Complete Heart Block (Third-degree Atrioventricular (AV) Block)

Complete Heart Block (Third-degree Atrioventricular (AV) Block)

Heart block or AV Bundle Block is a disturbance in the heart’s electrical system. In heart block, your heart beats irregularly and very slowly, possibly stopping for about 20 seconds at a time. This can be because of an obstruction, disruption or delay along the pathway the electrical impulses travel through to make your heart beat.  This condition can be due to damage or an injury to the heart valves or heart muscle. While heart block itself does not generally require direct treatment, the underlying related health conditions do.

Normally, heart block causes palpitations, lightheadedness and fainting. There can be chest pain too. Depending on its severity, heart block can be dangerous. For example, a complete heart block (third-degree heart block) can make pre-existing conditions like heart failure even worse. It may lead to unconsciousness and even sudden cardiac arrest.

What is Heart Block?

Heart block is a disruption of the heart’s electrical impulses. A healthy person’s heart beats at around 60 – 100 times in a minute. A heartbeat means one contraction of the heart muscle that pushes blood around our body. Typically, heart muscle contractions are controlled by electrical impulses that travel from the heart’s upper chambers or the atria to the lower chambers or the ventricles.

A partial heart block can occur when the electrical impulses are delayed or stopped partially, preventing regular beats of your heart. A complete heart block happens when the electrical signals are disrupted or stopped completely. This may result in a drop in your heartbeat to approximately 40 times a minute. Even changes to impulses for just a fraction of second can lead to heart block.

At times, a heart block makes it hard for our heart to pump blood through our circulatory system properly. This results in a reduced supply of oxygen to our muscles and organs (including the brain), impairing their functions.

Types of Heart Block

Heart block is of three types, namely:

  1. First-degree heart block: Minor heartbeat disturbances like skipped heartbeats. First-degree heart block is not a very serious type of heart block and usually does not need treatment.
  2. Second-degree heart block: This happens when some electrical signals do not reach your heart, causing skipped or dropped heartbeats. You may feel giddy, and may also need a pacemaker. As the atrial impulse does not reach the ventricles, the ventricle may not contract.
  3. Complete heart block or third-degree heart block: This happens when electrical signals do not travel between the lower and upper chambers of our heart. Complete heart block is very common in heart disease patients. Individuals with complete heart block have a serious risk of a heart attack without a pacemaker.

Complete Heart Block

Complete heart block may result from the damage of the atrioventricular node (AV node) during surgery. However, sometimes it may also occur spontaneously, without surgery. To restore a normal heart rhythm or rate, an artificial pacemaker is needed.


Many people with complete heart block are already suffering from an underlying heart condition, such as cardiomyopathy, congenital heart disease or coronary heart disease. Increasing age may also be a cause,  as electrical pathways in our heart ages too. Some medications and electrolyte imbalances may also cause complete heart block.


The signs and symptoms of complete heart block include:

  • Chest pain
  • Breathlessness
  • Pre-syncope (Feeling that you will faint)
  • Syncope (Fainting) – causing someone to collapse completely
  • Fatigue or extreme tiredness
  • Having a slow heartbeat (bradycardia)
  • Palpitations (feeling of fluttering, pounding or skipping in the chest)

All the above signs and symptoms can be life-threatening. Please call for an ambulance or call your local medical emergency service provider if you experience these symptoms.


Your primary care doctor might refer you to a heart specialist (cardiologist) for a complete cardiac evaluation. The cardiologist may begin by acquiring your past medical records, including records of any heart tests you may have undergone.

The heart specialist may ask you a few questions about your general health, diet as well as activity levels including your family medical history. The specialist may also want to know about any over-the-counter or prescription medications you take and whether you consume alcohol, use drugs or smoke.

You will go through a comprehensive physical examination during which, the heart specialist will listen to your heart. In addition, he or she will check your pulse to measure your heart rate or heart rhythm. The specialist may also check you for signs of heart failure like fluid retention in the feet or legs.

Heart block can be diagnosed using a test called, Electrocardiogram (ECG or EKG). ECG effectively records your heart’s electrical activity. This test produces a graph that demonstrates the heart rhythm and heart rate including the timing of electrical signals as they move through your heart. 

If your doctor decides to check electrical signals over a long period of time, he or she may recommend wearing a Holter Monitor, a small, portable ECG machine, for 24 to 48 hours. Holter monitor enables continuous recording of your heart’s electrical activity as you go about performing your daily activities

This monitor helps detects problems that may not show up on a resting ECG that records only for a few seconds.


Complete heart block is a medical emergency. Depending on the severity of your problem, the heart specialist may recommend medication or implanting a pacemaker.


The doctor may prescribe some anti-arrhythmic medications that can change the electrical signals in your heart and help prevent the disturbances in the electrical system of your heart.


Depending on the severity, your doctor may recommend implanting a compact device called pacemaker in your chest. A minor surgery is performed to implant this small device. The pacemaker has two wires that connect to your heart’s right side. The pacemaker works as a backup electrical system for your heart. It reminds your heart to beat at a normal rate if it stops or slows down.


Complete heart block is a serious medical emergency, and getting it treated at the right time is important. Also, since treating complete heart block needs an expert heart specialist, find out if you have specialists with quality training and experience to treat heart blocks. The more complex your medical condition, the greater this matters.

Knowing the signs and making lifestyle changes can surely help. Take action now! Enroll in our comprehensive Healthy Heart Program to keep your heart healthy.

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