Our hearts are a central organ that helps to keep us alive. Day in and day out, our hearts are pumping blood throughout our bodies, providing our cells and tissues with oxygen and key nutrients to keep us going 

However, because of their central role in our body, it can be difficult to accurately diagnose heart problems. Symptoms of heart problems can be mistakenly linked to other illnesses and conditions, preventing the appropriate treatments being given to patients. The consequences of these mistakes can be fatal. In this article we will explore how CT scans can help with diagnosing one specific heart condition, heart enlargement.

Introduction to heart enlargement

What is heart enlargement?

Heart enlargement, also known as cardiomegaly, is a condition where the heart becomes enlarged which can impact its function. The heart comprises 4 chambers where blood can travel in two loops; oxygenated blood travels throughout our body to provide our cells with nutrients and deoxygenated blood travels separately to the lungs to become oxygenated. In order to pump the blood, these heart chambers are separated by valves and each valve is surrounded by muscle that can contract to push the blood through these loops. 

When cardiomegaly occurs, either the heart muscle becomes thicker or the heart chambers become larger, both of which cause the heart to enlarge. This increased muscle wall thickness or increased size of the chambers can occur in any section, or even all parts of the heart. Having an enlarged heart is usually an indicator of a more serious disease as the consequences of having an enlarged heart can be very severe. Therefore, having regular checkups can help to manage the symptoms of this condition.

What are the symptoms of heart enlargement? 

• Shortness of breath - Individuals may feel the sensation of shortness of breath after exercise or even when resting. Some people may even wake up from sleep because of this feeling
• Headaches - headaches and lightheadedness can be common symptoms of heart enlargement as enough blood isn’t circulating around the body. Some individuals may also experience fainting spells due to a low blood pressure
• Chest pain - Also known as angina, this sharp squeezing pain in the chest can also spread to the shoulders, jaws and arms. Experiencing angina as a result of a reduced blood flow to the heart and can have serious consequences if left untreated. It's important to note that chest pain can have many other causes and not all chest pain is due to heart problems
• Tiredness - individuals may feel tired quite quickly despite having plenty of sleep and performing exercise may be difficult. This could be due to a reduced blood flow around the body
• Swelling - swelling or edema of the legs, ankles and feet and a bloated feeling may be experienced by those with cardiomegaly. This swelling could indicate that the heart is unable to pump hard enough to push blood up the body and as a result, blood accumulates in the lower body

Many of these symptoms are non-specific and could be linked to many heart conditions or even other illnesses. Many people with heart enlargement may not show symptoms at all, whilst for others, they may get worse over time. Medical imaging technology such as C.T scans can be very useful in making an accurate diagnosis and ensure patients get the appropriate treatment they need.

How do CT scans work to monitor heart enlargement?

What is a CT scan?

A computerised tomography (CT) scan uses X-rays and special computer technology to create cross-sectional images of the body. CT scans create much more detailed images than singular X-ray images and can be stacked to create 3D images of the body. CT scans are able to provide images of both soft and hard tissues of the body, so are useful in visualising both bone and blood vessels. A CT scan can be used to see the heart structure, the valves within each chamber and the muscular walls surrounding it, making it a useful tool to diagnose and monitor heart enlargement. 

What is a coronary angiogram CT?

Coronary computed tomography angiography (CTCA) is a specific type of CT scan used to image the coronary arteries. These blood vessels supply blood to the heart specifically allowing cardiac muscle cells to access nutrients and oxygen. If the coronary arteries become blocked, the heart is no longer able to access oxygen and this can lead to a heart attack. Coronary arteries can become blocked due to fat, cholesterol and other substances depositing in the arteries which narrow the blood vessels. As we age, deposition of fat in the arteries can accumulate and if appropriate lifestyle changes are not put into place, it can lead to the condition of atherosclerosis. Atherosclerosis in the coronary arteries is known as coronary artery disease.

Coronary artery disease can be linked to an enlarged heart, as if the heart’s own oxygen supply is lowered, the heart will pump harder to make up for it. This can lead to the muscle walls becoming thicker and overall, the heart becoming larger and more inefficient at pumping. A CTCA allows the coronary arteries and surrounding structures of the heart to be visualised allowing the overall health of the heart to be monitored. A CTCA scan works by first injecting the patient with an iodine dye which acts as a contrast on the computer images. This contrast helps to make the coronary arteries stand out in the images. Then the patient undergoes the CT scan and afterwards, the images collected can be processed by a radiographer to assess the health of the patient's coronary arteries. This information can be used to help manage the symptoms of coronary artery disease, including heart enlargement.

What is a coronary artery calcium (CAC)?

Also known as a coronary calcium score, this CT scan can be used to calculate the amount of calcium present in the coronary arteries. Calcium can be one of the components of the plaque that builds up in the coronary arteries and can contribute to an enlarged heart. Unlike the CTCA, a CAC does not require a dye to be injected into the patient beforehand. Instead, the patient will be taken straight to the CT scanner. The results from a CAC can help inform doctors about the appropriate treatments to give to patients and if they are at risk of future heart attacks. CAC scans are particularly advantageous to use for patients who are not showing symptoms of heart enlargement.

The calcium score itself is calculated by measuring the density of the calcium deposits on the images. The higher the calcium score, the greater the risk the individual has of experiencing a major cardiovascular event in the future (e.g. a heart attack). The calcium score is particularly useful in assessing patients who do not show symptoms of heart enlargement but have other risk factors for heart disease (e.g. diabetic, previous history of heart problems). This can help doctors provide preventive treatment to individuals who have a high coronary calcium score.

Recommended frequency of CT scans

A CTCA can provide information about the coronary arteries as well as the entire heart structure and often the diagnostic tool used by doctors in patients showing symptoms of heart disease or have a known history of coronary artery disease. As these patients already present signs of heart disease, often one scan is enough to make a diagnosis. The diagnostic accuracy of CTCA in identifying abnormal coronary arteries is high, with a diagnostic sensitivity of 97%.⁴

Recommendations to rescan for a CAC 

For individuals with a coronary calcium score of 0, the risk of future major cardiovascular events is very low. A 2009 study compiled data from 13 different researchers focused on patients receiving a CAC scan. It was found that of the 29,000 patients, less than 1% of those with a CAC score of 0 experienced a cardiovascular event (heart attack, stroke).¹ This study followed-up with patients 4.5 years after their initial CAC scan. The European Society of Cardiology (in which the British cardiovascular society is a member of), recommends for low risk patients with a calcium coronary score of 0 that a repeat CAC scan should be performed 5 years after their initial scan.²

Those with a high CAC score (400 and above) have a high risk of a future heart attack, so often do not require another CAC scan as they will be showing symptoms of serious heart disease and often the appropriate preventive treatments will be given to patients without a need for a scan. 

Individuals that have a medium CAC score (between 100 and 300) have a 5-20% increased risk of experiencing a heart attack in the future compared to those with a CAC score of 0. Therefore a rescan every 3 years is recommended³ for patients in this risk group. 

Summary

An enlarged heart can occur from the result of an increased heart muscle wall thickness or thinning of the cardiac muscle walls. These changes negatively affect the heart's ability to pump blood and supply enough oxygen and nutrients around the body. Because of this, individuals with enlarged hearts may experience a range of symptoms from tiredness, chest pain, headaches and swelling. If the appropriate treatments are not given to individuals with enlarged hearts, these symptoms may get worse over time. Fortunately, CT scans have emerged as useful tools to identify and accurately diagnose heart enlargement. CT scans can create 3D images of the heart interior, allowing blood vessels, muscle walls and heart chambers to be seen clearly. Specific types of CT scans can be used to visualise the coronary arteries or calculate the amount of calcium deposited in them. These tools can help ensure an accurate diagnosis is made and help inform patients if they are at risk of future heart problems.