Types Of Heart Scan

Introduction 

Heart scans are imaging techniques used to visualise the heart and surrounding structures, which include:

• The heart and its internal structures
• The arteries and the veins surrounding the heart 
• The pericardium

The early detection of heart conditions is key to successfully managing and treating them, and with the growing range of cardiac tests available, we are better equipped than ever to identify potential problems as soon as possible. New technologies have revolutionised cardiac imaging, offering doctors pictures with unprecedented clarity and resolution.^1,2,3

Different heart scans are selected and performed according to the patient's history, symptoms, signs, and physical examination findings. Conditions that may require cardiac imaging include:

• A myocardial infarction (heart attack)
• Heart failure
• Congenital heart disease
• A malfunction in one of the heart valves
• Infective endocarditis
• Pre-surgical assessment

In this article, we will discuss the common types of heart scans and their important characteristics. 

Common types of heart scans 

Echocardiogram (echo)

An echocardiogram is an ultrasound of the heart. Sound waves are used to create an image of the heart and its surrounding structures. It is a painless scan and uses no ionising radiation. It is used frequently by cardiologists. Before an echocardiogram, an ultrasound jelly is put on the left side of the chest. A probe is used to detect sound waves and create an image of the heart and its structures.^4,5 

Echocardiography visualises the structure of the heart, pericardium (heart lining), ventricles and aortas (the chambers of the heart), the heart valves, major blood vessels, and cardiac septa (the muscle separating the left and right sides of the heart). In addition, it images the blood flow in the heart and the surrounding vessels.

This test is indicated for patients with myocardial infarction, congenital heart disease, valvular anomalies, infective endocarditis, and many more conditions. Echocardiography has no contraindications, but it provides limited information for obese patients and patients with overcrowded ribs, as the thickness of the chest wall reduces the transmission of sound waves.^2,6

Cardiac computed tomography scan (CT)

A CT scan is used to create a 3-dimensional image of the heart using multiple layers of X-rays. It is a painless scan, but it emits a significant amount of ionising radiation, meaning it is not recommended for patients who are pregnant or have other conditions where radiation exposure should be limited. 

A contrast medium (dye) can be used in some cases to help create a better visualisation of the heart. This test is done in cases where other tests do not provide enough information for the diagnosis, prognosis and/or treatment modality of a disease.⁷ Using a CT scan, your healthcare provider will be able to see the complete structure of your heart and its surrounding structures. It is indicated in patients who have heart blockage and structural abnormalities. 

Single-photon emission computed tomography (SPECT)

A SPECT heart scan provides information about the structure and function of the heart. It uses gamma rays and gamma cameras. A radiotracer (gamma-emitting radioisotope) is injected into your veins and used to create an image based on your heart’s uptake of this radiotracer. The image created is dependent on the flow of the blood and the metabolism in the heart muscle.⁸ Therefore, this test is often used to evaluate the blood supply to the heart both at rest and after exercise or pharmacologic stress (when drugs are used to increase your heart rate instead of exercise). It is not recommended for pregnant patients or patients who have allergic reactions to the radiotracer (but this is very rare).

Cardiac positron emission tomography (PET)

During a PET scan, you will be injected with a radioactive tracer. As it decays, a scanner detects it and creates an image of your heart. A SPECT scan can be combined with a PET scan to provide an even better analysis of the functioning of the heart. However, PET scans have a high ionising radiation exposure and thus are contraindicated for patients who are pregnant or who have some other pre-existing conditions.²

Coronary CT angiogram 

Before a CT angiogram, your cardiologist will use anaesthetic to numb you, then nick a blood vessel and insert a catheter (long flexible tube) into the blood vessel. They will then thread the catheter through the blood vessels to the coronary arteries, which supply blood to the heart. At this stage, a contrast dye will be injected into the coronary arteries, and X-ray images will be taken to image them.

Coronary CT angiograms are typically used to detect and find blockages in the coronary arteries. They are often done before cardiac surgical interventions like stenting (angioplasty) and cardiac bypass surgery. This procedure exposes you to a high level of ionising radiation, and therefore it is contraindicated in pregnant patients. It is indicated in patients with myocardial infarction and/or coronary artery disease. Common side effects of this procedure include swelling or infection at the site of the incision.^3,5,9

Cardiac MRI

A cardiac MRI is a pain-free and non-invasive imaging technique. An MRI does not use any ionising radiation and instead uses radio waves, a magnet, and a computer to create a high-quality 2D and/or 3D image of your heart. Sometimes, a contrast dye will be used as well. It is more time-consuming compared to the other tests. During an MRI, you will lie inside a metal tube-like machine, which will make loud thumping noises. If you are uncertain of what to do or become uncomfortable, you can speak to your doctors through a speaker. 

This scan is used when a highly detailed picture of the heart is needed. It's important to inform your doctor about any metal objects in/on your body, including implants and piercings, before undergoing this medical procedure. People with claustrophobia (fear of confined spaces) and children are given sedatives if required, as you must lie completely still for the duration of the scan. Further, MRIs are safe for pregnant patients.^{2 3,5}

Multigated acquisition (MUGA) scan

MUGA scans are used to check how well your heart is pumping blood, and is typically used on patients experiencing heart failure. It measures ‘ejection fraction’, which indicates the percentage of your blood that is pumped out of the heart with each contraction. 

This scan uses a radiotracer and a specialised camera to create an image of the heart and the heart muscles. You will be asked to lie down, and electrodes will be placed on your chest. A camera will then be positioned above your chest, and the radiotracer will be injected into your blood. The camera produces images after detecting the radiation emitted by the radiotracer. As radiation is used, this scan can be harmful for those who are pregnant and/or breast feeding.²

3D Echocardiogram

The 3D echocardiogram is a relatively new diagnostic imaging technique. It is used to create a real-time 3D image of your heart without using any ionising radiation. However, it has many limitations: it is very expensive, and skilled staff are needed to take and analyse the images. Despite this, medical practitioners are trying to incorporate 3D echocardiography into regular practice. It is used to help treat a variety of structural and functional heart anomalies.¹⁰

Contrast echocardiography

Like a normal echocardiogram, contrast echocardiography uses sound waves from an ultrasound to visualise the heart - but also uses a contrast agent to enhance the image. These tests are used to help measure the function of the left ventricle (one of the chambers of your heart). They visualise the interaction of microscopic gas bubbles (produced by the agitation of saline by your heart) with an ultrasound to create a better image of the heart and its surrounding structures. It is mainly indicated for coronary artery disease, myocardial infarction, and chronic ischemic heart disease.¹¹

Summary 

Heart scans are crucial for the early detection of cardiac conditions and allow doctors to visualise the heart and its surroundings. This article provides an overview of various common types of heart scans, including:

• The ultrasound-based echocardiogram for structural and blood flow insights 
• Cardiac computed tomography (CT) scans for 3D imaging
• Single-photon emission computed tomography (SPECT), which uses gamma rays and radiotracers
• Cardiac positron emission tomography (PET), which is used to quantify the heart’s metabolism
• The coronary CT angiogram, which is commonly used to detect artery blockages 
• The non-invasive cardiac MRI, which utilises radio waves and magnets
• The multifaceted acquisition (MUGA) scan, which measures your heart’s ejection fraction using a radiotracer
• The relatively new 3D echocardiography and contrast echocardiography tests

It is important to consult your healthcare providers about these tests to ensure you both gain a comprehensive understanding of your heart health. To gain a deeper understanding of your cardiovascular health, your healthcare provider might recommend a range of tests. It is essential to have regular, timely scans for good cardiovascular health. 

FAQs

How should I prepare for a heart scan?

Depending on the scan, there are multiple things the doctor advises. Ensure that you follow their instructions. These scans are done regularly, so there is nothing to worry about. 

How should I prepare for a cardiac MRI?

There are several important things to keep in mind before having a MRI:

• Remove all metal objects from your skin, clothes and pockets. 
• Inform the doctor about the medical implants you may have.

Are there any risks involved during cardiac scans?

These scans are safe and performed by trained professionals. Safety measures are prepared to avoid problems and mitigate any unforeseen accidents.