How Sick Sinus Syndrome Affects Your Heart

Sick sinus syndrome (SSS), also known as sinus node dysfunction, describes a group of problems that affect your heart rhythm. It happens when a defect occurs with your sinus node, also known as the sinoatrial node or SA node. Your sinus node controls the pace of your heartbeat.

The sinus node acts as your heart's pacemaker. It conducts and sends electrical signals to make your atria (upper heart chambers) contract.

Failure of the sinus node can lead to an increase, decrease, or total failure of your heart's pacemaker function. Your heart rate can become unable to meet the needs of your body.

This article describes everything you need to know about sick sinus syndrome. It includes SSS types, causes, risk factors, symptoms, diagnosis, treatment, and outlook.

Types of Sick Sinus Syndrome (SSS)

At rest, a healthy sinus node produces electrical impulses for a heart rate of between 60 and 100 beats per minute. This is a normal sinus rhythm or normal heart rhythm.

Sick sinus syndrome occurs when damage or disease to the sinus node causes sinus arrhythmia (irregular sinus signals) that is too slow, too fast, or erratic. The resulting abnormalities can occur:

• Tachycardia-bradycardia (or tachy-brady) syndrome: A heart rate that alternates between abnormally fast (tachycardia) and abnormally slow (bradycardia) rhythms, often with a long pause between heartbeats, affecting 50% of people with SSS
• Sinus bradycardia: A resting heart rate of under 60 beats per minute caused by the sinus node
• Sinus arrest or pause: Signals from the sinus node pause, resulting in skipped beats
• Sinoatrial exit block: Pauses or skipped beats occurring when signals to the upper chambers are slowed or blocked
  
• Chronotropic incompetence: A heart rate that is within regular range at rest but does not increase as it should with physical activity or other types of demand
  

Bradycardia

What Causes SSS?

SSS typically affects adults over age 50. The most common cause of SSS is the slow development of progressive fibrosis or damage to your sinus node that occurs with aging. However, its exact cause is typically impossible to define. When SSS occurs in children, it often develops due to damage to the atrium during cardiac surgery to correct congenital heart defects.

Generally, any condition that causes heart damage can also damage your sinus node. People with SSS may develop it because of intrinsic causes (causes that originate from structural or functional changes within the sinus node) or extrinsic causes (causes related to external factors that cause abnormalities of the sinus node).

Potential intrinsic causes of sick sinus syndrome include the following:

• Acute myocardial infarction (heart attack)
• General coronary artery disease
• Atrial fibrillation (AFib) (fast and irregular heartbeats from your heart's upper chambers)
• Cardiomyopathy (disease of the heart muscle)
• Congenital ion channel dysfunction (defects in proteins called ion channels)
• Connective tissue diseases such as lupus, rheumatoid arthritis, and Sjögren's syndrome
• Embolization (blockage) of the sinoatrial node artery
• Muscular dystrophy
• Postsurgical changes or surgical injury to the sinoatrial node

Potential extrinsic causes of sick sinus syndrome include the following:

• Diabetes mellitus
• Hypertension (high blood pressure)
• Certain types of medications, like antiarrhythmic drugs (medications that treat cardiac arrhythmias, abnormal heart rhythms), beta-blockers, Cordarone or Pacerone (amiodarone), Elavil (amitriptyline), Lanoxin (digoxin), Tagamet (cimetidine), lithium, cannabis, non-dihydropyridine calcium channel blockers, and sympatholytic drugs (decrease the activity of the sympathetic nervous system)
• Metabolic abnormalities including hypocalcemia (low levels of calcium), hypothyroidism (insufficient thyroid hormones), hypoxemia (insufficient oxygen in your blood), hyperkalemia (high potassium levels), and hypokalemia (lower than normal levels of potassium)
  

Risk Factors for SSS

Most cases of SSS occur in older men and women. However, you can develop sick sinus syndrome at any age. The condition results when age or other factors slow down your heart rate and lower the natural pacemaker function of your sinus node.

Having one or more of the following conditions increases your risk for SSS:

• Age 50 or older
• History of myocardial infarction or general coronary artery disease
  
• Cardiomyopathy or heart failure (inability of your heart to pump sufficient blood for your body's needs)
  
• Rheumatic fever, pericarditis, Chagas disease, myocarditis, or other inflammatory conditions that can involve your heart
• Sarcoidosis, amyloidosis, hemochromatosis, scleroderma, or other infiltrative cardiac diseases (heart diseases characterized by the deposit of abnormal substances within your heart tissue)
• History of any chronic disease linked to sinus node dysfunction
• Rare congenital diseases
• Trauma
• Taking medications that cause dysfunction of the sinoatrial node, such as beta-blockers, calcium channel blockers, digoxin, or medications that treat cardiac arrhythmias

Symptoms of SSS

SSS can be asymptomatic in its early stages. When symptoms occur, they can come and go, or become progressively worse.

Symptoms of SSS can include the following:

• Bradycardia (slower than the normal pulse, usually fewer than 60 beats per minute)
• Syncope (fainting)
• Persistent fatigue
• Weakness
• Dyspnea (shortness of breath) especially during exertion
• Angina (chest pain)
• Disturbed sleep
• Confusion
• Heart palpitations (heartbeat that can be pounding, racing, or fluttering)
  

Diagnosing Sick Sinus Syndrome

Diagnosing sick sinus syndrome can be a challenge. Symptoms often resemble other types of heart problems, so finding their cause can require more than one type of evaluation. Symptoms may also be mild and intermittent, occurring well before people seek care.

A diagnosis of sinus node dysfunction is reached when cardiac monitoring links your symptoms to bradyarrhythmia. Reaching this diagnosis can involve the following evaluations:

• Medical history and physical examination
• Medication review to assess for potential drug-related causes
• Basic chemical panel (blood test) and other laboratory tests needed to identify metabolic abnormalities such as hypothyroidism that may be the source of symptoms

Electrocardiography tests are also uses and include the following:

• (ECG or EKG)Eelectrocardiogram : A noninvasive diagnostic test that uses flat metal electrodes placed on your chest to evaluate the electrical activity of your heart during beating
• Echocardiogram: A noninvasive ultrasound imaging test used to observe your heart and diagnose any structural defects
• Holter monitor: A monitor worn externally as you go about your day that records the electrical activity of your heart for a period of 24 or 48 hours, and sometimes for several weeks, to evaluate any cardiac arrhythmias that may have occurred during the monitoring period
  
• External patch recorder: External, small, leadless patch that provides continuous monitoring, similar to a loop recorder, for two to 14 days
  
• Event monitor or patient-activated loop recorder: An eternal lead or armband monitor that is activated when symptoms occur to record your heart's electrical signals for two to four weeks at a time, which is transmitted remotely to a monitoring station
• Implantable loop recorder: A loop recorder implanted under the skin of your chest to provide continuous monitoring of your heart's electrical signals for the longest period of time, lasting from one to two years, with the remote transmission of data
• Electrophysiologic testing: Not commonly used, this minimally invasive procedure records your heart's electrical activity from within using catheters that are threaded into your heart through a vein in your groin
  

How SSS Is Treated

There is no cure for SSS. Treatment for SSS varies by individual. The goal of SSS treatment is to correct the cause of sinus node abnormalities and restore normal function.

Some causes of SSS, such as medications or metabolic abnormalities are reversible by treating the underlying disorder. The problem may not have to be treated if symptoms aren't present.

When symptoms occur, treatment may include the following:

• Artificial pacemaker: Most people with sick sinus syndrome are treated with a permanent artificial pacemaker. SSS is the most common reason that people receive an artificial pacemaker. An artificial pacemaker is a small, battery-powered device. It is implanted under the skin of your chest during minor surgery. An artificial pacemaker is attached to your heart by wires that monitor your heart rate. It replaces your SA node by sending electrical signals to your heart so it can beat normally.
• Medication changes: Treatment for SSS may involve changing your medication regimen if you are using any drugs known to increase your risk of symptoms. Consult your healthcare provider before changing or stopping any prescribed medications. Changing medications without medical supervision may worsen other medical conditions.
• Medication control of SSS: Medication control of sinus node dysfunction may be a secondary option for people who decline permanent pacemaker placement. However, the role of medications in long-term SSS disease progression and mortality is unclear. In some people, phosphodiesterase inhibitors have proven successful in symptom control. Other medications such as dopamine, atropine, and epinephrine have been used effectively for short-term control, but are not appropriate for the long-term management of sick sinus syndrome.
  

Outlook for SSS

SSS is typically a chronic and progressive disease. Its outlook varies by individual based on other risk factors such as other chronic health problems and medications taken to treat other heart problems.

When other chronic conditions are not a factor, people with SSS who have symptoms treated with a permanent, implanted pacemaker typically have an excellent outlook.

Possible Complications

Sick sinus syndrome typically worsens over time. As the disorder progresses and your heartbeat becomes more irregular more often, you have a higher chance of developing one of the following complications:

• Angina
• Decreased exercise capacity
• Syncope
• Falls or injuries as a result of fainting
• Heart failure (heart becomes unable to enough blood to meet your body's needs)
• Cardiac arrest
• Atrial fibrillation
• Poor heart pumping
• Impaired blood flow leading to organ damage related to impaired kidney function, brain function, and stroke (a deficiency of blood flow to an area of your brain)

When to See a Healthcare Provider

It can be difficult to determine when to see a healthcare provider for changes in your heart rate. A heart rate that beats abnormally fast, slow, or suddenly switches from fast to slow can occur as a result of your body's normal responses to factors like exercise, stress, or eating certain foods.

An average adult resting heart rate is typically 60 to 100 beats per minute (bpm). This heart rate is usually not affected by low or moderate exercise. However, frequently having a sudden spike in heart rate while resting may indicate a need for treatment.

Having a heart rate above or below a normal resting heart rate is not always a sign of a medical problem. However, it is possible that these sensations require medical treatment. In extreme cases, they may be a sign of a cardiac arrhythmia (a problem with your heart's electrical system).

Seek immediate attention if you have the following symptoms with a rapid heart rate or a heart rate that beats hard but not fast for long periods:

• Chest pain
• Shortness of breath
• Loss of consciousness
• Repeated dizziness or light-headedness
• Unusual sweating
• Fatigue
• Heart palpitations (feeling that your heart is skipping a beat, racing, or fluttering)
• Belly pain, vomiting, and nausea
  
• Back pain
  

Summary

Sick sinus syndrome (SSS) describes a group of heart rhythm problems that occur when your sinus node does not work right. It results in abnormal signals to your heart. This causes a heart rate that beats too slowly, too fast, or erratically.

While this problem most often affects older men and women, it can happen to anyone who has risk factors. Treatment usually involves an artificial pacemaker that ensures your heart receives normal signals.

Sick sinus syndrome is a chronic problem. While some people do not have symptoms, others have lifelong problems that get worse over time.

Getting the right diagnosis can help reduce your risk of problems with sick sinus syndrome. For most people with SSS, getting a pacemaker can improve their quality of life and long-term outlook.