Delta creatine kinase–MB outperforms myoglobin at two hours during the emergency department identification and exclusion of troponin positive non–ST-segment elevation acute coronary syndromes

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.

Is it prime time for "rapid comprehensive cardiopulmonary imaging" in the emergency department?

Reducing hospital admissions through improved risk stratification of patients with potential acute coronary syndrome represents a critical focus for reducing health care expenditure. Coronary computed tomographic angiography (CTA) has been used with increasing frequency as part of the evaluation of chest pain in the Emergency Department. In the appropriate group of patients at low to intermediate risk CTA appears to be an excellent evaluation strategy, safely and efficiently allowing for the rapid discharge of patients home.

Is coronary computed tomography angiography a resource sparing strategy in the risk stratification and evaluation of acute chest pain? Results of a randomized controlled trial

OBJECTIVES

Annually, almost 6 million U.S. citizens are evaluated for acute chest pain syndromes (ACPSs), and billions of dollars in resources are utilized. A large part of the resource utilization results from precautionary hospitalizations that occur because care providers are unable to exclude the presence of coronary artery disease (CAD) as the underlying cause of ACPSs. The purpose of this study was to examine whether the addition of coronary computerized tomography angiography (CCTA) to the concurrent standard care (SC) during an index emergency department (ED) visit could lower resource utilization when evaluating for the presence of CAD.

METHODS

Sixty participants were assigned randomly to SC or SC + CCTA groups. Participants were interviewed at the index ED visit and at 90 days. Data collected included demographics, perceptions of the value of accessing health care, and clinical outcomes. Resource utilization included services received from both the primary in-network and the primary out-of-network providers. The prospectively defined primary endpoint was the total amount of resources utilized over a 90-day follow-up period when adding CCTA to the SC risk stratification in ACPSs.

RESULTS

The mean (± standard deviation [SD]) for total resources utilized at 90 days for in-network plus out-of-network services was less for the participants in the SC + CCTA group ($10,134; SD ±$14,239) versus the SC-only group ($16,579; SD ±$19,148; p = 0.144), as was the median for the SC + CCTA ($4,288) versus SC only ($12,148; p = 0.652; median difference = -$1,291; 95% confidence interval [CI] = -$12,219 to $1,100; p = 0.652). Among the 60 total study patients, only 19 had an established diagnosis of CAD at 90 days. However, 18 (95%) of these diagnosed participants were in the SC + CCTA group. In addition, there were fewer hospital readmissions in the SC + CCTA group (6 of 30 [20%] vs. 16 of 30 [53%]; difference in proportions = -33%; 95% CI = -56% to -10%; p = 0.007).

CONCLUSIONS

Adding CCTA to the current ED risk stratification of ACPSs resulted in no difference in the quantity of resources utilized, but an increased diagnosis of CAD, and significantly less recidivism and rehospitalization over a 90-day follow-up period.

Management strategies for patients with low-risk chest pain in the emergency department

OPINION STATEMENT

There is abundant evidence to guide the management of chest pain patients with a confirmed or reasonably suspected diagnosis of acute coronary syndrome (ACS). But when it comes to the low-risk chest pain patient in the emergency department, there is limited evidence to support one approach over another. As a result, the evaluation of low-risk chest pain represents a distinct challenge for the emergency physician. Missing a diagnosis of ACS is certainly undesirable. However, the overuse of technology can result in misleading test results in populations with a low incidence of coronary disease. In this article, we dispel several myths surrounding low-risk chest pain and put forward a number of common-sense recommendations. We endorse taking a focused but thorough chest pain history; encourage the use of serial electrocardiogram, particularly for patients with ongoing or changing symptoms; comment on the interpretation of cardiac biomarkers in the era of highly sensitive troponin assays, drawing a distinction between myocardial injury and myocardial infarction; discuss the role of coronary computed tomography angiography as a test for coronary artery disease, rather than for ACS; and caution against the reflexive use of provocative testing in low-risk chest pain patients.

Identification of myocardial injury in the emergency setting

Within the past decade, the use of biomarkers to detect myocardial injury in the emergency department (ED) has been given increasing prominence as evident by the numerous studies and guidelines documenting their use. This review details the scope of the clinical problem, the history of changes in the definition of myocardial infarction (MI) and the new approaches, as well as suggestions for using laboratory biomarkers in the early detection of MI in the ED.

High-risk chief complaints I: chest pain--the big three

Chest pain is one of the most frequently seen chief complaints in patients presenting to emergency departments, and is considered to be a "high-risk" chief complaint. The differential diagnosis for chest pain is broad, and potential causes range from the benign to the immediately life-threatening. Although many (if not most) emergency department patients with chest pain do not have an immediately life-threatening condition, correct diagnoses can be difficult to make, incorrect diagnoses may lead to catastrophic therapies, and failure to make a timely diagnosis may contribute to significant morbidity and mortality. Several atraumatic "high-risk" causes of chest pain are discussed in this article, including myocardial infarction and ischemia, thoracic aortic dissection, and pulmonary embolism. Also included are brief discussions of tension pneumothorax, esophageal perforation, and cardiac tamponade.

Coronary bypass graft patency cannot be determined by multidetector spiral computed tomography

OBJECTIVES

Angiography by selective catheterization is the reference standard for coronary bypass graft patency assessment but carries a risk of serious complications. We have investigated whether 16-slice multidetector spiral computed tomography (MDCT) can substitute for selective angiography.

DESIGN

Two to three years after coronary artery bypass grafting, 45 patients with a total of 156 bypasses (100 single and 28 sequential grafts) were examined with both MDCT and conventional selective angiography on the same day. The bypasses were classified as patent, stenotic or occluded.

RESULTS

The likelihood ratio for MDCT-detected occlusion was 40, reflecting a fairly high combined sensitivity and specificity. However, 24% of the distal anastomoses could not be evaluated by MDCT, mainly because of respiratory movements, artifacts due to metal clips, and small vessel dimensions. Moreover, seven out of 117 bypasses (6%) deemed evaluable by MDCT were wrongly classified by this method.

CONCLUSIONS

At present, 16-slice MDCT cannot replace selective angiography for assessment of coronary bypass graft patency since 24% of bypasses could not be evaluated by this method, and an error rate of 6% is unacceptable.

Interpretation of high sensitivity cardiac troponin I results: reference to biological variability in patients who present to the emergency room with chest pain: case report series

BACKGROUND

The development of highly sensitive cardiac troponin (cTnI) assays has increased the number of true and false positive results for patients suspected of acute myocardial infarction (AMI). Cases are reported whereby the use of serial testing, the 99th percentile cutoff, and the application of biological variation of cTnI were used to help determine ischemic vs. non-ischemic causes of myocardial injury.

METHODS

cTnI was measured using the Siemens Ultra assay from 13 representative patients who presented to the emergency department with symptoms suggestive of acute cardiac disease. Based on a previous study, reference change values of a 46% increase and 32% decrease were used to interpret results. These differences were compared against the patient's discharge diagnosis.

RESULTS

Two patients who subsequently ruled in for AMI had a negative cTnI (<0.04 microg/l) and borderline positive cTnI (0.07 microg/l) at admission, respectively. While the 4-6 h results were also borderline, there was a significant increase from the baseline (+575% and +50%, respectively) to suggest the presence of an acute cardiac event. Two other AMI cases document the significant cTnI decline in results after peak values. In 7 other non-AMI cases (heart and renal failure, gastrointestinal bleeding, stroke and venous thrombosis), while baseline concentrations were clearly positive (0.18-2.12 microg/l), subsequent serial samples were not significantly increased or decreased from baseline. These findings were not typical for AMI. There were 2 cases with acute blunt cardiac trauma and intracranial hemorrhage, respectively, that produced cTnI results that were initially low (<0.04 and 0.05 microg/l, respectively), but significantly increased with serial testing thereby producing false positive Delta cTnI results for AMI.

CONCLUSIONS

Serial testing for troponin was useful in differentiating early AMI from non-ischemic causes of troponin increases. However, non-AMI patients with acute cardiac injury can produce troponin results that mimic AMI. Therefore serial troponin testing must be used in conjunction with clinical presentation and other laboratory findings.

Effects of contemporary troponin assay sensitivity on the utility of the early markers myoglobin and CKMB isoforms in evaluating patients with possible acute myocardial infarction

BACKGROUND

The 2003 American Heart Association (AHA) definition for myocardial infarction (MI) requires an "adequate set" (i.e. at least 6 h between measurements) of biomarkers and specifically troponin for the diagnosis of MI. The aim of the present study was to assess the performance of myoglobin, the CKMB isoforms, and cardiac troponin I (cTnI) in specimens earlier than the requisite 6 h after presentation, in a population originally characterized using World Health Organization (WHO) criteria.

METHODS

In 1996, 228 acute coronary syndrome patients with an "adequate sample set" had their specimens assayed for CKMB isoforms and myoglobin. In 2003, the same specimens were analyzed with the AccuTnI troponin I assay and myoglobin (Beckman Coulter Access immunoassay).

RESULTS

The clinical sensitivities for both myoglobin and the CKMB isoforms were >90% when the population was classified by WHO criteria. However the sensitivities were <70% when the ESC/ACC MI definition was used. Analyzing cTnI at earlier time points as long as there was at least 3 h between specimens or at least 1 specimen 6 h from pain onset did not misclassify subjects based on adverse outcomes in the year following their presentation.

CONCLUSION

Contemporary assays for cTnI with increased analytical sensitivity reduce the utility of myoglobin and CKMB isoforms to rule-out an AMI.

Clinical impact of the troponin 99th percentile cut-off and clinical utility of myoglobin measurement in the early management of chest pain patients admitted to the Emergency Cardiology Department

OBJECTIVE

To verify the clinical impact of different low cut-offs for troponin I/cardiac troponin I (99th percentile to 10% CV) and for myoglobin, in early risk stratification of patients with suspected acute coronary syndrome.

METHODS

A total of 516 consecutive non-ST-elevation patients admitted to hospital were followed. The first measurement of cardiac markers was performed at the point-of-care in the Emergency Cardiology Department, using Stratus CS. The lowest cardiac troponin I concentration with a CV<or=10% (cardiac troponin I concentration=0.07 microg/l) was used to perform an early diagnosis of cardiac damage and to admit non-ST-elevation patients to the Intensive Cardiac Unit. Final diagnosis of acute myocardial infarction was assessed according to European Society of Cardiology and American College of Cardiology diagnostic criteria: cardiac marker follow-up after hospital admission was performed in central laboratory. We retrospectively assessed how the diagnostic accuracy of an early diagnosis of myocardiac damage in the same population might have changed if different lower cardiac troponin I cut-offs had been used upon admitting patients in the Emergency Cardiology Department, independently from the analytical imprecision of the method.

RESULTS

A diagnosis of acute myocardial infarction was performed on 110 (21.3%) of 516 non-ST-elevation-patients admitted to hospital. Seventy (13.6%) patients had cardiac troponin I >0.07 microg/l in the Emergency Cardiology Department (P>0.05). Using lowering cut-off values, the difference between the fraction of patients that was positive compared with the diagnosis according to European Society of Cardiology and American College of Cardiology criteria and had remained statistically significant (P<0.05) up to 0.03 microg/l (99th percentile upper reference limit) was considered (85 patients, 16.5%, n.s.). Relative operating characteristic analysis confirmed that the best clinical cut-off was related to the cardiac troponin I concentration that meets the 99th percentile upper reference limit. The diagnostic accuracy of myoglobin in detecting the minimum cardiac damage was significantly lower, independently from the cut-offs considered.

CONCLUSION

The diagnostic accuracy in detecting myocardial damage early in the Emergency Cardiology Department improves when the 99th percentile is used as a decisional value of cardiac troponin I; the use of this cut-off makes the measurement of myoglobin unnecessary.

Acute coronary syndromes in the emergency department: diagnostic characteristics, tests, and challenges

Failure to diagnose patients who have acute coronary syndromes (ACSs)-either acute myocardial infarction (AMI) or unstable angina pectoris (UAP)-who present to the emergency department (ED) remains a serious public health issue. Better understanding of the pathophysiology of coronary artery disease has allowed the adoption of a unifying hypothesis for the cause of ACSs: the conversion of a stable atherosclerotic lesion to a plaque rupture with thrombosis. Thus, physicians have come to appreciate UAP and AMI as parts of a continuum of ACSs. This article reviews the state of the art regarding the diagnosis of ACSs in the emergency setting and suggests reasons why missed diagnosis continues to occur, albeit infrequently.