Introduction

Heart enlargement also known as cardiomegaly means an increase of the heart size beyond normal. It occurs when the transverse diameter of the cardiac contour (the heart’s visible structure as shown in an x-ray or other imaging studies) is greater than or equal to 50% of the transverse diameter on a back to front projection of the chest radiograph or computed tomography.^1,3

As estimated by the World Health Oragnisation, 17.9 million people died from cardiac vascular diseases in 2019, representing 32% of all global deaths. Of these deaths, 85% were due to heart attacks or strokes which may occur as a result of an enlarged heart. Also, out of 17 million premature deaths (under the age of 70) in 2019 occurred as a result of noncommunicable diseases, of which 38% were caused by cardiac vascular diseases.²

There are different forms of image studies that can be used to diagnose the presence of cardiomegaly (heart enlargement), but this article focuses on the use of echocardiography to observe the features indicating an enlarged heart.

Understanding heart enlargement

Heart enlargement also known as cardiomegaly means an increase of the heart size beyond normal. It occurs when the transverse diameter of the cardiac contour (the heart’s visible structure as shown in an x-ray or other imaging studies) is greater than or equal to 50% of the transverse diameter on a back to front projection of the chest radiograph or computed tomography.¹

An enlarged heart is not a disease in itself rather, it is a symptom of an underlying health condition associated with the heart. These conditions can be congenital (health condition(s) acquired right from birth) or developed overtime.³

There are several factors/conditions that cause heart enlargement. They include the following:

• Coronary artery disease, which is the most common cause. This may be a  reason for a heart attack or the presence of insufficient blood flow to the heart
• High blood pressure
• Heart valve diseases, where one of the heart’s four valves (the aortic, mitral, pulmonary, or tricuspid valve) becomes too narrow or starts to leak. It can also happen when there is a bacterial infection in the heart’s lining
• Congenital heart disease like a hole in the heart, Ebstein anomaly, and coarctation of the aorta
• Certain lung diseases like blood clot in the lungs, chronic obstructive pulmonary disease, and hyperventilation syndrome in obese people
• Substances like alcohol, cocaine, or certain chemotherapy drugs (like doxorubicin, cyclophosphamide, trastuzumab) and radiation can induce cardiomegaly
• Some immune system diseases that create inflammation in the heart tissues
• Natural conditions such as stress cardiomyopathy, enlargement of the heart due to exercise, or increased heart size during pregnancy
• And other genetic factors^1,3

What is echocardiography?

Echocardiography is a non-invasive (i.e it doesn’t involve piercing the skin) safe procedure where sound waves that cannot be heard are sent to check the components of the heart using a transducer (something that looks like a microphone). Results obtained help to show the size and structure of the heart during a cardiac cycle.^4,5

When the transducer is placed on the chest, it sends waves into different parts of the heart. These waves echo back, they are recorded and sent to the computer creating images on the screen which are later recorded or saved.^4,5

The importance of this procedure is to check for the presence of any abnormalities in the heart’s chamber, valves, and its overall performance to detect any form of condition.^4,5

There two types of echocardiography:

• Transthoracic echocardiography (TTE): The transthoracic method shows real time sizes, structure and function of the heart during its cardiac cycle. It is a non-invasive process⁴
• Transesophageal echocardiography (TEE): The transesophageal method is more invasive than the standard transthoracic method. It requires the insertion of a tube into a patient’s esophagus to obtain images inside not hindered by the chest wall. This method is used when deeper studies are to be done⁴

Key features of heart enlargement detected by echocardiography

The transthoracic method will be used to discuss the key features of heart enlargement.

• Right atrial enlargement: the right side of the heart is viewed and measured from its top most part where all four chambers of the heart are visible. To measure the size accurately, the outlines of the heart are measured when it fully contracts. To get accurate measurements, the following procedure is done;
  • Long axis(major): involves taking measurement along the length of the heart. On average the measurement of the heart is 4.4 cm. If it is over 5.3 cm then the heart is enlarged
  • Short axis(minor): involves measuring the heart at its widest point. The measurement is around 3.5cm and can be considered enlarged when it is over 4.5 cm
  • Area: involves measurements around the heart’s outline which includes the valve and all its inner walls. The average area is 11 cm but above 18 cm is enlarged⁶
• Right ventricular enlargement: the right lower side of the heart chamber is viewed to check for the presence of enlargement. Its form of enlargement is group into;
  • Mild enlargement: the width of the right chamber is larger than normal(over 4.2 cm), but the left chamber is still bigger
  • Moderate enlargement: the right chamber is nearly the same size as the left, but the left chamber still points to the tip of the heart
  • Severe enlargement: the right chamber is now larger than the left and forms the tip of the heart⁷
  • Left atrial enlargement: the disk summation model is used to measure the left lower heart chamber. To calculate the volume of the left atrium, the inner chamber wall is measured excluding the veins and the area around the heart’s valve. Features are almost  similar to the right side
• Left ventricular enlargement: Features are;
  • Larger Size: The inside width of the left side of the heart when it’s relaxed gets bigger:
    • For women: over 5.3 cm
    • For men: over 5.9 cm
  • Larger Volumes: The amount of blood the heart holds at different times is increased:
    • When relaxed (diastole):
    • For women: over 104 mL
    • For men: over 155 mL
  • When pumping (systole):
    • For women: over 49 mL
    • For men: over 58 mL
• Shape Change: Normally, the left side of the heart is oval-shaped, with the length being about twice the width. When the heart is severely enlarged, it starts to look more round, with the length and width becoming similar⁹

Summary

Echocardiography is one of the reliable methods for checking the features of the heart. It shows the structure, function, the presence of a heart disease and other underlying conditions. 

Having the knowledge of these features of the heart when detected through echocardiology, helps to influence a patient’s diagnosis, management and treatment helping the doctor(s) to make informed decisions and manage heart conditions effectively.