Four of the world's leading cardiology societies — the ESC, ACC, AHA, and World Heart Federation — have jointly released the Fifth Universal Definition of Myocardial Infarction (MI), replacing the old numerical classification system that was frequently misapplied in clinical practice. The new framework sorts all heart attacks into three straightforward categories: primary (spontaneous, due to acute coronary pathology), secondary (triggered by oxygen imbalance from another acute illness), and procedure-related (linked to cardiac procedures). The simpler language is designed to improve clinician communication and patient understanding alike.

The update also tackles longstanding gaps in equity and precision. Sex-specific troponin thresholds are now standard, addressing the systematic underdiagnosis of MI in women, who naturally have lower troponin levels. Spontaneous coronary artery dissection (SCAD) — which disproportionately affects young women — is now explicitly recognized as a distinct primary MI mechanism. MINOCA has been redefined as "myocardial injury with nonobstructive coronary arteries," reinforcing that it's a starting point for diagnosis, not a conclusion.

Key Takeaways:

• New ICD-11 codes for each MI type will, for the first time, enable tracking of rare causes like SCAD, vasospasm, and embolism
• Sex-specific troponin cutoffs aim to close the gender gap in MI diagnosis
• SCAD, found in nearly 90% of women among those diagnosed, now has its own distinct classification and ICD-11 code
• Imaging is emphasized as central to confirming diagnosis and guiding etiology-specific treatment

Why it matters: The previous numerical MI classification led to misclassification in nearly half of type 1 MI patients. This new globally endorsed framework aims to standardize care, fuel research into underexplored MI types, and ensure no heart attack goes unrecognized.