2026 Fifth Universal Definition of Myocardial Infarction

The Fifth Universal Definition of Myocardial Infarction (MI) updates the classification of MI by defining three major clinical settings—primary MI, secondary MI, and procedure-related MI—to better reflect underlying pathophysiology, support clinical evaluation, and incorporate objective diagnostic criteria. Primary MI occurs spontaneously because of an acute coronary pathology; although most cases result from atherothrombosis, alternative coronary causes may be identified through coronary imaging and functional testing. Secondary MI results from another acute condition that causes an imbalance between myocardial oxygen supply and demand, with proposed objective criteria guiding the use of cardiac and invasive or noninvasive coronary imaging to promote consistent diagnosis and inform treatment. Procedure-related MI occurs as a complication of percutaneous or surgical cardiac procedures, and its diagnosis does not depend on cardiac biomarker thresholds, with comparable criteria applied across percutaneous and surgical interventions. Across all three settings, the updated definition provides guidance on interpreting symptoms and signs of myocardial ischemia, cardiac biomarkers, and imaging findings. It also addresses alignment with ICD-11 codes, distinguishes MI from myocardial injury, and considers implications for patients, public health, and research. Adoption of this classification in clinical practice and research is expected to make the diagnosis of MI more meaningful and provide clearer implications for patient care across healthcare settings. Source: https://www.jacc.org/