Heart block (patient information)

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 * Associate Editor(s)-In-Chief: Varun Kumar, M.B.B.S.

Overview
Heart block is a problem that occurs with the heart's electrical system. This system controls the rate and rhythm of heartbeats. ("Rate" refers to the number of times your heart beats in a minute. "Rhythm" refers to the pattern of regular or irregular pulses produced when the heart beats over time.)

With each heartbeat, an electrical signal spreads across the heart from the upper to the lower chambers. As it travels, the signal causes the heart to contract and pump blood. This process repeats with each new heartbeat.

Heart block occurs if the electrical signal is slowed or disrupted as it moves from the upper to the lower chambers of the heart.

What are the symptoms of heart block
Symptoms depend on the type of heart block you have. First-degree heart block rarely causes symptoms.

Symptoms of second- and third-degree heart block include:


 * Fainting
 * Dizziness or light-headedness
 * Fatigue (tiredness)
 * Shortness of breath
 * Chest pain

What causes heart block?
Heart block has many causes. Some people are born with the disorder (congenital), while others develop it during their lifetimes (acquired).

Congenital Heart Block

 * One form of congenital heart block occurs in babies whose mothers have autoimmune diseases, such as lupus. People who have these diseases make proteins called antibodies that attack and damage the body's tissues or cells.


 * In pregnant women, antibodies can cross the placenta. (The placenta is the organ that attaches the umbilical cord to the mother's womb.) These proteins can damage the baby's heart and lead to congenital heart block.


 * Congenital heart defects also may cause congenital heart block. These defects are problems with the heart's structure that are present at birth. Often, doctors don't know what causes these defects.

Acquired Heart Block
Many factors can cause acquired heart block. Examples include:


 * Damage to the heart from a heart attack. This is the most common cause of acquired heart block.
 * Coronary heart disease, also called coronary artery disease.
 * Myocarditis, or inflammation of the heart muscle.
 * Heart failure.
 * Rheumatic fever.
 * Cardiomyopathy, or heart muscle diseases.
 * sarcoidosis
 * Degenerative muscle disorders Lev's disease and Lenegre's disease.
 * Certain types of surgery also may damage the heart's electrical system and lead to heart block.
 * Exposure to toxic substances and taking certain medicines—including digitalis, beta blockers, and calcium channel blockers—also may cause heart block. Doctors closely watch people who are taking these medicines for signs of problems.
 * Some types of heart block have been linked to genetic mutations (changes in the genes).
 * An overly active vagus nerve also can cause heart block. You have one vagus nerve on each side of your body. These nerves run from your brain stem all the way to your abdomen. Activity in the vagus nerve slows the heart rate.

In some cases, acquired heart block may go away if the factor causing it is treated or resolved. For example, heart block that occurs after a heart attack or surgery may go away during recovery.

Also, if a medicine is causing heart block, the disorder may go away if the medicine is stopped or the dosage is lowered. Always talk with your doctor before you change the way you take your medicines.

Who is at the highest risk?
The risk factors for congenital and acquired heart block are different.

Congenital Heart Block

 * If a pregnant woman has an autoimmune disease, such as lupus, her fetus is at risk for heart block.


 * Autoimmune diseases can cause the body to make proteins called antibodies that can cross the placenta. (The placenta is the organ that attaches the umbilical cord to the mother's womb.) These antibodies may damage the baby's heart and lead to congenital heart block.


 * Congenital heart defects also may result in congenital heart block. These defects are problems with the heart's structure that are present at birth. Most of the time, doctors don't know what causes these defects.


 * Heredity may play a role in certain heart defects. For example, a parent who has a congenital heart defect may be more likely than other people to have a child with the condition.

Acquired Heart Block

 * Acquired heart block can occur in people of any age. However, most types of the disorder are more common in older people. This is because many of the risk factors are more common in older people.


 * People who have a history of heart disease or heart attacks are more likely to have heart block. Examples of heart disease that can lead to heart block include heart failure, coronary heart disease, and cardiomyopathy (heart muscle diseases).


 * Other diseases also may raise the risk of heart block. These include sarcoidosis and the degenerative muscle disorders Lev's disease and Lenegre's disease.


 * Exposure to toxic substances or taking certain medicines, such as digitalis, also can raise your risk of heart block.


 * Well-trained athletes and young people are at higher risk for first-degree heart block caused by an overly active vagus nerve. You have one vagus nerve on each side of your body. These nerves run from your brain stem all the way to your abdomen. Activity in the vagus nerve slows the heart rate.

When to seek urgent medical care?
If you are experiencing the above mentioned symptoms for the first time or are severe, call 9–1–1 or have someone drive you to the hospital emergency room. If you have milder symptoms, talk with your doctor right away to find out whether you need prompt treatment.

Diagnosis
Heart block may be diagnosed as part of a routine doctor's visit or during an emergency situation. (Third-degree heart block often is an emergency.) Your doctor will diagnose heart block based on your family and medical histories, a physical exam, and results from tests such as:
 * EKG (Electrocardiogram): Doctors usually use a test called an EKG (electrocardiogram) to help diagnose heart block. An EKG shows how fast the heart is beating and its rhythm (steady or irregular). The test also records the strength and timing of electrical signals as they pass through each part of the heart.
 * Holter Monitors: A Holter monitor records the heart's electrical signals for a full 24- or 48-hour period. You wear one while you do your normal daily activities. This allows the monitor to record your heart for a longer time than a standard EKG.
 * Event Monitors: An event monitor is similar to a Holter monitor. You wear an event monitor while doing your normal activities. However, an event monitor only records your heart's electrical activity at certain times while you're wearing it.
 * Electrophysiology Study: For some cases of heart block, doctors may do electrophysiology studies (EPS). During this test, a thin, flexible wire is passed through a vein in your groin (upper thigh) or arm to your heart. The wire records your heart's electrical signals.

Treatment options
Treatment depends on the type of heart block you have. First-degree heart block usually needs no treatment.

If you have second-degree heart block, you may need a pacemaker. A pacemaker is a small device that's placed under the skin of your chest or abdomen. This device uses electrical pulses to prompt the heart to beat at a normal rate.

If you have third-degree heart block, you will need a pacemaker. In an emergency, a temporary pacemaker may be used until you can get a long-term device. Most people who have third-degree heart block need pacemakers for the rest of their lives.

Some people who have third-degree congenital heart block don't need a pacemaker for many years. Others may need a pacemaker at a young age or during infancy.

If a pregnant woman has an autoimmune disease, such as lupus, her fetus is at risk for heart block. If heart block is detected in a fetus, the mother may be given medicine to reduce the fetus' risk of developing serious heart block.

Sometimes acquired heart block goes away if the factor causing it is treated or resolved. For example, heart block that occurs after a heart attack or surgery may go away during recovery.

Also, if a medicine is causing heart block, the condition may go away if the medicine is stopped or the dosage is lowered. Always talk with your doctor before you change the way you take your medicines.

Where to find medical care for heart block?
Directions to Hospitals Treating Heart Block

What to expect (Outlook/Prognosis)?

 * First-degree heart block may not cause any symptoms or require treatment.
 * If you have second-degree heart block that doesn't require a pacemaker, talk with your doctor about keeping your heart healthy. Your doctor will tell you whether you need ongoing care for your condition.
 * People who have third-degree heart block and some people who have second-degree heart block need pacemakers. This device uses electrical pulses to prompt the heart to beat at a normal rate.
 * If you have a pacemaker, you should take special care to avoid things that may interfere with it. Avoid close or prolonged contact with electrical devices and devices that have strong magnetic fields. These objects can keep your pacemaker from working properly.
 * Let all of your doctors, dentists, and medical technicians know that you have a pacemaker. You also should notify airport screeners.
 * Your doctor can give you a card that states what kind of pacemaker you have. Carry this card in your wallet. You may want to consider wearing a medical ID bracelet or necklace that states that you have a pacemaker.
 * Certain medical procedures can disrupt pacemakers. Examples include MRI (magnetic resonance imaging), electrocauterization during surgery, and shock-wave lithotripsy to get rid of kidney stones.
 * Your doctor may need to check your pacemaker several times a year to make sure it's working well. Some pacemakers must be checked in the doctor's office, but others can be checked over the phone.
 * Ask your doctor about what types of physical activity are safe for you. A pacemaker usually won't limit you from doing sports and physical activity. But you may need to avoid full-contact sports, such as football, that can damage the pacemaker.

Possible complications

 * Arrhythmias
 * Heart failure
 * Stroke