Sick sinus syndrome

Overview

Sick sinus syndrome is the inability of the heart's natural pacemaker (sinus node) to create a heart rate that's appropriate for the body's needs. It causes irregular heart rhythms (arrhythmias). Sick sinus syndrome is also known as sinus node dysfunction or sinus node disease.

The sinus node is an area of specialized cells in the upper right chamber of the heart. This area controls your heartbeat. Normally, the sinus node creates a steady pace of electrical impulses. The pace changes depending on your activity, emotions, rest and other factors.

In sick sinus syndrome, the electrical signals are abnormally paced. Your heartbeat can be too fast, too slow, interrupted by long pauses — or an alternating combination of these rhythm problems. Sick sinus 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 have few or no symptoms. Symptoms may be mild or come and go — making them difficult to recognize at first.

Signs and symptoms of sick sinus syndrome may include:

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

When to see a doctor

Talk to your doctor if you have any signs or symptoms of sick sinus syndrome. Many medical conditions can cause these problems, and it's important to get a timely and accurate diagnosis.

If you have new or unexplained chest pain or suspect you're having a heart attack, call for emergency medical help immediately.

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 upper heart chamber (atrium).

This natural pacemaker produces electrical signals that trigger each heartbeat. From the sinus node, electrical signals 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 working properly, causing your heart rate to be too slow (bradycardia), too fast (tachycardia) or irregular.

Problems of the sinus node include the following:

  • Sinus bradycardia. The sinus node produces an electrical charge at a slower rate than normal.
  • Sinus arrest. Signals from the sinus node pause, causing skipped beats.
  • Sinoatrial exit block. Signals to the upper heart chambers are slowed or blocked, causing a pause or skipped beats.
  • Chronotropic incompetence. The heart rate is normal at rest, but doesn't increase with physical activity.
  • Bradycardia-tachycardia syndrome. The heart rate alternates between abnormally slow and fast rhythms, usually with a long pause (asystole) between heartbeats.

What makes the sinus node misfire?

Abnormalities of the sinus node may be caused by the following:

  • Age-related wear and tear of heart tissues
  • Heart disease
  • Inflammatory diseases affecting the heart
  • Damage to the sinus node or scarring from heart surgery
  • Medications to treat high blood pressure, including calcium channel blockers and beta blockers
  • Drugs to treat irregular heartbeats (arrhythmias)
  • Some Alzheimer's disease medications
  • Neuromuscular diseases, such as muscular dystrophy
  • Obstructive sleep apnea
  • Rare genetic mutations
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 node and then passes into the ventricles, causing them to contract and pump out blood.

Risk factors

Sick sinus syndrome can occur at any age, but it's most common in people in their 70s or older. Common heart disease risk factors may increase the risk of sick sinus syndrome:

  • High blood pressure
  • High cholesterol
  • Excess body weight
  • Lack of exercise

Complications

When your heart's natural pacemaker isn't working properly, your heart can't work as well 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

Your doctor will perform a physical exam and ask questions about your symptoms and medical history.

Symptoms of sick sinus syndrome — such as dizziness, shortness of breath and fainting — only occur when the heart is beating abnormally. You may not have symptoms at the time of your doctor's appointment.

To determine if your symptoms are related to problems with the sinus node and heart function, your doctor may use the following tests:

  • Electrocardiogram (ECG). During this test, sensors (electrodes) are attached to your chest and legs to create a record of the electrical signals traveling through your heart. The test might show patterns that indicate sick sinus syndrome, including a fast heart rate, slow heart rate or long pause in the heartbeat after a fast heart rate.
  • Holter monitor. This portable ECG 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. You may be asked to keep a diary of symptoms.
  • Event recorder. This portable ECG, which may be worn up to a month, enables your doctor to correlate symptoms and heart rhythm. When you feel symptoms, you push a button, and a brief ECG recording is saved.
  • Other monitors. Some personal devices, such as smart watches, offer electrocardiogram monitoring. Ask your doctor if this is an option for you.
  • Implantable loop recorder. This small ECG device is implanted just under the skin of your chest and is used for continuous, long-term monitoring of your heart's electrical activity, particularly if you have infrequent 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 being performed

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

The primary treatment goals are to reduce or eliminate symptoms and to manage and treat any other health conditions that may be contributing to sick sinus syndrome.

If you don't have symptoms, your doctor may recommend regularly scheduled exams to monitor your condition. For most people with symptoms, the treatment is an implanted electronic pacemaker. If your symptoms are mild or infrequent, the decision to use a pacemaker will depend on results of ECG exams, your overall health, and the risk of more-serious problems.

Medication changes

Your doctor will likely check your current medications to see if any could be interfering with the function of your sinus node, including some medications used to treat high blood pressure or heart disease. Your doctor may adjust these medications or prescribe alternatives.

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) in the right atrium to pace the heart rate. However, most people with sick sinus syndrome benefit from dual-chamber pacemakers. One lead in the right atrium paces the upper chambers, and one lead in the right ventricle paces the lower chambers.

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

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 medications to prevent or to slow down 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), dabigatran (Pradaxa) or other similar medications.
  • AV node ablation. This procedure also can 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.
  • Cardiac ablation for atrial fibrillation. This procedure is similar to AV node ablation. However, in this case, ablation targets heart tissues that can lead to atrial fibrillation. This actually eliminates atrial fibrillation itself, rather than just preventing it from reaching the ventricles.
A heart during 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).

Catheters positioned in the heart for 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

You many not necessarily prevent sick sinus syndrome, but you can take steps to keep your heart as healthy as possible and lower your risk of cardiovascular disease:

  • Exercise and eat a healthy diet. Live a heart-healthy lifestyle by exercising regularly. Eat a diet with generous portions of nonstarchy vegetables, fruit and whole grains and modest portions of fish, lean meats, poultry and dairy.
  • Maintain a healthy weight. Being overweight increases your risk of developing heart disease. Ask your doctor what your goal weight should be.
  • 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 use.
  • Don't use illegal drugs. Talk to your doctor about an appropriate program 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

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

Be prepared to answer questions about your medical history and symptoms. Write down your answers to help you remember details.

Questions your doctor may ask about symptoms include:

  • Do your symptoms include feeling lightheaded or dizzy?
  • Have you ever fainted?
  • Do you have rapid, fluttering or pounding heartbeats?
  • Do you feel pressure, heaviness, tightness or pain in your chest?
  • Does exercise or physical exertion worsen your symptoms?
  • Does anything improve your symptoms?
  • How often have you experienced symptoms?
  • How long have the symptoms lasted?

Other questions may include the following:

  • Have you been diagnosed with high blood pressure, high cholesterol, diabetes or a heart condition?
  • What medications do you take and what dosage? Who is the prescribing doctor?
  • Why were the prescription drugs prescribed?
  • Have you been taking the medication as prescribed?
  • Have you recently stopped, started or changed medications?
  • What over-the-counter medications, herbal remedies or supplements do you take?

Write down any questions you have for your doctor. You might bring a companion to write down information during the appointment.

What you can do in the meantime

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

Last Updated Mar 17, 2020


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