Heart Block Adult



Heart block is when signals that control the heartbeat are partly or fully blocked. This leads to slow or skipped heartbeats. It also makes it hard for the heart to pump blood. Heart block can range from mild to serious and life-threatening.

There are 3 types of heart block:

  • First-degree (mildest type)—The heart signals move more slowly from one heart node to another.
  • Second-degree—Signals from the upper to lower heart are blocked, off and on.
  • Third-degree, or complete (most serious)—The heart signals cannot pass from the upper to the lower heart at all. This needs care right away.
Anatomy of the Heart
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Heart block is caused by:

  • Underlying heart disease or certain heart defects
  • Certain medicines

Risk Factors

The risk of heart block increases with age. Other things that may raise the risk are:

  • History of heart disease, such as a heart attack, heart failure, valve problems, and endocarditis
  • An inherited heart defect
  • Conditions that affect the heart such as sarcoidosis, rheumatic fever, or Lyme disease
  • Medicines such as beta-blockers, calcium channel blockers, or digitalis



Symptoms of heart block may be:

  • Lightheadedness
  • Fainting
  • Chest pain
  • Problems breathing


Your doctor will ask about symptoms and past health. A physical exam will be done. A heart doctor may make the diagnosis.

Diagnosis is based on tests, such as:

  • ECG—tests electrical activity of the heart
  • Echocardiogram—imaging exam of the heart to look for structural heart disease



Treatment depends on the type of heart block. In general, treatment may not be needed for first-degree heart block.

If medicines are causing heart block, they will be stopped or changed.

Some second degree—and all third degree heart block—will need a pacemaker. A pacemaker is an implanted device to help the heart beat at a normal pace.

Underlying conditions will also need to be treated.


Some heart block cannot be prevented. For others, the risk may be lowered by:

  • Treating heart problems
  • A heart healthy lifestyle that includes:
    • Regular exercise
    • A diet low in animal fat and rich in lean proteins, vegetables, and fruit
    • Reducing stress
    • Not smoking
    • Limiting or not using alcohol and caffeine
  • Not using medicines that can cause heart block

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

Edits to original content made by Denver Health.

a (Atrioventricular Block—Adult; AV Block—Adult)


American Heart Association http://www.heart.org 

Heart Rhythm Society http://www.hrsonline.org 


Canadian Heart Rhythm Society http://www.chrsonline.ca 

Heart and Stroke Foundation of Canada http://www.heartandstroke.ca 


Atrioventricular (AV) conduction disorders. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/atrioventricular-av-conduction-disorders. Accessed September 14, 2021.

Atrioventricular block. Merck Manual Professional Version website. Available at: https://www.merckmanuals.com/professional/cardiovascular-disorders/arrhythmias-and-conduction-disorders/atrioventricular-block. Accessed September 14, 2021.

Bolourchi M, Silver ES, et al. Advanced heart block in children with Lyme disease. Pediatr Cardiol. 2019;40(3):513-517.

Heart block. Heart Rhythm Society website. Available at: https://upbeat.org/heart-rhythm-disorders/heart-block#axzz2OHs4EXZq. Accessed September 14, 2021.

Heart conduction disorders. American Heart Association website. Available at: https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/conduction-disorders. Accessed September 14, 2021.