Cardiac troponins in chronic kidney disease patients with special emphasis on their importance in acute coronary syndrome

Defining Myocardial Infarction in trials of people receiving hemodialysis: consensus report from the SONG-HD MI Expert Working group

Cardiovascular disease is the leading cause of death in patients receiving hemodialysis. Currently there is no standardized definition of myocardial infarction (MI) for patients receiving hemodialysis. Through an international consensus process MI was established as the core CVD measure for this population in clinical trials. The Standardised Outcomes in Nephrology Group - Hemodialysis (SONG-HD) initiative convened a multidisciplinary, international working group to address the definition of MI in this population.Based on current evidence, the working group recommends using the 4th Universal Definition of MI with specific caveats with regard to the interpretation of "ischemic symptoms" and performing a baseline 12-lead electrocardiogram to facilitate interpretation of acute changes on subsequent tracings. The working group does not recommend obtaining baseline cardiac troponin values, though does recommend obtaining serial cardiac biomarkers in settings where ischemia is suspected. Application of an evidence-based uniform definition should increase the reliability and accuracy of trial results.

Monthly measurement of high-sensitivity cardiac troponins T and creatine kinase in asymptomatic chronic hemodialysis patients: A one-year prospective study

BACKGROUND

Cardiology guidelines recommend measuring high-sensitivity cardiac troponin (hs-cTn) for the diagnostic work-up of acute coronary syndromes (ACS). Many hospitals measure hs-cTnT, but preliminary data have shown that hs-cTnT is higher than normal in many hemodialysis patients without evidence of ACS. The purpose of this study was therefore to determine the hs-cTnT levels every month for 1 year in asymptomatic hemodialysis patients, in order to assess their changes over time relative to creatine kinase.

METHODS

Fourty-four hemodialysis patients (mean age 67 ± 14 years) were included. The predialysis levels of fifth-generation hs-cTnT, CK, and CK-MB were measured every month for 1 year using a Cobas® 6000 analyzer (Roche Diagnostics, Switzerland).

RESULTS

Almost 100% of hs-cTnT measurements were higher than normal (N < 14 ng/L); the mean ± SD annual level was 84 ± 59 ng/L, ranging from a minimum of 24 ± 2 to 241 ± 28 ng/L in individual patients. The mean levels of CK and CK-MB were normal. Thirteen myocardial infarctions were analyzed, which were all associated with an initial elevation in hs-cTnT >45% from the individual baseline value. By comparison, CK and CK-MB only increased in 38% and 31% of these myocardial infarctions, respectively.

DISCUSSION

hs-cTnT is persistently higher than normal in chronic hemodialysis patients. Standard algorithms for diagnosing ACS can obviously not be used and alternative diagnostic strategies need to be developed. According to our data, and given the huge variation in baseline hs-cTnT levels among patients, the use of higher cut-offs as proposed in the literature cannot be recommended. Instead, we consider that hs-cTnT should be checked at regular intervals (e.g., every 3-6 months) in order to establish individual baseline levels for hs-cTnT. This approach, in most instances, not only makes it possible to more rapidly rule-in but also to rapidly rule-out, cases of ACS in hemodialysis patients who develop cardiac symptoms.

Diagnostic Reclassification by a High-Sensitivity Cardiac Troponin Assay

STUDY OBJECTIVE

Our objective is to describe the rates of diagnostic reclassification between conventional cardiac troponin I (cTnI) and high-sensitivity cardiac troponin T (hs-cTnT) and between combined and sex-specific hs-cTnT thresholds in adult emergency department (ED) patients in the United States.

METHODS

We conducted a prospective, single-center, before-and-after, observational study of ED patients aged 18 years or older undergoing single or serial cardiac troponin testing in the ED for any reason before and after hs-cTnT implementation. Conventional cTnI and hs-cTnT results were obtained from a laboratory quality assurance database. Combined and sex-specific thresholds were the published 99th percentile upper reference limits for each assay. Cases underwent physician adjudication using the Fourth Universal Definition of Myocardial Infarction. Diagnostic reclassification occurred when a patient received a diagnosis of myocardial infarction or myocardial injury with one assay but not the other assay. Our primary outcome was diagnostic reclassification between the conventional cTnI and hs-cTnT assays. Diagnostic reclassification probabilities were assessed with sample proportions and 95% confidence intervals for binomial data.

RESULTS

We studied 1,016 patients (506 men [50%]; median age 60 years [25th, 75th percentiles 49, 71]). Between the conventional cTnI and hs-cTnT assays, 6 patients (0.6%; 95% confidence interval 0.2% to 1.3%) underwent diagnostic reclassification regarding myocardial infarction (5/6 reclassified as no myocardial infarction) and 166 patients (16%; 95% confidence interval 14% to 19%) underwent diagnostic reclassification regarding myocardial injury (154/166 reclassified as having myocardial injury) by hs-cTnT.

CONCLUSION

Compared with conventional cTnI, the hs-cTnT assay resulted in no clinically relevant change in myocardial infarction diagnoses but substantially more myocardial injury diagnoses.

Implications of the complex biology and micro-environment of cardiac sarcomeres in the use of high affinity troponin antibodies as serum biomarkers for cardiac disorders

Cardiac troponin I (cTnI), the inhibitory-unit, and cardiac troponin T (cTnT), the tropomyosin-binding unit together with the Ca-binding unit (cTnC) of the hetero-trimeric troponin complex signal activation of the sarcomeres of the adult cardiac myocyte. The unique structure and heart myocyte restricted expression of cTnI and cTnT led to their worldwide use as biomarkers for acute myocardial infarction (AMI) beginning more than 30 years ago. Over these years, high sensitivity antibodies (hs-cTnI and hs-cTnT) have been developed. Together with careful determination of history, physical examination, and EKG, determination of serum levels using hs-cTnI and hs-cTnT permits risk stratification of patients presenting in the Emergency Department (ED) with chest pain. With the ability to determine serum levels of these troponins with high sensitivity came the question of whether such measurements may be of diagnostic and prognostic value in conditions beyond AMI. Moreover, the finding of elevated serum troponins in physiological states such as exercise and pathological states where cardiac myocytes may be affected requires understanding of how troponins may be released into the blood and whether such release may be benign. We consider these questions by relating membrane stability to the complex biology of troponin with emphasis on its sensitivity to the chemo-mechanical and micro-environment of the cardiac myocyte. We also consider the role determinations of serum troponins play in the precise phenotyping in personalized and precision medicine approaches to promote cardiac health.

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Serum levels of cardiac TnI and cardiac TnT permit stratification of patients with chest pain.

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Release of troponins into blood involves not only frank necrosis but also programmed necroptosis.

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Genome wide analysis of serum troponin levels in the general population may be prognostic about cardiovascular health.

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Significant levels of serum troponins with exhaustive exercise may not be benign.

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Troponin in serum can lead to important data related to personalized and precision medicine.