The clinical need for high-sensitivity cardiac troponin assays for acute coronary syndromes and the role for serial testing

Perioperative Change of High-Sensitive Cardiac Troponin I Concentration in Cats According to Three Different Anaesthesia Protocols

BACKGROUND

Cardiac troponin I, a particular biomarker, is released into the bloodstream in response to myocardial injury.

OBJECTIVES

To evaluate perioperative changes in high-sensitivity cardiac troponin I (hs-cTnI) concentration during ovariohysterectomy in cats undergoing three different anaesthesia protocols.

METHODS

 Twenty-one female mixed-breed cats owned by clients aged (2.2 ± 0.7 years) and weight (3.2 ± 0.5 kg) were included in our study. The cats were divided into three groups: propofol-isoflurane (PI) group (n = 7), xylazine-ketamine (XK) group (n = 7) and xylazine-isoflurane (XI) group (n = 7). After pre-anaesthetic propofol (6 mg/kg IV) was administered to cats in Group PI, a mask was placed, and anaesthesia was maintained with 3.0% isoflurane in oxygen. Cats in Group XK underwent general anesthetization with xylazine hydrochloride (2 mg/kg IM) and, 10 min later, ketamine hydrochloride (10 mg/kg IM). Cats in Group XI were administered xylazine hydrochloride (2 mg/kg IM), and then anaesthesia (3.0% isoflurane and oxygen) was continued with a mask. Blood samples were collected from all cats; preoperatively and postoperatively at 0 and 12 h (Pre-, Post-0 h and Post-12 h, respectively). Serum hs-cTnI concentrations were measured with the Advia Centaur TnI-Ultra.

RESULTS

In all 21 cats, hs-cTnI concentration increased at Post-0 h and 12 h measurement points compared to Pre-. In the XK group, hs-cTnI concentrations exhibited a significant increase at the Post-0 h (51.30 ng/L) and Post-12 h (157.70 ng/L) time points compared to Pre- (6.70 ng/L) (p < 0.05).

CONCLUSIONS

The XK group increased the concentration of hs-cTnI more than other protocols. In the PI group, the increase in hs-cTnI concentrations at Post-0 and 12 h increased less than the other two groups (p < 0.05). The PI group was found to induce less myocardial damage.

Clinical relevance and advances in detection of translational biomarker cardiac troponin

Cardiovascular diseases (CVD) are a range of diseases, pointing the functional hindrances in the heart and blood vessels of the human system that contributes to 48.6 % of the world's adult death rate. The diagnosis of CVD relies upon the Electro Cardio Gram (ECG) and detection of muscle markers such as troponins. Among the cardiac trio, Cardiac Troponin I (cTnI) weighing 23 KiloDalton (kDa) is a sorted biomarker for CVD. cTnI remains high in the blood after 1-2 weeks of myocardial damage. Testing of cTnI in CVD patients aids in diagnosis and risk stratification of the disease. Different determination systems including optical, electrochemical, and acoustic have been put forward for monitoring the cTnI which are Point of Care (POC) that promotes simple and sensitive detection of cTnI. The modern era has paved way to high-sensitivity Troponin I (hscTnI) devices that can detect up to 0.01 ng/ml in human blood/plasma/serum. Yet, the practice of hscTnI is impracticable due to cost inefficiency. Development of new hscTnI devices with minimal investment and maximal detection range will meet the global requirement. This review gives an over view on different detection systems of cardiac troponin I which stands as a translational detection molecule for CVDs.

Judging the clinical suitability of analytical performance of cardiac troponin assays

New millennium diagnostic criteria for acute myocardial infarction precipitated a revolutionary shift from an approach based primarily on electrocardiography and clinical symptoms to a strategy based on biomarkers, and preferably cardiac troponins (cTn) I and T. In the last 20 years, clinical recommendations have strengthened the role of cTn and led to the development of highly sensitive (hs-cTn) assays, which are now leading players in all current clinical practice guidelines. To optimize the clinical use of these hs-cTn assays, focus on their analytical aspects has become increasingly important, emphasizing the need for the establishment of suitable analytical performance by the definition and implementation of appropriate specifications. An accurate estimate of measurement uncertainty, together with the acquisition of the highest analytical quality when very low concentrations of hs-cTn are measured, are essential requirements and should represent a practical laboratory standard in assuring optimal clinical use. Additional goals for further improving the quality of laboratory information should be the establishment of robust data concerning biological variation of cTn and the resolution of practical challenges opposed to the harmonization of cTn I results obtained by differing commercial measuring systems.

Diagnostic accuracy of glycogen phosphorylase BB for myocardial infarction: A systematic review and meta-analysis

PURPOSE

We tried to investigate the diagnostic accuracy of glycogen phosphorylase BB as a cardiac marker for myocardial infarction.

METHODS

We searched through different electronic databases (PubMed, Google-scholar, Embase, and Cochrane Library) to locate relevant articles. Studies, with sufficient data to reconstruct a 2 × 2 contingency table, met our inclusion criteria were included. Three reviewers independently screened the articles. Discrepancies were resolved by other reviewers. Unpublished data were requested from the authors of the study via email. Subsequently, data extraction was done using a standardized form and quality assessment of studies using the QUADAS-2 tool. Meta-analysis was done using a bivariate model using R software.

RESULTS

Fourteen studies were selected for the final evaluation, which yielded the summary points: pooled sensitivity 87.77% (77.52%-93.72%, I2  = 86%), pooled specificity 88.45% (75.59%-94.99%, I2  = 88%), pooled DOR 49.37(14.53-167.72, I2  = 89%), and AUC of SROC was 0.923. The lambda value of the HSROC curve was 3.670. The Fagan plot showed that GPBB increases the pretest probability of myocardial infarction from 46% to 81% when positive, and it lowers the same probability to 12% when negative.

CONCLUSION

With these results, we can conclude that GPBB has modest accuracy in screening myocardial infarction, but the limitations of the study warrant further high-quality studies to confirm its usefulness in predicting myocardial infarction (MI).

Poor outcome among patients undergoing myocardial perfusion imaging with intermediate-zone troponin

BACKGROUND

Intermediate zone troponin elevation is defined as one to five times the upper limit of normal. Approximately half the patients presenting with chest pain to the emergency department have initial intermediate zone troponin.

OBJECTIVES

We aimed to investigate the long-term outcome of patients hospitalized with chest pain and intermediate zone troponin elevation.

METHODS

We investigated 8269 patients hospitalized in a tertiary center with chest pain. All patients had serial measurements of troponin during hospitalization. Patients were divided into three groups based on their initial troponin levels: negative troponin (N = 6112), intermediate zone troponin (N = 1329) and positive troponin (N = 828). All patients underwent myocardial perfusion imaging (MPI) as part of the initial evaluation.

RESULTS

Mean age of the study population was 68 ± 11, of whom 36% were women. Patients with an intermediate zone troponin were older, more likely to be males, and with significantly more cardiovascular co-morbidities. Multivariate analysis adjusted for age, gender, cardiovascular risk factors, and abnormal MPI result found that patients with intermediate zone troponin had a 70% increased risk of re-hospitalization at 1 year (HR 1.70, 95%CI 1.48-1.96, p-value < 0.001) and 5.3 times higher risk of total mortality at 1-year (HR 5.33, 95%CI 3.65-7.78, p-value < 0.001). sub-group analysis found that among the intermediate zone troponin group, patients with double intermediate zone troponin had the poorest outcome.

CONCLUSIONS

Intermediate zone troponin elevation is an independent risk factor associated with adverse outcomes and therefore patients with an initial value in this range should be closely monitored and aggressively managed.

Desempenho Diagnóstico da Angiotomografia Computadorizada e da Avaliação Seriada de Troponina Cardíaca Sensível em Pacientes com Dor Torácica e Risco Intermediário para Eventos Cardiovasculares

Fundamento

A angiotomografia coronária (ATC) tem sido usada para avaliação de dor torácica principalmente em pacientes de baixo risco, e poucos dados existem com pacientes em risco intermediário.

Objetivo

Avaliar o desempenho de medidas seriadas de troponinas sensíveis e de ATC em pacientes de risco intermediário.

Métodos

Um total de 100 pacientes com dor torácica, TIMI score 3 ou 4 e troponina negativa foram prospectivamente incluídos. Todos os pacientes foram submetidos à ATC, e aqueles com obstruções ≥ 50% foram encaminhados à cineangiocoronariografia. Pacientes com lesões < 50% recebiam alta hospitalar, receberam alta e foram contatados 30 dias depois por telefonema para avaliação dos desfechos clínicos. Os desfechos foram hospitalização, morte, e infarto agudo do miocárdio em 30 dias. A comparação entre os métodos foi realizada pelo teste de concordância kappa. O desempenho das medidas de troponina e da ATC na detecção de lesões coronárias significativas e desfechos clínicos foi calculado. Os resultados foram considerados estatisticamente significativos quando p <0,05.

Resultados

Estenose coronária ≥ 50% na ATC foi encontrada em 38% dos pacientes e lesões coronárias significativas na angiografia coronária foram encontradas em 31 pacientes. Dois eventos clínicos foram observados. A análise de concordância Kappa mostrou baixa concordância entre as medidas de troponina e ATC na detecção de lesões coronárias significativas (kappa = 0,022, p = 0,78). O desempenho da ATC para detectar lesões coronárias significativas na angiografia coronária ou para prever eventos clínicos em 30 dias foi melhor que as medidas de troponina sensível (acurácia de 91% versus 60%).

Conclusão

ATC teve melhor desempenho que as medidas seriadas de troponina na detecção de doença coronariana significativa em pacientes com dor torácica e risco intermediário para eventos cardiovasculares.

Type-II myocardial infarction and chronic myocardial injury rates, invasive management, and 4-year mortality among consecutive patients undergoing high-sensitivity troponin T testing in the emergency department

AIMS

As assessment of patients with suspected acute coronary syndromes (ACS) in emergency departments (EDs) represents a major workload because high-sensitivity troponin (HsTn) T and I levels are frequently measured, and a minority of patients have final diagnosis of myocardial infarction (MI). We determined the relative frequencies of three patients groups: Type-I MI, Type-II MI (including acute myocardial injury).

METHODS AND RESULTS

Among 2738 consecutive patients with suspected ACS presenting to ED at Liverpool Hospital, Australia, between March and June 2014. We studied the use of invasive and pharmacological therapies, and 4-year outcomes. Adjudication of MI was according to the 4th universal definition as follows: (i) Type-I MI; (ii) Type-II MI (including acute myocardial injury), and (iii) chronic myocardial injury. Of 995 patients (36%) [median age 76 years (interquartile range 65-83)] with ≥2 HsTnT measurements and one >14 ng/L, 727 (73%) had chronic myocardial injury, 171 (17%) had Type-II MI, and 97 (9.7%) had Type-I MI; respective late mortality rates to 48 months were 33%, 43%, and 14% (P < 0.001). In-hospital angiography rates were 95% for patients with Type-I MI, [62% had percutaneous coronary intervention (PCI)] 24% (7% PCI) for those with Type-II MI, and 3.4% for chronic myocardial injury. On Cox modelling for mortality relative to Type 1 MI, adjusted hazard ratios were 1.94 [95% confidence intervals (CIs) 1.06-3.57]; P = 0.032 for Type 2 MI, and for chronic myocardial injury 1.14 (95% CIs 0.64-2.02); P = 0.66.

CONCLUSION

Among unselected patients undergoing HsTnT testing in EDs, Type-II MI including acute myocardial injury was more common than Type-I MI. Chronic myocardial injury, which occurred in three of four patients. Whereas patients with Type-II MI had higher late mortality than those with Type-I MI, after multivariable analyses mortality rates were marginally different.

Relation of Biomarkers of Cardiac Injury, Stress, and Fibrosis With Cardiac Mechanics in Patients ≥ 65 Years of Age

High sensitivity cardiac troponin T (hscTnT), soluble ST2 (sST2), N-terminal B-type natriuretic peptide (NT-proBNP), and galectin-3 are biomarkers of cardiac injury, stress, myocardial stretch, and fibrosis. Elevated levels are associated with poor outcomes. However, their association with cardiac mechanics in older persons is unknown. Associations between these biomarkers and cardiac mechanics derived from speckle tracking echocardiography, including left ventricular longitudinal strain (LVLS), early diastolic strain, and left atrial reservoir strain (LARS) were evaluated using standardized beta coefficients () in a cross sectional analysis with cardiac biomarkers in older patients without cardiovascular disease, low ejection fraction, or wall motion abnormalities. Biomarker associations with strain were attenuated by demographics and risk factors. In adjusted models, LVLS was associated with continuous measures of hscTnT (β^∧-0.06, p = 0.020), sST2 (β^∧ -0.05, p = 0.024) and NT-proBNP (β^∧ -0.06, p = 0.007). "High" levels (i.e., greater than prognostic cutpoint) of hscTnT (>13 ng/ml), sST2 (>35 ng/ml), and NT-proBNP (>190 pg/ml) were also associated with worse LVLS. In risk factor adjusted models, LARS was associated with hscTnT (β^∧ -0.08, p = 0.003) and NT-proBNP (β^∧-0.18, p <0.0001). High hscTnT (>13 ng/ml) and high NT-proBNP (>190 pg/ml) were also both associated with worse LARS. Gal-3 was not associated with any strain measure. In conclusion, in persons ≥ 65 years of age, without cardiovascular disease, low ejection fraction, or wall motion abnormalities, hscTnT, sST2, and NT-proBNP are associated with worse LVLS. HscTnT and NT-proBNP are associated with worse LARS. In conclusion, these subclinical increases in blood biomarkers, and their associations with subtle diastolic and systolic dysfunction, may represent pre-clinical heart failure.

Elevation of troponin I in acute ischemic stroke

Background. Cardiac morbidities account for 20% of deaths after ischemic stroke and is the second commonest cause of death in acute stroke population. Elevation of cardiac troponin has been regarded as a prognostic biomarker of poor outcome in patients with acute stroke.

Methods. This retrospective study enrolled 871 patients with acute ischemic stroke from August 2010 to March 2015. Data included vital signs, laboratory parameters collected in the emergency department, and clinical features during hospitalization. National Institutes of Health Stroke Scale (NIHSS), Barthel index, and modified Rankin Scale (mRS) were used to assess stroke severity and outcome.

Results. Elevated troponin I (TnI) > 0.01 µg/L was observed in 146 (16.8%) patients. Comparing to patients with normal TnI, patients with elevated TnI were older (median age 77.6 years vs. 73.8 years), had higher median heart rates (80 bpm vs. 78 bpm), higher median white blood cells (8.40 vs. 7.50 1,000/m³) and creatinine levels (1.40 mg/dL vs. 1.10 mg/dL), lower median hemoglobin (13.0 g/dL vs. 13.7 g/dL) and hematocrit (39% vs. 40%) levels, higher median NIHSS scores on admission (11 vs. 4) and at discharge (8 vs. 3), higher median mRS scores (4 vs3) but lower Barthel index scores (20 vs. 75) at discharge (p < 0.001). Multivariate analysis revealed that age ≥ 76 years (OR 2.25, CI [1.59–3.18]), heart rate ≥ 82 bpm (OR 1.47, CI [1.05–2.05]), evidence of clinical deterioration (OR 9.45, CI [4.27–20.94]), NIHSS score ≥ 12 on admission (OR 19.52, CI [9.59–39.73]), and abnormal TnI (OR 1.98, CI [1.18–3.33]) were associated with poor outcome. Significant factors for in-hospital mortality included male gender (OR 3.69, CI [1.45–9.44]), evidence of clinical deterioration (OR 10.78, CI [4.59–25.33]), NIHSS score ≥ 12 on admission (OR 8.08, CI [3.04–21.48]), and elevated TnI level (OR 5.59, CI [2.36–13.27]). C-statistics revealed that abnormal TnI improved the predictive power of both poor outcome and in-hospital mortality. Addition of TnI > 0.01 ug/L or TnI > 0.1 ug/L to the model-fitting significantly improved c-statistics for in-hospital mortality from 0.887 to 0.926 (p = 0.019) and 0.927 (p = 0.028), respectively.

Discussion. Elevation of TnI during acute stroke is a strong independent predictor for both poor outcome and in-hospital mortality. Careful investigation of possible concomitant cardiac disorders is warranted for patients with abnormal troponin levels.

Self-Assembly of Ferritin Nanoparticles into an Enzyme Nanocomposite with Tunable Size for Ultrasensitive Immunoassay

The self-assembly of nanoparticles into larger superstructures is a powerful strategy to develop novel functional nanomaterials, as these superstructures display collective properties that are different to those displayed by individual nanoparticles or bulk samples. However, there are increasing bottlenecks in terms of size control and multifunctionalization of nanoparticle assemblies. In this study, we developed a self-assembly strategy for construction of multifunctional nanoparticle assemblies of tunable size, through rational regulation of the number of self-assembling interaction sites on each nanoparticle. As proof-of-principle, a size-controlled enzyme nanocomposite (ENC) was constructed by self-assembly of streptavidin-labeled horseradish peroxidase (SA-HRP) and autobiotinylated ferritin nanoparticles (bFNP). Our ENC integrates a large number of enzyme molecules, together with a streptavidin-coated surface, allowing for a drastic increase in enzymatic signal when the SA is bound to a biotinylated target molecule. As result, a 10 000-fold increase in sensitivity over conventional enzyme-linked immunosorbent assays (ELISA) methods was achieved in a cardiac troponin immunoassay. Our method presented here should provide a feasible approach for constructing elaborate multifunctional superstructures of tunable size useful for a broad range of biomedical applications.

[Troponin elevation in ischemic stroke patients]

Cerebrovascular and cardiovascular diseases are major causes of death and disability worldwide. Ischemic stroke is a frequent complication in cardiac diseases and, vice versa, cardiac complications commonly cause early clinical worsening and death after stroke. In the emergency setting, cardiac biomarkers (preferably troponin, cTn) are measured frequently in patients presenting with acute ischemic stroke. The measurement of cTn is recommended by the guidelines for early management of patients with acute ischemic stroke from the American Heart Association. In case of pathologic cTn elevation, physicians are confronted with diagnostic and therapeutic uncertainties. Up-to-date recommendations on interpretation and consecutive actions remain ambiguous because cTn elevations may originate from causes other than acute coronary disease and because clinical signs and symptoms of acute coronary disease may be obscured by neurological deficits of the stroke. The application of modern, high-sensitive cTn assays that detect even minor cTn elevations has rather aggravated the dilemma of how to interpret this finding in patients with ischemic stroke.This article gives an overview on possible mechanisms of the frequently observed cTn elevation in ischemic stroke patients and offers help on interpretation and meaningful actions.

Effects of blood sample anticoagulants on lateral flow assays using luminescent photon-upconverting and Eu(III) nanoparticle reporters

Many quantitative and semiquantitative lateral flow (LF) assays have been introduced for clinical analytes such as biomarkers for cancer or acute myocardial infarction (AMI). Various detection technologies involving quantitative analyzing devices have been reported to have sufficient analytical sensitivity and quantification capability for clinical point-of-care tests. Fluorescence-based detection technologies such as quantum dots, Eu(III) nanoparticles, and photon-upconverting nanoparticles (UCNPs) have been introduced as promising solutions for point-of-care devices because of their high detectability by optical sensors. Lateral flow assays can be used for various sample types, e.g., urine, saliva, cerebrospinal fluid, and blood. This study focuses on the properties of serum and plasma because of their relevance in cancer and AMI diagnostics. The limit of detection was compared in LF assays having Eu(III) nanoparticles or UCNPs as reporters and the antibody configurations for two different analytes (prostate-specific antigen and cardiac troponin I (cTnI)). The results indicate a significant effect of anticoagulants in venipuncture tubes. The samples in K3EDTA tubes resulted in significant interference by decreased reporter particle mobility, and thus the limit of detection was up to eightfold less sensitive compared to serum samples. Despite the matrix interference in the cTnI assay with UCNP reporters, limits of detection of 41 ng/L with serum and 66 ng/L with the Li-heparin sample were obtained.

Diagnostic Role of High-Sensitivity Cardiac Troponin T in Acute Myocardial Infarction and Cardiac Noncoronary Artery Disease

BACKGROUND AND AIMS

Currently, the distinction between AMI and cardiac noncoronary artery disease (CNCD) remains a challenge in clinical practice. Our aim was to evaluate the diagnostic role of high-sensitivity cardiac troponin T (hs-cTnT) level at presentation and its change within the first hour to distinguish AMI from CNCD.

METHODS

hs-cTnT was measured at presentation and after 1 h in 110 consecutive Chinese patients with symptoms suggestive of AMI within 12 h from symptom onset. Receiver-operating characteristics (ROC) analysis was used to estimate the diagnostic accuracy of hs-cTnT.

RESULTS

Patients with AMI had higher presentation values of hs-cTnT and higher absolute changes in the first h than patients with CNCD. The diagnostic accuracy of hs-cTnT at presentation for the distinction between patients with AMI and CNCD as quantified by the area under the receiver-operating characteristics curve (AUC) was 0.88. The discriminatory power of Δhs-cTnT 0-1 h was higher for absolute (AUC, 0.89; 95% CI, 0.83-0.94) compared to relative (AUC, 0.64; 95% CI, 0.60-0.73) changes. Combining presentation values of hs-cTnT at presentation with absolute changes in the first h increased the AUC to 0.93 (p < 0.001 for comparison with AUC of 0 h hs-cTnT).

CONCLUSIONS

Overall, our results suggest that the combined use of presentation values of hs-cTnT and its absolute change in the first hour discriminates well between patients with AMI and CNCD, further confirming the role of hs-cTnT as a biomarker for the early diagnosis of AMI.

microRNA-based diagnostics and therapy in cardiovascular disease-Summing up the facts

Circulating microRNAs (miRNAs) are discussed as potential disease-specific biomarkers in cardiovascular disease. Their diagnostic value has been examined in numerous studies and animal models with respect to coronary artery disease (CAD) and myocardial infarction (MI) and the prognostic abilities of circulating miRNAs in risk stratification of future disease have been evaluated. Various miRNAs are described to complement protein-based biomarkers or classical risk factors in the diagnosis of CAD or MI and even represent potential new biomarkers in the discrimination of unstable angina pectoris (UAP). Signatures consisting of sets of multiple miRNAs seem to improve the predictive power compared to single miRNAs. Furthermore, the emerging field of miRNA-based therapeutics has reached cardiovascular research. The first promising in vitro results are raising hope for future clinical application. However, methods and material used for RNA isolation, miRNA detection and normalization steps still lack ways of standardization and need to be considered carefully. This article reviews the current knowledge of miRNAs in cardiovascular disease focusing on CAD and MI and will provide an overview regarding the use of circulating miRNAs as biomarkers and potential therapeutic targets in the field of CAD.

Measurement of high-sensitivity troponin T in noncardiac medical intensive care unit patients. Correlation to mortality and length of stay

OBJECTIVES

To assess the frequency, magnitude, and prognostic significance of elevations in cardiac troponin T in noncardiac critically ill patients, including elevations at levels below the limit of detection of traditional assays.

METHODS

Using a high-sensitivity assay, we measured troponin T (high-sensitivity troponin T [hsTnT]) in 451 unique patients within 12 hours of their admission to a noncardiac medical intensive care unit. Outcomes of patients, grouped by hsTnT level, were compared.

RESULTS

Overall, 98% of the study patients had detectable levels of hsTnT (>3 ng/L), and 33% had levels above the diagnostic cutoff of a traditional fourth-generation cardiac troponin T assay. Patient groups with higher hsTnT levels had markedly higher rates of in-hospital mortality (P < .001) and longer stays in the hospital and intensive care unit (P < .01).

CONCLUSIONS

In noncardiac critically ill patients, cardiac troponin T elevations are common but often at levels undetectable by traditional assays. hsTnT elevations predict a more complex clinical course and an increased risk of death.

Age- and sex-dependent upper reference limits for the high-sensitivity cardiac troponin T assay

OBJECTIVES

The study sought to determine the 99th percentile upper reference limit for the high-sensitivity cardiac troponin T assay (hs-cTnT) in 3 large independent cohorts.

BACKGROUND

The presently recommended 14 ng/l cut point for the diagnosis of myocardial infarction using the hs-cTnT assay was derived from small studies of presumably healthy individuals, with relatively little phenotypic characterization.

METHODS

Data were included from 3 well-characterized population-based studies: the Dallas Heart Study (DHS), the Atherosclerosis Risk in Communities (ARIC) Study, and the Cardiovascular Health Study (CHS). Within each cohort, reference subcohorts were defined excluding individuals with recent hospitalization, overt cardiovascular disease, and kidney disease (subcohort 1), and further excluding those with subclinical structural heart disease (subcohort 2). Data were analyzed stratified by age, sex, and race.

RESULTS

The 99th percentile values for the hs-cTnT assay in DHS, ARIC, and CHS were 18, 22, and 36 ng/l (subcohort 1) and 14, 21, and 28 ng/l (subcohort 2), respectively. These differences in 99th percentile values paralleled age differences across cohorts. Analyses within sex/age strata yielded similar results between cohorts. Within each cohort, 99th percentile values increased with age and were higher in men. More than 10% of men 65 to 74 years of age with no cardiovascular disease in our study had cardiac troponin T values above the current myocardial infarction threshold.

CONCLUSIONS

Use of a uniform 14 ng/l cutoff for the hs-cTnT assay may lead to over-diagnosis of myocardial infarction, particularly in men and the elderly. Clinical validation is needed of new age- and sex-specific cutoff values for this assay.

The clinical value of serial measurement of high-sensitivity cardiac troponin T in acute exacerbations ofchronic obstructive pulmonary disease

Objective

To assess the prevalence and long-term prognostic value of a dynamic (rise/fall) pattern of cardiac troponin T (hs-cTnT) elevation during acute exacerbation of chronic obstructive pulmonary disease (AECOPD) compared with a stable hs-cTnT elevation.

Methods

Prospective cohort study of unselected patients admitted with AECOPD to the emergency room of a university hospital. Serial hs-cTnT measurements were made during admission. Survival after a median of 1.8 years was recorded.

Results

83 patients with a mean age of 72 years and a mean forced expiratory volume in 1 s (FEV₁) of 0.9 L. The mortality rate was 62%. The median hs-cTnT at admission was 27 ng/L (IQR 13.4–51)). 65 patients (78%) had at least one hs-cTnT measurement ≥14 ng/L, and among these the median change in hs-cTnT was 50.7% (IQR 25.2–89.4). Of the patients with serial hs-cTnT measurements, 53 (82%) had a dynamic pattern (ie, ΔTnT ≥20%). In multivariate analysis, stable hs-cTnT elevation was associated with increasing age (OR per 5 years with 95% CI 1.9 (1.01 to 3.7), p=0.045) and low Hb (OR 7.3 (1.1 to 49), p=0.039). Stable hs-cTnT elevation was associated with increased mortality with an HR of 2.4 (95%CI 1.1 to 5.3, p=0.027) in the multivariate Cox regression analysis.

Conclusions

Among the patients with at least one hs-cTnT above the 99th centile, 82% had a rise/fall pattern, as requested to make a diagnosis of myocardial infarction. Compared to a dynamic rise/fall pattern of hs-cTnT, a stable and moderately elevated hs-cTnT during AECOPD is associated with poor long-term prognosis.

Early diagnosis of myocardial infarction using absolute and relative changes in cardiac troponin concentrations

BACKGROUND

Absolute changes in high-sensitivity cardiac troponin T (hs-cTnT) seem to have higher diagnostic accuracy in the early diagnosis of acute myocardial infarction compared with relative changes. It is unknown whether the same applies to high-sensitivity cardiac troponin I (hs-cTnI) assays and whether the combination of absolute and relative change might further increase accuracy.

METHODS

In a prospective, international multicenter study, high-sensitivity cardiac troponin (hs-cTn) was measured with 3 novel assays (hs-cTnT, Roche Diagnostics Corp, Indianapolis, Ind; hs-cTnI, Beckman Coulter Inc, Brea, Calif; hs-cTnI, Siemens, Munich, Germany) in a blinded fashion at presentation and after 1 and 2 hours in a blinded fashion in 830 unselected patients with suspected acute myocardial infarction. The final diagnosis was adjudicated by 2 independent cardiologists.

RESULTS

The area under the receiver operating characteristic curve for diagnosing acute myocardial infarction was significantly higher for 1- and 2-hour absolute versus relative hs-cTn changes for all 3 assays (P < .001). The area under the receiver operating characteristic curve of the combination of 2-hour absolute and relative change (hs-cTnT 0.98 [95% confidence interval {CI}, 0.97-0.99]; hs-cTnI, Beckman Coulter Inc, 0.97 [95% CI, 0.96-0.99]; hs-cTnI, Siemens, 0.96 [95% CI, 0.93-0.99]) were high and provided some benefit compared with the use of absolute change alone for hs-cTnT, but not for the hs-cTnI assays. Reclassification analysis confirmed the superiority of absolute changes versus relative changes.

CONCLUSIONS

Absolute changes seem to be the preferred metrics for both hs-cTnT and hs-cTnI in the early diagnosis of acute myocardial infarction. The combination of absolute and relative changes provides a small added value for hs-cTnT, but not for hs-cTnI.

Glycogen phosphorylase isoenzyme BB plasma kinetics is not related to myocardial ischemia induced by exercise stress echo test

BACKGROUND

Glycogen phosphorylase BB (GPBB) is released from cardiac cells during myocyte damage. Previous studies have shown contradictory results regarding the relation of enzyme release and reversible myocardial ischemia. The aim of this study was to determine the plasma kinetics of GPBB as a response to the exercise stress echocardiographic test (ESET), and to define the relationship between myocardial ischemia and enzyme plasma concentrations.

METHODS

We studied 46 consecutive patients undergoing ESET, with recent coronary angiography. In all patients, a submaximal stress echo test according to Bruce protocol was performed. Concentration of GPBB was measured in peripheral blood that was sampled 5 min before and 10, 30 and 60 min after ESET.

RESULTS

There was significant increase of GPBB concentration after the test (p=0.021). Significant increase was detected 30 min (34.9% increase, p=0.021) and 60 min (34.5% increase, p=0.016) after ESET. There was no significant effect of myocardial ischemia on GPBB concentrations (p=0.126), and no significant interaction between sampling intervals and myocardial ischemia, suggesting a similar release profile of GPBB in ischemic and non-ischemic conditions (p=0.558). Patients in whom ESET was terminated later (stages 4 or 5 of standard Bruce protocol; n=13) had higher GPBB concentrations than patients who terminated ESET earlier (stages 1, 2 or 3; n=33) (p=0.049). Baseline GPBB concentration was not correlated to any of the patients' demographic, clinical and hemodynamic characteristics.

CONCLUSIONS

GPBB plasma concentration increases after ESET, and it is not related to inducible myocardial ischemia. However, it seems that GPBB release during ESET might be related to exercise load/duration.

Delta troponin for the early diagnosis of AMI in emergency patients with chest pain

OBJECTIVES

In patients presenting to the Emergency Department (ED) with potential acute myocardial infarction (AMI), elevated cardiac troponin (cTn) levels are indicative of myocardial necrosis. We assessed the accuracy of 'delta cTn' at 2h or 6h compared to the cTn concentration above the 99th percentile reference value for AMI in a prospective study of adult patients presenting to ED with symptoms suggestive of possible acute coronary syndrome.

METHODS

Blood was sampled for cardiac troponin I (cTnI) on presentation, and at 2h and 6h following presentation using a sensitive assay (Beckman AccuTnI). All clinical endpoints were adjudicated by a cardiologist who was blinded to the 2h cTn assay result.

RESULTS

Of the 874 patients, 70 (8%) were diagnosed with an AMI during their index presentation. The area under the ROC curve for diagnosing AMI at 2h was 0.89 [95%CI, 0.84-0.95] for absolute delta cTn versus 0.79 [95%CI 0.73-0.85] for the relative change. Specificity and PPV at 2h were optimized using a delta cTnI ≥ 0.03 μg/L (95.8% [95%CI 94.1-97.0] and 61.4% [95%CI 50.9-70.9] respectively). Sensitivity and NPV for AMI were optimized using the 99th percentile with the addition of a delta of<0.03 μg/L (97.1% [95%CI 90.2-99.2] and 99.7% [95%CI 99-99.9] respectively).

CONCLUSIONS

An algorithm incorporating cTnI concentration and delta cTn values with a sensitive troponin assay allows accurate diagnosis of AMI within 2h from presentation and earlier rule-out of AMI in the majority of patients.

Risk stratification in patients with unstable angina using absolute serial changes of 3 high-sensitive troponin assays

BACKGROUND

It is unknown whether unstable angina (UA) results in previously nondetectable low-level myocardial necrosis. We compared the pattern of myocardial necrosis between patients with UA, acute myocardial infarction (AMI), and noncardiac chest pain (NCCP) using 3 high-sensitive cardiac troponin (hs-cTn) assays.

METHODS

In a multicenter study, we enrolled 842 unselected patients with acute chest pain in the emergency department. Roche hs-cTnT, Beckman Coulter hs-cTnI, and Siemens hs-cTnI were determined in a blinded fashion at presentation and after 1, 2, 3, and 6 hours. The final diagnosis was adjudicated by 2 independent cardiologists.

RESULTS

A change in hs-cTn of ≥2 ng/L within the first hour after presentation as assessed with Roche hs-cTnT, Beckman Coulter hs-cTnI, and Siemens hs-cTnI was observed in 26%, 31%, and 32% of patients with UA (n = 115) compared with 91%, 92%, and 96% in patients with AMI (n = 120) and 12%, 23%, and 16% in patients with NCCP (n = 415; P < .001 for all comparisons between UA and AMI, P > .05 for all comparisons between UA and NCCP). In patients with UA, such a 1-hour change in hs-cTn of ≥2 ng/L was associated with an increased risk of death or AMI during the 30-day follow-up (P = .003, .03, .03) and 2-year follow-up (P < .001, .002, and .006).

CONCLUSIONS

In marked contrast to patients with AMI, most patients with UA do not exhibit relevant hs-cTn changes. The minority of UA with hs-cTn changes, however, has a significantly worse short- and long-term outcome.

Single resting hsTnT level predicts abnormal myocardial stress test in acute chest pain patients with normal initial standard troponin

OBJECTIVES

The goal of this study was to determine the ability of a single, resting high-sensitivity troponin T (hsTnT) measurement to predict abnormal myocardial perfusion imaging (MPI) in patients presenting with acute chest pain to the emergency department (ED).

BACKGROUND

HsTnT assays precisely detect very low levels of troponin T, which may be a surrogate for the presence and extent of myocardial ischemia.

METHODS

We included all patients from the ROMICAT I (Rule Out Myocardial Infarction Using Computer Assisted Tomography) trial, an observational cohort study, who underwent both single-photon emission computed tomography (SPECT)-MPI stress testing and 64-slice computed tomography angiography (CTA) and in whom hsTnT measurements were available. We assessed the discriminatory value of hsTnT for abnormal SPECT-MPI and the association of reversible myocardial ischemia by SPECT-MPI and the extent of coronary atherosclerosis by CTA to hsTnT levels.

RESULTS

Of the 138 patients (mean age 54 ± 11 years, 46% male), 19 (13.7%) had abnormal SPECT-MPI. Median hsTnT levels were significantly different between patients with normal and abnormal SPECT-MPI (9.41 pg/ml [interquartile range (IQR): 5.73 to 19.20 pg/ml] vs. 4.89 pg/ml [IQR: 2.34 to 7.68 pg/ml], p = 0.001). Sensitivity of 80% and 90% to detect abnormal SPECT-MPI was reached at hsTnT levels as low as 5.73 and 4.26 pg/ml, respectively. Corresponding specificity was 62% and 46%, and negative predictive value was 96% and 96%, respectively. HsTnT levels had good discriminatory ability for prediction of abnormal SPECT-MPI (area under the curve: 0.739, 95% confidence interval: 0.609 to 0.868). Both reversible myocardial ischemia and the extent of coronary atherosclerosis (combined model r(2) = 0.19 with partial of r(2) = 0.12 and r(2) = 0.05, respectively) independently and incrementally predicted the measured hsTnT levels.

CONCLUSIONS

In patients with acute chest pain, myocardial perfusion abnormalities and coronary artery disease are predicted by resting hsTnT levels. Prospective evaluations are warranted to confirm whether resting hsTnT could serve as a powerful triage tool in chest pain patients in the ED before diagnostic testing and improve the effectiveness of patient management.

Short- and long-term individual variation in cardiac troponin in patients with stable coronary artery disease

BACKGROUND

A rise or fall of cardiac troponin is a prerequisite for the diagnosis of acute myocardial infarction. Defining significant changes requires knowledge of both biological and analytical variation. The short-term biological variation of cardiac troponin in healthy individuals is 3%-48%. However, healthy individuals may not be representative for patients in whom cardiac troponin measurement is often of clinical importance. Therefore, we studied the individual variation of cardiac troponin in patients with symptoms of stable coronary artery disease.

METHODS

Twenty-four patients scheduled for elective coronary angiography were included. Blood samples were drawn once at enrollment and serially at six 4-h intervals on the day before coronary angiography. Cardiac troponin was measured with hs-cTn assays from Abbott Laboratories (premarket cTnI assay) and Roche Diagnostics (Elecsys(®) cTnT assay with two different lots).

RESULTS

The short-term individual variation in cardiac troponin I (cTnI) was 14%, the reference change value (RCV) 49%, and RCV-log-normal (rise/fall) 54%/-35%. The corresponding values for cTnT were 7%, 23%, and 26%/-21%. The long-term variation for cTnI was 24%, RCV 69%, and RCV-log-normal (rise/fall) 97%/-49%. The corresponding values for cTnT were 11%, 32%, and 37%/-27%.

CONCLUSIONS

The short-term individual variation of cardiac troponin in patients with symptoms of stable coronary artery disease is similar to the biological variation previously demonstrated in healthy individuals. Our results suggest that a change in cardiac troponin concentrations of >50% can be used in attempting to diagnose acute myocardial injury. To detect significant long-term changes in cardiac troponin concentrations, larger changes will be required.

Comparison of diagnostic accuracy between three different rules of interpreting high sensitivity troponin T results

With the introduction of high sensitivity troponin-T (hs-TnT) assay, clinicians face more patients with 'positive' results but without myocardial infarction. Repeated hs-TnT determinations are warranted to improve specificity. The aim of this study was to compare diagnostic accuracy of three different interpretation rules for two hs-TnT results taken 6 h apart. After adjusting for clinical differences, hs-TnT results were recoded according to the three rules. Rule1: hs-TnT >13 ng/L in at least one determination. Rule2: change of >20 % between the two measures. Rule3: change >50 % if baseline hs-TnT 14-53 ng/L and >20 % if baseline >54 ng/L. The sensitivity, specificity and ROC curves were compared. The sensitivity analysis was used to generate post-test probability for any test result. Primary outcome was the evidence of coronary critical stenosis (CCS) on coronary angiography in patients with high-risk chest pain. 183 patients were analyzed (38.3 %) among all patients presenting with chest pain during the study period. CCS was found in 80 (43.7 %) cases. The specificity was 0.62 (0.52-0.71), 0.76 (0.66-0.84) and 0.83 (0.74-0.89) for rules 1, 2 and 3, respectively (P < 0.01). Sensitivity decreased with increasing specificity (P < 0.01). Overall diagnostic accuracy did not differ among the three rules (AUC curves difference P = 0.12). Sensitivity analysis showed a 25 % relative gain in predicting CCS using rule 3 compared to rule 1. Changes between two determinations of hs-TnT 6 h apart effectively improved specificity for CCS presence in high-risk chest pain patients. There was a parallel loss in sensitivity that discouraged any use of such changes as a unique way to interpret the new hs-TnT results.

Prognostic significance of elevated cardiac troponin-T levels in acute respiratory distress syndrome patients

BACKGROUND

Elevated levels of biochemical markers of myocardial necrosis have been associated with worsened outcomes in Acute Respiratory Distress Syndrome (ARDS), but there are few prospective data on this relationship. We investigated elevated cardiac troponin T (cTnT) levels and their relationship with outcome in patients with ARDS.

METHODS

A prospective cohort study of patients with ARDS was conducted at a tertiary-care academic medical center. Patients had blood taken within 48 hours of ARDS onset and assayed for cTnT. Patients were followed for the outcomes of 60-day mortality, number of organ failures, and days free of mechanical ventilation. Echocardiographic and electrocardiographic (ECG) data were analyzed for signs of myocardial ischemia, infarction, or other myocardial dysfunction.

RESULTS

177 patients were enrolled, 70 of whom died (40%). 119 patients had detectable cTnT levels (67%). Median cTnT level was 0.03 ng/mL, IQR 0-0.10 ng/mL, and levels were higher among non-survivors (P = .008). Increasing cTnT level was significantly associated with increasing mortality (P = .008). The association between increasing cTnT level and mortality remained significant after adjustment in a multivariate model (HR(adj) = 1.45, 95% CI 1.17-1.81, P = .001). Elevated cTnT level was also associated with increased number of organ failures (P = .002), decreased number of days free of mechanical ventilation (P = .03), echocardiographic wall motion abnormalities (P = 0.001), and severity of tricuspid regurgitation (P = .04). There was no association between ECG findings of myocardial ischemia or infarction and elevated cTnT.

CONCLUSIONS

Elevated cTnT levels are common in patients with ARDS, and are associated with worsened clinical outcomes and certain echocardiographic abnormalities. No association was seen between cTnT levels and ECG evidence of coronary ischemia.

Release Kinetics of Cardiac Biomarkers in Patients Undergoing Transcoronary Ablation of Septal Hypertrophy

BACKGROUND

The release kinetics of cardiac troponin T measured with conventional vs high-sensitivity cardiac troponin T (hs-cTnT) assays in patients with acute myocardial infarction (AMI) is difficult to establish.

METHODS

We analyzed the release kinetics of cTnT measured by fourth generation and high-sensitivity assays, creatine kinase-MB (CK-MB), and myoglobin in patients with hypertrophic obstructive cardiomyopathy undergoing transcoronary ablation of septal hypertrophy (TASH), a model of AMI. Consecutive patients (n = 21) undergoing TASH were included. Serum and EDTA-plasma samples were collected before and at 15, 30, 45, 60, 75, 90, and 105 min, and 2, 4, 8, and 24 h after TASH.

RESULTS

cTnT concentrations measured by the hs assay were significantly increased at 15 min [21.4 ng/L, interquartile range (IQR) 13.3–39.7 ng/L vs 11.3 ng/L, IQR 6.0–18.8 ng/L at baseline; P = 0.031]. In comparison, cTnT concentrations measured by the conventional fourth generation assay increased significantly at 60 min (30.0 ng/L, IQR 20.0–30.0 ng/L vs &lt;10.0 ng/L, IQR &lt;10.0–10.0 ng/L; P &lt; 0.01), CK-MB at 90 min (8.4 μg/L, IQR 6.9–14.4 μg/L vs 0.9 μg/L, IQR 0.4–1.1 μg/L; P &lt; 0.01), and myoglobin at 30 min (188.0 μg/L, IQR 154.0–233.0 μg/L vs 38.0 μg/L, IQR 28.0–56.0; P &lt; 0.01).

CONCLUSIONS

cTnT concentrations measured by the hs assay were significantly increased after TASH at all of the time points, with a doubling at 15 min after induction of AMI, confirming earlier evidence of myocardial injury compared to the fourth generation cTnT assay and CK-MB and myoglobin.

High-sensitivity cardiac troponin in the distinction of acute myocardial infarction from acute cardiac noncoronary artery disease

BACKGROUND

We hypothesized that high-sensitivity cardiac troponin (hs-cTn) and its early change are useful in distinguishing acute myocardial infarction (AMI) from acute cardiac noncoronary artery disease.

METHODS AND RESULTS

In a prospective, international multicenter study, hs-cTn was measured with 3 assays (hs-cTnT, Roche Diagnostics; hs-cTnI, Beckman-Coulter; hs-cTnI Siemens) in a blinded fashion at presentation and serially thereafter in 887 unselected patients with acute chest pain. Accuracy of the combination of presentation values with serial changes was compared against a final diagnosis adjudicated by 2 independent cardiologists. AMI was the adjudicated final diagnosis in 127 patients (15%); cardiac noncoronary artery disease, in 124 (14%). Patients with AMI had higher median presentation values of hs-cTnT (0.113 μg/L [interquartile range, 0.049-0.246 μg/L] versus 0.012 μg/L [interquartile range, 0.006-0.034 μg/L]; P<0.001) and higher absolute changes in hs-cTnT in the first hour (0.019 μg/L [interquartile range, 0.007-0.067 μg/L] versus 0.001 μg/L [interquartile range, 0-0.003 μg/L]; P<0.001) than patients with cardiac noncoronary artery disease. Similar findings were obtained with the hs-cTnI assays. Adding changes of hs-cTn in the first hour to its presentation value yielded a diagnostic accuracy for AMI as quantified by the area under the receiver-operating characteristics curve of 0.94 for hs-cTnT (0.92 for both hs-cTnI assays). Algorithms using ST-elevation, presentation values, and changes in hs-cTn in the first hour accurately separated patients with AMI and those with cardiac noncoronary artery disease. These findings were confirmed when the final diagnosis was readjudicated with the use of hs-cTnT values and validated in an independent validation cohort.

CONCLUSION

The combined use of hs-cTn at presentation and its early absolute change excellently discriminates between patients with AMI and those with cardiac noncoronary artery disease.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00470587.

Cardiac biomarkers in the intensive care unit

Cardiac biomarkers (CB) were first developed for assisting the diagnosis of cardiac events, especially acute myocardial infarction. The discoveries of other CB, the better understanding of cardiac disease process and the advancement in detection technology has pushed the applications of CB beyond the 'diagnosis' boundary. Not only the measurements of CB are more sensitive, the applications have now covered staging of cardiac disease, timing of cardiac events and prognostication. Further, CB have made their way to the intensive care setting where their uses are not just confined to cardiac related areas. With the better understanding of the CB properties, CB can now help detecting various acute processes such as pulmonary embolism, sepsis-related myocardial depression, acute heart failure, renal failure and acute lung injury. This article discusses the properties and the uses of common CB, with special reference to the intensive care setting. The potential utility of "multimarkers" approach and microRNA as the future CB are also briefly discussed.