Clinical performance of three cardiac troponin assays in patients with unstable coronary artery disease (a FRISC II substudy)

Cardiovascular Biomarkers: Lessons of the Past and Prospects for the Future

Cardiovascular diseases (CVDs) are a major healthcare burden on the population worldwide. Early detection of this disease is important in prevention and treatment to minimise morbidity and mortality. Biomarkers are a critical tool to either diagnose, screen, or provide prognostic information for pathological conditions. This review discusses the historical cardiac biomarkers used to detect these conditions, discussing their application and their limitations. Identification of new biomarkers have since replaced these and are now in use in routine clinical practice, but still do not detect all disease. Future cardiac biomarkers are showing promise in early studies, but further studies are required to show their value in improving detection of CVD above the current biomarkers. Additionally, the analytical platforms that would allow them to be adopted in healthcare are yet to be established. There is also the need to identify whether these biomarkers can be used for diagnostic, prognostic, or screening purposes, which will impact their implementation in routine clinical practice.

Graded Coronary Risk Stratification for Emergency Department Patients With Chest Pain: A Controlled Cohort Study

Background Resource utilization among emergency department (ED) patients with possible coronary chest pain is highly variable. Methods and Results Controlled cohort study amongst 21 EDs of an integrated healthcare system examining the implementation of a graded coronary risk stratification algorithm (RISTRA-ACS [risk stratification for acute coronary syndrome]). Thirteen EDs had access to RISTRA-ACS within the electronic health record (RISTRA sites) beginning in month 24 of a 48-month study period (January 2016 to December 2019); the remaining 8 EDs served as contemporaneous controls. Study participants had a chief complaint of chest pain and serum troponin measurement in the ED. The primary outcome was index visit resource utilization (observation unit or hospital admission, or 7-day objective cardiac testing). Secondary outcomes were 30-day objective cardiac testing, 60-day major adverse cardiac events (MACE), and 60-day MACE-CR (MACE excluding coronary revascularization). Difference-in-differences analyses controlled for secular trends with stratification by estimated risk and adjustment for risk factors, ED physician and facility. A total of 154 914 encounters were included. Relative to control sites, 30-day objective cardiac testing decreased at RISTRA sites among patients with low (≤2%) estimated 60-day MACE risk (-2.5%, 95% CI -3.7 to -1.2%, P<0.001) and increased among patients with non-low (>2%) estimated risk (+2.8%, 95% CI +0.6 to +4.9%, P=0.014), without significant overall change (-1.0%, 95% CI -2.1 to 0.1%, P=0.079). There were no statistically significant differences in index visit resource utilization, 60-day MACE or 60-day MACE-CR. Conclusions Implementation of RISTRA-ACS was associated with better allocation of 30-day objective cardiac testing and no change in index visit resource utilization or 60-day MACE. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT03286179.

Prospective Validation and Comparative Analysis of Coronary Risk Stratification Strategies Among Emergency Department Patients With Chest Pain

Background

Coronary risk stratification is recommended for emergency department patients with chest pain. Many protocols are designed as “rule‐out” binary classification strategies, while others use graded‐risk stratification. The comparative performance of competing approaches at varying levels of risk tolerance has not been widely reported.

Methods and Results

This is a prospective cohort study of adult patients with chest pain presenting between January 2018 and December 2019 to 13 medical center emergency departments within an integrated healthcare delivery system. Using an electronic clinical decision support interface, we externally validated and assessed the net benefit (at varying risk thresholds) of several coronary risk scores (History, ECG, Age, Risk Factors, and Troponin [HEART] score, HEART pathway, Emergency Department Assessment of Chest Pain Score Accelerated Diagnostic Protocol), troponin‐only strategies (fourth‐generation assay), unstructured physician gestalt, and a novel risk algorithm (RISTRA‐ACS). The primary outcome was 60‐day major adverse cardiac event defined as myocardial infarction, cardiac arrest, cardiogenic shock, coronary revascularization, or all‐cause mortality. There were 13 192 patient encounters included with a 60‐day major adverse cardiac event incidence of 3.7%. RISTRA‐ACS and HEART pathway had the lowest negative likelihood ratios (0.06, 95% CI, 0.03–0.10 and 0.07, 95% CI, 0.04–0.11, respectively) and the greatest net benefit across a range of low‐risk thresholds. RISTRA‐ACS demonstrated the highest discrimination for 60‐day major adverse cardiac event (area under the receiver operating characteristic curve 0.92, 95% CI, 0.91–0.94, P<0.0001).

Conclusions

RISTRA‐ACS and HEART pathway were the optimal rule‐out approaches, while RISTRA‐ACS was the best‐performing graded‐risk approach. RISTRA‐ACS offers promise as a versatile single approach to emergency department coronary risk stratification.

Registration

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03286179.

Automated Retrospective Calculation of the EDACS and HEART Scores in a Multicenter Prospective Cohort of Emergency Department Chest Pain Patients

OBJECTIVES

Coronary risk scores are commonly applied to emergency department patients with undifferentiated chest pain. Two prominent risk score-based protocols are the Emergency Department Assessment of Chest pain Score Accelerated Diagnostic Protocol (EDACS-ADP) and the History, ECG, Age, Risk factors, and Troponin (HEART) pathway. Since prospective documentation of these risk determinations can be challenging to obtain, quality improvement projects could benefit from automated retrospective risk score classification methodologies.

METHODS

EDACS-ADP and HEART pathway data elements were prospectively collected using a Web-based electronic clinical decision support (eCDS) tool over a 24-month period (2018-2019) among patients presenting with chest pain to 13 EDs within an integrated health system. Data elements were also extracted and processed electronically (retrospectively) from the electronic health record (EHR) for the same patients. The primary outcome was agreement between the prospective/eCDS and retrospective/EHR data sets on dichotomous risk protocol classification, as assessed by kappa statistics (ĸ).

RESULTS

There were 12,110 eligible eCDS uses during the study period, of which 66 and 47% were low-risk encounters by EDACS-ADP and HEART pathway, respectively. Agreement on low-risk status was acceptable for EDACS-ADP (ĸ = 0.73, 95% confidence interval [CI] = 0.72 to 0.75) and HEART pathway (ĸ = 0.69, 95% CI = 0.68 to 0.70) and for the continuous scores (interclass correlation coefficients = 0.87 and 0.84 for EDACS and HEART, respectively).

CONCLUSIONS

Automated retrospective determination of low risk status by either the EDACS-ADP or the HEART pathway provides acceptable agreement compared to prospective score calculations, providing a feasible risk adjustment option for use in large data set analyses.

Performance of Coronary Risk Scores Among Patients With Chest Pain in the Emergency Department

BACKGROUND

Both the modified History, Electrocardiogram, Age, Risk factors and Troponin (HEART) score and the Emergency Department Assessment of Chest pain Score (EDACS) can identify patients with possible acute coronary syndrome (ACS) at low risk (<1%) for major adverse cardiac events (MACE).

OBJECTIVES

The authors sought to assess the comparative accuracy of the EDACS (original and simplified) and modified HEART risk scores when using cardiac troponin I (cTnI) cutoffs below the 99th percentile, and obtain precise MACE risk estimates.

METHODS

The authors conducted a retrospective study of adult emergency department (ED) patients evaluated for possible ACS in an integrated health care system between 2013 and 2015. Negative predictive values for MACE (composite of myocardial infarction, cardiogenic shock, cardiac arrest, and all-cause mortality) were determined at 60 days. Reclassification analyses were used to assess the comparative accuracy of risk scores and lower cTnI cutoffs.

RESULTS

A total of 118,822 patients with possible ACS were included. The 3 risk scores' accuracies were optimized using the lower limit of cTnI quantitation (<0.02 ng/ml) to define low risk for 60-day MACE, with reclassification yields ranging between 3.4% and 3.9%, while maintaining similar negative predictive values (range 99.49% to 99.55%; p = 0.27). The original EDACS identified the largest proportion of patients as low risk (60.6%; p < 0.0001).

CONCLUSIONS

Among ED patients with possible ACS, the modified HEART score, original EDACS, and simplified EDACS all predicted a low risk of 60-day MACE with improved accuracy using a cTnI cutoff below the 99th percentile. The original EDACS identified the most low-risk patients, and thus may be the preferred risk score.

Challenges in high-sensitive troponin assay interpretation for intensive therapy

Cardiac troponins T and I are considered highly sensitive and specific markers for the diagnosis of acute myocardial infarction. Currently, a series of nonprimary cardiac abnormalities may manifest as an elevation in high-sensitive assays. The reduction in their detection limits has allowed earlier diagnosis and the use of evidence-based therapeutic measures; however, this characteristic has increased the spectrum of detectable noncoronary heart diseases, which poses challenges for characterizing acute coronary syndromes and creates a new role for these tests in known disorders in intensive care units, especially sepsis. Management of patients through a greater understanding of how these markers behave should be re-evaluated to ensure their correct interpretation.

Evaluation of a high-sensitivity cardiac troponin I assay compared to a first-generation cardiac troponin I assay in Doberman Pinschers with and without dilated cardiomyopathy

BACKGROUND

Echocardiography and 24-hour ECG are the gold standard tests to diagnose dilated cardiomyopathy (DCM) in Doberman Pinschers (DP), but myocardial damage might be detected earlier using a high-sensitivity cardiac troponin I (hs-cTnI) assay.

OBJECTIVE

To evaluate and compare an hs-cTnI assay (Advia Centaur TnI-Ultra assay) with a conventional cTnI assay in DP with different stages of DCM and in healthy DP.

ANIMALS

Three hundred forty-five examinations from 162 DP with and 179 DP without DCM.

METHODS

Prospective longitudinal study. Dogs were allocated into 6 groups based on echocardiographic and 24-hour ECG criteria: (1) healthy group (179 dogs), (2) last-normal group (29 dogs), which included dogs that were considered to be healthy at the time of their examination but were assigned to the last-normal group retrospectively when DCM was diagnosed at their next examination within 1.5 years, (3) only arrhythmias (45 dogs, 119 examinations), (4) only echocardiographic changes (24 dogs, 61 examinations), (5) echocardiographic changes with ventricular premature complexes (41 dogs, 100 examinations), and (6) decompensated (23 dogs, 36 examinations). Hs-cTnI and conventional cTnI concentration measurements were performed and compared.

RESULTS

A cutoff value of hs-cTnI concentration >0.113 ng/mL had a sensitivity of 81.2% and a specificity of 73.2% to identify the presence of DCM. The conventional cTnI assay showed a similar test performance, but the hs-cTnI assay identified more dogs (21/29 dogs, 72%) in the last-normal group compared to the conventional cTnI test (18/29 dogs, 62%).

CONCLUSIONS AND CLINICAL IMPORTANCE

The hs-cTnI is an additional test with good potential to identify early DCM.

Sensitive Cardiac Troponins: Could They Be New Biomarkers in Pediatric Pulmonary Hypertension Due to Congenital Heart Disease?

To analyze the role of sensitive cardiac troponin I (scTnI) and high-sensitive troponin T (hscTnT) in the determination of myocardial injury caused by volume and pressure load due to pulmonary hypertension (PH) and to investigate if these markers may be useful in the management of PH in childhood. Twenty-eight patients with congenital heart disease (CHD) with left to right shunt and PH, 29 patients with CHD with left to right shunt but without PH, and 18 healthy children, in total 75 individuals, were included in the study. All cases were aged between 4 and 36 months. Echocardiographic evaluation was performed in all cases, and invasive hemodynamic investigation was performed in 33 cases. Blood samples were obtained from all cases, for the measurement of brain natriuretic peptide (BNP), pro-brain natriuretic peptide (pro-BNP), sensitive cardiac troponin I (scTnI), and high-sensitive troponin T (hscTnT) levels. The mean BNP, pro-BNP, scTnI, and hsTnT levels were statistically significantly higher in patients with PH than in the patients without PH (p < 0.001). A statistically significant positive correlation was determined between pulmonary artery systolic pressure and scTnI and hscTnT levels (r = 0.34 p = 0.01, r = 0.46 p < 0.001, respectively) levels. Pulmonary hypertension determined in congenital heart diseases triggers myocardial damage independently of increased volume or pressure load and resistance, occurring by disrupting the perfusion via increasing ventricular wall tension and the myocardial oxygen requirement. Serum scTnI and hscTnT levels may be helpful markers to determine the damage associated with PH in childhood.

The Diagnostic Value and Cost-Effectiveness of Creatine Kinase-MB, Myoglobin and Cardiac Troponin-T for Patients with Chest Pain in Emergency Department Observation Ward

Aim

To evaluate the diagnostic value and cost-effectiveness of creatine kinase-MB isomer, myoglobin and cardiac troponin-T for patients with chest pain in emergency department observation ward.

Method

A prospective study was carried out to include all patients presenting with chest pain of suspected cardiac origin and admitted to the observation ward. Electrocardiogram and blood tests for the three cardiac markers were performed at the time of consultation and six to eight hours after admission to the observation ward. Progress of the patients was followed up for 30-day survival or the condition reviewed up to six months and the final diagnoses were documented.

Result

A total of 480 patients were recruited. The incidence of acute myocardial infarction was 1.5%. No one died of cardiac cause within 30 days. Troponin was more accurate than creatine kinase for diagnosing acute myocardial infarction and it was cost-effective. Myoglobin was of no value.

Conclusion

Troponin is recommended as a diagnostic tool for evaluating patients with chest pain in observation ward.

Effect of part-time cardiac catheterization facilities in patients with acute myocardial infarction

BACKGROUND

Although the easy availability of invasive cardiac care facilities is associated with an increase in their use, their influence on outcomes is not clear. We sought to investigate whether a newly available cardiac catheterization laboratory (CCL) performing percutaneous coronary intervention (PCI) on a part-time (PT) basis might improve outcomes in patients with acute myocardial infarction (AMI).

METHODS

This was an observational cohort study that included all consecutive patients with AMI admitted to a secondary-level hospital in Spain before and after the PT-CCL opened in January 2006: during 1998-2005 and 2006-2014, respectively. All-cause in-hospital and long-term mortality were the co-primary endpoints. In-hospital complications and length of stay were secondary endpoints. For the analyses, patients were stratified according to propensity-score (PS) quintiles.

RESULTS

A total of 5339 patients were recruited, and 50.3% were managed after the opening of the PT-CCL. The PT-CCL was associated with greater use of PCI (81.2 vs. 32.5%, p<0.001) and guidelines-recommended medication (all p<0.001), lower risk of recurrent angina (PS-adjusted RR=0.160, 95% CI 0.115-0.222) and shorter length of hospital stay (PS-adjusted RR for length of stay <8days=0.357, 95% CI 0.301-0.422). In patients with NSTEMI, PT-CCL was associated with improved long-term survival (PS-adjusted HR=0.764, 95% CI 0.602-0.970).

CONCLUSIONS

In patients with AMI, a new PT-CCL was associated with greater use of PCI and guideline-recommended medication, lower risk of recurrent angina and shorter length of hospital stay. In a subset of patients with NSTEMI, PT-CCL was associated with improved long-term survival.

Early invasive versus non-invasive treatment in patients with non-ST-elevation acute coronary syndrome (FRISC-II): 15 year follow-up of a prospective, randomised, multicentre study

BACKGROUND

The FRISC-II trial was the first randomised trial to show a reduction in death or myocardial infarction with an early invasive versus a non-invasive treatment strategy in patients with non-ST-elevation acute coronary syndrome. Here we provide a remaining lifetime perspective on the effects on all cardiovascular events during 15 years' follow-up.

METHODS

The FRISC-II prospective, randomised, multicentre trial was done at 58 Scandinavian centres in Sweden, Denmark, and Norway. Between June 17, 1996, and Aug 28, 1998, we randomly assigned (1:1) 2457 patients with non-ST-elevation acute coronary syndrome to an early invasive treatment strategy, aiming for revascularisation within 7 days, or a non-invasive strategy, with invasive procedures at recurrent symptoms or severe exercise-induced ischaemia. Plasma for biomarker analyses was obtained at randomisation. For long-term outcomes, we linked data with national health-care registers. The primary endpoint was a composite of death or myocardial infarction. Outcomes were compared as the average postponement of the next event, including recurrent events, calculated as the area between mean cumulative count-of-events curves. Analyses were done by intention to treat.

FINDINGS

At a minimum of 15 years' follow-up on Dec 31, 2014, data for survival status and death were available for 2421 (99%) of the initially recruited 2457 patients, and for other events after 2 years for 2182 (89%) patients. During follow-up, the invasive strategy postponed death or next myocardial infarction by a mean of 549 days (95% CI 204-888; p=0·0020) compared with the non-invasive strategy. This effect was larger in non-smokers (mean gain 809 days, 95% CI 402-1175; p_interaction=0·0182), patients with elevated troponin T (778 days, 357-1165; p_interaction=0·0241), and patients with high concentrations of growth differentiation factor-15 (1356 days, 507-1650; p_interaction=0·0210). The difference was mainly driven by postponement of new myocardial infarction, whereas the early difference in mortality alone was not sustained over time. The invasive strategy led to a mean of 1128 days (95% CI 830-1366) postponement of death or next readmission to hospital for ischaemic heart disease, which was consistent in all subgroups (p<0·0001).

INTERPRETATION

During 15 years of follow-up, an early invasive treatment strategy postponed the occurrence of death or next myocardial infarction by an average of 18 months, and the next readmission to hospital for ischaemic heart disease by 37 months, compared with a non-invasive strategy in patients with non-ST-elevation acute coronary syndrome. This remaining lifetime perspective supports that an early invasive treatment strategy should be the preferred option in most patients with non-ST-elevation acute coronary syndrome.

FUNDING

Swedish Heart-Lung Foundation, Swedish Foundation for Strategic Research, and Uppsala Clinical Research Center.

Serial High-Sensitivity Troponin T in Post-Primary Angioplasty Exercise Test

BACKGROUND

The kinetics of high-sensitivity troponin T (hscTnT) release should be studied in different situations, including functional tests with transient ischemic abnormalities.

OBJECTIVE

To evaluate the release of hscTnT by serial measurements after exercise testing (ET), and to correlate hscTnT elevations with abnormalities suggestive of ischemia.

METHODS

Patients with acute ST-segment elevation myocardial infarction (STEMI) undergoing primary angioplasty were referred for ET 3 months after infarction. Blood samples were collected to measure basal hscTnT immediately before (TnT0h), 2 (TnT2h), 5 (TnT5h), and 8 hours (TnT8h) after ET. The outcomes were peak hscTnT, TnT5h/TnT0h ratio, and the area under the blood concentration-time curve (AUC) for hscTnT levels. Log-transformation was performed on hscTnT values, and comparisons were assessed with the geometric mean ratio, along with their 95% confidence intervals. Statistical significance was assessed by analysis of covariance with no adjustment, and then, adjusted for TnT0h, age and sex, followed by additional variables (metabolic equivalents, maximum heart rate achieved, anterior wall STEMI, and creatinine clearance).

RESULTS

This study included 95 patients. The highest geometric means were observed at 5 hours (TnT5h). After adjustments, peak hscTnT, TnT5h/TnT0h and AUC were 59% (p = 0.002), 59% (p = 0.003) and 45% (p = 0.003) higher, respectively, in patients with an abnormal ET as compared to those with normal tests.

CONCLUSION

Higher elevations of hscTnT may occur after an abnormal ET as compared to a normal ET in patients with STEMI.

Outcomes of non-acute coronary syndrome patients discharged from the emergency department with troponin positivity

BACKGROUND

Cardiac troponin elevation portends a worse prognosis in diverse patient populations. The significance of troponin elevation in patients discharged from emergency departments (EDs) without inpatient admission is not well known.

METHODS

Patients without a diagnosis of acute coronary syndrome discharged from two EDs between April 1, 2006, and December 31, 2007, with an abnormal cardiac troponin (troponin positive [TP]) were compared to a troponin-negative (TN) cohort matched for age, sex, and primary discharge diagnosis. Outcomes were obtained by linking with a regional ED and a provincial vital statistics database and adjusted for the following: estimated glomerular filtration rate, do-not-resuscitate status, history of coronary artery disease, Canadian Triage and Acuity Scale, and left ventricular hypertrophy on electrocardiography. The primary outcome was a composite of death or admission to hospital within 1 year.

RESULTS

Our total cohort (n  =  344) consisted of 172 TP and 172 TN patients. In the univariate analysis, TP patients had a higher rate of the primary outcome (OR 3.2, 95% CI 2.1-5.0, p < 0.001) and both of its components (p < 0.001). After adjusting for covariates, positive troponin remained an independent predictor of the primary outcome (OR 2.1, 95% CI 1.3-3.4, p  =  0.005) and inpatient admission (OR 2.0, 95% CI 1.2-3.4, p  =  0.006). There was no significant difference in death (OR 1.3, 95% CI 0.6-2.9, p  =  0.5) after adjustment.

CONCLUSIONS

A positive troponin assay during ED stay in discharged patients is an independent marker for risk of subsequent admission. Our findings suggest that the prognostic power of an abnormal troponin extends to patients discharged from the ED.

The global need to define normality: the 99th percentile value of cardiac troponin

BACKGROUND

How to select a presumably normal population for the establishment of 99th percentile cutoffs for cardiac troponin assays has not been adequately addressed. Lack of attention to this question can result in misleading medical decision cutoffs.

CONTENT

From our review of the peer-reviewed literature, including international recommendations, no uniform procedure is followed and no uniform guideline has been published by experts or regulatory agencies to guide researchers or manufacturers of cardiac troponin assays in their quest to define the health or "normality" of a reference population that is used to establish an accurate 99th percentile value. As we progress globally into the era of high-sensitivity cardiac troponin assays, we propose several suggested approaches to define presumably normal individuals by use of clinical and biomarker surrogates.

SUMMARY

Our uniform approach to defining who is normal and who may not be normal will help to define diagnostic and risk outcomes assessments in the management of patients with suspected myocardial injury, both for use in current clinical practice and clinical research, as well as for the potential future use of cardiac troponin in primary prevention.

Novel biomarkers for risk stratification and identification of life-threatening cardiovascular disease: troponin and beyond

Chest pain and other symptoms that may represent acute coronary syndromes (ACS) are common reasons for emergency department (ED) presentations, accounting for over six million visits annually in the United States [1]. Chest pain is the second most common ED presentation in the United States. Delays in diagnosis and inaccurate risk stratification of chest pain can result in serious morbidity and mortality from ACS, pulmonary embolism (PE), aortic dissection and other serious pathology.

Because of the high morbidity, mortality, and liability issues associated with both recognized and unrecognized cardiovascular pathology, an aggressive approach to the evaluation of this patient group has become the standard of care. Clinical history, physical examination and electrocardiography have a limited diagnostic and prognostic role in the evaluation of possible ACS, PE, and aortic dissection, so clinicians continue to seek more accurate means of risk stratification. Recent advances in diagnostic imaging techniques particularly computed-tomography of the coronary arteries and aorta, have significantly improved our ability to diagnose life-threatening cardiovascular disease.

In an era where health care utilization and cost are major considerations in how disease is managed, it is crucial to risk-stratify patients quickly and efficiently. Historically, biomarkers have played a significant role in the diagnosis and risk stratification of several cardiovascular disease states including myocardial infarction, congestive heart failure, and pulmonary embolus. Multiple biomarkers have shown early promise in answering questions of risk stratification and early diagnosis of cardiovascular pathology however many do not yet have wide clinical availability. The goal of this review will be to discuss these novel biomarkers and describe their potential role in direct patient care.

Cardiac troponin-T and CK-MB (mass) levels in cardiac and non cardiac disease

Serum cardiac troponin T (cTnT) and CKMB (mass) were analysed in three groups of patients. The first group (n=32) were patients with acute coronary syndromes including myocardial infarction. The second group (n=35)were patients with hypertension. The third group (n=24) were patients who had succumbed to non cardiac diseases. In all 3 groups, cardiac troponin T was elevated when compared with controls (p<0.001). However, CKMB elevation was not significant in all groups. CKMB levels correlated well with troponin T levels only when CKMB was greater than 50 ng/ml (r=1.00). Small elevations of troponin T identifies minimal cardiac necrosis and patients can benefit from early invasive therapy.

Troponin-Specific Autoantibody Interference in Different Cardiac Troponin I Assay Configurations

BACKGROUND

Autoantibodies to cardiac troponins (cTnAAb) can interfere with the measurement of cardiac troponin I (cTnI) by immunoassays. The aim of this study was to explore the degree of cTnAAb interference in different cTnI assay configurations.

METHODS

Ternary troponin complex was added into samples (serum or plasma, n = 132, 68% cTnAAb positive) from individuals without known cardiac conditions. The recovery of cTnI was then measured with 6 investigational cTnI assays (2, 3, or 4 antibodies per assay). Three of these assays were then selected for further comparison by use of samples (plasma, n = 210, 33% cTnAAb positive) from non–ST-elevation acute coronary syndrome patients in the FRISC-II (FRagmin/Fast Revascularisation during InStability in Coronary artery disease) cohort. Finally, these results were compared to those obtained with 3 commercial cTnI assays.

RESULTS

Analytical recoveries varied widely among the 6 investigational assays. Notably the low recoveries (median 9%) of the midfragment-targeting reference assay were normalized (median 103%) with the use of the 4-antibody assay construct (3 capture, 1 tracer antibody) with only 1 antibody against a midfragment epitope. Reduced analytical recoveries correlated closely with measured autoantibody amounts. cTnI concentrations from cTnAAb-positive patient samples determined with 3 investigational assays confirmed the reduced concentrations expected from the low analytical recoveries. The results from the commercial cTnI assays with antibody selections representative for contemporary assay constructs revealed a similar underestimation (up to 20-fold) of cTnI in cTnAAb-positive samples.

CONCLUSIONS

A novel cTnI assay deviating from the conventional IFCC-recommended midfragment approach substantially improves cTnI detection in samples containing cTnAAbs.

Cardiac biomarkers are associated with an increased risk of stroke and death in patients with atrial fibrillation: a Randomized Evaluation of Long-term Anticoagulation Therapy (RE-LY) substudy

BACKGROUND

Cardiac biomarkers are strong predictors of adverse outcomes in several patient populations. We evaluated the prevalence of elevated troponin I and N-terminal pro-B-type natriuretic peptide (NT-proBNP) and their association to cardiovascular events in atrial fibrillation (AF) patients in the Randomized Evaluation of Long-Term Anticoagulation Therapy (RE-LY) trial.

METHODS AND RESULTS

Biomarkers at randomization were analyzed in 6189 patients. Outcomes were evaluated by Cox proportional hazards models adjusting for established cardiovascular risk factors and the CHADS(2) and CHA(2)DS(2)-VASc risk scores. Patients were stratified based on troponin I concentrations: <0.010 μg/L, n=2663; 0.010 to 0.019 μg/L, n=2006; 0.020 to 0.039 μg/L, n=1023; ≥0.040 μg/L, n=497; and on NT-proBNP concentration quartiles: <387; 387 to 800; 801 to 1402; >1402 ng/L. Rates of stroke were independently related to levels of troponin I with 2.09%/year in the highest and 0.84%/year in the lowest troponin I group (hazard ratio [HR], 1.99 [95% CI, 1.17-3.39]; P=0.0040), and to NT-proBNP with 2.30%/year versus 0.92% in the highest versus lowest NT-proBNP quartile groups, (HR, 2.40 [95% CI, 1.41-4.07]; P=0.0014). Vascular mortality was also independently related to biomarker levels with 6.56%/year in the highest and 1.04%/year the lowest troponin I group (HR, 4.38 [95% CI, 3.05-6.29]; P<0.0001), and 5.00%/year in the highest and 0.61%/year in the lowest NT-proBNP quartile groups (HR, 6.73 [3.95-11.49]; P<0.0001). Biomarkers increased the C-statistic from 0.68 to 0.72, P<0.0001, for a composite of thromboembolic events.

CONCLUSIONS

Elevations of troponin I and NT-proBNP are common in patients with AF and independently related to increased risks of stroke and mortality. Cardiac biomarkers seem useful for improving risk prediction in AF beyond currently used clinical variables.

Cardiac biomarkers in acute myocardial infarction

Each year, a large number of patients are seen in the Emergency Department with presentations necessitating investigation for possible acute myocardial infarction. Patients can be stratified by symptoms, risk factors and electrocardiogram results but cardiac biomarkers also have a prime role both diagnostically and prognostically. This review summarizes both the history of cardiac biomarkers as well as currently available (established and novel) assays. Cardiac troponin, our current "gold standard" biomarker criterion for the diagnosis of myocardial infarction has high sensitivity and specificity for this diagnosis and therapies instituted in patients with elevated troponin have been shown to influence outcomes. Other markers of myocardial necrosis, inflammation and neurohormonal activity have also been shown to have either diagnostic or prognostic utility, but none have been shown to be superior to troponin. The measurement of multiple biomarkers and the use of point of care markers may accelerate current diagnostic protocols for the assessment of such patients.

Early dynamic change in high-sensitivity cardiac troponin T in the investigation of acute myocardial infarction

BACKGROUND

The definition of acute myocardial infarction (AMI) requires a rise and/or fall in troponin with 1 or more results ≥99th percentile of the reference range. How much troponin must change has not been specified. We ascertained whether dynamic changes (δ) in high-sensitivity troponin T (hs-TnT) improved diagnostic and prognostic test performance in the emergency department.

METHODS

We recruited 939 patients with symptoms suggestive of acute coronary syndrome (without ST elevation). hs-cTnT was measured at 0 h and 2 h after presentation. End-points were admission diagnosis of AMI and 1-year adverse events (composite of death, AMI, revascularization).

RESULTS

Diagnostic specificity of 0-2-h hs-cTnT for AMI (incurred by 200 patients) improved from 79.8% (78.8%-80.5%) by using the 99th percentile alone to 94.2% (92.9%-95.4%) when we also included a δ ≥20%, but diagnostic sensitivity decreased from 94.5% (90.7%-96.9%) to 49.5% (44.6%-53.9%). With the inclusion of those patients with a δ ≥20% when 0-2-h hs-cTnT was <99th percentile, in addition to any with concentrations ≥99th percentile, diagnostic sensitivity increased to 97.5% (94.4%-98.9%). hs-cTnT ≥99th percentile predicted adverse events (incurred by 111 patients), adjusted hazard ratio 1.9 (1.2-2.8), whereas a δ ≥20% did not, hazard ratio 1.1 (0.7-1.7).

CONCLUSIONS

Diagnostic specificity of hs-cTnT improved with the use of a δ ≥20% in those patients with concentrations ≥99th percentile, but at a cost of a large reduction in sensitivity. Diagnostic sensitivity improved with the use of a δ ≥20% in patients with 0-2-h concentrations <99th percentile. Both approaches may be required for optimum rule-in and rule-out strategies, respectively. The δ criteria seem to be less useful for medium-term risk stratification.

High-sensitivity versus conventional troponin in the emergency department for the diagnosis of acute myocardial infarction

Introduction

Recently, newer assays for cardiac troponin (cTn) have been developed which are able to detect changes in concentration of the biomarker at or below the 99th percentile for a normal population. The objective of this study was to compare the diagnostic performance of a new high-sensitivity troponin T (HsTnT) assay to that of conventional cTnI for the diagnosis of acute myocardial infarction (AMI) according to pretest probability (PTP).

Methods

In consecutive patients who presented to our emergency departments with chest pain suggestive of AMI, levels of HsTnT were measured at presentation, blinded to the emergency physicians, who were asked to estimate the empirical PTP of AMI. The discharge diagnosis was adjudicated by two independent experts on the basis of all available data.

Results

A total of 317 patients were included, comprising 149 (47%) who were considered to have low PTP, 109 (34%) who were considered to have moderate PTP and 59 (19%) who were considered to have high PTP. AMI was confirmed in 45 patients (14%), 22 (9%) of whom were considered to have low to moderate PTP and 23 (39%) of whom were considered to have high PTP (P < 0.001). In the low to moderate PTP group, HsTnT levels ≥ 0.014 μg/L identified AMI with a higher sensitivity than cTnI (91%, 95% confidence interval (95% CI) 79 to 100, vs. 77% (95% CI 60 to 95); P = 0.001), but the negative predictive value was not different (99% (95% CI 98 to 100) vs. 98% (95% CI 96 to 100)). There was no difference in area under the receiver operating characteristic (ROC) curve between HsTnT and cTnI (0.93 (95% CI 0.90 to 0.98) vs. 0.94 (95% CI 0.88 to 0.97), respectively).

Conclusions

In patients with low to moderate PTP of AMI, HsTnT is slightly more useful than cTnI. Our results confirm that the use of HsTnT has a higher sensitivity than conventional cTnI.

High sensitivity troponin outperforms contemporary assays in predicting major adverse cardiac events up to two years in patients with chest pain

Background

Previous studies have shown a risk of subsequent major adverse cardiovascular events (MACEs) in patients with suspected acute coronary syndromes (ACSs) and elevated cardiac troponin. The aim of this study was to compare prognostic utility of high-sensitivity troponin with contemporary troponin assays in such patients.

Methods

In total, 332 patients with suspected ACS were investigated between November 2006 and April 2007; all were followed for two years. Blood samples were analysed to compare Roche Elecsys high-sensitivity troponin T (hsTnT), Abbott Architect troponin I 3rd generation (TnI 3) and Roche Elecsys troponin T (TnT), for the prediction of MACE (composite of cardiovascular death, non-fatal myocardial infarction and revascularization).

Results

Sixty-eight patients (20.5%) experienced MACE between discharge and two years. Receiver operating characteristic (ROC) curve derived area under the ROC curve (95% confidence intervals) for baseline hsTnT were 0.70 (0.63–0.76), TnI 3 0.66 (0.59–0.73) and TnT 0.61 (0.53–0.69). hsTnT ( P = 0.001) was superior to TnT and TnI 3 trended ( P = 0.094) to superiority but were equivalent to each other. hsTnT best stratified patients with cumulative event rates for two-year MACE of 35.6% for levels ≥99th percentile, 17.9% for levels between the limit of detection (LOD) and 99th percentile and 5.4% for levels <LOD compared with TnI 3: 33.0%, 31.1% and 10.9%, respectively. TnT had MACE rates of 36.7% when ≥99th percentile and 15.4% when <99th percentile (=LOD).

Conclusions

hsTnT outperformed contemporary TnI and TnT assays for the prediction of MACE at two years. Those with levels below the LOD for hsTnT identified a group of patients at very low risk for adverse events.

Troponin elevation in coronary vs. non-coronary disease

Acute myocardial infarction is defined as myocardial cell death due to prolonged myocardial ischaemia. Cardiac troponins (cTn) are the most sensitive and specific biochemical markers of myocardial injury and with the new high-sensitivity troponin methods very minor damages on the heart muscle can be detected. However, elevated cTn levels indicate cardiac injury, but do not define the cause of the injury. Thus, cTn elevations are common in many disease states and do not necessarily indicate the presence of a thrombotic acute coronary syndrome (ACS). In the clinical work it may be difficult to interpret dynamic changes of troponin in conditions such as stroke, pulmonary embolism, sepsis, acute perimyocarditis, Tako-tsubo, acute heart failure, and tachycardia. There are no guidelines to treat patients with elevated cTn levels and no coronary disease. The current strategy of treatment of patients with elevated troponin and non-acute coronary syndrome involves treating the underlying causes. The aim of this paper is to review data from studies of non-ACS patients with acutely elevated troponin who in clinical practice may be difficult to discriminate from ACS patients.

Early and late outcome prediction of death in the emergency room setting by point-of-care and laboratory assays of cardiac troponin I

BACKGROUND

Point-of-care (POC) assays of cardiac troponins are common in the emergency department setting. The question raised was as follows: What is the clinical impact of the results of POC assays of cardiac troponins as compared with sensitive laboratory assays?

METHODS

Patients admitted consecutively to the emergency department (N = 1,069) and on whom cardiac troponins were requested as part of their clinical work-up were included. Cardiac troponin I (cTnI) was measured by the POC assays-i-Stat (Abbott Diagnostics, Abbott Park, IL) and Stratus CS (Siemens Healthcare Diagnostics, Deerfield, IL)-and by the laboratory assays-Access AccuTnI (Beckman Coulter, Fullerton, CA) and Architect cTnI (Abbott Diagnostics). Results were related to early (14 days) and late outcome (median 3.3 months, range 0.1-35) as to death.

RESULTS

The laboratory assays identified more patients (P < .001) with elevated levels than the two POC assays (39%-74% vs 20%-27%). Adopting the 99th percentiles upper reference limit, the Access AccuTnI identified 88% and Architect cTnI identified 81% of all patients who died of cardiovascular disease as compared with 50% and 54% for i-Stat and Stratus CS, respectively (P < .001). Negative predictive values for the laboratory assays were 97% as compared with 89% to 93% for the POC assays. Negative likelihood ratios were 0.25 (CI 0.15-0.041) and 0.59 to 0.68 (CI 0.47-0.79), respectively.

CONCLUSIONS

The current POC cTnI assays are less sensitive for outcome prediction of patients with myocardial injury. The clinical judgment of the patient with suspected myocardial ischemia should not solely rely on results from POC assays. If a clinical suspicion of myocardial injury remains despite negative cTnI results with the POC assays, such results should be complemented by results from sensitive laboratory assays.

The utility of troponin measurement to detect myocardial infarction: review of the current findings

Myocardial infarction (MI) is defined by the presence of myocardial necrosis in combination with clinical evidence of myocardial ischemia. Cardiac troponins are regulatory proteins within the myocardium that are released into the circulation when damage to the myocyte has occurred. Therefore, serum troponin is an exquisitely sensitive marker of myocardial injury and is necessary for establishing the diagnosis of MI. High-sensitivity troponin assays are improving the diagnostic accuracy and rapid detection of myocardial infarction. The early identification of MI is vital for the institution of anti-thrombotic therapy to limit myocardial damage and preserve cardiac function. Troponin has both diagnostic and prognostic significance in the setting of acute coronary syndrome (ACS). Increased troponin levels in the absence of ACS should prompt an evaluation for an alternative, non-thrombotic mechanism of troponin elevation and direct management at the underlying cause. This review describes the role of troponin in the evaluation of patients with suspected myocardial infarction.

The new high-sensitivity cardiac troponin T assay improves risk assessment in acute coronary syndromes

BACKGROUND

Cardiac troponins are currently the markers of choice for diagnosis of acute myocardial infarction and risk assessment in acute coronary syndrome (ACS). With the introduction of the new high-sensitivity cardiac troponin T (hs-cTnT) assay, it has become possible to measure cTnT even in healthy subjects. However, how the hs-cTnT assay compares with the old cTnT assay for risk assessment in ACS is still unknown.

METHODS

Cardiac troponin T levels were measured with the new hs-cTnT assay and the old third-generation cTnT assay in serum samples collected 48 hours after randomization in 1,452 randomly selected ACS patients enrolled in the GUSTO-IV trial. During 30 days of follow-up, deaths and myocardial infarctions were recorded. At 12 months, only all-cause mortality was collected.

RESULTS

The 16% of the patients that had levels higher than the 99th percentile cutoff for hs-cTnT but less than for cTnT had a similar 1-year mortality as the 60% that were positive for both assays (9.2% vs 10.7%, P = .52) and a higher 1-year mortality compared with the 24% that were negative for both assays (9.2% vs 2.6%, P = .001). For death or acute myocardial infarction at 30 days, the group that was positive only for hs-cTnT had an intermediate risk compared with the groups negative or positive for both assays (2.4%, 5.2%, and 8.7%; P < .001).

CONCLUSION

The new hs-cTnT assay, compared with the old cTnT assay, identified more patients with myocardial damage and who were at an increased risk for new cardiac events.

Troponins and high-sensitivity troponins as markers of necrosis in CAD and heart failure

For years, cardiac troponins (cTn) have been regarded as the preferred biomarkers for the diagnosis of myocardial infarction and for the risk stratification of patients with acute coronary syndromes, as well as for the selection of patients who need an early invasive strategy, and for the guidance of adjunctive pharmacological therapy. In addition, measurement of cTn has been found useful for detection of myocardial necrosis in conditions unrelated to myocardial ischemia including acute pulmonary embolism, myocarditis, heart failure, sepsis, and end-stage renal disease. In these conditions, an unfavorable prognosis is unequivocally associated with detectable concentrations of cTn.A major limitation of most currently available cTn assays is the lack of adequate precision, i.e., to measure cTn concentrations at the 99th percentile value with a coefficient of variation < 10%. As a consequence, many manufacturers have developed more sensitive cTn assays that now comply with precision criteria required by the Joint European Society of Cardiology/ American College of Cardiology/American Heart Association/World Heart Federation Task Force for the Redefinition of Acute Myocardial Infarction.Using assays with higher analytic sensitivity more patients will be seen in clinical practice with the high-sensitivity cardiac troponin T (TnThs) above the 99th percentile discriminator. The causes of these elevations may be due to acute, subacute and chronic cardiac disease such as heart failure or cardiomyopathies.

High-sensitivity troponin T concentrations in acute chest pain patients evaluated with cardiac computed tomography

BACKGROUND

For evaluation of patients with chest pain and suspected acute coronary syndrome (ACS), consensus guidelines recommend use of a cardiac troponin cut point that corresponds to the 99 th percentile of a healthy population. Most conventional troponin methods lack sufficient precision at this low level.

METHODS AND RESULTS

In a cross-sectional study, 377 patients (mean age 53.7 years, 64.2% male) with chest pain and low to intermediate likelihood for ACS were enrolled in the emergency department. Blood was tested with a precommercial high-sensitivity troponin T assay (hsTnT) and compared with a conventional cardiac troponin T method. Patients underwent a 64-slice coronary computed tomography coronary angiogram at the time of phlebotomy, on average 4 hours from initial presentation. Among patients with acute chest pain, 37 (9.8%) had an ACS. Using the 99th percentile cut point for a healthy population (13 pg/mL), hsTnT had 62% sensitivity, 89% specificity, 38% positive predictive value, and 96% negative predictive value for ACS. Compared with the cardiac troponin T method, hsTnT detected 27% more ACS cases (P=.001), and an hsTnT above the 99 th percentile strongly predicted ACS (odds ratio 9.0, 95% confidence interval 3.9 to 20.9, P<0.001). Independent of ACS diagnosis, computed tomography angiography demonstrated that concentrations of hsTnT were determined by numerous factors, including the presence and severity of coronary artery disease, left ventricular mass, left ventricular ejection fraction, and regional left ventricular dysfunction.

CONCLUSIONS

Among low- to intermediate-risk patients with chest pain, hsTnT provides good sensitivity and specificity for ACS. Elevation of hsTnT identifies patients with myocardial injury and significant structural heart disease, irrespective of the diagnosis of ACS.

Clinical applications of highly sensitive troponin assays

Cardiac troponin is the biomarker of choice for the diagnosis of acute myocardial infarction. Recent consensus recommendations have adopted a concentration of troponin above the 99th percentile of a healthy population to diagnose myocardial infarction. Until recently, there was no assay capable of achieving recommended precision; however, with the development of "highly sensitive" troponin assays, it is now possible to accurately measure troponin concentrations at and below the current 99th percentile of a healthy population. These assays have enormous potential in not only identifying more patients with acute myocardial infarction, and providing superior risk prediction in those so afflicted, in addition highly sensitive troponins assays may be useful for long-term risk assessment of the patient with coronary disease. In this article, we will review the clinical applications, novel concepts, challenges, and limitations of using highly sensitive troponins assays.

Prevalence and prognostic significance of incidental cardiac troponin T elevation in ambulatory patients with stable coronary artery disease: data from the Heart and Soul study

BACKGROUND

The significance of troponin elevation and clinical utility of troponin testing in ambulatory patients with coronary artery disease (CAD) have not been examined. We sought to investigate the prevalence and prognostic value of cardiac troponin T (cTnT) elevation in a population with stable CAD.

METHODS

We studied 987 patients with stable CAD enrolled in the Heart & Soul study who had plasma cTnT measurements before performing exercise treadmill testing.

RESULTS

Of the studied population, 58 patients or 6.2% had detectable cTnT levels, >or=0.01 ng/mL (0.01-0.72 ng/mL). During a mean follow-up period of 4.3 (0.1-6.5) years, 58.6% of participants with detectable cTnT had cardiovascular events compared with 22.5% of those without detectable cTnT (hazard ratio [HR] 3.8, 95% CI 2.6-5.4, P < .001). This association remained strong after adjustment for traditional risk factors and C-reactive protein (HR 2.0, 95% CI 1.3-3.1, P = .002). However, after further adjustment for N-terminal pro-B-type natriuretic peptide and echocardiographic parameters of left ventricular function, cTnT elevation was not an independent predictor of cardiovascular events (HR 1.3, 95% CI, 0.8-2.3, P = .28).

CONCLUSIONS

In ambulatory patients with stable CAD, the prevalence of cTnT elevation was 6.2%. Cardiac troponin T elevation detected using the conventional troponin assay was associated with increased risk of adverse cardiovascular outcomes, but its prognostic value was not incremental over N-terminal pro-B-type natriuretic peptide and echocardiographic evidence of cardiac abnormalities.

Biochemical diagnosis of myocardial infarction evolves towards ESC/ACC consensus: Experiences from the Nordic countries

OBJECTIVES

To investigate the diagnostic approach in Nordic hospitals receiving patients suspected of acute myocardial infarction (MI), especially focusing on implementation of the recently proposed criteria by the European Society of Cardiology (ESC) and the American College of Cardiology (ACC) for the definition of MI.

DESIGN

A survey with questionnaires of the diagnostic approach was conducted among all relevant departments (220) in the Nordic countries.

RESULTS

Seventy-six percent (167) of hospitals responded. Troponins I and T (TnI and TnT) and creatinine kinase monobasic fraction (mass concentration) (CKMB(mass)) covered 93 and 65% of hospitals, respectively. Of troponin users, 34% indicated use of TnI vs 66% using TnT. Sporadic use of AST, CK, LD and myoglobin was reported. There was a tendency to lower cut-off levels in Sweden and Finland. Among troponin assays, there was considerable heterogeneity regarding cut-off levels.

CONCLUSIONS

The Nordic countries are approaching ESC/ACC consensus on cardiac markers. Compared with previous national surveys (1995-1999), there is a shift towards the use of troponins. However, differences in cut-off levels of troponin emphasize the need for harmonization of assays.

Diagnosis and Management of Patients with Suspected Acute Myocardial Infarction

Patients admitted with suspected acute myocardial infarction (MI) constitute a diagnostic, prognostic and therapeutic challenge for the treating physician. Elevation of a marker of myocardial necrosis together with ischemic symptoms and/or ischemic ECG changes are mandatory for the diagnosis of acute MI. Troponin T or I is the preferred marker of myocardial necrosis. The diagnostic process should start as soon as possible. The introduction of prehospital ECG recordings and prehospital administration of thrombolytic treatment in case of ST-segment elevation MI, have been shown to decrease the time from onset of symptoms till treatment considerably, which also translates into saved lives. In contrast, data of the value of prehospital analyses of biochemical markers are still limited. In patients without ST-segment elevation on admission the diagnosis is dependent on repeated measurements of markers of myocardial damage, which together with other biochemical markers (e.g. CRP and BNP/NT-proBNP) also are useful for risk assessment. Patients identified to be at low risk of future cardiac events might be discharged early and, on the contrary, a more intense treatment might be started in patients identified to be at high risk. An elevated troponin concentration is shown to identify patients who benefit from antithrombotic therapy and invasive procedures. Several different risk scoring models based on a combination of clinical variables, ECG-changes and biochemical markers, have been shown to further improve risk assessment and selection of treatment.

Clinical Performance of Two Highly Sensitive Cardiac Troponin I Assays

Background: The aim of this study was to compare the clinical performance of 2 sensitive cTnI assays with 10% CV imprecision below the 99th percentile upper reference limit.

Methods: We measured cardiac troponin and N-terminal pro-brain natriuretic peptide (NT-proBNP) concentrations in a random sample of the Global Use of Strategies To Open Occluded Coronary Arteries (GUSTO) IV cohort (n = 1251). Outcome data of 1-year mortality and the composite endpoint DMI [death and/or myocardial infarction (MI) within 30 days] were available in all patients. The 99th percentile of a healthy population was estimated from the Sweden Women and Men and Ischemic Heart Disease (SWISCH) cohort (n = 442). We measured cardiac troponin I (cTnI) using the Access AccuTnI (Beckman Coulter) and Centaur TnI Ultra (Siemens Healthcare Diagnostics) and NT-proBNP using the Elecsys 2010 (Roche Diagnostics).

Results: Applying the 10% CV cutoff, the sensitivity of the Access AccuTnI assay in identifying DMI and death was higher than that of the Centaur TnI Ultra (P = 0.02 and P &lt; 0.001), and the AccuTnI assay also identified more patients at risk (P &lt; 0.001) and with poor outcome. Applying the 99th percentile cutoffs, AccuTnI identified more patients at risk than the Centaur TnI (P &lt; 0.001) and with significant differences in outcome. Significantly more patients with cardiac troponins below the cutoffs as measured by Centaur TnI had increased NT-proBNP concentrations (P &lt; 0.001) compared with AccuTnI.

Conclusions: The AccuTnI assay identified more patients at risk than the Centaur cTnI Ultra assay. Our results demonstrate the clinical potential of high-sensitivity cardiac troponin assays for the identification of patients at risk of dying from cardiovascular disease.

Present and Future Biochemical Markers for Detection of Acute Coronary Syndrome

The use of biochemical markers in the diagnosis and management of patients with acute coronary syndrome has increased continually in recent decades. The development of highly sensitive and cardiac-specific troponin assays has changed the view on diagnosis of myocardial infarction and also extended the role of biochemical markers of necrosis into risk stratification and guidance for treatment. The consensus definition of myocardial infarction places increased emphasis on cardiac marker testing, with cardiac troponin replacing creatine kinase MB as the "gold standard" for diagnosis of myocardial infarction. Along with advances in the use of more cardiac-specific markers of myocardial necrosis, biochemical markers that are involved in the progression of atherosclerotic plaques to the vulnerable state or that signal the presence of vulnerable plaques have recently been identified. These markers have variable abilities to predict the risk of an individual for acute coronary syndrome. The aim of this review is to provide an overview of the well-established markers of myocardial necrosis, with a special focus on cardiac troponin I, together with a summary of some of the potential future markers of inflammation, plaque instability, and ischemia.

Frequency of elevations in markers of cardiomyocyte damage in otherwise healthy newborns

Myocardial damage in infancy is a risk factor for eventual cardiac disease. Given that myocardial stress is greatest during the perinatal period and that the neonatal period is when most pediatric heart failure occurs, the aim of this study was to determine whether even otherwise healthy neonates might have subclinical myocardial damage and, if so, what characteristics might identify them. Umbilical cord and neonatal serum samples from 32 normal neonates were assayed for biomarkers of myocardial injury. No neonate had clinical evidence of cardiac or other abnormalities. Serum cardiac troponin T was elevated in 19 of 25 cords (76%) and in 16 of 17 neonates (94%); levels indicating myocardial infarction (> or =0.2 ng/ml) were found in 2 patients (1 umbilical cord and 1 neonatal sample). Creatine kinase-MB was elevated in 6 of 16 cords (38%) and in 8 of 15 neonates (53%). Cardiac troponin I was elevated in 11% and 17% of samples, myoglobin in 4% and 17%, and high-sensitivity C-reactive protein in 9% and 40%. Measures of myocardial injury were associated with longer hospitalization (r = 0.50, p = 0.04), non-Caucasian race (p = 0.012), lower birth weights (p = 0.014), positive maternal cervical cultures (r = 0.41, p = 0.046), and elevated high-sensitivity C-reactive protein (r = 0.66, p = 0.005). In conclusion, clinically occult myocardial injury appears to occur in some healthy newborns, although whether it is pathologic or not remains to be determined.

Cardiovascular biomarkers: increasing impact of laboratory medicine in cardiology practice

The practice of cardiology is in continual evolution, in parallel with the progress achieved by medical research in understanding the pathophysiology of cardiovascular disease and in developing new therapeutic procedures. Consequently, manufacturers of cardiac biomarkers are pressed with new demands to improve the performance of the existing and the development of novel ones. Several highly sensitive and/or specific assays for myocardial ischemic damage and myocardial function detection have already become commercially available. Moreover, an increasing number of novel risk factors have been added to the classical risk factors of cardiovascular disease. Finally, the recent surge of genetic analysis procedures will likely soon provide the clinical cardiologist with a number of laboratory tests for defining the molecular diagnosis, assessing new risk factors, and better targeting the pharmaceutical approaches in patients with cardiovascular disease. In this review, we first present the general characteristics of a biomarker followed by the analytical and clinical performance of assay methods.

Highly Sensitive Cardiac Troponin T Values Remain Constant after Brief Exercise- or Pharmacologic-Induced Reversible Myocardial Ischemia

Background: Using a new precommercial high-sensitivity cardiac troponin T (hsTnT) assay, we evaluated whether hsTnT increases after reversible myocardial ischemia.

Methods: In 195 patients undergoing nuclear stress testing (ST) using single-photon emission computed tomography (SPECT) for suspected ischemic heart disease, we measured hsTnT before and 18 min, 4 h, and 24 h after the stress test. Thirty patients were excluded before ST because of cardiac troponin T (cTnT) &gt;30 ng/L (0.03 μg/L) as measured by the fourth-generation commercial test. Another 65 patients were excluded because of a combination of fixed and reversible perfusion defects (PDs) after SPECT.

Results: We studied 18 patients with reversible PDs, 41 patients with fixed PDs, and 41 patients without any PDs. Of these 100 patients, 61 received dynamic ST and 39 pharmacological ST. Median baseline hsTnT concentrations (25th, 75th percentile) were comparable in patients with reversible, fixed, and no PDs [5.57 (2.47, 12.60), 8.01 (4.55, 12.44), and 6.90 (4.63, 10.59) ng/L, respectively]. After ST, median hsTnT concentrations did not change in the reversible, fixed, or no PD groups from baseline to 18 min [−0.41 (−0.81, 0.01), 0.01 (−0.75, 0.79), and 0.36 (−0.42, 1.01) ng/L] or from baseline to 4 h [−0.56 (−1.82, 0.74), 0.24 (−0.60, 1.45), and 0.23 (−0.99, 1.15) ng/L]. Median baseline hsTnT concentrations tended to be higher in patients undergoing pharmacological vs dynamic ST; however, there were no significant increases in hsTnT concentrations after either type of ST.

Conclusions: Elevation of cTnT is rather a consequence of irreversible myocyte death than reversible myocardial ischemia after exercise or pharmacologic myocardial ischemia.

The determination of the 99th centile level for troponin assays in an Australian reference population

Background

Current guidelines for the diagnosis and risk assessment of patients presenting with myocardial infarction recommend a single decision cut-off point for cardiac troponin (cTn) based on the 99th centile of a reference population. The 99th centile level for eight troponin assays was determined in an apparently cardio-healthy Australian reference population.

Methods

Nine laboratories measured troponin in serum and plasma collected from 111 reference individuals. An imprecision profile was determined using up to 10 serum samples analysed on 10 separate days. Method comparison using 100 routinely tested plasma samples was performed to estimate method concordance.

Results

Generally 99th centile values determined in this study were lower than, or the same as manufacturers' levels, except for cTnI by Architect (0.020 vs. 0.012 μg/L), and imprecision at the 99th centile was 20% coefficient of variation (CV) or higher. Troponin concentrations at 10% CV were greater than those quoted in the manufacturer's package insert except by AxSYM, 0.06 vs. 0.16 μg/L cTnI, and by E-170, 0.02 vs. 0.03 μg/L cTnT. In the method comparison 74, 70, 65, 75, 58, 66, 58 and 77 samples measured by Access, Architect, AxSYM, Centaur, Dimension RxL, E-170, i-STAT and Vitros ECi assays, respectively, had troponin concentrations above the study 99th centile.

Conclusions

Depending on the selected reference population for troponin, there is likely to be variability in the 99th centile as shown in this study. Some differences in sample concordance at the 99th centile cut-off were observed between cTn methods and may result in different clinical classification.