Four Major Heart Health Organizations Agree on the First Universal Definition of a Heart Attack
The world's four leading cardiovascular health organizations have agreed on the first universal definition of a heart attack, announced on August 28, 2026, in Munich on the opening day of the European Society of Cardiology's annual congress. The consensus document, formally titled the Fifth Universal Definition of Myocardial Infarction (2026), was issued jointly by the ESC, the American College of Cardiology (ACC), the American Heart Association (AHA), and the World Heart Federation (WHF) (Guardian; ESC).
Prof Nicholas Mills, a cardiologist at Edinburgh University, led the international taskforce that produced the new guidelines. The ESC's own press release states that the definition aims to improve diagnosis, treatment, and patient understanding of myocardial infarction (ESC press release).
The classification restructures how heart attacks are categorized. The most serious cases previously known as "type 1" are now classed as "primary" heart attacks. Under the new framework, secondary myocardial infarction is defined as acute myocardial ischemia (reduced blood flow to the heart) and injury secondary to an alternative acute condition — meaning the heart attack is a consequence of another medical event rather than the primary problem (AHA Journals). The full classification system divides myocardial infarction into types, giving clinicians a standardized taxonomy for distinguishing the underlying mechanisms of injury (ESC guidelines page).
One of the most consequential changes in the new guidance concerns sex-specific diagnostic thresholds. The guidelines lower the troponin threshold required for diagnosing a heart attack in women compared to men. Troponin is a protein released into the bloodstream when cardiac muscle is damaged, and it has long served as the principal biomarker — a measurable indicator in the blood — for myocardial injury. Applying a single threshold across both sexes has been associated with underdiagnosis in women, whose baseline troponin levels tend to be lower. The revised thresholds aim to close that diagnostic gap (Guardian).
The guidance also upgrades three types of heart attack that are disproportionately seen in women: coronary artery spasm, coronary embolism (a blockage caused by a traveling clot), and spontaneous coronary artery dissection (SCAD), which involves a tear in the artery wall. SCAD occurs in women at least 80 percent of the time and frequently presents during or soon after pregnancy. By formally incorporating these mechanisms into the universal definition, the taskforce brings conditions that have historically sat at the margins of myocardial infarction classification into its central framework (Guardian).
Prof Bryan Williams, chief scientific and medical officer of the British Heart Foundation, described the new definition as a landmark moment and a radical shift in how heart attacks are defined and diagnosed (Guardian). Notably, the AHA's newsroom, which published a June 29, 2026 release on the companion Second Universal Definition of Heart Failure, had not issued its own standalone announcement of the heart attack definition as of the date of the Munich congress (AHA newsroom).
The heart attack definition is not the only consensus document the four societies have produced this year. On June 29, 2026, the ESC, ACC, AHA, and WHF also released the Second Universal Definition of Heart Failure (2026) as an expert consensus document, developed in collaboration with the Heart Failure Society of America (HFSA), the Heart Failure Association (HFA), and the Japanese Heart Failure Society (JHFS). The AHA described that document as refining and updating how heart failure is identified and classified (AHA newsroom; AHA Journals).
The broader context here is one of long-standing diagnostic inconsistency. Myocardial infarction has been defined and redefined iteratively, with each successive universal definition refining the role of biomarkers, imaging, and clinical criteria. The absence of a single, globally endorsed definition meant that a patient meeting diagnostic criteria in one jurisdiction might not meet them in another. This fragmented landscape had implications not only for individual patient care but for the comparability of clinical trials, epidemiological surveillance, and health-system performance metrics across borders.
The sex-specific elements of the new definition address a well-documented gap in cardiovascular medicine. Women presenting with myocardial infarction have historically been more likely to receive a delayed or missed diagnosis, partly because clinical algorithms and biomarker thresholds were derived predominantly from male populations. The decision to lower troponin thresholds for women and to formally elevate SCAD, coronary artery spasm, and coronary embolism within the classification reflects an effort to align diagnostic criteria with the actual epidemiology of these events across sexes.
ESC 365 has scheduled sessions dedicated to the new definition, including one titled "5th Universal Definition of Myocardial Infarction: new clinical classifications" on October 14, 2026, and a presentation on October 15, 2026, suggesting that implementation and dissemination will extend well beyond the Munich announcement (ESC 365; ESC 365 presentation).
The practical test of the new definition will come as hospitals and national cardiology societies decide whether and how to integrate the revised thresholds and classifications into local clinical pathways, electronic health record systems, and guideline documents. Consensus at the international level does not automatically translate into uniform practice at the bedside, and the adoption lag for prior universal definitions has typically measured in years rather than months. What the Fifth Universal Definition provides is a common reference point. Whether clinicians and health systems use it as such is the question that now matters.
