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MUNICH -- Guidelines issued by the major world cardiology associations to update and standardize just what is a heart attack have added the concept of "myocardial injury."

The new 4th Universal Definition of Myocardial Infarction emphasizes troponin expression as the main trigger to determine if a person should go to the cath lab for chest pain that may be a heart attack, the authors of the 30-page guideline reported in the European Heart Journal.

Cardiac injury is defined as a rise in troponin without other symptoms or components of myocardial infarction.

"The term acute myocardial infarction should be used when there is acute myocardial injury with clinical evidence of acute myocardial ischemia and with detection of a rise and/or fall of cardiac troponin values with at least one value above the 99th percentile upper reference limit and at least one of the following:

• "Symptoms of myocardial ischemia"
• "New ischemic 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 ischemic 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 European Society of Cardiology, 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 heart attack, patients with chest pain may be wrongly labelled with heart attack and not receive the correct treatment," said Kristian Thygesen, MD, of Aarhus University Hospital in Denmark.

"Many doctors have not understood that elevated troponin levels in the blood are not sufficient to diagnose a heart attack and this has created real problems," said Thygesen, who was joint chair of the Task Force that wrote the document, together with Joseph Alpert, MD, of the University of Arizona in Tucson, and Harvey White, MD, MD, of Auckland City Hospital in New Zealand.

"It is important on several levels to know that what is called a heart attack in Cleveland is also considered a heart attack in London," Russell Luepker, MD, of the University of Minnesota in Minneapolis, told 乌鸦传媒. "We have tightened up definitions of heart attack categories."

The new definition also touches on new technologies that include advances in imaging and development of ultra-sensitive troponin assays, noted Luepker, a member of the multi-person task force that worked on the project.

Richard Kovacs, MD, of Indiana University School of Medicine in Indianapolis and vice president of the American College of Cardiology, said the new heart attack definition is needed "because we use these definitions for so much of our quality improvement in our hospitals and clinics."

He told 乌鸦传媒, "It is important that they have brought back the concept of myocardial injury so we can have a diagnosis of injury not just infarction. That's a big deal for the patients, because patients with an infarction are treated differently than those with an cardiac injury."

Kovacs said that have a "crisp definition" of myocardial infarction is also a benefit to doctors, to payers, to regulators, and to researchers, so that when one talks about a heart attack in one institution, it is the same phenomenon occurring to a patient in another facility.

The guideline task force researchers acknowledged the ongoing controversy concerning what troponin assay should be considered to make determination of myocardial infarction.

"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," they noted.

"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."

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