Fifth Universal Definition of Myocardial Infarction Replaces Numerical MI Type System

For the first time, a single universal definition of myocardial infarction (MI) has been jointly developed and published by the European Society of Cardiology (ESC), American College of Cardiology (ACC), American Heart Association (AHA), and World Heart Federation (WHF).¹

The Fifth Universal Definition of Myocardial Infarction (UDMI) replaces the numerical type 1 through 5 classification with three clinically defined categories, presented ahead of a dedicated session at European Society of Cardiology (ESC) Congress 2026 in Munich, Germany.¹,² The task force says the new system was designed for more consistent application across clinical practice, research, and public health reporting.¹

“People may think of an MI as a heart attack caused by a blocked coronary artery but there are many different causes of MI,” ESC Chair Nicholas Mills, BSc Hons MBChB PhD, from the University of Edinburgh, said in a statement. “The previous universal definition used a numerical system to categorise 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.”

Numerical MI typing, introduced with the Third UDMI and expanded in the Fourth UDMI in 2018, has remained difficult to apply consistently, particularly for infarctions arising from a non-atherothrombotic coronary process or occurring after a procedure.¹ The Fifth UDMI is a consensus statement, not a clinical practice guideline, and is intended to be applied alongside existing regional and national guidance.¹

Primary, Secondary, and Procedure-Related MI Classification

Under the new framework, every MI is categorized as primary, secondary, or procedure-related.¹ Primary MI covers spontaneous presentations due to an acute coronary pathology, now explicitly including atherothrombosis, spontaneous coronary artery dissection, coronary embolism, vasospasm, and late (> 30 days post-procedure) stent thrombosis, restenosis, or graft failure, which is reclassified as de novo disease rather than a procedural complication.¹

Secondary MI applies when myocardial oxygen supply-demand imbalance from another acute condition drives ischemia, confirmed by obstructive coronary artery disease without acute coronary pathology or by a new regional wall motion abnormality.¹

Procedure-related MI, replacing the former type 4 and 5 categories, is defined by a coronary complication within 30 days of a percutaneous or surgical cardiac procedure.¹ It no longer relies on a cardiac biomarker threshold and now applies the same criteria across percutaneous and surgical settings.¹

Troponin Criteria, MINOCA Update, and ICD-11 Alignment

The task force refined criteria for acute and chronic myocardial injury, now requiring sex-specific 99th percentile upper reference limits for cardiac troponin.¹ According to the statement, uniform thresholds systematically under-recognize myocardial injury in female patients, and the sex-specific approach is intended to correct this bias across both myocardial infarction and other injury-associated cardiac conditions.¹

The definition of myocardial injury with non-obstructive coronary arteries (MINOCA) is also updated, with the term now referring explicitly to a working diagnosis in patients presenting with features of possible MI who are found to have non-obstructive coronary arteries, replacing prior language referencing “myocardial infarction” rather than “myocardial injury.” The task force states most patients ultimately carry a non-coronary cardiac or non-cardiac diagnosis, and any patient subsequently confirmed to have MI should be reclassified as primary, secondary, or procedure-related based on the underlying setting.¹

The document also introduces accelerated diagnostic pathways using high-sensitivity cardiac troponin assays and new objective criteria for silent or unrecognized MI and for diagnosis following sudden death.¹

The task force worked with the World Health Organization to propose International Classification of Diseases 11th Revision (ICD-11) codes aligned with the updated categories.¹ WHF chair Sarah Zaman, MBBS, PhD, University of Sydney, said the ICD-11 alignment will standardize data collection by MI type once implemented. “Importantly, ICD-11 coding will also standardise data collection on each MI type, enabling further largescale research in areas of unmet need,” she said.

Kristin Newby, MD, ACC/AHA co-chair from Duke University Medical Center, said the numerical typing was rarely used directly in patient conversations because of its complexity.¹ “With the new approach, we can now talk with patients about the cause of their MI so that they can understand their condition and recognise why the next steps, such as further tests and treatments, are needed,” Newby said.¹

The Fifth UDMI also adds dedicated guidance for adapting diagnosis in low-resource settings without ready access to coronary or cardiac imaging, and outlines implications of the revised classification for research design going forward.¹

References:

1. Mills NL, Newby LK, Zaman S, et al. ESC/ACC/AHA/WHF Universal Definition Document Advisory Group. Fifth universal definition of myocardial infarction (2026): on behalf of the joint European Society of Cardiology (ESC)/American College of Cardiology (ACC)/American Heart Association (AHA)/World Heart Federation (WHF) Task Force for the Universal Definition of Myocardial Infarction. Circulation. 2026;154:e00-e00. doi:10.1161/CIR.0000000000001477

2. European Society of Cardiology. New global definition of myocardial infarction aims to improve diagnosis, treatment and patient understanding. Published August 28, 2026. Accessed August 28, 2026. https://www.escardio.org/news/press/press-releases/new-global-definition-of-myocardial-infarction-aims-to-improve-diagnosis-treatment-and-patient-understanding/