Long-term prognostic value of serial troponin T bedside tests in patients with acute coronary syndromes

Accuracy of OMI ECG findings versus STEMI criteria for diagnosis of acute coronary occlusion myocardial infarction

OBJECTIVE

In the STEMI paradigm of Acute Myocardial Infarction (AMI), many NSTEMI patients have unrecognized acute coronary occlusion MI (OMI), may not receive emergent reperfusion, and have higher mortality than NSTEMI patients without occlusion. We have proposed a new OMI vs. Non-Occlusion MI (NOMI) paradigm shift. We sought to compare the diagnostic accuracy of OMI ECG findings vs. formal STEMI criteria for the diagnosis of OMI. We hypothesized that blinded interpretation for predefined OMI ECG findings would be more accurate than STEMI criteria for the diagnosis of OMI.

METHODS

We performed a retrospective case-control study of patients with suspected acute coronary syndrome. The primary definition of OMI was either 1) acute TIMI 0-2 flow culprit or 2) TIMI 3 flow culprit with peak troponin T ≥ 1.0 ng/mL or I ≥ 10.0 ng/mL.

RESULTS

808 patients were included, of whom 49% had AMI (33% OMI; 16% NOMI). Sensitivity, specificity, and accuracy of STEMI criteria vs Interpreter 1 using OMI ECG findings among 808 patients were 41% vs 86%, 94% vs 91%, and 77% vs 89%, and for Interpreter 2 among 250 patients were 36% vs 80%, 91% vs 92%, and 76% vs 89%. STEMI(-) OMI patients had similar infarct size and mortality as STEMI(+) OMI patients, but greater delays to angiography.

CONCLUSIONS

Blinded interpretation using predefined OMI ECG findings was superior to STEMI criteria for the ECG diagnosis of Occlusion MI. These data support further investigation into the OMI vs. NOMI paradigm and suggest that STEMI(-) OMI patients could be identified rapidly and noninvasively for emergent reperfusion using more accurate ECG interpretation.

Point-of-care testing: where is the evidence? A systematic survey

Point-of-care testing (POCT) has had rapid technological development and their use is widespread in clinical laboratories to assure reduction of turn-around-time and rapid patient management in some clinical settings where it is important to make quick decisions. Until now the papers published about the POCT have focused on the reliability of the technology used and their analytical accuracy. We aim to perform a systematic survey of the evidence of POCT efficacy focused on clinical outcomes, selecting POCT denoted special analytes characterized by possible high clinical impact. We searched in Medline and Embase. Two independent reviewers assessed the eligibility, extracted study details and assessed the methodological quality of studies. We analyzed 84 studies for five POCT instruments: neonatal bilirubin, procalcitonin, intra-operative parathyroid hormone, troponin and blood gas analysis. Studies were at high risk of bias. Most of the papers (50%) were studies of correlation between the results obtained by using POCT instruments and those obtained by using laboratory instruments. These data showed a satisfactory correlation between methods when similar analytical reactions were used. Only 13% of the studies evaluated the impact of POCT on clinical practice. POCT decreases the time elapsed for making decisions on patient management but the clinical outcomes have never been adequately evaluated. Our work shows that, although POCT has the potential to provide beneficial patient outcome, further studies may be required, especially for defining its real utility on clinical decision making.

Optical scanner for immunoassays with up-converting phosphorescent labels

A 2-D optical scanner was developed for the imaging and quantification of up-converting phosphor (UCP) labels in immunoassays. With resolution better than 500 microm, a scan rate of 0.4 mm/s, and a 1-2% coefficient of variation for repeatability, this scanner achieved a detection limit of fewer than 100 UCP particles in an 8.8. x 10(4) microm(2) area and a dynamic range that covered more than three orders of magnitude. Utilizing this scanner, a microfluidic chip immunoassay for the cytokine interferon-gamma (IFN-gamma) was developed: concentrations as low as 3 pM (50 pg/mL) were detected from 100 microL samples with a total assay time of under an hour, including the 8 min readout. For this UCP-based assay, 2-D images of the capture antibody lines were scanned, image processing techniques were employed to extract the UCP emission signals, a response curve that spanned 3-600 pM IFN-gamma was generated, and a five-parameter logistic mathematical model was fitted to the data for determination of unknown IFN-gamma concentrations. Relative to common single-point or 1-D scanning optical measurements, our results suggest that a simple 2-D imaging system can speed assay development, reduce errors, and improve accuracy by characterizing the spatial distribution and uniformity of surface-captured optical labels as a function of assay conditions and device parameters.

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.

Elevated cardiac troponin T in hemodialysis patients receiving more intravenous iron sucrose

Elevated cardiac troponin T (cTnT) has been associated with shorter survival in hemodialysis patients. Moreover, intravenous (IV) iron treatment has been held responsible for oxidative stress and accelerated atherosclerosis in these patients. In the present study, we investigated the relationship between cTnT concentration, IV iron treatment, and parameters of iron status. In addition, parameters of oxidative stress, inflammation, and atherosclerosis were evaluated. Predialysis blood samples of 78 chronic hemodialysis patients were analyzed for cTnT, malondialdehyde, creatine kinase (CK), and CK-isoenzyme MB (CK-MB). In addition, the mean value of predialysis serum samples collected during the last year, were considered for homocysteine, ferritin, iron, iron binding capacity, blood cell counts, blood urea nitrogen, creatinine, albumin, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), calcium, phosphate, iPTH, cholesterol, and triglyceride. The quantity of IV iron sucrose administered during the last two years was counted from the patients' files. Echocardiography, all events related to ischemic heart disease, and urine volume were also recorded. Elevated cTnT levels (> or =0.10 ng/mL) were found in 18 patients (23.1%). The amount of iron administered was 2264+/-1871 mg with a range 0-7000 mg. Patients with elevated cTnT levels received more IV iron than those with normal cTnT (3692+/-1771 vs. 1761+/-1595 mg, p<0.001). The serum ferritin level was higher in patients with elevated cTnT (median levels; 477 vs. 288 ng/mL; P<0.05). Patients with elevated cTnT were longer on dialysis compared to those with normal levels (median times; 35.5 vs. 15 months, P<0.01) and regression analysis identified the amount of administered iron as an independent factor for elevated cTnT (P<0.01). Intravenous iron treatment and high ferritin concentration are related to high cTnT level, which has previously been incriminated as a survival marker in hemodialysis patients.

Myoglobin stratifies short-term risk in acute major pulmonary embolism

BACKGROUND

Concentrations of cardiac troponins can be elevated in acute pulmonary embolism (APE) indicating myocardial injury. Although concentration of myoglobin (MYO) increases after myocardial damage, even before detectable rise of cardiac troponin levels occurs, MYO was not evaluated in APE. Therefore, we assessed prevalence and prognostic significance of myoglobin in major APE.

METHODS

We studied 46 patients (30 women, aged 61.9+/-17.8 years) with major APE defined with right ventricular dilatation. On admission serum myoglobin, and cardiac troponin T (cTnT) were measured. Serum MYO concentrations >58 ng/ml for women, and >72 ng/ml for men were considered abnormal. CTnT>0.01 ng/ml was regarded to indicate myocardial injury.

RESULTS

MYO levels exceeding sex specific norms were found in 21/46 (45.7%) of patients, while detectable cTnT was found in 24/46 (52.1%) of patients. Seven patients died during hospitalization. Elevated MYO significantly predicted in-hospital mortality (OR 25, 95% CI 1.3-474.2), while increased cTnT concentration did not affect the survival. Among clinical and echocardiographic variables only older age indicated worse prognosis (OR 1.6, 95% CI 1.06-2.41).

CONCLUSIONS

Myoglobin levels are elevated in serum on admission in almost half of patients with major APE. Elevated myoglobin level, marker of myocardial injury, is a powerful predictor of increased risk of fatal outcome in major pulmonary embolism.

A new scoring system to stratify risk in unstable angina

BACKGROUND

We performed this study to develop a new scoring system to stratify different levels of risk in patients admitted to hospital with a diagnosis of unstable angina (UA), which is a complex syndrome that encompasses different outcomes. Many prognostic variables have been described but few efforts have been made to group them in order to enhance their individual predictive power.

METHODS

In a first phase, 473 patients were prospectively analyzed to determine which factors were significantly associated with the in-hospital occurrence of refractory ischemia, acute myocardial infarction (AMI) or death. A risk score ranging from 0 to 10 points was developed using a multivariate analysis. In a second phase, such score was validated in a new sample of 242 patients and it was finally applied to the entire population (n = 715).

RESULTS

ST-segment deviation on the electrocardiogram, age > or = 70 years, previous bypass surgery and troponin T > or = 0.1 ng/mL were found as independent prognostic variables. A clear distinction was shown among categories of low, intermediate and high risk, defined according to the risk score. The incidence of the triple end-point was 6 %, 19.2 % and 44.7 % respectively, and the figures for AMI or death were 2 %, 11.4 % and 27.6 % respectively (p < 0.001).

CONCLUSIONS

This new scoring system is simple and easy to achieve. It allows a very good stratification of risk in patients having a clinical diagnosis of UA. They may be divided in three categories, which could be of help in the decision-making process.

Risk stratification in non-ST segment elevation acute coronary syndromes with special focus on recent guidelines

Patients with unstable angina or non-ST segment elevation (non-Q-wave) myocardial infarction are a heterogeneous group with respect to their risk of developing clinically significant adverse events such as subsequent myocardial infarction and death. Recent guidelines promote risk stratification of these patients, targeting high-risk patients for maximal antithrombotic and antiischemic therapy and low-risk patients for early discharge. We reviewed current and future modalities for risk stratification of patients and the predictive value of these methods in context with available pharmacologic agents. Unfortunately, most of the data identifying a particular pharmacologic regimen as beneficial in high-risk patients are retrospectively derived from large trials. Until prospective studies that use markers to guide therapy are available, clinicians should be familiar with the use of these risk markers and their application to the role of a given management strategy, including pharmacologic therapy.

Implications of troponin testing in clinical medicine

During the past decade considerable research has been conducted into the use of cardiac troponins, their diagnostic capability and their potential to allow risk stratification in patients with acute chest pain. Determination of risk in patients with suspected myocardial ischaemia is known to be as important as retrospective confirmation of a diagnosis of myocardial infarction (MI). Therefore, creatine kinase (CK)-MB - the former 'gold standard' in detecting myocardial necrosis - has been supplanted by new, more accurate biomarkers.Measurement of cardiac troponin levels constitute a substantial determinant in assessment of ischaemic heart disease, the presentations of which range from silent ischaemia to acute MI. Under these conditions, troponin release is regarded as surrogate marker of thrombus formation and peripheral embolization, and therefore new therapeutic strategies are focusing on potent antithrombotic regimens to improve long-term outcomes. Although elevated troponin levels are highly sensitive and specific indicators of myocardial damage, they are not always reflective of acute ischaemic coronary artery disease; other processes have been identified that cause elevations in these biomarkers. However, because prognosis appears to be related to the presence of troponins regardless of the mechanism of myocardial damage, clinicians increasingly rely on troponin assays when formulating individual therapeutic plans.