The role of cardiac troponin T and other new biochemical markers in evaluation and risk stratification of patients with acute chest pain syndromes

Predictive value of inflammation and myocardial necrosis markers in acute coronary syndrome

Introduction. Biochemical cardiac markers play an important role in diagnosing and treatment of patients with acute coronary syndrome. Markers of myocytes necrosis, troponins, have been recommended for diagnosing and treatment of myocardial infarction with ST segment elevation, myocardial infarction without ST segment elevation and unstable angina pectoris. Two more groups of cardiac markers have been gaining in importance: inflammation markers and cardiac function markers. The objective of this study was the risk stratification and identification of patients with coronary syndrome, who could take advantage from evolutionary changes of serum cardiac markers. Material and Methods. The method of the analysis sums up the results of independently published studies and literature and data base review, such as MEDLINE, PubMed and KOBSON. Inflammation markers. Systemic and localized inflammation plays an important role in the development of acute coronary syndrome. The following inflammation markers are available: C-reactive protein. IL-2, sedimentation of erythrocytes and fibrinogen; as well as myocardial necrosis markers: creatine kinase MB, myoglobin and cardiac troponins. Conclusion. Tropinins are ideal markers which enable early detection of patients with acute coronary syndrome, whereas inflammation markers are helpful in diagnosing and assessing the severity of inflammation.

Strategic use of immunoprecipitation and LC/MS/MS for trace-level protein quantification: myosin light chain 1, a biomarker of cardiac necrosis

Myosin light chain 1 (Myl3) is a 23-kDa isoform of one of the subunits of myosin, a protein involved in muscle contraction. Myl3 is presently being studied as a biomarker of cardiac necrosis to predict drug-induced cardiotoxicity, and in the work presented here, an LC/MS/MS assay was developed and validated to measure Myl3 in rat serum. The key steps in this approach involved immunoaffinity purification of Myl3 from serum followed by on-bead digestion with trypsin to release a surrogate peptide. This tryptic peptide was quantified using a synthetic peptide standard and a corresponding stable isotope-labeled internal standard, and the results were stoichiometrically converted to Myl3 serum concentrations. Myl3 concentrations were corrected for peptide recovery following immunoprecipitation and digestion (85%) and showed excellent agreement with synthetic peptide standards. Both the synthetic peptide and His-Myl3 protein were used to evaluate assay accuracy (% RE) and precision (% CV), which were measured on each of 3 days. The synthetic peptide was evaluated over the range of 0.073-7.16 nM, while Myl3 protein QC samples prepared in rat serum were evaluated over the range of 0.13-6.62 nM. To prepare control matrix, endogenous Myl3 was immunodepleted from pooled rat serum. Peptide interday accuracy and precision did not exceed 7.6 and 11.1%, and Myl3 interday accuracy and precision did not exceed 12.9 and 13.2%, respectively. Data are presented from the application of this assay to establish a time course in which rats demonstrated a marked increase in Myl3 serum concentrations following administration of isoproterenol, a beta-adrenergic receptor agonist known to induce cardiac injury. This assay is an example of a larger effort in our laboratory to use LC/MS/MS in conjunction with immunoaffinity techniques to evaluate candidate biomarkers of target organ toxicity and to expedite the development of biomarker assays for drug development.

New cut-off values of cardiac markers for risk stratification of angina pectoris

BACKGROUND

The aim of this present prospective study was to investigate the accuracy of cardiac markers for the prediction of subsequent cardiac events (cardiac death, acute myocardial infarction and recurrent ischemia requiring coronary revascularization).

METHODS

Fibrinogen, cardiac troponin T, troponin I, creatine phosphokinase myocardial fraction, C-reactive protein and myoglobin at baseline and after 6 h were measured on 154 patients (109 male, 63+/-11 years) with chest pain. Receiver operator characteristic analyses were performed to determine cut-off points of cardiac markers in prediction of adverse events.

RESULTS

The following cut-off values for prediction of cardiac events were calculated: troponin I at baseline 0.3 ng/ml (predictive accuracy=0.870), troponin I at 6 h 0.50 ng/ml (p.a.=0.909); troponin T at baseline 0.05 ng/ml (p.a.=0.643), troponin T at 6 h 0.05 ng/ml (p.a.=0.612), creatine phosphokinase myocardial fraction at baseline 2.0 ng/ml (p.a.=0.721), creatine phosphokinase myocardial fraction at 6 h 2.5 ng/ml (p.a.=0.734), myoglobin at baseline 23 ng/ml (p.a.=0.623), myoglobin at 6 h 26 ng/ml (p.a.=0.617), C-reactive protein at baseline 0.31 mg/dl (p.a.=0.662), C-reactive protein at 6 h 0.55 mg/dl (p.a.=0.682), and fibrinogen at baseline 360 mg/dl (p.a.=0.701). The combination of baseline troponin I with different parameters resulted in a higher sensitivity of up to 98%, with a similar predictive accuracy, but a lower specificity. Additive measurements of cardiac troponin I at 6 h to baseline cardiac troponin T and I proved to be the best combination for prediction of subsequent cardiac events.

CONCLUSIONS

Changes in cut-off levels of cardiac markers and inflammatory parameters results in a high accuracy of risk stratification in patients with chest pains. Combination of these measurements might further help in the identification of patients who would benefit from early coronary revascularization.

Effects of transvenous pacing on cardiac troponin release

Cardiac troponins are invaluable tools for the detection of minimal myocardial injury. No study to date has analyzed the effect of permanent cardiac pacing on minimal myocardial injury detection by cardiac troponin I (cTnI) measurement. We investigated 76 clinically stable patients (mean age 75 years, range 31-93 years, 59% men) listed for elective endocardial permanent pacemaker insertion. Patients were required to have normal levels of cardiac cTnI, aspartate transaminase (AST) and creatinine kinase (CK) on a venous blood sample taken immediately prior to elective pacemaker implantation. Repeat measurements of AST, CK, and cTnI were performed at a mean of 19.2 post implantation. There was a detectable small rise in cTnI levels above normal in 21% of patients in a second blood sample taken 18-21 hours later (mean cTnI 0.39 +/- 0.37 microg/L, normal < 0.15 microg/L). The only factor that correlated with this rise was prolonged x ray screening time for lead implantation.

Classification and risk stratification of patients with acute chest pain using a low discriminatory level of cardiac troponin T

BACKGROUND

Cardiac troponins are the biochemical markers of choice for the evaluation of acute coronary syndromes (ACS). Using the first-generation test, most studies related adverse outcome to > 0.20 or 0.10 microg/l cardiac troponin T (cTnT) levels. With the highly sensitive and specific second- and third-generation assays, cTnT is undetectable in most healthy individuals.

HYPOTHESIS

We evaluated whether a lower cTnT level, within 24 h of admission, could indicate an increased risk of future complications.

METHODS

During 1998-1999, clinical data were collected in 260 patients with ACS. Cardiac troponin T was measured at arrival, and 4, 8, and 12-24 h thereafter. The maximum cTnT value was then used to assess, over a 15-month follow-up period, the cumulative risk of death or myocardial infarction (MI), as well as rates of events according to quartiles of cTnT values.

RESULTS

Patients with < or = 0.03 microg/l cTnT levels had the lowest rate of adverse events and the best Kaplan-Meier event-free survival curve. Increasing cTnT levels were associated with stepwise increases in mortality rates and with a constant 10-fold increase in MI rates during follow-up.

CONCLUSIONS

A low threshold cTnT elevation is recommended to assess the risk of ACS. All cTnT elevations > 0.03 microg/l predict a higher risk of MI during follow-up, whereas increasing values predict mortality in relation to the amount of elevation.

Evaluation and risk stratification of acute coronary syndromes using a low cut-off level of cardiac troponin T, combined with CK-MB mass determination

OBJECTIVES

To study the usefulness of combined cardiac Troponin T (cTnT) and CK-MB mass determinations in risk stratification of acute coronary syndromes.

DESIGN AND METHODS

Blood samples for cTnT and CK-MB mass were collected at arrival and 4, 8, and 12-24 later in 301 consecutive patients with recent acute chest pain (ACP). Data were also collected for cardiac events.

RESULTS

Combined cardiac mortality/nonfatal myocardial infarction over a period of 15 months was lowest in patients with <0.04 microg/l cTnT and -<5.0 microg/l CK-MB mass intermediate in those with elevated cTnT but normal CK-MB mass and highest when both markers were elevated, in absence of early reperfusion.

CONCLUSION

The use of a low cut-off point of cTnT, combined wit CK-MB mass determination, offers a good strategy for risk stratification of ACP patients.

Cardiac troponins

Cardiac troponins I and T are proteins integral to the function of cardiac muscle. They are very sensitive markers for the detection of myocardial damage, and the ability to assay their serum levels accurately and quickly have revolutionized the concepts of minor myocardial injury and infarction. They are also powerful prognostic indicators of future adverse cardiac events. Limitations, more of troponin T than I, include decreased specificity in renal failure and skeletal muscle disease. Rapid, whole blood assays are now available that can be done at the patient's bedside. This review discusses the cardiac troponins, their biochemistry, the assays for them currently available, and their roles in the evaluation of cardiac disease in the Emergency Department (ED).

Platelet hyperaggregability to platelet activating factor (PAF) in non-ST elevation acute coronary syndromes

It is known that myocardial ischaemia increases platelet aggregatory response to various agonists, ex vivo. We investigated the platelet aggregatory response to platelet activating factor (PAF), ex vivo, in patients with non-ST elevation acute coronary syndromes and determined the specificity and sensitivity of this response. Thirty-two consecutive patients with non-ST elevation acute coronary syndromes and 20 healthy volunteers were studied. Platelet aggregation in platelet-rich plasma was studied on the day of admission. The maximal aggregation achieved within 2 min after the addition of PAF (100 nM) was expressed as a percentage of 100% light transmission. PAF EC50 values were defined as the concentration that induces 50% of maximal aggregation. The PAF EC50 values of the non-ST elevation acute coronary syndromes patients were significantly lower compared to those of the controls (p < 0.0001). The maximal percentage of aggregation was also significantly higher (p < 0.0005). Ninety-one per cent of the patients were correctly classified using PAF EC50 values (specificity 90.0% and sensitivity 91.2%); the corresponding results using the maximal percentage of aggregation were 80% (specificity 70.0% and sensitivity 87.5%). The estimated values used as thresholds were 22.47 nM and 17.97 for the PAF EC50 and the maximal percentage of aggregation, respectively. The results of the present study suggest that platelet hyperaggregability to PAF, ex vivo, in non-ST elevation acute coronary syndromes is characterised by a high specificity and sensitivity, and thus it may represent a mechanism contributing to the pathophysiology of acute coronary syndromes.

Differences in the diagnosis of myocardial infarction by troponin T compared with clinical and epidemiologic criteria

We investigated the difference in the number of myocardial infarction (MI) diagnoses based on troponin T compared with clinical and epidemiologic (modified FINnish Multinational MONItoring of trends and determinants in CArdiovascular diseases) diagnoses, and the prognosis of patients with discordant diagnoses. Five hundred fifty-nine consecutive patients (315 men and 244 women, median age 69 years) were admitted to the hospital with a suspected acute coronary syndrome. Median follow-up time was 17 months. Of the 559 patients, 127 had a clinical and 137 an epidemiologic diagnosis of MI. When a diagnosis of MI was primarily based on troponin T (>0.10 microg/L), the number of MIs was 169, which increased by 33% compared with the number of MIs by clinical diagnosis, and by 23% compared with those by epidemiologic diagnosis. However, troponin T was not elevated in 13% of the 127 patients with the clinical diagnosis and in 14% of the 137 patients with the epidemiologic diagnosis of MI. Among patients in whom clinical diagnosis of MI was not made, the prognosis with regard to coronary death or nonfatal MI was not significantly worse in patients with troponin T >0.10 microg/L than < or =0.10 microg/L (hazard ratio 1.07; 95% confidence interval 0.62 to 1.84). In patients with a suspected acute coronary syndrome, troponin T-based diagnostics leads to an increase in the number of patients diagnosed with MI compared with clinical or epidemiologic diagnosis. The prognostic impact of troponin T in patients without clinical diagnosis of MI based on elevations in conventional enzyme activities needs further study in larger series of patients.

Biomarkers in disease and health

Biomarkers have considerable potential in aiding the understanding of the relationship between diet and disease or health. However, to assess the role, relevance and importance of biomarkers on a case by case basis it is essential to understand and prioritise the principal diet and health issues. In the majority of cases, dietary compounds are only weakly biologically active in the short term, have multiple targets and can be both beneficial and deleterious. This poses particular problems in determining the net effect of types of foods on health. In principle, a biomarker should be able to contribute to this debate by allowing the measurement of exposure and by acting as an indicator either of a deleterious or of an enhanced health effect prior to the final outcome. In this review, the examples chosen - cancer (stomach, colon/rectal, breast); coronary heart disease and osteoporosis - reflect three major diet-related disease issues. In each case the onset of the disease has a genetic determinant which may be exacerbated or delayed by diet. Perhaps the most important factor is that in each case the disease, once manifest, is difficult to influence in a positive way by diet alone. This then suggests that the emphasis for biomarker studies should focus on predictive biomarkers which can be used to help in the development of dietary strategies which will minimise the risk and be of greater benefit.

Elevated cardiac troponin levels predict the risk of adverse outcome in patients with acute coronary syndromes

BACKGROUND

Elevations of cardiac troponin T or I are predictive of adverse outcomes in patients with acute coronary syndromes. However, odds ratios (ORs) vary substantially between studies. This investigation refines these values by means of a meta-analysis.

METHODS

Twenty-one studies were suitable. ORs were calculated for short-term (30 days) and long-term (5 months to 3 years) follow-up in patients with ST-segment elevation (ST upward arrow), in those without ST-segment elevation (no ST upward arrow), and in patients with unstable angina. The primary end point was a composite of death or nonfatal myocardial infarction.

RESULTS

A total of 18,982 patients were included. At 30 days, the OR for death or myocardial infarction was 3.44 (95% confidence interval [CI], 2.94-4.03; P <. 00001) for patients with positive troponin. In the ST upward arrow group, troponin elevations carried a 2.86-fold (95% CI, 2.35-3.47; P <.0001) higher risk during short-term follow-up, which was maintained long term. The no-ST upward arrow patients with troponin elevations manifested a 4.93-fold (95% CI, 3.77-6.45; P <.0001) increase of adverse outcomes. The OR for patients with unstable angina and positive troponin was 9.39 (95% CI, 6.46-13.67; P <.0001). For cardiac death alone, the results were similar.

CONCLUSIONS

Patients with acute coronary syndromes who have troponin elevations show a substantial increase in risk during short and long-term follow-up.

Correlation of Antemortem Serum Creatine Kinase, Creatine Kinase-MB, Troponin I, and Troponin T with Cardiac Pathology

Background: Spurious increases in serum troponins, especially troponin T, have been reported in patients with and without acute myocardial syndromes.

Methods: We studied 78 autopsied patients without clinical myocardial infarction (MI) and correlated histologic cardiac findings with antemortem serum creatine kinase (CK), its MB isoenzyme (CK-MB), cardiac troponin I (cTnI), and cardiac troponin T (cTnT).

Results: There was no significant myocardial pathology in 15 patients. Cardiac pathologies were in five groups: scarring from previous MI or patchy ventricular fibrosis (n = 9), recent MI (n = 27), healing MI (n = 7), degenerative myocyte changes consistent with congestive heart failure (CHF; n = 12), and other cardiac pathologies (n = 8). The median concentrations in the five groups were not significantly different for either CK or CK-MB. Compared with the no-pathology group, only the MI group was significantly different for cTnI, and the MI and other pathology groups were significantly different for cTnT. For patients with MI, 22%, 19%, 48%, and 65% had increased CK, CK-MB, cTnI, and cTnT, respectively; for CHF and other cardiac pathologies combined, the percentages were 28%, 17%, 22%, and 50%. For patients with increased cTnI, 72% and 28% had MI and other myocardial pathologies, respectively; patients with increased cTnT had 64% and 36%, respectively. Patients without myocardial pathology had no increases in CK-MB, cTnI, or cTnT.

Conclusions: All patients with increased serum CK-MB, cTnI, and cTnT had significant cardiac histologic changes. The second-generation cTnT assay appears to be a more sensitive indicator of MI and other myocardial pathologies than the cTnI assay used in this study.

Risk stratification after acute myocardial infarction in the reperfusion era

Historically, risk stratification for survivors of acute myocardial infarction (AMI) has centered on 3 principles: assessment of left ventricular function, detection of residual myocardial ischemia, and estimation of the risk for sudden cardiac death. Although these factors still have important prognostic implications for these patients, our ability to predict adverse cardiac events has significantly improved over the last several years. Recent studies have identified powerful predictors of adverse cardiac events available from the patient history, physical examination, initial electrocardiogram, and blood testing early in the evaluation of patients with AMI. Numerous studies performed in patients receiving early reperfusion therapy with either thrombolysis or primary angioplasty have emphasized the importance of a patent infarct related artery for long-term survival. The predictive value of a variety of noninvasive and invasive tests to predict myocardial electrical instability have been under active investigation in patients receiving early reperfusion therapy. The current understanding of the clinically important predictors of clinical outcomes in survivors of AMI is reviewed in this article.

Troponin T and creatinine kinase isoenzyme MB mass in the diagnosis of myocardial infarction

The aim of this study was to compare troponin T (TnT) and creatine kinase isoenzyme MB mass (CK-MBm) with conventional enzymes, ie CK, CK-MB activity and lactate dehydrogenase isoenzyme 1, in the diagnosis of myocardial infarction (MI). 624 patients (351 men and 273 women, median age 69 years) were admitted to hospital with suspicion of an acute coronary heart disease event. TnT was elevated (> 0.10 microg/L) in 100%, CK-MBm (> 5.0 microg/L) in 99%, and both markers in 99% of the 89 patients with the diagnosis of a definite MI according to modified FINMONICA criteria. In the 60 patients with the diagnosis of a probable MI, TnT was elevated in 65%, CK-MBm in 67% and both markers in 60%. In the patients with unstable coronary artery disease (unstable angina or prolonged chest pain attack) and conventional enzymes within normal limits, TnT was elevated in 14%, CK-MBm in 17% and both markers in 9%. The use of TnT and CK-MBm did not lead to a major change in the diagnostics of definite MI. However, TnT and CK-MBm did not confirm the diagnosis of probable MI in one-third of the events. These new markers revealed a myocardial injury in about 15% of those patients who had unstable coronary artery disease and conventional enzymes within normal limits.