The Fifth Universal Definition of Myocardial Infarction (MI) released on behalf of a joint task force from the ACC, European Society of Cardiology (ESC), American Heart Association (AHA) and World Heart Federation (WHF) provides a new clinical classification of MI that is based on pathophysiology, aligns with clinical evaluation of patients and incorporates objective diagnostic criteria.

Published in JACC, highlights from the updated definition include:

• Refined criteria for acute and chronic myocardial injury that emphasize underlying mechanisms and support the use of sex-specific cardiac troponin thresholds to improve diagnostic accuracy, particularly in women.
• Replacement of the numerical classification of MI with three clinical classifications: 1) Primary MI; 2) Secondary MI; and 3) Procedure-related MI.
• New, objective criteria for silent or unrecognized MI.
• An updated definition of MINOCA to "myocardial injury with nonobstructive coronary arteries." According to the authors, this revision reflects the view that MINOCA should be considered a working diagnosis rather than a final diagnosis.
• The introduction of accelerated diagnostic pathways using high-sensitivity cardiac troponin assay.
• Guidance on the diagnosis of MI in low-resource settings.
• Proposed ICD-11 codes to help align with the updated classification of MI and encourage continued implementation and research.

"The definition incorporates sex-specific cardiac troponin thresholds to avoid systematic bias and underdiagnosis in female patients," says L. Kristen Newby, MD, FACC, the ACC/AHA co-chair of the updated document. "The use of imaging is encouraged to define the etiology of MI, and this will support more personalized care, recognizing that treatment differs depending on the underlying cause and setting in which it occurs."

"One of the objectives of this update in the classification is to improve consistency in the application of the diagnosis of MI in clinical practice and clinical research so that the findings from research can be readily adopted into practice, allowing for improved epidemiological research and between-country comparisons," the authors said.

The document, which replaces the definition published in 2018, was developed by a multidisciplinary panel of experts representing 12 countries across five continents.