BEST PRACTICES :: UNDERSTANDING ELEVATED TROPONIN
In the presence of a cTn above the 99th percentile URL, the serial troponin pattern helps distinguish acute versus chronic myocardial injury, and the presence or absence of signs and/ or symptoms of clinical myocardial ischemia help further distinguish acute myocardial injury from acute myocardial infarction (type 1 versus type 2 MI; Figure 1). MI types 3, 4, and 5 involve cardiac death and coronary procedure–related ischemia, and more information can be found within the ref- erenced publications.1
Defining and interpreting an elevated troponin Two overarching groups of elevated cTn in the absence of MI include causes related to 1) biological factors, including other disease states that can cause acute or chronic myocardial injury, and 2) assay factors, including interferences and pre-analytical influences. A contributing effect may begin with a choice made prior to even beginning use of a cTn assay, when making the choice of the 99th percentile URL to utilize. It is recommended to utilize sex-specific 99th percentile URLs, as women have lower levels of cTn compared to men.1,3
Use of an overall 99th
percentile (which falls below the male-specific 99th percentile, and above the female-specific 99th percentile) in a male patient with a result near this threshold may lead to interpretation of the result as greater than the 99th percentile, when with use of a male-specific 99th percentile URL the result would be less than this threshold. The probability of this scenario is somewhat low, however, given the likelihood of cTn results that may be expected to occur close to the 99th percentile.
Biological-related cardiac troponin elevations One of the first factors to consider when interpreting an elevated troponin result in the differential diagnosis of acute MI is a cause where the troponin is truly elevated, but due to disease other than acute MI, to assure the proper diagnosis and treatment are identified. Referring back to Figure 1, these mechanisms of myocardial cell injury may be acute non-ischemic (no cTn rise and/or fall) or may be chronic (cTn stable). These diseases can largely be grouped into two categories: 1) cardiac causes and 2) non-cardiac or systemic causes (Figure 2). Examples of cardiac diseases that may cause an elevated cTn include atrial fibrillation, myocarditis, and acute heart failure.1,4
Some cardiac
disorders would have overlapping signs or symptoms with acute MI, such as shortness of breath, weakness, and even chest pain, meaning that the differential diagnosis must be carefully evaluated. Examples of non-cardiac or systemic disorders that may cause myocardial injury and elevated cTn include chronic kidney disease, pulmonary hypertension, stroke, and sepsis.1,4 For some cTnT assays, one source of elevation that has been published on consistently in the non-cardiac disorder group is skeletal muscle disease, which has been hypothesized to be due to re-expression of cTnT in the skeletal muscle.5,6
Another
more recently discovered cause of increased cTn is COVID-19. A variety of cardiac or non-cardiac sources may cause a cTn increase in the clinical context of COVID-19, some of which may be non-ischemic but also ischemic, and the observed cTn concentration reflects a combination of what may be pre-existing cardiac disease and acute myocardial injury.7
MLO-ONLINE.COM SEPTEMBER 2023 | 39
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48
