New Definition of Myocardial Infarction Established

August 29, 2018

By Alex Morrisson

MUNICH, Germany -- August 28, 2018 -- Cardiac injury can occur without an actual myocardial infarction (MI), according to updated definition and guidelines presented here at the 2018 Congress of the European Society of Cardiology (ESC)

“The term myocardial injury should be used when there is evidence of elevated cardiac troponin values with at least 1 value above the 99th percentile upper reference limit,” explained lead author Kristian Thygesen, MD, Aarhus University Hospital, Aarhus, Denmark. “The myocardial injury is considered acute if there is a rise and/or fall of cardiac troponin values.”

The key portion of the guideline, which hasn’t been updated since 2012, is the definition of an MI. The authors wrote that the term acute MI should be used when there is acute myocardial injury with clinical evidence of acute myocardial ischaemia and with detection of a rise and/or fall of cardiac troponin values with at least 1 value above the 99th percentile upper reference limit and at least 1 of the following:
● Symptoms of myocardial ischaemia
● New ischaemic electrocardiogram (ECG) changes
● Development of pathological Q waves
● Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality in a pattern consistent with an ischaemic etiology
● Identification of a coronary thrombus by angiography or autopsy

The guidelines are the 4-year work of a committee representing cardiologists and other healthcare professionals from the ESC, the American College of Cardiology, the American Heart Association, and the World Heart Federation.

“Unless there is clarity in the emergency room on what defines a MI, patients with chest pain may be wrongly labelled and not receive the correct treatment,” said Dr. Thygesen. “Many doctors have not understood that elevated troponin levels in the blood are not sufficient to diagnose a MI and this has created real problems.”

The guideline authors acknowledged the ongoing controversy concerning which troponin assay should be considered to make a determination of a MI.

“Clinicians should be aware that for all cardiac troponin assays, including high sensitivity cardiac troponin assays, there is still no expert opinion or consensus about specific criteria for how the 99th percentile upper reference level should be defined,” the authors wrote. “We endorse International Federation of Clinical Chemistry and Laboratory Medicine guidelines on the technical issues related to high sensitivity cardiac troponin assays, including how studies should be configured to determine 99th percentile upper reference levels.”

[Presentation title: Fourth Universal Definition of Myocardial Infarction (2018)]