor about a program to quit drinking and manage other behaviors related to alcohol abuse.
  • Don't use illegal drugs. Talk to your doctor about an appropriate program for you if you need help ending illegal drug use.
  • Control stress. Avoid unnecessary stress and learn coping techniques to handle normal stress in a healthy way.
  • Go to scheduled checkups. Have regular physical exams and report any signs or symptoms to your doctor.

Preparing for an appointment

Symptoms of sick sinus syndrome, if present at all, may be so mild that you don't realize they're cause for concern. For this reason, sick sinus syndrome might not be diagnosed until it's advanced, when the risk of complications is greater.

Call your family doctor or general practitioner if you have symptoms of sick sinus syndrome. You might be referred to a doctor trained in diagnosing and treating heart conditions (cardiologist).

Here's some information to help you prepare for your appointment.

What you can do

When you make the appointment, ask if you need to follow any pre-appointment restrictions, such as changing your activity level or your diet to prepare for diagnostic tests.

Make a list of:

  • Your symptoms and when they began
  • Key medical information, including other medical conditions you have and family history of heart disease
  • Medications, vitamins or supplements you take, including doses
  • Questions to ask your doctor

Take a family member or friend with you, if possible, to help remember what the doctor says.

For sick sinus syndrome, some questions to ask your doctor include:

  • What is likely causing my symptoms?
  • What are other possible causes for these symptoms?
  • What tests do I need?
  • What treatment approach do you recommend?
  • How will you monitor my health long term?
  • I also have another health problem. How can I manage them together?
  • Should my children or other close relatives be screened for heart problems?
  • Are there brochures or other printed material I can have? What websites do you recommend?

Don't hesitate to ask other questions.

What to expect from your doctor

Your doctor is likely to ask you questions, including:

  • Do your symptoms include feeling lightheaded or dizzy?
  • Have you ever fainted?
  • Do you have rapid, fluttering or pounding heartbeats (palpitations)?
  • Do you feel pressure, heaviness, tightness or pain in your chest (angina)?
  • Does exercise or physical exertion worsen your symptoms?

What you can do in the meantime

If exercise makes your symptoms worse, avoid exercise until your doctor has seen you.

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