Major cardiac societies develop and publish a universal definition of myocardial infarction

When a myocardial infarction, such as a heart attack, occurs, being able to classify its type can improve diagnosis and treatment. For the first time, a universal definition of myocardial infarction has been developed and published by four major cardiac societies: the European Society of Cardiology (ESC), the American College of Cardiology (ACC), the American Heart Association (AHA) and the World Heart Federation (WHF). The Fifth Universal Definition of Myocardial Infarction will be presented at ESC Congress 2026 on 30 August.

Myocardial infarction (MI) is one of the most common cardiovascular disorders, with an estimated prevalence of 3.8% in individuals aged less than 60 years and 9.5% in those aged over 60 years.3 MI remains a leading cause of death and is a significant public health concern worldwide.

People may think of an MI as a heart attack caused by a blocked coronary artery but there are many different causes of MI. The previous universal definition used a numerical system to categorize the different types of MI but this was not always easy to apply in clinical practice, leading to inconsistences in diagnosis and treatment. The ESC, ACC, AHA and WHF have worked together to devise an updated and simplified classification system for MI, which aims to address these limitations."

Professor Nicholas Mills, ESC Chair, University of Edinburgh, UK

The new system considers the underlying cause of the MI and aligns the diagnosis with established approaches to clinical evaluation. It recognizes that MI occurs in three clinical settings: primary MI, secondary MI and procedure-related MI. In this updated approach to MI classification, all MIs fit into one of these three clinical categories and the new document outlines the diagnostic tests and investigations that are required for each.

Primary MI is one that arises spontaneously due to an acute problem in a coronary artery. It is most commonly caused by a rupture of an atherosclerotic plaque, but there are other causes such as a tear in the coronary wall (spontaneous coronary artery dissection [SCAD]), spasm or a clot. Secondary MI arises from an imbalance in oxygen supply and demand in the heart caused by another condition, such as very high or very low blood pressure or a very fast heartbeat. The third setting – procedure-related MI – is one that occurs within 30 days of a cardiac procedure (such as coronary stenting) or heart operation (such as coronary artery bypass surgery).

Explaining what the new universal definition of MI means for patients, ACC/AHA Chair, Professor Kristin Newby from Duke University Medical Center, Durham, USA, said, "Clinicians often do not use the previous numerical terminology – e.g. type 2 or type 4c – in patient discussions as it is rather complex. With the new approach, we can now talk with patients about the cause of their MI so that they can understand their condition and recognize why the next steps, such as further tests and treatments, are needed."

In another first, the new universal definition of MI aligns with International Classification of Disease (ICD) coding, which captures statistics on the extent, causes and consequences of different diseases. WHF Chair, Associate Professor Sarah Zaman from the University of Sydney, Australia, noted: "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. Importantly, ICD-11 coding will also standardize data collection on each MI type, enabling further largescale research in areas of unmet need." As an example, the new alignment could facilitate wider study of less common mechanisms of primary MI, such as SCAD, a condition occurring predominantly in women, which is currently under-diagnosed.

The Task Force Chairs concluded: "By simplifying classification, we hope to make a diagnosis of MI more meaningful and consistent to better inform treatment, enhance patient understanding and improve opportunities for monitoring and research."