Serial creatine kinase-MB results are a sensitive indicator of acute myocardial infarction in chest pain patients with nondiagnostic electrocardiograms: the second Emergency Medicine Cardiac Research Group Study

The diagnostic utility of creatine kinase-MB versus total creatine phosphokinase ratio in patients with non-ST elevation myocardial infarction from unstable angina

Objective:

The present study seeks to find a way to quickly and correctly differentiate myocardial infarction from unstable angina by measuring the creatine kinase-MB/creatine phosphokinase ratio and comparing in non-ST elevation myocardial infarction patients with unstable angina at different time intervals, to improve the health quality of patients with coronary artery disease.

Methods:

The present study is a retrospective epidemiological analysis of 260 patients with non-ST elevation myocardial infarction and 260 patients with unstable angina, including age, sex, creatine kinase-MB, and creatine phosphokinase biomarkers at two-time intervals, including referral (4–8 h from the onset of pain) as the first interval, and 8 h after the first sampling was extracted as the second interval. Moreover, the delta of the creatine kinase-MB/creatine phosphokinase ratio during two interval times was measured.

Results:

In non-ST elevation myocardial infarction patients in the first and second intervals, creatine kinase-MB/creatine phosphokinase ratio was 32.7 and 33.8% higher than the normal laboratory cutoff (positive), respectively, and in the group of unstable angina patients, this index was positive in 31.9 and 30.4% of patients, respectively. There was no significant difference between the mean creatine kinase-MB to creatine phosphokinase index between the patients with non-ST elevation myocardial infarction and unstable angina (p = 0.507). In the first interval, the sensitivity and specificity of this index in differentiating non-ST elevation myocardial infarction from unstable angina were 51.5 and 57.3% (area under the curve = 0.518), respectively. While in the second interval, the sensitivity and specificity of this index were 17.7 and 87.8% (area under the curve = 0.519), respectively. The creatine kinase-MB/creatine phosphokinase delta in the non-ST elevation myocardial infarction group was significantly higher than in patients with unstable angina during different time intervals (p = 0.01).

Conclusion:

According to our results, creatine kinase-MB/creatine phosphokinase index cannot help differentiate the two groups of non-ST elevation myocardial infarction and unstable angina. However, the findings show that higher levels of creatine kinase-MB enzyme and creatine kinase-MB/creatine phosphokinase delta in the early hours, 4–16 h after the onset of pain in non-ST elevation myocardial infarction patients, can be used to differentiate between non-ST elevation myocardial infarction and unstable angina.

An artificial intelligence-based risk prediction model of myocardial infarction

BACKGROUND

Myocardial infarction can lead to malignant arrhythmia, heart failure, and sudden death. Clinical studies have shown that early identification of and timely intervention for acute MI can significantly reduce mortality. The traditional MI risk assessment models are subjective, and the data that go into them are difficult to obtain. Generally, the assessment is only conducted among high-risk patient groups.

OBJECTIVE

To construct an artificial intelligence-based risk prediction model of myocardial infarction (MI) for continuous and active monitoring of inpatients, especially those in noncardiovascular departments, and early warning of MI.

METHODS

The imbalanced data contain 59 features, which were constructed into a specific dataset through proportional division, upsampling, downsampling, easy ensemble, and w-easy ensemble. Then, the dataset was traversed using supervised machine learning, with recursive feature elimination as the top-layer algorithm and random forest, gradient boosting decision tree (GBDT), logistic regression, and support vector machine as the bottom-layer algorithms, to select the best model out of many through a variety of evaluation indices.

RESULTS

GBDT was the best bottom-layer algorithm, and downsampling was the best dataset construction method. In the validation set, the F1 score and accuracy of the 24-feature downsampling GBDT model were both 0.84. In the test set, the F1 score and accuracy of the 24-feature downsampling GBDT model were both 0.83, and the area under the curve was 0.91.

CONCLUSION

Compared with traditional models, artificial intelligence-based machine learning models have better accuracy and real-time performance and can reduce the occurrence of in-hospital MI from a data-driven perspective, thereby increasing the cure rate of patients and improving their prognosis.

Knockdown of miR-1275 protects against cardiomyocytes injury through promoting neuromedin U type 1 receptor

The present study aimed to assess the role of miR-1275 in cardiac ischemia reperfusion injury. H9 human embryonic stem cell (hESC)-derived cardiomyocytes stimulated by oxygen-glucose deprivation/reoxygenation (OGD/R) were used to simulate myocardial injury in vitro. miR-1275 expression levels in cells were measured by RT-qPCR. The release of lactate dehydrogenase (LDH) and creatine kinase (CK) was examined through LDH and CK ELISA kits. Cell apoptosis was detected through flow cytometry. A Fura-2 Calcium Flux Assay Kit and a Fluo-4 assay kit were used to determine the Ca²⁺ concentration. Expression levels of proteins were tested by Western blotting. The binding effect of miR-1275 and neuromedin U type 1 receptor (NMUR1) was detected by dual-luciferase activity assay. The results showed that miR-1275 was upregulated in OGD/R-stimulated cardiomyocytes. Inhibition of miR-1275 suppressed the increased activity of LDH and CK, cell apoptosis, reactive oxygen species (ROS) production, intracellular Ca²⁺ concentration and sarcoplasmic reticulum (SR) Ca²⁺ leak induced by OGD/R treatment in cardiomyocytes. miR-1275 directly targets 3'UTR of NMUR1 and negatively regulates NMUR1 expression. Silence of NMUR1 abolished the protecting effect of the miR-1275 antagomir on myocardial OGD/R injury. Our study indicated that the miR-1275 antagomir protects cardiomyocytes from OGD/R injury through the promotion of NMUR1.

Isobaric tags for relative and absolute quantitation‑based proteomics reveals potential novel biomarkers for the early diagnosis of acute myocardial infarction within 3 h

Acute myocardial infarction (AMI) is one of the most common and life-threatening cardiovascular diseases. However, the ability to diagnose AMI within 3 h is currently lacking. The present study aimed to identify the differentially expressed proteins of AMI within 3 h and to investigate novel biomarkers using isobaric tags for relative and absolute quantitation (ITRAQ) technology. A total of 30 beagle dogs were used for establishing the MI models successfully by injecting thrombin powder and a polyethylene microsphere suspension. Serum samples were collected prior to (0 h) and following MI (1, 2 and 3 h). ITRAQ-coupled liquid chromatography-mass spectrometry (LC-MS) technology was used to identify the differentially expressed proteins. The bioinformatics analysis selected several key proteins in the initiation of MI. Further analysis was performed using STRING software. Finally, western blot analysis was used to evaluate the results obtained from ITRAQ. In total, 28 proteins were upregulated and 23 were downregulated in the 1 h/0 h group, 28 proteins were upregulated and 26 were downregulated in the 2 h/0 h group, and 24 proteins were upregulated and 19 were downregulated in the 3 h/0 h group. The Gene Ontology (GO) annotation and functional enrichment analysis identified 19 key proteins. Protein-protein interactions (PPIs) were investigated using the STRING database. GO enrichment analysis revealed that a number of key proteins, including ATP synthase F1 subunit β (ATP5B), cytochrome c oxidase subunit 2 and cytochrome c, were components of the electron transport chain and were involved in energy metabolism. The western blot analysis demonstrated that the expression of ATP5B decreased significantly at all three time points (P<0.01), which was consistent with the ITRAQ results, whereas the expression of fibrinogen γ chain increased at 2 and 3 h (P<0.01) and the expression of integrator complex subunit 4 increased at all three time points (P<0.01), which differed from the ITRAQ results. According to the proteomics of the beagle dog MI model, ATP5B may serve as the potential biomarkers of AMI. Mitochondrial dysfunction and disruption of the electron transport chain may be critical indicators of early MI within 3 h. These finding may provide a novel direction for the diagnosis of AMI.

Understanding cardiac extracellular matrix remodeling to develop biomarkers of myocardial infarction outcomes

Cardiovascular Disease (CVD) is the most common cause of death in industrialized countries, and myocardial infarction (MI) is a major CVD with significant morbidity and mortality. Following MI, the left ventricle (LV) undergoes a wound healing response to ischemia that results in extracellular matrix (ECM) scar formation to replace necrotic myocytes. While ECM accumulation following MI is termed cardiac fibrosis, this is a generic term that does not differentiate between ECM accumulation that occurs in the infarct region to form a scar that is structurally necessary to preserve left ventricle (LV) wall integrity and ECM accumulation that increases LV wall stiffness to exacerbate dilation and stimulate the progression to heart failure. This review focuses on post-MI LV ECM remodeling, targeting the discussion on ECM biomarkers that could be useful for predicting MI outcomes.

Novel Risk Stratification Assays for Acute Coronary Syndrome

PURPOSE OF REVIEW

Since identification of aspartate aminotransferase as the first cardiac biomarker in the 1950s, there have been a number of new markers used for myocardial damage detection over the decades. There have also been several generations of troponin assays, each with progressively increasing sensitivity for troponin detection. Accordingly, the "standard of care" for myocardial damage detection continues to change. The purpose of this paper is to review the clinical utility, biological mechanisms, and predictive value of these various biomarkers in contemporary clinical studies.

RECENT FINDINGS

As of this writing, a fifth "next" generation troponin assay has now been cleared by the US Food and Drug Administration for clinical use in the USA for subjects presenting with suspected acute coronary syndromes. Use of these high-sensitivity assays has allowed for earlier detection of myocardial damage as well as greater negative predictive value for infarction after only one or two serial measurements. Recent algorithms utilizing these assays have allowed for more rapid rule-out of myocardial infarction in emergency department settings. In this review, we discuss novel assays available for the risk assessment of subjects presenting with chest pain, including both the "next generation" cardiac troponin assays as well as other novel biomarkers. We review the biological mechanisms for these markers, and explore the positive and negative predictive value of the assays in clinical studies, where reported. We also discuss the potential use of these new markers within the context of future clinical care in the modern era of higher sensitivity troponin testing. Finally, we discuss advances in new platforms (e.g., mass spectrometry) that historically have not been considered for rapid in vitro diagnostic capabilities, but that are taking a larger role in clinical diagnostics, and whose prognostic value and power promise to usher in new markers with potential for future clinical utility in acute coronary syndrome.

Diagnostic parameters of CK–MB and myoglobin related to chest pain duration

Objective:

Cardiac marker sensitivity depends on chest pain duration at the time of sampling. Our objective was to estimate the sensitivity, specificity, and likelihood ratios of early CK–MB and myoglobin assays in patients presenting to the emergency department (ED) with nondiagnostic ECGs, stratified by the duration of ongoing chest pain at the time of ED assessment.

Methods:

This was a prospective observational study carried out in 10 US and 2 Canadian EDs. Patients &gt;25 years of age with ongoing chest pain and nondiagnostic ECGs were stratified by pain duration (0–4 h, 4–8 h, 8–12 h, &gt;12 h). CK–MB and myoglobin assays were drawn at T = 0 (ED assessment) and T = 1 hr. Patients were followed for 7–14 days to identify all cases of acute myocardial infarction (AMI). ED test results were correlated with patient outcomes.

Results:

Of 5005 eligible patients, 565 had AMI. Pain duration was 0–4 h in 3014 patients, 4–8 h in 961, 8–12 h in 487, and &gt;12 h in 543. Marker sensitivity increased with pain duration, ranging from 28%–77% for CK–MB and 39%–73% for myoglobin. The maximal sensitivity achieved by a T = 0 assay was 73%, and this was in patients with 8–12 or &gt;12 h of ongoing pain. No combination of tests achieved 90% sensitivity in any pain duration strata.

Conclusions:

Regardless of chest pain duration, single assays and early serial markers (0+1 hr) do not rule out AMI; therefore, serial assays over longer observation periods are required. Likelihood ratios derived in this study will help physicians who use Bayesian analysis to determine post-test AMI likelihood in patients with chest pain.

Comparison of Mass Versus Activity of Creatine Kinase MB and Its Utility in the Early Diagnosis of Re-infarction

Currently employed markers for the detection of acute coronary syndrome are Troponin T, CK (Creatine Kinase) and CKMB activity. CKMB activity measured by immunoinhibition method can give falsely elevated results due to the presence of atypical CK and CKBB and at times lead to the mis-diagnosis of acute coronary syndrome. Hence, CKMB mass (CKMB) measured by electrochemiluminence sandwich principle was employed. In this cross-sectional study 183 samples of 61 patients were analyzed within 6 h of diagnosis of acute coronary syndrome and followed up to 72 h. The correlation coefficient between CKMB activity and CKMBM at 4-6 h was 0.744, while at 12-24 h it was 0.909 and at 48-72 h it was 0.337. Thus there was good association between the two methods at 12-24 h but, statistically for method comparison studies and for replacing one method by another, the two methods need to be in agreement with one another. In this study the two methods are not in agreement with one another and thus analytically not replaceable. Another finding was obtained that CKMBM reached cut off levels prior to CKMB enzyme activity and hence, CKMBM is clinically better than CKMB activity to detect reinfarction.

Diagnostic time course, treatment, and in-hospital outcomes for patients with ST-segment elevation myocardial infarction presenting with nondiagnostic initial electrocardiogram: a report from the American Heart Association Mission: Lifeline program

BACKGROUND

Prior studies indicate that a subset of patients diagnosed as having ST-segment elevation myocardial infarction (STEMI) will have an initial non-diagnostic electrocardiogram (ECG) during evaluation. However, the timing of diagnostic ECG changes in this group is unknown. Our primary aim was to describe the timing of ECG diagnosis of STEMI in patients whose initial ECG was non-diagnostic. Secondarily, we sought to compare the delivery of American College of Cardiology/American Heart Association guidelines-based care and in-hospital outcomes in this group compared with patients diagnosed as having STEMI on initial ECG.

METHODS

We analyzed data from 41,560 patients diagnosed as having STEMI included in the National Cardiovascular Data Registry ACTION Registry-GWTG from January 2007 to December 2010. We divided this study population into 2 groups: those diagnosed on initial ECG (N = 36,994) and those with an initial non-diagnostic ECG that were diagnosed on a follow-up ECG (N = 4,566).

RESULTS

In general, baseline characteristics and clinical presentations were similar between the 2 groups. For patients with an initial non-diagnostic ECG, 72.4% (n = 3,305) had an ECG diagnostic for STEMI within 90 minutes of their initial ECG. There did not appear to be significant differences in the administration of guideline-recommended treatments for STEMI, in-hospital major bleeding (P = .926), or death (P = .475) between these groups.

CONCLUSIONS

In a national sample of patients diagnosed as having STEMI, 11.0% had an initial non-diagnostic ECG. Of those patients, 72.4% had a follow-up diagnostic ECG within 90 minutes of their initial ECG. There did not appear to be clinically meaningful differences in guidelines-based treatment or major inhospital outcomes between patients diagnosed as having STEMI on an initial ECG and those diagnosed on a follow-up ECG.

Novel cardiac-specific biomarkers and the cardiovascular continuum

The concept of the cardiovascular continuum, introduced during the early 1990s, created a holistic view of the chain of events connecting cardiovascular-related risk factors with the progressive development of pathological-related tissue remodelling and ultimately, heart failure and death. Understanding of the tissue-specific changes, and new technologies developed over the last 25-30 years, enabled tissue remodelling events to be monitored in vivo and cardiovascular disease to be diagnosed more reliably than before. The tangible product of this evolution was the introduction of a number of biochemical markers such as troponin I and T, which are now commonly used in clinics to measure myocardial damage. However, biomarkers that can detect specific earlier stages of the cardiovascular continuum have yet to be generated and utilised. The majority of the existing markers are useful only in the end stages of the disease where few successful intervention options exist. Since a large number of patients experience a transient underlying developing pathology long before the signs or symptoms of cardiovascular disease become apparent, the requirement for new markers that can describe the early tissue-specific, matrix remodelling process which ultimately leads to disease is evident. This review highlights the importance of relating cardiac biochemical markers with specific time points along the cardiovascular continuum, especially during the early transient phase of pathology progression where none of the existing markers aid diagnosis.

Testing of low-risk patients presenting to the emergency department with chest pain: a scientific statement from the American Heart Association

The management of low-risk patients presenting to emergency departments is a common and challenging clinical problem entailing 8 million emergency department visits annually. Although a majority of these patients do not have a life-threatening condition, the clinician must distinguish between those who require urgent treatment of a serious problem and those with more benign entities who do not require admission. Inadvertent discharge of patients with acute coronary syndrome from the emergency department is associated with increased mortality and liability, whereas inappropriate admission of patients without serious disease is neither indicated nor cost-effective. Clinical judgment and basic clinical tools (history, physical examination, and electrocardiogram) remain primary in meeting this challenge and affording early identification of low-risk patients with chest pain. Additionally, established and newer diagnostic methods have extended clinicians' diagnostic capacity in this setting. Low-risk patients presenting with chest pain are increasingly managed in chest pain units in which accelerated diagnostic protocols are performed, comprising serial electrocardiograms and cardiac injury markers to exclude acute coronary syndrome. Patients with negative findings usually complete the accelerated diagnostic protocol with a confirmatory test to exclude ischemia. This is typically an exercise treadmill test or a cardiac imaging study if the exercise treadmill test is not applicable. Rest myocardial perfusion imaging has assumed an important role in this setting. Computed tomography coronary angiography has also shown promise in this setting. A negative accelerated diagnostic protocol evaluation allows discharge, whereas patients with positive findings are admitted. This approach has been found to be safe, accurate, and cost-effective in low-risk patients presenting with chest pain.

Laboratory approach to the management of clinical emergencies: a diagnostic series

This article emphasizes on the laboratory investigations that may play a significant role in the prompt management of the patient. Hence, other conditions where laboratory investigations will not play a major role are not included in this article. An attempt has been made to highlight certain issues wherein we can prevent inadvertent ordering of tests to minimize the burden on the overworked emergency laboratory, without compromising patient care. The conditions that will be dealt here include: acute chest pain, acute abdominal pain, road traffic injuries, acute respiratory distress, high grade fever, vomiting, loss of consciousness, poisoning and laboratory accidents, and lastly occupational exposure to potential biological hazards.

Chest pain unit concept: rationale and diagnostic strategies

Each year in the United States, over 8 million patients present to the emergency department(ED) with complaints of chest discomfort or other symptoms consistent with possible acute coronary syndrome (ACS). While over half of these patients are typically admitted for further diagnostic evaluation, fewer than 20% are diagnosed with ACS. With hospital beds and inpatient resources scarce, these admissions can be avoided by evaluating low- to moderate-risk patients in chest pain units. This large, undifferentiated patient population represents a potential high-risk group for emergency physicians requiring a systematic approach and specific ED resources. This evaluation is required to appropriately determine if a patient is safe to be discharged home with outpatient follow-up versus requiring admission to the hospital for monitoring and further testing.

The sensitivity of cardiac markers stratified by symptom duration

We compared the sensitivity of three commonly used cardiac markers between two subpopulations, those who came to the Emergency Department (ED) late (6-24 h) after their symptoms began, and those who arrived earlier (<6 h), in a prospective comparative trial. Among all adult patients who presented to our ED with symptoms suggestive of acute myocardial infarction (MI), we drew serum for myoglobin, CK-MB, and troponin I upon arrival (time 0) and 2 h later. Outcomes, including acute MI, were determined. Sensitivities for all three markers between the subpopulations who arrived fewer than 6 h from symptom onset were compared to those who arrived later (6-24 h). We enrolled 346 eligible subjects, 36% of whom described cardiac symptoms as beginning 6 or more hours earlier; 14% suffered acute MIs. For time 0, the sensitivity of all three markers for acute MI was significantly higher among those subjects with symptoms of 6 or more hours' duration as compared to those with less. For troponin I, the increase in sensitivity between these two subpopulations approached 300%. At the time of the 2-h sample, the differences in sensitivities were much less and were not statistically significant. We conclude that cardiac marker values obtained at time 0 among Emergency Department patients who arrive 6 or more hours after cardiac symptom onset provide significantly higher sensitivities as compared to those obtained in patients who arrive earlier. For troponin I, the increase in sensitivity approaches threefold.

Early use of glycoprotein IIb/IIIa inhibitors in the ED treatment of non-ST-segment elevation acute coronary syndromes: a local quality improvement initiative

A prospective observational study was conducted in 2,007 patients experiencing chest pain to determine impact of local quality improvement (QI) measures on the use of glycoprotein (GP) IIb/IIIa inhibitors in the ED treatment of high-risk patients with non-ST-segment elevation acute coronary syndromes (ACS). Patients with injury on the initial ECG or new sustained injury on continuous ECG were excluded. QI interventions were as follows: control (0-4 mo): no interventions (standardized protocols and prewritten orders in place 4 months prior); phase I (5-8 mo): simple education/awareness program with posted drug information pamphlets and eligibility criteria; phase II (9-12 mo): mandated QI form with real-time feedback and focused one-on-one physician education championed by an ED physician QI advocate. A total of 179 (8.9%) of the study patients met predefined high-risk criteria. Of these, a total of 41 (23.0%) patients had GP IIb/IIIa inhibitor therapy initiated in the ED. Percent of high-risk patients receiving therapy increased from 6.0% during the control phase to 16.1% during phase I and 50.9% during phase II. After controlling for patient demographics, patients treated during phase I had a 2.8 times increased odds (95% confidence interval CI: 0.8-10.3; P =.11 [not significant]) of receiving GP IIb/IIIa inhibitor relative to the control phase, and patients treated during phase II had a 20.2 times increased odds (95% CI: 6.1-66.9; P <.0001) of treatment. In conclusion, local QI measures incorporating standardized protocols, preprinted orders, physician education, and interactive feedback championed by an ED QI physician advocate can increase early use of GP IIb/IIIa inhibitors in the ED treatment of high-risk patients presenting with chest pain.

Prospective evaluation of emergency department patients with potential coronary syndromes using initial absolute CK-MB vs. CK-MB relative index

We compared the predictive properties of an initial absolute creatine kinase-MB (CK-MB) to creatine kinase-MB relative index (CK-MB RI) for detecting acute myocardial infarction (AMI), acute coronary syndromes (ACS), and serious cardiac events (SCE). Consecutive patients > 24 years of age with chest pain who received an electrocardiogram (EKG) as part of their Emergency Department (ED) evaluation had CK and CK-MB drawn at presentation. Patients were followed prospectively during their hospital course. The main outcome was AMI, ACS or SCE (death, AMI, dysrhythmias, CHF, PTCA/stent, CABG) within 30 days. The sensitivity, specificity, PPV and NPV of CK-MB and CK-MB RI to predict AMI, ACS, and SCE were calculated with 95% CIs. We enrolled 2028 patients. There were 105 patients (5.2%) with AMI, 266 (13.1%) with ACS, and 150 with SCE (7.4%). Absolute CK-MB had a higher sensitivity than CK-MB RI for AMI (52.0 vs. 46.9, respectively), ACS (23.5 vs. 20.8, respectively), and SCE (39.6 vs. 36.0, respectively), but a lower specificity than CK-MB RI for AMI (93.2 vs. 96.1, respectively), ACS (93.1 vs. 96.1, respectively) and SCE (93.3 vs. 96.3, respectively); and lower PPV for AMI (35.7 vs. 46.5, respectively), ACS (42.0 vs. 53.4, respectively) and SCE (38.5 vs. 50.5, respectively). The negative predictive values were similar for all outcomes. We conclude that the risk stratification of ED chest pain patients by absolute CK-MB has higher sensitivity, similar NPV, but a lower specificity and PPV than CK-MB relative index for detection of AMI, ACS, and SCE. The optimal test depends upon the relative importance of the sensitivity or specificity for clinical decision-making in an individual patient.

The prominent T wave: electrocardiographic differential diagnosis

The prominent T wave is an abnormal T-wave morphology encountered in the earliest phase of ST-segment elevation acute myocardial infarction (AMI). Prominent T waves, however, are associated with other diagnoses, including hyperkalemia, early repolarization, and left ventricular hypertrophy (LVH). This article focuses on the electrocardiographic differential diagnosis of the prominent T wave with the presentation of 4 illustrative cases. We also recommend that the designation hyperacute should refer exclusively to the prominent T waves of ST-segment elevation AMI.

Ruling out myocardial infarction with troponin T and creatine kinase MB mass: diagnostic and prognostic aspects

OBJECTIVE

To investigate the time window for ruling out myocardial infarction (MI) with troponin T (TnT) and creatine kinase isoenzyme MB mass (CK-MBm) and the prognosis of patients with ruled-out MI diagnosis.

DESIGN

The study was based on 397 patients admitted with a suspected acute coronary syndrome but with relief of symptoms within 24 h.

RESULTS

MI diagnosis was confirmed with elevated TnT (>0.10 microg/l) in 108 patients. in 91% within 12-24 h from the onset of symptoms, and in 99% within 12 h from admission. In 94 of these patients CK-MBm became elevated (>5.0 microg/l). in 95% within 10-12 h from the onset of symptoms, and in 99% within 6 h from admission. Among patients with ruled-out MI diagnosis, the 1-year incidence of recurrent coronary events was 29% in those with positive history of coronary heart disease (CHD) but only 7% in those without prior CHD (p < 0.001).

CONCLUSION

Using TnT or CK-MBm, MI can be ruled out within 12 h from admission in the majority of patients. Among patients with ruled-out MI diagnosis, positive history of CHD is an important determinant of prognosis.

Point-of-care testing: a cardiologist's view

The rationale for point-of-care testing is that more rapid provision of biochemical test results performed at the patients bedside will equate with better outcomes. For this to be the case, a number of conditions must be satisfied, and in particular the choice of appropriate markers, an adequate turnaround time (TAT), and an accurate measurement. Point-of-care testing of cardiac markers was found to reduce TAT from 72 (central laboratory) to 20 min thus allowing to decrease total hospital stay.

[Chest pain units: state of the art of the management of patients with chest pain in the emergency department]

Chest pain is one of the most common reasons for patients coming to emergency departments. Most of these individuals end up being hospitalized due to uncertainty of the cause of their complaint. This aggressive and defensive attitude is taken by emergency physicians because some 10 to 30% of these patients actually have acute coronary syndrome. As the admission electrocardiogram and serum CK-MB level have a sensitivity of about 50% for the diagnosis of acute myocardial infarction, serial evaluation is mandatory for non-low risk patients. Inspite of this knowledge, an average of 2-3% of patients with acute myocardial infarction are erroneously released from emergency departments, what is responsible for expensive malpractice suits in the United States. Chest Pain Units were introduced in emergency practice two decades ago to improve medical care quality, reduce inappropriate hospital discharges, reduce unnecessary hospital admissions and reduce medical costs, thus making patient's assessment cost-effective. This is achieved mostly with the use of systematic diagnostic protocols by qualified and trained personnel in the emergency department setting and not in the coronary care unit.

Accuracy of biomarkers to diagnose acute cardiac ischemia in the emergency department: a meta-analysis

STUDY OBJECTIVE

We sought to evaluate quantitatively the evidence on the diagnostic performance of presentation and serial biochemical markers for emergency department diagnosis of acute cardiac ischemia (ACI), including acute myocardial infarction (AMI) and unstable angina.

METHODS

We conducted a systematic review and meta-analysis of the English-language literature published between 1966 and December 1998. We examined the diagnostic performance of creatine kinase, creatine kinase-MB, myoglobin, and troponin I and T testing. Diagnostic performance was assessed by using estimates of test sensitivity and specificity and was summarized by summary receiver-operating characteristic curves.

RESULTS

Only 4 studies were found that evaluated all patients with ACI; 73 were found that focused only on a diagnosis of AMI. To diagnose ACI, presentation biomarker tests had sensitivities of 16% to 19% and specificities of 96% to 100%; serial biomarker tests had sensitivities of 31% to 45% and specificities of 95% to 98%. Considering only the diagnosis of AMI, presentation biomarker tests had summary sensitivities of 37% to 49% and summary specificities of 87% to 97%; serial biomarker tests had summary sensitivities of 79% to 93% and summary specificities of 85% to 96%. Variation of test sensitivity was best explained by test timing. Longer symptom duration or time between serial tests yielded higher sensitivity.

CONCLUSION

The limited evidence available to evaluate the diagnostic accuracy of biomarkers for ACI suggests that biomarkers have very low sensitivity to diagnose ACI. Thus, biomarkers alone will greatly underdiagnose ACI and will be inadequate to make triage decisions. For AMI diagnosis alone, multiple testing of individual biomarkers over time substantially improves sensitivity, while retaining high specificity, at the expense of additional time. Further high-quality studies are needed on the clinical effect of using biomarkers for patients with ACI in the ED and on optimal timing of serial testing and in combination with other tests.

Emergency management of cardiac chest pain: a review

All patients attending an ED with chest pain that could be cardiac should be given a high triage priority to allow rapid assessment and treatment. All patients should receive adequate analgesia and aspirin. Patients with AMI who require fibrinolytic agents should be identified and treatment started. Other high risk patients need inpatient care and may need low molecular weight heparin. Low risk patients require rapid, cost effective and efficacious ROMI protocols, so they can be discharged safely. CPAUs provide the best way of achieving this. Currently the best early protocol seems to be serial CK-MB measurements and continuous ST segment monitoring.

Delta CK-MB outperforms delta troponin I at 2 hours during the ED rule out of acute myocardial infarction

It has been shown that a rise in creatine kinase MB bank (CK-MB) of > or = + 1.6 ng/mL in 2 hours is more sensitive and equally specific for detection of acute myocardial infarction (AMI) as compared with a 2-hour CK-MB > or = 6 ng/mL during the emergency department (ED) evaluation of chest pain. Because cardiac specific troponin I (cTnI) is thought to have similar early release kinetics as compared with CK-MB mass, we undertook a retrospective cohort study in 578 chest pain patients whose baseline CK-MB and cTnI was less than two times the hospital's upper limits of normal and who underwent a 2-hour CK-MB and cTnI to compare sensitivities and specificities of the 2-hour delta CK-MB (deltaCK-MB) and delta cTnI (delta cTnI) for AMI and 30-day Adverse Outcome (AO). Thirty day AO was defined as AMI, life-threatening complication, death, or percutaneous transluminal coronary angioplasty (PTCA)/coronary artery bypass graft (CABG) within 30 days of ED presentation. Optimum delta values were determined by choosing the smallest cutoff value greater than the assay precision where the deltaCK-MB and delta cTnI had a positive likelihood ratio for 30-day AO of > or = 15. A deltaCK-MB > or = +1.5 ng/mL was more sensitive than a deltaTnI > or = +0.2 ng/mL for AMI (87.7% versus 61.4%; P < .0005) and 30-day AO (56.7% versus 42.3%; P < .005). There were no differences in specificities for AMI and 30-day AO. Combining the two tests (MBdelta > or = +1.5 ng/mL and/or a deltaTnI > or = +0.2 ng/mL) resulted in an incremental increase in sensitivity of 89.5% for AMI and 61.9% for AO (P < .005). Patients with either a rise in CK-MB of > or = +1.5 ng/mL or rise in cTnI of > or = +0.2 ng/mL in 2 hours should receive consideration for aggressive antiischemic therapy and further diagnostic testing before making an exclusionary diagnosis of nonischemic chest pain.

Early diagnosis of acute myocardial infarction in patients without ST-segment elevation

Early identification of acute myocardial infarction (AMI) is necessary to initiate appropriate treatment. In patients presenting without ST-segment elevation, diagnosis is often dependent on the presence of elevated myocardial markers. This study examines the ability of serial MB mass alone and in combination with myoglobin in diagnosing AMI in patients without ST-segment elevation within 3 hours of presentation. In all, 2,093 patients were admitted and underwent serial marker analysis using myoglobin, creatine kinase (CK), and CK-MB at 0, 3, 6, and 8 hours. AMI was diagnosed by a CK-MB > or =8.0 ng/ml and a relative index (RI) (CK-MB x 100/total CK) > or =4.0. A total of 186 patients (9%) were diagnosed with AMI. The optimal diagnostic strategy was an elevated CK-MB + RI on the initial or 3-hour sample or at least a twofold increase in CK-MB without exceeding the upper range of normal over the 3-hour time period (sensitivity 93%, specificity 98%). The combination of an elevated CK-MB + RI or myoglobin on the initial or 3-hour sample had a sensitivity of 94%, although specificity was significantly lower, at 86%. Sensitivities and specificities after exclusion of the 242 patients with ischemic electrocardiographic changes were essentially unchanged. We conclude that most patients with AMI presenting with nondiagnostic electrocardiograms can be diagnosed within 3 hours of presentation.

Early laboratory indicators of acute myocardial infarction

Biochemical markers of myocardial injury have evolved so that the diagnosis or exclusion of acute myocardial infarction can be determined within a short time with a high degree of sensitivity and specificity. The use of these markers in patients complaining of chest pain allows for medically appropriate and cost-effective triage decision making in the emergency department.