What is heart block?

Heart block is a type of heart rhythm disorder (arrhythmia). It is the slowing down or interruption of the electrical signal from the upper chambers of the heart (the atria) to the lower chambers (the ventricles). The electrical signal causes the heart muscle to contract and the heart to beat. A slow heartbeat of less than 60 beats per minute is called bradycardia.

It might help you to learn about how a healthy heart works first.

Heart block may develop in adults or children. Babies can be born with a heart block if they have a congenital heart defect or their mom has an autoimmune disease like lupus. This is called congenital heart block. Sometimes, no cause can be identified.


Heart block is classified by how much the electrical signals between the atria and the ventricles are slowed down. There are three types of heart block:

  1. First-degree heart block is the mildest form and usually doesn’t cause symptoms. Electrical signals are slowed, but they all reach the ventricles.
  2. Second-degree heart block has a slower – and sometimes irregular – heart rhythm. Not all signals reach the ventricles and some heart beats are dropped.
  3. Third-degree heart block (complete atrioventricular block) is the most severe form. None of the electrical signals reach the ventricles. A natural back-up system in the ventricles takes over, but the heart rhythm is slower and more irregular than normal. 

Heart block can occur at any age, but it is most likely to occur in the elderly – especially people who have other forms of heart disease such as:

Some medications – including digoxin, beta-blockers and calcium channel blockers – may cause heart block. If you take any of these medications, your healthcare team will watch you closely for signs of heart block.

Trained athletes and young people with a high vagal tone may also have first-degree heart block. There is one vagus nerve running from your brain to your abdomen on each side of your body. Vagus nerve activity slows the heart rate.


First-degree heart block may not have any symptoms.

Symptoms of second-degree or third-degree heart block range from lightheadedness to fatigue or fainting, shortness of breath and chest pain.


Heart block is usually diagnosed using an electrocardiogram (ECG/EKG), a printed record of your heart's electrical activity that gives information about its rhythm, size and any possible damage.


First-degree heart block might not require any treatment at all.

Sometimes a pacemaker is implanted to treat second and third-degree heart block. The pacemaker takes over the job of regular electrical stimulation of the heart. It will help your heart to beat in a regular rhythm.

Some lifestyle changes such as avoiding stress, and cutting out alcohol and caffeine (coffee, tea, soft drinks, chocolate, and some over-the-counter pain medicines) may be helpful. There are many other important lifestyle changes you can make that can improve your condition including eating a healthy diet and becoming more physically active. Talk to your doctor about the most beneficial lifestyle changes for you.

Some forms of heart block may go away on their own if the underlying condition that is causing the problem is treated or removed. For example, if your medication is causing heart block and you don’t need it anymore, your condition might improve. But never stop taking a prescribed medication without discussing it first with your doctor, nurse practitioner or pharmacist. They will be happy to talk to you if you have any questions or worries about any medication. 

Related information

Living Well with Heart Disease (PDF)


A senior man on a wheelchair talking with his caregiver.

Looking for support?

Find useful services and connect with others living with heart disease or stroke. 
A senior man on a wheelchair talking with his caregiver.