Introduction

Having an enlarged heart is medically known as cardiomegaly. A common misconception is that heart enlargement is a disease of its own; however, it is normally considered a sign of having another underlying disease or condition. For example, in cases of heart failure, the heart needs to work harder to pump blood around your body efficiently. Other causes of heart enlargement include congenital factors, damage from a heart attack, high blood pressure, and heart valve disease, to name a few. In heart enlargement, the muscle cells can either grow bigger, which leads to the thickening of the walls (hypertrophic cardiomyopathy) in your heart, or stretch (dilated cardiomyopathy), thus leading to it becoming enlarged.³ In a few individuals, there are no signs/symptoms of an enlarged heart; however, those who do develop symptoms often report having an irregular rhythm, also known as an arrhythmia, swelling in the legs, or shortness of breath, particularly when lying down.^1,2

It is important to detect an enlarged heart quickly, as it could highlight any underlying conditions and be easier to treat when detected early. This is because it can help you in managing the symptoms with medication or lifestyle changes. It can also prevent any further complications from occurring.¹

Cardiomegaly is normally diagnosed by a chest X-ray, which shows the condition of the heart as well as your lungs. Although with a chest X-ray, other tests are usually needed to determine whether the heart is enlarged, as well as the cause the previously unknown cause. An example of this is cardiac magnetic resonance imaging (MRI), where a clearer, more detailed image of your heart is produced.^4,5

This article aims to address how advancements in cardiac MRI improve the assessment and detection of heart enlargement. 

Basics of cardiac MRI and heart enlargement detection

How does a cardiac MRI work?

You may be wondering how cardiac MRIs work and how the imaging differs from other type of heart scans. The way a cardiac MRI produces an image of your heart is through the use of radio waves and magnets. This then provides either a two-dimensional or three-dimensional image of your heart, and shows how your blood is pumping.⁶ This takes approximately 30 to 90 minutes, depending on how many scans need to be taken. Similar to an X-ray, you will need to lie down on a bed. However, it is inside a scanner, which is tunnel-shaped and open at both ends; this is the MRI machine. An MRI also requires you to stay still while in the machine so that clear images can be produced.⁷

Challenges in detecting an enlarged heart

A major challenge of detecting an enlarged heart is, as aforementioned, that the symptoms such as shortness of breath and fatigue can be easily dismissed or confused with other conditions.⁸ Another challenge is the limitations of some of the imaging used to diagnose cardiomegaly. To expand, echocardiography, which is normally used to detect heart size and function, has a few limitations which can hinder diagnosis, especially in cases where the heart is only slightly enlarged. This could be due to the complex anatomy of the heart, which makes certain structures hard to detect, or due to a poor acoustic window (due to factors such as obesity, previous surgeries or lung disease), which means the image comes out blurry, making it harder to make an accurate diagnosis.⁹ MRI scans also have some limitations, especially in complex cases where a patient may have multiple cardiac conditions or morbidities (other medical issues), and where image interpretation may be difficult. However, recent advances in MRI technology have worked to target these limitations in order to improve detection.⁹

Recent technological advancements in cardiac MRI

Over the last few years, there have been many technological advancements in cardiac MRI techniques to improve the diagnosis of heart enlargement in its early stages. These include methods such as improving spatial and temporal resolution, mapping techniques and whole-heart imaging. 

Improved spatial and temporal resolution (or sharper, faster MRI Scans: seeing the heart in detail)

You may be wondering what the difference is between spatial and temporal resolution. Spatial resolution is the amount of detail visible in an image, or how well you can see two structures that are close together. In other words, if an image is blurry or unclear, it has low spatial resolution.¹⁰ Temporal resolution is the ability of the imaging technique to distinguish and capture multiple images of an event that happens or changes over time.¹¹ This is important when scanning the heart as it is constantly beating, so a high temporal resolution would be needed to create a detailed image of heart size and function. Overall, both these factors are important in ensuring a clear, detailed image is produced for clinicians to interpret and make a proper assessment. These factors have been considered to develop advanced imaging techniques such as cine and real-time imaging. 

Cine and real-time imaging (or real-time imaging: Watching the heart beat in Action)

Traditional cine imaging requires the patient to hold their breath during repeated scans, which can be uncomfortable for patients with underlying conditions. It is also used alongside other machines, such as an ECG, to provide a full picture of the heart as it beats.^12,13 Recent advances in cine imaging, coupled with real-time imaging, allow for an image to be produced with a high spatial and temporal resolution without having to hold your breath. This, therefore, makes the imaging process much easier when capturing the entire cardiac cycle and the size of the heart. Although some results are comparable with traditional cine imaging, this new approach paves the way for further advances in detecting heart enlargement.¹⁴

How T1/T2 mapping helps spot early heart changes

T1 and T2 mapping is a method used in cardiac MRIs to measure the tissue properties of the heart muscle.¹⁵ In heart enlargement, the muscle cells can either grow bigger (leading to thickened heart walls) or stretch outwards (dilated cardiomyopathy), thus becoming enlarged.¹⁶ Hence, the mapping allows for analysis of the heart muscle and its function by measuring the space between muscle cells, also known as the extracellular volume fraction. As these scans can often be time-consuming, researchers have developed a new technique called CMR multitasking that allows T1/T2 mapping to be done alongside other forms of T1 mapping, including time-resolved scans. This method reduces the time taken to produce an image, making the experience more comfortable for the patient.¹⁶

3D whole-heart imaging (or 3D Imaging: A complete view of the heart)

Furthermore, recent advances have enabled researchers to develop a non-invasive technique that creates and provides 3D images of the heart while breathing. This helps address the limitations of other methods. In studies conducted, 3D imaging provided a higher resolution image depicting all the anatomy of the heart, allowing for quicker interpretation.^17,18 Although it is not yet available for clinical use, this holds promise for the future of cardiac MRIs, making it easier to assess not only heart enlargement but also other cardiac conditions. 

Advantages of advanced cardiac MRI for heart enlargement assessment 

The recent advancements in cardiac MRI highlight several valuable advantages in detecting and assessing heart enlargement. Although some have already been mentioned, the key advantages include:

Detailed imaging

• These recent advances allow clinicians to produce more detailed images of the heart's structural characteristics, leading to quicker and more accurate assessment

Non-invasive

• As MRIs do not use radiation, they are considered safer and non-invasive for patients, especially those who may need repeat scans

Functional assessment

• Cardiac MRIs can provide information about how the heart functions by measuring blood flow and the performance of the heart muscle. This is particularly important because the heart's pumping ability may be affected over time by the structural changes seen in an enlarged heart¹⁹

Clinical implications

Although cardiac MRIs show great promise in the assessment and detection of heart conditions, there are some implications of their use, such as: 

Limited availability

• Some hospitals may not have cardiac MRI scanners, which could increase patient waiting times or require them to travel to other areas for the scan

Costly

• Cardiac MRIs are much more expensive than other tests used to assess heart enlargement due to the specialised equipment and the image-taking process. This could therefore limit their use, especially for routine check-ups¹⁹

Summary

To conclude, cardiomegaly, or an enlarged heart, is often a sign of another underlying condition rather than a disease in itself. The causes of an enlarged heart range from heart failure and congenital factors to high blood pressure or heart valve abnormalities. Symptoms may include arrhythmias, leg swelling, and shortness of breath, though some individuals may remain asymptomatic, meaning they don’t develop any of these symptoms. While chest X-rays are commonly used to diagnose cardiomegaly, cardiac magnetic resonance imaging (MRI) provides more detailed and accurate images, helping in the identification of heart size as well as its function. 

Recent advancements in cardiac MRI, such as improved spatial and temporal resolution, cine and real-time imaging, and techniques like T1/T2 mapping or 3D whole-heart imaging, have improved the ability to detect heart enlargement at an earlier stage. Alongside this, AI has also been harnessed to speed up analysis and deliver computational techniques, supporting greater diagnostic accuracy ^20,21. 

These innovations support clearer, non-invasive, and more comprehensive assessments of an enlarged heart. However, challenges such as high costs, limited availability of MRI machines, and the need for specialised training may restrict the use of certain cardiac MRI techniques. Despite these barriers, advanced cardiac MRI techniques show great promise in improving diagnosis, assessment and management of heart enlargement and related cardiovascular conditions, as well as improved patient outcomes.