Introduction

Heart enlargement, also known as cardiomegaly, refers to a condition where the heart is abnormally thick and larger than usual, resulting in difficulty pumping blood.¹ It is not a disease on its own, but it is a sign of an underlying condition,² such as heart failure. Symptoms of an enlarged heart do not affect everyone with cardiomegaly; however, it can cause shortness of breath, irregular heartbeat, and swelling of the abdomen and legs in some affected individuals.² Although not referred to as a disease individually, some risk factors can lead to cardiomegaly. These include high blood pressure, heart diseases and a family history of heart disease.² Cardiomegaly can affect the whole heart or parts of the heart, and complications can arise depending on the location of affected areas.² Such complications can be heart failure, blood clots, leaky heart valves, cardiac arrest and death.² 

An electrocardiogram (ECG), is a simple diagnostic tool that records the rhythm, rate and electrical activity of the heart.³ During an ECG, cables are connected to the chest via sticky pads. The cables are then connected to a machine that reads myocardial activity.³ Upon completion, the machine prints a trace which doctors can interpret as the presence of abnormal activity. An ECG can be used to detect cardiomegaly, and specific findings on the trace can indicate an enlarged heart. 

Background on cardiomegaly

Cardiomegaly can be used as an umbrella term that encapsulates many conditions that can lead to an enlarged heart.⁴ Several diseases can lead to an enlarged heart, such as: 

• Coronary heart disease
• Hypertension
• Valvular heart disease
• Congenital heart disorders 
• Pulmonary diseases 
• Infectious myocarditis
• Arrhythmia
• Cardiomyopathy⁴ 

Symptoms

Although not everyone with an enlarged heart presents with symptoms, people who do get symptoms can suffer a decrease in their quality of life. Diagnosis of cardiomegaly is often based on testing rather than observing symptoms alone, but in those who do develop signs of the disease, symptoms include: 

• Shortness of breath
• Peripheral oedema
• Fatigue
• Palpitations
• Angina
• Anorexia
• Recent pregnancy 
• Family history of cardiomyopathy⁴

Diagnosis

However, many of these symptoms do not manifest unless the affected individual is exercising, hence many of these symptoms remain dormant and undetected in a sedentary patient.⁴ As symptoms do not affect every person, and may not happen unless, upon exertion, diagnosis of the disease is based on tests such as an MRI, a chest X-ray, an echocardiogram and an ECG.⁴ 

ECG

An ECG is a test used to examine cardiac function.⁵ It works by attaching leads to the chest and recording the heart’s activity. Different leads correspond to different areas of the heart,⁵ which facilitates doctors in understanding where the problem may be. It is now used to diagnose a variety of heart conditions and problems, such as cardiomegaly. 

The leads in an ECG are composed of: 

• Limb leads – RA, LA, LL, RL
• Precordial leads – V1, V2, V3, V4, V5 and VG⁵ 

If a 12-lead ECG is needed, then two more leads will be placed on the back.⁵ It is crucial that the leads are placed correctly in order to properly and accurately detect the heart’s activity. Upon agreement with the individual undergoing ECG, the sticky pads will be placed down, the leads connected, and the ECG machine will be turned on. A trace of the heart’s activity is then swiftly printed out, which can then be read by the physician.⁵ 

ECG indicators of heart enlargement and its severity

Cardiomegaly can cause distinct changes in an individual’s ECG trace, and having these specific indicators on the ECG does not necessarily equate to cardiomegaly, but the correlation between these findings and a diagnosis of an enlarged heart is strongly positive.¹ An abnormally large wave observed in an ECG trace may indicate an enlarged heart.⁶

These ECG changes include:¹ 

• Left ventricular hypertrophy
• Low voltage QRS
• Arrhythmia
• P wave abnormalities
• ST-T wave changes
• Conduction abnormalities
• Q-wave changes 

A higher left ventricular hypertrophy value, usually measured as increased QRS voltage, means that there may be an enlargement in a section of the heart.⁷ The higher the voltage, the greater the likelihood of significant hypertrophy.⁷ The QRS complex represents ventricular depolarisation, and it is made up of the Q, R and S waves.⁸ The QRS complex typically lasts several milliseconds however, it may be higher and longer as it takes longer for a larger heart to depolarise in cardiomegaly.⁸ 

Another value we can look at is how the P wave looks and how it correlates with the severity of the enlargement.⁹ If the P wave on the ECG trace appears wide or tall, it may mean that the atria – two chambers out of the four of the heart are dilated.⁹ The extent of the abnormalities on the P waves correlates with the severity of atria enlargement, and thus the heart. This can be caused by underlying conditions such as mitral valve disease.⁹ 

Another pattern we can look at in cardiomegaly is the ST wave values.¹⁰ In enlargement of the left ventricle, the ST waves may look depressed, shorter than usual, and the T wave may be inverted.¹⁰ 

For all of these ECG changes, the more severe they appear – whether the values become abnormally higher or lower, it indicates that the underlying cardiomegaly is more severe.¹⁰ All of these factors indicate that the heart is enlarged and under more strain. The ECG is also advanced enough that it can tell us if specific parts of the heart are enlarged, such as the left ventricle or the atria, by looking at the specific values.

However, it is important to consider that these ECG changes only correlate with the severity of the disease. Correlation does not necessarily imply causation,¹¹ which means that the changes on the ECG are not causing the severe cardiomegaly, and vice versa. The ECG changes highlight whether the heart is enlarged however, the enlargement itself may be caused by an underlying condition. 

FAQs

Is there treatment for an enlarged heart?

Treatment will depend on the underlying condition that has caused the enlarged heart. This can range from diuretics, beta-blockers, ACE inhibitors, surgeries, lifestyle changes and in severe cases, a heart transplant.¹² 

When should I call a doctor?

You should call your doctor if you suspect you may have an enlarged heart if you are experiencing symptoms or if you want advice on how to manage your condition.¹² 

Is an ECG painful?

No, it is a non-invasive procedure. You will not feel anything.

Summary

Cardiomegaly, more commonly known as heart enlargement, is a condition where the heart is enlarged and under strain due to underlying heart disease. It may cause severe symptoms, such as shortness of breath, swelling of the limbs, chest pain and irregular heartbeats. These symptoms can be scary for the affected individual and they may be anxious about the cause of their disease. Diagnosing cardiomegaly relies on a variety of tests and imaging: one of these is the electrocardiogram, the ECG. An ECG is a machine that can read the heart’s electrical activity and print a trace for doctors to analyse. The patient is connected to the machine with ten - sometimes twelve - leads, which are attached to sticky pads and then to the patient’s chest. An ECG can show specific values that are abnormal in cardiomegaly, such as P wave abnormalities, QRS complex heightened voltage, and ST wave depression and inversion. These values can indicate whether the heart is enlarged, but it is only an implied correlation that needs to be investigated further. However, it is important to note that the more abnormal these values may be, the more severe the cardiomegaly can be. If you suspect you may have symptoms of an enlarged heart, you should see your doctors as soon as possible.