Fifth Universal Definition Reclassifies Myocardial Infarction

The Fifth Universal Definition of Myocardial Infarction, published in the Journal of the American College of Cardiology, replaces the previous numbered myocardial infarction (MI) types with a pathophysiology-based clinical framework. The document was developed by a joint task force representing the European Society of Cardiology, American College of Cardiology (ACC), American Heart Association, and World Heart Federation.

The revised framework classifies MI as primary, secondary, or procedure-related. Primary MI arises spontaneously from an acute coronary pathology. Secondary MI results from myocardial oxygen supply-demand imbalance associated with another acute condition. Procedure-related MI occurs as a complication of a percutaneous or surgical cardiac procedure.

The document also refines criteria for acute and chronic myocardial injury. Sex-specific cardiac troponin thresholds are incorporated to reduce systematic bias and under-recognition of myocardial injury and MI among women. Accelerated diagnostic pathways using high-sensitivity cardiac troponin assays are included, along with new objective criteria for silent or unrecognized MI.

The Fifth Universal Definition introduces new objective criteria for silent or unrecognized MI using ECG and cardiac imaging evidence to determine whether a prior MI occurred without a recognized acute clinical presentation.

The definition changes the expansion of MINOCA from “myocardial infarction with nonobstructive coronary arteries” to “myocardial injury with nonobstructive coronary arteries.” Guideline authors characterized MINOCA as a working diagnosis that requires further investigation to determine the underlying cause and final diagnosis. Coronary and cardiac imaging are encouraged to help establish the etiology of MI.

The document also provides diagnostic guidance for low-resource settings and proposes ICD-11 codes aligned with the revised categories. Developed by a multidisciplinary panel representing 12 countries across 5 continents, the update is intended to improve consistency in MI diagnosis across clinical practice and research, and support epidemiological research and international comparisons.

Sources: Mills NL, Newby LK, Zaman S, et al. Fifth universal definition of myocardial infarction (2026). J Am Coll Cardiol. Published online August 28, 2026. doi:10.1016/j.jacc.2026.07.025

American College of Cardiology. Global CV societies release updated universal definition of MI. American College of Cardiology; August 28, 2026. Accessed August 30, 2026.