Troponin testing: Analytical aspects
- Allan S Jaffe, MD
Allan S Jaffe, MD
- Section Editor — Coronary Heart Disease
- Professor of Medicine
- Mayo Medical School
- David A Morrow, MD, MPH
David A Morrow, MD, MPH
- Professor of Medicine
- Harvard Medical School
- Section Editor
- Juan Carlos Kaski, DSc, MD, DM (Hons), FRCP, FESC, FACC, FAHA
Juan Carlos Kaski, DSc, MD, DM (Hons), FRCP, FESC, FACC, FAHA
- Section Editor — Coronary Heart Disease
- Professor of Cardiovascular Science
- Director, Cardiovascular and Cell Sciences Research Institute
- St. George's, University of London
Cardiac injury occurs when there is disruption of normal cardiac myocyte membrane integrity. This results in the loss into the extracellular space (including blood) of intracellular constituents, including detectable levels of a variety of biologically active cytosolic enzymes and structural proteins, referred to as biomarkers, such as troponin, creatine kinase, myoglobin, heart-type fatty acid binding protein, and lactate dehydrogenase. Injury is usually considered irreversible (cell death), but definitive proof that cell death is always the cause when troponin is released, without possible contributions from reversible other mechanisms, is not available. (See "Troponin testing: Clinical use", section on 'Possible acute myocardial injury'.)
When a sufficient number of myocytes have died (myocyte necrosis), elevations of troponin occur. If this occurs over a short period, acute clinical disease may be apparent. If over a longer period, more chronic processes may be responsible. The causes of cardiac injury are numerous. Ischemia, consequent to an imbalance between the supply and demand of oxygen (and nutrients), is one common cause. Because earlier biomarkers of cardiac injury were much less sensitive and thus when elevated were more likely to reflect marked insults such as ischemia, some clinicians consider any elevation of a biomarker of cardiac injury as indicative of ischemic heart disease. However, this assumption has never been correct, and is even less so now that more sensitive markers such as troponin are in clinical use. Other causes of myocardial injury are included in a table (table 1).
The biochemical characteristics and utility of troponins for the diagnosis of cardiac injury, and acute myocardial infarction in particular, will be reviewed here. Other relevant topics include:
●(See "Troponin testing: Clinical use".)
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