Four Major Cardiac Societies Unveil Simplified Global Definition of Heart Attack

Four of the world's largest cardiac organizations have agreed on a new way to define and classify heart attacks, replacing a system so complicated that doctors often abandoned it in practice. The European Society of Cardiology, the American College of Cardiology, the American Heart Association, and the World Heart Federation unveiled the Fifth Universal Definition of Myocardial Infarction on August 30 at the ESC Congress 2026. The shift matters because how a heart attack is classified shapes how it gets treated—and until now, the terminology was so tangled that clinicians rarely used it when talking to patients about what had happened to them.

Myocardial infarction is one of the most common cardiovascular conditions globally. It affects 3.8 percent of people under 60 and 9.5 percent of those 60 and older. It remains a leading cause of death and a persistent public health burden across every region. Yet the previous universal definition, which relied on a numerical system to sort different types of heart attacks, created problems in real clinical settings. Doctors found it difficult to apply consistently, which meant patients in different hospitals or countries could receive different diagnoses and treatment plans for essentially the same event. The new framework was designed to fix that fracture between what the textbooks said and what actually happened at the bedside.

The old system used numbers—type 2, type 4c, and so on—that were precise in theory but cumbersome in practice. Nicholas Mills, chair of the ESC and a professor at the University of Edinburgh, explained that most people think of a heart attack as a simple thing: a blocked artery. In reality, he said, there are many different causes. The new definition acknowledges this complexity while making it legible. Instead of numerical categories, the framework sorts all heart attacks into three clinical settings based on what caused them.

Primary myocardial infarction occurs spontaneously because of an acute problem in a coronary artery. Most commonly, this happens when an atherosclerotic plaque ruptures. But it can also result from a tear in the coronary wall, called spontaneous coronary artery dissection, or from spasm or a clot. Secondary myocardial infarction arises from an imbalance between the heart's oxygen supply and demand, triggered by another condition—severe high or low blood pressure, or a very rapid heartbeat. The third category, procedure-related myocardial infarction, occurs within 30 days after a cardiac procedure like coronary stenting or a bypass surgery. Every heart attack now fits into one of these three boxes, and the new document specifies which diagnostic tests and investigations are needed for each.

The practical benefit for patients is immediate. Kristin Newby, chair of the ACC and AHA and a professor at Duke University Medical Center, noted that clinicians rarely used the old numerical terminology when explaining things to patients because it was too abstract. With the new approach, doctors can now discuss the actual cause of a patient's heart attack in plain language. A patient can understand whether their heart attack happened because of a blocked artery, because their body's oxygen balance went wrong, or because of a procedure they underwent. That clarity matters for compliance, for understanding what comes next, and for recognizing why further tests and treatments are necessary.

The new definition also aligns with the International Classification of Diseases coding system, which is how health systems worldwide track disease patterns and outcomes. This is significant because it means the same classification will be used for both clinical care and public health statistics. Sarah Zaman, chair of the World Heart Federation and an associate professor at the University of Sydney, explained that the organizations worked with the World Health Organization to propose ICD-11 codes that match the updated MI classifications. Implementation will take time, she said, but the payoff will be substantial: better public health monitoring, more consistent healthcare system planning, and standardized data collection that will enable large-scale research into areas where knowledge is still thin.

One example is spontaneous coronary artery dissection, a less common cause of primary heart attack that occurs predominantly in women and is currently underdiagnosed. Better coding and classification could make it easier for researchers to identify patterns, understand risk factors, and improve recognition in clinical practice. The task force chairs concluded that by simplifying the classification system, they hope to make a heart attack diagnosis more meaningful and consistent, to better guide treatment decisions, to deepen patient understanding, and to open new pathways for monitoring and research across the global medical community.