The diagnosis of acute myocardial infarction in the emergency department; Part 2.

At present, routine use of cardiac enzymes in the emergency department (ED) cannot be justified, except possibly as a final screen prior to discharge. Computer-derived predictive instruments do not surpass the physician's diagnostic sensitivity for acute myocardial infarction (AMI), but do demonstrate significantly higher specificity. Limited data exist on the utility of echocardiography and thallium scanning in the ED. Methods of triaging patients on the basis of prognosis are well supported in the literature. The physician's high diagnostic sensitivity is maintained at the cost of significant numbers of admissions who subsequently rule out for AMI. No single clinical variable or combination of clinical variables can reliably confirm or exclude AMI in the ED. Ultimately, the physician's clinical assessment must remain the final determinant of the necessity for admission. However, judicious use of prediction rules and prognostic indicators should improve resource utilization.     

Pitfalls in the emergency department diagnosis of acute myocardial infarction

The accurate assessment and triage of patients with potential ACS is a complex decision-making process based on information that is not entirely reliable. The knowledgeable EP recognizes that assessment of patients with chest pain requires an understanding of the various clinical presentations of ACS and high-risk patient types, as well as careful use of the available modalities to diagnose these syndromes efficiently while incurring minimal risk to the patients safety. The busy EP is faced with sick patients with chest pain daily, so that it behoove anyone in emergency medicine to familiarize themselves with these diagnostic pitfalls.     

Serum markers in the emergency department diagnosis of acute myocardial infarction

No currently used cardiac-specific serum marker meets all the criteria for an "ideal" marker of AMI. No test is both highly sensitive and highly specific for acute infarction within 6 hours following the onset of chest pain, the timeframe of interest to most emergency physicians in making diagnostic and therapeutic decisions. Patients presenting to the ED with chest pain or other symptoms suggestive of acute cardiac ischemia therefore cannot make a diagnosis of AMI excluded on the basis of a single cardiac marker value obtained within a few hours after symptom onset. The total CK level is far too insensitive and nonspecific a test to be used to diagnose AMI. It retains its value, however, as a screening test, and serum of patients with abnormal total CK values should undergo a CK-MBmass assay. Elevation in CK-MB is a vital component of ultimate diagnosis of AMI, but levels of this marker are normal in one fourth to one half of patients with AMI at the time of ED presentation. The test is highly specific, however, and an abnormal value (particularly when it exceeds 5% of the total CK value) at any time in a patient with chest pain is highly suggestive of an AMI. There have been several improvements of CK-MB assay timing and subform quantification that appear highly useful for emergency physicians. Rapid serial CK-MB assessment greatly increases the diagnostic value of the assay in a timeframe suitable for ED purposes but unfortunately still misses about 10% of patients ultimately diagnosed with acute MI. Assays of CK-MB subforms have very high sensitivity, and, although unreliable within 4 hours of symptom onset, have excellent diagnostic value at 6 or more hours after chest pain begins. Automated test assays recently have become available and could prove applicable to ED settings. The cardiac troponins are highly useful as markers of acute coronary syndromes, rather than specifically of AMI, and abnormal values at any time following chest pain onset are highly predictive of an adverse cardiac event. The ED applicability of the troponins is severely limited, however, because values remain normal in most patients with acute cardiac events as long as 6 hours following symptom onset. Myoglobin appeared promising as a marker of early cardiac ischemia but appears to be only marginally more sensitive than CK-MB assays early after symptom onset and less sensitive than CK-MB at 8 hours or more after chest pain starts. Rapid serial myoglobin assessment, however, appears highly useful as an early marker of AMI. The marker has a very narrow diagnostic window. The clinician is left with several tests that are highly effective in correctly identifying patients with AMI (or at high risk for AMI), but none that can dependably exclude patients with acute coronary syndromes soon after chest pain onset. A prudent strategy when assessing ED patients with chest pain and nondiagnostic ECGs is to order CK-MB and troponin values on presentation in the hope of making an early diagnosis of AMI or unstable coronary syndrome. Although it is recognized that normal values obtained within 6 hours of symptom onset do not exclude an acute coronary syndrome, patients at low clinical risk and having normal cardiac marker tests could be provisionally admitted to low-acuity hospital settings or ED observation. After 6 to 8 hours of symptom duration has elapsed, the cardiac-specific markers are highly effective in diagnosing AMI, and such values obtained can be used more appropriately to make final disposition decisions. At no time should results of serum marker tests outweigh ECG findings or clinical assessment of the patient's risk and stability.     

Body surface mapping improves diagnosis of acute myocardial infarction in the emergency department

Traditionally, the diagnosis of acute myocardial infarction (AMI) in emergency departments is done through an assessment of history and presenting symptoms, 12-lead electrocardiogram (ECG), and cardiac biomarkers. The 12-lead ECG is not highly sensitive for detecting ECG changes, and some infarctions may be missed. Failure to identify patients in the early stages of AMI can result in failure to provide beneficial therapies. New technology, the 80-lead ECG, uses body surface mapping to provide a more comprehensive view of cardiac electrical activity. Body surface mapping has greater sensitivity in detecting AMI in the inferoposterior portions of the left ventricle and the right ventricle. Portable hardware and user-friendly software coupled with an easily applied disposable torso vest containing the electrodes produce a 12-lead ECG, 80-lead ECG, and color contour torso or flat map showing ECG changes. Recent studies support the use of 80-lead body surface mapping for detecting AMI in the emergency department.     

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

Introduction  

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

Prognostic significance of interleukin-6 measurement in the diagnosis of acute myocardial infarction in emergency department

BACKGROUND: Markers of inflammation may predict both coronary artery disease (CAD) and adverse outcomes in patients with known CAD. Here, we investigated the role of interleukin-6 (IL-6) in the "triage" and risk assessment of patients admitted to emergency department (ED). METHODS: Serum IL-6 and high sensitivity C-reactive protein (hs-CRP) levels were prospectively evaluated in 88 patients with a history of precordial chest pain or shortness of breath of recent onset (<6 h). RESULTS: Of the 88 patients, 21% were discharged from the ED with diagnosis of non-ischemic chest pain (NICP), 39% had a final diagnosis of unstable angina (UA) and 40% experienced an acute myocardial infarction (AMI). Median IL-6 (p<0.001) and hs-CRP (p<0.01) levels on admission were significantly increased in patients with AMI compared with patients with NICP or UA. IL-6 levels correlated with hs-CRP (p<0.01). Multivariate analyses including known risk factors showed that elevated creatine kinase-MB (p<0.05) and IL-6 levels (p<0.01) were independently associated with a final diagnosis of AMI. Elevated IL-6 levels significantly predicted the risk of AMI (OR=2.47, p=0.006) in chest pain-enzyme negative patients. CONCLUSIONS: IL-6 may behave as an adjunctive diagnostic tool to assist in the risk assessment of enzyme-negative patients with precordial chest pain of recent onset.     

Therapeutic procedures in the emergency department patient with acute myocardial infarction

Life-threatening cardiac arrhythmias and other peri-infarct complications are often unexpected and commonly present with little warning. The therapeutic procedures reviewed often require immediate implementation and should be second nature to any physician involved in the management of patients with an AMI.     

Performance of a sensitive troponin assay in the early diagnosis of acute myocardial infarction in the emergency department

Aim: Troponin assays have high diagnostic value for myocardial infarction (MI), but sensitivity has been weak early after chest pain onset. New, so‐called ‘sensitive’ troponin assays have recently been introduced. Two studies report high sensitivity for assays taken at ED presentation, but studied selected populations. Our aim was to evaluate the diagnostic performance for MI of a sensitive troponin assay measured at ED presentation in an unselected chest pain population without ECG evidence of ischaemia. Methods: This is a sub‐study of a prospective cohort study of adult patients with potentially cardiac chest pain who underwent evaluation for acute coronary syndrome. Patients with clear ECG evidence of acute ischaemia or an alternative diagnosis were excluded. Data collected included demographic, clinical, ECG, biomarker and outcome data. A ‘positive’ troponin was defined as >99th percentile of the assay used. MI diagnosis was as judged by the treating cardiologist. The outcomes of interest were sensitivity, specificity and likelihood ratios (LR) for positive troponin assay taken at ED presentation. Data were analysed by clinical performance analysis. Results: Totally 952 were studied. Median age was 61 years; 56.4% were male and median TIMI score was 2. There were 129 MI (13.6, 95% CI 11.5–15.9). Sensitivity of TnI at ED presentation was 76.7% (95% CI 68.5–83.7%), specificity 93.6% (95% CI 91.7–95.1%), with LR positive 11.92 and LR negative 0.25. Conclusion: Sensitive TnI assay at ED presentation has insufficient diagnostic accuracy for detection of MI. Serial biomarker assays in patients with negative initial TnI are required.     

急诊室内使用瑞替普酶治疗急性心肌梗死的疗效评价

目的比较第三代静注溶栓药物瑞替普酶(rPA)和阿替普酶(rt-PA)对急性心肌梗死(AMI)患者急诊静脉溶栓治疗的临床疗效。方法采用前瞻开放性临床研究方法,观察2004年3月至2006年12月期间在本院急诊室内接受rPA或rt-PA静脉溶栓治疗的AMI患者,共55例,其中rPA组24例,rt-PA组31例,观察血管再通率、死亡率、平均住院天数、心力衰竭及休克等并发症和出血不良反应。结果rPA和rt-PA组的再通率分别为87.50%和83.83%,(P>0.05)。溶栓后30d内心力衰竭、休克及再梗死发生率两组相当,(P>0.05);死亡率分别为8.33%(2例)和6.45%(2例),P>0.05;轻度出血发生率分别66.66%和48.38%,P>0.05;脑出血发生率为8.33%和9.68%,P>0.05;住院天数分别为(10.74±6.49)d和(13.09±13.36)d,P>0.05。结论瑞替普酶适合急诊室内急性心肌梗死患者的静脉溶栓治疗。     

Effects of EMS transportation on time to diagnosis and treatment of acute myocardial infarction in the emergency department

INTRODUCTION. Recent studies have documented decreased time to emergency department (ED) thrombolytic therapy with the use of prehospital electrocardiography. PURPOSE. Is the time to ED diagnosis and treatment of acute myocardial infarction (AMI) patients with thrombolytic agents decreased by emergency medical services (EMS) transport when compared with those transported by other means (non-EMS)? DESIGN. Retrospective, case-control study. POPULATION. The AMI patients treated with thrombolytic agents at a 34,000-visit, community hospital ED during 1992. METHODS. Review of records of patients who received thrombolytic therapy for AMI. Statistical analysis was performed using "Student's" t-test and Yates corrected Chi-square. RESULTS. Eighty-seven patients received thrombolytic agents for AMI during 1992; 33 arrived by ambulance, 54 arrived by other methods. There were no differences in age, gender, or time of ED arrival among these groups. Ambulance patients received standard advanced life support (ALS) care, but not a 12-lead electrocardiogram (ECG) or thrombolytic agents. Ambulance patients experienced a significantly shorter time to first ECG (12.9 +/-9.1 min. versus 20.8 +/-25.3 min.; p = .028) and received thrombolytic therapy sooner than did controls (56.0 +/-31.5 min. versus 78.0 +/-63.4 min.; p = .018). There was no difference in time from diagnosis to treatment between these groups. CONCLUSION. Emergency medical services transport of AMI patients in this study decreased time to diagnosis and treatment and may be a confounder in studies that assess the value of field EMS interventions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Biochemical markers in the management of suspected acute myocardial infarction in the emergency department

Objectives—To compare cardiac troponin T, myoglobin, CK, CKMB activity, CKMB mass and the initial electrocardiogram in the early diagnosis of myocardial infarction in the emergency department.

Methods—Biochemical markers were measured at presentation in patients with a possible diagnosis of acute myocardial infarction. Based on the clinical notes, patients were grouped as "definite myocardial infarction" (n = 50), "definite no myocardial infarction" (n = 81) and "uncertain" (n = 96). Sensitivity and specificity and positive and negative predictive values were calculated using the 131 patients with definitely present or absent myocardial infarction.

Results—The initial electrocardiogram was more sensitive than any of the markers in the first six hours from symptom onset—sensitivity 74% (95%CI 61% to 88%). The positive predictive value of the initial electrocardiogram was 97% in the first six hours; the markers ranged from 47% to 67%. The negative predictive value of the initial electrocardiogram was 85% in the first six hours; the markers ranged from 61% to 70%. Four patients with non-diagnostic electrocardiograms presenting beyond six hours after pain onset had a myocardial infarct detected by at least three of the biochemical markers in each case.

Conclusions—The electrocardiogram is of more diagnostic use than biochemical markers in the first six hours after the onset of pain, but biochemical markers give additional positive diagnostic information in patients presenting later than this. The negative predictive accuracy of biochemical markers is too low for a single sample to be useful for excluding myocardial infarction in the first six hours after onset of symptoms.

     

Delay in thrombolytic treatment in acute myocardial infarction: the role of the accident and emergency department.

During a 6-week period, 248 patients presenting with chest pain presumed to be cardiac in origin, were recruited in a time and motion study in the Accident and Emergency Department of the Leicester Royal Infirmary. The study considered the ambulance-response and transfer times from the scene to the hospital, as well as the duration of the patients stay in the Department. While Ambulance Time from the scene of the incident to the hospital averaged 28 min, the time spent in the Accident and Emergency Department prior to admission averaged 76.5 min. This study was conducted in the light of growing concern expressed at the delay in administering thrombolytic agents to those patients with acute myocardial infarction (AMI). The authors propose possible ways of reducing such delays.     

Beta-blocker use in the emergency department in patients with acute myocardial infarction undergoing primary angioplasty

Our objectives were to evaluate the frequency of β-blocker administration in the setting of acute myocardial infarction (AMI) where angioplasty is the primary treatment, and to investigate Emergency Physician’s (EPs) attitudes toward β-blockers. We performed a retrospective chart review of all patients who presented with symptoms and electrocardiogram (EKG) criteria consistent with AMI in the defined study period. Charts were reviewed for β-blocker administration and other treatments. A survey was subsequently distributed to all EPs to determine self-reported reasons for withholding β-blockers. There were 91 patients identified. Of those who did not have contraindications, 99% (89/90) received aspirin, 97% (88/91) received heparin, 94% (84/89) received nitrates, but only 28% (19/68) received β-blockers. Ninety-six percent of β-blocker-eligible patients received them as inpatients. Eighty-six percent (44/52) of EPs completed the survey. Physicians felt strongly about avoiding β-blockers in patients with asthma exacerbation, severe congestive heart failure, and high degree AV block. Bradycardia was the most frequent reason for withholding β-blockers. In this series of patients presenting with AMI, β-blockers were greatly underutilized. The self-reported reasons of EPs for withholding β-blocker therapy did not explain why 72% (49/68) of patients without contraindications did not receive β-blockers.     

Thrombolysis in acute myocardial infarction: the safety and efficiency of treatment in the accident and emergency department.

OBJECTIVES: To assess the safety and efficiency with which the accident and emergency (A&E) department provides thrombolytic treatment for patients with acute myocardial infarction (AMI). METHODS: A prospective observational study based in a teaching hospital for one year. All patients who presented with the clinical and electrocardiographic indications for thrombolytic treatment were studied. Patients were grouped according to route of admission. After logarithmic transformation, the "door to needle times" of the groups were compared using a two tailed Student's t test. Arrhythmias and complications after thrombolytic treatment were noted. The appropriateness of the treatment was assessed retrospectively by review of the clinical records and electrocardiograms, judged against locally agreed eligibility criteria. RESULTS: Data from 153 patients were analysed; 138/153 (90%) patients were admitted via the A&E department. The shortest door to needle times were seen in those patients thrombolysed by A&E staff within the A&E department (mean 43.8 minutes). The transfer of A&E patients to the coronary care unit (CCU) was associated with a significant increase in the door to needle time (mean 58.8 minutes, p = 0.004). Only one malignant arrhythmia occurred during the administration of thrombolysis in the A&E department, and this was managed effectively. No arrhythmias occurred during transfer of thrombolysed patients to the CCU. In every case, the decision to administer thrombolysis was retrospectively judged to have been appropriate. CONCLUSIONS: The A&E department provides appropriate, safe, and timely thrombolytic treatment for patients with AMI. Transferring A&E patients to the CCU before thrombolysis is associated with an unnecessary treatment delay.     

Thrombolysis in acute myocardial infarction: the safety and efficiency of treatment in the accident and emergency department.

OBJECTIVES: To assess the safety and efficiency with which the accident and emergency (A&E) department provides thrombolytic treatment for patients with acute myocardial infarction (AMI). METHODS: A prospective observational study based in a teaching hospital for one year. All patients who presented with the clinical and electrocardiographic indications for thrombolytic treatment were studied. Patients were grouped according to route of admission. After logarithmic transformation, the "door to needle times" of the groups were compared using a two tailed Student's t test. Arrhythmias and complications after thrombolytic treatment were noted. The appropriateness of the treatment was assessed retrospectively by review of the clinical records and electrocardiograms, judged against locally agreed eligibility criteria. RESULTS: Data from 153 patients were analysed; 138/153 (90%) patients were admitted via the A&E department. The shortest door to needle times were seen in those patients thrombolysed by A&E staff within the A&E department (mean 43.8 minutes). The transfer of A&E patients to the coronary care unit (CCU) was associated with a significant increase in the door to needle time (mean 58.8 minutes, p = 0.004). Only one malignant arrhythmia occurred during the administration of thrombolysis in the A&E department, and this was managed effectively. No arrhythmias occurred during transfer of thrombolysed patients to the CCU. In every case, the decision to administer thrombolysis was retrospectively judged to have been appropriate. CONCLUSIONS: The A&E department provides appropriate, safe, and timely thrombolytic treatment for patients with AMI. Transferring A&E patients to the CCU before thrombolysis is associated with an unnecessary treatment delay.     

急性心肌梗死的诊断探讨

心肌梗死是冠状动脉闭塞,血流中断,导致心肌严重而持久的缺血所引起的心肌坏死.心肌梗死常引起胸骨后或心前区剧烈疼痛,持续1～2小时至1～2天.休息或含硝酸甘油无效,主要表现为：休克、心律失常、心力衰竭及发热.     

急诊应用瑞替普酶尿激酶对急性心肌梗死溶栓的随机对照研究

目的 在急诊科观察瑞替普酶(r-PA)、尿激酶(UK)用于急性心肌梗死(AMI)溶栓治疗的疗效和不良反应.方法 对符合入选标准的87例AMI患者随机分为r-PA组和UK组,在急诊科分别给予r-PA和UK溶栓治疗,其中r-PA组41例,UK组46例,观察两组溶栓后相关冠状动脉再通率,急性期35 d内的死亡率、并发症和不良反应发生率.结果 2 h内溶栓再通率r-PA组36例(87.8%),UK组30例(65.2%),两组比较差异有统计学意义(P<0.05);两组在急性期35 d内死亡率、缺血再发生和并发症比较差异无统计学意义(P>0.05);r-PA组出血不良反应少于UK组,两组比较差异有统计学意义(P<0.05).结论 与UK相比,在急诊室给予AMI患者r-PA溶栓治疗,梗死相关动脉再通率更高,出血不良反应较少.     

Gender disparity in emergency department non-ST elevation myocardial infarction management

Background

Many studies have looked at differences between men and women with acute coronary syndrome. These studies demonstrate that women have worse outcomes, receive fewer invasive interventions, and experience delay in the initiation of established medical therapies.

Objective

Using innovative technology, we set out to unveil and resolve any gender disparities in the evaluation and treatment of patients presenting with a positive troponin while in the emergency department. Our goal was to assess the feasibility of using a business management query system to create an automated data report that could identify deficiencies in standards of care and be used to improve the quality of treatment we provide our patients.

Methods

Over a 12-month period, key markers for patients with non-ST elevation myocardial infarction (NSTEMI) were tracked (e.g., time to electrocardiogram, door to medications). During this time, educational endeavors were initiated utilizing McKesson’s Horizon Business Insight™ (McKesson Information Solutions, Alpharetta, GA) to illustrate gender differences in standard therapy. Subsequently, indicators were evaluated for improvement.

Results

Substantial improvements in key indicators for management of NSTEMI were obtained and gender differences minimized where education was provided.

Conclusion

The integration of these information systems allowed us to create a successful performance improvement tool and, as an added benefit, nearly eliminated the need for manual retrospective chart reviews.