The New Heart Attack Definition Recodes Women’s Missed Cases

Four global heart groups published a new heart attack definition on 28 August 2026 that recodes the attacks women get most. The Fifth Universal Definition of Myocardial Infarction drops the old type 1 to type 5 labels and requires sex-specific troponin cutoffs.

Emergency labs, hospital codes, and the treatments that follow those labels still have to change for the paper to alter who leaves hospital alive.

Heart Attacks Now Split Into Three Clinical Types

The document is a joint statement from the European Society of Cardiology, the American College of Cardiology, the American Heart Association, and the World Heart Federation. It was issued as ESC Congress opened in Munich and is due on the main auditorium stage on 30 August. Prof Nicholas Mills of the University of Edinburgh chaired the ESC side of the task force.

People still picture a heart attack as a clot blocking an artery, Mills told the ESC press office, but many different causes starve heart muscle of blood. The 2018 Fourth Definition sorted those causes into numbered types that were hard to use at the bedside. The 2026 rewrite puts every infarction into one of three clinical settings: primary, secondary, or procedure-related.

Primary means the problem started in a coronary artery. Plaque rupture is still the most common trigger, and the document now places spontaneous coronary artery dissection, artery spasm, and embolism in that same primary group. Secondary means another acute illness, such as very high or very low blood pressure or a very fast heartbeat, created a supply and demand mismatch. Procedure-related means the damage came within 30 days of a stent or a bypass operation.

NEW 2026 #ESCGuidelines – Fifth Universal Definition of Myocardial Infarction (2026) 👇https://t.co/EzBQZfDp0W#ESCCongress pic.twitter.com/6V3HzQpdWS

— European Society of Cardiology (@escardio) August 28, 2026

THE OLD LABELS AND THE NEW ONES

In emergency and intensive care, a high troponin during sepsis or shock can no longer be stamped as a secondary heart attack by default. The new rules ask whether the patient has injury only, a true secondary infarction, or a primary coronary event unmasked by the illness, and that call now depends on the ECG, serial troponin, and imaging.

The Old Type 2 Bucket Hid Women’s Attacks

The three causes pulled into the primary group are far more common in women, and SCAD is the clearest example. About 80% of SCAD cases are in women, and many occur during pregnancy or soon after birth. The 2026 text says SCAD should be considered in particular in female patients under 50 and in the pregnancy and postpartum window.

Grouping those non-atherosclerotic coronary causes with oxygen supply-demand imbalance as type 2 “has limited its adoption in practice,” the task force wrote in the European Heart Journal. Those patients follow different diagnostic paths and need different treatment. A spasm, a tear, and a travelling clot are not the same disease as a plaque rupture, and they are not the same as a troponin rise in a patient with pneumonia.

That sorting error sat on top of a wider gap in ordinary clot-driven attacks. The British Heart Foundation says about 33,000 women are admitted with a heart attack each year in the UK, one woman every 16 minutes. Coronary heart disease still kills twice as many UK women as breast cancer.

THE CARE GAP THE NEW LABELS ARE MEANT TO CLOSE

• Wrong first diagnosis: Women had a 50% higher chance than men of an incorrect initial diagnosis after a heart attack, in a BHF part-funded study of 564,412 patients.
• STEMI and NSTEMI: Women with a final STEMI diagnosis had a 59% greater chance of that first-pass error, and women with NSTEMI had a 41% greater chance.
• Death after the error: Men and women who were misdiagnosed had about a 70% higher risk of dying within 30 days than patients whose first label matched the final one.
• Equal-care estimate: A Leeds University analysis that the BHF part-funded put 8,243 deaths among women hospitalised in England and Wales in the preventable column if care had matched the standard men received.

Dr Sonya Babu-Narayan, associate medical director at the BHF, has said women are more likely than men to face delay or misdiagnosis, and that they are less likely to get stents, surgery, statins, and rehab. Prof Bryan Williams, the charity’s chief scientific and medical officer, called the Munich agreement a radical shift in how heart attacks are defined and diagnosed, with a focus on less common causes that predominantly affect women.

Why Women Need a Lower Troponin Line

Troponin is the protein that leaks into blood when heart muscle is injured. A heart attack diagnosis still needs a rise or fall in that protein plus evidence of ischaemia, such as symptoms, ECG changes, or imaging. The 2026 definition says sex-specific 99th percentile troponin limits now define myocardial injury, in order to avoid systematic under-recognition in female patients.

Healthy women run a lower 99th percentile than healthy men on high-sensitivity assays. In the High-STEACS programme Mills led in Scotland, myocardial injury was set at 16 ng/L in women and 34 ng/L in men on a high-sensitivity troponin I test. Mills has said the key blood test has been used at an average level that picks up all men and misses some women, in every emergency department that relies on it.

Dr Martha Gulati, a cardiologist who studies women’s heart disease, wrote after the congress that using the same cutoff in women and men can systematically underdiagnose injury in women. “Women’s heart attacks don’t always look like men’s. Our definitions finally reflect that,” she said.

WHERE EXPERTS DISAGREE

• The 2026 task force: Sex-specific 99th percentile upper reference limits should define injury, and the AHA summary lists that change among the core updates.
• High-STEACS investigators: Those limits identified five times more additional women than men with injury, yet women still got fewer coronary treatments and outcomes did not improve.
• A 2025 multicenter analysis of 7,137 patients: A uniform cutoff gave similar sensitivity in women and men, and sex-specific limits reclassified only 0.4% of patients, which led those authors to keep a shared number.

Adoption is already uneven. A 2024 survey of 663 laboratories in 76 countries found high-sensitivity troponin in 91.9% of labs, with sex-specific reference ranges used often for troponin I and much less often for troponin T. A definition can require the female line. A lab still has to load it into the analyser.

Finding More Injured Hearts Did Not Change Treatment

High-STEACS remains the largest test of what happens when hospitals actually switch on sex-specific cutoffs. The stepped-wedge trial enrolled 48,282 consecutive patients with suspected acute coronary syndrome across 10 hospitals, 47% of them women, and published the sex-specific analysis in the Journal of the American College of Cardiology in 2019.

Use of the high-sensitivity troponin I assay with those thresholds increased detected myocardial injury by 42% in women and by 6% in men. After that switch, women received about half the treatments men received for coronary disease. The primary outcome of recurrent infarction or cardiovascular death at one year did not fall in women.

HIGH-STEACS AFTER THE CUTOFF CHANGE

Kuan Ken Lee and colleagues wrote that women with injury remained less likely than men to undergo revascularization or to receive dual antiplatelet, statin, or other preventive therapy. The paper’s closing line still hangs over Munich: the assay identified five times more additional women than men with injury, and outcomes were not improved.

A lower diagnostic line can put more women’s names on the injury list. It does not automatically book the angiogram, load the dual antiplatelet, or start the statin. The 2026 document tries to close that gap by changing what the injury is called, not only where the lab draws the line.

SCAD, Spasm, and Clots That Travel

That is why the primary bucket matters for treatment, not just for paperwork. A classic type 1 attack from a ruptured plaque is treated with rapid reperfusion, stents, and blood thinners aimed at clot. SCAD is a tear in the artery wall. Most stable tears are managed conservatively because the vessel often heals, and putting a stent in can extend the dissection. Clot-busting drugs can worsen bleeding into the wall and are generally avoided.

Coronary spasm tightens the artery, sometimes after emotional stress, exercise, or extreme cold, and the first-line drugs are calcium channel blockers and nitrates rather than an emergency stent for plaque. Coronary embolism is a clot or fragment that travelled from elsewhere, so the work-up looks for a source such as atrial fibrillation or a valve problem instead of treating the artery as if it had local plaque rupture.

WHY THESE ATTACKS CANNOT SHARE A CLOT PROTOCOL

• SCAD: Conservative care is preferred when flow is preserved, because percutaneous intervention has a high rate of extending the tear, and pregnancy-associated cases more often present as STEMI involving the left anterior descending artery.
• Spasm: The artery can look open between episodes, so the diagnosis depends on recognising the mechanism rather than forcing a stent into a vessel that is not full of plaque.
• Embolism: The blockage arrived from somewhere else, so antiplatelet and anticoagulant choices follow the source, not a one-size plaque algorithm.
• Imaging: The 2026 text gives angiography, intravascular imaging, echo, and MRI a larger job in naming the cause, including in women under 50 and around pregnancy.

Mayo Clinic notes that women are more likely than men to have an attack with no severe blockage, and that they have heart attack symptoms more often at rest or even during sleep. Chest pain is still the most common symptom in both sexes. Nausea, unusual fatigue, and pain in the neck, jaw, or back are more often reported in women, which is one reason a first-pass diagnosis goes wrong before the troponin result is even read.

Prof Kristin Newby of Duke University Medical Center, the ACC and AHA chair for the document, said clinicians often skipped the old type numbers in conversations with patients because the labels were too complex. The new terms are meant to let a doctor say the cause out loud, so the next test and the next drug make sense to the person in the bed.

Hospitals Still Have to Recode Every Emergency Lab

Associate Prof Sarah Zaman of the University of Sydney chaired the World Heart Federation side of the task force. She said the group had worked with WHO on codes that match the new types, and that the payoff is public health monitoring and research on under-counted causes such as SCAD.

We have worked with the World Health Organization to propose ICD-11th edition codes that align with the updated MI classifications. While implementation will take time, it will result in better public health monitoring and healthcare system planning.

Sarah Zaman, WHF Chair, ESC press briefing, Munich

The European Heart Journal text maps primary infarction onto ICD-11 headings that split atherothrombosis, SCAD, coronary embolism, coronary vasospasm, and late restenosis. Those proposed ICD-11 codes with WHO are how a tear in a 34-year-old stops being filed as a vague type 2 event and starts being counted as a primary coronary attack. Until hospital episode statistics use those codes, research and staffing plans will keep under-counting the attacks this rewrite was written to find.

The document also adds accelerated high-sensitivity troponin pathways, rules for silent infarction, and a presumed diagnosis in low-resource settings where biomarkers and imaging are missing. A multidisciplinary panel from 12 countries across five continents wrote it. The European Association for Cardio-Thoracic Surgery and the Society of Thoracic Surgeons endorsed it, and the Society for Cardiovascular Angiography and Interventions gave an affirmation of value.

Mills said the job now is to implement the definition as widely as possible, in the UK and everywhere else. The last time his group changed only the blood cutoff, women still left hospital with fewer stents, fewer dual antiplatelet prescriptions, and fewer statins than men. The 2026 paper recodes the mechanism and drafts the ICD-11 line. The analyser in the emergency lab, the coder on the ward, and the team that offers the angiogram still have to use them.

Frequently Asked Questions

Which Journals Published the 2026 Heart Attack Definition?

The Fifth Universal Definition of Myocardial Infarction was published on 28 August 2026 as a joint statement and appeared at the same time in the European Heart Journal, Circulation, and the Journal of the American College of Cardiology. The writing chairs were Nicholas L. Mills for the ESC, L. Kristin Newby for the ACC and AHA, and Sarah Zaman for the World Heart Federation, with a panel drawn from 12 countries across five continents.

What Is MINOCA Under the New Rules?

MINOCA is now defined as myocardial injury with non-obstructive coronary arteries, and the task force treats it as a working diagnosis rather than a final one. The change is meant to stop teams from parking a patient under that label without naming the actual mechanism, which may still turn out to be spasm, SCAD, embolism, plaque disruption that was missed, or a non-ischaemic injury.

Why Do Female Troponin 99th Percentiles Run Lower?

A 2024 systematic review of 19 studies found lower female 99th percentiles than male and overall cutoffs in more than 90% of high-sensitivity troponin I assays, and in eight of nine troponin T studies. Roche’s later TSIX programme, reported in 2025, set sex-specific upper reference limits at 18 ng/L for females and 32 ng/L for males, with an overall limit of 27 ng/L, which is why a single shared number can sit above many women’s true 99th percentile.

How Common Is Myocardial Infarction in Younger Adults?

The ESC press briefing cited a 2023 systematic review and meta-analysis by Salari and colleagues that put the global prevalence of myocardial infarction at 3.8% in people younger than 60 and 9.5% in people older than 60. Those figures are for the condition as a whole, not for SCAD or spasm alone, and they are one reason the task force also wrote diagnostic guidance for hospitals that lack troponin assays and cardiac imaging.

Does Procedure-Related Infarction Still Use a Fixed Troponin Multiple?

The 2026 definition keeps procedure-related infarction as events within 30 days of a percutaneous or surgical cardiac procedure, but it moves away from treating a fixed troponin multiple after PCI or bypass as diagnostic on its own. The authors noted that post hoc analyses had shown varying procedure-related criteria changing reported infarction rates across trials, and the update tries to make those trial endpoints comparable.

Disclaimer: This article is news reporting and analysis of a published medical definition, and it is for information only. It is not medical advice, a diagnosis, or a treatment plan for chest pain, heart attack symptoms, pregnancy-related symptoms, or any other complaint. Anyone with possible heart attack symptoms should seek emergency care, and readers should consult a qualified physician or cardiologist before changing tests, medicines, or follow-up. Figures, cutoffs, and coding proposals reflect the sources as of 1 September 2026 and may change as hospitals, laboratories, and WHO coding schedules adopt the document.