A new global definition of myocardial infarction (MI) has been devised by a task force of four major cardiology societies, with the goal of enabling cardiologists and other healthcare professionals to better diagnose and treat patients with the condition.

The previous universal definition relied on a numerical system that was often challenging to apply to clinical practice, leading to discrepancies in diagnosis and treatment, according to the task force. The updated and simplified classification system for MI, they explained, aims to address these constraints.

The new categories are:

• primary, arising spontaneously due to an acute coronary pathology
• secondary, caused by oxygen imbalance in the setting of another acute medical illness
• procedure-related, occurring in the setting of percutaneous or open surgical cardiac procedures

“These classifications reflect the underlying pathophysiology, align with clinical care, and enable application in clinical practice,” said L. Kristin Newby, MD, co-chair on the joint task force.

Imaging is emphasized to confirm diagnosis, establish underlying etiology, and lend functional significance to the diagnosis, said Newby, of the Duke University School of Medicine in Durham, North Carolina. “This will lead to more precise treatment based on the setting and underlying etiology of the MI classification,” she said.

Because the classification is more intuitive, it will be easier to apply in practice and to enhance communication between clinicians and patients, she added.

The new definition, known as the Fifth Universal Definition of Myocardial Infarction, was presented at the European Society of Cardiology (ESC) Congress 2026 and published in the European Heart Journal. The task force consisted of the European Society of Cardiology, the American College of Cardiology, the American Heart Association, and the World Heart Federation.

Three Proposed International Classification of Diseases (ICD) Codes

A leading cause of death and one of the most prevalent cardiovascular conditions, MI is estimated to affect nearly 4% of people younger than 60 years and almost 10% of those older than 60 years.

The guideline proposes new ICD codes for each of the three new MI classifications, which will help support research opportunities, Newby said. For the first time, she said, healthcare professionals can determine how often MI occurs in the setting of another acute medical illness or in percutaneous or open surgical cardiac procedures.

“Since all acute coronary pathologies are now included in the primary MI category, and each has a unique ICD-11 code, we will be able to understand the incidence of less common etiologies like vasospasm, spontaneous coronary artery dissection (SCAD), and embolism,” Newby said. “We will then be able to use these codes to identify cohorts of patients for research studies that can help understand the life course of individuals with these illnesses and seek to develop new treatment approaches.”

SCAD, a fairly uncommon cause of MI compared with most cases of acute coronary syndrome, is disproportionately found in young women. A recent study found that women make up nearly 90% of patients diagnosed with SCAD.

The updated classification explicitly recognizes SCAD as a distinct acute coronary mechanism for causing primary MI, said Marysia S. Tweet, MD, an associate professor of medicine and director of the Women’s Heart Clinic in the Department of Cardiovascular Medicine in at Mayo Clinic, Rochester, Minnesota.

“Under the previous definition, SCAD was listed in the type 2 category, alongside conditions leading to oxygen supply-demand imbalance,” said Tweet, who was not a member of the task force.

“The updated distinction stresses the importance of identifying SCAD and distinguishing it from other causes of primary MI using the appropriate diagnostic tools, including coronary angiography and when necessary, intracoronary imaging,” she said.

New Definition of MINOCA

Another key change is the definition MINOCA, Tweet added. It’s now defined as myocardial injury with nonobstructive coronary arteries, rather than MI with nonobstructive coronary arteries.

“For cardiologists and other clinicians, this change reinforces that MINOCA is a working diagnosis, rather than a final diagnosis, thereby prompting further evaluation to identify the underlying cause of MI to determine etiology-specific treatment,” she said.

Nicholas L. Mills, PhD, of the British Heart Foundation Chair of Cardiology at The University of Edinburgh, Edinburgh, Scotland, pointed out that sex-specific troponin thresholds now define both acute and chronic myocardial injury.

“This resolves a systematic bias in care and will minimize the risk that MI, or other cardiac conditions associated with MI, are underdiagnosed in women who have lower troponin concentrations than men,” said Mills, co-chair of the task force. “This will help ensure that all presentations of acute MI are not missed, whether they are due to atherothrombosis or SCAD.”

Mills noted that there are key knowledge gaps that require further research. “In particular, new approaches are needed to identify those patients with possible secondary and procedure-related MI in whom cardiac and coronary imaging will change disease management,” he said. “Studies are also needed to evaluate intra-coronary and cardiac magnetic resonance imaging in patients when the etiology of primary MI is uncertain.”

Newby reported receiving research grant funding from Roche Diagnostics, Medtronic, and Boehringer Ingelheim, as well as consulting honoraria from Medtronic and Bristol Myers Squibb.

Mills reported receiving ongoing research funding (public/not-for-profit) from the British Heart Foundation Chair Award, Fellowships, the Research Excellence Award, and Programme Grant. His department/institution also received research funding from Roche Diagnostics. He reported serving as associate editor of the AHA journal, Circulation, for which he received a modest remuneration.

Tweet reported being supported by the National Heart, Lung, and Blood Institute and the National Institutes of Health. The Mayo Clinic SCAD Research Program is supported in part by SCAD Research, Inc., Carlsbad, California. She also reported serving as an associate editor for JACC: Advances.

Martta Kelly is a medical journalist who lives in the New York metro area.