Cardiac troponin I in the diagnosis of myocardial injury and infarction

Evaluation of the analytical and clinical performance of a new high-sensitivity cardiac troponin I assay: hs-cTnI (CLIA) assay

OBJECTIVES

Cardiac troponin (cTn) is the key biomarker for diagnosis of acute coronary syndrome (ACS). We performed a complete assessment of the high-sensitivity cardiac troponin I (hs-cTnI) (CLIA) assay on the analytical performance and clinical diagnostic performance, which was compared with Abbott ARCHITECT hs-cTnI assay.

METHODS

Sex-specific 99th percentile upper reference limits (URLs) were determined from a healthy population of 424 males and 408 females. High-sensitivity performance was assessed by examining the imprecision at sex-specific URLs and the detectable results above LoD in a cohort of healthy population. The diagnostic performance of the hs-cTnI (CLIA) assay was validated in a population of 934 patients with suspected ACS.

RESULTS

The 99th percentile URLs were 15.3 ng/L for female, 31.3 ng/L for male and 24.2 ng/L for overall population. The total imprecision near the sex-specific 99th percentile URLs were <5 %. 76.74 % of females, 97.12 % of males and 86.69 % of overall population had cTnI values exceeding the LoD, which met the criteria of high-sensitivity troponin assay. No cross-reactivity or interference was identified. The diagnostic sensitivity, specificity, PPV, NPV, and AUC of hs-cTnI (CLIA) assay were 97.97 , 90.70, 79.02, 99.21 % and 0.9885, respectively, which were comparable to ARCHITECT hs-cTnI assay.

CONCLUSIONS

hs-cTnI (CLIA) assay is a high-sensitivity troponin I method with high precision, sensitivity and specificity. The clinical diagnostic performance of hs-cTnI (CLIA) is comparable to the established ARCHITECT hs-cTnI assay. Mindray's hs-cTnI (CLIA) assay is an attractive alternative for diagnosis of myocardial infarction with a high level of accuracy and safety.

Chemical-Chemical Redox Cycle Signal Amplification Strategy Combined with Dual Ratiometric Immunoassay for Surface-Enhanced Raman Spectroscopic Detection of Cardiac Troponin I

Improving the sensitivity and reproducibility of surface-enhanced Raman spectroscopy (SERS) methods for the detection of bioactive molecules is crucial in biological process research and clinical diagnosis. Herein, we designed a novel SERS platform for cardiac troponin I (cTnI) detection by a chemical-chemical redox cycle signal amplification strategy combined with a dual ratiometric immunoassay. First, ascorbic acid (AA) was generated by enzyme-assisted immunoreaction with a cTnI-anchored sandwich structure. Then, oxidized 4-mercaptophenol (ox4-MP) was reacted with AA to produce 4-mercaptophenol (4-MP). Quantitative analysis of cTnI was realized by a Raman signal switch between ox4-MP and 4-MP. Specifically, AA could be regenerated by reductant (tris(2-carboxyethyl) phosphine, TCEP), which in turn produced more signal indicator 4-MP, causing significant signal amplification for cTnI analysis by SERS immunosensing. Moreover, a dual ratiometric-type SERS method was established with the intensity ratio I1077/I822 and I633/I822, which improved the reproducibility of the cTnI assay. The excellent performance of the chemical-chemical redox cycle strategy and ratio-type SERS assay endows the method with high sensitivity and reproducibility. The linear ranges of cTnI were 0.001 to 50.0 ng mL-1 with detection limits of 0.33 pg mL-1 (upon I1077/I822) and 0.31 pg mL-1 (upon I635/I822), respectively. The amount of cTnI in human serum samples yielded recoveries from 89.0 to 114%. This SERS method has remarkable analytical performance, providing an effective approach for the early diagnosis of cardiovascular diseases, and has great latent capacity in the sensitive detection of bioactive molecules.

Acetogenin-induced fibrotic heart disease from avocado (Persea americana, Lauraceae) poisoning in horses

Poisoning by avocado (Persea americana) has been confirmed in sheep, goats, dogs, rabbits and ostriches. The clinical signs and lesions are attributed to the acetogenin, persin. Little is known regarding the epidemiology, clinical signs, lesions and therapy caused by acetogenin-induced heart damage. During the two-year study, we investigated a horse farm with six horses that often fed themselves with P. americana leaves or mature fruit pulp and skin on the ground. Two horses died, and one underwent necropsy, histopathology, and immunohistochemistry using the anti-cardiac troponin C (cTnC). Grossly and histopathologically, there was severe cardiac fibroplasia. Immunohistochemically, there was a multifocal decrease or negative expression in the cTnC cardiomyocytes' cytoplasm. Persea americana leaves were confirmed in the alimentary tract using botanical anatomy and molecular techniques. The chemical investigation by (LC-ESI-MS) revealed the presence of the acetogenins, persin and avocadene 1-acetate from P. americana. Persin was present in leaves and fruits (seed and pulp), while avocadene 1-acetate was found in leaves and fruits (seed, peel, and pulp) with a higher concentration in the pulp. Four other horses have been examined by electrocardiogram, echocardiogram and serum Troponin 1 (cTnI). To establish a causal effect of consumption of P. Americana and heart fibroplasia in horses, long-time experiments must be carried out.

Biomarkers for Myocarditis and Inflammatory Cardiomyopathy

Purpose of Review

Myocarditis is a disease caused by inflammation of the heart that can progress to dilated cardiomyopathy, heart failure, and eventually death in many patients. Several etiologies are implicated in the development of myocarditis including autoimmune, drug-induced, infectious, and others. All causes lead to inflammation which causes damage to the myocardium followed by remodeling and fibrosis. This review aims to summarize recent findings in biomarkers for myocarditis and highlight the most promising candidates.

Recent Findings

Current methods of diagnosing myocarditis, including imaging and endomyocardial biopsy, are invasive, expensive, and often not done early enough to affect progression. Research is being done to find biomarkers of myocarditis that are cost-effective, accurate, and prognostically informative. These biomarkers would allow for earlier screening for myocarditis, as well as earlier treatment, and a better understanding of the disease course for specific patients.

Summary

Early diagnosis of myocarditis with biomarkers may allow for prompt treatment to improve outcomes in patients.

Current Use of Cardiac Biomarkers in Various Heart Conditions

Biomarkers are increasingly recognized to have significant clinical value in early identification and progression of various cardiovascular diseases. There are many heart conditions, such as congestive heart failure (CHF), ischemic heart diseases (IHD), and diabetic cardiomyopathy (DCM), and cardiac remodeling, in which the severity of the cardiac pathology can be mirrored through these cardiac biomarkers. From the emergency department (ED) evaluation of acute coronary syndromes (ACS) or suspected acute myocardial infarction (AMI) with cardiac marker Troponin to the diagnosis of chronic conditions like Heart Failure (HF) with natriuretic peptides, like B-type natriuretic peptide (BNP), N-terminal pro-B- type natriuretic peptide (Nt-proBNP) and mid regional pro-atrial natriuretic peptide (MR- proANP), their use is continuously increasing. Their clinical importance has led to the discovery of newer biomarkers, such as the soluble source of tumorigenicity 2 (sST2), galectin-3 (Gal-3), growth differentiation factor-15 (GDF-15), and various micro ribonucleic acids (miRNAs). Since cardiac pathophysiology involves a complex interplay between inflammatory, genetic, neurohormonal, and biochemical levels, these biomarkers could be enzymes, hormones, and biologic substances showing cardiac injury, stress, and malfunction. Therefore, multi-marker approaches with different combinations of novel cardiac biomarkers, and continual assessment of cardiac biomarkers are likely to improve cardiac risk prediction, stratification, and overall patient wellbeing. On the other hand, these biomarkers may reflect coexisting or isolated disease processes in different organ systems other than the cardiovascular system. Therefore, knowledge of cardiac biomarkers is imperative. In this article, we have reviewed the role of cardiac biomarkers and their use in the diagnosis and prognosis of various cardiovascular diseases from different investigations conducted in recent years.

Cardiac Effects of Treadmill Running at Different Intensities in a Rat Model

Purpose: In this study, we investigated the effect of treadmill exercise training on cardiac hypertrophy, collagen deposition, echo parameters and serum levels of cardiac troponin I (cTnI) in rats, and how they differ with various exercise intensities, hence exploring potential signal transduction. Methods: Male Sprague-Dawley rats were randomly divided into sedentary (SED), low-intensity running (LIR), medium-intensity running (MIR), and high-intensity running (HIR) groups. Each exercise group had 3 subgroups that were sacrificed for cardiac tissue analyses at 1, 4, and 8 weeks, respectively, and all rats participated in a daily 1 h treadmill routine 5 days per week. Echocardiographic measurements were performed 24 h after the last exercise session. Additionally, myocardium samples and blood were collected for histological and biochemical examinations. Changes in the extracellular signal-regulated kinases 1/2 (ERK1/2) signal pathway were detected by Western blotting. Results: After a week of running, ventricular myocyte size and the phosphorylation of ERK1/2 increased in the HIR group, while left ventricular (LV) diastolic diameter values and LV relative wall thickness increased in the LIR and MIR groups. In addition, we observed heart enlargement, cTnI decrease, and ERK1/2 signal activation in each of the exercise groups after 4 weeks of running. However, the HIR group displayed substantial rupture and increased fibrosis in myocardial tissue. In addition, compared with the LIR and MIR groups, 8 weeks of HIR resulted in structural damage, fiber deposition, and increased cTnI. However, there was no difference in the activation of ERK1/2 signaling between the exercise and SED groups. Conclusion: The effect of running on cardiac hypertrophy was intensity dependent. In contrast to LIR and MIR, the cardiac hypertrophy induced by 8 weeks of HIR was characterized by potential cardiomyocyte injury, which increased the risk of pathological development. Furthermore, the ERK signaling pathway was mainly involved in the compensatory hypertrophy process of the myocardium in the early stage of exercise and was positively correlated with exercise load. However, long-term exercise may attenuate ERK signaling activation.

Clinical Utility of Cardiac Troponin I and Cardiac Troponin T Measurements

The measurement of CK-MB remains the test of choice for confirmation or exclusion of AMI and probably will remain the test of choice for routine diagnosis in the near future. Nowadays determination of cardiac troponin T (cTnT) and cardiac troponin I (cTnI) as a method relatively expensive and time-consuming should be restricted to clinical settings that really require their high specificity.

Identifying Cardiac Diseases using Cardiac Biomarkers in Rhesus Macaques (Macaca mulatta)

Cardiac biomarkers are an important tool for diagnosing cardiac diseases in both human and veterinary patients. Serum concentrations of N-terminal probrain natriuretic peptide (NT-proBNP) and cardiac troponin I (cTnI) have been used to indicate the presence of various cardiac diseases including hypertrophic cardiomyopathy (HCM) in various species including humans. However, these cardiac biomarkers have not been established as a diagnostic tool for detecting cardiac disease in rhesus macaques. In the rhesus macaque colony at the California National Primate Research Center, naturally occurring HCM and various other cardiac diseases have been identified. In this study, commercially available assays were used to measure serum cTnI and NT-proBNP concentrations to evaluate their utility as a diagnostic screening tool for cardiac diseases in rhesus macaques. This study revealed that the serum cTnI concentration was significantly higher in animals with echocardiographically apparent cardiac disease as compared with the animals that had no cardiac structural and functional changes (the control group). However, no significant differences were detected between animals with HCM and non-HCM cardiac disease. Because the area under the receiver operating characteristic curve was 0.81 when the serum cTnI was compared between the control and cardiac disease groups, serum cTnI was considered a moderately accurate test to predict the presence of cardiac disease. The optimal cut-off value of serum cTnI concentration for diagnosis of cardiac disease was 0.0085 ng/mL, with a sensitivity of 0.68 and specificity of 0.94. Significant but weak correlations were noted between the serum cTnI concentration and several echocardiographic parameters. Conversely, no significant differences in NT-proBNP concentrations were detected between animals with and without cardiac diseases. In conclusion, measurement of serum cTnI can be used to aid in diagnosing cardiac diseases in rhesus macaques. However, cTnI measurement does not replace echocardiographic evaluation to diagnose cardiac diseases in rhesus macaques due to the poor sensitivity of the assay and the weak correlation to with more established echocardiographic markers for cardiac disease.

miR-21-5p as a potential biomarker of inflammatory infiltration in the heart upon acute drug-induced cardiac injury in rats

Investigation of genomic changes in cardiotoxicity can provide novel biomarkers and insights into molecular mechanisms of drug-induced cardiac injury (DICI). The main objective of this study was to identify and characterize dysregulated microRNAs (miRNAs) in the heart associated with cardiotoxicity. Wistar rats were dosed once with either isoproterenol (1.5 mg/kg, i.p), allylamine (100 mg/kg, p.o.) or the respective vehicle controls. Heart tissue was collected at 24 h, 48 h and 72 h post-drug administration and used for histopathological assessment, miRNA profiling, immunohistochemical analysis and in situ hybridization. Multiplex analysis of 68 miRNAs in the heart revealed a significant upregulation of several miRNAs (miR-19a-3p, miR-142-3p, miR-155-5p, miR-208b-3p, miR-21-5p) after isoproterenol and one miRNA (miR-21-5p) after allylamine administration. Localization of miR-21-5p was specific to inflammatory cell infiltrates in the heart after both treatments. Immunohistochemical analysis of Stat3, a known miR-21-5p regulator, also confirmed its upregulation in cardiomyocytes and inflammatory cell infiltrates. The toxicity signatures based on miRNA networks, identified in vivo, can potentially be used as mechanistic biomarkers as well as to study cardiotoxicity in vitro in order to develop sensitive tools for early hazard identification and risk assessment.

Troponin through the looking-glass: emerging roles beyond regulation of striated muscle contraction

Troponin is a heterotrimeric Ca²⁺-binding protein that has a well-established role in regulating striated muscle contraction. However, mounting evidence points to novel cellular functions of troponin, with profound implications in cancer, cardiomyopathy pathogenesis and skeletal muscle aging. Here, we highlight the non-canonical roles and aberrant expression patterns of troponin beyond the sarcomeric milieu. Utilizing bioinformatics tools and online databases, we also provide pathway, subcellular localization, and protein-protein/DNA interaction analyses that support a role for troponin in multiple subcellular compartments. This emerging knowledge challenges the conventional view of troponin as a sarcomere-specific protein exclusively involved in muscle contraction and may transform the way we think about sarcomeric proteins, particularly in the context of human disease and aging.

A review on ZnO-based electrical biosensors for cardiac biomarker detection

Over the past few decades zinc oxide (ZnO)-based thin films and nanostructures have shown unprecedented performance in a wide range of applications. In particular, owing to high isoelectric point, biocompatibility and other multifunctional characteristics, ZnO has extensively been studied as a transduction material for biosensor development. The fascinating properties of ZnO help retain biological activity of the immobilized biomolecule and help in achieving enhanced sensing performance. As a consequence of recent advancements in this multidisciplinary field, diagnostic biosensors are expanding beyond traditional clinical labs to point-of-care and home settings. Label-free electrical detection of biomarkers has been demonstrated using ZnO-sensing platforms. In this review we highlight the characteristics of ZnO that enable realization of its use in development of point-of-care biosensors toward disease diagnosis, in particular cardiovascular diseases.

Pharmacokinetic and pharmacodynamic study of doxorubicin in children with cancer: results of a "European Pediatric Oncology Off-patents Medicines Consortium" trial

Purpose

Doxorubicin is a key component in many pediatric oncology treatment regimens; still pharmacology data on which current dosing regimens are based are very limited.

Methods

We conducted a multinational pharmacokinetic study investigating age dependency of doxorubicin metabolism and elimination in children with cancer. One hundred and one patients treated with doxorubicin according to a cancer-specific national or European therapeutic trial were recruited. Doses of doxorubicin ranged from 10.4 to 57.7 mg/m². Blood samples for measurement of doxorubicin and its metabolite doxorubicinol were collected after two administrations, with five samples collected in children <3 years and eight in children ≥3 years. A population pharmacokinetic approach was used for analysis, including pharmacogenetic covariates. Natriuretic peptides and cardiac troponins were measured to evaluate their role as early indicators of cardiotoxicity.

Results

Age dependence of doxorubicin clearance was demonstrated, with children less than 3 years having a statistically significant lower clearance (21.1 ± 5.8 l/h/m²) than older children (26.6 ± 6.7 l/h/m²) (p = 0.0004) after correcting for body surface area. No effect of the investigated genetic polymorphisms on the pharmacokinetics could be observed. Although natriuretic peptides were transiently elevated after each doxorubicin administration and troponin levels increased with increasing doxorubicin exposure, only limited correlation could be observed between their blood levels and doxorubicin pharmacokinetics.

Conclusion

In the European framework of funding and regulatory support, an add-on study to existing therapeutic trials was developed. The pediatric need concerning missing PK data could be addressed with limited burden for the patients. Empirically used dose adaptations for infants were generally found to be justified based on our PK analyses.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-016-3174-8) contains supplementary material, which is available to authorized users.

Cardiac Troponin I Increase After Successful Percutaneous Coronary Angioplasty: Predictors and Long-Term Prognostic Value

After successful percutaneous coronary interventions (PCI), elevations of cardiac enzymes are not rare, but it is still not clear whether those elevations are associated with adverse late outcome. The purpose of the study was to investigate the relation between cardiac troponin I (cTn-I) increase after successful percutaneous intervention and late outcome. The study consisted of 100 consecutive patients (mean age 56 ±9.8, 84% male) who had successful elective coronary balloon angioplasty with or without stent implantation. Patients with stable angina (n=54) and unstable angina (n=46) were included in the study. Blood samples for measurement of cTn-I were taken before and immediately after the procedure, and every 6 hours for the first 24 hours. Patients with preprocedural cTn-I elevation were excluded from the study. Postprocedural cTn-I elevation was detected in 34 patients (34%, troponin (+) group) and cTn-I levels were normal in 66 patients (66%, troponin (-) group). Logistic regression analysis showed that intervention in patients with unstable angina, stent implantation following balloon dilation, and maximal inflation pressure were the predictors of cTn-I elevation (p=0.035, p=0.038, and p=0.014, respectively). During the prospective follow-up period for 21 ±7.5 months, the incidence of major cardiac events including recurrent angina, acute myocardial infarction, death, and revascularization were not different in patients with and without cTn-I elevation. Overall, major cardiac events occurred in 9 patients (26%) in the troponin (+) group and in 13 patients (20%) in the troponin (-) group. Kaplan-Meier survival analysis showed that cTn-I elevation was not an important correlate of overall cardiac events (log-rank: 1.66, p=0.19). The authors conclude that postprocedural cTn-I elevation is related to unstable angina, stent implantation following predilation, and inflation pressure, and there is no association with minor myocardial injury occurring after successful percutaneous coronary intervention and late adverse cardiac events.

Differential expression of microRNAs in ischemic heart disease

Recent studies provide evidence that ischemic preconditioning (IP) and ischemia/reperfusion (IR) injury lead to altered expression of microRNAs (miRNAs) that affect the survival and recovery of cardiomyocytes. These endogenous ∼22-nucleotide noncoding RNAs negatively regulate gene expression via degradation and translational inhibition of their target mRNAs. miRNAs are involved in differentiation, proliferation, electrical conduction, angiogenesis and apoptosis. These pathways can lead to physiological and pathological adaptations. This review intends to explore several facets of miRNA expression and the underlying mechanisms involved in IR injury, as well as IP as a cardioprotective strategy. In addition, we will investigate miRNA interaction with the renin-angiotensin system and the potential use of miRNAs in developing sensitive biomarkers for cardiovascular disease.

Differential analysis of transient increases of serum cTnI in response to handling in rats

Serum cardiac troponins are the key biomarkers of myocardial necrosis in humans and in preclinical species. The use of ultrasensitive assays for serum cardiac troponin I (cTnI) as a biomarker in safety studies is hampered by interindividual differences. In this study, we investigated the effect of handling procedures on serum cTnI and explored modeling and simulation approaches to mitigate the impact of these interindividual differences. Femoral-catheterized male Crl:WI(Han) rats (n = 16/group) were left undisturbed in their cages with no handling; subjected to 5 min of isoflurane/O₂ anesthesia (A); or placed into a rodent restrainer followed by simulated tail vein injection (RR). Serum cTnI concentrations were assessed over a 24-h period using an ultrasensitive assay, and the study was repeated for confirmation. The mean serum cTnI concentration pre-procedure was 4.2 pg/mL, and remained stable throughout the duration of the study in the rats submitted to the A procedure. Serum cTnI concentrations increased transiently after the RR procedure with a median time to maximum concentration (T_max), of 1 and 2 h and a mean maximum value concentration (C_max), of 53.0 and 7.2 pg/mL in the initial and repeat studies, respectively. A population pharmacodynamic model identified interindividual, procedure- and study-specific effects on serum cTnI concentrations in rats. It is concluded that a modeling and simulation approach more appropriately describes and statistically analyzes the data obtained with this ultrasensitive assays.

Role of imaging for acute chest pain syndromes

Acute chest pain suggestive of ischemic cardiac origin, with a normal or nondiagnostic electrocardiogram and negative initial cardiac markers for myocardial necrosis represent a significant diagnostic dilemma for clinicians. Multiple imaging modalities play a pivotal role in early diagnosis and safe discharge of these patients. In this review, we compare the current imaging modalities available for these patients including their diagnostic accuracy, feasibility, and cost effectiveness. Acute rest myocardial perfusion imaging significantly improves the clinical outcome in these patients and reduces the overall cost when incorporated into the decision making pathway. The choice of imaging modality recommended should be based on local institutional expertise and the overall clinical presentation. The imaging modality with high diagnostic accuracy and negative predictive value will provide for precise risk stratification which is important to clinical decision making, including patients who require admission to the hospital and those who can be safely discharged.

Cardiac biomarkers in acute myocardial infarction

Each year, a large number of patients are seen in the Emergency Department with presentations necessitating investigation for possible acute myocardial infarction. Patients can be stratified by symptoms, risk factors and electrocardiogram results but cardiac biomarkers also have a prime role both diagnostically and prognostically. This review summarizes both the history of cardiac biomarkers as well as currently available (established and novel) assays. Cardiac troponin, our current "gold standard" biomarker criterion for the diagnosis of myocardial infarction has high sensitivity and specificity for this diagnosis and therapies instituted in patients with elevated troponin have been shown to influence outcomes. Other markers of myocardial necrosis, inflammation and neurohormonal activity have also been shown to have either diagnostic or prognostic utility, but none have been shown to be superior to troponin. The measurement of multiple biomarkers and the use of point of care markers may accelerate current diagnostic protocols for the assessment of such patients.

Do induced tachycardias within the scope of electrophysiological studies lead to elevated plasma troponin I levels?

AIMS

Troponin I (TNI) is an established marker for the diagnosis of acute coronary syndrome (ACS). The study evaluated if (induced) tachycardiac arrhyhthmias within the scope of the electrophysiological studies (EPS) led to elevation of TNI serum levels.

METHOD

TNI was measured in the serum of 28 patients before and after the EPS. The left ventricular ejection fraction (LV-EF) was investigated by two-dimensional echocardiography. Left ventricle hypertrophy (LVH) was measured according to the recommendations of the American Society of Echocardiography. All patients underwent coronary angiography prior to the EPS, and significant coronary heart disease was defined as stenosis > 50%. The EPS revealed supraventricular and ventricular tachycardias using the 18-step protocol with one, two, and three extrastimuli.

RESULTS

Indications for the EPS were syncope (n = 15), atrioventricular tachycardia (n = 4), non-sustained VT (n = 6), and sustained VT (n = 3). Coronary heart disease (CHD) was detected in 8 patients (1-vessel: n = 3; 2-vessel: n = 4; 3-vessel: n = 1), and 2 patients underwent percutaneous coronary intervention before EPS. Echocardiography revealed normal LV-EF in 18 patients and a reduction in the others (low n = 3, middle n = 5, high n = 2). Thirteen patients suffered from LVH. In 2 patients, external cardioversion was required during the EPS. TNI was elevated over 0.1 ng/ml (risk stratification cut-off for ACS) in 4 patients before and in 12 patients after EPS. There was no relationship between LV-EF, CHD, and the elevation of TNI after the EPS.

CONCLUSION

TNI can be elevated by (induced) tachycardias within the scope of electrophysiological studies without a relationship to LV-EF, LVH, and CHD.

Right ventricular pressure dynamics and stress echocardiography in pharmacological and exercise stress testing

REASONS FOR PERFORMING STUDY

There is interest in using pharmacological stress testing (PST) as a substitute for exercise stress testing (EST) to evaluate cardiac function in horses.

OBJECTIVES

To compare the effect of PST and EST on right ventricular pressure dynamics and stress echocardiography.

METHODS

Five horses completed a PST and EST in a randomised crossover design. High fidelity pressure transducers were placed in the right ventricle. Continuous pressure signals were digitally collected and stored, and dP/dtmax, dP/dtmin and tau calculated from these measurements. ECGs were recorded continuously for 20 h. Echocardiography was performed prior to EST and PST, during and after PST, and immediately post EST. Plasma cardiac troponin I concentrations were measured pre- and 3-4 h post stress testing. For PST, 5 microg/kg bwt glycopyrrolate i.v. followed after 10 min by 5 microg/kg bwt/min dobutamine infusion over 10 min was given. EST consisted of a 2 min gallop at 110% speed required to elicit VO2max.

RESULTS

Both EST and PST resulted in a significant increase in right-ventricular dP/dtmax and dP/dtmin over baseline (P<0.05) and a significant decrease in tau compared with baseline (P<0.05). EST dP/dtmax and dP/dtmin were significantly greater than PST dP/dtmax and dP/dtmin (P<0.05) and EST tau was significantly less than PST tau (P<0.05). Two minutes post EST and 5 min post PST dP/dtmax were not significantly different, but were significantly less than end-EST and during PST. Tau was also not significantly different between post EST and post PST, but was significantly decreased end-EST compared with during PST. FS were not significantly different between PST and post EST, but during PST and post EST all FS were significantly higher than baseline. Cardiac troponin I concentrations were significantly elevated post PST and were greater than post EST. The clinical relevance of this is unknown.

CONCLUSIONS

PST had a similar, although less marked effect on the cardiac parameters related to right-ventricular pressure dynamics and a similar effect on echocardiography as exercise stress testing.

POTENTIAL RELEVANCE

PST deserves further evaluation in normal horses and those with cardiac disease, and may be complementary to EST to better identify exercise-induced cardiac dysfunction.

Development of a method to measure plasma and whole blood choline by liquid chromatography tandem mass spectrometry

Background

Current gold standard markers for myocardial damage are troponins I and T, which are both sensitive and specific for the detection of myocardial infarction, but require up to 6 h to become reliably elevated in serum. Investigation into markers with potential to identify patients with early ischaemic changes is therefore intense. Choline is reported to be prognostic in patients presenting with acute coronary syndromes via its release from ischaemic cell membranes.

Methods

Liquid chromatography tandem mass spectrometry was used to develop a method to quantitate choline in plasma and blood. The method involves addition of a deuterated internal standard to an aliquot of plasma or blood followed by organic solvent addition, which precipitates the proteins in the sample. Preparation was carried out directly into a 96-deep-well plate. Chromatography of choline used a strong cation exchange column and separation used a Waters Atlantis dC18 analytical column positioned directly before the mass spectrometer source, allowing on-line preanalytical clean up of the sample.

Results

The lower limit of quantitation was 0.38 μmol/L, linearity was observed up to 754 μmol/L, with a working concentration range of 0.38–224 μmol/L, inter- and intra-assay coefficients of variation were <6% and <4%, respectively. Samples were stable throughout five freeze–thaw cycles and recovery was between 94% and 114%.

Conclusions

The assay was successfully validated in accordance with FDA guidelines and is suitable for quantitation of choline in research and clinical settings.

Qualification of cardiac troponin I concentration in mouse serum using isoproterenol and implementation in pharmacology studies to accelerate drug development

Cardiac troponin I is a useful biomarker of myocardial injury, but its use in mice and application to early drug discovery are not well described. The authors investigated the relationship between cTnI concentration in serum and histologic lesions in heart tissue from mice treated with isoproterenol (ISO). Cardiac TnI concentrations in serum increased in a dose-dependant manner and remained increased twenty-four to forty-eight hours after a single administration of isoproterenol. Increased cTnI concentration was of greater magnitude and longer duration than increased fatty acid binding protein 3 concentration, aspartate aminotransferase activity, and creatine kinase activity in serum. Isoproterenol-induced increases in cTnI concentrations were both greater and more sustained in BALB/c than in CD1 mice and correlated with incidence and severity of lesions observed in heart sections from both strains. In drug development studies in BALB/c mice with novel kinase inhibitors, cTnI concentration was a reliable stand-alone biomarker of cardiac injury and was used in combination with measurements of in vivo target inhibition to demonstrate an off-target contribution to cardiotoxicity. Additional attributes, including low cost and rapid turnaround time, made cTnI concentration in serum invaluable for detecting cardiotoxicity, exploring structure-activity relationships, and prioritizing development of compounds with improved safety profiles early in drug discovery.

Present and Future Biochemical Markers for Detection of Acute Coronary Syndrome

The use of biochemical markers in the diagnosis and management of patients with acute coronary syndrome has increased continually in recent decades. The development of highly sensitive and cardiac-specific troponin assays has changed the view on diagnosis of myocardial infarction and also extended the role of biochemical markers of necrosis into risk stratification and guidance for treatment. The consensus definition of myocardial infarction places increased emphasis on cardiac marker testing, with cardiac troponin replacing creatine kinase MB as the "gold standard" for diagnosis of myocardial infarction. Along with advances in the use of more cardiac-specific markers of myocardial necrosis, biochemical markers that are involved in the progression of atherosclerotic plaques to the vulnerable state or that signal the presence of vulnerable plaques have recently been identified. These markers have variable abilities to predict the risk of an individual for acute coronary syndrome. The aim of this review is to provide an overview of the well-established markers of myocardial necrosis, with a special focus on cardiac troponin I, together with a summary of some of the potential future markers of inflammation, plaque instability, and ischemia.

Troponin ratio and risk stratification in subjects with acute coronary syndrome undergoing percutaneous coronary intervention

BACKGROUND

Cardiac enzyme release after percutaneous coronary intervention (PCI) seems to play a role in risk stratification. After PCI, CK-MB plasmatic concentrations three times above the upper level of normal (ULN) are currently the most used risk stratification parameters. We sought to assess whether peak cardiac troponin I (cTn-I) concentration/base concentration ratio (PBTR) may act as a predictor of major adverse cardiac events (MACEs) after PCI, regardless of cTn-I ULN.

METHODS

We evaluated 326 consecutive patients with acute coronary syndrome (ACS) who underwent PCI. Baseline and post-PCI cTn-I values were evaluated over serial blood samples every 6h for at least 72h. Patients were further divided into four groups according to their PBTR values (<1, 1-4, 4-10, >10). MACEs were recorded over a 6-month follow-up period. Patients with primary PCI or unsuccessful PCI were excluded from the study.

RESULTS

Higher values of PBTR significantly correlated with a worse prognosis at 6 months (<1, 16.30% of MACEs; 1-4, 19.42%; 4-10, 24.39%; >10, 35.63%; p<0.05), both in Q-wave myocardial infarction (MI) and unstable angina (UA) subgroups. The correlation remained statistically significant, even considering subjects with peak cTn-I less than three times the ULN (p < 0.05) and after correction for age, gender, risk factors, diagnosis (MI versus UA), and peak cTn-I levels in a multiple Cox' regression analysis (HR 1.62, p<0.05).

CONCLUSIONS

PBTR is an independent predictor of MACEs after PCI in a 6-month follow-up period. This risk stratification tool may be useful to predict adverse events in PCI patients, even in the case of apparently non-elevated peak cTn-I concentrations.

Nicorandil suppressed myocardial injury after percutaneous coronary intervention

BACKGROUND

Nicorandil exerts beneficial effects as an adjunctive therapy for patients with ischemic heart disease. This study was designed to assess the effects of nicorandil on the myocardial protective benefits of elective percutaneous coronary intervention (PCI).

METHODS

We randomly divided 49 patients scheduled to undergo elective PCI into two groups, nicorandil and control. Before PCI, the former received an intravenous bolus injection of nicorandil (4 mg), followed by continuous infusion at 6 mg/h for 24 h after intervention. Oral administration of nicorandil was continued until follow-up coronary angiography (CAG). Serial venous blood samples, for measurement of creatine kinase (CK), creatine kinase MB isoform (CK-MB), troponin I (TnI) and myoglobin, were obtained before PCI, and at 0 h, 4 h, 24 h and 48 h after PCI. Left ventricular function and left ventricular wall motion were evaluated by means of contrast ventriculography before PCI and follow-up CAG.

RESULTS

At 24 h after PCI, elevations of cardiac enzymes were significantly suppressed in the nicorandil as compared to the control group; CK (78.1+/-34.9 versus 117.4+/-137.9 U/l, P=0.0141), CK-MB (1.57+/-1.90 versus 2.67+/-4.50 U/l, P=0.0485) and TnI (0.37+/-0.55 versus 0.86+/-1.65 ng/ml, P=0.0101). Regional left ventricular wall motion was significantly improved at follow-up in the nicorandil as compared to the control group.

CONCLUSIONS

Nicorandil suppressed elevations of cardiac enzymes after elective PCI and left ventricular wall motion was also significantly improved at follow-up, suggesting that nicorandil enhances the myocardial protective effect of PCI against angioplasty-related myocardial injury.

In vitro and in vivo examination of cardiac troponins as biochemical markers of drug-induced cardiotoxicity

Cardiac troponin T (cTnT) and troponin I (cTnI) are becoming acknowledged as useful biochemical markers of drug-induced cardiotoxicity. In this study we examined the release kinetics of cTnT and cTnI using an in vitro model of isolated rat neonatal ventricular cardiomyocytes (NVCM, 72h treatment with 0.1-3microM of daunorubicin) and compared it with data from a rabbit model of chronic anthracycline-induced cardiomyopathy in vivo (3mg/kg of daunorubicin weekly, 10 weeks). In cell-culture media, the cTnI and cTnT concentrations were concentration- and time-dependently increasing in response to daunorubicin exposure and were negatively exponentially related to cardiomyocyte viability. With 3microM daunorubicin, the relative increase of AUC of cTnT and cTnI was 2.4- and 5.3-fold higher than the increase of LDH activity, respectively. In rabbits, the daunorubicin-induced cardiomyopathy was associated with progressive increase of both cTnT and cTnI. Although the correlation between cTnT and cTnI cumulative release (AUCs) was found (R=0.81; P<0.01) and both cardiac troponins corresponded well with the echocardiographically-assessed systolic dysfunction (R=0.83 and 0.81 for cTnT and cTnI, respectively; P<0.001), the first significant increase in cTnI levels was observed earlier (at a cumulative daunorubicin dose of 200mg/m(2)) than with cTnT (350mg/m(2)). In conclusion, our study has confirmed cTnT and cTnI as very sensitive and specific markers of anthracycline-induced cardiotoxicity. The troponins can become not only the bridge between the clinical and experimental studies of drug-induced cardiotoxicity but also the linkage between the preclinical experiments in vitro and in vivo.

Tissue-specific interactions of TNI isoforms with other TN subunits and tropomyosins in C. elegans: the role of the C- and N-terminal extensions

The aim of this study is to investigate the function of the C-terminal extension of three troponin I isoforms, that are unique to the body wall muscles of Caenorhabditis elegans and to understand the molecular interactions within the TN complex between troponin I with troponin C/T, and tropomyosin. We constructed several expression vectors to generate recombinant proteins of three body wall and one pharyngeal troponin I isoforms in Escherichia coli. Protein overlay assays and Western blot analyses were performed using antibodies. We demonstrated that pharyngeal TNI-4 interacted with only the pharyngeal isoforms of troponin C/T and tropomyosin. In contrast, the body wall TNI-2 bound both the body wall and pharyngeal isoforms of these components. Similar to other invertebrates, the N-terminus of troponin I contributes to interactions with troponin C. Full-length troponin I was essential for interactions with tropomyosin isoforms. Deletion of the C-terminal extension had no direct effect on the binding of the body wall troponin I to other muscle thin filament troponin C/T and tropomyosin isoforms.

Acute effects of short duration, maximal exercise on cardiac troponin I in healthy horses

This study evaluated the effects of exercise on cardiac troponin I (cTnI) concentrations in healthy, adult horses.

Fifteen fit, healthy horses determined to have a normal cardiovascular system completed a standardized exercise test on a high-speed treadmill. Heparinized blood was collected for plasma cTnI concentrations before maximal exercise, and 1, 3, 6, 9, 12 and 24 h post-exercise. The cTnI concentrations were measured with a commercial system (Stratus CS, Dade Behring, Inc.). Results were analysed by a multivariate ANOVA, where indicatedpost hocanalysis was done by Tukey–Kramer HSD and significance was placed atp < 0.05.

All horses had elevations in cTnI concentrations after maximal exercise. Values for cTnI trended higher at 3 h (0.066 ± 0.011 ng ml− 1) and 6 h (0.062 ± 0.011 ng ml− 1) post-exercise compared with pre-exercise (0.039 ± 0.007 ng ml− 1), although this did not reach statistical significance. Mean cTnI concentrations were within our normal reference range at all time points, although four individuals were above our normal range after exercise.

These data show that short-term, high-intensity exercise induces a small rise in plasma cTnI in normal horses. This should be kept in mind when evaluating cTnI concentrations in horses that have recently completed intense exercise. In addition, these data suggest that 3–6 h after intense exercise may be the optimal time for measurement of cTnI concentrations in horses with suspected exercise-induced myocardial damage.

Troponin as a marker of myocardiac damage in drug-induced cardiotoxicity

Cardiac troponins T and I (cTnT and cTnI) are becoming the serum biomarkers of choice for monitoring potential drug-induced myocardial injury in both clinical and preclinical studies. The utility of cardiac troponins has been mainly demonstrated following the administration of antineoplastic drugs and beta-sympathomimetics, although the routine use of these markers in the monitoring in patients who received anthracyclines therapy is far from settled. Unlike the previous markers, which suffered from numerous shortages, the main advantages of cardiac troponins are their high specificity and sensitivity, wide diagnostic window and the possibility to use commercially available assays in clinical settings as well as in a broad range of laboratory animals. Nevertheless, in spite of vigorous research in this area, a number of questions are still unanswered and these are discussed in this review. The main problems seem to be the lack of standardisation of variety of troponin immunoassays, the assessment of suitable cutoff for drug-induced cardiotoxicity and determination of critical diagnostic window related to the optimal timing of sample collection, which may be drug-dependent.

[Muscle cell proteins are selectively released into the blood stream by marathon running]

In 19 marathon runners of both sexes, plasma concentrations of total creatine kinase (CK) activity, CKMB mass, myoglobin and troponin I were determined before and immediately after the race. Total CK activity and myoglobin increased significantly in all runners and showed neither a correlation with the individual age of the runners nor with the time they needed to reach the goal. In 12 of the runners, CKMB mass increased during the race to a level suggesting myocardial necrosis. However, the runners did not show any detectable deterioration of cardiac function after the race. The appearance of considerable amounts of muscle proteins in plasma precipitated by the muscle strain during the race seems explained by damage of skeletal muscle detected by histological studies. These phenomena may also be a consequence of profoundly disturbed cellular permeability, perhaps due to a kind of local stunning of muscle tissue by prolonged muscular strain.

Cardiac troponin I in pastured and race-training Thoroughbred horses

Cardiac troponin I (cTnI), a myocardial polypeptide, is a highly sensitive and specific biomarker of myocardial injury in people and dogs. The structure of cTnI is highly conserved across species, and equine myocardium has high reactivity with human immunoassays. The purpose of this study was to describe cTnI concentrations in normal pastured and race-training Thoroughbred horses. Ten horses on pasture and 10 horses in race training were studied. Horses were considered normal on the basis of physical examination, training performance, electrocardiography (ECG), and echocardiography. Serum cTnI concentrations were determined with a colorimetric immunoassay. The assay has an analytical sensitivity of 0.04 ng/mL. Serum cTnI concentrations in race-training horses were not significantly different from those of pastured horses. When groups were combined, mean cTnI concentration (+/- SD) was 0.047 +/- 0.085 ng/mL. and the median was 0 (range, 0-0.35 ng/mL). The 90th percentile for both groups combined was 0.11 ng/mL. This study establishes a preliminary reference range for serum cTnI in normal Thoroughbred horses.

Cardiac troponin I: its contribution to the diagnosis of perioperative myocardial infarction and various complications of cardiac surgery

OBJECTIVE

To study the value of assaying cardiac troponin I (cTnI) for the early diagnosis of perioperative myocardial infarction (PMI) and various complications of cardiac surgery.

DESIGN

A prospective observational clinical study.

SETTING

Biochemical laboratory, anesthesia, and cardiac surgery department of Hôpital Broussais.

PATIENTS

Two hundred and sixty consecutive patients undergoing cardiac surgery.

INTERVENTIONS

All patients underwent coronary artery bypass grafting and/or valvular surgery under extracorporeal circulation. Per-operative and postoperative follow-up consisted of electrocardiogram, echocardiography (mainly by the transesophageal approach), and serial determinations of biochemical markers such as creatinine kinase-MB isoenzyme (CK-MB) and cTnI. PMI, new ST segment changes, and ventricular arrhythmias were considered postoperative adverse cardiac outcome.

MEASUREMENTS AND MAIN RESULTS

CTnI was measured before cardiopulmonary bypass (T0) and 12 and 24 hrs after (T12, T24). CK-MB was measured on arrival in the intensive care unit and on the first postoperative day (D1). Patients were divided into three groups according to the type of surgery: coronary artery bypass graft (CABG), valvular surgery (VS), or both procedures. The plasma CK-MB and cTnI concentrations were high in all patients after extracorporeal circulation because of aortic clamping or cardioplegia. The CK-MB and cTnI values were higher in the VS group than in the CABG group. Values peaked at T12 and fell by T24, except when PMI occurred. Eight patients developed a PMI. Patients with PMI had significantly higher cTnI levels at T12 and T24, and higher CK-MB values at D1 than patients without PMI. Cutoff values of cTnI for diagnosing PMI were >19 microg/L at T12 with 100% sensitivity and 73% specificity, and >36 microg/L at T24, with 100% sensitivity and 93% specificity. Lower cTnI values were highly suggestive of the absence of PMI after CABG and/or VS. Other complications such as ST segment changes, ventricular arrhythmias and cardiac failure were indicated by high cTnI levels at T12 and T24. Myocardial protective measures were associated with a nonsignificant increase in cTnI values.

CONCLUSIONS

CTnI is more sensitive and specific than CK-MB for diagnosing PMI and other forms of heart failure after cardiac surgery.

Measurement of cardiac troponins

The cardiac troponins form part of the regulatory mechanism for muscle contraction. Specific cardiac isoforms of cardiac troponin T and cardiac troponin I exist and commercially available immunoassay systems have been developed for their measurement. A large number of clinical and analytical studies have been performed and the measurement of cardiac troponins is now considered the 'gold standard' biochemical test for diagnosis of myocardial damage. There have been advances in understanding the development and structure of troponins and their degradation following myocardial cell necrosis. This has contributed to the understanding of the problems with current assays. Greater clinical use has also highlighted areas of analytical and clinical confusion. The assays are reviewed based on manufacturers' information, current published material as well as the authors' in-house experience.

Myocardial injury and systemic fibrinolysis in patients undergoing repair of ruptured abdominal aortic aneurysm: a preliminary report

BACKGROUND

ruptured abdominal aortic aneurysm (AAA) is associated with inhibition of systemic fibrinolysis. Hypofibrinolysis is a risk factor for ischaemic myocardial injury, one of the commonest complications of ruptured AAA repair. Cardiac troponin I (cTnI) is one of the most sensitive and specific marker of myocardial injury currently available.

OBJECTIVE

To examine, for the first time, the relationship between fibrinolytic activity and myocardial injury in patients operated for ruptured AAA.

METHODS

Twenty patients (18 men and 2 women of median age 74, range 65-86 years) undergoing repair of ruptured AAA were prospectively studied. Plasma tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI-1) activity were measured pre-operatively, immediately before and five minutes following aortic clamp release. Serum cTnI was measured pre-operatively, 6 and 24 h following clamp release. Results cTnI was detectable at one or more sample points in 13 (65%) patients, and in 7 out of 8 patients who suffered major cardiac complications. There was a significant negative correlation between pre-operative t-PA activity and cTnI before operation (r =-0.55, p = 0.01) and 6 h ( r =-0.51, p =0.02) after clamp release. There was a significant positive correlation between pre-operative PAI activity and cTnI before operation (r =+0.50, p =0.03), 6 h ( r =+0.47, p =0.04) and 24 h ( r =+0.50, p =0.03) after clamp release. There was no correlation between pre- and intra-operative hypotension or blood transfusion requirement and cTnI release.

CONCLUSIONS

Hypofibrinolysis during ruptured AAA repair is associated with the development of peri-operative myocardial injury. The causal mechanisms underlying this state are not clear but treatment of this prothrombotic/hypofibrinolytic diathesis may help to limit myocardial cell necrosis.

Accuracy of biomarkers to diagnose acute cardiac ischemia in the emergency department: a meta-analysis

STUDY OBJECTIVE

We sought to evaluate quantitatively the evidence on the diagnostic performance of presentation and serial biochemical markers for emergency department diagnosis of acute cardiac ischemia (ACI), including acute myocardial infarction (AMI) and unstable angina.

METHODS

We conducted a systematic review and meta-analysis of the English-language literature published between 1966 and December 1998. We examined the diagnostic performance of creatine kinase, creatine kinase-MB, myoglobin, and troponin I and T testing. Diagnostic performance was assessed by using estimates of test sensitivity and specificity and was summarized by summary receiver-operating characteristic curves.

RESULTS

Only 4 studies were found that evaluated all patients with ACI; 73 were found that focused only on a diagnosis of AMI. To diagnose ACI, presentation biomarker tests had sensitivities of 16% to 19% and specificities of 96% to 100%; serial biomarker tests had sensitivities of 31% to 45% and specificities of 95% to 98%. Considering only the diagnosis of AMI, presentation biomarker tests had summary sensitivities of 37% to 49% and summary specificities of 87% to 97%; serial biomarker tests had summary sensitivities of 79% to 93% and summary specificities of 85% to 96%. Variation of test sensitivity was best explained by test timing. Longer symptom duration or time between serial tests yielded higher sensitivity.

CONCLUSION

The limited evidence available to evaluate the diagnostic accuracy of biomarkers for ACI suggests that biomarkers have very low sensitivity to diagnose ACI. Thus, biomarkers alone will greatly underdiagnose ACI and will be inadequate to make triage decisions. For AMI diagnosis alone, multiple testing of individual biomarkers over time substantially improves sensitivity, while retaining high specificity, at the expense of additional time. Further high-quality studies are needed on the clinical effect of using biomarkers for patients with ACI in the ED and on optimal timing of serial testing and in combination with other tests.

Clinical and Experimental Results on Cardiac Troponin Expression in Duchenne Muscular Dystrophy

Background: Because of controversial earlier studies, the purpose of this study was to provide novel experimental and additional clinical data regarding the possible reexpression of cardiac troponin T (cTnT) in regenerating skeletal muscle in Duchenne muscular dystrophy (DMD).

Methods: Plasma from 14 patients (mean age, 7.5 years; range, 5.7–19.4 years) with DMD was investigated for creatine kinase (CK), the CK MB isoenzyme (CKMB), cTnT and cardiac troponin I (cTnI), and myoglobin. cTnT concentrations were measured by an ELISA (second-generation assay; Roche) using the ES 300 Analyzer. cTnI, myoglobin, and CKMB were measured by an ELISA using the ACCESS System (Beckman Diagnostics). Troponin isoform expression was studied by Western blot analysis in remnants of skeletal muscle biopsies of three patients with DMD and in an animal model of DMD (mdx mice; n = 6).

Results: There was no relation of cTnT and cTnI to clinical evidence for cardiac failure. cTnI concentrations remained below the upper reference limit in all patients. cTnT was increased (median, 0.11 μg/L; range, 0.06–0.16 μg/L) in 50% of patients. The only significant correlation was found for CK (median, 3938 U/L; range, 2763–5030 U/L) with age (median, 7.5 years; range, 6.8–10.9 years; r = −0.762; P = 0.042). Western blot analysis of human or mouse homogenized muscle specimens showed no evidence for cardiac TnT and cTnI expression, despite strong signals for skeletal muscle troponin isoforms.

Conclusions: We found no evidence for cTnT reexpression in human early-stage DMD and in mdx mouse skeletal muscle biopsies. Discrepancies of cTnT and cTnI in plasma samples of DMD patients were found, but neither cTnT nor cTnI plasma concentrations were related with other clinical evidence for cardiac involvement.

Clinically significant blunt cardiac trauma: role of serum troponin levels combined with electrocardiographic findings

BACKGROUND

The true importance of blunt cardiac trauma (BCT) is related to the cardiac complications arising from it. Diagnostic tests that can predict accurately if such complications will develop or not may allow early and aggressive monitoring or early discharge. We investigated the role of two simple and convenient tests, serum cardiac troponin I (cTnI) and electrocardiogram (ECG), when used to identify patients at risk of cardiac complications after BCT.

METHODS

Over a 10-month period, 115 patients with evidence of significant blunt thoracic trauma were prospectively followed to identify the presence of clinically significant BCT (Sig-BCT), defined as cardiogenic shock, arrhythmias requiring treatment, or structural cardiac abnormalities directly related to the cardiac trauma. An ECG was obtained at admission and at 8 hours. Cardiac troponin I was measured at admission, at 4 hours, and at 8 hours. Transthoracic echocardiography was performed when clinically indicated. The sensitivity, specificity, and positive and negative predictive values of ECG and cTnI to identify Sig-BCT were calculated. Clinical risk factors for Sig-BCT were examined by univariate and multivariate analysis.

RESULTS

Nineteen patients (16.5%) were diagnosed with Sig-BCT and, in 18 of them, symptoms presented within 24 hours of admission. Abnormal electrocardiographic findings were detected in 58 patients (50%) and elevated cTnI levels in 27 (23.5%). Electrocardiography and cTnI had positive predictive values of 28% and 48% and negative predictive values of 95% and 93%, respectively. However, when both tests were abnormal (positive) or normal (negative), the positive and negative predictive values increased to 62% and 100%, respectively. Other independent risk factors for Sig-BCT were head injury, spinal injury, history of preexisting cardiac disease, and a chest Abbreviated Injury Score greater than 2.

CONCLUSION

The combination of ECG and cTnI identifies reliably the presence or absence of Sig-BCT. Patients with an abnormal ECG and cTnI need close monitoring for at least 24 hours. Patients with a normal admission ECG and cTnI can be safely discharged in the absence of other injuries.

Cardiac troponin I predicts myocardial dysfunction in aneurysmal subarachnoid hemorrhage

OBJECTIVES

We studied the incidence of myocardial injury in aneurysmal subarachnoid hemorrhage (SAH) using the more sensitive cardiac troponin I (cTnI) assay, correlated changes in cTnI with creatine kinase, MB fraction (CK-MB), myoglobin, and catecholamine metabolite assays, and examined the predictive value of changes in cTnI for myocardial dysfunction.

BACKGROUND

Myocardial injury in aneurysmal SAH as evidenced by elevated CK-MB fraction has been reported. Little published data exist on the value of cTnI measurements in aneurysmal SAH.

METHODS

Thirty-nine patients were studied for seven days. Clinical cardiovascular assessment, electrocardiographic (ECG), echocardiography, cTnI, CK, CK-MB and CK-MB index, myoglobin and 24-h urinary catecholamine assays were performed in all patients. The ECG abnormalities were defined by the presence of ST-T changes, prolonged QT intervals, and arrhythmias. An abnormal echocardiogram was defined by the presence of wall-motion abnormalities and a reduced ejection fraction. The severity of SAH was graded clinically and radiologically.

RESULTS

Eight patients demonstrated elevations in cTnI (upper limit of normal is 0.1 microg/liter with the immunoenzymatic assay and 0.4 microg/liter with the sandwich immunoassay), while five had abnormal CK-MB levels (upper limit of normal is 8 microg/liter). Patients with more severe grades of SAH were more likely to develop a cTnI leak (p < 0.05). Patients with cTnI elevations were more likely to demonstrate ECG abnormalities (p < 0.01) and manifest clinical myocardial dysfunction (p < 0.01) as evidenced by the presence of a gallop rhythm on auscultation and clinical or radiological evidence of pulmonary edema as compared to those with CK-MB elevations. The sensitivity and specificity of cTnI to predict myocardial dysfunction were 100% and 91%, respectively, whereas the corresponding figures for CK-MB were 60% and 94%, respectively. Elevations in myoglobin levels (upper limit of normal <70 microg/liter) and urinary catecholamine metabolites (urinary vanilmandelate/creatinine ratio upper limit of normal, 2.6) are a nonspecific finding.

CONCLUSIONS

Measurements of cTnI reveal a higher incidence of myocardial injury than predicted by CK-MB in aneurysmal SAH, and elevations of cTnI are associated with a higher incidence of myocardial dysfunction. Thus, cTnI is a highly sensitive and specific indicator of myocardial dysfunction in aneurysmal SAH.

Comparison of the diagnostic value of cardiac troponin I and T determinations for detecting early myocardial damage and the relationship with histological findings after isoprenaline-induced cardiac injury in rats

Cardiac troponins I (cTnI) and T (cTnT) have been shown to be highly sensitive and specific markers of myocardial cell injury. The purpose of this study was to investigate the diagnostic value of cTnI and cTnT with regard to creatine kinase (CK) and lactate dehydrogenase (LD) and to determine whether they can be used for early diagnosis of myocardial damage in rats, and to examine the relationship between cTnl and cTnT release with histological examinations, using isoprenaline-induced cardiac muscle damage as an experimental model in the rat. Eighteen Wistar rats per group were treated with a single dose of either isoprenaline (iso) or with normal saline as a control group. The anti-cTnI and cTnT monoclonal antibodies (mAbs) employed in the cTnI (Access) and cTnT (Elecsys) assays cross-react with cTnI and cTnT of the rat. A highly significant rise of cTnl or cTnT was found already 2 h after iso. The time-courses of cTnI and cTnT were monophasic in form. The highest cTnI (mean+/-S.D., 1.1+/-2.3 ng/ml) and cTnT (mean+/-S.D. 3.6+/-30 ng/ml) were found 4 h after iso. cTnI and cTnT significantly increased in iso-treated rats in comparison with controls whether the differences between 2-, 4- and 6-h levels and basal levels were considered or not. The areas under cTnl and cTnT curves (AUC) (0-6 h) and the maximal cTnI and cTnT (0-6 h) after iso were significantly different from the controls. For CK and LD, no elevation in comparison with controls could be detected (except a trend for LD whether or not the difference between 6-h levels and basal levels were considered (P=0.08) and for LD AUC (0-6 h) (P=0. 059)). Correlations between maximal cTnI and cTnT and AUC were 0.69 (P=0.0001) and 0.60 (P=0.0066), respectively. Histological examinations of iso-treated rats revealed acute focal or multifocal myofibrillar degeneration of the myocardial tissue in ten out of 14 rats and showed the earliest alterations 4 h after iso in one treated rat. Only four of the controls exhibited evidence of mild changes and slight mononuclear cell infiltration. cTnl and cTnT peak values to at least 0.35 and 1.3 ng/ml, respectively, were necessary to detect histological myocardial cell injury after iso. cTnI and cTnT were found to be early markers for diagnosing iso-induced myocardial damage in comparison with CK and LD. Elevations of cTnI and cTnT appeared to relate to the severity of histologic changes after myocardial injury. Although there was a difference in the absolute concentration of results between cTnI and cTnT assays, due to a lack of standardization and heterogeneity in the cross-reactivities of mAbs to various troponin I and T forms, cTnI and cTnT can be used as easily measurable target parameters for detection of cardiotoxic and/or cardiodegenerative effects in rats.

The role of cardiac troponin I in determining the necessity for exercise electrocardiography in low risk patients with chest pain

BACKGROUND

Assessment of non-cardiac chest pain places a considerable burden on healthcare resources. The current practice of serial electrocardiographs (ECGs), serum creatinine phosphokinase and by pre-discharge exercise electrocardiography gives an average in-hospital stay of 3.7 days.

AIMS

This study assess the use of a sensitive assay for cardiac troponin I (cTnI) to identify a low risk group for whom exercise ECG may not be indicated.

METHOD

Ninety-five patients with acute chest pain and with peak cTnI < 0.1 ng/ml and a non-diagnostic resting ECG were studied. Patients were divided into two groups. Group one had normal range cTnI (< 0.03 ng/ml). Group two had minimal elevation of cTnI (0.03-0.099 ng/ml). Average follow-up was 172 days.

RESULTS

Nineteen patients had minimal elevation in cTnI of whom five developed significant ST shift on exercise and five had adverse events. No patient with a normal range cTnI had a positive stress test and none suffered an adverse event (p < 0.001).

CONCLUSION

CTnI in the normal range can identify patients with acute chest pain who have a negligible event rate and for whom exercise electrocardiography is not required.

Use of a dual monoclonal solid phase and a polyclonal detector to create an immunoassay for the detection of human cardiac troponin I

OBJECTIVES

We report the development of a fully automated, random access, chemiluminescent immunoassay, for the detection of human cardiac Troponin I (cTnI) in serum and plasma for use on the ACS:180(R) System.

DESIGN AND METHODS

This assay format uses a combination of two monoclonal antibodies covalently coupled to paramagnetic (PMP) particles as a solid phase and an affinity purified polyclonal antibody, specific to the N-terminal domain of cTnI (peptide-3 region) labeled with a chemiluminescent compound as the detector antibody. The assay offers excellent low-end sensitivity and precision.

RESULTS

No interferences are observed from by blood components such as HAMA and drugs used in cardiac therapy. Patient samples tested on the ACS:180 cTnI assay showed good correlation with the Stratus cTnI assay (ACS: cTnI = 1. 02*Stratus + 0.05 g/L, r = 0.96, n = 1170).

CONCLUSION

Paired with the other ACS:180 cardiac assays, myoglobin and CKMBII, the ACS:180 system now offers an excellent panel of cardiac assay for use in rapid and accurate diagnosis of a myocardial event.