Comparative analysis of cardiac troponin I and creatine kinase-MB as markers of acute myocardial infarction

Comprehensive bioinformatics analytics and in vivo validation reveal SLC31A1 as an emerging diagnostic biomarker for acute myocardial infarction

BACKGROUND

Globally, Acute Myocardial Infarction (AMI) is a common cause of heart failure (HF), which has been a leading cause of mortality resulting from non-communicable diseases. On the other hand, increasing evidence suggests that the role of energy production within the mitochondria strongly links to the development and progression of heart diseases, while Cuproptosis, a newly identified cell death mechanism, has not yet been comprehensively analyzed from the aspect of cardiovascular medicine.

MATERIALS AND METHODS

8 transcriptome profiles curated from the GEO database were integrated, from which a diagnostic model based on the Stacking algorithm was established. The efficacy of the model was evaluated in a multifaced manner (i.e., by Precision-Recall curve, Receiver Operative Characteristic curve, etc.). We also sequenced our animal models at the bulk RNA level and conducted qPCR and immunohistochemical staining, with which we further validated the expression of the key contributor gene to the model. Finally, we explored the immune implications of the key contributor gene.

RESULTS

A merged machine learning model containing 4 Cuproptosis-related genes (i.e., PDHB, CDKN2A, GLS, and SLC31A1) for robust AMI diagnosis was developed, in which SLC31A1 served as the key contributor. Through in vivo modeling, we validated the aberrant overexpression of SLC31A1 in AMI. Besides, further transcriptome analysis revealed that its high expression was correlated with significant potential immunological implications in the infiltration of many immune cell types, especially monocyte.

CONCLUSIONS

We constructed an AMI diagnostic model based on Cuproptosis-related genes and validated the key contributor gene in animal modeling. We also analyzed the effects on the immune system for its overexpression in AMI.

Effects of Melatonin on Cardiac Injury and Inflammatory Biomarkers in Patients Undergoing Coronary Artery Bypass Graft Surgery: a Meta-analysis

INTRODUCTION

The antiinflammatory and antioxidative effects of melatonin have been established in recent years. Several studies indicate that oxidative stress and inflammation are key drivers of post-coronary artery bypass graft (CABG) surgery complications. In the present study, we aimed to investigate the effects of melatonin on cardiac injury and inflammatory biomarkers in CABG candidates.

METHODS

Embase, Medline/PubMed, Web of Science, Scopus, and the Cochrane library were searched up to 5 June 2022. All randomized controlled trials examining cardiac injury and inflammatory biomarkers of CABG patients who received melatonin were included. The random-effects model was utilized to perform the analysis.

RESULTS

A total of 947 citations were retrieved through database searches. Finally, five articles (six trials with 342 patients) were included after the screening. Melatonin supplementation led to a significant reduction in cardiac troponin I (CTnI) [weighted mean difference(WMD): -2.28 ng/ml; 95% CI -2.87, -1.69; P < 0.01; I²: 91.25%] and high sensitivity-C reactive protein (hs-CRP) levels (WMD: -0.62 mg/L; 95% CI -0.73, -0.5; P < 0.01; I²: 99.98%) in patients undergoing CABG surgery. We found a nonsignificant decrease in creatine kinase isoenzyme muscle/brain (CK-MB) levels (WMD: -2.87 ng/ml; 95% CI -5.97, 0.23; P = 0.07; I²: 99.98%) after melatonin supplementation. No publication bias was found according to Egger's test.

CONCLUSION

Melatonin supplementation may be useful in reducing cardiac injury and inflammatory biomarkers in CABG candidates. Future studies should investigate the clinical significance of these findings.

Circular RNAs: Biogenesis, Biological Functions, and Roles in Myocardial Infarction

Non-coding RNAs have been excavated as important cardiac function modulators and linked to heart diseases. Significant advances have been obtained in illuminating the effects of microRNAs and long non-coding RNAs. Nevertheless, the characteristics of circular RNAs are rarely mined. Circular RNAs (circRNAs) are widely believed to participate in cardiac pathologic processes, especially in myocardial infarction. In this review, we round up the biogenesis of circRNAs, briefly describe their biological functions, and summarize the latest literature on multifarious circRNAs related to new therapies and biomarkers for myocardial infarction.

Microfluidics for diagnosis and treatment of cardiovascular disease

Cardiovascular disease (CVD), a type of circulatory system disease related to the lesions of the cardiovascular system, has become one of the main diseases that endanger human health. Currently, the clinical diagnosis of most CVDs relies on a combination of imaging technology and blood biochemical test. However, the existing technologies for diagnosis of CVDs still have limitations in terms of specificity, detection range, and cost. In order to break through the current bottleneck, microfluidic with the advantages of low cost, simple instruments and easy integration, has been developed to play an important role in the early prevention, diagnosis and treatment of CVDs. Here, we have reviewed the recent various applications of microfluidic in the clinical diagnosis and treatment of CVDs, including microfluidic devices for detecting CVD markers, the cardiovascular models based on microfluidic, and the microfluidic used for CVDs drug screening and delivery. In addition, we have briefly looked forward to the prospects and challenges of microfluidics in diagnosis and treatment of CVDs.

Protective effect of glycyrrhizin on coronary microembolization-induced myocardial dysfunction in rats

Coronary microembolization (CME)-induced inflammation and cardiomyocyte apoptosis are two key factors contributing to CME-induced myocardial dysfunction. High-mobility group box-1 (HMGB1) plays essential role in progression of CME-induced injury and inhibition of HMGB1 has been shown to be protective. In present study, the potential effects of glycyrrhizin, a HMGB1 inhibitor, on CME-induced myocardial dysfunction are evaluated. Using a rat model of CME, we administrated glycyrrhizin in rats prior to CME induction. The level of HMGB1, TNF-α, iNOS, IL-6, IL-1β, cleaved caspase-3, Bax, and Bcl-2 were measured. The serum level of cardiac troponin I, creatine kinase, was detected. The cardiac function and cardiomyocyte apoptosis were evaluated. The activation of TLR4/NF-κB signaling pathway was analyzed. Glycyrrhizin prevented CME-induced production of HMGB1, TNF-α, iNOS, IL-6, and IL-1β. Glycyrrhizin inhibited CME-induced cardiomyocyte apoptosis and the expression of cleaved caspase-3 and Bax, while enhanced the expression of Bcl-2. Glycyrrhizin decreased cardiac troponin I and creatine kinase levels and improved cardiac function. Glycyrrhizin prevented the activation of HMGB1/TLR4/NF-κB signaling pathway. Glycyrrhizin ameliorated myocardial dysfunction in CME rats by preventing inflammation and apoptosis of cardiomyocytes.

Nanostructured aptamer-based sensing platform for highly sensitive recognition of myoglobin

A composite was prepared from PtSn nanoparticles and carbon nanotubes (PtSnNP/CNTs) and applied to the electrochemical determination of myoglobin (Mb). An Mb-aptamer was immobilized on a glassy carbon electrode (GCE), and hexcyanoferrate was used as an electrochemical probe. The PtSnNP/CNTs were synthesized by a microwave-aided ethylene glycol reduction method. Detection is based on electron transfer inhibition that is caused by the folding and conformational change of the Mb-aptamer in the presence of Mb. The amperometric signal for hexacyanoferrate, best measured at 0.2 V vs. Ag/AgCl depends on the concentration of Mb that interacts with the aptamer on the GCE. This approach is selective and sensitive for Mb due to (a) the highly specific recognition ability of the aptamer for Mb, (b) the powerful electronic properties of carbon nanotubes, (c) the arranged decoration of CNTs with PtSnNPs, and (d), the superior electron transfer to hexacyanoferrate. The assay is highly selective, with linear relationships from 0.01-1 nM and 10 nM-200 nM, and a limit of detection as low as 2.2 ± 0.1 pM. The modified GCE was applied to the quantitation of Mb in spiked human serum samples. Graphical abstract Schematic illustration of the method for Mb detection.

An ultrasensitive label free nanobiosensor platform for the detection of cardiac biomarkers

We report the fabrication of a label free nano biosensor platform comprising single nanofiber that is derived out of multi-walled carbon nanotubes (MWCNTs) embedded SU-8 photoresist, for the detection of three important human cardiac biomarkers viz., myoglobin (Myo), cardiac Troponin I (cTn I) and Creatine Kinase-MB (CK-MB). These composite nanofibers were synthesized using electrospinning process. Single nanofibers were aligned between pairs of electrodes in-situ during the electrospinning process. The target proteins were detected using chemiresistive detection methodology. Each biomarker was detected using a specific, single, aligned nanofiber, functionalized with its corresponding monoclonal antibody. Chemiresistive detection involves measuring the change in conductance of the functionalized nanofibers upon the binding of the targeted antigen. The minimum detection limits of Myo, CK-MB and cTn I were experimentally found out to be as low as 6, 20 and 50 fg/ml respectively. No response was observed when the nanofibers were exposed to a non-specific protein, demonstrating excellent specificity to the targeted detection. These MWCNTs embedded SU-8 nanofibers based nanobiosensor platform shows great promise in the detection of cardiac markers and other proteins as they have fast response time, high sensitivity and good specificity.

Nanovesicular liposome-encapsulated hemoglobin (LEH) prevents multi-organ injuries in a rat model of hemorrhagic shock

The goals of resuscitation in hemorrhagic shock are to correct oxygen deficit and to maintain perfusion pressure to the vital organs. We created liposome-encapsulated hemoglobin (LEH) as a nanoparticulate oxygen carrier (216±2nm) containing 7.2g/dl hemoglobin, and examined its ability to prevent the systemic manifestations of hemorrhagic shock (45% blood loss) in a rat model. We collected plasma after 6h of shock and LEH resuscitation, and determined the circulating biomarkers of systemic inflammation and functions of liver, gut, heart, and kidney. As is typical of the shock pathology, a significant increase in the plasma levels of cardiac troponin, liver function enzymes, soluble CD163 (macrophage activation), and creatinine, and the liver/gut myeloperoxidase activity was observed in the hemorrhaged rats. The plasma levels of TNF-α, IL-6, IL-1α, CINC-1, and IL-22 also increased after hemorrhagic shock. LEH administration prevented the hemorrhagic shock-induced accumulation of the markers of injury to the critical organs and pro-inflammatory cytokines. LEH also decreased the plasma levels of stress hormone corticosterone in hemorrhaged rats. Although saline also reduced the circulating corticosterone and a few other tissue injury markers, it was not as effective as LEH in restraining the plasma levels of creatinine, alanine transaminase, CD163, TNF-α, IL-6, and IL-1α. These results indicate that resuscitation with nanoparticulate LEH creates a pro-survival phenotype in hemorrhaged rats, and because of its oxygen-carrying capacity, LEH performs significantly better than saline in hemorrhagic shock.

Sensitive point-of-care monitoring of cardiac biomarker myoglobin using aptamer and ubiquitous personal glucose meter

Myoglobin (Myo), which is one of the early markers to increase after acute myocardial infarction (AMI), plays a major role in urgent diagnosis of cardiovascular diseases. Hence, monitoring of Myo in point-of-care is fundamental. Here, a novel assay for sensitive and selective detection of Myo was introduced using a personal glucose meter (PGM) as readout. In the presence of Myo, the anti-Myo antibody immobilized on the surface of polystyrene microplate could capture the target Myo. Then the selected aptamer against Myo, which was obtained using our screening process, was conjugated with invertase, and such aptamer-invertase conjugates bound to the immobilized Myo due to the Myo/aptamer interaction. Subsequently, the resulting "antibody-Myo-aptamer sandwich" complex containing invertase conjugates hydrolyzed sucrose into glucose, thus establishing direct correlation between the Myo concentration and the amount of glucose measured by PGM. By employing the enzyme amplification, as low as 50 pM Myo could be detected. This assay also showed high selectivity for Myo and was successfully used for Myo detection in serum samples. This work may provide a simple but reliable tool for early diagnosis of AMI in the world, especially in developing countries.

Sorbin and SH3 domain-containing protein 2 is released from infarcted heart in the very early phase: proteomic analysis of cardiac tissues from patients

BACKGROUND

Few proteomic studies have examined human cardiac tissue following acute lethal infarction. Here, we applied a novel proteomic approach to formalin-fixed, paraffin-embedded human tissue and aimed to reveal the molecular changes in the very early phase of acute myocardial infarction.

METHODS AND RESULTS

Heart tissue samples were collected from 5 patients who died within 7 hours of myocardial infarction and from 5 age- and sex-matched control cases. Infarcted and control myocardia were histopathologically diagnosed and captured using laser microdissection. Proteins were extracted using an originally established method and analyzed using liquid chromatography-tandem mass spectrometry. The label-free quantification demonstrated that the levels of 21 proteins differed significantly between patients and controls. In addition to known biomarkers, the sarcoplasmic protein sorbin and SH3 domain-containing protein 2 (SORBS2) was greatly reduced in infarcted myocardia. Immunohistochemical analysis of cardiac tissues confirmed the decrease, and Western blot analysis showed a significant increase in serum sorbin and SH3 domain-containing protein 2 in acute myocardial infarction patients (n=10) compared with control cases (n=11).

CONCLUSIONS

Our advanced comprehensive analysis using patient tissues and serums indicated that sarcoplasmic sorbin and SH3 domain-containing protein 2 is released from damaged cardiac tissue into the bloodstream upon lethal acute myocardial infarction. The proteomic strategy presented here is based on precise microscopic findings and is quite useful for candidate biomarker discovery using human tissue samples stored in depositories.

Cardiac troponins I and T: molecular markers for early diagnosis, prognosis, and accurate triaging of patients with acute myocardial infarction

Acute myocardial infarction (AMI) is the leading cause of death worldwide, with early diagnosis still being difficult. Promising new cardiac biomarkers such as troponins and creatine kinase (CK) isoforms are being studied and integrated into clinical practice for early diagnosis of AMI. The cardiac-specific troponins I and T (cTnI and cTnT) have good sensitivity and specificity as indicators of myocardial necrosis and are superior to CK and its MB isoenzyme (CK-MB) in this regard. Besides being potential biologic markers, cardiac troponins also provide significant prognostic information. The introduction of novel high-sensitivity troponin assays has enabled more sensitive and timely diagnosis or exclusion of acute coronary syndromes. This review summarizes the available information on the potential of troponins and other cardiac markers in early diagnosis and prognosis of AMI, and provides perspectives on future diagnostic approaches to AMI.

Management of acute coronary syndrome: achievements and goals still to pursue. Novel developments in diagnosis and treatment

Acute coronary syndromes contribute a substantial part of the global disease burden. To realize a reduction in mortality and morbidity, the management of patients with these conditions involves the integration of several different approaches. Timely delivery of appropriate care is a key factor, as the beneficial effect of reperfusion is greatest when performed as soon as possible. Innovations in antithrombotic therapy have also contributed significantly to improvements in the prevention of ischaemic complications. However, with the use of such treatment, an increase in the risk of bleeding is inevitable. Therefore, the greatest challenge is now to obtain an optimal balance between the prevention of ischaemic complications and the risk of bleeding. In this regard, identification of patients at highest risk of either one is essential.

Iminodiacetic acid-functionalized gold nanoparticles for optical sensing of myoglobin via Cu2+ coordination

A novel gold nanoparticle (AuNP)-based optical sensing system has been developed for the detection of myoglobin (Mb), which is of significant importance for early disease diagnosis. Two thiol molecules containing an iminodiacetic acid moiety (IDA) were synthesized. This detection is based on the Mb-induced aggregation of IDA-functionalized AuNPs resulting from the structures of Mb sandwiched between the functionalized AuNPs via Cu(2+) bridges in the coordination interactions of IDA-Cu(2+)-histidine residues available on the Mb surface, which was confirmed by UV-vis spectroscopy, transmission electron microscopy, dynamic light scattering, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The induction aggregation resulted in a red shift in plasmon resonance band of the AuNPs concomitant with a change in solution color from red to purple. The qualitative and quantitative detections of Mb can be achieved by colorimetric observations and UV-vis spectral measurements, respectively. The selectivity of protein assay with the functionalized AuNPs was further investigated, and it is found that the optical sensing of histidine-rich proteins is closely related to number and distribution of surface histidine residues as well as size of proteins.

Intravenous hMSCs improve myocardial infarction in mice because cells embolized in lung are activated to secrete the anti-inflammatory protein TSG-6

Quantitative assays for human DNA and mRNA were used to examine the paradox that intravenously (i.v.) infused human multipotent stromal cells (hMSCs) can enhance tissue repair without significant engraftment. After 2 x 10(6) hMSCs were i.v. infused into mice, most of the cells were trapped as emboli in lung. The cells in lung disappeared with a half-life of about 24 hr, but <1000 cells appeared in six other tissues. The hMSCs in lung upregulated expression of multiple genes, with a large increase in the anti-inflammatory protein TSG-6. After myocardial infarction, i.v. hMSCs, but not hMSCs transduced with TSG-6 siRNA, decreased inflammatory responses, reduced infarct size, and improved cardiac function. I.v. administration of recombinant TSG-6 also reduced inflammatory responses and reduced infarct size. The results suggest that improvements in animal models and patients after i.v. infusions of MSCs are at least in part explained by activation of MSCs to secrete TSG-6.

How to find evidence when you need it, part 4: Matching clinical questions to appropriate databases

Practitioners seeking enhancement of clinical care through consideration of research require rapid and efficient point-of-care access to current studies and summaries pertaining to specific clinical queries. MEDLINE and other large databases usually contain the citations relevant to such questions but frequently fall short of the practical requirements of busy clinicians. We present a summary of the knowledge and skills required for physicians to select and use smaller databases appropriate to particular types of questions arising from emergency care. We outline a step-by-step approach that begins at the bedside with the sorting of questions into appropriate categories of knowledge and research design. We identify commonly encountered pitfalls in the process of connecting a particular question to an appropriate database. We illustrate the approach through a set of demonstration questions pertaining to patients presenting to emergency departments with chest pain consistent with acute coronary ischemia. We describe a selection of resources and databases and summarize their performance in locating articles relevant to the demonstration questions.

Test strategies for the detection of myocardial damage

In the space of half a century, cardiac marker testing has advanced incrementally from enzymes present in nearly all tissues to proteins having remarkable specificity for myocardium. Markers with other desirable properties, such as earlier release, have also been introduced and others may be anticipated, although a single perfect marker is not on the horizon. Optimum application of these new markers still requires improved robustness and harmonization of commercial assays, and continuing insights in the pathophysiology of acute coronary syndromes. As these advances occur, future testing will likely focus more on therapeutic decisions than on arbitrary diagnostic classifications.

Retrograde versus antegrade crystalloid cardioplegia in coronary surgery: value of troponin-I measurement

BACKGROUND

The optimal route for delivery of cardioplegia is still in debate in patients with ischemic heart disease. Cardiac troponin-I is a new marker with the potential for detection of minor differences in myocardial ischemia.

METHODS

In a prospective randomized trial 58 patients undergoing elective coronary artery bypass grafting for two- or three-vessel coronary artery disease were divided into groups with antegrade (group A, n = 29) and retrograde (group R, n = 29) application of crystalloid cardioplegia (St. Thomas II). Patients with major risk factors were excluded. In addition to routine electrocardiogram monitoring, cardiac troponin-I and creatine kinase-MB activity were measured in all patients preoperatively at 2, 5, 8, 24, and 48 hours after aortic cross-clamp release, and at hospital discharge.

RESULTS

In both groups, there were no differences regarding operative parameters. A significantly higher cardiac troponin-I concentration was observed in the antegrade group at 24 hours after cross-clamp (8.2 +/- 8.5 microg/L vs 3.2 +/- 3.1 microg/L; p = 0.02). Patients with subtotal stenosis or occlusion of one or more main coronary arteries showed significantly lower cardiac troponin-I levels after retrograde application.

CONCLUSIONS

Lower concentrations of the cardiac troponin-I marker after retrograde application of cardioplegia indicate advantages of myocardial protection in ischemic heart disease.

The sensitivity of cardiac markers: an evidence-based approach

The aim of this study was to determine whether, using an evidence-based approach, the results of the papers found in the literature are valid and sufficiently scientifically rigorous to be used to definitely address the problem of cardiac marker sensitivity in detection of acute myocardial infarction. In particular, the diagnostic sensitivities of myoglobin, creatine kinase (CK)-MB isoenzyme, determined as mass concentration, CK-MB isoforms, and of the two cardiac troponins, troponin I and troponin T, were reviewed using a priori formulated inclusion/exclusion criteria for judging the eligibility of studies to be included in the analysis. A clear final message derived from this systematic analysis is the unacceptably poor diagnostic sensitivity of all evaluated markers at patient admission, with substantial failure rate to rule out myocardial infarction at this time. Myoglobin is at present the most sensitive of the markers studied for excluding early AMI with an optimum timing of sampling at patient presentation and approximately 4 h later. However, this marker cannot be used by itself as a proportion of patients admitted to the hospital with a late infarction could be missed. The early rate of rise of CK-MB mass and troponin T is similar. Maximum sensitivity of these two parameters is achieved by the analysis of a second sample 6 to 12 h after admission. Additional larger studies are needed to address the question which troponin shows earlier release after myocardial damage, and to clarify the role of CK-MB isoforms as a possible early marker of myocardial infarction.

Reflex testing II: evaluation of an algorithm for use of cardiac markers in the assessment of emergency department patients with chest pain

A reflex algorithm was developed and evaluated for the use of serum cardiac markers for the diagnosis and rule out of acute myocardial infarction (AMI), and risk stratification of unstable angina patients for those who present to emergency departments (ED) with chest pain. The process begins with testing of total CK and myoglobin at admission. Based on these results, the algorithm determines the need for subsequent testing for the CK-MB isoenzyme and cardiac troponin I (cTnI). The algorithm also directs the need for further blood collection and cardiac marker testing at 4, 8, and 12 h after presentation. A total of eleven stopping points were identified. For some of these stopping points, the algorithm concluded that further blood collections and testing was unnecessary and redundant. The algorithm was retrospectively evaluated on 101 non-consecutive chest pain patients who presented to the EDs at three hospitals. For the AMI group (n=34), six of nine possible different stopping points were reached: 64.7% of cases were diagnosed with the first sample at admission, an additional 32.3% after 4 h, and 2.9% at 8 h. The 12-h sample was not necessary for any of the AMI patients. For the non-AMI group (n=67), most reached the stopping point of no cardiac injury or risk. There were five unstable angina patients who had minor myocardial damage on the basis of a marginally increased cTnI. Of these, one patient subsequently suffered AMI, and three others required angioplasty or bypass surgery. Compared to performing four tests on all patient samples, the reflex algorithm would have reduced the number of necessary tests from 442 to 130 (71% reduction) for AMI patients, and 871 to 469 (46% reduction) for non-AMI patients, if prospectively implemented.

National Academy of Clinical Biochemistry Standards of Laboratory Practice: Recommendations for the Use of Cardiac Markers in Coronary Artery Diseases

The Sixth Conference on the “Standards of Laboratory Practice Series”, sponsored by the National Academy of Clinical Biochemistry (NACB), was held on August 4–5, 1998, at the Annual Meeting of the American Association for Clinical Chemistry, in Chicago, IL. An expert committee was assembled to write recommendations on the use of cardiac markers in coronary artery diseases. The NACB Committee prepared a preliminary draft of the guidelines, made them available on the World Wide Web (www.nacb.org), and distributed them before the presentations. The recommendations were divided into four areas: the use of markers in the triage of patients with chest pain, acute coronary syndromes, clinical applications other than acute myocardial infarction and research, and assay platforms and markers of acute myocardial infarction. The recommendations were revised and subsequently re-presented in part at the “Biomarkers in Acute Cardiac Syndromes Conference”, sponsored by the Jewish Hospital Heart and Lung Institute, Louisville KY, on October 16–17, 1998. This report lists each recommendation, its scientific justification, and a summary of discussions from conference participants and reviewers.

Approximately 100 individuals responded to various versions of these recommendations via direct correspondences, telephone calls to Committee members, electronic mail correspondence to the Committee Chairman, or oral questions and comments raised during one of the two conference presentations. Some of the recommendations were changed to reflect the consensus opinion. In cases in which there was no consensus, the Committee included pertinent discussion without necessarily changing the original recommendations. At times, the Committee members felt that although a particular recommendation might not be the current standard of care today, they anticipate that it likely will be adopted in the near future.

Elevation of serum cardiac troponin I in noncardiac and cardiac diseases other than acute coronary syndromes

This study evaluated the role of serum cardiac troponin I as a biochemical marker for the diagnosis of acute coronary syndromes in the presence of noncardiac diseases. Diagnostic characteristics were examined in 102 consecutive patients who were found to have serum cardiac troponin I levels higher than the upper reference limit of 0.6 ng/mL. Of 102 patients with cardiac troponin I levels of >0.6 ng/mL, 35 did not have the final diagnoses of acute coronary syndromes (myocardial infarction or unstable angina) but had various other final diagnoses, including nonischemic dilated cardiomyopathy, muscular disorders, central nervous system disorders, HIV disease, chronic renal failure, sepsis, lung diseases, and endocrine disorders. The mean value of serum cardiac troponin I in the patients with diseases other than acute coronary syndromes was significantly lesser than in those with acute coronary syndromes (2.0+/-1.9 [SD] v. 24.7+/-28.2 ng/mL; P<.0001). There were significantly fewer histories of chest pain and prior myocardial infarction in patients with diseases other than acute coronary syndromes than in those with acute coronary syndromes (history of chest pain, 3 v. 48 patients [P<.001]; history of prior myocardial infarction, 0 v. 30 patients [P<.001]). In conclusion, elevated serum levels of cardiac troponin I, especially in the lower ranges, should be interpreted with caution, particularly in patients suffering from acute illnesses who lack other diagnostic features suggestive of acute coronary ischemic events.

A proposed strategy for utilization of creatine kinase-MB and troponin I in the evaluation of acute chest pain

In recent years, cardiac troponins have attracted great interest as a marker for myocardial injury. However, there are limited data on strategies for use of creatine kinase (CK)-MB and troponin I (cTnI) in clinical practice. We sought to develop a testing strategy using prospectively collected clinical data including serial CK-MB and cTnI levels from 1,051 patients aged > or = 30 years admitted to a teaching hospital for acute chest pain. Diagnostic performance was evaluated for peak values of CK-MB and cTnI obtained during the first 24 hours for the combined end point of acute myocardial infarction and/or major cardiac events within 72 hours. The overall diagnostic accuracy was similar for both cardiac markers alone, and for the combination of cTnI and CK-MB (receiver-operating characteristic curve 0.84, 0.86, and 0.87, respectively). In the multivariate analysis, models including cardiac markers showed that both CK-MB and cTnI added information to clinical data to predict the combined end point, but cTnI added significantly less. Using recursive partitioning analysis, we developed a strategy that would restrict routine cTnI use to patients with normal CK-MB results and findings on the electrocardiogram consistent with ischemia. This strategy would divide patients with suspected myocardial ischemia into 4 groups with risks for the combined end point of 4%, 13%, 26%, and 85%. Thus, cTnI adds information to CK-MB mass and clinical data for predicting major cardiac events, but this contribution is mainly in patients with evidence of myocardial ischemia on their electrocardiograms.

Early laboratory indicators of acute myocardial infarction

Biochemical markers of myocardial injury have evolved so that the diagnosis or exclusion of acute myocardial infarction can be determined within a short time with a high degree of sensitivity and specificity. The use of these markers in patients complaining of chest pain allows for medically appropriate and cost-effective triage decision making in the emergency department.