How is coronary heart disease traditionally diagnosed?

“If a patient is suffering from chest pain – and coronary heart disease (CHD) is suspected – they will usually be referred to a Rapid Action Chest Pain Clinic at their local hospital, where they can be seen quickly and assessed by a specialist team of nurses and doctors.

"One of the first tests they will undergo is usually a CT scan of the heart to look for obvious narrowing and blockages in the coronary arteries.

"A CT scan can pinpoint healthy, free-flowing arteries and serious blockages very clearly. However, there is always a large number of cases where the arterial problems are subtler, and the cardiologist can’t be sure – looking at the patient’s scan – if there are dangerous blood flow restrictions that require stent treatment or surgical intervention, or whether medication will be enough to control the condition.” 


So what happens to patients when their CT scans are inconclusive?

“If significant coronary (heart artery) narrowing is suspected, but not confirmed after a CT scan, the next step is usually a 'functional' test, where the heart is put under stress – usually with medication – and then examined with ultrasound or radioactive tracer or, in many cases, an invasive angiogram. 

“Performed under local anaesthetic, an angiogram involves feeding a catheter into the heart through an artery in the wrist or groin under local anaesthetic. A special dye is then injected through the catheter into the coronary arteries. An x-ray will then highlight any blood vessels that are narrowed or blocked. This procedure can be performed as day surgery but, as with all surgical procedures, it can be uncomfortable and stressful for the patient and comes with obvious risks.”


Are there diagnostic techniques that are not so invasive?

“Yes. HeartFlow Analysis is a new, non-invasive diagnostic tool that is designed to reduce the need for invasive, exploratory tests. It’s an incredibly sophisticated technology that combines the data from the patient’s initial CT scan through deep learning, highly-trained analysts and cutting edge cardiovascular research, to create a personalised, digital, 3D model of the patient’s coronary arteries.

"The programme can then pinpoint and colour code, vessel by vessel, the impact any narrowing or blockages are likely to be having on an individual patient’s blood flow. 

"The patient doesn’t need to have a special appointment for this procedure and does not undergo any additional risk by having this analysis done - we simply send the CT scans off to the lab in the US for assessment by secure transfer. The results usually come back to us within just a few hours.” 


It all sounds incredibly high tech - but how helpful is it really?

“Research, and our experience of using the technique at NHS Frimley Health Foundation Trust, over the last six months has shown that this non-invasive diagnostic technique is extremely useful and has helped cut the number of patients going for invasive exploratory procedures by roughly two thirds.

"Because we can reveal arterial problems without invasive tests with this technology, we are now using angiograms more often as a precursor to surgery, piggy-backing them with surgical procedures such as putting in stents - so everything is done in one operation. This saves time and money for the hospital and significantly reduces stress, discomfort and risk for our patients.”


Why does Frimley have access to this service - while other hospitals don’t?

"When the National Institute for Health Care Excellence (NICE) assessed this product last year - they were very impressed. But despite the fact it has a huge amount of very creditable research* behind it, it still has to be trialled very carefully by a few NHS hospitals before it can be rolled out nationwide. 

More than 20 NHS trusts are using this tool at the moment, and Frimley was one of the first. We are carefully monitoring everything to see how successful it is, and exactly which type of patient can benefit most from it.”


*Links to a wide range of clinical research into HeartFlow can be found at



Dr Peter Clarkson is the Cardiology Lead Consultant at NHS Frimley Health Foundation Trust in Surrey. He holds private practicing privileges at the Surrey Cardiovascular Clinic, Guildford and Spire Clare Park Hospital in Crondall, Farnham. His interests include General Adult Cardiology, Coronary Intervention/Stenting, permanent pacemaker and Complex Device Therapy.