Mills NL, Newby LK, Zaman S, et al; ESC/ACC/AHA/WHF Universal Definition Document Advisory Group. Fifth Universal Definition of Myocardial Infarction (2026).
The old Type 1–5 numbering was accurate but not usable at the bedside. The new document replaces it with three categories tied directly to pathophysiology.
The Fourth Universal Definition (2018) classified MI into five numbered types based on underlying mechanism. As ACC/AHA co-chair Kristin Newby put it in the ESC's own release, clinicians in practice rarely used terms like "type 2" or "type 4c" in conversations with patients — the numbering was precise for research and coding but opaque at the bedside. The Fifth UDMI, jointly authored by ESC/ACC/AHA/WHF and endorsed by EACTS and STS, collapses this into three categories — primary, secondary, and procedure-related — mapped to new ICD-11 codes. This is genuinely new: it was first presented at ESC Congress 2026 on August 30, and the post being audited went up almost immediately after.
Slides 2, 3, 5, and 6 of the carousel accurately reflect the published document.
| Category | Definition | Roughly maps to |
|---|---|---|
| Primary MI | Spontaneous presentation due to a primary acute coronary pathology — typically plaque rupture/erosion with thrombosis | Former Type 1 |
| Secondary MI | Results from myocardial oxygen supply–demand imbalance due to another acute condition (anemia, hypoxemia, shock, arrhythmia, vasospasm, embolism) | Former Type 2 |
The fundamental diagnostic requirement the carousel states on slide 5 — acute myocardial injury (troponin rise/fall with at least one value above the 99th-percentile URL) plus objective evidence of acute ischemia — is stated correctly, and the injury-vs-infarction distinction on slide 6 (elevated troponin alone = injury; injury + ischemia evidence = infarction) matches the document's own framing precisely.
Slide 4 says the opposite of what the new guideline actually did.
"Procedure-related MI occurs in association with a coronary revascularization procedure or its complications and requires specific biomarker thresholds together with appropriate clinical, ECG, imaging or angiographic evidence."
Multiple independent summaries of the same guideline (JACC full text, HCPLive's coverage of the ESC presentation) state this plainly: "It no longer relies on a cardiac biomarker threshold." The diagnosis is now based on a suspected coronary complication within 30 days of a cardiac procedure, plus acute myocardial injury on troponin measurement, plus at least one clinical or ECG feature (ischemic symptoms, new ischemic ECG changes, or unexplained sudden deterioration under sedation) — not a specific fold-elevation cutoff.
This is a deliberate, explained change, not an oversight in the new document. The old Fourth-Definition thresholds (troponin >5× URL for type 4a, >10× URL for type 5) were, in the task force's own words, arbitrary. A large prospective international study cited in the new document found that 97.5% of patients undergoing cardiac surgery already exceed 10× the URL — meaning the old "type 5" threshold flagged almost everyone. The same study found you'd need a threshold over 218× the URL (95% CI 40–318) to actually identify patients at meaningfully increased risk of peri-procedural mortality. That's the evidence base behind dropping the fixed-multiple biomarker threshold entirely in favor of the injury-plus-clinical-feature approach.
Slide 5 describes the 99th-percentile URL generically. The actual document specifies sex-specific 99th-percentile upper reference limits for cardiac troponin, explicitly to correct systematic under-recognition of myocardial injury in female patients under a single uniform threshold. This is one of the document's more consequential practical changes and isn't in the carousel at all.
Not mentioned anywhere in the eight slides: the term MINOCA is updated from "myocardial infarction with non-obstructive coronary arteries" to "myocardial injury with non-obstructive coronary arteries" — recognizing it as a working diagnosis rather than a final one. Any patient subsequently confirmed to have a true infarction should be reclassified into primary, secondary, or procedure-related based on the underlying cause.
The carousel's closing summary slide is accurate and worth keeping as the quick-reference version.
| 4th UDMI (2018) | 5th UDMI (2026) |
|---|---|
| Type 1 — Atherothrombosis | Primary MI — acute coronary pathology |
| Type 2 — Supply–demand imbalance | Secondary MI — supply–demand imbalance |
| Type 3 — Sudden cardiac death | Reclassified as primary, secondary, or procedure-related once evaluated, per Section 7 |
| Type 4 (4a/4b/4c) — PCI-related MI | Procedure-related MI — same criteria regardless of percutaneous vs. surgical approach, no fixed biomarker multiple (see Section 03 above) |
| Type 5 — CABG-related MI |
The one addition worth making to this summary slide: Type 3 (sudden cardiac death) doesn't map to a single new category the way Types 1, 2, 4, and 5 do. The new document handles it by defining objective criteria for diagnosing MI after sudden death, then reclassifying the case as primary, secondary, or procedure-related based on the underlying circumstances once that evaluation is complete — it's a diagnostic pathway, not a fourth category sitting alongside the other three.
Reproduced in full from the carousel; this table is a direct, accurate lift from the guideline's own Table 2 and is worth keeping as a standalone reference.
| Mechanism | Condition |
|---|---|
| Ischaemia | Myocardial infarction |
| Inflammation | Myocarditis (autoimmune, infectious, toxic) |
| Heart transplant rejection | |
| Cytokine mediated in sepsis | |
| Haemodynamic stress | Supply–demand imbalancea |
| Tachy- or brady-arrhythmia | |
| Acute heart failure | |
| Acute pulmonary embolism | |
| Malignant hypertension | |
| Physiological stress | Strenuous exercise |
| Catecholamine stress | Takotsubo syndrome |
| Subarachnoid haemorrhage | |
| Stroke | |
| Epileptic seizures | |
| Phaeochromocytoma | |
| Toxicity | Anthracyclines |
| ErbB (erythroblastic oncogene B)-targeted therapies | |
| Tyrosine kinase inhibitors | |
| Immune checkpoint inhibitors | |
| Radiation induced | |
| Trauma | Electrical cardioversion |
| Percutaneous coronary or structural intervention | |
| Catheter ablation or device implantation | |
| Cardiac surgery | |
| Cardiac contusion |
This is the practical payoff of the whole reclassification: "myocardial injury" is the umbrella, and ischaemia (i.e., actual infarction) is only one of six listed mechanisms that can elevate troponin. The other five — inflammation, haemodynamic stress, physiological/catecholamine stress, toxicity, and trauma — can all produce a positive troponin without any infarction at all. Reading this table alongside Section 02 above is the fastest way to internalize why the document repeatedly warns against diagnosing MI from a troponin value in isolation.
This is a fast, largely accurate summary of a document that was published days before it. The structural framing — primary/secondary/procedure-related replacing the numbered types, the injury-vs-infarction distinction, the two-step diagnostic logic, and the closing old-vs-new summary slide — all hold up against the actual Eur Heart J/JACC text. The one correction worth remembering is the opposite of what slide 4 states: procedure-related MI in the Fifth Definition explicitly moved away from fixed biomarker-multiple thresholds, for evidence-based reasons the old thresholds couldn't support. If you're updating personal notes or a teaching slide from this carousel, that's the line to fix first, and the sex-specific troponin threshold, the MINOCA redefinition, and the Type 3 reclassification pathway are worth adding.