The Third MI Definition: An Expert Interview With Joseph Alpert

Linda Brookes, MSc; Joseph S. Alpert, MD


October 26, 2012

An Expert Interview With Joseph S. Alpert, MD

About the Interviewee

Dr. Alpert is Professor of Medicine and Director of Coronary Care at the University of Arizona College of Medicine at Tucson. He is board-certified in internal medicine and cardiovascular disease. Dr. Alpert has authored 48 books and monographs and more than 600 publications, including original articles, book chapters, reviews, and editorials. He is editor-in-chief of The American Journal of Medicine.

Dr. Alpert is cochair of the Joint European Society of Cardiology (ESC)/American College of Cardiology Foundation (ACCF)/American Heart Association (AHA)/World Heart Federation (WHF) Task Force for the Universal Definition of Myocardial Infarction, which produced both the 2012 and 2007 definitions of myocardial infarction. Dr. Alpert is also the lead coauthor of the 2012 Third Universal Definition of Myocardial Infarction (MI), which was published simultaneously in the European Heart Journal,[1]Journal of the American College of Cardiology,[2]Circulation,[3]Heart,[4]and Nature Reviews Cardiology[5] and is the subject of this interview.

Background to the Interview

As both an indicator of coronary artery disease (CAD) and an outcome measure in clinical trials, observational studies, and quality assurance programs, the clinical syndrome designated as MI requires a precise and consistent definition. Although a consensus has existed since the 1960s, the definition of MI has gradually evolved as more sensitive biomarker assays and imaging techniques have become available.

Before 2000, standard criteria set out by the World Health Organization (WHO) defined MI on the basis of symptoms; ECG abnormalities; and biomarkers, such as creatine kinase-myocardial band MB isoform (CKMB). Since 2000, however, these criteria have been formulated by global task forces representing major European, US, and international cardiology organizations. Following the consensus document issued in 2000,[6] which redefined MI as basically any necrosis in the setting of myocardial ischemia, the second, published in 2007,[7,8,9] focused on the different conditions that might lead to an MI.

The Third Universal Definition of Myocardial Infarction was presented during the recent annual congress of the ESC in Munich, Germany, on behalf of the ESC, the ACCF, the AHA, and the WHF, by the cochairs of the Joint ESC/ACCF/AHA/WHF Task Force: Joseph S. Alpert, MD (University of Arizona College of Medicine, Tucson), Professor Kristian Thygesen, MD, DSc (Aarhus University Hospital, Denmark), and Professor Harvey D. White, MB ChB (Auckland City Hospital, New Zealand). The task force involved 52 members from a record number of countries -- including, for the first time, China and Russia. The new definition was published simultaneously, in English, in 5 US and European medical journals.[1,2,3,4,5]

In the new definition, the diagnosis of acute MI remains unchanged: That is, it applies where there is evidence of myocardial necrosis in a clinical setting consistent with acute myocardial ischemia. However, the criteria for diagnosis have been updated, with an emphasis on the biomarker cardiac troponin.

The first essential criterion for diagnosis of MI is detection of a rise or fall in cardiac troponin, or CKMB if troponin is not available, with at least 1 value above the 99th percentile upper reference limit, plus at least 1 the following criteria:

  • Symptoms of ischemia;

  • ECG changes of new or presumed new ischemia (significant ST-segment T-wave changes or new left bundle branch block);

  • Development of pathologic Q waves on ECG; or

  • Imaging evidence of new loss of viable myocardium or new regional wall-motion abnormality.

Other criteria include those for MI in sudden unexpected cardiac death and for MI during percutaneous coronary intervention (PCI) and coronary artery bypass graft surgery (CABG).

The guidance document supports the use of high-sensitivity cardiac troponin assays, especially for distinguishing myocardial injury not related to myocardial ischemia, such as that associated with heart failure or renal failure. These assays are available in Europe, and not in the United States.

MI is designated as ST-segment elevation MI or non- ST-segment elevation MI, and as in the 2007 version, it is classified into 5 types on the basis of pathologic, clinical, and prognostic differences. These types have been updated in the latest version.

  • Type 1 MI (spontaneous MI) is related to atherosclerotic plaque rupture or other event leading to thrombus formation in ≥ 1 of the coronary arteries, leading to decreased myocardial blood flow with ensuing necrosis;

  • Type 2 MI arises from a condition other than CAD;

  • Type 3 MI is deemed to have occurred when cardiac death occurs with symptoms suggestive of myocardial ischemia, but without biomarker values having been obtained; and

  • Type 4 and 5 MIs are related to PCI and CABG, respectively, and have been redefined since 2007.

The new document also describes situations in which troponin levels are elevated in conditions where myocardial injury with necrosis is associated with predominantly nonischemic myocardial injury, such as heart failure, renal failure, myocarditis, arrhythmias, or pulmonary embolism. Guidance is offered for the application of the definition in clinical trials and cautions about the societal implications of revising diagnosis-related coding, hospital reimbursement, public health statistics, sick leave, and disability attestation, as well as the potential psychological consequences for patients and their families.

To further discuss the new definition and how it will affect clinical practice and research worldwide, Joseph S. Alpert, MD, cochair of the Joint Task Force for the Universal Definition of Myocardial Infarction, spoke with Linda Brookes, MSc, for Medscape.