Features of the Metabolisms of Cardiac Troponin Molecules—Part 1: The Main Stages of Metabolism, Release Stage

Role of Antitroponin Antibodies and Macrotroponin in the Clinical Interpretation of Cardiac Troponin

Cardiac troponin is extensively used as a biomarker in modern medicine due to its diagnostic capability for myocardial injury, as well as its predictive and prognostic value for cardiac diseases. However, heterophile antibodies, antitroponin antibodies, and macrotroponin complexes can be observed both in seemingly healthy individuals and patients with cardiac diseases, potentially leading to false positive or disproportionate elevation of cTn (cardiac troponin) assay results and introducing discrepancies in clinical interpretations with impact on medical management. In this review article, we describe the possible mechanisms of cTn release and the sources of variations in the assessment of circulating cTn levels. We also explore the pathophysiological mechanisms underlying antitroponin antibody development and discuss the influence exerted by macrotroponin complexes on the results of immunoassays. Additionally, we explore approaches to detect these complexes by presenting various clinical scenarios encountered in routine clinical practice. Finally, unsolved questions about the development, prevalence, and clinical significance of cardiac autoantibodies are discussed.

Vacuum assisted and gravitational venous drainage in aortic valve surgery: A propensity-match study

INTRODUCTION

Vacuum assisted venous drainage (VAVD) is widely adopted in minimally invasive cardiac surgery. VAVD enables the advantage of using smaller cannulae in a reduced surgical field while allowing satisfactory drainage and pump flow. The production of gaseous micro-emboli is a recognized risk associated with VAVD, however no difference in clinical endpoints have been reported between patients operated on with gravity venous drainage (GVD) or with VAVD. Due to the paucity of data on selected surgical populations, we sought to evaluate the early outcomes of patients undergoing isolated aortic valve replacement using VAVD or GVD.

METHODS

Data on 521 patients between 09/2016 and 09/2022 were retrieved from our internal database. Patients were divided into two groups according to use VAVD or GVD. A propensity match analysis was performed to account for difference between the two groups.

RESULTS

The propensity match provided two well balanced cohorts with 129 patients each. A minimally invasive access was used in 97% of the cases in VAVD group vs 98% in GVD group (p = .68). Mean cardiopulmonary by-pass (CPB) time was 71 vs 73 min (p = .74), respectively. There was no difference in lactates peak (p = .19) and urine output during CPB (p = .74). We registered two in-hospital deaths in VAVD cohort (1.6%) vs. no mortality in GVD group (p = .5). Postoperative cerebral stroke occurred in 1 patient in GVD cohort vs. 0 in VAVD (p = 1). Severe postoperative acute kidney injury complicated the course in 16 patients in GVD group and in 5 patients who had VAVD (p = .012). VAVD was associated with a higher number of patients with elevated postoperative AST (p = .07) and Troponin I (p = .01) values.

CONCLUSIONS

The use of VAVD during isolated aortic valve replacement was not associated with increased risks of postoperative complications and in-hospital mortality with results that were at least similar to those registered in a matched cohort of patients operated on with GVD.

Kinetics of cardiac troponin and other biomarkers in patients with ST elevation myocardial infarction

Objective

To examine changes in concentration, time-to-peak and the ensuing half-life of cardiac biomarkers in patients with myocardial infarction.

Methods

Blood sampling was performed every third hour within 24 h after percutaneous coronary intervention (PCI) on a cohort of patients with ST elevation myocardial infarction. Cardiac troponin (cTn) was measured by the Dimension Vista, Vitros, Atellica, and Alinity high-sensitivity (hs) cTnI assays, and the Elecsys hs-cTnT assay. Further, creatine kinase (CK), myoglobin, creatine kinase MB (CKMB) and other biomarkers were analyzed.

Results

A total of 36 patients completed blood sampling (median age 60 years, IQR 56.4-66.5 years; seven women, 19.4%). Hs-cTnI measured by the Vitros assay was the first hs-cTn to peak at 9.1 h (95%-CI 6.2-10.1) after PCI and 11.7 h (95%-CI 10.4-14.8) after symptoms onset. There were no notable differences between hs-cTn assays in regard to time-to-peak. Also, Vitros hs-cTnI reached the highest median ratio of concentration to upper reference level of nearly 2,000. The median half-life from peak concentration ranged from 7.6 h for myoglobin (CI 6.8-8.6) to 17.8 h for CK (CI 6.8-8.6). For hs-cTn assays the median T½ ranged from 12.4 h for the Vista hs-cTnI assay (95%-CI 11.0-14.1 h) to 17.3 h for the Elecsys hs-cTnT (95%-CI 14.9-20.8 h).

Conclusions

This study updates knowledge on the kinetics of cardiac biomarkers in current clinical use. There was no notable difference in trajectories, time-to-peak or half-life between hs-cTn assays.

Diagnostic Role and Methods of Detection of Cardiac Troponins: An Opinion from Historical and Current Points of View

The laboratory methods for the determination of cardiac troponins (cTnI, cTnT) used nowadays are extremely diverse, which has a significant impact on our understanding of the biology and diagnostic the value of cTnI and cTnT as biomarkers. The main classification of methods for the determination of cTnI and cTnT is based on the sensitivity of the immunoassay. Low- and moderately sensitive detection methods are known to be relatively less sensitive, which leads to a relatively late confirmation of cardiomyocyte death. Due to the new highly sensitive methods used to determine cTnI and cTnT, designated as a highly or ultrasensitive immunoassays (hs-TnT and hs-TnT), we received new, revised data about the biology of cardiac troponin molecules. In particular, it became clear that they can be considered products of normal myocardium metabolism since hs-TnT and hs-TnT are detected in almost all healthy patients. It also turned out that hs-TnT and hs-TnT differ by gender (in men, troponin concentration in the blood is higher than in women), age (in elderly patients, the levels of troponins are higher than in young ones) and circadian cycles (morning concentrations of troponins are higher than in the evening). A large variety of methods for determining cTnI and cTnT, differing in their diagnostic capabilities, creates the need for tests to perform an unbiased assessment of the analytical characteristics of each method. This review focuses on the most pressing issues related to the discussion of the biological characteristics of cardiac troponin and the analytical characteristics of troponin immunoassays from a historical and contemporary point of view.