Third Universal Definition of MI Is a Charm

Marlene Busko

August 28, 2012

August 28, 2012 (Munich, Germany) — An international group of experts has released a third universal definition of MI, which builds on an earlier iteration and establishes the levels of cardiac troponin required to diagnose MI in different scenarios [1].

The consensus document was developed by a 52-member task force that represented four societies: the American College of Cardiology (ACC), the American Heart Association (AHA), the European Society of Cardiology (ESC), and the World Heart Federation (WHF).

Lead author Dr Kristian Thygesen (Aarhus University Hospital, Denmark) presented the document at the European Society of Cardiology (ESC) 2012 Congress on August 25, 2012. It will be published at about the same time in five journals: Circulation, the Journal of the American College of Cardiology, the European Heart Journal, Global Heart, and Nature Reviews Cardiology.

The document, which updates their 2007 definition of MI, was needed due to the appearance of more sensitive troponin assays in the intervening years, the group writes.

In this version, the experts agreed that "troponin remains the biomarker of choice to detect acute myocardial infarction," AHA spokesperson Dr Gregg C Fonarow (Ahmanson-UCLA Cardiomyopathy Center, Los Angeles, CA) told heartwire . "The key criterion for [diagnosing] acute myocardial infarction remains that there is evidence of myocardial necrosis in a clinical setting consistent with acute myocardial ischemia," he added. "If cardiac troponin is used [as the biomarker], there should be at least one value above the 99th percentile upper reference limit for the specific troponin assay."

Improved Guidance for Clinical Practice, Clinical Trials

In 2000, the first global MI task force published a new definition of MI that suggested that MI equals cell death plus acute myocardial ischemia. In 2007, the second global MI task force issued an update that specified five types of MI, which remain similar in the current document.

Recent data allowed the definition to be further refined and clarified, Fonarow said. In the past, the lack of an accepted definition of MI in various settings made it difficult to compare data across different clinical practices, administrative data sets, registries, and clinical trials.

This updated document includes criteria for defining acute MI after different procedures.

MI related to PCI is defined as an elevation of cardiac troponin levels that is greater than five times the 99th percentile upper reference limit in patients with normal baseline troponin levels or a more than 20% rise in troponin in patients with elevated and stable or falling troponin levels.

MI related to CABG is defined as troponin values greater than 10 times the 99th percentile upper reference limit during the first 48 hours after CABG in patients with normal baseline troponin levels.

The consensus statement also defines MI associated with stent thrombosis.

ECG is an integral part of the diagnostic workup in patients with suspected MI, according to the authors. They also spell out how imaging techniques such as echocardiography, nuclear imaging, MRI, and computed tomography (CT) can be useful to diagnose MI.

"The new definition will likely be adopted by the FDA and will be used in clinical-trial protocols accepted by the FDA," Fonarow speculates. "This will help to standardize the way myocardial infarction is defined in clinical trials, registries, and clinical practice, making comparisons between trials and clinical practice more meaningful."

Thygesen has received speaker fees, honoraria, consultancy fees, and advisory-board fees from and has served as an investigator or committee member for Edwards Lifesciences, Servier, St Jude Medical, Roche Pharma, the Danish Heart Foundation, and Roche Diagnostics and has received research funding (department or institutional) from Roche Pharma, the Danish Heart Foundation, Tryg Fonden, and Roche Diagnostics. The relationships between the task force members and industry, government, and private health providers are published in an online supplement. Fonarow has no relevant disclosures.