What is heart block and how does it affect the heart?

When patients are told they may have heart block, the name can understandably sound alarming. Despite the terminology, heart block does not mean that the heart has stopped working. Instead, it refers to a problem with the electrical signals that control how the heart beats.

The heart relies on a precise electrical system to coordinate each contraction. When this system is disrupted, the signals travelling through the heart can slow down or become partially blocked. This disruption is what doctors describe as heart block.

Depending on the severity, heart block can range from a mild electrical delay to a more significant heart rhythm disorder that requires treatment.

How the Heart’s Electrical System Works

To understand heart block, it helps to first understand how the heart normally controls its rhythm.

Every heartbeat begins with an electrical signal generated in a small area of the heart called the sinus node. This signal spreads across the upper chambers of the heart, known as the atria.

The signal then passes through a specialised structure called the atrioventricular node, often abbreviated as the AV node. From there, the electrical impulse travels to the lower chambers, known as the ventricles, which pump blood around the body.

The British Heart Foundation explanation of how the heart works describes how this electrical pathway coordinates each heartbeat.

When electrical signals are slowed or interrupted as they travel from the atria to the ventricles, heart block occurs.

What Happens During Heart Block

In heart block, the electrical signals moving through the AV node or nearby pathways are delayed or partially interrupted.

As a result, communication between the upper and lower chambers of the heart becomes disrupted.

This can cause the heart to beat more slowly than normal, or in some cases irregularly.

When the heart rate becomes too slow, the body may not receive enough blood and oxygen during certain activities. This can lead to symptoms such as dizziness, fatigue, or fainting.

The severity of symptoms often depends on the type of heart block present.

The Different Types of Heart Block

Doctors classify heart block into three main categories based on how much the electrical signals are affected.

First-Degree Heart Block

First-degree heart block is the mildest form of the condition.

In this situation, electrical signals are slowed as they travel through the AV node, but they still reach the ventricles.

Many people with first-degree heart block experience no symptoms and may only discover the condition during routine heart testing such as an electrocardiogram (ECG).

In most cases, it does not require treatment but may be monitored over time.

Second-Degree Heart Block

Second-degree heart block occurs when some electrical signals fail to reach the ventricles.

This means that occasionally a heartbeat is skipped because the signal from the atria does not successfully pass through the AV node.

Some individuals may notice symptoms such as light-headedness, fatigue, or occasional palpitations.

There are different subtypes of second-degree heart block, and treatment decisions depend on how frequently signals are blocked and whether symptoms occur.

Third-Degree Heart Block

Third-degree heart block, also known as complete heart block, is the most serious form.

In this situation, electrical signals from the atria do not reach the ventricles at all. The ventricles must rely on their own slower backup electrical system to generate heartbeats.

This results in a much slower heart rate and can cause symptoms such as:

• Dizziness

• Fatigue

• Shortness of breath

• Episodes of fainting

Complete heart block often requires treatment, commonly with a pacemaker to restore a reliable heart rhythm.

What Causes Heart Block

There are several reasons why heart block may develop.

In some people, the condition occurs because the heart’s electrical system changes naturally with age.

Other possible causes include:

• Coronary artery disease

• Previous heart attacks

• Inflammation affecting the heart muscle

• Certain medications that influence heart rhythm

• Congenital heart conditions present from birth

In some cases, no clear cause is identified.

Understanding the underlying cause helps guide treatment and determine whether the condition is likely to progress.

Symptoms to Be Aware Of

The symptoms of heart block vary depending on the severity of the electrical disruption.

Mild forms may cause no noticeable symptoms at all. More significant heart block may lead to symptoms related to a slower heart rate.

Common symptoms include:

• Fatigue or reduced energy

• Dizziness or light-headedness

• Shortness of breath during activity

• Episodes of fainting

Any persistent symptoms involving dizziness or unexplained fainting should always be assessed by a medical professional.

How Heart Block Is Diagnosed

Diagnosing heart block involves examining the heart’s electrical activity.

The most common test used is an electrocardiogram (ECG). This test records the electrical signals of the heart and can reveal whether those signals are delayed or blocked.

If symptoms occur intermittently, doctors may recommend longer monitoring using portable ECG devices worn for 24 hours or longer.

Additional tests, such as echocardiography, may be used to assess the structure and function of the heart.

These investigations form part of the diagnostic tests used in cardiology to determine the type of heart block and whether treatment is required.

Treatment Options

Treatment for heart block depends on the severity of the condition and the symptoms experienced.

For mild cases, regular monitoring may be all that is required.

If symptoms occur or the electrical blockage becomes more significant, treatment may involve implanting a pacemaker.

A pacemaker is a small device placed beneath the skin of the chest that helps regulate the heart’s rhythm. It monitors the heartbeat and delivers gentle electrical impulses when the heart rate becomes too slow.

Modern pacemakers are highly reliable and allow patients to return to normal daily activities.

A Personal Perspective

When discussing heart block with patients, I often emphasise that the condition involves the heart’s electrical signals rather than a structural blockage in the arteries.

This distinction is important because it helps patients understand why treatments such as pacemakers are effective.

With accurate diagnosis and appropriate management, many people with heart block live active and fulfilling lives.

Regular follow-up and personalised care remain essential to ensure the heart continues to function safely.

Supporting Heart Health

Even when heart rhythm conditions are present, lifestyle habits continue to play an important role in overall cardiovascular health.

Consistent routines such as regular physical activity, balanced nutrition, and effective stress management can support heart function and general wellbeing.

I often encourage patients to focus on steady, sustainable habits rather than drastic changes.

Small daily choices repeated consistently can make a meaningful difference over time.

Conclusion

Heart block occurs when the electrical signals controlling the heartbeat are slowed or interrupted as they travel through the heart. Depending on the type and severity, the condition may cause few symptoms or lead to problems such as dizziness, fatigue, or fainting.

The different forms of heart block range from mild electrical delays to more significant disruptions that may require treatment with a pacemaker.

If you have symptoms such as unexplained dizziness, fainting, or concerns about heart block, contact me to arrange a consultation and discuss the most appropriate evaluation and treatment for your heart health.