First-degree atrioventricular (AV) block is a condition that causes the electrical signals that travel from the heart’s upper chambers (atria) to its lower chambers (ventricles) to move too slowly. As a result, the heart may beat more slowly than normal.

First-degree AV block is the least serious type of heart block. Second- and third-degree AV blocks are more serious. First-degree AV block can increase your risk of developing a type of irregular heartbeat called atrial fibrillation. It is also associated with a higher risk of needing a pacemaker in the future.

What are the causes?

This condition may be caused by:

  • Any condition that damages the electrical pathway that controls the heart’s rate and rhythm, such as a heart attack.

  • Overstimulation of the nerve that slows down the heart rate (vagus nerve). This cause is common among well-conditioned athletes.

  • Some medicines that slow down the heart rate, such as beta blockers or calcium channel blockers.

  • Surgery that damages the heart.

Some people are born with this condition (congenital heart block), but most people develop it over time.

What increases the risk?

The risk for this condition increases with age. You are also more likely to develop this condition if you have:

  • A history of heart attack.

  • Heart failure.

  • Coronary heart disease.

  • Inflammation of heart muscle (myocarditis).

  • Disease of heart muscle (cardiomyopathy).

  • Infection of the heart valves (endocarditis).

  • Infections or diseases that affect the heart. These include:

    • Lyme disease.

    • Sarcoidosis.

    • Hemochromatosis.

    • Rheumatic fever.

    • Certain muscle disorders.

Babies are more likely to be born with heart block if:

  • The baby’s mother has an autoimmune disease, such as lupus.

  • The baby is born with a heart defect that affects the heart’s structure.

  • A parent was born with a heart defect.

What are the signs or symptoms?

This condition usually does not cause any symptoms.

How is this diagnosed?

This condition may be diagnosed based on:

  • A physical exam.

  • Your medical history.

  • A measurement of your pulse or heartbeat.

  • Tests. These may include:

    • An electrocardiogram (ECG). This checks for problems with electrical activity in the heart.

    • Ambulatory cardiac monitoring. This is a portable ECG that you wear. It checks your heart’s rhythm.

    • An electrophysiology (EP) study. Long, thin tubes (catheters) are placed in your heart. The catheters give information about your heart’s electrical signals.

How is this treated?

Usually, treatment is not needed for this condition. In some cases, treatment involves:

  • Treating an underlying condition, such as heart disease.

  • Changing or stopping any heart medicines that can cause heart block.

Follow these instructions at home:

Alcohol use

  • Do not drink alcohol if:

    • Your health care provider tells you not to drink.

    • You are pregnant, may be pregnant, or are planning to become pregnant.

  • If you drink alcohol:

    • Limit how much you use to:

      • 0–1 drink a day for women.

      • 0–2 drinks a day for men.

    • Be aware of how much alcohol is in your drink. In the U.S., one drink equals one 12 oz bottle of beer (355 mL), one 5 oz glass of wine (148 mL), or one 1½ oz glass of hard liquor (44 mL).

General instructions

  • Take over-the-counter and prescription medicines only as told by your health care provider.

  • Follow your health care provider’s recommendations to help reduce your risk of heart disease. These may include:

    • Exercising at least 30 minutes on 5 or more days each week (150 minutes). Ask your health care provider what type of exercise is safe for you.

    • Eating a heart-healthy diet with fruits and vegetables, whole grains, low-fat dairy products, and lean proteins like poultry and eggs. Your health care provider or dietitian can help you make healthy choices.

    • Maintaining a healthy weight.

  • Do not use any products that contain nicotine or tobacco, such as cigarettes, e-cigarettes, and chewing tobacco. If you need help quitting, ask your health care provider.

  • Keep all follow-up visits as told by your health care provider. This is important.

Where to find more information

  • American Heart Association:

  • National Heart, Lung, and Blood Institute:

Contact a health care provider if you:

  • Feel like your heart is skipping beats.

  • Feel more tired than normal.

  • Have swelling in your hands, feet, or lower legs.

Get help right away if you:

  • Have symptoms that change or get worse.

  • Develop new symptoms.

  • Have chest pain, especially if the pain:

    • Feels like crushing or pressure.

    • Spreads to your arms, back, neck, or jaw.

  • Feel short of breath.

  • Feel light-headed or weak.

  • Faint.

These symptoms may represent a serious problem that is an emergency. Do not wait to see if the symptoms will go away. Get medical help right away. Call your local emergency services (911 in the U.S.). Do not drive yourself to the hospital.


  • First-degree atrioventricular (AV) block is the least serious type of heart block. In this condition, the signals that control heart rate move too slowly. As a result, the heart may beat more slowly than normal.

  • Usually, treatment is not needed for this condition. In some cases, you may need to change or stop medicines that may be making the condition worse.

  • Healthy lifestyle choices such as exercising regularly, eating a healthy diet, and limiting alcohol are good for your heart.

This information is not intended to replace advice given to you by your health care provider. Make sure you discuss any questions you have with your health care provider.