Third degree AV block (patient information)

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Varun Kumar, M.B.B.S. Soroush Seifirad, M.D.[2] Qasim Khurshid, M.B.B.S.

Heart block

For third-degree AV block specific info please scroll down.

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:

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 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.
  • 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.
  • 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.

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.

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.

Treatment options

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.

Medications to avoid

Patients diagnosed with second-degree atrioventricular block and third-degree atrioventricular block should avoid using the following medications:

  • Amiodarone
  • Propafenone
  • Timolol
    If you have been diagnosed with second-degree atrioventricular block and third-degree atrioventricular block, consult your physician before starting or stopping any of these medications.


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

Third degree AV block

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.
Third-degree atrioventricular block (AV block) also called complete heart block is a medical condition in which the nerve impulse generated in the sinoatrial node (SA node) in the atrium of the heart can not propagate to the ventricles.

What are the symptoms of Third degree AV block?

People with third-degree AV block typically experience severe bradycardia (an abnormally low measured heart rate), hypotension (decreased blood pressure), and at times, hemodynamic instability and syncope. They may faint, or complain of dizziness or simply feel week.

What causes Third degree AV block?

Third-degree atrioventricular block (AV block) is a medical condition in which the nerve impulse generated in the sinoatrial node (SA node) in the atrium of the heart can not propagate to the ventricles.

Many conditions can cause third-degree heart block, but the most common cause is coronary ischemia. Progressive degeneration of the electrical conduction system of the heart can lead to third-degree heart block. This may be preceded by first-degree AV block, second-degree AV block, bundle branch block, or bifascicular block. In addition, acute myocardial infarction may present with third-degree AV block.

An inferior wall myocardial infarction may cause damage to the AV node, causing third-degree heart block. In this case, the damage is usually transitory. Studies have shown that third-degree heart block in the setting of an inferior wall myocardial infarction typically resolves within 2 weeks. The escape rhythm typically originates in the AV junction, producing a narrow complex escape rhythm.

An anterior wall myocardial infarction may damage the distal conduction system of the heart, causing third-degree heart block. This is typically extensive, permanent damage to the conduction system, necessitating a permanent pacemaker to be placed. The escape rhythm typically originates in the ventricles, producing a wide complex escape rhythm.

Third-degree heart block may also be congenital and has been linked to the presence of lupus in the mother. It is thought that maternal antibodies may cross the placenta and attack the heart tissue during gestation. The cause of congenital third-degree heart block in many patients is unknown. Studies suggest that the prevalence of congenital third-degree heart block is between 1 in 15,000 and 1 in 22,000 live births.

Hyperkalemia in those with previous cardiac disease and Lyme disease can also result in third-degree heart block.

Who is at highest risk?

Elderly, particularly those with ischemic heart disease, and patients with certain disorders such as Lyme disease are at increased risk of developing complete heart block (CHB).

Diagnosis

An electrocardiogram ( ECG) is used to diagnose CHB.

When to seek urgent medical care?

Any syncope, loss of consciousnesses in a patient with known risk factors of heart disease calls for urgent medical care.

Treatment options

Medications to avoid

Patients diagnosed with third degree AV block(except in patients with a functioning artificial pacemaker) should avoid using the following medications:


Where to find medical care for Third degree AV block?

Almost every emergency room can diagnose and refer the patients to the third parties who will make the decision for appropriate intervention. If a pacemaker is needed which is necessary for the majority of cases then a specialized cardiology/electrophysiology center is needed to place a duel chamber pacemaker.

Prevention

There is no direct preventive measurement for the development of complete heart block. All those general cardio-protective advises works here as well when there is no ischemia and atherosclerosis, CHB is pretty unlikely. When CHB developed, secondary prevention to decrease complications of CHB is warranted which includes placement of a dual chamber pacemaker to reshape normal heart electrical activity .As with other forms of heart block, secondary prevention may also include medicines to control blood pressure and atrial fibrillation, as well as lifestyle and dietary changes to reduce risk factors associated with heart attack and stroke.

What to expect (Outlook/Prognosis)?

The prognosis of patients with complete heart block is generally poor without therapy. Patients with 1st and 2nd degree heart block are usually asymptomatic.

Possible complications

  • Arrhythmias
  • Heart failure
  • Stroke
  • In acute complete heart block, patients are prone to the complications of sudden loss of consciousness such as fall, head trauma, hip fracture, and driving accident.


Sources

http://www.nhlbi.nih.gov/health/dci/Diseases/hb/hb_whatis.html


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