Munich, Germany—The Third Universal Definition of Myocardial Infarction, which was developed by 4 major cardiology societies, was presented at the 2012 Congress of the European Society of Cardiology (ESC), by Kristian Thygesen, MD, Professor, Aarhus University Hospital, Denmark. Dr Thygesen is Cochair of the Global Myocardial Infarction Task Force that developed this document and was involved with developing the previous definitions.
The definition of myocardial infarction (MI) provides information for the diagnosis of patients, as well as end points in clinical trials, which have had tremendous heterogeneity of the definition of MI, thereby limiting the ability to appropriately compare outcomes data across trials. Standardizing the definition of MI for clinical trial end points is necessary, because these trials are used to develop clinical practice guidelines.
Focus on Biomarkers and Imaging
The key drivers for updating the definition of MI are the increasingly sensitive markers of myocardial necrosis, especially troponin, and more refined imaging techniques, including electrocardiogram (ECG) changes.
“We have always had to go for a more biochemical approach,” said Dr Thygesen. “Biomarkers could detect necrosis, which was always difficult with an ECG. So, in this latest definition, the concept of MI has not changed, but the diagnosis is now based on patient symptoms, ECG changes, highly sensitive biochemical markers, and information gleaned from various imaging techniques.”
The third universal definition was developed jointly by the ESC, the American College of Cardiology (ACC), the American Heart Association (AHA), and the World Heart Federation. The first universal definition was developed in 2000 by the ESC and ACC because of the emerging role of biomarkers in accurately reflecting the pathology, and all 4 societies developed the second definition, which was published in 2007.
Notably, the third universal definition includes additions related to percutaneous coronary intervention (PCI), coronary artery bypass graft (CABG) surgery, cardiac and noncardiac surgery, and clinical trials. New definitions in the document include:
- Definition to differentiate MI types 1 and 2 according to condition of the coronary arteries
- New definition of MI in patients undergoing cardiac procedures (eg, transcatheter aortic valve implantation, ablation, MI), MI associated with noncardiac procedures, MI in the intensive care unit, and associated with heart failure (HF)
Definitions for clinical trial end points.
Updates in the document include:
- Criteria of acute MI, including identification of intracoronary thrombus by angiography or autopsy
- Information on elevations of cardiac troponin levels from myocardial injury
- Definition of MI types 1, 2, 3, 4a, and 4b
- ST-segment elevation criteria that are age- and sex-specific
- Tabulation of MI types with multiples of the 99th percentile of troponin values
- Definition of reinfarction, recurrent MI, and silent MI.
“There has been some confusion about how to define MI, because the new biomarkers are so sensitive that they are seen in many conditions besides MI, thus a new way to put the new biomarkers into perspective was needed,” said Robert O. Bonow, MD, a member of the Global Myocardial Infarction Task Force and spokesperson for the AHA. Dr Bonow is the Goldberg Distinguished Professor of Cardiology, Vice Chairman of the Department of Medicine and Director of the Center for Cardiovascular Innovation at Northwestern University Feinberg School of Medicine, Chicago, IL.
Dr Bonow noted the possible concern of the overdiagnosis of MI, because the high-sensitivity biomarkers could be elevated in other conditions, such as HF or cardiomyopathies, where there may be a steady low-grade, long-term release of troponin. In contrast, a suspected MI should have a pattern of troponin over time, where it increases and then decreases.
The Third Definition of MI will also be useful after PCI or CABG, because the standardized definition for the postprocedure level of troponin will help to distinguish between a true complication of the procedure and a standard type of change that occurs in the heart muscle after blood flow is restored.
In addition, this definition is important epidemiologically, stated Dr Bonow, so “good data can be developed in the United States and globally for the prevalence of MI,” and to help identify whether strategies to prevent MI are effective.
The Third Universal Definition of MI is being published simultaneously by the European Heart Journal, Journal of the American College of Cardiology, Circulation, Global Heart, and Nature Reviews Cardiology.