Heart Block

Overview

Heart block is a problem with the heart's electrical 'wiring'. Your heart has a natural pacemaker (a small area of cells that starts each heartbeat) and a network of electrical pathways that carry the signal through the heart. The signal normally passes through a kind of checkpoint called the AV node, which sits between the upper chambers (atria) and the lower chambers (ventricles). In heart block, the signal is slowed down or partly or fully blocked at that checkpoint. As a result, the heart may beat more slowly, or the lower chambers may beat on their own slower rhythm. Heart block is not the same as a 'blocked artery' or a heart attack. It is about electricity, not about blood flow through the arteries. Heart block is graded as first degree (mild slowing), second degree (some signals don't get through) and third degree or 'complete' heart block (signals don't get through at all).

Mild (first-degree) heart block is quite common, especially in older adults, and is often found by chance on a routine heart tracing (ECG). Second-degree block is less common and complete heart block is uncommon outside of older people and people with significant heart disease or recent heart surgery.

It can affect anyone at any age, but it becomes more common as people get older. It is more likely in people who already have heart disease, have had heart surgery, or take certain heart medicines. Some young, very fit people, especially endurance athletes, have mild forms with no problem at all. A rare form affects newborn babies and is linked to an autoimmune condition in the mother.

Symptoms

Common symptoms

• No symptoms at all — it is often found on a routine ECG
• Feeling light-headed, dizzy or 'spaced out'
• Feeling unusually tired or lacking energy, especially with activity
• A pulse that feels slow, or a fluttering or skipping feeling in the chest
• Shortness of breath when moving around
• Fainting or a brief blackout (this needs medical attention)

Symptoms in children

• Most children have no symptoms and are found on a heart tracing, often before birth or after birth
• Poor feeding or slow weight gain in babies
• Tiredness or breathlessness during play in older children
• Fainting or dizzy spells in older children and teenagers
• A slow heartbeat noticed by a doctor or nurse

Symptoms in older adults

• Falls or unexplained collapses
• Confusion or memory difficulties that seem new, partly because the brain is not getting enough blood flow
• Feeling very tired doing everyday tasks such as walking upstairs or carrying shopping
• Blackouts that are sometimes wrongly put down to 'just getting older'
• A slow pulse noted by a doctor or nurse

Causes

Main causes

• Age-related wear and scarring of the heart's electrical pathways — the most common cause
• Coronary heart disease or a previous heart attack damaging the electrical system
• Heart conditions such as heart failure, cardiomyopathy (a disease of the heart muscle) or inflammation of the heart
• Heart surgery, particularly valve surgery, or procedures that affect the electrical system
• Some heart medicines that slow the electrical signal — your doctor will review these
• An overactive vagus nerve (the nerve that slows the heart), which can happen in very fit people, during sleep, or with certain stomach upsets
• Rarely, an inherited condition, an infection such as Lyme disease, or an electrolyte imbalance in the blood
• In newborn babies, a rare form passed on through the mother's immune system

Risk factors

• Getting older
• Existing heart disease, a previous heart attack, or heart failure
• Previous heart surgery or certain heart procedures
• Taking medicines that slow the heart rate or the electrical signal
• Uncontrolled high blood pressure or high cholesterol
• Diabetes and long-standing kidney disease
• An underactive thyroid or an electrolyte imbalance
• Being an endurance athlete (for mild forms, usually harmless)
• A family history of heart rhythm problems or inherited heart conditions

When to see a doctor

See a doctor urgently if:

• You faint, black out, or have a fall you cannot explain
• You have new dizziness along with chest pain or breathlessness
• You notice your pulse is very slow and you feel unwell, weak or confused
• You have heart block and your symptoms suddenly get worse

Book a routine appointment if:

• You feel more tired, dizzy or breathless than usual, even mildly
• A smartwatch or home monitor shows a slow or irregular pulse
• Heart block showed up on a heart tracing and you have not yet discussed it with a doctor
• You take a heart medicine and are worried it may be slowing your pulse
• You have a family history of heart rhythm problems or a pacemaker

Diagnosis

Your doctor will ask about your symptoms, your medicines and your family history, and will check your pulse and blood pressure. The key test is an ECG (electrocardiogram) — a quick, painless tracing of your heart's electrical signals that shows which type of heart block you have. Because heart block can come and go, you may be given a portable monitor to wear for a day or longer so your heart can be recorded while you go about normal life.

Tests that may be done

• ECG (electrocardiogram) — sticky patches on the chest record the heart's electrical signal in seconds
• Ambulatory or Holter monitor — a small wearable recorder used for 24 hours or more to catch intermittent block
• Event recorder or patch monitor — worn for days or weeks, with a button to press when you feel symptoms
• Blood tests — to check thyroid, kidney function, salt levels and markers of heart strain
• Echocardiogram — an ultrasound scan of the heart that shows how well the heart muscle and valves are working
• Exercise or tilt-table test — sometimes used to see how your heart rate responds to activity or position
• Electrophysiology study — a specialised test using thin wires inside the heart, only needed in selected cases
• Review of all your medicines, including over-the-counter ones, to look for a treatable cause

What to expect at your appointment

Most people start with a simple ECG in a GP surgery or clinic, which takes only a few minutes and is completely painless. If the first tracing is normal but your symptoms continue, you may be asked to wear a monitor at home. Results usually come back within days to a few weeks. If the type of heart block is serious, you will normally be referred to a heart specialist (cardiologist) quickly, and sometimes you may be asked to stay in hospital for monitoring while a plan is made.

Treatment

Treatment depends on which type of heart block you have and whether it is causing symptoms. First-degree heart block usually needs no treatment at all — just regular check-ups. Second-degree heart block may need monitoring or a pacemaker. Complete (third-degree) heart block nearly always needs a pacemaker. Where another condition or a medicine is causing the block, treating that cause or adjusting the medicine may be enough.

Self-care at home

• Keep taking your medicines as prescribed, but tell your doctor if you feel dizzy or your pulse seems slow — never stop a heart medicine on your own
• Learn to check your pulse, or use a home monitor or smartwatch if you have one, and note the readings when you feel unwell
• Write down your symptoms, when they happen and what you were doing, to share at appointments
• Stand up slowly if you feel dizzy, and sit or lie down straight away if you feel faint
• Avoid driving or swimming alone if you have had unexplained blackouts until your doctor says it is safe
• Keep your blood pressure, cholesterol and blood sugar within the range your doctor advises
• Limit alcohol and avoid recreational stimulant drugs, which can disturb heart rhythms
• Attend your follow-up appointments and heart tracings, even if you feel well

Medical treatments

For mild heart block, the usual approach is 'watch and wait' with regular check-ups and ECGs. If a medicine is slowing the heart's electrical signal, your doctor may adjust the dose or switch to a different one — always discuss this first rather than changing anything yourself. If another condition is behind the block, such as an underactive thyroid, an infection or an electrolyte imbalance, treating that condition can improve the block. For second-degree or complete heart block that causes symptoms, the standard treatment is a pacemaker: a small device about the size of a matchbox, placed under the skin near the collarbone, with thin leads that send gentle electrical signals to keep the heart beating at a safe rate. Some newer pacemakers are tiny and sit directly inside the heart. The pacemaker is fitted under local anaesthetic, usually as a day-case or short hospital stay, and most people notice a big improvement in their energy and dizziness afterwards. You will be given a pacemaker identification card and follow-up checks, often remotely from home.

When is surgery considered?

A pacemaker is not open-heart surgery — it is a small procedure done through a cut of a few centimetres, usually under local anaesthetic with some sedation, and most people go home the same day or the next day. Occasionally, open-heart surgery is needed for a related problem, such as a faulty heart valve or a complication after previous heart surgery, and the electrical issue is dealt with at the same time.

Living with this condition

Most people with heart block, with or without a pacemaker, get on with their normal lives. If you have a pacemaker, you will be given a card to carry, and you should show it at airports and at any medical appointment. Everyday electrical items — phones, microwaves, laptops, hairdryers — are safe to use normally; only very strong magnetic fields, such as some large industrial magnets or MRI scanners, need special handling, and your pacemaker team will explain this. Keep having your pacemaker checked as advised, often with a small monitor at home that sends readings to the clinic.

Lifestyle tips

• Stay as active as your doctor advises — gentle to moderate exercise is good for the heart
• Limit alcohol and avoid smoking, which raise the risk of heart rhythm problems
• Keep to a healthy weight and have your blood pressure and cholesterol checked regularly
• Get enough sleep and manage stress where you can
• Tell any doctor, dentist or surgeon that you have heart block or a pacemaker before procedures
• Avoid very hot saunas or long hot baths if you feel faint easily, and drink enough fluids in hot weather
• Check with your doctor before starting any new medicine, including supplements and cold remedies

Diet and exercise

A heart-friendly eating pattern — plenty of vegetables, fruit, wholegrains, beans and fish, with less salt, processed food and added sugar — supports the heart's overall health. Regular activity such as walking, swimming or cycling helps your heart and circulation, but build up gradually and stop if you feel dizzy or breathless. If you have a pacemaker, you can usually exercise normally; your team may just advise avoiding heavy contact sports or very strenuous upper-body lifting for a short while after the device is fitted. Ask your doctor or cardiac rehabilitation team for advice tailored to you.

Mental health and emotional wellbeing

Being told you have a heart problem can bring worry, poor sleep and low mood, and fainting or dizziness can make you nervous about going out. These feelings are very common and worth talking about — mention them at your appointments, because support is available. Talking therapies, cardiac rehabilitation groups and peer support can all help you feel more confident again. If you ever feel hopeless or overwhelmed, please reach out to a trusted doctor, a local mental health service, or a crisis line in your country straight away.

Prevention

You cannot prevent all heart block, especially the age-related kind, but you can lower your chances by looking after your heart: keeping blood pressure, cholesterol and blood sugar in a healthy range, not smoking, limiting alcohol, staying active and having regular check-ups. If you take a medicine that affects your heart rate, ask your doctor to review it regularly. Anyone with symptoms such as dizziness or fainting should be checked promptly, as early treatment prevents problems later.

Vaccines

There is no vaccine for heart block itself. Staying up to date with routine vaccinations — including flu and pneumonia vaccines if your doctor recommends them — helps protect your heart and general health, especially if you have other heart conditions.

Screening programmes

There is no routine national screening programme for heart block. An ECG is often done before starting certain medicines or before surgery, and your doctor may suggest one if you have a slow pulse, dizziness or a family history of heart rhythm problems. If you have a smartwatch that alerts you to a slow or irregular pulse, mention it to your doctor rather than worrying alone.

Complications

If left untreated

• Fainting and falls, which can lead to injuries such as a broken hip or head injury
• Very slow heart rates that cause severe dizziness, weakness or confusion
• Heart failure, where the heart pumps less effectively and you feel breathless and swollen
• In rare cases, complete heart block can cause a dangerous pause in the heartbeat or a cardiac arrest
• Anxiety and loss of confidence, and giving up activities you enjoy

Long-term outlook

The outlook is generally very good. Mild heart block usually stays mild and needs only occasional checks. For people who need a pacemaker, the device works reliably for many years, batteries are checked without surgery, and most people feel much better and return to their usual activities. Serious complications are uncommon when heart block is found and treated. If you notice new symptoms, tell your doctor early — that is the best way to keep things on track.

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