Heart CT scans: a peek into the future

Since their accidental discovery by a German physicist in 1895, X-rays have revolutionised medicine by making it possible for the first time to ‘see’ inside the body.

Then in the 1970s, X-ray technology took on a whole new dimension when Sir Godfrey Hounsfield came up with the idea of computed tomography (CT) scanning.

In CT scans, the X-ray beam moves in a circle to take many different images, which are then combined to form one 3D image.

Today, CT scans are in wide use. When used to look at the heart and its blood vessels they can help to diagnose heart problems, or spot who is at higher risk of heart conditions.

What’s CT coronary angiogram?

There are two different types of heart CT scan. One is called a CT coronary angiogram (CTCA), which shows the structure of the coronary arteries that supply blood to your heart.

It shows narrow areas in these arteries that may mean you have coronary artery disease, resulting from the build-up of fatty deposits in the artery wall. These deposits, called plaques, can cause chest pain (angina) and lead to a heart attack.

Before CTCAs, doctors could only use standard angiograms to look at the coronary arteries. A standard angiogram involves a thin tube, called a catheter, being put into a blood vessel via the wrist or groin, and then guided up into the heart to look for blockages in the coronary arteries.

Both the standard angiogram and a CTCA involve an iodine-based dye, called a contrast, being injected into your blood so that your coronary arteries show up under X-rays.

But unlike a standard angiogram, a CTCA does not need a catheter to be inserted into the heart, so it’s safer and more comfortable.

The scan takes only a few minutes and provides detailed images of the heart and its arteries.

Since 2016, UK guidelines have recommended CTCA as one of the first tests for someone experiencing new chest pain that may be caused by coronary artery disease. The results of a trial funded by the Chief Scientist Office of Scotland and supported by British Heart Foundation (BHF), fed into these guidelines.

The trial called SCOT-HEART was led by BHF Professor David Newby from the University of Edinburgh. It involved over 4,000 people with suspected angina who were referred to rapid access chest pain clinics in Scotland.

Participants were randomly split into two groups: one group had standard care, and the other had standard care, plus a CTCA.

The researchers found that the rate of future heart attacks was almost halved in the group that had a CTCA. They think this is probably because people in this group were started earlier on preventive treatments, such as statins.

What’s CT calcium scoring?

CT calcium scoring is a simpler CT scan that does not require any contrast dye. It measures the amount of hardened (calcified) plaques in the arteries.

A higher calcium score indicates a higher number of plaques, and, therefore, a greater risk of having a heart attack.

BHF-funded researchers have helped to show that CT calcium scoring can also be used to assess the severity of narrowing of the aortic heart valve (aortic stenosis).

A study found that using different calcium score thresholds for men and women with aortic stenosis more accurately identified who had severe disease, and so would benefit most from surgery to replace the aortic valve.

How could heart CT scans be used in the future?

BHF is funding research into how heart CT scans can be used to improve the prevention, diagnosis and treatment of heart issues, including using them to:

Rule out serious heart problems after chest pain

Most people attending A&E with chest pain have a blood test to measure troponin, a protein released into the blood when the heart muscle is damaged.

If this rules out a heart attack, many people will be discharged without further tests or treatment.

However, even if the troponin levels do not indicate a heart attack, some people may have coronary artery disease that could lead to a heart attack in the future. It’s not currently clear how these people should best be treated and care varies widely. 

BHF Professor Nick Mills at the University of Edinburgh is leading a BHF-funded clinical trial that aims to address this uncertainty. The trial called TARGET-CTCA is looking at whether using a highly sensitive troponin test to identify people who should have a CTCA scan could help diagnose coronary artery disease earlier and prevent future heart attacks.

The trial has enrolled 3,170 people who went to hospital with chest pain and had moderate levels of troponin in their blood – not high enough to indicate a heart attack, but enough to suggest possible damage to the heart. Half the people taking part received standard care, where their GP decided on further treatment based on current guidelines.

The other half were referred for a CTCA to look for any blockages in their coronary arteries. The research team reviewed the scan results and based on these they sent a report to the patient’s GP recommending whether any treatment was needed.

This could be a statin to reduce their cholesterol levels, or an antiplatelet agent such as aspirin to help prevent clots forming in the coronary arteries.

Participants in the trial are now being followed up for an average of three years to see whether using troponin testing and CTCAs together in this way helps to prevent future heart attacks or deaths from heart-related issues.

The results are expected in 2025 and could improve care for people who attend hospital with chest pain.

Better predict heart attacks

Doctors currently estimate a person’s risk of a future heart attack based on their age, gender and risk factors. This is called a risk score: if it’s high, they may suggest lifestyle changes or statins to help lower the risk of future heart problems.

BHF’s Professor Newby is now leading a new trial, which is called SCOT-HEART 2, to test whether CT heart scans could be used to better identify people who are most at risk of coronary heart disease and would benefit from preventative measures.

The research team are aiming to enrol 6,000 people aged 40 to 70 in Scotland, who do not currently have heart problems but are at risk. For example, people with high blood pressure or diabetes, which are both risk factors for heart disease.

Participants will have their risk score calculated and will then be randomly split into two groups. Half will have the current standard risk score-based treatment, and the other half will have a CT heart scan (including a CTCA and a CT calcium score) that will be used to help doctors decide their treatment.

Participants will be tracked for up to 10 years to monitor the number of people who go on to have a heart attack.

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