Cardiac Biomarkers for Detection of Myocardial Infarction: Perspectives from Past to Present

A Future Blood Test to Detect Cerebral Aneurysms

Intracranial aneurysms are reported to affect 2-5% of the population. Despite advances in the surgical management of this disease, diagnostic technologies have marginally improved and still rely on expensive or invasive imaging procedures. Currently, there is no blood-based test to detect cerebral aneurysm formation or quantify the risk of rupture. The aim of this review is to summarize current literature on the mechanism of aneurysm formation, specifically studies relating to inflammation, and provide a rationale and commentary on a hypothetical future blood-based test. Efforts should be focused on clinical-translational approaches to create an assay to screen for cerebral aneurysm presence and risk-stratify patients to allow for superior treatment timing and management. Cerebral Aneurysm Blood Test Considerations: There are multiple caveats to development of a putative blood test to detect cerebral aneurysm presence.

Protocatechuic acid reverses myocardial infarction mediated by β-adrenergic agonist via regulation of Nrf2/HO-1 pathway, inflammatory, apoptotic, and fibrotic events

Myocardial infarction (MI) is an instant ischemic death of cardiomyocytes that remains a major global cause of mortalities. MI is accompanied by oxidative, inflammatory, apoptotic, and fibrotic insults. Protocatechuic acid (PCA) is a polyphenolic compound with various potent biological activities. In this study, we explored the possible cardioprotective role of PCA against isoproterenol (ISO)-mediated MI. Rats were either injected with ISO (85 mg/kg, subcutaneously) or pretreated with PCA (100 or 200 mg/kg, orally). PCA supplementation markedly normalized ISO-induced disturbed cardiac function markers (creatine kinase-MB, lactate dehydrogenase, and troponin T). Notably, PCA administration exerted remarkable increases in glutathione and its derived enzymes, superoxide dismutase, and catalase, as well as decreases in malondialdehyde and nitric oxide levels in the injured cardiac tissue. The molecular findings validated the augmented cellular antioxidative capacity by PCA via increasing the gene expressions of nuclear factor erythroid 2-related factor 2 and heme oxygenase-1. The cardioprotective efficacy of PCA extended to suppress cardiac inflammation as demonstrated by the decreased levels of tumor necrosis factor-alpha, interleukin-1 beta, and nuclear factor kappa B. Additionally, PCA prevented cardiomyocyte loss and fibrosis by decreasing Bax, caspase-3, transforming growth factor-β1 and matrix metalloproteinase-9, and enhancing B-cell lymphoma 2 and tissue inhibitors of metalloproteinase-3. The cardiac histological screening further confirmed the PCA's protective action. The obtained data recommend PCA as an alternative therapeutic agent to attenuate the molecular, biochemical, and histological alterations associated with MI development.

Acute Myocardial Infarction Biosensor: A Review From Bottom Up

Acute myocardial infarction (AMI) is a cardiovascular disease that is produced due to a deficiency of oxygen generating irreversible damage in the heart muscle. In diagnosis, electrocardiogram (ECG) investigation has been the main method but is insufficient, so approaches like the measurement of biomarkers levels in plasma or saliva have become one of the most commonly applied strategies for prognosis of AMI, as some of them are specifically related to a heart attack. Many tests are carrying on to determine biological markers changes, but usually, they present disadvantages related to time consumption and laborious work. To overcome the issues, researchers around the world have been developing different ways to enhance detection through the use of biosensors. These diagnostic devices have a biological sensing element associated to a physicochemical transducer that can be made from different materials and configurations giving place to different kinds of detection: Electrical/Electrochemical, Optical and Mechanical. In this review, the authors presents relevant investigations related to the most important biomarkers and biosensors used for their detection having in mind the nanotechnology participation in the process through the application of nanostructures as a good choice for device configuration.

Prognostic impact of the combination of serum transaminase and alkaline phosphatase determined in the emergency room in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention

Background

Elevated serum transaminase or alkaline phosphatase (ALP) has been proposed as a novel prognosticator for ST-segment elevation myocardial infarction (STEMI). We evaluated the combined prognostic impact of elevated serum transaminases and ALP on admission in STEMI patients who underwent primary percutaneous coronary intervention (PCI).

Methods

A total of 1176 patients with STEMI undergoing primary PCI were retrospectively enrolled from the INTERSTELLAR registry. Hypoxic liver injury (HLI) was defined as serum transaminase > twice the upper limit of normal. The cut-off value of high ALP was set at the median level (73 IU/L). Patients were divided into four groups according to their serum transaminase and ALP levels. The primary endpoint was major adverse cardiac or cerebrovascular events (MACCE), defined as the composite of all-cause death, non-fatal myocardial infarction, non-fatal stroke, and ischemia-driven revascularization.

Results

Median follow-up duration was 25 months (interquartile range, 10–39 months). The rate of MACCE was highest in patients with HLI (+) and high ALP (25.9%), compared to those in the other groups (8.2% in HLI [-] and low ALP, 11.8% in HLI [-] and high ALP, and 15.0% in HLI [+] and low ALP). Each of HLI or high ALP was an independent predictor for MACCE (HR 1.807, 95% CI 1.191–2.741; HR 1.721, 95% CI 1.179–2.512, respectively). Combined HLI and high ALP was associated with the worst prognosis (HR 3.145, 95% CI 1.794–5.514).

Conclusions

Combined HLI and high ALP on admission is associated with poor clinical outcomes in patients with STEMI who have undergone primary PCI.

Remifentanil attenuates cardiac dysfunction, lipid peroxidation and immune disorder in rats with isoproterenol-induced myocardial injury via JNK/NF-KB p65 inhibition

Background

Myocardial injury caused by myocardial ischemia (MI) is still a severe condition that can result in apoptosis, oxidative stress, and inflammation. Remifentanil is a selective, ultra-short-acting, µ-opioid receptor agonist opioid. It can improve sinusoidal heart rate patterns in the fetus, for bupivacaine-induced cardiotoxicity, and with lipopolysaccharide (LPS)-induced cardiomyocytes injuries. This study aimed to explore the cardioprotective effects of remifentanil in MI model rats.

Methods

Sprague Dawley (SD) rats were split into five groups at random, including a control group, Isop group, low-dose remifentanil treatment group (10 µg/kg), medium-dose remifentanil treatment group (20 µg/kg), and a high-dose remifentanil treatment group (40 µg/kg). The MI model was achieved by subcutaneously injecting rats with isoproterenol (85 mg/kg) for two consecutive days. With the expression of apoptotic molecules, myocardial systolic function index, inflammation, antioxidant enzymes, and the myocardial enzyme taken into account, the data was analyzed.

Results

After treatment with remifentanil, the left ventricular wall thickness (LVWT), left ventricular end-systolic volume (LVESV), left ventricular ejection fraction (LVEF), fraction shortening (FS), and heart rate (HR) were significantly increased in comparison with the Isop group. Creatine kinase-MB (CK-MB), Mb, and cTnl expressions were decreased. Meanwhile, the levels of cleaved caspase-3 and caspase-9 were decreased. Remarkably, the levels of reactive oxidative species (ROS), malondialdehyde (MDA), and lactate dehydrogenase (LDH) were observed to be repressed, while the levels of superoxide dismutase (SOD) was significantly increased. More importantly, the levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, and interferon (IFN)-γ were decreased.

Conclusions

Remifentanil has significant potential as a therapeutic intervention strategy for ameliorating myocardial injury after MI and these findings provide the rationale for further clinical studies.

Cardioprotective effect of Amaranthus tricolor extract in isoprenaline induced myocardial damage in ovariectomized rats

Red spinach (Amaranthus tricolor) has been reported to possess many benefits and medicinal properties and used as a part of traditional medicine in Ayurveda and Siddha. The aim of the study was to investigate the effects of Amaranthus tricolor on isoproterenol-induced oxidative stress, fibrosis, and myocardial damage in ovariectomized rats. Ovariectomy surgery was conducted to remove both ovaries from the rats. After recovery, rats were administered with ISO subcutaneously (50 mg/kg) twice a week and were treated with ethanolic extracts of A. tricolor. This investigation showed that the level of oxidative stress markers was significantly increased while the superoxide dismutase (SOD) activity decreased in ISO administered ovariectomized rats. A. tricolor extract and atenolol treatment prevented the rise of malondialdehyde, nitric oxide and advanced protein oxidation product. Moreover, elevated activities of AST, ALT, and CK-MB enzymes were also lowered by both atenolol and A. tricolor treatment. Increased uric acid and creatinine levels were also normalized by atenolol, and A. Tricolor treatment in ISO administered ovariectomized rats. ISO-induced ovariectomized rats also showed massive inflammatory cell infiltration, fibrosis and iron deposition in heart compared to sham rats. Atenolol and A. tricolor treatment prevented the inflammatory cells infiltration, fibrosis, and iron deposition. These results suggest that A. tricolor treatment may protect against ISO administered myocardial infarction in ovariectomized rats probably by preventing inflammation, oxidative stress, and fibrosis. Further research is warranted to examine molecular mechanism of cardioprotective effect of A. tricolor.

Changing concept in treatment of asymptomatic severe aortic stenosis and normal ejection fraction: time for biomarkers reappraisal

The uncertainty of whether/how to treat asymptomatic patients with isolated severe aortic stenosis and normal left ventricular ejection fraction is one of the most topical in cardiovascular medicine. Recently, the AVATAR trial: first ever randomized trial in the setting of aortic stenosis has been started in an attempt to adequately address this 'burning issue'. In light of this fact it is important to identify biomarkers which might help in risk stratification of these patients, not only in the referring physician's office during a routine exam, but also for preoperative patients scheduled for surgical replacement/transcatheter aortic valve implantation. This report is focusing on novel laboratory parameters which might be helpful in this risk stratification.

Aptamer-Based Microfluidic Electrochemical Biosensor for Monitoring Cell-Secreted Trace Cardiac Biomarkers

Continual monitoring of secreted biomarkers from organ-on-a-chip models is desired to understand their responses to drug exposure in a noninvasive manner. To achieve this goal, analytical methods capable of monitoring trace amounts of secreted biomarkers are of particular interest. However, a majority of existing biosensing techniques suffer from limited sensitivity, selectivity, stability, and require large working volumes, especially when cell culture medium is involved, which usually contains a plethora of nonspecific binding proteins and interfering compounds. Hence, novel analytical platforms are needed to provide noninvasive, accurate information on the status of organoids at low working volumes. Here, we report a novel microfluidic aptamer-based electrochemical biosensing platform for monitoring damage to cardiac organoids. The system is scalable, low-cost, and compatible with microfluidic platforms easing its integration with microfluidic bioreactors. To create the creatine kinase (CK)-MB biosensor, the microelectrode was functionalized with aptamers that are specific to CK-MB biomarker secreted from a damaged cardiac tissue. Compared to antibody-based sensors, the proposed aptamer-based system was highly sensitive, selective, and stable. The performance of the sensors was assessed using a heart-on-a-chip system constructed from human embryonic stem cell-derived cardiomyocytes following exposure to a cardiotoxic drug, doxorubicin. The aptamer-based biosensor was capable of measuring trace amounts of CK-MB secreted by the cardiac organoids upon drug treatments in a dose-dependent manner, which was in agreement with the beating behavior and cell viability analyses. We believe that, our microfluidic electrochemical biosensor using aptamer-based capture mechanism will find widespread applications in integration with organ-on-a-chip platforms for in situ detection of biomarkers at low abundance and high sensitivity.

Liver and cholestatic parameters as prognostic biomarkers of in-hospital MACE in patients with STEMI

BACKGROUND

Liver and cholestatic parameters are increased in ST-segment elevation myocardial infarction (STEMI). The aim of the present study was to evaluate the prognostic value of these parameters to predict in-hospital major adverse cardiac events (MACE) in patients after STEMI.

MATERIALS AND METHODS

Blood samples of patients with STEMI, who underwent percutaneous coronary intervention (PCI) and stent implantation, were retrospectively analysed and correlated with in-hospital events.

RESULTS

The study population consisted of 847 consecutive patients (62·4 ± 13·43 years; 73·8% male). The total in-hospital MACE rate was 9·8%, driven by death of any cause (8·4%). The Mann-Whitney U-test revealed that liver and cholestatic parameters (alanine transaminase P < 0·0001, aspartate transaminase P < 0·0001, alkaline phosphatase (AP) P < 0·0001, gamma-glutamyl transferase P = 0·0006 and total bilirubin P = 0·0023) were significantly higher in the MACE group. Further logistic regression analyses confirmed the correlation between MACE and all five laboratory markers, even after adjustment for age and heart enzymes. Logistic regression model revealed AP to be the best predictor for worth outcome (OR 1·0188; 95% CI 1·0118-1·0258; P < 0·0001).

CONCLUSION

Liver and cholestatic parameters are elevated in patients after STEMI. Increased AP is associated with in-hospital event rates.

An historical approach to the diagnostic biomarkers of acute coronary syndrome

Suspected acute myocardial infarction (AMI) is one of the leading causes of admission to the emergency departments in Western countries but also an increasing cause in many other nations. The diagnosis of AMI involves the evaluation of clinical signs and symptoms, electrocardiographic assessment, and measurement of cardiac circulating biomarkers. In the last sixty years, the use of laboratory markers has changed considerably. Early biomarkers assessment has entailed testing for total enzyme activity of aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and creatine kinase (CK). Advances in electrophoresis allowed the identification of more cardio-specific isoenzymes of both CK and LDH, thus leading to the introduction of the CK-MB and LDH-1 activity assays. Soon thereafter, the development of immunoassays, as well as technical advances in automation, allowed the measurements of the CK-MB in mass rather than in activity and myoglobin. Currently, cardiac troponins have the highest sensitivity and specificity for myocardial necrosis and represent the biochemical gold standard for diagnosing AMI. This review provides a chronology of the major events which marked the evolution of cardiac biomarkers testing and the development of the relative assays from the first introduction of AST in the 1950s to the last high sensitivity troponin immunoassays in the 2010s.

Troponin elevations in patients with chronic cardiovascular disease: An analysis of current evidence and significance

Serum troponin elevation above the 99^th percentile of the upper reference limit in healthy subjects (<0.01 ng/ml measured using currently available high-sensitivity cardiac troponin laboratory assays) is required to establish the diagnosis the diagnosis of myocardial necrosis in acute cardiovascular syndromes, as well as guide prognosis and therapy. In the perioperative period, for patients with cardiac disease undergoing noncardiac surgery, it is a particularly critical biomarker universally used to assess the myocardial damage. The value of troponin testing and elevation (as well as its significance) in patients with chronic cardiac valvular, vascular, and renal disease is relatively less well understood. This evidence-based review seeks to examine the currently available data assessing the significance of troponin elevation in certain chronic valvular and other disease states.

Xanthine Oxidase Inhibitor, Allopurinol, Prevented Oxidative Stress, Fibrosis, and Myocardial Damage in Isoproterenol Induced Aged Rats

We evaluated the preventive effect of allopurinol on isoproterenol (ISO) induced myocardial infarction in aged rats. Twelve- to fourteen-month-old male Long Evans rats were divided into three groups: control, ISO, and ISO + allopurinol. At the end of the study, all rats were sacrificed for blood and organ sample collection to evaluate biochemical parameters and oxidative stress markers analyses. Histopathological examinations were also conducted to assess inflammatory cell infiltration and fibrosis in heart and kidneys. Our investigation revealed that the levels of oxidative stress markers were significantly increased while the level of cellular antioxidants, catalase activity, and glutathione concentration in ISO induced rats decreased. Treatment with allopurinol to ISO induced rats prevented the elevated activities of AST, ALT, and ALP enzymes, and the levels of lipid peroxidation products and increased reduced glutathione concentration. ISO induced rats also showed massive inflammatory cells infiltration and fibrosis in heart and kidneys. Furthermore, allopurinol treatment prevented the inflammatory cells infiltration and fibrosis in ISO induced rats. In conclusion, the results of our study suggest that allopurinol treatment is capable of protecting heart of ISO induced myocardial infarction in rats probably by preventing oxidative stress, inflammation, and fibrosis.

Diagnostics on acute myocardial infarction: Cardiac troponin biomarkers

Acute myocardial infarction or myocardial infarction (MI) is a major health problem, due to diminished flow of blood to the heart, leads to higher rates of mortality and morbidity. Data from World Health Organization (WHO) accounted 30% of global death annually and expected more than 23 million die annually by 2030. This fatal effects trigger the need of appropriate biomarkers for early diagnosis, thus countermeasure can be taken. At the moment, the most specific markers for cardiac injury are cardiac troponin I (cTnI) and cardiac troponin T (cTnT) which have been considered as 'gold standard'. Due to higher specificity, determination of the level of cardiac troponins became a predominant indicator for MI. Several ways of diagnostics have been formulated, which include enzyme-linked immunosorbent assay, chemiluminescent, fluoro-immunoassays, electrical detections, surface plasmon resonance, and colorimetric protein assay. This review represents and elucidates the strategies, methods and detection levels involved in these diagnostics on cardiac superior biomarkers. The advancement, sensitivity, and limitations of each method are also discussed. In addition, it concludes with a discussion on the point-of care (POC) assay for a fast, accurate and ability of handling small sample measurement of cardiac biomarker.

Cardioprotective effect of rhizomes of Acorus gramineus against isoproterenol-induced cardiac damage in pigs

The present study was designed to evaluate the cardioprotective potential of water extract of rhizomes of Acorus gramineus (AGR) against isoproterenol (ISO)-induced myocardial infarction. Male pigs were orally administered with 250 or 500 mg/kg of AGR or with vehicle for 9 days, with concurrent subcutaneous injections of ISO on the 8th and 9th day. Administration of AGR significantly ameliorated ISO-induced cardiac dysfunctions as evidenced by the ventricular ST-segment interval and R-amplitude as well as the left ventricle fractional shortening and ejection fraction. Additionally, administration of AGR significantly attenuated increased cardiac injury markers, such as cardiac troponin T, tumor necrosis factor-α, and myeloperoxidase activity, and cardiac marker enzymes, and prevented the depletion of antioxidant parameters. Malondialdehyde formation was also inhibited by AGR. Based on the results, it is concluded that AGR possesses significant cardioprotective potential and may serve as an adjunct in the treatment and prophylaxis of myocardial infarction.

Introduction of high-sensitivity troponin assays: impact on myocardial infarction incidence and prognosis

OBJECTIVE

The study objective was to compare the incidence and prognosis of acute myocardial infarction when using high-sensitivity cardiac troponin assays instead of a standard cardiac troponin assay for the diagnosis of acute myocardial infarction.

METHODS

In a prospective international multicenter study, we enrolled 1124 consecutive patients presenting with suspected acute myocardial infarction. Final diagnoses were adjudicated by 2 independent cardiologists 2 times using all available clinical information: first using standard cardiac troponin levels and second using high-sensitivity cardiac troponin T levels for adjudication. Patients were followed up for a mean of 19±9 months.

RESULTS

The use of high-sensitivity cardiac troponin T instead of standard cardiac troponin resulted in an increase in the incidence of acute myocardial infarction from 18% to 22% (242 vs 198 patients), a relative increase of 22%. Of the 44 additional acute myocardial infarctions, 35 were type 1 acute myocardial infarctions and 9 were type 2 acute myocardial infarctions. This was accompanied by a reciprocal decrease in the incidence of unstable angina (unstable angina, 11% vs 13%). The most pronounced increase was observed in patients adjudicated with cardiac symptoms of origin other than coronary artery disease with cardiomyocyte damage (83 vs 31 patients, relative increase of 268%). Cumulative 30-month mortality rates were 4.8% in patients without acute myocardial infarction, 16.4% in patients with a small acute myocardial infarction detected only by high-sensitivity cardiac troponin T but not standard cardiac troponin, and 23.9% in patients with a moderate/large acute myocardial infarction according to standard cardiac troponin assays and high-sensitivity cardiac troponin T (P<.001).

CONCLUSIONS

The introduction of high-sensitivity cardiac troponin assays leads to only a modest increase in the incidence of acute myocardial infarction. The novel sensitive assays identify an additional high-risk group of patients with increased mortality, therefore appropriately classified with acute myocardial infarction (Advantageous Predictors of Acute Coronary Syndromes Evaluation; NCT00470587).

Clinical evaluation of a matrix metalloproteinase-12 cleaved fragment of titin as a cardiovascular serological biomarker

BACKGROUND

Titin is a muscle-specific protein found in cardiac and skeletal muscles which is responsible for restoring passive tension. Levels and functioning of titin have been shown to be affected by cardiac damage. Due to the inherent difficulty of measuring titin levels in vivo in a clinical setting, we aimed to develop an assay that could reliably measure fragments of degraded titin in serum and potentially be used in the assessment of cardiac muscle damage.

METHODS

A competitive ELISA was developed to specifically measure levels of the titin sequence 12670' NVTVEARLIK 12679', derived by the degradation of titin by matrix metalloproteinase (MMP)-12. Serum samples from 90 individuals were divided into 3 equally sized groups. One group had been diagnosed with acute myocardial infarction (AMI) while the remaining two were asymptomatic individuals either with CT-scan signs of coronary calcium (CT-plusCa) or without coronary calcium (CT-noCa).

RESULTS

Mean geometric levels of the titin fragment in the CT-noCa group were 506.5 ng/ml (± 43.88). The CT-plusCa group showed 50.6% higher levels of the marker [763 ng/ml (± 90.14)] (P < 0.05). AMI patients showed 56.3% higher levels [792 ng/ml (± 149)] (P < 0.05).

CONCLUSIONS

The titin-12670 fragment is present in both individuals with undiagnosed and diagnosed CVD. The statistically significant increase in level of the marker in the AMI group is indicative that this neoepitope biomarker may be a useful serological marker in AMI.

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.

Cardioprotective effects of glycyrrhizic acid against isoproterenol-induced myocardial ischemia in rats

The aim of the present study was to look into the possible protective effects of glycyrrhizic acid (GA) against isoproterenol-induced acute myocardial infarction in Sprague-Dawley rats. The effect of three doses of glycyrrhizic acid in response to isoproterenol (ISO)-induced changes in 8-isoprostane, lipid hydroperoxides, super oxide dismutase and total glutathione were evaluated. Male Sprague-Dawley rats were divided into control, ISO-control, glycyrrhizic acid alone (in three doses-5, 10 and 20 mg/kg BW) and ISO with glycyrrhizic acid (in three doses) groups. ISO was administered at 85 mg/kg BW at two consecutive days and glycyrrhizic acid was administered intraperitoneally for 14 days. There was a significant increase in 8-isoprostane (IP) and lipid hydroperoxide (LPO) level in ISO-control group. A significant decrease in total superoxide dismutase (SOD) and total glutathione (GSH) was seen with ISO-induced acute myocardial infarction. Treatment with GA significantly increased SOD and GSH levels and decreased myocardial LPO and IP levels. Histopathologically, severe myocardial necrosis and nuclear pyknosis and hypertrophy were seen in ISO-control group, which was significantly reduced with GA treatment. Gycyrrhizic acid treatment proved to be effective against isoproterenol-induced acute myocardial infarction in rats and GA acts as a powerful antioxidant and reduces the myocardial lipid hydroperoxide and 8-isoprostane level.

Investigation of peptide biomarker stability in plasma samples using time-course MS analysis

Peptide biomarkers in plasma or serum are subject to proteolytic degradation caused by intrinsic peptidase activities, resulting in a potential barrier in translating a discovered biomarker into clinical application. This chapter describes a method using time-course MALDI-TOF MS analysis to investigate the stability of a plasma peptide biomarker under a variety of preanalytical situations. A synthesized peptide with the same primary sequence as a potential endogenous biomarker is spiked into a blood sample, and the sample is incubated over time at r.t. (25  ±  1°C) or other preanalytical situations. At a specific period of incubation time, the sample is quenched with the addition of acid with or without an internal control peptide. The spiked peptides in the sample are extracted with one of three procedures for highly soluble, moderately soluble, or essentially insoluble peptides. The peptide samples are then analyzed using MALDI-TOF MS. The abundance changes of the peptide biomarker are monitored by time-course changes of the mass spectra. These changes over-time are measured and fitted to a first-order degradation reaction so that stability of the peptide biomarker (half-life) can be calculated. Kinetics analysis of both parent and shorter (daughter) peptides are also possible by fitting to a sequential multiple-step reaction (SMSR) model. This optimized method facilitates evaluation of biomarker stability, and helps to define sample handling and analytical processing steps that contribute to instability of measured peptide biomarker(s).

Tei index (myocardial performance index) and cardiac biomarkers in dogs with parvoviral enteritis

Tei index (myocardial performance) and cardiac biomarkers were evaluated in dogs with parvoviral enteritis (PVE). Tei index was calculated as isovolumic contraction time plus isovolumic relaxation time divided by ejection time. Myocardial and skeletal muscle damages were assessed by serum levels of cardiac troponin I (cTnI), creatine (phospho) kinase, lactate dehydrogenase and aspartate aminotransferase. Serum magnesium level was also determined. According to treatment response, dogs were divided into the survivor (n=20) and non-survivor groups (n=23). Seven healthy dogs served as controls. The mean value of the Tei index was higher in non-survivors, compared with survivors (p<0.02) and healthy controls (p<0.01). Serum level of cTnI in non-survivors was higher than that of survivors and controls (p<0.05). Tei index showed the highest sensitivity and specificity to predict mortality. The findings of an elevated Tei index and an increase in serum cTnI are factors associated with a poor prognosis in cases of canine parvovirosis.

Protein detection enhanced by 3DNA dendrimer signal amplification

DNA dendrimers, conjugated with both anti-biotin antibodies and up to 350 labeling entities, were designed and adapted to protein microarray and enzyme-linked immunosorbent assay (ELISA) to improve the limits of protein detection with no additional steps or equipment. Application of conjugated dendrimers to standard ELISA cytokine detection resulted in up to threefold improvement of the limits of detection with no significant increase in the inter- and intra-assay coefficient of variation (CV) compared to streptavidin horseradish peroxidase (SA-HRP) detection. The adaptation of conjugated dendrimers to protein microarray cytokine detection resulted in up to 10-fold improvement of the limits of detection, but assay conditions would have to be optimized to decrease the intra- and inter-assay %CVs.

Biomarkers of tissue injury

Biomarkers of tissue injury have evolved empirically over the last 50–100 years. With the advent of immunoassays and discovery tools such as RNA expression and proteomics, more systematic approaches to the discovery of biomarkers can be expected in the future. This review discusses the evolution of biomarkers of muscle, liver, heart and brain injury and illustrates that a modern discovery tool, such as mRNA profiling, would have predicted the biomarkers for cardiac injury (heart attacks) that actually evolved over 50 years by empiric approaches. We also discuss how novel biomarkers for brain injury were identified using RNA expression approaches. It is our prediction that there will be a growth in the number of valuable biomarkers for identifying cell and organ injury in the next 5–10 years.

Biomarkers in translation; past, present and future

The search for biomarkers and their evaluation by scientists and clinicians is of paramount importance if we are going to improve health care. In this paper we discuss the history of the discovery of biomarkers for renal and cardiac injury. We also summarize the use of biomarkers in preclinical evaluation in experimental animals and in patients to help diagnose or monitor a disease, predict outcome or to evaluate a therapeutic intervention. The need for validated biomarkers of tissue injury or disease that must be easy to analyse rapidly, preferably at the bedside, is essential if clinical decision making is to be optimally affected by their use.

A personal history of markers of myocyte injury [myocardial infarction]

BACKGROUND

The measurement of proteins in blood to reflect damage to the heart is one of the most successful examples of easily measured biomarkers identifying a serious major health problem. The concept of using a blood test to reflect organ or cell injury requires a substance that is very abundant in the target cell, has a means of reaching blood, a reasonable half-life in blood, and ideally a specific form reflective only of the target cell in tissue. The myocyte's major role is contraction so proteins involved in contraction or the energy to support it should be good candidate markers.

CONCLUSIONS

All the various biomarkers that have been used to detect cardiac damage are involved in contraction or energy metabolism, but the markers evolved empirically starting with transaminases in the 1950s leading to troponins in the 1990s. This history is reviewed with reflections on my experiences with developing assays for CK-MB and Troponin I.

Potential value for new diagnostic markers in the early recognition of acute coronary syndromes

The diagnostic approach to acute coronary syndromes (ACS) remains one of the most difficult and controversial challenges facing emergency physicians. In recent years, cardiac troponins have emerged as the biochemical "gold standard" for diagnosis of patients with acute chest pain, enhancing our ability to recognize ACS. Early diagnosis and treatment of myocardial ischemia improve patient outcomes, but conventional markers are often nondiagnostic at the time of arrival at the emergency department. Promising new biomarkers, which appear earlier after the onset of ischemia, are being studied and integrated into clinical practice. Some are markers of myocyte necrosis, but others, including ischemia-modified albumin and natriuretic peptides, detect myocardial ischemia and myocardial dysfunction. The aim of the present article is to review the diagnostic approach to ACS, focusing on recent literature describing novel biochemical markers. If ongoing and future studies confirm their role in probability-based models risk assessment, a new era in the diagnostic approach to ACS may be dawning.

Evaluation of cardiac laboratory markers in patients with systemic sclerosis

OBJECTIVES

Myocardial involvement is frequent in systemic sclerosis, but symptoms are usually delayed and non-specific, thus often misrecognized. The aim of this study was the evaluation of the early subclinical cardiac involvement in patients with systemic sclerosis by means of non-invasive laboratory cardiac markers.

DESIGN AND METHODS

Cardiac troponin T (cTnT), ischemia modified albumin (IMA) and NT-prohormone-brain natriuretic peptide (NT-proBNP) were measured in 40 female patients with systemic sclerosis and in 40 matched healthy controls.

RESULTS

Patients with systemic sclerosis displayed significantly increased concentrations of serum IMA (106 versus 93.5 kunits/l, P < 0.0001) and NT-proBNP (89 versus 37 pg/ml, P < 0.0001), whereas no significant differences could be observed in both IMA and NT-proBNP values in limited versus diffuse pattern of disease.

CONCLUSIONS

The increased levels of NT-proBNP and IMA could be considered a sign of early myocardial involvement, warranting further heart examination and a regular follow-up.

N-terminal pro-brain natriuretic peptide on admission in patients with acute myocardial infarction and correlation with scintigraphic infarct size, efficacy of reperfusion, and prognosis

We investigated whether N-terminal pro-brain natriuretic peptide (NT-pro-BNP) that was measured on admission in patients with acute myocardial infarction (AMI) predicts the efficacy of reperfusion or whether NT-pro-BNP provides prognostic information independent of infarct size as estimated by single-photon emission computed tomographic scintigraphy. The study included 174 patients with ST-segment elevation AMI who were admitted within 24 hours of pain onset. NT-pro-BNP level was measured on admission. Paired scintigraphic studies (before and 7 to 14 days after reperfusion) were performed to assess infarct size and define myocardial salvage. One-year clinical follow-up was assessed. Patients were categorized into the high NT-pro-BNP group (57 patients in the upper tertile of NT-pro-BNP) and low NT-pro-BNP group (117 patients in the middle and lower tertiles of NT-pro-BNP). Initial median perfusion defect was 35.0% (interquartile rage 20.0 to 53.0%) of the left ventricle in the high NT-pro-BNP group versus 19.0% (interquartile range 10.0 to 32.2) of the left ventricle in the low NT-pro-BNP group (p <0.001). Median salvage index was 0.36 (interquartile range 0.16 to 0.86) in the high NT-pro-BNP group versus 0.53 (interquartile range 0.31 to 0.75) in the low NT-pro-BNP group (p = 0.22). After adjustment in Cox's proportional hazards model, NT-pro-BNP remained an independent correlate of 1-year mortality (adjusted hazard ratio 2.31, 95% confidence interval 1.09 to 4.89, p = 0.03, high vs low NT-pro-BNP group). In conclusion, NT-pro-BNP measured on admission in patients with AMI correlates with scintigraphic area at risk and predicts prognosis but does not predict the efficacy of mechanical reperfusion by stenting or angioplasty.

The exciting story of cardiac biomarkers: from retrospective detection to gold diagnostic standard for acute myocardial infarction and more

This paper reviews the history of the contribution of the laboratory medicine to clinical cardiology and discusses the most important steps in this field. Until 20 years ago, the clinical laboratory only placed at the cardiologist's disposal a few assays for the retrospective detection of cardiac tissue necrosis, such as enzymatic methods for creatine kinase and lactate dehydrogenase activities. However, in the latter part of the 20th century, highly sensitive and specific assays, such as cardiac troponins, as well as assays for markers of myocardial function, such as cardiac natriuretic peptides, rapidly changed the scenario of clinical management of patients with cardiac diseases, assigning to the laboratory a pivotal role in the overall diagnostic flow. This is witnessed by the recent incorporation of these markers into international guidelines and in the redefinition of myocardial infarction. For the foreseeable future, new serum markers of myocardial ischemic, i.e. reversible, injury or related to coronary plaque instability and disruption are expected.

Research translation: a new frontier for clinical laboratories

Translational research and translational medicine (referred to hereafter as translational research) are interchangeable terms that underline the pressing need to translate into practical benefits for those affected by disease the extensive investments divested by the private and public sectors in biomedical research. For people more directly involved in clinical practice (physicians, clinical laboratory professionals and patients), translational research responds to the need to accelerate the capture of benefits of research, closing the gap between what we know and what we practice. This basically means the transfer of diagnostic and therapeutic advances proven effective in large, well-conducted trials (and, therefore, evidence-based) to daily medical practice. Translational research should be regarded as a two-way road: bench to bedside, and bedside to bench. In particular, to make possible a more effective translation process, a new road map should be implemented through interaction and cooperation between basic researchers, clinicians, laboratory professionals and manufacturers. Some examples of recent developments in clinical laboratory testing, including markers of cardiovascular diseases, clinical proteomics and recombinant allergens, may explain the importance of careful evaluation of all variables that allow the introduction of such new insights into clinical practice to assure better clinical outcomes. The vital role of laboratory medicine in the delivery of safer and more effective healthcare requires more careful evaluation not only of the analytical characteristics, but also of any other variable that may affect the clinical usefulness and diagnostic performances of laboratory tests, thus allowing more accurate interpretation and utilization of laboratory information.

Clin Chem Lab Med 2006;44:1303–12.