Heart block

What happens in heart block?

Your heartbeat is controlled by electrical signals that travel from the upper chambers in your heart (the atria) to the lower chambers (the ventricles), making them contract. If you have heart block, these electrical signals become slowed down or blocked as they travel through your heart. This can happen at various points in the electrical pathway.

Atrioventricular (AV) heart block

In this type of heart block, the delay or block happens when the electrical impulses travel between your atria and your ventricles. It’s categorised into three levels.

• First-degree – this is the mildest form, when the impulses still travel from the atria to the ventricles, but more slowly. You rarely get symptoms with this type.
• Second-degree – this is when some impulses pass through to the ventricles, but some are blocked.
• Third-degree (complete heart block) – this is the most serious type, where the impulses are completely blocked from travelling to your ventricles. Your ventricles end up beating with their own rhythm, and sometimes your heart may stop altogether. 

Bundle branch blocks

This happens when the electrical impulses travel from your atria to your ventricles, but then became delayed or blocked as they travel through your ventricles. It can affect the electrical pathways on the left- or right-hand side of your heart. It doesn’t usually cause any symptoms, but it can be a sign that you have another heart condition.

Watch our animation to see how your heart beats normally and what happens in heart block.

Symptoms of heart block

Whether or not you have any symptoms from heart block depends on the type of heart block you have, and how serious it is.

You may:

• feel very tired (fatigued)
• feel light-headed, faint or pass out
• feel short of breath
• get palpitations (you can sense your heart thumping, fluttering or skipping beats)
• feel sick or vomit

If you have any of these symptoms, see your doctor.

Diagnosis of heart block

Your doctor will ask about your symptoms and medical history, including whether you’re taking any medications. They’ll examine you, and check your pulse and blood pressure too. If you’ve been having palpitations, your doctor will want to know what they feel like and when you tend to get them. 

You’ll need to have a test called an electrocardiogram (ECG). This measures the electrical activity in your heart. You may need to have an ambulatory ECG, which records your heartbeat while you go about your usual activities over 24 hours or more. Or you might need to have an implantable loop recorder. This is a small device which is implanted under your skin and is programmed to record abnormal rhythms. Your doctor will refer you to a cardiologist (a heart specialist) if you need to have this.

Your doctor or cardiologist may also arrange for you to have some of the following tests to investigate your symptoms. 

• Blood tests to check the levels of certain substances that might be related to arrhythmia in your blood.
• Chest X-ray. This allows your doctor to look for any changes in your heart or lungs that might be causing the problem.
• Echocardiogram. This test uses ultrasound to provide a clear image of your heart muscles and valves and can show how well your heart is working.
• Exercise ECG (cardiac stress test). This is when you have an ECG while you exercise on a treadmill to see if this triggers an arrhythmia.
• Tilt table test. You might have this if you have lots of dizzy spells or fainting episodes. It involves measuring your heart rate, rhythm and blood pressure, while you lie on a table which is slowly tilted upwards.
• Electrophysiology studies. This checks the electrical activity of your heart and can help to identify a heart block.

Treatment of heart block

Your treatment for heart block will depend on how serious it is and whether it’s causing any symptoms. If you have mild (first-degree) heart block, you probably won't need any specific treatment. Your doctor will review any medications you’re taking, and may suggest stopping any that could be causing your heart block. If your heart block is caused by an underlying health condition, your doctor will focus your treatment on that.

If your heart block is more serious and isn’t caused by medicines or an underlying health condition, you’ll probably need to have a pacemaker. This is a device that helps to control your heartbeat.

Temporary pacing

Sometimes, you might have what’s known as temporary pacing, to see if this improves your symptoms. This is when a wire is guided through a vein up to your heart. The other end of the wire is fixed outside of your body. The wire conducts electrical impulses to control your heartbeat. You might have this instead of a permanent pacemaker or while you’re waiting for one to be fitted.

Permanent pacemakers

A permanent pacemaker is a small device fitted inside your chest, that monitors your heartbeat and sends electrical signals to stimulate your heart. Most pacemakers only send signals if your heartbeat slows below a certain pre-set level. Usually, pacemakers with two leads (called dual-chamber pacemakers) are used for heart block. The two leads connect to two different points in your heart – usually your right atrium and right ventricle.

You’ll usually have a pacemaker fitted under local anaesthesia and sedation. This means your chest area will feel numb, and you may feel sleepy with the sedative. Your cardiologist will make a small cut just under your collarbone, and insert the pacemaker, before threading the leads into the right position in your heart. You’ll usually have to stay in hospital overnight, but you should be able to go home the following day. Your cardiologist will check that the pacemaker is working correctly before you leave. 

Living with a pacemaker

You should be able to live a normal, active life with a pacemaker, and most people find that their quality of life improves. However, there are certain things about living with a pacemaker that you’ll need to be aware of. The staff at the clinic will go through this with you. 

• You won’t be able to drive for a week after your procedure
• You may need to be careful about taking part in certain sports at first (see our FAQ: Can I exercise or play sports with a pacemaker?)
• You’ll be able to use everyday electrical devices such as mobile phones, laptops and household appliances, without any problems. But keep them at least 12cm away from your pacemaker – don’t hold them directly over where your pacemaker is fitted.
• Strong magnetic fields may interfere with your pacemaker. If there’s a chance you’ll be exposed to this – for instance, in your workplace – speak to your clinic.
• If you go for any medical tests or procedures or you’re admitted to A&E, always let the medical staff know that you have a pacemaker.

Causes of heart block

Causes of heart block include:

• damage and stiffening of the tissues in your heart, which often happens as you get older
• coronary artery disease
• some types of medicine such as beta-blockers and calcium-channel blockers
• heart muscle diseases (cardiomyopathy)
• heart conditions you're born with (congenital heart disorders)
• having surgery on your heart, such as an operation on your heart valves
• infectious diseases such as Lyme disease