Bradycardia

1 What is Bradycardia?

Bradycardia is a condition when your heart beats slower than normal.

During rest, in a normal adult, the heart usually beats between 60 and 100 times a minute.

If you have bradycardia, your heart will beat less than 60 times a minute. It can be a serious concern if your heart is unable to pump sufficient oxygen-rich blood to your body.

However, in some people, bradycardia does not cause any symptoms or complications.

For instance, physically active individuals usually have a heart rate less than 60 beats per minute without causing any symptoms.

The heart will beat at a slower rate during deep sleep. Several treatments are available including an implanted pacemaker device to correct bradycardia.

2 Symptoms

Bradycardia can lead to situations in which your major organs do not receive enough oxygen-rich blood and this results in signs and symptoms such as:

  • Fatigue and getting tired easily during physical activity
  • Feeling dizzy or fainting (syncope)
  • Chest pain and shortness of breath
  • Confusion or memory problems
  • Cardiac arrest (in extreme cases)

When is a slow heart rate considered normal?

  • A resting heart rate lesser than 60 beats a minute may be considered normal in young, otherwise healthy adults and trained athletes.

There are several conditions that can give rise to signs and symptoms of bradycardia.

Therefore, it is necessary to get an early, precise diagnosis along with appropriate care.

Consult your doctor if you or your child come across any of the symptoms of bradycardia.

If you feel light-headed, have difficulty breathing or have chest pain that lasts for more than a few minutes, seek emergency care or call 911.

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3 Causes

Bradycardia can be caused by anything that interrupts the normal pattern of electrical impulses controlling the heart rate.

The following factors can lead to or contribute to problems within your heart's electrical system:

  • Damage to the heart tissue as a result of aging or from heart conditions such as a heart attack
  • High levels of blood pressure (hypertension)
  • Congenital heart defects
  • Infection of the heart tissues called myocarditis
  • A complication following heart surgery
  • Underactive thyroid glands or hypothyroidism
  • Imbalance of mineral-related substances required for conduction of electrical impulses (electrolytes)
  • Repeated pauses in breathing during sleep (obstructive sleep apnea)
  • Inflammatory diseases such as rheumatic fever or lupus
  • The accumulation of iron in the organs (hemochromatosis)
  • Medications given for other heart rhythm disorders, high blood pressure and psychosis
  • Electrical circuitry of the heart

Normal functions

Your heart is made up of four chambers — two upper chambers (atria) and two lower chambers (ventricles).

Your heart's rhythm is controlled by a natural pacemaker (the sinus node) situated in the right atrium.

This sinus node is responsible for the production of electrical impulses that are required for the initiation of each heartbeat.

From the sinus node, the electrical impulses pass across the atria, resulting in contraction of the atria, which pumps blood into the ventricles.

The electrical impulses then reach a cluster of cells called the atrioventricular (AV) node, which transmits the signal to a specialized collection of cells called the bundle of His.

These cells, in turn, transmit the signal down to their left branch that serves the left ventricle and to the right branch, serving the right ventricle.

As a  result, the ventricles contract and pump blood — the right ventricle sends deoxygenated blood to the lungs and the left ventricle pumps oxygen-rich blood to the body.

Bradycardia results if these electrical signals slow down or are blocked.

Sinus node problems

Bradycardia commonly starts in the sinus node.

A slow heart rate may be a result of problems in the sinus node such as:

  • Discharge of electrical impulses at a rate slower than normal  
  • There may be interruptions or failure to discharge at a regular rate
  • Discharge of an electrical impulse that gets blocked before causing atrial contraction

In some cases, the sinus node problems may cause alternating slow and fast heart rates called bradycardia-tachycardia syndrome.

  • Heart block (atrioventricular block): Bradycardia may also result when electrical signals transmitted through the atria do not get transmitted to the ventricles (heart block, or atrioventricular block). The interruption in transmission of the electrical signal may occur in the AV node, the bundle of His, or along its left and right branches. Heart blocks are classified depending on the degree to which electrical signals from the atria reach your ventricles.
  • First-degree heart block: This is the mildest form of heart block in which all electrical signals from the atria reach the ventricles, but the signal is slightly slowed down. This rarely gives rise to any symptoms and does not need any treatment.
  • Second-degree heart block: With this type of blockage, all the electrical signals do not reach the ventricles. Some beats may get  "dropped," which results in a slower and irregular rhythm.
  • Third-degree (complete) heart block: In third-degree heart block, none of the electrical impulses from the atria successfully reach the ventricles. With such condition, the bundle of His or other tissues of the ventricles take the role of a substitute pacemaker for the ventricles. These substitutes produce slow and sometimes unreliable electrical impulses to control the beat of the ventricles.
  • Bundle branch block: The disruption of an electrical signal in the right or left bundle branches, towards the end of the pathway of electrical impulses is called a bundle branch block. The seriousness of bundle branch blocks vary and depend on whether both the branches are affected, the presence of other types of heart block and the degree of heart tissue damage.

4 Making a Diagnosis

After your family doctor evaluates your condition or following emergency care, you will be referred to a cardiologist for a complete diagnostic assessment of bradycardia.

Ask a family member or a friend who can give you some moral support to accompany you, if possible.

You can make a list of things you need to discuss with your doctor.

This list may include:

  • All the symptoms you have gone through, including those that may seem unrelated to your heart condition
  • Key personal information, including any major stresses or recent changes in your life
  • The regular medications you take including vitamins or herbal supplements
  • Questions to ask your doctor, in the order of their importance

Basic questions to ask your doctor include:

  • What is the most likely the cause for my slow heart rate?
  • What kinds of diagnostic tests do I need?
  • What is the most appropriate treatment available?
  • What type of risks does my heart condition involve?
  • What tests are available for monitoring my heart condition?
  • How often should I attend follow-up appointments?
  • How will other conditions that I have affect my heart problem?
  • Do I need to restrict any physical activities?
  • Are there any brochures/printed material or websites that I can refer to for more information?

Your doctor is likely to ask you a number of questions such as :

  • When did your first symptom appear?
  • Have you gone through fainting spells in the past?
  • Does anything, such as exercise, worsen your symptoms?
  • Are you a smoker?
  • Are you undergoing treatment for other heart diseases such as high blood pressure, high cholesterol or other conditions that affect your circulatory system?
  • Are you on any medications for these conditions and do you take them as advised?

In order to diagnose your condition, your doctor will review your symptoms, review your medical and family history and conduct a physical examination.

Your doctor will also order a series of tests to measure your heart rate, establish a link between a slow heart rate and your symptoms and identify conditions that may be causing bradycardia.

  • Electrocardiogram (ECG or EKG): An electrocardiogram, also called an ECG or EKG, is a primary tool for evaluating bradycardia. An ECG uses small sensors (electrodes) attached to your chest and arms to record electrical signals as they travel through your heart. Your doctor can look for patterns among these signals to determine what kind of bradycardia you have.

Your doctor may also have you use a portable ECG device at home to provide more information about your heart rate and to help establish a correlation between a slow heart rate and the onset of symptoms.

These devices include:

  • Holter monitor: This portable ECG device is carried in your pocket or worn on a belt or shoulder strap. It can record your heart's activity for an entire 24-hour period, which provides your doctor with a prolonged look at your heart rhythms. Your doctor will most likely ask you to keep a diary during the same 24 hours. You'll describe any symptoms you experience and record the time they occur.
  • Event recorder: This portable ECG device is intended to monitor your heart activity over the course of a few weeks to a few months. You activate it only when you experience symptoms that may be related to a slow heart rate. When you feel symptoms, you push a button, and an ECG strip is recorded for a few minutes. This permits your doctor to determine your heart rhythm at the time of your symptoms.

Your doctor may also use an ECG monitor while performing other tests to understand the impact of bradycardia.

These tests include:

  • Tilt table test: This test helps your doctor better understand how your bradycardia contributes to fainting spells. You lie flat on a special table, and then the table is tilted as if you were standing up. Changes in the position may cause a fainting spell and help your doctor to establish a link between your heart rate and fainting episodes.
  • Exercise test: Your doctor may monitor your heart rate while you walk on a treadmill or ride a stationary bike to see whether your heart rate increases appropriately in response to physical activity.
  • Laboratory and other tests: Your doctor will order blood tests to screen for underlying conditions that may be contributing to bradycardia, such as an infection, hypothyroidism or an electrolyte imbalance. If sleep apnea is suspected of contributing to bradycardia, you may undergo tests to monitor your sleep patterns.

5 Treatment

The treatment of bradycardia depends on the type of electrical conduction problem involved, the severity of your symptoms and the underlying cause of your slow heart rate.

  • Treating underlying conditions: If an underlying disorder such as hypothyroidism or obstructive sleep apnea is the cause for your slow heart rate, the treatment of the disorder can correct your bradycardia.
  • Alterations in medications: Several medications including some that are prescribed for other heart conditions may give rise to bradycardia. Your doctor will evaluate the medications you are taking and may advise alternative treatments. Prescribing a different medicine or modifying the dosage may help in correcting bradycardia.
  • Pacemaker: A pacemaker is a small battery-operated device about the size of a cellphone. It is implanted under your collarbone. The wires from this device are passed through the veins and into your heart. The electrodes present at the end of these wires are attached to the tissues of the heart. It monitors your heart rate and creates electrical impulses when necessary, in order to maintain an appropriate rate. Some pacemakers can capture and record information that your cardiologist will read in order to monitor the condition of your heart. Regular follow-up appointments will be scheduled to ensure proper functioning of your pacemaker and your heart.

6 Prevention

The most efficient method of preventing bradycardia is to reduce risk factors that contribute to the development of heart disease.

If you are suffering from heart disease, closely monitor it and follow a treatment plan advised by your doctor to decrease your risk of developing bradycardia.
    

Prevention of heart disease

In order to prevent heart disease, you can follow these precautions:

  • Regular exercise and a healthy diet: Follow a heart-healthy lifestyle by exercising regularly and adapting a healthy diet, which is low in fat and rich in fruits, vegetables, whole cereals and grains.
  •  Maintain your weight within the recommended range for your height: Being overweight or severely obese makes you more susceptible to heart disease.
  • Keep your blood pressure and cholesterol level within normal range: Make positive lifestyle modifications and take your daily medications prescribed by your doctor to keep high blood pressure (hypertension) or high cholesterol levels under control.
  • Quit smoking and stop alcohol use: If you are a smoker and you are unable to quit the habit on your own, discuss with your doctor the strategies or programs that may help you discontinue your smoking habit. If you drink alcohol, you may have it in moderate amounts, but doctors recommend to completely avoid the use of alcohol for some conditions. Your doctor will give specific advice while taking your heart condition into consideration. If you find it difficult to control your use of alcohol, ask your doctor for a program that helps you stop drinking.
  • Avoid the use of recreational drugs: Discuss with your doctor about the choice of an appropriate program if you need help in terminating recreational drug use.
  • Manage your stress effectively: Avoid getting subjected to unnecessary stress and learn coping techniques that help you handle normal daily stress in a healthy way.
  • Attend scheduled checkups: During your regular scheduled visits to your doctor, physical examination and evaluation of your signs and symptoms will be done.

Treatment and monitoring of existing heart disease

If you are having a heart disease, these measures can help cut-down your risk of developing bradycardia or other disorders of heart rhythm disorder:

  • Follow your treatment plan correctly: Be sure you know your treatment plan well, and take all the medications prescribed by your doctor.
  • Report any changes promptly: In case your existing symptoms change, become worse or if you have developed new symptoms, inform your doctor immediately.

7 Risks and Complications

Age is the most important risk factor in the development of bradycardia.

Heart problems that are often associated with bradycardia are more likely to occur in elderly people.

  • Risk factors related to heart disease: Bradycardia often occurs associated with heart tissue damage, which results from some type of heart disease. As a result, factors that increase your risk of heart disease may also increase the risk of bradycardia.

Adoption of a heart-healthy lifestyle, modifications and medical treatment may help decrease the risk of heart disease associated with the following factors:

  • High blood pressure
  • Smoking and heavy consumption of alcohol
  • Use of recreational drugs
  • Mental stress or anxiety

If left untreated, complications of bradycardia may occur depending on the severity of heart tissue damage.

Possible complications of the slow heart rate may include:

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