Third Degree Atrioventricular Block

ExitCare ImageThird degree atrioventricular block is a type of heart block. The heartbeat is a coordinated contraction between the upper and lower chambers of the heart. This coordinated contraction happens because of an electrical impulse that is sent from the upper chambers of the heart to the lower chambers of the heart. Normally, this electrical impulse is transmitted without problems. In third degree heart block, also known as complete heart block, the heart's electrical impulse does not pass from the upper chambers of the heart to the lower chambers of the heart. The heart's lower chambers beat independently from the upper chambers. This causes the heart to beat at a very slow rate and does not allow the heart to pump blood very well. Third degree heart block is serious and can result in death.


  • Heart attack. A heart attack can cause scarring which can damage the heart's electrical system.

  • Aging can cause degeneration and scarring of the heart's electrical system.

  • Heart medication such as beta blockers or calcium channel blockers. These kinds of medications can slow the heart rate. They can affect the electrical impulse of the heart if the dosage is too high.

  • Open heart surgery can affect the electrical pathway of the heart.


  • Symptoms may include the following:

  • Fainting or near fainting.

  • Feeling dizzy or lightheaded.

  • Difficulty breathing or shortness or breath.

  • Chest pain.

  • Fatigue.

  • Swelling of the lower legs.


Third degree heart block can be diagnosed by:

  • An electrocardiogram (EKG). An EKG is a tracing of the heartbeat and can show a 3rd degree heart block.

  • Electrophysiology (EP) study. This is a procedure which tests the electrical pathway of your heart. This type of test is done by a specialist who places a catheter (long thin tube) in your heart. The catheter is used to study your heart and record your heart's electrical signals.


  • 3rd degree heart block requires hospitalization and continuous heart rhythm monitoring.

  • Most people with 3rd degree heart block will need a permanent pacemaker to help your heart beat.

  • If a permanent pacemaker cannot be placed immediately, a temporary pacemaker may be needed.

  • Heart medications such beta blockers or calcium channel blockers can slow the heart rate. Your caregiver may need to adjust your heart medication if this is the cause of your heart block.


  • You have unexplained fatigue.

  • You feel lightheaded.

  • You feel faint.

  • You feel your heart skipping beats or your heart beats very fast.


  • You have severe chest pain, especially if the pain is crushing or pressure-like and spreads to the arms, back, neck, or jaw. THIS IS AN EMERGENCY. Do not wait to see if the pain will go away. Get medical help at once. Call your local emergency services (911 in the U.S.). DO NOT drive yourself to the hospital.

  • You notice increasing shortness of breath during rest, sleeping, or with activity.

  • You "black out" or faint.

  • You have swelling in your lower legs.


  • Understand these instructions.

  • Will watch your condition.

  • Will get help right away if you are not doing well or get worse.