Arrhythmias
Atrioventricular block bradycardia
What is atrioventricular block bradycardia?
Atrioventricular block (AV block) is a type of heart block that causes an abnormally slow heartbeat (bradycardia).
Like other heart blocks, AV block is caused by a blockage in the heart’s electrical system – in this case in the atrioventricular (AV) node. However, unlike other heart blocks, AV block disrupts and slows the heart rate, resulting in bradycardia. For this reason, AV block is considered to be a type of arrhythmia.
Heart contractions: 3rd degree AV block vs normal
If you have AV block the electrical signals that normally travel from your sinoatrial (SA) node down through your AV node and then on to your ventricles are interrupted.
The interruption can cause your heart to skip beats and become bradycardic, and it doesn’t pump as effectively as a normal heart.
AV block is defined as first, second, or third degree, depending on how significant the conduction blockage is.
In first degree AV block, the least severe type, the electrical pulse is delayed but it still reaches your ventricles.
In second degree AV block, the electrical pulse is occasionally completely blocked. And in third degree, it is always blocked.
Third-degree AV block is usually considered to be a medical emergency. It has a serious impact on your heart’s ability to pump and can be life-threatening.
If you would like to learn more about a normal heartbeat take a look at Your heart: The basics.
What causes atrioventricular block?
Some people with AV block were born with it – this is called a congenital heart block – but for most people it develops with age; the AV node becomes sclerosed or scarred and this disrupts the heart’s conduction system.
To learn more about how your heart’s conduction pathways and how they work, take a look at Your heart’s electrical system.
Electrical signals: Atrioventricular block vs normal
Non-age-related damage to the heart’s conduction system might be caused by scarring from previous heart surgery, particularly aortic or mitral valve surgery, but most cases it’s the result of a heart attack.
Coronary artery disease, cardiomyopathy (heart muscle weakness or thickening), and heart valve disorders can all also cause AV block, as can any disorder that causes heart inflammation (myocarditis, for example).
Common causes of AV block include:
- Age: Age-related AV block is usually seen in people over 50
- Heart attack
- Scarring from a surgical procedure, typically one involving the aortic or mitral valve
- Congenital conditions
- Medications that are intended to slow your heart rate
What are the symptoms of atrioventricular block?
If you have first-degree AV block, you may not experience any symptoms and may not even be aware that you have it. However, if you have second- or third-degree block, you will experience symptoms, and in the case of third-degree, they are likely to be severe.
Here is a list of the common symptoms of second-degree AV block. If you experience these symptoms you should seek medical advice:
- Palpitations and a feeling of skipped heartbeats
- Shortness of breath
- Dizziness or fainting
The main symptom of third-degree AV block is losing consciousness. This is a medical emergency.
Third-degree AV block can cause cardiac arrest and requires immediate medical care.
If someone you know experiences this symptom you should immediately seek emergency medical assistance.
How is atrioventricular block treated?
Your doctor will determine the best course of treatment based on the degree of your AV block and the severity of your symptoms.
If you have a first-degree block you may not need any treatment at all.
Treatments for second- and third-degree AV block include:
- Surgical insertion of a pacemaker
- Intravenous medications that will improve your heart’s conduction of electrical signals and increase your heart rate may be administered in the hospital
- Adjustments to any medications you may already be taking that are slowing your heart rate
What are the aims of treatment?
The aims of treatment for people with AV block are to normalize your heart rate and improve your heart’s ability to pump.
In third-degree AV block, the immediate aim of treatment is to prevent cardiac arrest.