What is an ECG?

An electrocardiogram (ECG) is a powerful tool to measure and display changes in electrical signals produced from your heart when it beats. These can detect and indicate problems that might be going on within the heart itself.¹

An explanation of the lines displayed on an ECG

Your heart has two sides: the right, which carries blood to the lungs to pick up oxygen, and the left, where blood delivers oxygen to your body. Interestingly, if you were to listen to each heartbeat, you would hear two beats. The first keeps blood flowing within the heart, and the second forces blood out of the heart.²

The first beat

At the top of your heart, you have two smaller chambers called atria. In the first beat, blood passes from these atria into larger chambers below called ventricles (Figure 2). This is made possible by two valves, the right tricuspid valve and the left bicuspid valve (think of valves like gates, they let you in and out). Since the first beat doesn’t have to be as strong, an ECG shows a smaller P wave (shown as P in Figure 1).³

The second beat

The second heartbeat forces the blood to exit the heart, either from the right ventricle into the lungs to collect oxygen, or from the left ventricle to deliver oxygen to the rest of your body. Since blood now must travel further, the second beat must be a lot stronger, and this is shown on an ECG by the larger waves known as the QRS complex (see Figure 1).

You may have noticed a T wave on the ECG in Figure 1 above. Electrical activity is what allows the heart to beat, but this relies on sodium moving in and out of cells around the chambers of the heart. During a heartbeat, the sodium moves into these cells, which causes them to contract. After blood is forced out of the chamber, the heart cells need to rest in preparation for the next heartbeat. This is done by sodium moving back out of the heart cells, which is what causes the T wave to show. Think of it as the heart resetting.^4,5,6

What is heart enlargement?

The medical term for heart enlargement is cardiomegaly, i.e. your heart is larger than it should be. The meaning of large here is defined as the heart being 50% or greater than the diameter of the chest (Figure 3 demonstrates how to measure the diameter of the chest).⁷

Did you know that heart enlargement tends to be a direct complication of other diseases related to the heart, most commonly cardiomyopathy (thickening of the heart muscles, affecting how effectively it is at pumping blood)?⁷

Symptoms to look out for

There are a few symptoms of heart enlargement, and if you notice these, you must get medical help:⁸

• Shortness of breath – You may feel this more if you are lying down flat
• Irregular heartbeat
• Swelling in your legs or tummy, which is called oedema

Risk factors that may lead to heart enlargement

It must be noted that heart enlargement is more common in people assigned male at birth compared to people assigned female at birth and tends to affect more adults, although it is not unheard of in children.⁹

Other diseases ECGs can detect have also shown links which expose risks for you developing heart enlargement:

• Coronary artery disease – blockage of blood flow in the blood vessels of the heart
• Ventricular and Atrial Hypertrophy – Enlargement of the atria and ventricles
• Infectious myocarditis – Swollen heart muscles due to infection
• Deposition diseases – Where substances build up in the heart, eventually causing blockages, e.g. amyloidosis

Changes in an electrocardiogram (ECG)

An ECG can reveal multiple changes, which is reassuring, especially for the outlook you face with an enlarged heart. These changes are not directly the result of heart enlargement but are changes due to other conditions that cause heart enlargement.

Hypertrophy causes changes in an ECG which strongly suggest heart enlargement. Let’s look at these changes for each wave shown on an ECG:^7,10

P wave changes

The P waves represent the atria. Enlargement in the right atrium may cause the smaller P wave to appear taller and pointed. If there is enlargement within the left atrium, the P wave may appear wider and can sometimes even have two bumps rather than one.

QRS complex

The QRS complex consists of three waves:

Q Wave – this wave may appear slightly smaller or may not even appear due to changes in electrical activity because of the thicker ventricle walls

R Wave – This wave will often appear taller than usual since the thicker ventricle walls can hold a stronger electrical charge

S Wave – This wave might seem deeper on an ECG because of stress on the heart.

T wave change

If you have seen an ECG in person, you would have seen several leads stuck onto the body. Certain leads measure specific areas of the heart during a heartbeat. In some cases, leads that are measuring the left ventricle can present an inverted T wave on the ECG due to added strain on the heart. A heart that is working harder than usual may also show a smaller T wave.

Remember that the T wave occurs because the sodium is moving back out of the heart cells, so that the heart can reset before it beats again? Heart enlargement can cause this usually smooth wave to be pointed, which suggests that there is a change in how the heart resets.

Other conditions to look out for

There are other conditions that can suggest heart enlargement. Let’s look at how some of these appear on an ECG.^7,10

Hypertrophic cardiomyopathy

Q waves might appear in readings where they would not usually appear. The R waves may become taller, and the S waves might become deeper, similar to what we discussed for the enlargement of chambers. One difference is that the waves might show up on an ECG reading more to the left.

Dilated cardiomyopathy

Like that seen on an ECG representing hypertrophy, the P wave may look more pointed and sometimes may show as a double peak. The larger QRS complex on an ECG may look smaller than usual and can grow in width if there are certain blockages within the heart.

Arrhythmias – irregular heartbeat

Rather than waves changing in appearance, arrhythmias change the frequency. This means that the waves might not be evenly or consistently spaced out.

Ischemic changes

This also includes coronary artery disease, which is commonly known as a heart attack.¹¹ The usually flat area between the S wave and the T wave on an ECG may become dipped or heightened, and the T wave itself may even become inverted or flattened due to changes in electrical activity within the heart.

Amyloidosis - A type of deposition disease

The P wave will have the same height since electrical voltage does not change, but it may appear wider than usual. Low voltage does, however, affect the ventricles, which are represented by smaller QRS complexes on an ECG.¹²

What happens next?

It is important that you take matters into your own hands initially and book an appointment with a GP. This way, you can expose yourself to an array of different tests that will be helpful in diagnosing heart enlargement. Some of these tests include:

• Blood tests
• Chest X-ray
• ECG
• Echocardiogram
• Exercise test
• Cardiac catheterisation
• MRI scan
• CT scan

Treatment

It comes with a disclaimer that treatments for heart enlargement can be quite invasive, and so there is an understandable challenge imposed on you in how to cope with these treatments. Be assured that you are not alone in this decision.⁸

Treatment that falls into medications include:⁸

• Diuretics
• Blood pressure drugs
• Blood thinners
• Heart rhythm drugs

More invasive surgical treatments:⁸

• Pacemaker
• Implantable cardioverter-defibrillator
• Heart valve surgery
• Coronary bypass surgery
• Left ventricular assist device
• Heart transplant

Summary

Turns out that ECGs are a powerful insight into your heart’s health. Specifically, with heart enlargement, there are signs that indirectly suggest that your heart requires critical care. Changes in an ECG affect the position of the waves, specifically waves appearing in readings that should not appear in or whether the shape itself changes to become heightened or flattened. The changes you see in an ECG seem to be across the board, as there is a lot of overlap when comparing the conditions that lead to heart enlargement. This may be quite confusing, and you might be left feeling doubtful. Early detection will give the treatment plan the best possible chance.