Assessment of inter-individual variability in hamstring muscle recovery after a sport-specific sprint training in women and men

Background: Hamstring muscles are most affected by multiple sprint-based sports as a result of muscle strain during sprinting, leading to reduced performance and increased risk of injury. Therefore, the purpose of the study was to assess inter-individual variability in hamstrings recovery after a sport-specific repeated-sprint training (RST), through sprint-specific markers of muscle recovery and associated muscle damage biomarkers in women and men. Methods: Healthy females (n = 14) and males (n = 15) underwent 10 repeated 40-m sprints with a 3-min rest pause between each repetition. Force-generating capacity (FGC) by the 90° hip :20° knee test and range of motion Jurdan test, together with serum biomarkers [sarcomeric mitochondrial creatine kinase (sMtCK), oxidative stress, irisin] were tested at baseline and 24-, 48- and 72-h post-exercise through a repeated measures design. Participants were classified according to FGC loss into high responders (HR) and low responders (LR). Results: 21 individuals (10 females, 11 males) were classified as HR (FGC loss >20% and recovery >48 h), while 8 individuals (4 females, 4 males) were classified as LR. HR individuals showed unrecovered maximal voluntary isometric contraction (MVIC) torque until 72 h post-training (p = 0.003, np 2 = 0.170), whereas only HR males showed decreased range of motion (p = 0.026, np 2 = 0.116). HR individuals also showed increased sMtCK (p = 0.016, np 2 = 0.128), oxidative stress (p = 0.038, np 2 = 0.106) and irisin (p = 0.019, np 2 = 0.123). Conclusion: There is inter-individual variability in the muscular response to a sport-specific RST, identifiable by MVIC torque assessment. The findings support that the 90° hip :20° knee test is a powerful indirect test to screen hamstrings recovery in both women and men, in a cost-effective way. However, the Jurdan test might not be able to monitor hamstrings recovery in sportswomen after RST. Decreases in muscle capacity are linked to damage to muscle sarcolemma and mitochondria until 72 h post-exercise. Overall, 72 h will not be adequate time to restore hamstrings structure and function after a sport-specific RST in both female and male responders.

Myocardial Injury, Troponin Release and Cardiomyocyte Death in Brief Ischemia, Failure and Ventricular Remodeling

Troponin released from irreversibly injured myocytes is the gold standard biomarker for the rapid identification of an acute coronary syndrome. In acute myocardial infarction, necrotic cell death is characterized by sarcolemmal disruption in response to a critical level of energy depletion after more than 15-minutes of ischemia. While troponin I and T are highly specific for cardiomyocyte death, high-sensitivity assays have demonstrated that measurable circulating levels of troponin are present in the majority of normal subjects. In addition, transient as well as chronic elevations have been demonstrated in many disease states not clearly associated with myocardial ischemia. The latter observations have given rise to the clinical concept of myocardial injury. This review will summarize evidence supporting the notion that circulating troponin levels parallel the extent of myocyte apoptosis in normal ventricular remodeling and in pathophysiological conditions not associated with infarction or necrosis. It will review the evidence that myocyte apoptosis can be accelerated by both diastolic strain from elevated ventricular preload as well as systolic strain from dyskinesis after brief episodes of ischemia too short to cause a critical level of myocyte energy depletion. We then show how chronic, low rates of myocyte apoptosis from endogenous myocyte turnover, repetitive ischemia or repetitive elevations in LV diastolic pressure can lead to significant myocyte loss in the absence of neurohormonal stimulation. Finally, we posit that the differential response to strain-induced injury in heart failure may determine whether progressive myocyte loss and HFrEF or interstitial fibrosis and HFpEF become the heart failure phenotype.

Assessment of musculoskeletal pain, fatigue and grip strength in hospitalized patients with COVID-19

BACKGROUND

Although there are some retrospective studies to present musculoskeletal findings of the COVID-19, still the muscle strength and fatigue has not been studied in detail.

AIM

To reveal the symptoms of musculoskeletal system in COVID-19 patients, to evaluate myalgia, arthralgia and physical/mental fatigue, to assess handgrip muscle strength, and to examine the relations of these parameters with the severity and laboratory values of the disease.

DESIGN

This study was designed as a cross-sectional, single-center case series.

SETTING

This study took place from May 15, 2020, to June 30, 2020 at the Istanbul University-Cerrahpasa, Cerrahpasa Pandemia Services.

POPULATION

Hospitalized 150 adults with laboratory and radiological confirmation of severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) according to WHO interim guidance were included in the study.

METHODS

The disease severity 2007 IDSA/ATS guidelines for community acquired pneumonia was used. Myalgia severity was assessed by numerical rating scale (NRS). Visual analog scale and Chalder Fatigue Scale (CFS) were used for fatigue severity determination. Handgrip strength (HGS) was measured by Jamar hand dynamometer.

RESULTS

One hundred three patients (68.7%) were non-severe, and 47 patients (31.3%) were severe. The most common musculoskeletal symptom was fatigue (133 [85.3%]), followed by myalgia (102 [68.0%]), arthralgia (65 [43.3%]) and back pain (33 [22.0%]). Arthralgia, which was mostly notable at wrist (25 [16.7%]), ankle (24 [16.0%]) and knee (23 [15.3%]) joints, was significantly higher among the severe group. Severe myalgia was prevalent among myalgia sufferers regardless of COVID-19 severity. The physical fatigue severity score was significantly higher in severe cases, whereas this difference was not significant in mental fatigue score. Female patients with severe infection had "lower" grip strength, whereas grip strength among males did not differ significantly between non-severe and severe COVID-19 cases. Nevertheless, the mean values in both genders and in age decades were below the specified normative values. CRP, ferritin, and LDH levels were significantly higher in women with "lower" grip strength compared to the "normal" group.

CONCLUSIONS

Aside from other multisystemic symptoms, musculoskeletal symptoms are quite common in patients with COVID-19. Patients have severe ischemic myalgia regardless of disease activity. Although there is a muscle weakness in all patients, the loss of muscle function is more of a problem among women in connection with disease severity. Muscular involvement in Coronavirus disease is a triangle of myalgia, physical fatigue, and muscle weakness.

CLINICAL REHABILITATION IMPACT

Muscle involvement in COVID-19 patients does not mean only myalgia but also a combination of physical fatigue and muscle weakness, and this should be considered in planning the rehabilitation strategies of COVID-19 patients.

Post-Myocardial Infarction Ventricular Remodeling Biomarkers-The Key Link between Pathophysiology and Clinic

Studies in recent years have shown increased interest in developing new methods of evaluation, but also in limiting post infarction ventricular remodeling, hoping to improve ventricular function and the further evolution of the patient. This is the point where biomarkers have proven effective in early detection of remodeling phenomena. There are six main processes that promote the remodeling and each of them has specific biomarkers that can be used in predicting the evolution (myocardial necrosis, neurohormonal activation, inflammatory reaction, hypertrophy and fibrosis, apoptosis, mixed processes). Some of the biomarkers such as creatine kinase-myocardial band (CK-MB), troponin, and N-terminal-pro type B natriuretic peptide (NT-proBNP) were so convincing that they immediately found their place in the post infarction patient evaluation protocol. Others that are related to more complex processes such as inflammatory biomarkers, atheroma plaque destabilization biomarkers, and microRNA are still being studied, but the results so far are promising. This article aims to review the markers used so far, but also the existing data on new markers that could be considered, taking into consideration the most important studies that have been conducted so far.

Ischemia time impacts on respiratory chain functions and Ca2+-handling of cardiac subsarcolemmal mitochondria subjected to ischemia reperfusion injury

Background

Mitochondrial impairment can result from myocardial ischemia reperfusion injury (IR). Despite cardioplegic arrest, IR-associated cardiodepression is a major problem in heart surgery. We determined the effect of increasing ischemia time on the respiratory chain (RC) function, the inner membrane polarization and Ca²⁺ homeostasis of rat cardiac subsarcolemmal mitochondria (SSM).

Methods

Wistar rat hearts were divided into 4 groups of stop-flow induced warm global IR using a pressure-controlled Langendorff system: 0, 15, 30 and 40 min of ischemia with 30 min of reperfusion, respectively. Myocardial contractility was determined from left ventricular pressure records (dP/dt, dPmax) with an intraventricular balloon. Following reperfusion, SSM were isolated and analyzed regarding electron transport chain (ETC) coupling by polarography (Clark-Type electrode), membrane polarization (JC1 fluorescence) and Ca²⁺-handling in terms of Ca²⁺-induced swelling and Ca²⁺-uptake/release (Calcium Green-5 N® fluorescence).

Results

LV contractility and systolic pressure during reperfusion were impaired by increasing ischemic times. Ischemia reduced ETC oxygen consumption in IR40/30 compared to IR0/30 at complex I-V (8.1 ± 1.2 vs. 18.2 ± 2.0 nmol/min) and II-IV/V (16.4 ± 2.6/14.8 ± 2.3 vs. 2.3 ± 0.6 nmol/min) in state 3 respiration (p < 0.01). Relative membrane potential revealed a distinct hyperpolarization in IR30/30 and IR40/30 (171.5 ± 17.4% and 170.9 ± 13.5%) compared to IR0/30 (p < 0.01), wearing off swiftly after CCCP-induced uncoupling. Excess mitochondrial permeability transition pore (mPTP)-gated Ca²⁺-induced swelling was recorded in all groups and was most pronounced in IR40/30. Pyruvate addition for mPTP blocking strongly reduced SSM swelling in IR40/30 (relative AUC, ± pyruvate; IR0/30: 1.00 vs. 0.61, IR15/30: 1.68 vs. 1.00, IR30/30: 1.42 vs. 0.75, IR40/30: 1.97 vs. 0.85; p < 0.01). Ca²⁺-uptake remained unaffected by previous IR. Though Ca²⁺-release was delayed for ≥30 min of ischemia (p < 0.01), Ca²⁺ retention was highest in IR15/30 (RFU; IR0/30: 6.3 ± 3.6, IR 15/30 42.9 ± 5.0, IR30/30 15.9 ± 3.8, IR40/30 11.5 ± 6.6; p ≤ 0.01 for IR15/30 against all other groups).

Conclusions

Ischemia prolongation in IR injury gradually impaired SSM in terms of respiratory chain function and Ca²⁺-homeostasis. Membrane hyperpolarization appears to be responsible for impaired Ca²⁺-cycling and ETC function. Ischemia time should be considered an important factor influencing IR experimental data on subsarcolemmal mitochondria. Periods of warm global ischemia should be minimized during cardiac surgery to avoid excessive damage to SSMs.

Predictive Value of High-Sensitivity Troponin T for Systolic Dysfunction and Infarct Size (Six Months) After ST-Elevation Myocardial Infarction

The association of markers of myocardial injury and dysfunction with infarct size (IS) and ejection fraction (EF) are well documented. However, limited data are available on the newer high-sensitivity troponin assays and comparison with morphologic and functional assessment with cardiac magnetic resonance imaging. We aimed to examine the associations of high-sensitivity cardiac Troponin-T (hs-cTnT), creatine kinase MB iso-enzyme (CKMB), and N-terminal pro B-type Natriuretic Peptide (NT-proBNP) to IS and EF at 6 months. Blood samples from 119 ST-segment elevation myocardial infarction patients from the Rapid Endovascular Catheter Core Cooling Combined With Cold Saline solution as an Adjunct to Percutaneous Coronary Intervention for the Treatment of Acute Myocardial Infarction trial were collected at baseline, 6, 24, and 48 hours after admission. Cardiac magnetic resonance was performed at 4 ± 2 days and 6 months. The association of biomarker levels to IS and EF was tested with Pearson's correlation coefficients and linear regression models with bootstrap resampling. The correlation coefficient of biomarker to IS was (CKMB: r = 0.71); (NT-proBNP: r = 0.55); (hs-cTnT: r = 0.80); and for EF (CKMB: r = 0.57); (NT-proBNP: r = 0.48); and (peak hs-cTnT: r = 0.68). IS and EF at 4 ± 2 days had the strongest correlations with IS and EF at 6 months respectively (IS: r = 0.84) and (EF: r = 0.74). Receiver operating characteristic of peak hs-cTnT for predicting EF ≤40% at 6 months was 0.87 compared with 0.75 for early IS. Early EF was a negative predictor of late EF <40%, 1-area under curve = 0.93. In conclusion, high-sensitivity Troponin T is a rapid, cheap, generally available tool for accurate prediction of systolic dysfunction in patients 6 months after first-time ST-segment elevation myocardial infarction.

How is cardiac troponin released from injured myocardium?

Cardiac troponin I and cardiac troponin T are nowadays the criterion biomarkers for the laboratory diagnosis of acute myocardial infarction due to their very high sensitivities and specificities for myocardial injury. However, still many aspects of their degradation, tissue release and elimination from the human circulation are incompletely understood. Myocardial injury may be caused by a variety of different mechanisms, for example, myocardial ischaemia, inflammatory and immunological processes, trauma, drugs and toxins, and myocardial necrosis is preceded by a substantial reversible prelethal phase. Recent experimental data in a pig model of myocardial ischaemia demonstrated cardiac troponin release into the circulation from apoptotic cardiomyocytes as an alternative explanation for clinical situations with increased cardiac troponin without any other evidence for myocardial necrosis. However, the comparably lower sensitivities of all currently available imaging modalities, including cardiac magnetic resonance imaging for the detection of particularly non-focal myocardial necrosis in patients, has to be considered for cardiac troponin test result interpretation in clinical settings without any other evidence for myocardial necrosis apart from increased cardiac troponin concentrations as well.

Histological evidence for reversible cardiomyocyte changes and serum cardiac troponin T elevation after exercise in rats

This study characterized cardiac troponin T (cTnT) appearance and associated histological evidence of reversible or irreversible changes in myocardial ultrastructure, determined via electron microscopy, in rats undertaking isoproterenol (ISO) infusion or an endurance exercise challenge. Male rats were randomized into ISO and exercise groups. In ISO trials rats were killed 5 h (ISO‐5H) and 24 h (ISO‐REC19H) after a single ISO or saline injection (SAL‐5H; SAL‐REC19H). In the exercise trials rats were killed before, as a control (EXE‐CON), immediately after (EXE‐END5H) and 19 h after (EXE‐REC19H) a 5‐h bout of swimming with 5% body weight attached to their tail. Serum cTnT was quantified by electrochemiluminescence, and myocardial samples in ISO‐REC19H, EXE‐REC19H and SAL‐REC19H were harvested for assessment of specific mitochondrial injury scores using electron‐microscopy. cTnT was undetectable in all control animals (SAL‐5H/SAL‐REC19H and EXE‐CON). cTnT increased in all animals after ISO and exercise but the response was significantly higher (P < 0.05) at ISO‐5H (median [range]: 2.60 [1.76–6.18] μg · L⁻¹) than at EXE‐END5H (median [range]: 0.05 [0.02–0.14] μg · L⁻¹). cTnT returned to baseline at EXE‐REC19H, but had not completely recovered at ISO‐REC19H (median [range]: 0.17 [0.09–1.22] μg · L⁻¹). Mitochondrial “injury scores” were significantly higher (P < 0.05) in ISO‐REC19H compared to EXE‐REC19H and SAL‐REC19H, with no difference between EXE‐REC19H and SAL‐REC19H. Mitochondria from EXE‐REC19H appeared aggregated in nonlinear clusters in a small number of scans. These findings suggest that acute exercise‐induced appearance of cTnT in this animal model is only associated with reversible changes in cardiomyocyte structure.

Understanding different facets of cardiovascular diseases based on model systems to human studies: a proteomic and metabolomic perspective

Cardiovascular disease has remained as the largest cause of morbidity and mortality worldwide. From dissecting the disease aetiology to identifying prognostic markers for better management of the disease is still a challenge for researchers. In the post human genome sequencing era much of the thrust has been focussed towards application of advanced genomic tools along with evaluation of traditional risk factors. With the advancement of next generation proteomics and metabolomics approaches it has now become possible to understand the protein interaction network & metabolic rewiring which lead to the perturbations of the disease phenotype. Further, elucidating different post translational modifications using advanced mass spectrometry based methods have provided an impetus towards in depth understanding of the proteome. The past decade has observed a plethora of studies where proteomics has been applied successfully to identify potential prognostic and diagnostic markers as well as to understand the disease mechanisms for various types of cardiovascular diseases. In this review, we attempted to document relevant proteomics based studies that have been undertaken either to identify potential biomarkers or have elucidated newer mechanistic insights into understanding the patho-physiology of cardiovascular disease, primarily coronary artery disease, cardiomyopathy, and myocardial ischemia. We have also provided a perspective on the potential of proteomics in combating this deadly disease.

BIOLOGICAL SIGNIFICANCE

This review has catalogued recent studies on proteomics and metabolomics involved in understanding several cardiovascular diseases (CVDs). A holistic systems biology based approach, of which proteomics and metabolomics are two very important components, would help in delineating various pathways associated with complex disorders like CVD. This would ultimately provide better mechanistic understanding of the disease biology leading to development of prognostic biomarkers. This article is part of a Special Issue entitled: Proteomics in India.

The effects of heart and skeletal muscle inflammation and cardiomyopathy syndrome on creatine kinase and lactate dehydrogenase levels in Atlantic salmon (Salmo salar L.)

Heart and skeletal muscle inflammation (HSMI) and cardiomyopathy syndrome (CMS) are putative viral cardiac diseases of Atlantic salmon. This study examined the levels and correlated the serum enzymes creatine kinase (CK) and lactate dehydrogenase (LDH) to the histopathology of clinical outbreaks of HSMI and chronic CMS in farmed Atlantic salmon. A total of 75 fish from 3 different HSMI outbreaks, 30 chronic CMS fish, and 68 fish from 3 nondiseased fish groups were used as the study population (N = 173). Serum CK and LDH levels correlated significantly with the total inflammation and total necrosis scores for HSMI fish (P = 0.001). However, no correlation was identified for enzyme levels and histopathology scores for chronic CMS fish. The significantly increased CK and LDH levels and their positive correlations to histopathology differentiate HSMI from CMS clinically suggesting the potential use of enzymes for screening for HSMI is promising.

Enhancement of amlodipine cardioprotection by quercetin in ischaemia/reperfusion injury in rats

Objectives

To investigate the possible modification of the cardioprotective effect of amlodipine when co-administered with quercetin in myocardial ischaemia/reperfusion-induced functional, metabolic and cellular alterations in rats.

Methods

Oral doses of amlodipine (15 mg/kg) and quercetin (5 mg/kg), alone or in combination, were administered once daily for 1 week. Rats were then subjected to myocardial ischaemia/reperfusion (35min/10min). Heart rates and ventricular arrhythmias were recorded during ischaemia/reperfusion progress. At the end of reperfusion, activities of plasma creatine kinase (CK) and cardiac myeloperoxidase were determined. In addition, cardiac contents of lactate, ATP, thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH) and total nitrate/nitrite (NOx) were estimated. Finally, histological examination was performed to visualize the protective cellular effects of different pretreatments.

Key findings

Combined therapy provided significant improvement in the amlodipine effect toward preserving cardiac electrophysiologic functions, ATP and GSH contents as well as reducing the elevated plasma CK, cardiac TBARS and NOx contents.

Conclusion

Quercetin could add benefits to the cardioprotective effect of amlodipine against injury induced in the heart by ischaemia/reperfusion.

Periprocedural creatine kinase-MB elevations: long-term impact and clinical implications

Since the introduction of percutaneous transluminal coronary angioplasty (PTCA), percutaneous intervention with balloon catheters, stents, and atherectomy devices has become a widely accepted practice. The persistent complication of non-Q-wave myocardial infarction (MI), as evidenced by increased cardiac enzyme levels after intervention, has aroused only moderate concern because its incidence was perceived to be small and not clinically relevant. With more systematic assessments of cardiac enzymes--specifically, creatine kinase (CK) and its MB isoform--evidence has begun to clarify both the incidence and the prognosis of periprocedural non-Q-wave MI: It appears to occur nearly three times more often than is clinically evident across all device types (8 to 9% of all interventions) and is directly and continuously associated with adverse outcomes, including late death. Although directional and rotational atherectomy improve angiographic outcome compared with PTCA, periprocedural infarction occurs at least twice as often with these newer technologies; the incidence associated with stent placement is comparable to and possibly higher than that of PTCA. Factors that may cause elevated CK-MB levels include distal embolization, side branch occlusion, thrombus, and coronary spasm. Analyses of the major trials of platelet glycoprotein (GP) IIb/IIIa receptor inhibitors, a class of potent antiplatelet agents, show striking effectiveness of these drugs in reducing the incidence of "enzyme-only" or "silent" MI and in improving long-term clinical outcomes. The findings implicate platelet mediation in the occurrence of periprocedural infarction and suggest an important role for antiplatelet therapy, particularly GP IIb/IIIa receptor inhibition, in protecting patients undergoing percutaneous intervention.

Baseline serum levels of cardiac biomarkers in patients with stable coronary artery disease

Stable coronary artery disease (CAD) can cause repetitive reversible myocardial ischaemia, and it seems to be possible that reversibly injured myocardium releases small amounts of soluble cytoplasmic proteins. Hence, the aim was to evaluate the effect of stable CAD on baseline serum levels of cardiac biomarkers. We studied 68 consecutive outpatients referred for gated myocardial perfusion imaging. Before a treadmill exercise test, blood samples for measurement of creatine kinase (CK), CK-myocardial band (CK-MB) mass, myoglobin, aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) were collected. Normal perfusion patterns were detected in 29 (43%) patients (group 1) and perfusion defects were detected in 39 (57%) patients (group 2). Baseline serum levels of biomarkers except CK were significantly higher in group 2 (p=0.001). Stable CAD increases baseline levels of CK-MB mass, myoglobin, AST and LDH in the serum and this increase is related to the extent and severity of the perfusion defect and to some extent the ejection fraction of the left ventricle.

New potential uses for cardiac troponins

This review briefly synthesizes the molecular biology of troponin, which is currently the best biochemical marker for the detection of cardiac injury and, thus, acute myocardial infarction as well. Potential new uses for the marker based on these insights, with a specific interest in cardiac troponin fragments that potentially could be linked to distinct clinical conditions, are described. Some of the clinical problems clinicians are faced with including how to use the markers in renal failure and the difficulties associated with the heterogeneity of current troponin assays are also discussed. Finally, we present the possibility of specific cardiac troponin fragments resulting from modification or degradation, associated with distinct pathological processes, as new potential uses for this biomarker.

PIFITHRIN-α ATTENUATES P53-MEDIATED APOPTOSIS AND IMPROVES CARDIAC FUNCTION IN RESPONSE TO MYOCARDIAL ISCHEMIA/REPERFUSION IN AGED RATS

Ischemic cardiovascular disease is a common age-related disease. The p53-dependent cardiac myocyte apoptosis induced by myocardial ischemia/reperfusion (MI/R) is an important feature in the progression of ischemic heart disease. In the present studies, we hypothesized that inhibition of p53-dependent myocyte apoptosis may improve cardiac dysfunction in aged rats after MI/R. A dose (2.2 mg/kg, i.p.) of pifithrin-alpha (PFT), a p53 inhibitor, or saline was administered to 20-month-old male F344 rats, which were subjected to 30 min of myocardial ischemia by ligating the left main coronary artery, followed by release of the ligature and 4 h of reperfusion. Results of our experiments indicate that MI/R induced a significant decrease in cardiac output index (CI) and mean arterial blood pressure (MABP). Administration of PFT to aged rats 40 min before ischemia significantly improved CI and MABP during 3 to 4 h of reperfusion. The improvement of cardiac function was associated with a marked reduction in DNA fragmentation in the area at risk of the heart when compared with aged MI/R rats pretreated with saline. Interestingly, treatment with PFT 10 min after ischemia or 10 min after reperfusion had a similar protective effect on CI and MABP, but this effect did not reach statistical significance when compared with aged MI/R rats pretreated with saline. Treatment with PFT, however, did not influence plasma creatine kinase activity and the number of circulating leukocytes and infiltrated leukocytes in the area at risk of the heart. Moreover, results of Western blot show that pretreatment with PFT significantly attenuated the ratio of Bax to Bcl-2 in the area-at-risk tissue of the heart compared with that of rats pretreated with saline. Our results suggest that pretreatment with PFT significantly improved cardiac function. The mechanism of protective effect of PFT may involve the inhibition of p53 transcriptional function, thereby attenuating the p53/Bax-mediated myocyte apoptosis during the reperfusion period.

Serum chemical biomarkers of cardiac injury for nonclinical safety testing

There has been a substantial increase in the number and efficacy of laboratory biomarkers for the evaluation of human cardiac injury over the last decade. The advantages of these over traditional laboratory tests have encouraged adoption of comparable markers in nonclinical studies for cardiac injury assessment. Of particular interest are markers that are not only more sensitive and/or specific than traditional parameters for cardiac injury, but also those that may directly bridge human and laboratory animal safety testing. However, a majority of recently developed markers are quantified through antibody-based assays, and cross-reactivity with the comparable analyte in nonhuman samples is difficult to predict and often species-variable. The utility of these novel biomarkers thus, depends upon adequate assay validation with each laboratory species of interest. In contrast, traditional laboratory parameters of cardiac injury lack the properties of an ideal biomarker, but are well established and have an extensive database in nonclinical safety assessment. The current status and utility of both recently developed and traditional biomarkers of cardiac injury in nonclinical testing, and considerations for validation of novel biomarkers of cardiac injury are reviewed.

[Acute myocardial infarction and MRI: a comparison of infarct size by MRI and peak creatine kinase after a first episode]

AIM

To compare the assessment of infarct size using MRI and peak CK value.

POPULATION AND METHODS

16 patients presenting with a first MI and seriall measurement of CK underwent gadolinium-enhanced MRI.

RESULTS

A significant correlation was observed between both estimates of infarct size (r=0.56, p=0.0025). In addition, an inverse correlation was found between residual viability and peak CK (r=-0.51; p=0.043).

CONCLUSION

After a first episode of MI, infarct size estimate by MRI correlates with that determined by peak CK measurement.

Serum deoxyribonuclease I activity can be used as a sensitive marker for detection of transient myocardial ischaemia induced by percutaneous coronary intervention

AIMS

Cardiac markers such as troponin T (c-TnT) have proven unsuitable for the detection of early and transient myocardial ischaemia. We recently reported that abrupt elevation of serum deoxyribonuclease I (DNase I) activity in the early stage of acute myocardial infarction could be used as a diagnostic marker. To evaluate whether serum DNase I could be used as a marker of early myocardial ischaemia, we investigated alterations in its levels after transient ischaemia induced during percutaneous coronary intervention (PCI).

METHODS AND RESULTS

In 24 consecutive patients with stable angina undergoing elective PCI and 12 patients undergoing coronary angiography (CAG), serum samples were tested for DNase I, creatine kinase isoenzyme MB (CK-MB), and c-TnT before, soon after, and 3 and 12-24 h after completion of the procedures. Serum DNase I activity had risen significantly from baseline by 3 h after PCI in 21 of the 24 PCI patients. The mean per cent difference from baseline in serum DNase I activity 3 h after PCI was 35.9+/-37.5%. Even among the 16 PCI patients whose levels of CK-MB and c-TnT were within the normal range, 13 showed elevation of serum DNase I activity from baseline after PCI. In the CAG patient group, DNase I activity levels remained unchanged at all times after CAG.

CONCLUSION

Elevation of serum DNase I activity can be used as a sensitive marker for detection of transient myocardial ischaemia.

Attenuation of antioxidative capacity enhances reperfusion injury in aged rat myocardium after MI/R

Mortality due to ischemic cardiovascular diseases is significantly higher in elderly than in young adults. Myocardial ischemia-reperfusion (MI/R) can induce oxidative stress and an inflammatory response. We hypothesized that increased vulnerability of aged myocardium to reperfusion injury could be caused by decreased antioxidative capacity, rather than increased oxidant production, after MI/R. Aged (20-mo-old) and young (4-mo-old) male F344BN rats were subjected to 30 min of myocardial ischemia by ligation of the left main coronary artery followed by release of the ligature and 4 h of reperfusion. Four experimental groups were studied: young sham-operated rats, aged sham-operated rats, young rats subjected to MI/R, and aged rats subjected to MI/R. MI/R significantly increased infiltrated leukocyte number and myeloperoxidase (MPO) activity in perinecrotic areas of hearts of young rats compared with aged MI/R rats. These changes in infiltrated leukocyte number and MPO activity were associated with an increase in superoxide generation in perinecrotic areas from hearts of young rats compared with aged rats. Plasma levels of TNF-alpha and IL-1beta were significantly higher in young than in aged MI/R rats. However, plasma 8-hydroxy-2'-deoxyguanosine levels and creatine kinase activity were increased in aged compared with young MI/R rats. Increased reperfusion damage in aged rats was associated with a significant decrease in plasma ratio of GSH to GSSG. Our results suggest that enhanced ischemia-reperfusion injury in aged rat hearts may be related to reduced antioxidative capacity, rather than increased reactive oxygen species production. These findings contribute to a better understanding of effects of aging on oxidative stress and inflammatory responses of the heart after MI/R.

Exercise-induced increases in cardiac troponins and prothrombotic markers

Cardiac troponin I and T are potent tools for risk stratification and clinical decision-making for patients in the appropriate clinical setting of an acute coronary syndrome. Although these findings are relevant to patients with a typical clinical presentation, caution should be exercised in generalizing the results to troponin-positive athletes with a low clinical suspicion of coronary artery disease. This review addresses the clinical relevance of increased troponin levels induced by strenuous exercise. The imprecision and lack of standardization of currently available troponin assays merit caution with the application of these findings. In addition, it may well be that if reparative processes are present and/or the release is not due to irreversible injury that increases in troponins after vigorous exercise are normal and should not be expected to be of pathophysiological significance. Due to this potential for misclassification, the crux of appropriate interpretation of troponin testing is careful consideration of the corresponding clinical scenario. Troponin-positive patients often have complex coronary lesion morphology with intracoronary thrombus and understandably derive particular benefit from platelet glycoprotein GpIIb/IIa inhibitors as well as low molecular weight heparins. Studies on exercise-induced activation of blood coagulation have produced conflicting results. At present, there is no clear evidence that a hemostatic imbalance may trigger acute cardiac events after strenuous exercise. In contrast to troponin-positive patients, it may thus be premature and even dangerous to recommend pharmacologic intervention (low molecular weight heparins) to (troponin-positive) endurance athletes even when exercising during high-altitude exposure.

Prospective analysis of creatine kinase muscle-brain fraction and comparison with troponin T to predict cardiac risk and benefit of an invasive strategy in patients with non-ST-elevation acute coronary syndromes

OBJECTIVE

We sought to determine whether elevation of plasma creatine kinase muscle-brain fraction (CK-MB) would be useful to triage patients with acute coronary syndromes (ACS) to early angiography/revascularization.

BACKGROUND

It is unknown whether the measurement of CK-MB is effective for triage to an aggressive management strategy.

METHOD

Patients in the Treat Angina With Aggrastat and Determine Cost of Therapy With an Invasive or Conservative Strategy (TACTICS-TIMI) 18 study received aspirin, heparin, and tirofiban for treatment of ACS, were randomized to an invasive or a conservative strategy (angiography/revascularization between 4 and 48 h), and were followed up for a composite end point of death, myocardial infarction, or rehospitalization for ACS. Of 2,220 patients, CK-MB was elevated in 826 (37%). Of the patients with negative CK-MB, troponin T was elevated in 361 (31.2%). Event rates at 30 and 180 days were twice as high in patients with elevated CK-MB than in patients without elevated CK-MB. Both groups had similar benefit from an invasive strategy; there was no evidence of interaction between CK-MB elevation and strategy on the composite end point at 30 or 180 days. When patients were stratified according to both CK-MB and troponin status, there was evidence of a benefit in the invasive strategy among patients who were CK-negative but troponin-positive (odds ratios [95% confidence interval]: 0.13 [0.04 to 0.39] at 30 days and 0.29 [0.16 to 0.52] at 180 days).

CONCLUSION

Patients with minimal amounts of recent onset myonecrosis but elevated risk as indicated by CK-MB and troponin, respectively, benefit most from invasive management. Determination of troponin levels yielded significant information regarding triage to an invasive strategy, particularly in CK-MB-negative patients.

Thresholds for the electrocardiographic change range of biochemical markers of acute myocardial infarction (GUSTO-IIa data)

The definition of acute myocardial infarction (AMI) is increasingly dependent on levels of biochemical markers, including troponin. We aimed to determine the levels of biochemical markers associated with definite evolutionary electrocardiographic (ECG) changes in patients with ST-segment elevation myocardial infarction. By examining the database of 855 patients from the troponin substudy of GUSTO-IIa, we selected patients with ST-segment elevation at baseline, evidence of evolution of the QRS, T, and ST-segment waveforms on the predischarge electrocardiogram, and 3 measurements of > or =1 of the following: creatine kinase (CK)-MB, troponin T, or troponin I. We identified 222 patients with evolutionary ECG changes. The median QRS score for this population was 5 points; the fifth percentile was 1. For patients with 3 CK-MB measurements, the fifth percentile as a multiple of the upper limit of normal was 2.1 (upper limit of normal 7.0 ng/ml). For patients with troponin T measurements, the fifth percentile as a multiple of the upper limit of normal was 11.0 (upper limit of normal 0.1 ng/ml). For patients with troponin I measurements, the fifth percentile as a multiple of the upper limit of normal was 3.8 (upper limit of normal 1.5 ng/ml). This study revealed that 95% of the patients with definite ECG evidence of AMI had a more than twofold increase in CK-MB and more than a 3- to 11-fold increase in troponin.

Development of a simple whole blood panel test for detection of human heart-type fatty acid-binding protein

OBJECTIVE

For the diagnosis of acute myocardial infarction (AMI), we have developed a rapid and simple whole blood panel test for the detection of human heart-type fatty acid-binding protein (H-FABP) using one-step immunochromatography.

METHODS AND RESULTS

We have developed a whole blood panel test for rapid detection of human H-FABP using a one-step immunochromatography technique. The result of this panel test was not affected by the other contents of the blood such as bilirubin, hemoglobin and others. Furthermore, no cross-reactivity of the antibodies was found with other cardiac markers or other tissue-type FABPs. The result of this panel test was similar to the diagnostic cut-off value, 6.2 ng of H-FABP per mL of serum which was evaluated by the enzyme-linked immunosorbent assay (ELISA).

CONCLUSION

We have developed a simple one-step immunochromatography technique to detect H-FABP in whole blood sample. Further studies are required to identify the value of this point-of-care testing (POCT) as a diagnostic marker for AMI.

Reduced albumin-cobalt binding with transient myocardial ischemia after elective percutaneous transluminal coronary angioplasty: a preliminary comparison to creatine kinase-MB, myoglobin, and troponin I

BACKGROUND

Previous reports suggest that ischemic conditions rapidly reduce the capacity of human albumin to bind exogenous cobalt. A new assay based on human albumin-cobalt binding (ACB) may help detect early myocardial ischemia. We investigated altered ACB during the first 24 hours after transient ischemia induced during elective percutaneous transluminal coronary angioplasty (PTCA). We then compared ACB assay results with creatine kinase isoenzyme (CK-MB), myoglobin, and cardiac troponin I (cTn-I) values after PTCA.

METHODS AND RESULTS

In 41 patients undergoing elective PTCA, plasma samples were tested for the ACB assay, CK-MB, myoglobin, and cTn-I before, immediately after, and 6 and 24 hours after PTCA. Thirteen additional patients served as a control group with albumin-cobalt assays performed before and after diagnostic coronary catheterization without angioplasty. ACB assay results demonstrated a significant mean percent difference (10.1%) immediately after PTCA compared with baseline (P < .000001) and returned to baseline by 6 hours after PTCA. ACB assay differences immediately after PTCA were significantly greater than in the control group (10.1% vs -0.9%, P < .001). Mean CK-MB, myoglobin, and cTn-I values were not elevated above baseline immediately after PTCA but were significantly elevated above baseline 6 and 24 hours after PTCA.

CONCLUSIONS

These preliminary results suggest that human albumin undergoes a significant reduction in its capacity to bind exogenous cobalt soon after transient coronary occlusion during human PTCA and before significant elevations of CK-MB, myoglobin, or cTn-I. Further confirmatory investigations are warranted to determine if the ACB assay is a useful diagnostic test for early myocardial ischemia.

Normal CK, elevated MB predicts complications in acute coronary syndromes

The implications of an elevated Creatine kinase (CK)-MB isoenzyme (MB) in suspected acute coronary syndromes, with a normal total CK, is not well established. Despite many guidelines on managing patients with acute coronary ischemia, none indicates strategies for patients with elevated MB and with a normal CK. The outcome consequence of this result is not firmly established. Our objective was to prospectively evaluate outcomes in patients with suspected acute coronary syndromes, normal initial total CK, and increased MB. All Emergency Department patients with suspected acute coronary syndromes and creatinine < 2.0 mg/dL were eligible for study entry. Serial CK and MB fractions were measured on arrival in the Emergency Department, then 8 and 16 h postpresentation. A composite outcome of death, Q-wave myocardial infarction, or revascularization was defined at the index visit and 6 months later. Outcomes were determined by blinded record review and by telephone contact. In the 698 patients entered, the acute composite outcome rate was 25% (175) and 6.3% (44) at 6 months. Acute and 6 month adverse outcome rates were statistically the same for all patients with an elevated MB fraction, regardless of the total CK level. An elevated MB conferred a higher event rate than did a normal MB. We conclude that the adverse event rate for patients with suspected acute coronary syndromes and an elevated MB is the same whether or not the total CK is elevated. These patients should be considered as having had an acute coronary syndrome.

Creatine and creatinine metabolism

The goal of this review is to present a comprehensive survey of the many intriguing facets of creatine (Cr) and creatinine metabolism, encompassing the pathways and regulation of Cr biosynthesis and degradation, species and tissue distribution of the enzymes and metabolites involved, and of the inherent implications for physiology and human pathology. Very recently, a series of new discoveries have been made that are bound to have distinguished implications for bioenergetics, physiology, human pathology, and clinical diagnosis and that suggest that deregulation of the creatine kinase (CK) system is associated with a variety of diseases. Disturbances of the CK system have been observed in muscle, brain, cardiac, and renal diseases as well as in cancer. On the other hand, Cr and Cr analogs such as cyclocreatine were found to have antitumor, antiviral, and antidiabetic effects and to protect tissues from hypoxic, ischemic, neurodegenerative, or muscle damage. Oral Cr ingestion is used in sports as an ergogenic aid, and some data suggest that Cr and creatinine may be precursors of food mutagens and uremic toxins. These findings are discussed in depth, the interrelationships are outlined, and all is put into a broader context to provide a more detailed understanding of the biological functions of Cr and of the CK system.

Release of cardiac troponin in acute coronary syndromes: ischemia or necrosis?

Analysis of cardiac troponin T and I have been shown to be effective in detecting minor myocardial injury in cardiac patients who present with acute coronary syndromes (ACS). Determination of minor myocardial injury is significant, as these patients have a higher short-term morbidity and mortality than other unstable angina patients with normal concentrations for these markers. In this report, two theories are given as to why cardiac troponin is superior to other markers such as CK-MB for risk stratification. The 'low cut-off concentration model' is based on the fact that troponin is not increased in patients with skeletal muscle disease or injury, resulting in low baseline concentrations of the cardiac isoforms in the absence of active cardiac disease. This enables the use of low decision limits. Troponin also has a higher myocardial tissue content relative to CK-MB, thereby also increasing its clinical sensitivity to irreversible injury. In the 'reversible ischemia model', cytoplasmic free troponin T and I leak across the membrane of myocytes as the result of reduced coronary blood flow. Jeopardized myocardial tissue can recover with acute recanalization. Support for this model comes from clinical observations and animal studies.

Diagnostic marker cooperative study for the diagnosis of myocardial infarction

BACKGROUND

Millions of patients present annually with chest pain, but only 10% to 15% have myocardial infarction. Lack of diagnostic sensitivity and specificity of clinical and conventional markers prevents or delays treatment and leads to unnecessary costly admissions. Comparative data are lacking on the new markers, yet using all of them is inappropriate and expensive.

METHODS AND RESULTS

The Diagnostic Marker Cooperative Study was a prospective, multicenter, double-blind study with consecutive enrollment of patients with chest pain presenting to the emergency department. Diagnostic sensitivity and specificity and frequency of increase in patients with unstable angina were determined for creatine kinase-MB (CK-MB) subforms, myoglobin, total CK-MB (activity and mass), and troponin T and I on the basis of frequent serial sampling for </=24 hours. Of 955 patients with chest pain, 119 (12.5%) had infarction identified by use of CK-MB mass, and 203 (21%) had unstable angina. CK-MB subforms were most sensitive and specific (91% and 89%) within 6 hours of onset, followed by myoglobin (78% and 89%). For late diagnosis, total CK-MB activity (derived from subforms) was the most sensitive and specific (96% and 98%) at 10 hours from onset, followed by troponin I (96% and 93%), but not until 18 hours, and troponin T (87% and 93% at 10 hours). In unstable angina, CK-MB subforms were increased in 29.5%, myoglobin in 23.7%, troponin I in 19.7%, and troponin T in 14.8%. All markers were increased in 99 patients. With each marker as the diagnostic standard, CK-MB subforms and myoglobin remained the most sensitive for early diagnosis.

CONCLUSIONS

The CK-MB subform assay alone or in combination with a troponin reliably triages patients with chest pain and should lead to improved therapy and reduced cost.

Biochemical advances in detection of the acute coronary syndromes: Implications for therapeutic decisions

In this paper, I have attempted to place the evolving insights of the pathophysiology of coronary atherosclerosis in the context of the conventional perspective of clinical medicine. We strive to prevent death and to relieve suffering. Our clinical tools are critical but limited. Troponin, a biomarker of unprecedented organ specificity, in the context of the appropriate setting of new chest pain (or its equivalent syndrome), is an extraordinary aid to clinical diagnosis. Highly effective therapy is evolving which reduces loss of myocardium, undoubtedly reducing not only acute death but progression to congestive heart failure. Even if the newer therapies of the GpIIb/IIIa platelet antagonists and antithrombins are not yet widely employed, or may not be available to some physicians, the convincing demonstration of myocardial injury by troponin presents objective evidence to both the patient and the attending physician that serious compliance with a program of risk reduction must be urgently considered. Hoeg has described the mosaic of risk factors beyond the conventional and often ignored basic ones (JAMA, 1997, 277, 1387-1390). He provides thoughtful hope and encouragement for both patient and physician to do more in prevention of the subsequent predictable progression. We should look on a troponin positive vague unstable angina event as similar to a tremor which preceeds a subsequent earthquake. Although the mass of myocardium lost in such an episode may be small, it is a warning of the major acute myocardial infarction which can be predicted to follow at a later time if the course of the individual patient is not altered. Troponin is the objective evidence.

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.