Research
Half of those all-clear for angina in scan may be misdiagnosed
Half of people investigated for suspected angina and given the all-clear may be missing out on the correct diagnosis, based on a study funded by us, published in the journal Nature Medicine, and presented at the American Heart Association Scientific Sessions conference in New Orleans.
The study involved 250 British people referred for a coronary angiogram after experiencing chest pain. Based on their scan results, these people did not have angina - the medical term for pain or tightness within the chest caused by reduced blood flow to the heart.
However, when researchers gave these people an extra MRI scan, they found 51 per cent of people given the all-clear for angina actually had a form of it called microvascular angina. This is triggered by tiny blood vessels which can’t be seen using a standard coronary angiogram - where a thin tube is inserted into the wrist and up to the coronary arteries and an X-ray taken. The angiogram can only detect angina caused by blockages in the large coronary arteries.
Researchers say blood flow scans should be used to follow up angiograms for every patient with unexplained chest pain, but that many regions of the UK do not currently offer this.
Could diagnose thousands
Professor Colin Berry, senior author of the study from the University of Glasgow, said: “Further tests like the scan we used could help to reveal thousands more people with microvascular angina in the UK every year. Microvascular angina is currently particularly under-diagnosed in women.
“We need these extra test results because people whose angiogram results suggest their chest pain is not heart-related can be sent home without medication, on the assumption that their symptoms are due to things like indigestion, anxiety or arthritis.
“It is not uncommon for these people to then have to return to their GP multiple times, with continuing symptoms like chest pain and breathlessness.”
'Cardiac syndrome X'
Angina is a symptom of chest pain which can be caused by blockages or narrowing in the large coronary arteries which supply most blood to the heart. Microvascular angina used to be known as ‘cardiac syndrome X’ because it greatly confused doctors seeing patients with angina-like chest pains who didn’t have the expected narrowings or blockages in their coronary arteries.
Now the name, coined in the 1970s, is no longer used because experts understand that the pain is caused by tiny arteries within the heart muscle – less than half a millimetre across - which play a crucial role in regulating blood supply to the heart. Women are more likely to have the condition than men, particularly around and after the time of menopause.
Among the 250 people studied, all but six were judged to have chest pain that wasn’t heart-related based on their angiogram results. But the MRI scan found 123 of these people had microvascular angina – a diagnosis which is very clearly heart-related.
The scan detects microvascular angina, which reduces blood flow to the heart, by showing inadequate blood supply after people are given a drug called adenosine, which mimics the demands of physical activity on the body. In the study, half of the 250 people were offered altered treatment based on their MRI scan result, if needed. Such treatment could include calcium channel blockers, which relieve angina and lower blood pressure, and aspirin and statins, which reduce their risk of heart attacks and strokes. This group were examined to see how receiving a new diagnosis, following further tests after a coronary angiogram, might change people’s lives.
A better quality of life
Researchers found quality of life was better for people whose treatment was changed based on their scan, compared to those whose treatment was not changed following their scan. This group also saw a bigger reduction in the frequency of their chest pain – from weekly to monthly on average. They had a larger reduction in their difficulty doing everyday activities, based on a questionnaire.
A second questionnaire looked at people’s mobility, pain and discomfort, anxiety and depression and difficulties washing, dressing and performing normal daily activities. This also showed a greater improvement for people whose treatment changed based on their MRI scan.
There is some evidence that having microvascular angina may increase the risk of having a heart attack or stroke, although this wasn’t seen in the 12-month period people were followed up in the study.
People whose treatment was changed based on their MRI scan were found to have lower blood pressure, which may have been brought down by medications they were prescribed. They also had a lower weight, which researchers believe may have been a result of reduced chest pain making it easier to be active.
Serious impact on lives
Dr Sonya Babu-Narayan, clinical director at the British Heart Foundation and consultant cardiologist, said: “Coronary microvascular dysfunction, which is seen more commonly in women, is real. It can have a serious impact on people’s everyday lives, as they struggle with chest pain and breathlessness, and is often misunderstood.
“Unfortunately, many people go undiagnosed, are misdiagnosed, or are only diagnosed after years of delay, because the diagnosis of inadequate blood supply in tiny coronary blood vessels slips through the net.
“This important study shows that it doesn’t have to be this way – having heart MRI tests improved chest pain diagnosis, which in turn led to changes in treatment and better health.”
There were 127 people diagnosed with microvascular angina, including 123 whose angiogram had wrongly suggested their pain was not heart-related. The angiogram diagnosis that their chest pain was not heart-related appeared correct for 155 people.
The MRI scans used in the study revealed two people judged not to have heart-related chest pain by an angiogram, who in fact had hypertrophic cardiomyopathy – a genetic condition which can cause a life-threatening abnormal heart rhythm. Another two people had myocarditis – inflammation of the heart muscle which most people recover from following treatment.
There are around 250,000 coronary angiograms performed across the UK every year. The MRI scans in this study were done at the Golden Jubilee University National Hospital in Clydebank, within the west of Scotland.
These scans judged blood flow in the blood vessels of the heart, and included an algorithm assessing the difference in flow between the inner and outer area of the heart, which is not routinely available on the NHS. However researchers say conventional MRI scans would have a largely similar performance.
On how the study results should change NHS practice, Professor Berry added: “An angiogram alone is not enough for most people with suspected angina, but in most regions of the UK this is all that is performed.
“People should be offered an additional test to look at blood flow. That does not need to be an MRI scan like ours, as there are several alternative tests which might be helpful. These tests are needed because debilitating chest pain significantly reduces people’s physical and mental wellbeing, and their ability to go about their everyday lives.”
