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Heart Block

The beating of your heart is controlled by electrical signals that tell the heart muscle when to contract.

Heart block occurs when there is interference with the signals that usually move from the top chambers of your heart (the atria) to the bottom chambers (the ventricles). When those signals aren't able to move properly from the atria to the ventricles, they are unable to tell the ventricles to contract and pump blood as they should.

Heart block categories

Heart block has three stages:

  • First-degree heart block is the least severe and may not require any treatment. However, you may be at greater risk of developing an arrhythmia (irregular heartbeat) called atrial fibrillation.
  • Second-degree heart block is when the signals between the atria and ventricles are slower than in first-degree heart block.
  • Third-degree heart block is the most severe. Electrical signals don't travel at all, preventing your heart from pumping blood through your body. This can lead to cardiac arrest and death. You may require lifelong treatment with a pacemaker to keep your heart rhythm steady.


Symptoms depend on the degree of heart block you have.

  • First-degree heart block usually has no bothersome symptoms.
  • Second-degree heart block can cause dizziness, fainting, chest pain, fatigue, shortness of breath and nausea.
  • Third-degree heart block can cause extreme fatigue, irregular heartbeats, dizziness, fainting and cardiac arrest.

Risk factors

Your risk of developing heart block increases if you:

  • Have congenital heart defects
  • Were born to a mother who has autoimmune disease
  • Have recently had a heart attack or heart surgery
  • Have coronary artery disease
  • Have rheumatic fever
  • Have heart muscle diseases or inflammation
  • Are taking medications such as beta blockers, digitalis and calcium channel blockers
  • Have an overactive vagus nerve

Diagnosis & treatment

 Your physician will evaluate you to determine whether you have heart block by considering:

  • Your overall health
  • Family history of heart disease
  • Medications you are taking
  • Lifestyle choices
  • Your description of symptoms
  • A physical exam
  • An electrocardiogram (ECG), which records your heart's electrical impulses
  • Testing with a Holter event monitor that track your heart for a period of time
  • An electrophysiology study, which uses wires inserted into your heart to track rhythm changes

Your treatment depends on the type of heart block you have.

  • First-degree heart block often needs no treatment
  • Second-degree heart block may involve a pacemaker
  • Third-degree heart block requires a pacemaker for the rest of your life

Preventing heart block

Heart block can be prevented in some cases. If you are pregnant and have autoimmune disease, your fetus is at greater risk of developing heart block. Tests can be run during your pregnancy to determine whether your baby needs medication to reduce this risk.

A healthy lifestyle can also help prevent heart block and improve your overall heart health. Exercise, eat a nutritious diet and don't smoke (or quit if you do smoke).

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