Bradycardia is a slower than normal heart rate. The heart usually
beats between 60 and 100 times a minute in an adult at rest. If you have
bradycardia (brad-e-KAHR-de-uh), your heart beats fewer than 60 times
Bradycardia can be a serious problem if the heart doesn't pump enough
oxygen-rich blood to the body. For some people, however, bradycardia
doesn't cause symptoms or complications.
An implanted pacemaker and other treatments may correct bradycardia and help your heart maintain an appropriate rate.
If you have bradycardia, your brain and other organs may not get the
supply of oxygen they need. As a result, you may experience these
* Near-fainting or fainting (syncope)
* Shortness of breath
* Chest pains
* Disturbed sleep
* Confusion or memory impairment
* Easily tiring during physical activity
When a slow heart rate is normal
A resting heart rate slower than 60 beats a minute may be normal for
some people, particularly for healthy, young adults and trained
athletes. In these cases, bradycardia isn't considered a health problem.
When to see a doctor
A number of conditions can cause signs and symptoms of bradycardia. It's
important to get a prompt, accurate diagnosis and appropriate care. See
your doctor if you or your child experiences any bradycardia symptoms.
If you faint, have difficulty breathing or have chest pain lasting more
than a few minutes, get emergency care or call 911 or your local
emergency number. Seek emergency care for anyone experiencing these
Bradycardia is caused by something that disrupts the normal electrical
impulses controlling the rate of your heart's pumping action. Many
things can cause or contribute to problems with your heart's electrical
* Degeneration of heart tissue related to aging
* Damage to heart tissues from heart disease or heart attack
* High blood pressure (hypertension)
* Heart disorder present at birth (congenital heart defect)
* Infection of heart tissue (myocarditis)
* A complication of heart surgery
* Underactive thyroid gland (hypothyroidism)
* Imbalance of electrolytes, mineral-related substances necessary for conducting electrical impulses
* Obstructive sleep apnea, the repeated disruption of breathing during sleep
* Inflammatory disease, such as rheumatic fever or lupus
* Hemochromatosis, the buildup of iron in organs
* Medications, including some drugs for other heart rhythm disorders, high blood pressure and psychosis
Electrical circuitry of the heart
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 a natural pacemaker — the sinus node — located in the
right atrium. The sinus node produces electrical impulses that initiate
From the sinus node, electrical impulses travel across the atria,
causing the atria to contract and pump blood into the ventricles. The
electrical impulses then arrive at a cluster of cells called the
atrioventricular node (AV node).
The AV node transmits the signal to a specialized collection of cells
called the bundle of His. These cells transmit the signal down a left
branch serving the left ventricle and a right branch serving the right
ventricle. When the electrical impulse travels down these branches, the
ventricles contract and pump blood — the right ventricle sending
oxygen-poor blood to the lungs and the left ventricle sending
oxygen-rich blood to the body.
Bradycardia occurs when electrical signals slow down or are blocked.
Sinus node dysfunction
Bradycardia often starts in the sinus node. A slow heart rate may occur because the sinus node:
* Discharges electrical impulses at a slower than normal rate
* Pauses, or fails to discharge at a regular rate
* Discharges an electrical impulse that's blocked before causing the atria to contract
In some people the sinus node dysfunction may result in alternating slow
and fast heart rates (bradycardia-tachycardia syndrome).
Heart block (atrioventricular block)
Bradycardia also may occur because electrical signals transmitted
through the atria aren't transmitted to the ventricles (heart block, or
atrioventricular block). The disruption of the electrical signal may
occur in the AV node, the bundle of His, or somewhere along the left and
right branches that transmit electrical signals to the ventricles.
Heart blocks are classified based on the degree to which signals from
the atria reach your heart's main pumping chambers (ventricles).
* First-degree heart block. In the mildest form of heart block, all
electrical signals from the atria reach the ventricles, but the signal
is slowed down slightly. First-degree heart block rarely causes symptoms
and usually needs no treatment if there's no other abnormality in
electrical signal conduction.
* Second-degree heart block. In second-degree heart block, not all
electrical signals reach the ventricles. Some beats are "dropped,"
resulting in a slower and sometimes irregular rhythm.
* Third-degree (complete) heart block. In third-degree heart block,
none of the electrical impulses from the atria reaches the ventricles.
When this happens, the bundle of His or other tissues of the ventricles
function as a substitute pacemaker for the ventricles. These substitutes
result in slow and sometimes unreliable electrical impulses to control
the beat of the ventricles.
* Bundle branch block. The interruption of an electrical signal
somewhere in the right or left bundle branches — near the end of the
pathway for electrical impulses — is called a bundle branch block. The
seriousness of bundle branch block depends on whether both branches are
affected, the presence of other types of heart block and the degree of
damage to heart tissue.
Read this article on Mayoclinic.com.
Expand Arrow DownComplications
Complications of untreated bradycardia vary depending on how slow the
heart rate is, where the electrical conduction problem occurs and what
kind of damage may be present in heart tissue. If bradycardia is
significant enough to cause symptoms, possible complications of the slow
heart rate may include:
* Frequent fainting spells
* Inability of the heart to pump enough blood (heart failure)
* Sudden cardiac arrest or sudden death
A key risk factor for bradycardia is age. The degeneration of tissue
associated with many cases of bradycardia is more common in older
Risk factors related to heart disease
Bradycardia is often associated with damage to heart tissue from some
type of heart disease. Therefore, factors that increase your risk of
heart disease may also increase the risk of bradycardia. Lifestyle
changes or medical treatment may decrease the risk of heart disease
associated with the following factors:
* High blood pressure
* High cholesterol
* Heavy alcohol consumption
* Use of recreational drugs
* Psychological stress or anxiety
Preparing for your appointment
Whether you first see your family doctor or get emergency care, you'll
likely be referred to a heart specialist (cardiologist) for one or more
appointments for a complete diagnostic assessment.
If possible, take along a family member or friend who can give some
moral support and help you keep track of new information. Because there
may be a lot of ground to cover, it will be helpful to prepare as much
What you can do
Make a list ahead of time that you can share with your doctor. Your list should include:
* Symptoms you've experienced, including any that may seem unrelated to your heart
* Key personal information, including any major stresses or recent life changes
* Medications, including vitamins or supplements
* Questions to ask your doctor
List your questions from most important to least important in case time runs out. Basic questions to ask your doctor include:
* What is likely causing my slow heart rate?
* What kinds of tests do I need?
* What is the best course of action?
* What kind of risks does my heart condition create?
* How will we monitor my heart?
* How often will I need follow-up appointments?
* How will other conditions I have or medications I take affect my heart problem?
* Do I need to restrict my activities?
* Are there any brochures or other printed material that I can take home with me? What Web sites do you recommend visiting?
In addition to the questions you've prepared to ask your doctor, don't
hesitate to ask questions during your appointment at any time you don't
What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to
answer them may reserve time to go over any points you want to spend
more time on. Your doctor may ask:
* When did you first begin experiencing symptoms?
* Have you experienced fainting spells in the past?
* Does anything, such as exercise, seem to worsen symptoms?
* Do you smoke?
* Are you being treated for heart disease, high blood pressure, high
cholesterol or other conditions that may affect your circulatory
* What medications do you take for these conditions, and do you take them as prescribed?
Tests and diagnosis
Your doctor will 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.
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
* 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 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 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 of the
preceding few minutes and following few minutes is recorded. This
permits your doctor to determine your heart rhythm at the time of your
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 tests 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 induce a fainting spell and enable your
doctor to establish a correlation between your heart rate and fainting
* 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
Treatments and drugs
Treatment for bradycardia depends on the type of electrical conduction
problem, the severity of symptoms, and the cause of your slow heart
Treating underlying disorders
If an underlying disorder, such as hypothyroidism or obstructive sleep
apnea, is causing bradycardia, treatment of the disorder may correct
Change in medications
A number of medications, including some to treat other heart conditions,
can cause bradycardia. Your doctor will check what medications you're
taking and may recommend alternative treatments. Changing drugs or
lowering dosages may correct problems with a slow heart rate. When
alternative treatments are not possible and symptoms require treatment, a
pacemaker is necessary.
A pacemaker is a battery-operated device about the size of a cell phone
that's implanted under your collarbone. Wires from the device are
threaded through veins and into your heart. Electrodes at the end of the
wires are attached to heart tissues. The pacemaker monitors your heart
rate and generates electrical impulses as necessary to maintain an
Most pacemakers also capture and record information that your
cardiologist can use to monitor your heart. You will have regularly
scheduled follow-up appointments to check your heart and ensure the
proper function of your pacemaker.
The most effective way to prevent bradycardia is to reduce your risk of
developing heart disease. If you already have heart disease, monitor it
and follow your treatment plan to lower your risk of bradycardia.
Prevent heart disease
Treat or eliminate risk factors that may lead to heart disease. Take the following steps:
* 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 consume alcohol, drink
in moderation. For some conditions it is recommended that you completely
avoid alcohol. Ask your doctor for advice specific to your condition.
If you can't control your alcohol consumption, talk to your doctor about
a program to quit drinking and manage other behaviors related to
* Don't use recreational drugs. Talk to your doctor about an
appropriate program for you if you need help ending recreational drug
* 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.
Monitor and treat existing heart disease
If you already have heart disease, there are steps you can take to lower
your risk of developing bradycardia or another heart rhythm disorder:
* Follow the plan. Be sure you understand your treatment plan, and take all medications as prescribed.
* Report changes immediately. If your symptoms change or get worse
or you develop new symptoms, tell your doctor immediately.