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Thousands of patients admitted to hospital every year with suspected heart attacks could avoid an unnecessary invasive procedure if they have a routine heart MRI scan first, according to research led by the Radcliffe Department of Medicine.

MRI scanner from the control room, with two members of staff © Martin Phelps

The study is presented at the British Cardiovascular Society conference in Manchester and published in the Journal of American College of Cardiologists (JACC) Cardiovascular Imaging.

There are around 50,000 hospital admissions every year in the UK due to suspected NSTEMI heart attacks (where the coronary arteries that supply the heart with blood are severely narrowed but not completely blocked). Currently, guidelines recommend that patients who are considered at risk of further events have an invasive coronary angiogram within 72 hours.

Fifth of patients could avoid invasive angiogram

Now, researchers at the University of Oxford have shown that performing a heart MRI scan before their angiogram in suspected NSTEMI patients could change how doctors treat at least half of patients. The results suggest that around a fifth of patients could avoid having an invasive coronary angiogram altogether as, in the study, their scans revealed that other heart problems were the cause of their symptoms, rather than a heart attack.

Dr Mayooran Shanmuganathan, Consultant Cardiologist and Research Fellow in the Radcliffe Department of Medicine led the study. He said: ‘While this was a small study in one hospital, if we find similar results in a larger multi-centre trial it could help thousands of patients every year to avoid an invasive procedure that will not benefit them. We now need to test this non-invasive approach on a bigger scale, by using heart MRI scans to guide treatment decisions in patients suspected to have NSTEMI heart attack to determine its cost-effectiveness and the impact it has on longer-term clinical outcomes.’

An invasive coronary angiogram involves inserting a small tube (called a catheter) into an artery and guiding it up to the heart. This allows doctors to look inside a patient's coronary arteries (which supply the heart with blood) to check for narrowing or blockages and plan treatment. While common and straightforward, the procedure has about a one per cent risk of complications including bleeding and strokes.

As part of the Oxford Acute Myocardial Infarction (OxAMI) study, researchers recruited 100 patients admitted to hospital with a suspected NSTEMI heart attack. Each patient was treated according to current clinical guidelines, but before their invasive coronary angiogram they also underwent a heart MRI scan. The clinicians reading the scan and performing the angiogram made their diagnoses separately, without knowing the results of the other procedure.

MRI scans revealed other heart problems as cause of symptoms

Coronary angiograms showed that 27 of the patients with a suspected NSTEMI heart attack did not have any major narrowing or blockages in their arteries. The heart MRI scans of 18 (two thirds) of these patients showed either a normal heart or that other conditions (such as myocarditis and Takotsubo cardiomyopathy) were the cause of the problem.

The researchers say that other courses of investigation, such as a CT scan of the coronary arteries, would have been suggested before an invasive coronary angiogram for this group, had their heart MRI been used to plan their treatment.

Over two thirds (67 per cent) of the patients admitted with a suspected NSTEMI heart attack had evidence of a heart attack on their heart MRI scan. However, a scan would probably still have changed treatment decisions for many of these patients.

Scans from 15 patients revealed they likely had a STEMI (a type of heart attack where a coronary artery is completely blocked). Their heart MRI scans suggested that these patients may have presented late and therefore may not have benefitted from having a stent fitted. In another seven patients, heart MRI scans suggested that narrowing within a different coronary artery was responsible for symptoms rather than the one fitted with a stent.

Scan-first approach could prevent risk of complications

Dr Sonya Babu-Narayan, Associate Medical Director at the British Heart Foundation and consultant cardiologist, said: ‘With an ageing and increasingly unhealthy population, along with ongoing disruption to the health system and the effects of covid-19 on the cardiovascular system, the number of people with heart disease in the UK is set to increase. It’s vital that we can get everyone on a path to receive the tests and treatment they need as quickly as possible to save and improve more lives.

‘Invasive procedures like coronary angiograms will continue to have a crucial role in heart care, delivering important treatments such as stents that can help to save lives and stop future heart attacks. But if the results of larger trials are positive, this scan-first approach could help doctors to identify patients who don’t stand to benefit, allowing them to avoid the small but important risk of complications.’

This research was funded by the British Heart Foundation and the National Institute for Health and Care Research (NIHR) Oxford Biomedical Research Centre.