Fifth Universal Definition of MI Unveiled at ESC 2026

MUNICH, Germany—For the first time in 8 years, cardiology societies around the world have come together to define what constitutes a heart attack. The new Fifth Universal Definition of Myocardial Infarction (UDMI) comes with many updates related to underlying pathology and more closely matches how cardiologists evaluate patients with suspected MI.

The standards, which replace the Fourth UDMI, from 2018, were published online in the European Heart Journal and elsewhere to coincide with their release at the recent European Society of Cardiology (ESC) Congress 2026. In a team effort, the updated UDMI was developed jointly by the ESC, American College of Cardiology (ACC), American Heart Association (AHA), and World Heart Federation (WHF). It was endorsed by the European Association for Cardio-Thoracic Surgery (EACTS) and the Society of Thoracic Surgeons (STS).

Representing a diverse swath of specialties, the organizations “got together to arrive at a consensus as to how we diagnose and classify what is still the number one cause of death in the world,” Nicholas L. Mills, MD, PhD (University of Edinburgh, Scotland), the ESC chairperson of the Fifth UDMI, said during a press conference.

“What we’re trying to do is to change the way we communicate with patients,” Mills said. The idea is to give “clear guidance as to what’s caused their heart attack so that they have a better understanding, and hopefully we start to tailor the treatment that matters to the underlying cause in a way that has been difficult to do in the past.”

L. Kristin Newby, MD (Duke University, Durham, NC), the ACC/AHA co-chairperson, noted that the Fifth UDMI’s classification of myocardial infarction usefully aligns with how cardiologists already work in clinical practice. “It doesn’t really change at all how we see a patient, what our diagnostic testing is. But it brings in some new rigor, if you will, with regard to functional consequences of the myocardial infarction,” she told the media.

AHA President Manesh Patel, MD (Duke University), commenting on the new UDMI for TCTMD, predicted the changes “will make a huge difference” in the field. “The prior Universal Definition was certainly valuable,” he said, but its classification was built on numbers, which can be hard to remember and conceptualize. The current version instead uses descriptors that are “very straightforward and understandable,” Patel noted. 

Importantly, too, the Fifth UDMI standardizes these terms across not only professional societies but also across the patients cardiologists frequently encounter, he added. “It’s very clinically understandable.”

What’s Changed

As the document notes, the MI definitions in prior iterations of the UDMI “were major advances, though some aspects remained difficult to apply consistently in practice.” This was especially the case for MI arising from a condition apart from atherothrombosis or periprocedural MI that occurs after either PCI or cardiac surgery, its authors say.

In the Fifth UMDI, MI types are no longer categorized by number but instead as three clinical profiles:

• Primary (formerly type 1): all acute coronary pathologies, including atherothrombosis, spontaneous coronary artery dissection, coronary embolism, and vasospasm, as well as restenosis, stent thrombosis, or graft failure > 30 days from a procedure
• Secondary (formerly type 2): myocardial oxygen supply/demand imbalance due to an alternative acute condition and obstructive CAD without acute coronary pathology and/or new or presumed new regional wall motion abnormality or absence of viable myocardium
• Procedure-related (formerly type 4 and 5): coronary complication within 30 days of a cardiac procedure resulting in acute myocardial injury with one or more features. Both features are required when the complication arises during the procedure or in the setting of acute MI: evidence of a coronary complication of percutaneous intervention or cardiac surgery and new or presumed new regional wall motion abnormality or absence of viable myocardium

What had been type 3, referring to MI-related cardiac death that occurs before diagnostic testing, is no longer its own category but falls among the three above depending on its clinical classification.

Additionally, the Fifth UDMI has refined criteria for acute and chronic myocardial injury, with sex-specific thresholds for cardiac troponin. This latter aspect will hopefully “avoid systematic bias and the underrecognition of both myocardial infarction and other cardiac conditions associated with myocardial injury in female patients,” the authors point out.

Other new sections address the diagnosis of MI after sudden death, objective criteria for silent or unrecognized myocardial infarction, and accelerated pathways and advice for how to interpret high-sensitivity cardiac troponin assays. As TCTMD has reported, the letter I in MINOCA has shifted, too, from “infarction” to “injury” with nonobstructive arteries “in recognition that this is a working rather than final diagnosis,” the paper notes.

Finally, a key feature of the latest UDMI is that the clinical categories now line up with the International Classification of Disease 11th Revision (ICD-11) codes. These are used for tracking in-hospital events and monitoring public health. 

It brings in some new rigor, if you will, with regard to functional consequences of the myocardial infarction. L. Kristin Newby

Sarah Zaman, MBBS, PhD (University of Sydney, Australia), the WHF co-chairperson, said that the task force worked closely with the World Health Organization to ensure the various types of MI are concordant with specific ICD-11 codes.

“Now we have a number of coronary pathologies or basically different causes for heart attacks,” she noted, so having an ICD-11 code for each will allow researchers to better identify how often each of those MIs occur. Zaman highlighted the diagnostic code that, for the first time, specifies when spontaneous coronary artery dissection is the cause of MI. This will “enable us to study it, and we might finally get some treatment in this space,” she said.

Concordance with the ICD-11 codes is important in several ways, as highlighted in the paper: “Use of high-sensitivity cardiac troponin assays has increased the recognition of myocardial injury and, together with adoption of the Fourth UDMI, has led to an increase in the diagnoses of type 1 and type 2 myocardial infarction by 11% and 22%, respectively. However, as the Fourth UDMI was not aligned with the ICD-10 edition codes, this increase has not been reflected in morbidity and mortality data.”

This gap has “presented health system challenges when myocardial infarction has been incorrectly assigned to patients with nonischemic causes of acute myocardial injury,” the authors write.

Zaman further highlighted the fact that procedure-related MIs now are defined the same regardless of whether they occur in connection to PCI or CABG. “So for the first time we can directly compare them and in that way a patient can have a bit more of an informed consent about which procedure they want to undertake, because it will be a fair and equitable comparison,” she commented.

For Newby, it’s also noteworthy that the definition is “not totally dependent on a biomarker level.” So, if clinicians encounter a complication, they can first assess the biomarkers and then proceed to assessing the “functional consequences of that through echocardiography or cardiac magnetic resonance imaging,” she said.

Ajay Kirtane, MD (NewYork-Presbyterian/Columbia University Irving Medical Center, NY), however, told TCTMD he sees both pros and cons to the Fifth UDMI.

“I think it’s great that they’ve tried to unify many of these definitions. They’ve made it more clinically applicable in that there’s now ICD-11 linkage, and there’s also simplification pathophysiologically,” he commented.

But Kirtane did question the bar set for defining periprocedural MI. In some ways, it’s the right approach, he said, “in that you didn’t want to overdiagnose MI by having an abnormal biomarker, particularly high-sensitivity troponin, without some corroborating clinical information. That’s good—whatever your troponin is does not [automatically] make it a periprocedural MI,” he agreed.

Yet requiring a wall motion abnormality or absence of viable myocardium could overlook some events, Kirtane stressed.

For example, “there are scenarios where a side branch can close, the biomarker would be elevated, there could be EKG changes, but nobody [orders] an echo. And that would not be clearly listed as a periprocedural MI,” he explained, adding that this presents a “conundrum” for clinical events committees. 

“I wish it had said if you have an angiographic complication with other clinical evidence, that’s enough to call it a periprocedural MI, especially if your biomarker’s elevated. . . . I don’t think it’s a good thing to miss those types of events,” Kirtane said. “They fixed so many other items [from prior UDMIs] with such an admirable effort, it’s just a pity that they couldn’t fix this last one.”