What Is an ECG?

An ECG is one of the most commonly used tests in cardiology, yet many patients are unsure what it actually measures or why it has been recommended.

In simple terms, an ECG, which stands for electrocardiogram, records the electrical activity of the heart. It helps us assess how the heart is beating, whether the rhythm is regular, and whether there are signs of strain or underlying heart disease.

In my experience, patients are often reassured by how quick and straightforward the test is. We’ve found that explaining the purpose of an ECG beforehand helps reduce unnecessary anxiety and allows patients to feel more comfortable during the appointment.

What an ECG Measures

Every heartbeat is controlled by electrical signals travelling through the heart muscle.

An ECG records these signals using small sensors attached to the skin. The test produces a visual trace showing how the electrical impulses move through the heart.

This allows us to assess:

• Heart rhythm

• Heart rate

• Signs of irregular heartbeat

• Evidence of previous heart strain or damage

• Changes that may suggest reduced blood flow to the heart

In practice, what I see is that many patients assume an ECG looks directly at the structure of the heart. In reality, it specifically measures electrical activity.

Why an ECG Is Performed

An ECG is commonly recommended when patients experience symptoms that may relate to the heart.

These include:

• Chest discomfort

• Palpitations

• Dizziness or fainting

• Shortness of breath

• Fatigue

In my clinics, ECGs are performed routinely because they provide valuable information quickly and non-invasively.

What actually tends to happen is that the ECG either reassures us that the rhythm appears normal or helps identify whether further investigations are needed.

What Happens During the Test

One of the most reassuring aspects of an ECG is how simple the process is.

Small adhesive sensors, called electrodes, are placed on the chest, arms, and legs. These are connected to the ECG machine using wires.

The test itself is painless and usually takes only a few minutes.

In practice, we’ve found that many patients worry the test involves electric shocks or discomfort. However, the machine only records electrical signals. It does not send electricity into the body.

During the recording, you will usually be asked to lie still and breathe normally while the trace is captured.

What an ECG Can Detect

An ECG can provide important information about how the heart is functioning.

It may help identify:

• Atrial fibrillation

• Other abnormal heart rhythms

• Signs of previous heart attacks

• Evidence of strain on the heart

• Conduction problems such as heart block

In my experience, ECGs are particularly useful when symptoms such as palpitations or dizziness are present.

However, it is important to understand that a normal ECG does not always completely rule out heart disease.

The Limitations of an ECG

Although an ECG is extremely useful, it is only one part of a wider assessment.

What actually tends to happen is that patients assume a normal ECG means there is definitely no heart problem. In reality, some conditions may not appear on a short recording, particularly if symptoms are intermittent.

For example:

• Palpitations may not occur during the test

• Coronary artery disease may not always produce ECG changes at rest

• Structural heart conditions often require imaging tests such as echocardiography

In our experience, combining the ECG with a detailed clinical assessment provides the clearest overall picture.

Different Types of ECG Monitoring

There are several forms of ECG monitoring depending on the symptoms being investigated.

Resting ECG

This is the standard ECG performed in clinic while you are lying down.

Holter Monitor

This records the heart rhythm continuously over 24 to 48 hours or longer.

It is particularly useful when symptoms occur intermittently.

Event Monitors

These devices are worn for longer periods and activated during symptoms.

In my experience, extended monitoring works better than a single ECG for intermittent palpitations because it increases the likelihood of capturing the rhythm during an episode.

A Real-World Perspective

One of the most common things I hear is patients worrying before an ECG because they expect it to be uncomfortable or complicated.

In practice, it is one of the simplest investigations we perform.

In my clinics, the majority of ECGs are completed within minutes, and many provide immediate reassurance.

Another important point is that the ECG is often the starting point rather than the final answer. It helps guide whether additional testing is necessary.

Why ECGs Remain So Important

Despite advances in cardiac imaging and wearable technology, the ECG remains one of the most valuable tools in cardiology.

It is quick, accessible, and provides immediate information about the heart’s electrical activity.

From working with patients over many years, we’ve found that early ECG assessment often helps identify rhythm problems before they become more significant.

Conclusion

An ECG is a simple and painless test that records the electrical activity of the heart. It is commonly used to investigate symptoms such as chest discomfort, palpitations, dizziness, and shortness of breath.

In my experience, the ECG remains one of the most useful first-line investigations in cardiology because it provides rapid and valuable information about the heart’s rhythm and function.

If you have been advised to have an ECG or are concerned about symptoms affecting your heart, you can contact Roy Jogiya at Kingston Cardiologists to arrange a consultation and discuss the most appropriate next steps for your care.