Risk stratification with a point-of-care cardiac troponin T test in acute myocardial infarction. GUSTOIII Investigators. Global Use of Strategies To Open Occluded Coronary Arteries

Premorbid levels of high-sensitivity cardiac troponin T and natriuretic peptide and prognosis after incident myocardial infarction

High-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) at the time of myocardial infarction (MI) are strong predictors of prognosis. However, whether their premorbid (before MI occurrence) levels are associated with prognosis after incident MI is unknown.

METHODS

In 1,054 participants from the Atherosclerosis Risk in Communities Study with incident MI, we evaluated premorbid levels of hs-cTnT and NT-proBNP measured on median 5.8 (interquartile interval 3.0-11.5 [mean 5.5]) years prior to incident MI and their associations with subsequent composite and individual outcomes of all-cause mortality, cardiovascular mortality, recurrent MI, heart failure, and stroke.

RESULTS

During a median follow-up of 3.0 years after MI, 801 participants developed the composite outcome. Both hs-cTnT and NT-proBNP were independently associated with the composite outcome after incident MI. Among individual outcomes, all-cause mortality, cardiovascular mortality, and heart failure showed significant associations with both cardiac markers. Overall, NT-proBNP demonstrated a more evident relationship than hs-cTnT. Indeed, the addition of premorbid NT-proBNP alone, but not hs-cTnT alone, to conventional predictors at incident MI significantly improved risk prediction of the composite outcome after incident MI (Δc-statistic 0.013 [95% CI 0.005-0.022] from 0.691 with conventional predictors).

CONCLUSIONS

Premorbid levels of hs-cTnT and NT-proBNP assessed on average 6 years prior to incident MI were associated with adverse outcomes after incident MI. These results further highlight the importance of cardiac health at an earlier stage of life.

Relationship Between Troponin on Presentation and In-Hospital Mortality in Patients With ST-Segment-Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention

Background Troponin release in ST-segment-elevation myocardial infarction (STEMI) has predictable kinetics with early levels reflective of ischemia duration. Little research has examined the value of admission troponin levels in STEMI patients undergoing primary percutaneous coronary intervention. We investigated the relationship between troponin on presentation and mortality in a large, real-world cohort of STEMI patients undergoing primary percutaneous coronary intervention. Methods and Results We used multivariable adaptive regression modeling to examine the association between admission troponin levels and in-hospital mortality for patients who underwent primary percutaneous coronary intervention for STEMI. We adjusted for known clinical risk factors using a validated mortality risk model derived from the NCDR (National Cardiovascular Data Registry) CathPCI database, and this same model was used to calculate patients' predicted mortality based on clinical and demographic factors. Patients were then stratified by troponin groups to compare predicted versus observed mortality. Of the 14 061 patients included in the cohort, 47.2% had initial troponin levels that were undetectable or within the reference range. Admission troponin was an independent predictor of in-hospital mortality, and any value above the reference range was associated with increased mortality (1.8% versus 5.1%, [standardized difference, 18.2%]). Patients with the highest predicted risk for mortality (13% predicted) in the highest admission troponin grouping experienced an observed mortality of 19.5%. Patients in low troponin groupings consistently demonstrated lower than predicted mortality based on their clinical and demographic risk profile. Conclusions Nearly half of patients undergoing primary percutaneous coronary intervention had normal troponin on presentation and had a relatively good outcome. Mortality increases with elevated admission troponin levels, regardless of baseline clinical risk. The substantial number of patients who present with markedly elevated troponin and their relatively worse outcomes highlights the need for continued improvement in prehospital STEMI detection and care.

ST-segment elevation myocardial infarction

ST-segment elevation myocardial infarction (STEMI) is the most acute manifestation of coronary artery disease and is associated with great morbidity and mortality. A complete thrombotic occlusion developing from an atherosclerotic plaque in an epicardial coronary vessel is the cause of STEMI in the majority of cases. Early diagnosis and immediate reperfusion are the most effective ways to limit myocardial ischaemia and infarct size and thereby reduce the risk of post-STEMI complications and heart failure. Primary percutaneous coronary intervention (PCI) has become the preferred reperfusion strategy in patients with STEMI; if PCI cannot be performed within 120 minutes of STEMI diagnosis, fibrinolysis therapy should be administered to dissolve the occluding thrombus. The initiation of networks to provide around-the-clock cardiac catheterization availability and the generation of standard operating procedures within hospital systems have helped to reduce the time to reperfusion therapy. Together with new advances in antithrombotic therapy and preventive measures, these developments have resulted in a decrease in mortality from STEMI. However, a substantial amount of patients still experience recurrent cardiovascular events after STEMI. New insights have been gained regarding the pathophysiology of STEMI and feed into the development of new treatment strategies.

Effect of Pentoxifylline in Ameliorating Myocardial Injury in Patients With Myocardial Infarction Undergoing Thrombolytic Therapy: A Pilot Randomized Clinical Trial

Cell death following acute myocardial infarction (MI) is the hallmark pathology of cardiovascular disease, leading to considerable mortality and morbidity. Platelet and neutrophil activation and inflammatory cytokines, prominently TNF-α, play an important role in the development of cell death. Because pentoxifylline inhibits platelet and neutrophil activation and reduces TNF-α, this study was performed to assess the potential benefit of pentoxifylline in the reduction of myocardial injury following acute MI. In this randomized clinical trial, 98 patients with acute MI were randomly divided into 2 groups. The intervention group received an oral dose of 1200 mg of pentoxifylline immediately before thrombolytic therapy (TLT). All patients received the same standard protocol for treatment of MI. Cardiac enzymes were checked over 48 hours. ST resolution was measured over 90 minutes. Then all patients were followed up for a 1-month period to assess major adverse cardiac effects (MACEs). There were no significant differences in peak levels of CPK (P = .18) and CK-MB (P = .33) between the 2 groups, whereas peak level of troponin I was significantly lower in the pentoxifylline group (16.8 ± 10.4 vs 21.3 ± 11.6; P = .048). No significant change between the groups was observed in biomarkers levels, ST segment resolution, cardiac ejection fraction, and MACEs. The results showed that pentoxifylline significantly reduced the peak value of troponin I in patients with acute MI receiving TLT. No significant change was observed in the other studied parameters. Further outcome-based studies are needed to show the clinical relevance of differences between the groups in troponin peak.

A systematic evaluation of immunoassay point-of-care testing to define impact on patients' outcomes

Background Point-of-care testing has been developed to provide rapid test results. Most published studies focus on analytical performance, neglecting its impact on patient outcomes. Objective To review the analytical performance and accuracy of point-of-care testing specifically planned for immunoassay and to evaluate the impact of faster results on patient management. Methods A search of electronic databases for studies reporting immunoassay results obtained in both point-of-care testing and central laboratory scenarios was performed. Data were extracted concerning the study details, and the methodological quality was assessed. The analytical characteristics and diagnostic accuracy of six points-of-care testing: troponin, procalcitonin, parathyroid hormone, brain natriuretic peptide, C-reactive protein and neutrophil gelatinase-associated lipocalin were evaluated. Results A total of 116 scientific papers were analysed. Studies measuring procalcitonin, parathyroid hormone and neutrophil gelatinase-associated lipocalin reported a limited impact on diagnostic decisions. Seven studies measuring C-reactive protein claimed a significant reduction of antibiotic prescription. Several authors evaluated brain natriuretic peptide or troponin reporting faster decision-making without any improvement in clinical outcome. Forty-four per cent of studies reported analytical data, showing satisfactory correlations between results obtained through point-of-care testing and central laboratory setting. Half of studies defined the diagnostic accuracy of point-of-care testing as acceptable for troponin (median sensitivity and specificity: 74% and 94%, respectively), brain natriuretic peptide (median sensitivity and specificity: 82% and 88%, respectively) and C-reactive protein (median sensitivity and specificity 85%). Conclusions Point-of-care testing immunoassay results seem to be reliable and accurate for troponin, brain natriuretic peptide and C-reactive protein. The satisfactory analytical performance, together with an excellent practicability, suggests that it could be a consistent tool in clinical practice, but data are lacking regarding the patient outcomes.

Discordant cardiac biomarker levels independently predict outcome in ST-segment elevation myocardial infarction

AIMS

To investigate the prognostic relevance of elevated Troponin T (cTnT) levels in patients with ST-segment elevation myocardial infarction (STEMI) without significant creatine kinase (CK) elevation on admission.

METHODS AND RESULTS

From January 1, 2002 to December 31, 2006 patients with STEMI without significant CK elevation (<2-fold) on admission treated with percutaneous coronary intervention (PCI) were included and stratified according to cTnT plasma levels. Univariate and multivariate regression analyses were used to find independent predictors for mortality. During the 5-year period 514 patients with STEMI and normal CK plasma levels were included. 308 (59.9 %) patients had cTnT levels <0.1 μg/l and 206 (40.1 %) patients had cTnT levels ≥0.1 μg/l. Multivariate logistic regression analysis identified cTnT levels ≥0.1 μg/l and 3-vessel disease as positive, and hemoglobin levels as negative independent predictors for long-term mortality. Discordantly elevated cTnT plasma levels independently predicted higher mortality rates in the first year (HR 3.9, 95 % CI 1.7-9.1, p = 0.002) and during 5 years (HR 2.3, 95 % CI 1.4-3.9, p = 0.002) after PCI for STEMI.

CONCLUSIONS

Discordant elevation of cTnT in the presence of normal CK plasma levels on admission is associated with increased mortality in STEMI patients undergoing primary PCI. This may be due to preceding microembolization.

Subclinical elevation of high-sensitive troponin T levels at the convalescent stage is associated with increased 5-year mortality after ST-elevation myocardial infarction

BACKGROUND

It is unclear whether serum high-sensitive troponin T (hs-TnT) levels at the convalescent stage of ST-elevation myocardial infarction (STEMI) are associated with long-term mortality.

METHODS

This study enrolled a total of 2944 consecutive STEMI patients who were registered in the Osaka Acute Coronary Insufficiency Study between 2000 and 2009, and whose hs-TnT levels were evaluated at the convalescent stage. Patients were divided into four hs-TnT category groups according to the results of survival classification and regression tree (CART) analysis. The impact of hs-TnT levels on 5-year mortality was evaluated using multivariate Cox regression analysis.

RESULTS

Only one patient had hs-TnT level below the detection limit of the assay (<0.003ng/mL). The median hs-TnT level was 0.025 (quartile 0.011-0.083)ng/mL. During the median follow-up period of 1782 days, 188 patients died. Survival CART analysis revealed that the 1st, 2nd, and 3rd discriminating hs-TnT levels to discern 5-year mortality were 0.028, 0.008, and 1.340ng/mL, respectively. The adjusted hazard ratios for the medium-low (0.009-0.028ng/mL), medium-high (0.029-1.340ng/mL), and high-risk (≥1.341ng/mL) groups were 3.03 (95% confidence interval 1.18-7.77, p=0.021), 4.29 (1.63-11.28, p=0.003), and 8.68 (2.20-34.27, p=0.002), respectively. Integrated discrimination improvement (IDI) analysis revealed that incorporation of this hs-TnT classification scheme with other clinical variables statistically improved the discriminatory accuracy for 5-year mortality, with a time-dependent IDI of 0.0076 (p=0.033).

CONCLUSIONS

hs-TnT levels at the convalescent stage were associated with long-term mortality in STEMI patients. Even subclinical elevation of hs-TnT levels was associated with increased 5-year mortality.

Point-of-care cardiac troponin test accurately predicts heat stroke severity in rats

Heat stroke (HS) remains a significant public health concern. Despite the substantial threat posed by HS, there is still no field or clinical test of HS severity. We suggested previously that circulating cardiac troponin (cTnI) could serve as a robust biomarker of HS severity after heating. In the present study, we hypothesized that (cTnI) point-of-care test (ctPOC) could be used to predict severity and organ damage at the onset of HS. Conscious male Fischer 344 rats (n = 16) continuously monitored for heart rate (HR), blood pressure (BP), and core temperature (Tc) (radiotelemetry) were heated to maximum Tc (Tc,Max) of 41.9 ± 0.1°C and recovered undisturbed for 24 h at an ambient temperature of 20°C. Blood samples were taken at Tc,Max and 24 h after heat via submandibular bleed and analyzed on ctPOC test. POC cTnI band intensity was ranked using a simple four-point scale via two blinded observers and compared with cTnI levels measured by a clinical blood analyzer. Blood was also analyzed for biomarkers of systemic organ damage. HS severity, as previously defined using HR, BP, and recovery Tc profile during heat exposure, correlated strongly with cTnI (R(2) = 0.69) at Tc,Max. POC cTnI band intensity ranking accurately predicted cTnI levels (R(2) = 0.64) and HS severity (R(2) = 0.83). Five markers of systemic organ damage also correlated with ctPOC score (albumin, alanine aminotransferase, blood urea nitrogen, cholesterol, and total bilirubin; R(2) > 0.4). This suggests that cTnI POC tests can accurately determine HS severity and could serve as simple, portable, cost-effective HS field tests.

Novel Biomarkers: Utility in Patients with Acute Chest Pain and Relationship to Coronary Artery Disease on Coronary CT Angiography

Acute chest pain remains one of the most common patient presentations encountered in the emergency department. With the evolution of biomarkers and improvement in cardiac imaging there has been advancement in risk stratification of patients, but millions of dollars continue to be spent in the assessment of chest pain. Investigators have explored possible comparative alternatives to the traditional work up of chest pain. In this review, we will discuss the current state of biomarker use in the evaluation of acute chest pain. We will review established and emerging circulating biomarkers and their addition to cardiac CT for appropriate diagnosis of coronary artery disease.

A review of troponins in ischemic heart disease and other conditions

Measuring cardiac troponin (cTn) I and T levels is currently considered to be a cornerstone for making the diagnosis of acute coronary syndrome (ACS).Based on current literature, cTnI and cTnT are known to be very sensitive and specific for myocardial damage, regardless of the underlying cause. Lately, it has been found that cTns can be elevated and reflect worse prognoses in many situations where ACS is excluded. Such information can affect the validity of cTns as markers for ACS without classic symptoms. This may call for a revision of the troponin cutoff values to make a diagnosis of ACS. Furthermore, it opens a new field of study to determine appropriate management of patients with elevated cTn levels in whom ACS has been excluded.

High-concentration versus titrated oxygen therapy in ST-elevation myocardial infarction: a pilot randomized controlled trial

BACKGROUND

The optimal approach to oxygen therapy in ST-elevation myocardial infarction (STEMI) is uncertain.

METHODS

A randomized controlled trial was undertaken in which 136 patients presenting with their first STEMI uncomplicated by cardiogenic shock or marked hypoxia were randomized to receive high-concentration (6 L/min via medium concentration mask) or titrated oxygen (to achieve oxygen saturation 93%-96%) for 6 hours after presentation. The main outcome variables were 30-day mortality and infarct size assessed by troponin T level at 72 hours. Secondary outcomes included a meta-analysis of mortality data from this study and previous randomized controlled trials, and infarct size was assessed by magnetic resonance imaging at 4 to 6 weeks.

RESULTS

There were 1 of 68 and 2 of 68 deaths in the high-concentration and titrated oxygen groups, respectively; a meta-analysis including these data with those from the 2 previous studies showed an odds ratio for mortality of high-concentration oxygen compared with room air or titrated oxygen of 2.2 (95% CI 0.8-6.0). There was no significant difference between high-concentration versus titrated oxygen in troponin T (ratio of mean levels 0.74, 95% CI 0.50-1.1, P = .14), infarct mass (mean difference -0.8 g, 95% CI -7.6 to 6.1, P = .82), or percent infarct mass (mean difference -0.6%, 95% CI -5.6 to 4.5, P = .83).

CONCLUSION

This study found no evidence of benefit or harm from high-concentration compared with titrated oxygen in initially uncomplicated STEMI. However, our estimates have wide CIs, and as a result, large randomized controlled trials are required to resolve the clinical uncertainty.

Established and novel biomarkers in ST-elevation myocardial infarction

Cardiac biomarkers assist in the diagnosis of and risk stratification in acute coronary syndromes. In ST-elevation myocardial infarction (STEMI), rapid diagnosis and initiation of reperfusion via primary percutaneous coronary intervention or fibrinolysis is often based on the clinical history and presenting ECG, but measurement of biomarkers in the early and/or late phases of STEMI may allow the selection of patients who are at increased or decreased risk of subsequent complications. Although the measurement of only three biomarkers (troponin, natriuretic peptides and C-reactive protein) are currently included in practice guidelines, more than 20 other novel cardiac biomarkers have been proposed to provide improved risk stratification after a STEMI.

Early dynamic risk stratification with baseline troponin levels and 90-minute ST-segment resolution to predict 30-day cardiovascular mortality in ST-segment elevation myocardial infarction: analysis from CLopidogrel as Adjunctive ReperfusIon TherapY (CLARITY)-Thrombolysis in Myocardial Infarction (TIMI) 28

BACKGROUND

Troponin is the preferred biomarker for risk stratification in non-ST elevation ACS. The incremental prognostic use of the initial magnitude of troponin elevation and its value in conjunction with ST-segment resolution (STRes) in ST elevation myocardial infarction (STEMI) is less well defined.

METHODS

Troponin T (TnT) was measured in 1,250 patients at presentation undergoing fibrinolysis for STEMI in CLARITY-TIMI 28. ST-segment resolution was measured at 90 minutes. Multivariable logistic regression was used to examine the independent association between TnT levels, STRes, and 30-day cardiovascular (CV) mortality.

RESULTS

Patients were classified into undetectable TnT at baseline (n = 594), detectable but below the median of 0.12 ng/mL (n = 330), and above the median (n = 326). Rates of 30-day CV death were 1.5%, 4.5%, and 9.5%, respectively (P < .0001). Compared with those with undetectable levels and adjusting for baseline factors, the odds ratios for 30-day CV death were 4.56 (1.72-12.08, P = .002) and 5.81 (2.29-14.73, P = .0002) for those below and above the median, respectively. When combined with STRes, there was a significant gradient of risk, and in a multivariable model both baseline TnT (P = .004) and STRes (P = .003) were significant predictors of 30-day CV death. The addition of TnT and STRes to clinical risk factors significantly improved the C-statistic (from 0.86 to 0.90, P = .02) and the integrated discriminative improvement (7.1% increase) (P = .0009).

CONCLUSIONS

Baseline TnT and 90-minute STRes are independent predictors of 30-day CV death in patients with STEMI. Use of these 2 simple, readily available tools can aid clinicians in early risk stratification.

The usage patterns of cardiac bedside markers employing point-of-care testing for troponin in non-ST-segment elevation acute coronary syndrome: results from CRUSADE

BACKGROUND

Point-of-care (POC) testing may expedite the care of emergency department (ED) patients suspected of having acute coronary syndromes (ACS). We evaluated the use patterns of cardiac bedside markers or POC testing for troponin in patients with non-ST-segment elevation (NSTE) ACS.

METHODS

NSTE ACS data were collected from the Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes with Early Implementation of the American College of Cardiology/American Heart Association (ACC/AHA) Guidelines (CRUSADE) registry. We compared hospital and patient characteristics, in-hospital events, and process-of-care variables between hospitals to those that did not use POC testing in > or = 50% of enrolled patients. We examined characteristics, in-hospital events, and process-of-care differences between patients with negative vs positive troponin POC testing results.

RESULTS

Of 568 hospitals, 74 (16,276 patients) had high POC usage compared with 197 hospitals (50,782 patients) with no troponin POC usage. From the high POC usage hospitals, 12,604 patients had recorded troponin POC test results. Hospitals with high POC usage had a shorter ED length of stay and were less likely to administer aspirin, beta-blockers, and heparin during the first 24 hours of care. Patients with positive troponin POC results were more often older, minority, female, Medicare-insured, diabetic, and renally impaired. They had fewer electrocardiograms within 10 minutes but were more likely to get aspirin, beta-blockers, glycoprotein IIb/IIIa inhibitors, and heparin within 24 hours of arrival. They also had longer ED lengths of stay, received fewer in-hospital and interventional procedures, and had more adverse clinical events.

CONCLUSION

Differences existed in how hospitals used POC testing and the care given based on those results. Positive POC results are associated with expedited and higher use of anti-ischemic therapies.

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.

Usefulness of peak troponin-T to predict infarct size and long-term outcome in patients with first acute myocardial infarction after primary percutaneous coronary intervention

In acute myocardial infarction cardiac troponin-T (cTnT) is the preferred biomarker to detect myocardial necrosis. Our aim was to investigate the prognostic value of peak plasma cTnT in patients with ST-elevation myocardial infarction treated by primary percutaneous coronary intervention (PCI). Patients were eligible if ST-elevation myocardial infarction symptoms started <9 hours before the primary PCI. During the first 48 hours after primary PCI, cTnT and creatine kinase were measured repeatedly. Main outcome measures were left ventricular ejection fraction assessed by myocardial scintigraphy at 90 days, and clinical outcomes through 1-year follow-up after primary PCI in a dedicated outpatient clinic; 168 consecutive patients (79% men) with first ST-elevation myocardial infarction were studied. Mean age +/- SD was 59 +/- 12 years. Peak cTnT values were reached within 24 hours after primary PCI in all patients. The enzymatic infarct size, measured by cumulative 48-hours creatine kinase release, correlated positively with peak cTnT (r = 0.73, p <0.001). Left ventricular ejection fraction at 3 months was negatively correlated with peak cTnT (r = -0.52, p <0.001). A peak plasma cTnT > or = 6.5 microg/L predicted a left ventricular ejection fraction < or = 40% at follow-up with 86% sensitivity and 74% specificity. Multivariable Cox regression analysis identified peak cTnT as an independent predictor of major adverse cardiac events (hazard ratio 1.07, 95% confidence limits 1.01 to 1.12) and heart failure (hazard ratio 1.12, 95% confidence limits 1.05 to 1.20) during follow-up. In conclusion, peak cTnT after primary PCI for ST-elevation myocardial infarction offers a good estimation of infarct size and is a prognostic indicator in patients with first acute myocardial infarction.

Biomarkers on admission for the prediction of cardiovascular events after primary stenting in patients with ST-elevation myocardial infarction

BACKGROUND

Several cardiac biomarkers have been shown to have predictive values for the development of cardiovascular disease and clinical outcome after events, and are now broadly used by clinicians. Little is known about the utility of these biomarker values on admission in ST-elevation myocardial infarction (STEMI) cases of primary drug-eluting stent (DES) implantation and intense medical therapy.

HYPOTHESIS

Because little is known about the utility of these biomarkers on admission in ST-elevation myocardial infarction (STEMI) in cases primary drug-eluting stent (DES) implantation and intense medical therapy, we evaluated clinical outcomes.

METHODS

We enrolled 207 consecutive STEMI patients treated with primary stenting (mean age, 57.3 +/- 12.0 y). We evaluated the association between B-type natriuretic peptide (BNP), cardiac troponin I (cTnI), high-sensitivity C-reactive protein (hs-CRP) on admission, and death, reinfarction, and new or worsening congestive heart failure (CHF) through 1 y.

RESULTS

In backward-elimination models including all biomarkers, only the cTnI level was retained as a predictor of 1-y CHF (odds ratio [OR]: 1.017, 95% confidence interval [CI]: 1.001-1.034, p = 0.039). There were no predictors in terms of 1-y death, reinfarction, and composite endpoint. When we applied a simple score system, in which patients were categorized on the basis of the number of elevated biomarkers, the 1-y risks of death (p = 0.600), reinfarction (p = 0.185), and composite endpoint (p = 0.620) did not increase in proportion to the number of elevated biomarkers on admission. One-y CHF only tended to increase according to the number of elevated biomarkers (p = 0.067).

CONCLUSIONS

The use of cardiac biomarkers on admission, in each or in combination, had only a minimal impact for the prediction of long-term cardiovascular events after primary stenting in STEMI patients.

The value of biochemical markers for risk stratification prior to hospital admission in acute chest pain

We describe the use of biochemical markers in the pre-hospital setting with regard to diagnostic accuracy for the detection of an acute myocardial infarction (AMI) and for prognosis in connection with acute chest pain. The sensitivity has been reported to be limited; blood sampling occurs very early and often prior to the release of biochemical markers into the circulation. The specificity was in some studies also limited, but this is more difficult to explain. New biochemical markers like human heart fatty acid binding protein (H-FACB) have shown improved diagnostic accuracy, in the pre-hospital setting, in one small pilot study compared with traditional biochemical markers like troponins, creatine kinase (CK-MB) and myoglobin. However, in a recent small study, the sensitivity for troponin I (when a low decision limit for myocardial damage was used), when analysed prior to hospital admission, was reported to be very high. The latter data need to be confirmed in larger studies and various biochemical markers reflecting various pathophysiological aspects of the disease need to be tested before the analysis of any marker can be recommended for use in the pre-hospital setting of a suspected AMI.

Myoglobin and troponin I elevation predict 5-year mortality in patients with undifferentiated chest pain in the emergency department

BACKGROUND

The long-term prognostic significance of elevated cardiac markers in an undifferentiated patient population with chest pain is unknown.

METHODS

Serum troponin I (cTnI), creatine kinase-MB (CK-MB), and myoglobin were measured at presentation in 951 consecutive patients evaluated in the emergency department for possible acute coronary syndrome, and all-cause mortality was measured over 5 years.

RESULTS

Final diagnoses included myocardial infarction in 70 (7.4%), unstable angina in 78 (8.2%), stable angina in 26 (2.7%), heart failure in 135 (14.2%), syncope in 61 (6.4%), arrhythmia in 62 (6.5%), and noncardiac diagnoses in 519 (54.6%). Our study population had a mean (+/-SD) age of 63 (+/-16), 434 (46%) were male, 774 (81%) were African American, 408 (43%) had known coronary artery disease, 647 (68%) had hypertension, 244 (26%) had diabetes mellitus, and 237 (25%) had a serum creatinine>or=1.5 mg/dL. At 5 years, there were 349 (36.7%) deaths. In a multivariate model with adjustment for baseline covariates, an elevated cTnI>or=1.0 ng/mL (hazard ratio [HR] 1.7, 95% CI 1.3-2.3) and myoglobin>or=200 ng/mL (HR 1.6, 95% CI 1.2-2.1), but not CK-MB>or=9.0 ng/mL (HR 0.9, 95% CI 0.6-1.3), remained independent predictors of all-cause mortality. Patients with both elevated cTnI and myoglobin had a particularly high mortality rate.

CONCLUSION

Among patients evaluated in the emergency department for possible acute coronary syndromes, myoglobin and cTnI at presentation are powerful, independent predictors of long-term (5-year) prognosis.

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.

Prevalence and Prognostic Significance of Preprocedural Cardiac Troponin Elevation Among Patients With Stable Coronary Artery Disease Undergoing Percutaneous Coronary Intervention

Background— Although cardiac troponin (cTn) elevation is associated with periprocedural complications during percutaneous coronary intervention (PCI) in the setting of acute coronary syndromes, the prevalence and prognostic significance of preprocedural cTn elevation among patients with stable coronary artery disease undergoing PCI are unknown.

Methods and Results— Between July 2004 and September 2006, 7592 consecutive patients who underwent attempted stent placement at 47 hospitals throughout the United States were enrolled in a prospective multicenter registry. We analyzed the frequency of an elevated cTn immediately before PCI and its relationship to in-hospital and 1-year outcomes among patients who underwent PCI for either stable angina or a positive stress test. Among the stable coronary artery disease population (n=2382, 31.4%), 142 (6.0%) had a cTn level above the upper limit of normal before the procedure. Compared with patients who had normal baseline cTn, patients with elevated cTn had a higher rate of in-hospital death or myocardial infarction (13.4% versus 5.6%; P <0.001) and a trend toward higher rates of urgent repeat PCI (1.4% versus 0.2%; P =0.06). In multivariable analyses adjusted for demographic, clinical, angiographic, and procedural factors, baseline cTn elevation remained independently associated with the composite of death or myocardial infarction at hospital discharge (odds ratio, 2.1; 95% confidence interval, 1.2 to 3.8; P =0.01) and at the 1-year follow-up (odds ratio, 2.0; 95% confidence interval, 1.2 to 3.3; P =0.005).

Conclusions— Baseline elevation of cTn is relatively common among patients with stable coronary artery disease undergoing PCI and is an independent prognostic indicator of ischemic complications. If these data are confirmed in future studies, consideration should be given to routine testing of cTn before performance of PCI in this patient population.

Biomarkers and Bioassays for Cardiovascular Diseases: Present and Future

Stratification of cardiac patients arriving at the emergency department is now being made according to the levels of acute cardiac biomarkers (i.e. cardiac troponin (cTn) or creatine kinase myocardial band (CK-MB)). Ongoing efforts are undertaken in an attempt to identify and validate additional cardiac biomarkers, for example, interleukin-6, soluble CD40L, and C-reactive protein, in order to further risk stratify patients with acute coronary syndrome. Several studies have also now shown an association of platelet transcriptome and genomic single nucleotide polymorphisms with myocardial infarction by using advanced genomic tools. A number of markers, such as myeloid-related protein 14 (MRP-14), cyclooxygenase-1 (COX-1), 5-lipoxygenase activating protein (FLAP), leukotriene A4 hydrolase (LTA4H) and myocyte enhancing factor 2A (MEF2A), have been linked to acute coronary syndromes, including myocardial infarction. In the future, these novel markers may pave the way toward personalized disease-prevention programs based on a person's genomic, thrombotic and cardiovascular profiles. Current and future biomarkers and bioassays for identifying at-risk patients will be discussed in this review.

The use of biomarkers for the evaluation and treatment of patients with acute coronary syndromes

The advent of inexpensive, highly accurate, and predictive markers of myocardial injury, inflammation, and hemodynamic stability has revolutionized the evaluation and treatment of patients who have acute coronary syndromes (ACSs). These blood biomarkers require small sample volumes, can be run expeditiously, and provide important information concerning the diagnosis, risk stratification, and treatment of these patients. To understand the use of these markers, one must have some knowledge about what elevations in these markers imply, how they have to be collected and measured to provide reliable information, when to suspect analytic confounds, and what the key values are that impart the diagnostic, prognostic, and therapeutic information. This article discusses these issues, emphasizing what clinicians must know for optimal test use, and then addresses the practical use of these markers in patients who have ACS.

The effects of facilitated primary PCI by guide wire on procedural and clinical outcomes in acute ST-segment elevation myocardial infarction

BACKGROUND

Reperfusion of the infarct related artery (IRA) prior to PCI is prognostically important in patients with acute ST segment elevation myocardial infarction (STEMI). Reperfusion is either achieved spontaneously, facilitated by GP IIb/ IIIa inhibitors, or mechanically by crossing the guide wire beyond the lesion. In order to test the hypothesis that a visible coronary anatomy is independently associated with procedural and clinical outcomes, we evaluated the frequency and prognostic impact of guide wire facilitated reperfusion of the IRA before primary PCI.

METHODS AND RESULTS

We enrolled 311 consecutive patients with successful primary PCI for STEMI (TIMI grade > or =2 flow) within 12 h after onset of symptoms. Among these, 90 patients (28.9%) had a spontaneously reperfused IRA on initial angiogram, 56 patients (18.0%) achieved reperfusion after crossing of the guide wire, and 165 patients (53.1%) successful reperfusion only after PCI. Variables associated with successful guide wire facilitated reperfusion were younger age, no history of arterial hypertension, active smoking status, negative cardiac troponin T on admission, and an infarct in the territory of the right coronary artery. Patients with spontaneous reperfusion or reperfusion after crossing of the guide wire required less fluoroscopic time and less contrast material during angiography and had higher procedural success rates (TIMI grade 3 flow 91.1 vs 79.4%, p=0.048) than patients without initial reperfusion. In addition, patients with reperfusion after crossing the lesion with the guide wire had lower mortality rates at 30 days (3.6 vs 9.1%) and after a median of 16 months (3.6 vs 13.9%, p=0.03) than those with reperfusion after PCI.

CONCLUSIONS

Reperfusion of an occluded IRA by crossing the guide wire is associated with higher procedural success rates and better outcomes. Better roadmapping and device selection represent potential reasons but the exact mechanism for these benefits is still illusive.

Clinical, electrocardiographic, and biochemical data for immediate risk stratification in acute coronary syndromes

The recent evolution in therapeutic options for acute coronary syndromes (ACS) mandates early risk stratification in order to select the appropriate treatment strategy for individual patients. Simple clinical data derived from the patient's medical history and physical examination, a standard twelve-lead electrocardiogram (ECG), and determinations of biochemical markers of myocardial damage can be obtained in the emergency room and serve as a guide for deciding appropriate medical management and optimal use of available resources. Even the most important classification of the ACS is based upon a simple and dichotomous description of the ECG, where the presence of ST-segment elevation mandates an immediate attempt to restore coronary perfusion (either pharmacologically or mechanically), whereas its absence suggests pharmacological stabilization before further evaluation. Across the whole spectrum of ACS, clinical history data (such as older age, previous coronary events, and diabetes) and clinical variables (such as higher heart rate, lower blood pressure, and higher Killip class) are the most powerful prognostic determinants at multivariate analyses derived from large databases. The ECG adds significant and independent prognostic information using the analysis of qualitative (direction of ST-segment shift, associated T-wave inversion, and presence of conduction disturbances) and quantitative (number of leads involved, amount of ST- segment shifts, duration of QRS) characteristics. Biochemical markers of myocardial damage have also been identified as independent predictors of events. In addition, retrospective analyses of clinical trials have suggested that biochemical markers might serve as a guide to select pharmacological therapy. However, how to best combine electrocardiographic and biochemical data for immediate risk stratification remains to be further elucidated.

Cardiac markers and their point-of-care testing for diagnosis of acute myocardial infarction

Acute myocardial infarction (AMI) is the world's leading cause of mortality and morbidity. Therefore, quick and reliable diagnostics of AMI is extremely critical. Compared to the traditionally used central laboratory tests (CLT), which can be time-consuming and expensive, point-of-care testing (POCT) for AMI-indicative cardiac markers provides a convenient means for rapid diagnostic assays to be performed at the site of patient care delivery. In this article, the etiology and diagnosis of AMI are introduced, and some typical cardiac markers and their clinical applications are reviewed. Furthermore, the various POC cardiac marker devices that are currently available, the benefits of using cardiac marker POC assays, and challenges that cardiac marker POCT are facing are also discussed.

Biomarkers in acute cardiac disease: the present and the future

The use of biomarkers to aid diagnosis and treatment is increasing rapidly as genomics and proteomics help us expand the number of markers we can use and as an improved understanding of the pathophysiology of cardiac disease guides their use. However, as with all rapidly expanding fields, there is the risk of excessive enthusiasm unless we are circumspect about the data that guide the clinical use of these new tools. This review focuses first on how to use troponin, which at present is the best validated of the new markers, and will hopefully provide insight into how to use this biomarker more productively by distinguishing subsets of patients and by providing an understanding of the meaning of elevations in various clinical situations. The review then discusses the use as well as the knowledge gaps associated with emerging biomarkers such as B-type natriuretic peptide and C-reactive protein, which are increasingly moving toward more productive clinical use. Finally, it reflects on some of the large number of markers that are still in development.

Use of biomarkers in the emergency department and chest pain unit

The use of biomarkers of cardiac injury in the emergency department (ED) and observation unit settings has several nuances that are different and, therefore, worthy of its own set of use guidelines. The markers that are used, however, are the same. The primary marker of choice continues to be cardiac troponin (Tn). Other markers that have been used because of the need in the ED for rapid triage have been myoglobin and fatty acid binding protein. In addition, some centers still prefer less sensitive and less specific markers such as creatine kinase myocardial band (CK-MB). More recently, a push has occurred to develop markers of ischemia, such as ischemia modified albumin (IMA),to determine which patients have ischemia, even in the absence of cardiac injury. As troponin assays become more sensitive and method for use becomes better understood, the use of these other markers are being relegated to lesser and lesser roles. Markers of ischemia are useful, but at present, despite some enthusiasm, are not ready for routine use. Before describing the recommendations for clinical use of biomarkers in the ED, a basic understanding of some of the science and measurement issues related to these analytes is helpful.

Cardiac biomarkers: a contemporary status report

The field of cardiac biomarkers has grown by leaps and bounds in the past two decades. In this review we try to summarize the explosion of emerging knowledge and address the roles of some of the biomarkers that have either proven or potential utility. We detail some of the markers of ischemia, hemodynamic markers of heart failure, inflammatory markers, and the novel and innovative approach of combining these for a multimarker strategy. At the end of this review we highlight some of the biomarker-guided approaches and strategies that might lead to better and more-effective care of patients.

Artificial Neural Network Models for Prediction of Acute Coronary Syndromes Using Clinical Data From the Time of Presentation

STUDY OBJECTIVE

Clinical and ECG data from presentation are highly discriminatory for diagnosis of acute coronary syndromes, whereas definitive diagnosis from serial ECG and cardiac marker protein measurements is usually not available for several hours. Artificial neural networks are computer programs adept at pattern recognition tasks and have been used to analyze data from chest pain patients with a view to developing diagnostic algorithms that might improve triage practices in the emergency department. The aim of this study is to develop and optimize artificial neural network models for diagnosis of acute coronary syndrome, to test these models on data collected prospectively from different centers, and to establish whether the performance of these models was superior to that of models derived using a standard statistical technique, logistic regression.

METHODS

The study used data from 3,147 patients presenting to 3 hospitals with acute chest pain. Data from hospital 1 were used to train the models, which were then tested on independent data from the other 2 hospitals. From 40 potential factors, variables were selected according to the logarithm of their likelihood ratios to produce models using 8, 13, 20, and 40 factors. Identical data were used for logistic regression and artificial neural network models. Calibration and performance were assessed, the latter using receiver operating characteristic (ROC) curve analysis.

RESULTS

Although the performance of artificial neural network models generally increased with increasing numbers of factors, this was insignificant. The 13-factor model was therefore used for the rest of the study owing to its marginally improved calibration over the smallest model. Area under the ROC curve (with standard error) was 0.97 (0.006). The overall sensitivity and specificity of this model for acute coronary syndrome diagnosis using the training data was 0.93. ROC curves for logistic regression and artificial neural network models applied to data from the 3 hospitals were identical. For the 13-factor artificial neural network model tested on data from hospitals 2 and 3, area under the ROC curves (standard error) were 0.93 (0.006) and 0.95 (0.009), respectively. Investigation of the performance of the artificial neural network models throughout the range of predicted probabilities showed that they were well calibrated.

CONCLUSION

This study confirms that artificial neural networks can offer a useful approach for developing diagnostic algorithms for chest pain patients; however, the exceptional performance and simplicity of the logistic model militates in favor of logistic regression for the present task. Our artificial neural network models were well calibrated and performed well on unseen data from different centers. These issues have not been addressed in previous studies. However, and unlike in previous studies, we did not find the performance of artificial neural network models to be significantly different from that of suitably optimized logistic regression models.

Point-of-Care Testing and Cardiac Biomarkers: The Standard of Care and Vision for Chest Pain Centers

Point-of-care testing (POCT) is defined as testing at or near the site of patient care. POCTdecreases therapeutic turnaround time (TTAT), increases clinical efficiency, and improves medical and economic outcomes. TTAT represents the time from test ordering to patient treatment. POC technologies have become ubiquitous in the United States, and, therefore,so has the potential for speed, convenience, and satisfaction, strong advantages for physicians, nurses, and patients in chest pain centers. POCT is applied most beneficially through the collaborative teamwork of clinicians and laboratorians who use integrative strategies, performance maps, clinical algorithms, and care paths (critical pathways). For example, clinical investigators have shown that on-site integration of testing for cardiac injury markers (myoglobin, creatinine kinase myocardial band [CKMB],and cardiac troponin I [cTnI]) in accelerated diagnostic algorithms produces effective screening, less hospitalization, and substantial savings. Chest pain centers, which now total over 150 accredited in the United States, incorporate similar types of protocol-driven performance enhancements. This optimization allows chest pain centers to improve patient evaluation, treatment, survival, and discharge. This article focuses on cardiac biomarker POCT for chest pain centers and emergency medicine.

Admission N-terminal pro-brain natriuretic peptide and its interaction with admission troponin T and ST segment resolution for early risk stratification in ST elevation myocardial infarction

OBJECTIVE

To assess the long term prognostic value of N-terminal pro-brain natriuretic peptide (NT-proBNP) on admission and its prognostic interaction with both admission troponin T (TnT) concentrations and resolution of ST segment elevation in fibrinolytic treated ST elevation myocardial infarction (STEMI).

DESIGN AND SETTING

Substudy of the ASSENT (assessment of the safety and efficacy of a new thrombolytic) -2 and ASSENT-PLUS trials.

PATIENTS

NT-proBNP and TnT concentrations were determined on admission in 782 patients. According to NT-proBNP concentrations, patients were divided into three groups: normal concentration (for patients < or = 65 years, < or = 184 ng/l and < or = 268 ng/l and for those > 65 years, < or = 269 ng/l and < or = 391 ng/l in men and women, respectively); higher than normal but less than the median concentration (742 ng/l); and above the median concentration. For TnT, a cut off of 0.1 microg/l was used. Of the 782 patients, 456 had ST segment resolution (< 50% or > or = 50%) at 60 minutes calculated from ST monitoring.

MAIN OUTCOME MEASURES

All cause one year mortality.

RESULTS

One year mortality increased stepwise according to increasing concentrations of NT-proBNP (3.4%, 6.5%, and 23.5%, respectively, p < 0.001). In receiver operating characteristic analysis, NT-proBNP strongly trended to be associated more with mortality than TnT and time to 50% ST resolution (area under the curve 0.81, 95% confidence interval (CI) 0.72 to 0.9, 0.67, 95% CI 0.56 to 0.79, and 0.66, 95% CI 0.56 to 0.77, respectively). In a multivariable analysis adjusted for baseline risk factors and TnT, both raised NT-proBNP and ST resolution < 50% were independently associated with higher one year mortality, whereas raised TnT contributed independently only before information on ST resolution was added to the model.

CONCLUSION

Admission NT-proBNP is a strong independent predictor of mortality and gives, together with 50% ST resolution at 60 minutes, important prognostic information even after adjustment for TnT and baseline characteristics in STEMI.

Risk stratification of chest pain patients by point-of-care cardiac troponin T and myoglobin measured in the emergency department

A prospective multicenter study including 1410 chest pain patients with suspected acute coronary syndromes was carried out to examine the predictive value of biological cardiac markers for adverse events measured by a point-of-care system. Admission cardiac troponin T (cTnT) and myoglobin were measured in parallel on a point-of-care system in the emergency department and -- together with CK-MB mass -- on lab analyzers. In a one-year follow-up, cardiac and non-cardiac death, acute myocardial infarction, unstable angina pectoris and need for revascularization were registered. Median time between onset of symptoms and admission was 285 min; 172 patients (12.2%) had no event during follow-up. If the cTnT, measured either by the point-of-care system or a conventional lab analyzer, was >0.05 microg/L, then the chance of a cardiac event during the follow-up period was doubled (18% vs. 9%). Serial cTnT measurement did not add any further value to the predictive power of the admission cTnT. Myoglobin and CK-MB mass identified increasing risk with increasing concentration quartiles; cardiac event rates were 2.8- to 4.4-fold higher between the quartiles with the lowest and those with the highest analyte concentration, respectively. There was no difference in non-cardiac death rates between any concentration quartiles. In conclusion, the prediction of clinical events by cardiac troponin T and myoglobin measured with a point-of-care analyzer in the emergency department was as good as that of the same cardiac markers and CK-MB mass measured on lab analyzers.

Prognostic value of serum concentration of heart-type fatty acid-binding protein relative to cardiac troponin T on admission in the early hours of acute coronary syndrome

BACKGROUND

Heart-type fatty acid-binding protein (H-FABP) is proposed as an early biomarker for acute myocardial infarction (AMI), but its prognostic value is unclear in acute coronary syndrome (ACS). We evaluated the prognostic value of the H-FABP concentration relative to cardiac troponin T (cTnT) in the early hours of ACS.

METHODS

Serum concentrations of H-FABP and cTnT were measured on admission in 328 consecutive patients hospitalized for ACS within 6 h after the onset of chest pain [AMI, 241 (73.5%) patients; ST-segment elevation myocardial infarction, 154 (47.0%) patients; and emergent coronary angiography within 24 h after admission, 287 (87.5%) patients]. Cardiac events, which were defined as cardiac death or subsequent nonfatal AMI, were monitored for 6 months after admission.

RESULTS

During the 6-month follow-up period, there were 25 cardiac events, including 15 cardiac deaths and 10 subsequent nonfatal AMIs. Stepwise multivariate analyses including clinical, electrocardiographic, and biochemical variables revealed that increased H-FABP (above the median of 9.8 microg/L), but not increased cTnT (above the median of 0.02 microg/L), was independently associated with cardiac events in all patients [relative risk (RR) = 8.96; P = 0.0004], the subgroup of patients with ST-segment elevation myocardial infarction (RR = 11.3; P = 0.02), and the subgroup of patients with unstable angina and non-ST-segment elevation myocardial infarction (RR = 8.31; P = 0.007). The area under the ROC curve was higher for H-FABP than for cTnT (0.711 vs 0.578; P = 0.08), suggesting that H-FABP concentrations have a greater predictive capacity for cardiac events than cTnT.

CONCLUSION

Serum H-FABP is a potential independent predictor of cardiac events within 6 months of patient admission and may provide prognostic information superior to cTnT in the early hours of ACS.

Risk prediction in patients with chest pain: early assessment by the combination of troponin I results and electrocardiographic findings

OBJECTIVE

To evaluate the prognostic value of point of care troponin I (TnI) results in combination with findings from the admission electrocardiogram (ECG) in patients with chest pain.

METHODS

Rapid measurements of TnI were performed in 191 consecutive patients with chest pain and a non-diagnostic ECG for myocardial infarction.

RESULTS

Within 6 h from admission, maximum TnI elevations of > or = 0.07 microg/l and > or = 0.1 microg/l were noted in 59 and 39% of all patients, respectively. TnI elevations in the range of 0.07-0.09 microg/l were found in many patients with diagnoses other than acute coronary syndrome. By 6-month follow-up, cardiac death had occurred in 7.1 and 11% of patients with maximum TnI > or = 0.07 microg/l and > or = 0.1 microg/l, respectively and myocardial reinfarction was documented in 12 and 15%, respectively. ST-segment depression on the admission ECG was present in 16% of all patients and was the electrocardiographic abnormality with the highest risk (cardiac death 7.7%, myocardial reinfarction 15%). The combination of TnI > or = 0.1 microg/l and ST-segment depression or an abnormal admission ECG in general allowed the identification of patients at low, intermediate and high cardiac risk, 3 h after admission.

CONCLUSION

A threshold of TnI > or = 0.1 microg/l corresponding to the 10% coefficient of variation is prognostically most suitable for prediction of cardiac events in patients with chest pain. The combination of TnI results and findings from the admission ECG improves prognostic assessment and allows early and reliable risk stratification in this patient population.

Troponins in acute coronary syndromes

Cardiac troponins have replaced creatine kinase-MB as the preferred biomarker for establishing the diagnosis of myocardial infarction (MI). Expert recommendations set the diagnostic decision-limit for each assay at the 99th percentile of troponin levels in an apparently healthy reference population, which due to a lack of standardization, will vary depending upon the manufacturer. Among patients presenting with an acute coronary syndrome (ACS), even low-level elevations of cardiac troponin T or I correlate with higher risk of death and recurrent ischemic events compared to patients with levels of troponin below the decision limit. Renal failure does not appear to diminish the prognostic value of troponins among patients with a high clinical probability of ACS. Moreover, patients with elevated levels of troponin derive the most benefit from more intense medical therapy with antithrombin and antiplatelet medications, as well as an early invasive management strategy. Whereas cardiac troponins are extremely specific for myocardial necrosis, they do not discriminate between ischemic and non-ischemic etiologies of myocardial injury. Clinicians must, therefore, determine whether a patient's presenting symptoms are consistent with ACS. Combining troponin with other cardiac biomarkers may offer complimentary information on the underlying pathobiology and prognosis in an individual patient. Future generations of troponin assays may detect specific posttranslational modifications of troponins that may increase the analytic sensitivity for myocardial damage and offer insight into the timing and mechanism of myocardial injury.

Impact of the Revised Criteria for Acute Myocardial Infarction Using Cardiac Troponins in a Japanese Population With Acute Coronary Syndromes

BACKGROUND

The clinical implications of applying the new criteria of acute myocardial infarction (AMI) with cardiac troponins in terms of their diagnostic and prognostic impact in patients with suspected acute coronary syndromes (ACS) have not been well evaluated.

METHODS AND RESULTS

The study group comprised 973 consecutive patients who were diagnosed as having ACS with or without ST elevation (STE). They were divided into 3 groups: unstable angina (UA) group (n=195) representing patients with no significant elevations of creatine kinase (CK) and troponin T (TnT); TnT-myocardial infarction (MI) group (n=170) with TnT elevation and no CK elevation (additionally detected AMI by the new criteria); CK-MI group (n=608) with significant elevation of CK (AMI by the old criteria). In the TnT-MI group, 140 (76%) patients had non-STE ACS. In-hospital mortality rates for STE ACS were 0%, 2.5% and 9.7% in the UA, TnT-MI and CK-MI groups, respectively. The corresponding values for non-STE ACS were 1.8%, 4.6%, and 16.5%, respectively (p<0.0001), suggesting a pivotal role of TnT. In multiple logistic regression analysis, significant CK elevation was selected as an independent predictor of in-hospital death in concurrence with age > or =75 years, prior MI, shock and low left ventricular ejection fraction in non-STE ACS.

CONCLUSIONS

The new criteria result in a substantial increase in the diagnosis of AMI from non-STE ACS in particular. They assist greatly in detailed risk stratification of ACS patients, notably in cooperation with the old CK criteria.