Sick sinus syndrome — also known as sinus node disease or sinus node dysfunction — is the name for a group of heart rhythm problems (arrhythmias) in which the sinus node — the heart's natural pacemaker — 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.

A person with sick sinus syndrome may have heart rhythms that are too fast, too slow, punctuated by long pauses — or an alternating combination of all of these rhythm problems. Sick sinus syndrome is relatively uncommon, but the risk of developing sick sinus syndrome increases with age.

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

Source: http://www.mayoclinic.com

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

When they do occur, sick sinus syndrome symptoms may include:

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

Many of these signs and symptoms are caused by reduced blood flow to the brain when the heart beats too fast or too slowly.

When to see a doctor

If you have spells of 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.

Source: http://www.mayoclinic.com

Your heart is made up of four chambers — two upper chambers (atria) and two lower chambers (ventricles). The rhythm of your heart is normally controlled by the sinoatrial (SA) node — or sinus node — an area of specialized cells located 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 out to your lungs and body.

If you have sick sinus syndrome, your sinus node isn't functioning properly, so your heart rate may be too slow (bradycardia) or 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.
• 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 may be the cause, particularly in children.

Sick sinus syndrome may also be set off by medications, such as calcium channel blockers or beta blockers used to treat high blood pressure, heart disease or other conditions. However, in many cases, the sinus node doesn't work properly because of age-related wear and tear to the heart muscle.

Source: http://www.mayoclinic.com

Symptoms of sick sinus syndrome — such as dizziness, shortness of breath and fainting — are also symptoms of many other diseases and conditions.

However, in sick sinus syndrome, these symptoms only occur when the heart is beating abnormally. In order to diagnose and treat sick sinus syndrome, your doctor will need to establish a connection between your symptoms and an abnormal heart rhythm.

Electrocardiogram

Testing for sick sinus syndrome usually starts with a standard electrocardiogram (ECG). However, if your abnormal heart rhythms tend to come and go, they may not be detected during the brief time a standard ECG is recording. You may need additional types of ECG:

• Standard 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 may 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 an entire 24- to 48-hour period, which provides your doctor with an extended look at your heart rhythms. This type of monitoring can be very helpful for diagnosing sick sinus syndrome.

• 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 will often be given 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 may be triggered manually when you feel symptoms.

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 will often be given 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 may be triggered manually when you feel symptoms.

Electrophysiologic testing

This test isn't commonly used to screen for sick sinus syndrome. However, in some cases, electrophysiologic testing 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.

Source: http://www.mayoclinic.com

When your heart's natural pacemaker isn't working properly, your heart can't perform as efficiently as it should. This can lead to a very slow heart rate, which may cause fainting.

In rare cases, long periods of slow heart rate or fast heart rate can keep your heart from pumping enough blood to meet your body's needs — a condition called heart failure.

If you have a type of sick sinus syndrome called bradycardia-tachycardia syndrome, you also may be at a higher risk of developing a blood clot in your heart that may lead to a stroke. That's because the fast heart rhythm that occurs in bradycardia-tachycardia syndrome is often atrial fibrillation.

Atrial fibrillation is a chaotic rhythm of the upper chambers of the heart that can cause blood pooling in the heart. Blood clots are more likely to form when blood flow through the heart is altered in any way. A blood clot can break loose and travel to the brain, causing a stroke.

Source: http://www.mayoclinic.com

In some cases, inflammation and narrowed arteries caused by underlying heart disease can cause sick sinus syndrome. Your doctor may suggest that, in addition to other treatments, you make lifestyle changes that will keep your heart as healthy as possible.

Take the following steps to treat or eliminate risk factors that may 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.
• 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. If you drink alcohol, drink 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.

Source: http://www.mayoclinic.com

Sick sinus syndrome can occur in people of all ages, even infants. Because it usually develops slowly, over many years, it's most common in people around age 70.

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

Source: http://www.mayoclinic.com