Second-Degree Atrioventricular Block

Second-degree atrioventricular (AV) block is a condition that can cause the heart to miss beats. In this condition, the electrical signals that travel from the heart’s upper chambers (atria) to its lower chambers (ventricles) move too slowly or are interrupted. There are two types of second-degree AV block:

• Mobitz type 1 block. This type does not cause symptoms. It rarely requires treatment.

• Mobitz type 2 block. This type is more serious. It results in more missed beats and a very irregular heartbeat. It can lead to third-degree AV block, or complete heart block, meaning that no signal exists between the atria and ventricles. Mobitz type 2 is a dangerous condition that can lead to fainting or cardiac arrest. Mobitz type 2 block often requires a pacemaker.

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 or infection of the heart.

• 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.

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.

Symptoms of this condition include:

• Tiredness.

• Shortness of breath.

• Dizziness.

• Light-headedness.

• Fainting.

• Chest pain.

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 your 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.

Treatment for this condition depends on the type of block you have and how severe it is. Treatment may involve:

• Treating an underlying condition, such as heart disease.

• Changing or stopping any heart medicines that may have caused heart block.

• Having a permanent pacemaker placed in your chest. A pacemaker uses electrical pulses to help the heart beat normally. It is usually placed under the skin on your chest. You will likely need a pacemaker if you have Mobitz type 2 block.

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 for 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.