Less common heart attacks, which mainly affect women, are more likely to be diagnosed and treated correctly, under new international guidance unveiled at the European Society of Cardiology Congress in Munich.
The Fifth Universal Definition of Myocardial Infarction, influenced by decades of research funded by the British Heart Foundation, and developed by the four major cardiac societies, has a new focus on three types of heart attacks mostly experienced by females. It encourages doctors to perform an angiogram for patients who have had a suspected heart attack, to ensure these less common types are diagnosed.
This is hoped to improve diagnosis rates, and ensure people are given the best treatments, rather than unnecessary medications which may make the problem worse. The change could transform the care of tens and thousands of women in the UK, and many more globally.
The types of heart attack expected to be diagnosed more commonly following the change in definition include coronary artery spasm – tightening of a heart artery which can deprive the heart muscle of blood and oxygen and cause a heart attack, and which can be caused by emotional stress, exercise or extreme cold.
Another type is a heart attack caused by a coronary embolism, where a blood clot or foreign body, such as a fatty deposit, travels to a coronary artery and causes a blockage.
The third less common type of heart attack, also principally affecting women, is a coronary artery dissection (SCAD) - 80 per cent of which happen to women, and which can happen during, or soon after, pregnancy. This is where a tear suddenly appears in the wall of a coronary artery, which supplies blood to the heart.
"Deprioritised"
The three types are all now classed as 'primary' heart attacks. Previously they were classed as 'type 2' heart attacks, because a clot did not cause them. Some experts say this meant they were 'deprioritised'.
Among those welcoming the new definition is Allison Lawson, who had a heart attack caused by a SCAD 'out of the blue' when she was 51. It was following a cup of coffee with a neighbour that Allison started feeling very tired, before feeling a strange discomfort in the middle of her chest, then pain which spread down her left arm and up into her jaw. Within half an hour, she was being rushed to hospital in an ambulance.
Allison spent three days in the cardiac intensive care unit (CICU) following her heart attack in September 2024, and said: "The environment was surreal - machines beeping, nurses checking vitals, and me lying there trying to make sense of it all.
"I was completely drained, physically and emotionally. I felt like I’d been hit by a truck."
The financial assessment officer, from Saxilby in Lincolnshire, had never heard of a heart attack caused by a SCAD. She hopes the Fifth Universal Definition of Myocardial Infarction will lead to greater awareness, and potentially faster diagnosis for others in her situation.
She said: "For me, diagnosis was vital - before I knew what this was, I felt absolutely terrified by the lack of knowledge about what had happened to me. If the new heart attack definitions could help more people get an accurate and speedy diagnosis, it would really change things."
Step forward
The new definition groups less common types of heart attack with 'traditional' heart attacks often seen as the most severe. This should lead to more research helping to better understand the causes of these less common heart attacks, and new medical guidance for them which guarantee patients get the best treatment.
Importantly, the new definition also states that primary heart attacks should be confirmed using an angiogram. This is a test providing a picture of the blood vessels leading to the heart which helps to detect heart attacks caused by SCAD, coronary artery spasm and coronary embolism, which will ensure people get the right diagnosis and treatment.
Currently, some people who had a heart attack caused by a coronary artery spasm may be prescribed beta blockers when they should really be getting vasodilator tablets. Those with a heart attack caused by a coronary embolism may be given a statin when they should get a strong blood thinner, and people who had a SCAD heart attack could get a statin or blood-thinner, when it would instead be better to manage their blood pressure.
Adoption of the new guidance is hoped to prevent people getting less effective treatments, which do not target the cause of their heart attack and may make them more unwell.
The new classification of heart attacks is designed to be clearer for people who have had them, so they can fully understand what has happened. Heart attack survivors helped to review the new guidance and provided feedback and suggestions.
The three new categories of heart attack replace a numerical classification which was previously used by doctors. Secondary heart attacks, like previous type 2 heart attacks, are still heart attacks which are triggered by other illnesses, which put the body under stress so that the oxygen someone breathes in cannot meet the demands of their heart. But the new definition is more precise, and again emphasises that people should have imaging, such as an echocardiogram – an ultrasound scan of the heart – or an angiogram to confirm or rule out their diagnosis.
The third new category of heart attack is one caused by a cardiac procedure, such as a stent being inserted or coronary artery bypass surgery, and happens within 30 days of that procedure. This diagnosis of a procedure-related heart attack replaces the previous categories of type 4a-c and type 5 heart attacks, and is aimed at explaining the risk of heart attacks to patients undergoing medical interventions, so that they can weigh up the risks and benefits.
"Back to basics"
Professor Nicholas Mills, BHF Professor of Cardiology at the Centre for Cardiovascular Science, within the University of Edinburgh, helped lead the international taskforce of clinicians who devised the new heart attack definition. For the first time, it has been agreed between the European Society of Cardiology (ESC), the American College of Cardiology (ACC), the American Heart Association (AHA) and the World Heart Federation (WHF).
Professor Mills said: "This new definition, achieved following decades of research, is an attempt to go back to basics in defining heart attacks. These categories should importantly be easily understandable by the people who have had a heart attack, and ensure they receive the treatment which is best for them, and fits the cause of their heart attack.
The new definition also requires hospitals to differentiate between men and women when testing for troponin – the protein that the heart muscle releases into the blood when it is damaged, which can confirm if someone has had a heart attack.
Professor Mills, supported by funding from the British Heart Foundation, has conducted several studies showing that women have lower levels of troponin than men. Given troponin can signal a heart attack, it is important that different thresholds are used to avoid bias and the under-recognition of heart attacks in women. This happens routinely in the NHS, and Professor Mills hopes that will now be the case worldwide.
The taskforce behind the new heart attack categories is working with the World Health Organisation, arguing that its disease definitions should be changed too. With new definitions for heart attacks such as those caused by a SCAD, experts hope there will be better data on these less common conditions, leading to studies which reveal new insights.
The new guidelines are published in the European Heart Journal.
"Landmark moment"
Our chief scientific and medical officer, Professor Bryan Williams, said:
“This is a landmark moment – a radical shift in how we define and diagnose heart attacks worldwide which will transform people’s care.
"For decades, women have missed out on accurate diagnoses and treatment. This focus on finding less common causes of heart attacks, which predominantly affect women, should help to change that. It could be lifechanging for huge numbers of women in the UK and worldwide."