The risk factors of postoperative hypoxemia in patients with Stanford type A acute aortic dissection

Hypoxemia is one of the most common complications in patients after Stanford type A acute aortic dissection surgery. The aim of this study was to investigate the association of circulating ANG II level with postoperative hypoxemia and to identify the risk factors for postoperative hypoxemia in Stanford type A acute aortic dissection patients. In this study, 88 patients who underwent Stanford type A acute aortic dissection surgery were enrolled. Postoperative hypoxemia is defined by the oxygenation index (OI). Perioperative clinical data were collected and the serum ANG II and sACE2 levels were measured. The differences in the basic characteristics, intraoperative details, biochemical parameters, laboratory test data and clinical outcomes were compared between the hypoxemia group and the non-hypoxemia group by univariate analysis. Multivariate logistic regression analysis was performed on the variables with P < .1 in univariate analysis or that were considered clinically important to identify risk factors for postoperative hypoxemia. Twenty-five patients (28.4%) were considered to have postoperative hypoxemia (OI ≤ 200 mm Hg). The ANG II concentration remained a risk factor associated with postoperative hypoxemia [OR = 1.018, 95% CI (1.003-1.034), P = .022]. The other risk factors remaining in the logistic regression model were BMI [OR = 1.417, 95% CI (1.159-1.733), P = .001] and cTnI [OR = 1.003, 95% CI (1.000-1.005), P = .032]. Elevated levels of ANG II, BMI and cTnI are risk factors for postoperative hypoxemia in patients with Stanford type A acute aortic dissection.

A Comparative Study of Ischemia-Modified Albumin: A Promising Biomarker for Early Detection of Acute Coronary Syndrome (ACS)

Introduction The second most common cause of emergency department (ED) visits is chest pain and discomfort. Timely identification or threat stratification is crucial for identifying high-risk individuals who benefit from sophisticated diagnostic investigations (including cardiac biomarkers) and early relevant therapies. We aimed to assess the levels of ischemia-modified albumin (IMA) and also to study its sensitivity and specificity in comparison with cardiac troponin T/troponin I and electrocardiogram (ECG) (alone and in combination) in the diagnosis of acute myocardial infarction. Methods Adults (either gender) presented at the ED of a tertiary care centre with classical chest pain suggestive of angina pectoris or angina-like chest pain and ECG changes suggestive of ACS, ST-elevation myocardial infarction (STEMI), non-ST elevation myocardial MI (NSTEMI), and unstable angina, within three hours of onset were enrolled. Demographic and clinical information was recorded. ECG, haematological investigations like complete blood count, blood sugar level, lipid profile, IMA, troponin I, and creatinine kinase-MB (CK-MB), and radiological investigations like 2D-echocardiography (2D-ECHO) and coronary angiography were performed. Results A total of 100 subjects were enrolled in the study out of which 50 were cases and 50 were controls. Cases were older as compared to controls (mean age 60.5 versus 46.0 years). Of the 50 cases, 33 (66%) were males. There were equal numbers of males (33 each) and females (17 each) subjects in both the groups. Typical chest pain, risk factors, and history of coronary artery disease (CAD) were higher in cases. ECG diagnosis revealed the presence of STEMI (52%) and coronary angiography revealed the presence of double vessel CAD (60%) in cases. Among controls, gastroesophageal reflux disorder was the most common cause of chest pain followed by costochondritis and pneumonia. Glucose (fasting and postprandial), all lipid profile parameters (except high-density lipoprotein) and IMA values were significantly higher in cases as compared to controls. A combination of ECG+IMA has the highest sensitivity (90%) with 79% PPV in the diagnosis of ACS within three hours of the onset of chest pain, and ECG+IMA+2D-ECHO had similar results. However, ECG is equally sensitive. IMA alone has 64% sensitivity with 82% diagnostic accuracy which was higher than other biomarkers (CK-MB, cardiac troponin I). Conclusions As found in our study, among the biomarkers used, the diagnostic accuracy of IMA was the highest and better than that of cardiac troponin I and CK-MB. Although ECG is the preferred diagnostic tool for diagnosing ACS (STEMI, NSTEMI, and unstable angina) in patients presenting within three hours of the onset of chest pain, a confirmation can be done with the help of other diagnostic tests and investigations like serum IMA levels and further treatment can be initiated.

Prognostic Significance of Electrocardiography, Echocardiography, and Troponin in Patients Admitted With Non-ST Elevation Myocardial Infarction

BACKGROUND

Non-ST segment elevation myocardial infarction (NSTEMI) is a clinical condition characterized by typical symptoms of myocardial ischemia along with electrocardiographic changes and a positive value of troponin. After presentation in the emergency department, these patients have their troponin I value and electrocardiography done. Echocardiography (echo) should also be performed on these patients. This study was conducted to determine the prognostic significance of ECG, echo, and troponin.

METHODS

This observational study was conducted at a tertiary care cardiac hospital on 221 diagnosed patients of NSTEMI. Electrocardiography was performed to see any particular resting ECG findings and the peak values of cardiospecific troponin were analyzed for associations with major adverse events after a six-month period of follow-up. On echo, the left ventricular ejection fraction was divided into two categories: left ventricular ejection fraction (LVEF) <40% and LVEF >40%.

RESULTS

 The most frequent finding on presenting ECG was ST depression in anterior leads (V1-V6) in 27.6%. Median troponin I at presentation was 3.2 ng/dl and the median ejection fraction was 45%. The overall all-cause mortality rate at six months was observed to be 8.6%; re-infarction in 5%, re-hospitalization in 16.3%, and heart failure in 25.3% were observed. However, mortality was higher for patients with baseline ECG findings of A-fib, generalized ST-depression, poor R-wave progression, Wellens sign, and T-wave inversion in inferior; the mortality rate was also relatively higher among patients with poor LVEF (<30%).

CONCLUSION

ECG and echo were prognostically significant and with the combined incidence of adverse events. However, troponin lacks prognostic significance at six months.

Acute Cholecystitis Leading to Elevated High-Sensitive Cardiac Troponin I in a Young Female Without Any Cardiac Ailment: A Rare Case Presentation

Cardiac troponin I (cTnI) is regarded as a gold standard investigation for the diagnosis of acute myocardial infarction (AMI). However, cTnI may be elevated in certain non-AMI cardiac conditions and even in certain noncardiac conditions. We report a case of a young female presenting with symptoms suggestive of acute cholecystitis with elevated high-sensitive cardiac troponin I (hs-cTnI). The patient developed acute chest pain during the hospital stay. On evaluation, quantitative assay for hs-cTnI was found to be elevated; however, other markers of cardiac damage such as creatinine kinase-MB (CK-MB), qualitative cTnI by card test, and even echocardiogram (ECG) were found to be negative. As the patient was a young female with no significant history of coronary diseases, the spurious elevation of hs-TnI due to a noncardiac ailment was suspected. The patient was managed with minimal cardiological management till AMI was excluded. The hs-cTnI levels returned to normal post-cholecystectomy. A patient presenting with symptoms suggestive of cholecystitis and elevated hs-cTnI must be carefully evaluated before resorting to any invasive management for AMI. In most cases, hs-cTnI will return to normal post-cholecystectomy.

The Importance of Measuring Troponin in Chronic Obstructive Pulmonary Disease Exacerbations: A Systematic Review

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of death worldwide. Many patients with acute exacerbations need intensive care. There are many cardiovascular risk factors and comorbid conditions linked with COPD. Troponin elevation is used for the diagnosis of myocardial infarction. However, it is commonly elevated in patients with COPD. This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed and Scopus were searched for relevant articles. A total of 383 papers were identified. Out of the 383 papers, only 30 papers remained for final synthesis after removing duplicates, screening for relevant articles, and assessing eligibility criteria. After the quality appraisal, 11 papers were chosen for inclusion in this study. COPD is characterized by obstruction and inflammation of the airways. It is caused mainly by smoking, by causing harmful changes in the structure of the airways. It usually presents with dyspnea, cough, and/or production of sputum. Troponins are regulatory proteins found in the myocardium and skeletal muscles. The cause of its elevation in COPD and acute exacerbated chronic obstructive pulmonary disease (AECOPD) remains unclear. However, several reasons and factors have been suggested. The most intriguing fact is that high troponin in COPD, especially in exacerbations, has been linked in many articles to a higher risk of death. Furthermore, it could serve as a tool for better assessment and management of COPD patients. We found that troponin predicts death and poor outcomes in COPD and AECOPD. The exact mechanism of its elevations is not clear. We believe it can be a valuable tool for clinicians in better managing COPD and assessing the severity of the exacerbations.

Cardiac Troponin I Levels in Hospitalized COVID-19 Patients as a Predictor of Severity and Outcome: A Retrospective Cohort Study

Introduction

The COVID-19 (coronavirus disease) has affected millions of people, wreaking havoc worldwide. World Health Organization (WHO) labelled this disease as a serious threat to public health since its rapid spread from Wuhan, China. The respiratory manifestations of COVID-19 are common, but myocardium involvement causing myocardial injury and rise in cardiac markers is much less discussed.

Materials and methods

We conducted this retrospective cohort study from 1st April 2020 to 1st October 2020. Data was collected from the Hospital Management and Information System (HMIS) based on inclusion criteria. We used the Cox proportional hazard regression model for survival analysis, estimated the probability curves of survival using the Kaplan-Meier method, and contrasted it with the log-rank test.

Results

Among the 466 patients, 280 (69%) were male; the rest were female. The majority were both hypertensive and diabetic, and one-third had a myocardial injury on arrival. The most frequent symptoms in more than half of the patients (51.90%) included a combination of fever, dry cough, and shortness of breath. Out of 466 patients, 266 patients were discharged, and 200 did not survive. In our study, 168 (36.05%) patients had a cardiac injury; among them, 38 (22.61%) were in the discharge group, and the remaining 130 (77.39%) patients were in the nonsurvivor group. Our study results showed that the mortality rate was higher in patients with high cardiac troponin I (cTnI) levels (hazard ratio [HR] 3.61) on admission.

Conclusion

Our result concluded that measuring cTnI levels on presentation could help predict the severity and outcome in COVID-19 patients. It will allow physicians to triage patients and decrease mortality.

Indices of left ventricular voltage on electrocardiogram are closely associated with serum cardiac troponin I levels in normotensive Japanese individuals

The high-sensitivity cardiac troponin I (hs-cTnI) in serum can increase due to an increase in left ventricular (LV) overload in individuals with hypertension. Since LV voltage on an electrocardiogram (ECG) reflects LV load, it is possible that LV voltage is closely associated with hs-cTnI in individuals without hypertension. This study investigated the association between LV voltage indices and serum hs-cTnI levels in normotensive Japanese individuals.Subjects who visited the Enshu Hospital for a health check-up were screened for their eligibility. Subjects with renal dysfunction, cancer, active inflammatory disease, or a history of cardiovascular events were excluded, as were subjects with obvious ST segment or T wave abnormality, Wolff-Parkinson-White syndrome, pacemaker implantation, or frequent arrhythmia in the ECG. Exclusion of individuals with hypertension left 803 subjects (54.8 ± 11.3 years) for final inclusion. The R wave voltage in lead V5 (RV5 voltage), the Sokolow-Lyon voltage (a sum of the QRS wave (a complex wave consists of Q, R, and S wave) of the S wave voltage in lead V1 and the R wave voltage in lead V5), and the Cornell product (a product of QRS duration and QRS voltage) were evaluated by ECG as LV voltage indices. Laboratory measurements included serum hs-cTnI levels. Possible associations between indices of LV voltage on ECG and serum hs-cTnI levels were cross-sectionally investigated in the normotensive subjects.The median values [interquartile range] of hs-cTnI and BNP were and 2.1 [1.4-3.0] and 13.8 [7.7-24.9] pg/mL, respectively. Multivariate regression analysis identified that the levels of hs-cTnI, but not BNP, were significantly associated with RV5 voltage (β 0.090, P = .0087), Sokolow-Lyon voltage (β 0.112, P = .0009), and Cornell product (β 0.101, P = .039) after adjustment for possible confounding factors. Moreover, the RV5 voltage, Sokolow-Lyon voltage, and Cornell product were significantly associated with the hs-cTnI levels after adjustment for possible confounding factors including ECG findings (β 0.109, P = .0075; β 0.125, P = .0010; and β 0.096, P = .0116, respectively).Indices of LV voltage in ECG had close associations with serum hs-cTnI levels in normotensive subjects. These findings support that the ECG findings of LV voltage have significant associations with slight myocardial micro-damage even in normotensive subjects.

Free fatty acids as a marker for predicting periprocedural myocardial injury after coronary intervention

BACKGROUND

Previous studies have revealed that plasma levels of free fatty acids (FFAs) are related to cardiovascular risk. However, whether FFAs could predict periprocedural myocardial injury (PMI) following percutaneous coronary intervention (PCI) in patients with stable coronary artery disease (CAD) remains unclear.

PURPOSE

This study aimed to investigate the relationship of FFAs to PMI in untreated patients with CAD who underwent PCI.

METHODS

A total of 374 consecutive patients with CAD without lipid-lowering treatment on admission and with normal preprocedural cardiac troponin I (cTnI) levels who underwent PCI were prospectively enrolled. The baseline characteristics were collected and PMI was evaluated by cTnI analysis within 24 hours. The relation of preprocedural FFA levels to peak cTnI values after PCI was examined.

RESULTS

Preprocedural FFAs were positively correlated with peak cTnI values after PCI in both simple regression model (β=0.119, p=0.021) and multiple regression model (β=0.198, p=0.001). Patients with higher FFA levels had higher postprocedural cTnI levels compared with those with normal FFA levels (0.27±0.68 ng/mL vs 0.66±0.31 ng/mL, p=0.014). In the multivariable model, preprocedural FFA levels were associated with an increased risk of postprocedural cTnI elevation above 1× upper limit of normal (ULN, OR: 1.185, 95% CI 0.997 to 1.223, p=0.019) up to 10× ULN (OR: 1.132, 95% CI 1.005 to 1.192, p=0.003) .

CONCLUSIONS

The present study first suggested that elevated FFA levels were associated with an increased risk of PMI in untreated patients with CAD. Further study with large sample size may be needed to confirm our findings.

Comparison of pentraxin-3 and ischemia-modified albumin with troponin in early diagnosis of acute coronary syndrome

INTRODUCTION

In this study, our aim was to evaluate clinical utilities of Pentraxin 3 (PTX3) and Ischemia-modified Albumin (IMA) in diagnosis of acute coronary syndrome (ACS) and compare these two biomarkers with a conventional diagnostic marker, cardiac troponin I (cTnI).

MATERIALS AND METHODS

Sixty adult patients with ACS diagnosis were involved into this prospective study. Additionally, 20 healthy subjects were determined as control group (Group IV). Patients were divided into 3 groups as follows: Patients with Acute Myocardial Infarction (STEMI Group, n=20, Group I), patients without ST elevation but with elevated cTnI levels (NSTEMI Group, n=20, Group II), and patients with unstable angina pectoris (USAP Group, n=20, Group III). Blood measurements were obtained for each marker at admission and in the 4th hour.

RESULTS

Troponin level was significantly different between groups I and II at both admission and in the 4th hour. Additionally, PTX 3 level was significantly different at admission and 4th hour between groups II and III.

CONCLUSION

This study revealed that cTnI is the most sensitive test in ACS diagnosis at the admission to Emergency Department. Our results also revealed that PTX 3 may be a useful diagnostic tool for ACS at admission, however, IMA alone cannot be used for diagnosis of ACS. Similarly, in the 4th hour, cTnI was found to be the most useful marker in ACS diagnosis, however, PTX 3 and IMA were found to be inadequate for diagnosis of ACS (Tab. 3, Ref. 19).

Evidence of direct cardiac damage following high-intensity exercise in chronic energy restriction: A case report and literature review

RATIONALE

Following prolonged endurance events such as marathons, elevated levels of cardiospecific biomarkers are commonly reported. Although transiently raised levels are generally not considered to indicate clinical myocardial damage, comprehension of this phenomenon remains incomplete. The popularity of high-intensity interval training highlights a paucity of research measuring cardiac biomarker response to this type of exercise. This a posteriori case report discusses the elevation of cardiac troponins (cTn) associated with short interval, high-intensity exercise.

PATIENT CONCERNS

In this case report, an apparently healthy 29-year-old recreationally active female presented clinically raised cardiac troponin I (cTnI) levels (>0.04 ng/mL), after performing high-intensity cycle ergometer sprints. As creatine kinase (CK) is expressed by multiple organs (e.g., skeletal muscle, brain, and myocardium), cTnI assays were performed to determine any changes in total serum CK levels not originating from skeletal muscle damage.

DIAGNOSIS

A posteriori the individual's daily energy expenditure indicated chronically low-energy availability. Psychometric testing suggested that the individual scored positive for disordered eating, highly for fatigue levels, and low in mental health components.

OUTCOMES

The current case report provides novel evidence of elevated cTnI occurring as a result of performing short duration, high intensity, cycle ergometer exercise in an individual with self-reported chronically depleted energy balance. A schematic to identify potentially "at risk" individuals is presented.

LESSONS

Considering this as a case report, results cannot be generalized; however, the main findings suggest that individuals who habitually restrict their calorie intake below their bodies' daily energy requirements, may have elevated biomarkers of exercise induced myocardial stress from performing high-intensity exercise.

Establishment of a reference interval for high-sensitivity cardiac troponin I in healthy adults from the Sichuan area

High-sensitivity cardiac troponin I (hs-cTnI) has been used in the diagnosis and risk stratification of acute myocardial infarction. However, there is no common consensus on an hs-cTnI reference interval for the Chinese population. The aim of this study was to describe the distribution of hs-TnI and establish the 99th percentile reference interval for hs-cTnI in healthy adults from the Sichuan area.Serum specimens were collected from 1485 healthy adults (731 men and 754 women ranging in age from 18 to 85 years) in Sichuan Provincial People's Hospital. All specimens were divided into 4 groups according to age distribution: 18 to 35 years, 36 to 50 years, 51 to 65 years, and ≥66 years. Specimens were further divided into younger/middle and older-aged groups based on a cut-off age of 50 years. The serum hs-cTnI concentration was determined using the Abbott ARCHITECT STAT hs-cTnI assay.The serum hs-cTnI concentration increased with age (P < 0.05). The 99th percentiles of hsTnI were 28.0 pg/mL among the whole population, 31.1 pg/mL among men, and 22.7 pg/mL among women. The age-dependent 99th percentiles of hs-cTnI in men and women were as follows: 28.8 versus 12.5 pg/mL for 18 to 35 years, 20.4 versus 9.2 pg/mL for 36 to 50 years, 24.2 versus 13.6 pg/mL for 51 to 65 years, and 27.9 versus 32.2 pg/mL for ≥66 years.The 99th percentile reference interval for hs-cTnI in healthy adults from the Sichuan area was similar to the manufacturer's recommendation. Men had a higher 99th percentile hs-cTnI value than women in the age range of 18 to 65 years.

Differential Expression of Cardiac Troponin T and I in a Patient with Isolated Skeletal Muscular Sarcoidosis

A 49-year-old female was referred to our hospital due to high serum creatine kinase (CK) (2,605 IU/L) and serum cardiac troponin T (cTnT) (0.342 ng/mL) levels. She had no other complaints and further examinations suggested no signs of cardiac disease. Additionally, the serum cardiac troponin I (cTnI) levels were normal. She reported having gradually felt difficulty in walking upstairs. A biopsy indicated skeletal muscle sarcoidosis with positive staining for cTnT. Steroid therapy immediately resolved her muscular symptoms with a normalization of the serum CK levels. Since the serum levels of cTnI were normal, the concomitant measurement of cTnT/cTnI might be useful to diagnose skeletal muscular disease biochemically in such cases.

Influence of the cardiac glycoside digoxin on cardiac troponin I, acid-base and electrolyte balance, and haematobiochemical profiles in healthy donkeys (Equus asinus)

BACKGROUND

The effect of digoxin administration on the serum concentration of the cardiac troponin I (cTnI) has not been reported to date in equidae. This study was therefore designed to evaluate the effect of digoxin on cardiac cell damage in donkeys (Equus asinus) as assessed by cTnI, acid-base and electrolyte balance and haematobiochemical profiles. Ten clinically healthy donkeys were given an IV infusion of digoxin at a dose of 14 μg/kg. Blood samples were collected from the donkeys up through 72 h post-injection.

RESULTS

Three of the donkeys exhibited increased heart and respiratory rates post-injection. In the other seven animals, the heart and respiratory rates were lower 4 h post-injection. The serum digoxin concentration increased significantly at many time points after injection. The serum concentration of cTnI did not differ significantly between pre- and post-injection. An increase in blood pH was noted at 3 h after digoxin injection. There were also increases in PO2 and in oxygen saturation. Decreases in PCO2 at 2 to 48 h post-injection as well as a decrease in blood lactate at 4 h post-injection were observed. The serum concentration of glucose remained significantly elevated at all-time points after digoxin injection.

CONCLUSIONS

It is concluded that administration of digoxin to healthy donkeys (14 μg/kg) did not result in elevations of serum cTnI concentration, signs of digoxin intoxication, ECG abnormalities and did not increase serum concentrations of blood urea nitrogen and creatinine.

Salivary troponin I as an indicator of myocardial infarction

BACKGROUND & OBJECTIVES

Accurate and rapid diagnosis of acute myocardial infarction (MI) is of major clinical significance. The troponin is the biomarker of choice for detection of cardiac injury. The objective of this study was to identify salivary levels of cardiac troponin I (cTnI) in patients with acute MI.

METHODS

Thirty patients with acute MI and 28 normal healthy individuals were included in the study. cTnI levels were assayed in serum and saliva 12 and 24 h of acute MI by ELISA method.

RESULTS

In patients with acute MI, the serum and resting (unstimulated) saliva concentrations of cTnI, but not stimulated saliva cTnI, at both 12 and 24 h of onset of MI, were significantly higher than in controls. Resting saliva cTnI concentrations correlated significantly with serum cTnI levels (spearman rho = 0.34 and 0.45 in the total individuals and in the MI patients respectively).

INTERPRETATION & CONCLUSIONS

The present results suggest that saliva can be an analytical matrix for measurement of cTnI in patients with acute MI. Further studies may reveal capability of salivary cTnI for being used for developing point-of-care testing for early detection of MI in pre-clinical settings.

Exercise preconditioning initiates late cardioprotection against isoproterenol-induced myocardial injury in rats independent of protein kinase C

The objective of this study was to investigate the late cardioprotective effect of exercise preconditioning (EP) on isoproterenol (ISO)-induced myocardial injury in rats and the role of protein kinase C (PKC) in EP. Rats were injected with ISO 24 h after running on a treadmill for four periods of 10 min each at 28-30 m/min with intervening periods of rest of 10 min. Nonselective PKC inhibitor chelerythrine (CHE) was injected before EP. The myocardial injury was evaluated quantitatively in terms of the serum cardiac troponin I (cTnI) levels, the myocardial ischemia/hypoxia area, and the integral optical density (IOD) of haematoxylin-basic fuchsin-picric acid (HBFP) staining, and qualitatively in terms of the myocardial ultrastructure. EP markedly attenuated the ISO-induced myocardial ischemia/hypoxia and ultrastructural damage with lower serum cTnI levels. CHE injection before EP did not block the protective effect of EP, displaying a mild myocardial ischemia/hypoxia and well-preserved ultrastructure with even lower serum cTnI levels. The results indicate that EP can exert a late cardioprotection against ISO-induced myocardial injury, and that an injection of the nonselective PKC inhibitor CHE before EP may have a different effect on ISO-induced myocardial injury. Further investigation needs to be conducted to define the role of different PKC isozymes in EP by using isozyme-selective inhibitors.

Deciphering modifications in swine cardiac troponin I by top-down high-resolution tandem mass spectrometry

Cardiac troponin I (cTnI) is an important regulatory protein in cardiac muscle, and its modification represents a key mechanism in the regulation of cardiac muscle contraction and relaxation. cTnI is often referred to as the "gold-standard" serum biomarker for diagnosing patients with acute cardiac injury since it is unique to the heart and released into the circulation following necrotic death of cardiac tissue. The swine (Sus scrofa) heart model is extremely valuable for cardiovascular research since the heart anatomy and coronary artery distribution of swine are almost identical to those of humans. Herein, we report a comprehensive characterization of the modifications in swine cTnI using top-down high-resolution tandem mass spectrometry in conjugation with immunoaffinity chromatography purification. High-resolution high accuracy mass spectrometry revealed that swine cTnI affinity purified from domestic pig hearts was N-terminally acetylated and phosphorylated. Electron capture disassociation is uniquely suited for localization of labile phosphorylations, which unambiguously identified Ser22/Ser23 as the only basally phosphorylated sites that are well-known to be regulated by protein kinase A and protein kinase C. Moreover, a combination of tandem mass spectrometry with sequence homology alignment effectively localized a single amino acid polymorphism, V116A, representing a novel genetic variant of swine cTnI. Overall, our studies demonstrated the unique power of top-down high-resolution tandem mass spectrometry in the characterization of protein modifications, including labile phosphorylation and unexpected sequence variants.

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

BACKGROUND

The World Health Organization (WHO) criteria for the diagnosis of acute myocardial infarction (AMI) includes presentation of chest pain over 20 min, evolutionary changes on the electrocardiogram (ECG), and abnormal levels of cardiac enzymes.

HYPOTHESIS

A multicenter study was conducted to evaluate the efficacy of cardiac troponin I (cTnI) in detecting and ruling out AMI.

METHODS

The normal range for cTnI in 149 apparently healthy subjects without known history of cardiac or other diseases was 0 to 0.5 ng/ml. Cutoffs of 2.5 ng/ml for c TnI and 5.0 ng/ml for creatine kinase-MB (CK-MB) were used.

RESULTS

The diagnostic sensitivity of blood collected from 291 consecutive patients with suspicion of AMI was 95.0 and 96.4%, respectively, for samples obtained at 4-48 h after AMI onset. CK-MB was more sensitive during the early 4-8 h interval (84 vs. 74%); both had 100% sensitivity from 12-36 h. CTnI remained at 100% for 72 h, while CK-MB declined to 57%. The clinical specificity was 97.4 vs. 85.8%, respectively, on non-AMI patients with cardiac and noncardiac diseases, and those with renal disease.

CONCLUSION

cTnI is an excellent marker for detecting and ruling out AMI, because it has better specificity and a wider diagnostic window than the accepted standard, CK-MB.

Allele and species dependent contractile defects by restrictive and hypertrophic cardiomyopathy-linked troponin I mutants

Restrictive cardiomyopathy (RCM) is a debilitating disease characterized by impaired ventricular filling, reduced ventricular volumes, and severe diastolic dysfunction. Hypertrophic cardiomyopathy (HCM) is characterized by ventricular hypertrophy and heightened risk of premature sudden cardiac death. These cardiomyopathies can result from mutations in the same gene that encodes for cardiac troponin I (cTnI). Acute genetic engineering of adult rat cardiac myocytes was used to ascertain whether primary physiologic outcomes could distinguish between RCM and HCM alleles at the cellular level. Co-transduction of cardiac myocytes with wild-type (WT) cTnI and RCM/HCM linked mutants in cTnI's inhibitory region (IR) demonstrated that WT cTnI preferentially incorporated into the sarcomere over IR mutants. The cTnI IR mutants exhibited minor effects in single myocyte Ca(2+)-activated tension assays yet prolonged relaxation and Ca(2+) decay. In comparison RCM cTnI mutants in the helix-4/C-terminal region demonstrated a) hyper-sensitivity to Ca(2+) under loaded conditions, b) slowed myocyte mechanical relaxation and Ca(2+) transient decay, c) frequency-dependent Ca(2+)-independent diastolic tone, d) heightened myofilament incorporation and e) irreversible cellular contractile defects with acute diltiazem administration. For species comparison, a subset of cTnI mutants were tested in isolated adult rabbit cardiac myocytes. Here, RCM and HCM mutant cTnIs exerted similar effects of slowed myocyte relaxation and Ca(2+) transient decay but did not show variable phenotypes by cTnI region. This study highlights cellular contractile defects by cardiomyopathy mutant cTnIs that are allele and species dependent. The species dependent results in particular raise important issues toward elucidating a unifying mechanistic pathway underlying the inherited cardiomyopathies.

The relative utility of cardiac troponin I, creatine kinase-MBmass, and myosin light chain-1 in the long-term risk stratification of patients with chest pain

BACKGROUND

Sensitive and specific cardiac markers convey important short-term prognostic information about patients with an acute coronary syndrome. There are, however, few data assessing their value as long-term predictors.

HYPOTHESIS

The aim of the current study was to assess the relative value of three such markers and clinical characteristics in determining the long-term prognosis of patients with chest pain.

METHODS

Cardiac troponin I (cTnI), myosin light chain-(MLC-1), and creatine kinase-MBmass levels were obtained on admission (0 h) and at 4, 8, 16, and 24 h in 208 patients with chest pain. Eligible subjects were determined, at the time of hospital admission, to be at >7% risk of acute myocardial infarction (MI), but without new ST-segment elevation on their presenting electrocardiogram. Follow-up was performed a median of 28 (range 1-46) months later. The primary study endpoint was death or nonfatal MI, subsequent to the index admission.

RESULTS

Cardiac TnI levels > or = 0.2 ng/ml (odds ratio [OR] 1.93, 95% confidence interval [CI] 1.09-3.40) and MLC-1 levels > or = 1 ng/ml (OR 3.24, 95% CI 1.83-5.73) were both significant predictors of death or MI during long-term follow-up; MLC-1 was, however, the only independent biochemical predictor (OR 2.11,95% CI 1.14-3.93).

CONCLUSIONS

Both cTnl and MLC-1 predict the long-term outcome of patients with chest pain, but, in this cohort, MLC-1 proved to be a better predictor of mortality and nonfatal acute MI.

Detection of a novel sense-antisense RNA-hybrid structure by RACE experiments on endogenous troponin I antisense RNA

Conformational changes in the troponin/tropomyosin complex significantly alter the mechanical properties of cardiac muscle. Phosphorylation of cardiac troponin I, part of the troponin/tropomyosin complex, reduces calcium affinity, which leads to increased relaxation of cardiac muscle. Because cardiac troponin I plays a central role in tuning the heart to different work demands, detailed knowledge of troponin I protein regulation is required. Our group previously detected naturally occurring antisense RNA for troponin I in human and rat hearts, and here, attempt to unravel the structure of rat cardiac troponin I antisense RNA. We performed rapid amplification of cDNA ends (RACE) experiments and discovered antisense sequences identical to a copy of the sense mRNA, which led us to conclude that the antisense RNA must be transcribed from troponin I mRNA in the cytoplasm. Moreover, we isolated RNA structures comprising sense and antisense sequences in one continuous molecule. As we found no homolog structures described in the literature, we called this "hybrid RNA." Because a duplex formation was demonstrated previously we concluded that hybrid RNA is a consequence of a tight interaction between sense and antisense troponin I RNA in vivo, which we discuss in the article.

Multicentre evaluation of the diagnostic value of cardiac troponin T, CK-MB mass, and myoglobin for assessing patients with suspected acute coronary syndromes in routine clinical practice

OBJECTIVE

To assess the diagnostic efficiency of the third generation cardiac troponin T assay in routine clinical practice.

DESIGN

Prospective observational study of unselected consecutive admissions.

SETTING

Multicentre study in 43 teaching and non-teaching hospitals in 13 countries.

SUBJECTS

1105 hospital admissions, median age 67 years (range 15-96 years, 63.7% male) with suspected acute coronary syndromes (72.3% of cases) or other non-specific symptoms where cardiac disease required exclusion (27.7%).

INTERVENTIONS

Over the study period, myoglobin, creatine kinase MB isoenzyme (CK-MB), and cardiac troponin T where measured in parallel with conventional diagnostic tests. Final diagnostic classification involved standard ECG changes and CK-MB mass exceeding 5.0 microg/l.

MAIN OUTCOME MEASURES

Diagnostic efficiency was assessed by receiver operator characteristic curve analysis including and excluding patients with unstable angina.

RESULTS

Measurement of cardiac troponin T was diagnostically equivalent to CK-MB and both were better than myoglobin, with areas under the curve at 12 hours of 0.94, 0.99, and 0.80, respectively. Diagnostic criteria using CK-MB were inadequate and showed bias when patients with unstable angina were included. Elevations of cardiac troponin T did not occur when cardiac disease could be categorically excluded but were found in clinical conditions other than suspected acute coronary syndromes.

CONCLUSIONS

CK-MB is unsuitable as a diagnostic gold standard even at the proposed lower threshold. A lower cut off for cardiac troponin T of 0.05 microg/l should be used for diagnosis of acute myocardial infarction. Diagnosis of acute myocardial infarction cannot be made solely on the basis of a cardiac troponin T result.

Myocardial infarction redefined: the new ACC/ESC definition, based on cardiac troponin, increases the apparent incidence of infarction

OBJECTIVES

To investigate the impact of the redefinition of the diagnostic criteria for myocardial infarction on its apparent incidence in a non-selected and representative series of patients admitted with acute chest pain.

DESIGN

Single centre prospective study.

SETTING

Medical assessment unit and cardiology wards of an inner city university hospital.

PATIENTS

80 consecutive patients aged over 25 years admitted with suspected ischaemic acute chest pain (excluding those where the ECG indicated definite myocardial infarction).

INTERVENTIONS

Measurement of concentrations of conventional cardiac biomarkers (creatine kinase and its MB isoenzyme, CK-MB) and concentrations of the highly specific diagnostic indicator of myocardial damage, cardiac troponin I (cTnI) 12-24 hours after the onset of acute chest pain.

MAIN OUTCOME MEASURES

Frequency of myocardial infarction as assessed by conventional diagnostic criteria (creatine kinase and CK-MB) plus clinical symptoms of infarction, versus frequency of infarction based on high sensitivity troponin assays.

RESULTS

Among patients with acute coronary syndromes but non-diagnostic ECG changes, 40% (32/80) fulfilled the new criteria for myocardial infarction using high sensitivity cTnI measurement, compared with 29% (23/80) using the conventional diagnostic criteria for myocardial infarction.

CONCLUSIONS

The implications of the redefinition of myocardial infarction on patients, their care, and the use of health care resources are substantial.

Effect of elevated concentration of alkaline phosphatase on cardiac troponin I assays

Troponin I is the regulatory subunit of troponin complex associated with the actin thin filament within muscle cells. Cardiac troponin I (cTnI) is a good marker for diagnosis of myocardial damage. Several immunoassays are available for determination of cTnI in serum. The Stratus cTnI fluorometric enzyme immunoassay (Dade International) uses alkaline phosphatase (ALP) substrate. The microparticle enzyme immunoassay (MEIA) for cTnI (Abbott Laboratories) also uses ALP conjugate. On the other hand, the chemiluminescent assay (CLIA) for cTnI (Bayer Diagnostics) does not use ALP. ALP activity may frequently be elevated in serum of patients being evaluated for suspected myocardial infarction. Therefore, we studied the potential interference of ALP in cTnI assays. Serum pools were prepared from patients, and various concentrations of ALP solution were added to different aliquots. The cTnI concentrations were measured by the Stratus, MEIA, and CLIA assays. We observed no interference of ALP in the MEIA and CLIA assay for cTnI. On the other hand, we observed significant positive interference of ALP when cTnI concentrations were measured using the Stratus.