Cardiology societies drop numbered heart-attack types and set lower troponin bars for women

The world's main cardiology bodies have rewritten the definition of a heart attack. The Fifth Universal Definition of Myocardial Infarction, issued on Friday in Munich at the opening of the European Society of Cardiology congress, drops the numbered Types 1 through 5 and replaces them with three clinical classes: primary, secondary and procedure-related.

The document is published in the Journal of the American College of Cardiology and the European Heart Journal on behalf of a joint task force of the ESC, the American College of Cardiology, the American Heart Association and the World Heart Federation. It is endorsed by the European Association for Cardio-Thoracic Surgery and the Society of Thoracic Surgeons.

The change that will reach casualty departments first is the blood test. Sex-specific 99th percentile upper reference limits for cardiac troponin now define myocardial injury. Until this edition, many laboratories applied a single threshold to men and women. Women have lower circulating troponin on average. Using the male cut-off meant a share of female patients never crossed the line that triggered a heart-attack diagnosis, even when their hearts were damaged.

The task force states the point without dressing it up. The new limits are there to avoid systematic bias and the under-recognition of infarction and other injury in female patients.

The old numbering system treated a clot on a ruptured plaque as Type 1 and bundled most other mechanisms into Type 2 or left them in a grey zone. The new primary class covers a spontaneous presentation caused by an acute coronary problem. Secondary infarction covers cases in which something else in the body throws off the heart's oxygen balance. Procedure-related infarction covers damage tied to surgery or intervention. Silent or unrecognised infarction now has objective criteria of its own.

Three mechanisms that are far more common in women have been pulled into the main diagnostic path: coronary artery spasm, coronary embolism, and spontaneous coronary artery dissection, known as SCAD. Those events are often linked to childbirth, intense exercise or emotional stress. Under the previous scheme they were easier to miss or to treat as less urgent than a classic plaque rupture. The guidance also updates MINOCA. The term now reads myocardial injury with nonobstructive coronary arteries, a wording that covers injury as well as frank infarction when the arteries look clear on the angiogram.

The task force has proposed ICD-11 codes to match the new classes so that hospital records, insurance claims and research datasets can follow the same map. That is the piece that will decide whether the rewrite stays on conference slides or changes who gets a bed, a stent and a discharge diagnosis.

Women account for about a third of acute infarctions and tend to present eight to ten years later than men. Their symptoms more often sit outside the textbook chest crush. ST-elevation thresholds on the ECG already differ by sex in leads V2 and V3. The new troponin rule extends that logic into the laboratory.

The definition does not invent a new disease. It changes the gate. A woman whose troponin sits below the old unisex line and whose angiogram shows spasm or a tear rather than a blocked artery is now supposed to be counted, classified and treated as a heart-attack patient. Hospitals that keep using a single troponin cut-off will be working against the document that the four societies have now signed.

Implementation will vary by country and by assay. High-sensitivity troponin kits already carry sex-specific reference ranges. The test for the next year is whether emergency departments print those ranges on the result slip and whether coders stop forcing every case into the old Type 1 box. The paper gives them a new box to use.