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slow heartbeat

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Electrocardiogram of a normal heart rhythm

Alternative Names

A slow heartbeat, or bradycardia, is defined as a heart rate that is slower than normal. Normally, the heart beats at least 60 times per minute in adults. There are other age-related heart rates that are considered "normal" in children.

What is going on in the body?
When a person is at rest, the heart normally beats at a rate that is within a fairly narrow range. This range is usually 60 to 100 beats per minute in adults and slightly faster in children. With certain conditions, however, the heart rate may decrease below the "normal" level.

What are the signs and symptoms of the condition?
A person with a slow heartbeat may have no symptoms at all. When symptoms do occur, they may include: What are the causes and risks of the condition?
There are many possible causes of a slow heartbeat, including: Other causes are also possible. Sometimes no cause can be found.

What can be done to prevent the condition?
Most cases cannot be prevented. Medications should be taken exactly as prescribed. The doses should not exceed what is prescribed by the doctor. Avoiding heroin could prevent cases due to heroin overdose.

How is the condition diagnosed?
The speed of the heartbeat can usually be measured by checking the pulse or listening to the heartbeat with an instrument called a stethoscope.

The doctor will also need to figure out the cause of a slow heartbeat. Diagnosis of the cause starts with a history and physical examination. This may be all that is needed in some cases. In other cases, further tests may be needed.

For example, an electrocardiogram, or ECG, can help diagnose irregular heartbeats and heart attacks. A series of blood tests known as thyroid function tests can be used to diagnose low thyroid levels. A drug test of the urine or blood can be used to diagnose heroin use. A special x-ray test, called a cranial CT scan, may be done to look for head injuries or brain damage.

What are the long-term effects of the condition?
If the heart beats too slowly, it may not be able to pump blood well enough to keep a person alive. Most long-term effects are related to the cause. For example, cases due to hypothyroidism often go away quickly with treatment and there are no long-term effects. Cases due to an arrhythmia or shock sometimes result in death. head injuries and brain damage may cause permanent disabilities.

What are the risks to others?
A slow heartbeat is not contagious and poses no risks to others.

What are the treatments for the condition?
Treatment is directed at the cause. For example, a person with hypothyroidism is given thyroid hormone pills. Someone with arrhythmias may need a pacemaker, which is a device inserted under the skin to control the heart rate using electricity. A person with Head injuries may need surgery or medications to decrease the pressure inside the skull.

What are the side effects of the treatments?
Side effects are related to the treatments. For example, if the dose of thyroid medication is too high, the person may develop a heart rate that is too fast. Insertion of a pacemaker requires minor surgery, which may result in bleeding or infections.

What happens after treatment for the condition?
What happens after treatment depends on the cause of the slow heart rate. A person who has a slow heartbeat because he or she is a good athlete needs no treatment. An individual taking thyroid or blood pressure medications usually needs further monitoring and treatment for life. Someone with head injuries or brain damage may need help with regular activities.

How is the condition monitored?
The speed of the heartbeat can be monitored closely if needed. This is done with special equipment that measures the electrical activity in the heart. Other monitoring is related to the cause. For example, those with a heart attack may need close monitoring in the intensive care unit.

Author: Adam Brochert, MD
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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