![]() ![]() In one study, ~42% of patients diagnosed with type 2 MI actually had myocardial injury without ischemia and thus were misdiagnosed. Patients with myocardial injury are often misdiagnosed as having a type 2 MI in clinical practice. 4 A cardiac troponin result above the 99th percentile URL without a rise and/or fall over a period of serial measurements is characteristic of chronic myocardial injury. No standard exists for how much rise and/or fall of cardiac troponin identifies acute injury typically, an increase in the concentration greater than the reference change value (biological variation of an assay) is considered acute if the initial troponin value is 99th percentile, then an increase of at least 50% of the 99th percentile or a change >20% may be considered acute. Myocardial injury is considered acute if there is a rise and/or fall of cardiac troponin concentrations exceeding biological and/or analytical variation. 3 To address this, the Fourth Universal Definition of MI introduced the entity myocardial injury, which is defined by at least 1 cardiac troponin concentration above the 99th percentile URL. In the contemporary era, a vast number of patients with elevated troponin concentrations do not have evidence of ischemia. There are 5 recognized types of MI the most frequently encountered are type 1 MI (characterized by atherosclerotic processes such as plaque rupture, ulceration, fissuring, erosion, or dissection resulting in coronary thrombosis) and type 2 MI (myocardial necrosis resulting from a mismatch in myocardial oxygen supply-demand and occurring in the absence of an atherothrombotic event). New regional wall motions on imaging in an ischemic territory. ![]() New electrocardiographic evidence of ischemia.2 As defined by the Task Force, an MI is defined as a rise and/or fall in cardiac troponin (conventional or high sensitivity) with at least 1 value above the 99th percentile of the upper reference limit (URL) and at least 1 of the following: The latest iteration, the Fourth Universal Definition, was published in 2018. 1 Over the past decade, serial modifications to the definition have been made. To more precisely define acute MI and in recognition of its various presentations, the Universal Definition of MI was first published in 2007. Differentiating type 2 MI from myocardial injury is a relevant challenge with several considerations.ĭefining Type 2 MI Versus Myocardial Injury Furthermore, due to increasing medical complexity and more chronic coronary artery disease, the incidence of type 2 MI (due to supply-demand imbalance) is also higher. This may lead to clinician confusion and uncertainty. Troponin measurement is typically performed to seek acute myocardial infarction (MI), but all forms of myocardial injury (including nonischemic forms) are reflected in elevated troponin concentrations. The advent of more sensitive troponin assays together with widespread (and sometimes indiscriminate) use of troponin testing has led to more recognition of how prevalent myocardial injury may be.
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