Does the emergency room electrocardiogram identify patients with suspected myocardial infarction who are at low risk of acute complications?

Initial presenting electrocardiogram as determinant for hospital admission in patients presenting to the emergency department with chest pain: a pilot investigation

BACKGROUND

Evaluation of chest pain accounts for millions of costly Emergency Department (ED) visits and hospital admissions annually. Of these, approximately 10-20% are myocardial infarctions (MI).

HYPOTHESIS

Patients with chest pain whose initial electrocardiogram (ECG) is normal do not require hospital admission for evaluation and management of a possible myocardial infarction.

METHODS

The medical records of a consecutive cohort of 250 patients who presented to the ED with chest pain and were admitted by the ED physician to a cardiology inpatient service of an academic tertiary care medical center were reviewed. Reasons for admission to hospital was to rule out an acute coronary syndrome, specifically, myocardial infarction. The initial ECG of each patient was evaluated for abnormalities and compared with the final diagnosis.

RESULTS

Of the 75 patients presenting with normal ECGs (normal, upright T waves and isoelectric ST segments), 1 (1.3%) was subsequently diagnosed with a myocardial infarction by Troponin I elevation alone. Of the 55 patients presenting with abnormal ECGs but no clear evidence of ischemia [i.e., left bundle branch block (LBBB), right bundle branch block (RBBB), left anterior hemiblock (LAH)], 2 (3.6%) were diagnosed with MI. Of the 48 patients presenting with abnormal ECGs questionable for ischemia (nonspecific ST and T wave changes that were not clearly ST segment elevation or depression), 7 (14.6%) were diagnosed with an MI. Of the 72 patients who presented with abnormal ECGs showing ischemia (acute ST segment elevation and/or depression), 39 (54.2%) were shown to have evidence for MI.

SUMMARY

Patients who presented with normal ECGs (category 1) were extremely low risk for acute myocardial infarction. Patients with abnormal ECGs but no evidence of definite ischemia (category 2) had a relatively low incidence of MI. Patients with abnormal ECGs questionable for ischemia (category 3) had an intermediate risk of acute myocardial infarction. The majority of patients with abnormal ECGs demonstrating ischemia (category 4) were subsequently shown to evolve an acute myocardial infarction.

CONCLUSIONS

Patients with chest pain and initial ECGs with ST segment abnormalities suggestive or diagnostic for ischemia, should be admitted to the hospital for further evaluation and management. Patients with ECGs that do not display acute ST segment changes are at a lower risk for acute myocardial infarction than those with acute ST segment changes and should be admitted on the basis of cardiac risk profile. (i.e., age, gender, hypertension, diabetes, smoking, known coronary artery disease, etc.) Patients with normal ECGs (category 1) are at extremely low risk, and it may be acceptable to consider further evaluation on an outpatient basis.

Prognostic value of symptoms during a normal or nonspecific electrocardiogram in emergency department patients with potential acute coronary syndrome

OBJECTIVES

Emergency department (ED) patients with symptoms concerning for acute coronary syndrome (ACS) and a normal electrocardiogram (ECG) are at risk for adverse cardiovascular events. The authors hypothesized that patients with a normal or nonspecific ECG during symptoms have a lower risk for ACS than do those who are asymptomatic.

METHODS

This was a prospective cohort study of ED patients with potential ACS. Outcomes were acute myocardial infarction (AMI), ACS, and 30-day cardiovascular events (death, AMI, revascularization). Fisher's exact test, t-tests, and logistic regression were used for data analysis.

RESULTS

Of 2,593 patient visits, 2,007 patients had normal or nonspecific ECG findings. There were 1,196 who had symptoms during ECG, whereas 811 did not. Patients with symptoms at ECG acquisition were younger (49.9 vs. 55.2 years; p < 0.001) and were more likely to be black (70% vs. 64%; p = 0.002), female (63% vs. 58%; p = 0.03), and to have used cocaine (5% vs. 2%; p = 0.004). They were less likely to have hypertension (49% vs. 58%; p < 0.001), and diabetes (22% vs. 17%; p = 0.002). Patients with and without symptoms were equally likely to have AMI (both 2.8%; p > 0.99), ACS (10.1% vs. 11.5%; p = 0.34), and 30-day adverse outcomes (both 5.3%; p > 0.99). After adjustment for baseline cardiovascular-risk factors, odds ratios for patients with symptoms at the time of ECG acquisition were not significantly different for any of the outcomes: AMI (1.1; 95% confidence interval [CI] = 0.6 to 1.9); ACS (1.1; 95% CI = 0.8 to 1.4); or 30-day events (1.2; 95% CI = 0.8 to 1.9).

CONCLUSIONS

Patients who are symptomatic during acquisition of a normal or nonspecific ECG have rates of adverse cardiovascular events similar to those of patients without symptoms. Clinicians should not rely on the absence of ECG abnormalities during symptoms to help exclude ACS.

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.

Diagnosis of acute cardiac ischemia

A better understanding of coronary syndromes allow physicians to appreciate UAP and AMI as part of a continuum of ACI. ACI is a life-threatening condition whose identification can have major economic and therapeutic importance as far as threatening dysrhythmias and preventing or limiting myocardial infarction size. The identification of ACI continues to challenge the skill of even experienced clinicians, yet physicians continue (appropriately) to admit the overwhelming majority of patients with ACI; in the process, they admit many patients without acute ischemia [2], overestimating the likelihood of ischemia in low-risk patients because of magnified concern for this diagnosis for prognostic and therapeutic reasons. Studies of admitting practices from a decade ago have yielded useful clinical information but have shown that neither clinical symptoms nor the ECG could reliably distinguish most patients with ACI from those with other conditions. Most studies have evaluated the accuracy of various technologies for diagnosing ACI, yet only a few have evaluated the clinical impact of routine use. The prehospital 12-lead ECG has moderate sensitivity and specificity for the diagnosis of ACI. It has demonstrated a reduction of the mean time to thrombolysis by 33 minutes and short-term overall mortality in randomized trials. In the general ED setting, only the ACI-TIPI has demonstrated, in a large-scale multicenter clinical trial, a reduction in unnecessary hospitalizations without decreasing the rate of appropriate admission for patients with ACI. The Goldman chest pain protocol has good sensitivity for AMI but was not shown to result in any differences in hospitalization rate, length of stay, or estimated costs in the single clinical impact study performed. The protocol's applicability to patients with UAP has not been evaluated. Single measurement of biomarkers at presentation to the ED has poor sensitivity for AMI, although most biomarkers have high specificity. Serial measurements can greatly increase the sensitivity for AMI while maintaining their excellent specificity. Biomarkers cannot identify most patients with UAP. Finally, diagnostic technologies to evaluate ACI in selected populations, such as echocardiography, sestamibi perfusion imaging, and stress ECG, may have very good to excellent sensitivity; however, they have not been sufficiently studied.

Validation of a tool to safely triage selected patients with chest pain to unmonitored beds

OBJECTIVE

To externally validate a chest pain protocol that triages low risk patients with chest pain to an unmonitored bed.

METHODS

Retrospective study of all patients admitted from the emergency department of a tertiary referral public teaching hospital with an admission diagnosis of 'unstable angina' or suspected ischemic chest pain. Data was collected on adverse outcomes and analysed on the basis of intention-to-treat according to the chest pain protocol.

RESULTS

There were no life-threatening arrhythmias, cardiac arrests or deaths within the first 72 h of admission in the group assigned to an unmonitored bed by the chest pain protocol ([0/244]; 0.0%: 95% confidence interval 0.0-1.5%). Four patients had an uncomplicated myocardial infarction, two patients had recurrent ischemic chest pain and one patient developed acute pulmonary oedema ([7/244]; 2.9%: 95% confidence interval 1.2-5.8%).

CONCLUSION

This retrospective study externally validated the chest pain protocol. Care in a monitored bed would not have altered outcomes for patients triaged to an unmonitored bed by the chest pain protocol. Compared to current guidelines, application of the chest pain protocol could increase the availability of monitored beds.

It is safe to manage selected patients with acute coronary syndromes in unmonitored beds

This prospective, observational study evaluated the safety of the Western Hospital admission protocol for patients with suspected acute coronary syndromes. The study included all patients admitted from the Emergency Department with an admission diagnosis of unstable angina, post infarct angina, atypical chest pain, or chest pain for evaluation. Data collected included demographic data, admission diagnosis, location of admission (bed with or without cardiac monitoring), past medical history and presenting chest pain history to determine Agency for Health Care Policy (AHCPR) and Western Hospital (WH) protocol classifications, cardiac enzyme assays, electrocardiogram analysis, adverse outcomes [death, myocardial infarction (MI), dysrhythmia, acute pulmonary edema, recurrent pain], diagnosis at hospital discharge, and length of stay-(LOS). There were 508 patients with a mean age of 63.7 years enrolled in the study. Three hundred nineteen (62.8%) were admitted to beds without any cardiac monitoring. There was one unexpected death in the unmonitored group, an 85 year-old patient who suffered a presumed dysrhythmia and whom the treating physician had decided was not for resuscitation. Twelve patients suffered nonfatal MI, and none suffered pulmonary edema. All MI patients made an uneventful recovery, and none required thrombolysis. If all patients had been admitted to an area of care based on AHCPR guidelines, an additional 310 admissions to monitored beds would have been required. The results of this study suggest that selected patients with suspected acute coronary syndromes can be safely managed in beds without continuous cardiac monitoring.

The role of nuclear cardiology in clinical decision making

This review suggests that the field of nuclear cardiology is alive, well, and thriving, providing relevant information that aids in everyday clinical decision making for nuclear medicine and referring physicians alike. Despite the competition from other modalities, the clinically appropriate applications of nuclear cardiology techniques are likely to increase. The foundation of this optimism is based on the vast amount of data documenting cost-effective clinical applications for diagnosis, risk stratification, and assessing therapy in both chronic and acute coronary artery disease (CAD), the powerful objective quantitative analysis of perfusion and function provided by the technique, and the increasing general availability of the approach.

Evaluating the chest pain patient. Scope of the problem

With an understanding of the pathophysiology of ACS and an increasing number of early therapeutic options, there has been a shift in focus from ruling-out MI to identifying and stratifying risk in all patients with potential ACS. The presenting symptoms and ECG still remain the cornerstone of immediate diagnosis and triage. Through the application of new technologies, such as the cardiac troponins, and a reassessment of techniques, such as perfusion imaging and echocardiography, the clinician has an increasing selection of methods to rapidly assess chest pain of potential ischemic etiology. Coinciding with the evaluation of technology has been the development of the concept of the CPU and associated rapid diagnostic protocols. These protocols, whether they utilize the assistance of mathematic predictive instruments or represent simple triage schemes, form the backbone of a system to improve the care of patients with ACS in the current milieu of cost containment.

Assessment of the patient with chest pain in the accident and emergency department

This article will review measures enabling emergency staff to identify patients with chest pain who are likely to need admission to a cardiac care unit, in particular those with manifestations of acute ischaemic heart disease--acute myocardial infarction and unstable angina. Other non-cardiac causes of chest pain will also be discussed.

Myocardial infarction with an initially normal electrocardiogram--angiographic findings

To analyze the paradox of acute myocardial infarction (AMI) with an initially normal electrocardiogram (ECG), we reviewed the records of 732 patients discharged with a final diagnosis of AMI over a 2-year period. Twenty-one patient were identified whose initial ECG was normal and who underwent coronary arteriography during the index hospitalization. According to the ECG evolution, three distinct groups were identified: Group 1: those who subsequently developed ST elevation or Q waves (n = 7), Group 2: those who developed ST depression or T-wave inversion (n = 8), and Group 3: those whose ECG remained normal ( n = 6). Peak creatine kinase (CK), timing of the first ECG change, life-threatening complications, and location of the infarct-related coronary lesion were recorded. Infarct-related coronary lesions were also classified into those in a major coronary trunk versus those in secondary branches. The incidence of AMI with a normal ECG was 3.7%. There was no difference in the frequency of coronary artery involvement in the groups studied: left anterior descending (33%), right coronary artery (38%), and circumflex (28%). All ECG changes developed within the first 48 h of hospitalization; 17 +/- 15 in Group 1, and 24 +/- 12 h in Group 2. All six patients who had a persistently normal ECG (Group 3) had lesions in branch vessels (p < 0.05 when compared with Group 1 plus Group 2). Patients who developed ST elevation or Q waves (Group 1) always had a major artery trunk involved (p < 0.05 when compared with Group 2 plus Group 3). Patients in Group 3 had less myocardial damage and fewer complications compared with the other two groups. Myocardial infarction with an initial normal ECG is uncommon and may result from involvement of any of the three coronary arteries. Electrocardiographic evolution usually occurs within the first 48 h of hospitalization. Patients whose ECGs remain normal appear to have culprit lesions in coronary branches, smaller infarctions, and fewer in-hospital complications.

Early CK-MB elevations predict ischemic events in stable chest pain patients

OBJECTIVE

To demonstrate that creatine kinase-MB fraction (CK-MB) elevations within three hours of presentation in the emergency department (ED) are associated with subsequent ischemic events in clinically stable chest pain patients.

METHODS

Prospective cohort study at two university- affiliated teaching hospitals. Participants were consenting ED chest pain patients 25 years old or older without evidence of rhythm or hemodynamic instability (n = 449). Exclusions included ST-segment elevation > or = 0.1 mV in > or = 2 electrocardiogram leads, chest wall trauma, abnormal x-ray studies, and incomplete data collection. Measurements included presenting and three-hour CK-MB levels, presenting ECG, initial clinical impression of coronary care unit need, and clinical follow up. Monitored adverse events included myocardial ischemia necessitating coronary angioplasty or cardiac bypass surgery, recurrent in-hospital myocardial infarction, bradycardia requiring pacing, emergent cardioversion, cardiogenic shock, ventricular fibrillation, and death.

RESULTS

Overall, nine (2%) of 449 patients experienced an ischemic event within the first 48 hours. All nine patients required either coronary angioplasty or bypass surgery. Four (44%) of the nine patients with 48-hour ischemic events had elevated CK-MB levels. Of 23 patients who had complications within one week of ED presentation, seven (30%) had elevated ED CK-MB levels. An elevated CK-MB level was associated with an ischemic event both within 48 hours (risk ratio 9.5; 95% CI 2.7-33.7) and within one week (risk ration 5.2; 95% CI 2.3-11.7).

CONCLUSIONS

An elevated CK-MB level within three hours of ED presentation is associated with a subsequent ischemic event in the clinically stable chest pain patient without ST-segment elevation. However, the ED CK-MB identifies only a minority or otherwise low-risk patients who develop ischemic events; other markers for diagnosing myocardial ischemia in the ED are needed.

Emergency department CK-MB: a predictor of ischemic complications. National cooperative CK-MB project group

OBJECTIVE

To demonstrate that a positive CK-MB in the emergency department (ED) predicts an increased risk for complications of myocardial ischemia in patients admitted to the hospital for evaluation of chest pain.

METHODS

53 academic and community hospital EDs participated in this prospective observational cohort analysis of 5,120 patients with chest pain without ST-segment elevation on the initial ED 12-lead electrocardiogram. All patients were admitted for evaluation of chest pain in one of the participating hospitals as part of the National Cooperative CK-MB Project. Patients were stratified by whether or not they had an elevated CK-MB level in the ED. CK-MB measurements were made on ED presentation and two hours later. Patient medical records were reviewed for inpatient diagnoses--myocardial infarction (MI) or other diagnosis--and for ischemic complication--cardiac-related death, recurrent or delayed in-hospital MI, significant ventricular arrhythmias, new conduction defects, congestive heart failure, and cardiogenic shock.

RESULTS

369 (7.2%) of the 5,120 patients had MI. The proportion of patients with any complication in the MI group was 24%, while the complication rate in the non-MI group was 0.4%. In all patients, regardless of final diagnosis, the relative risk of any complication was 16.1 (95% CI 11.0-23.6) in those with a positive ED CK-MB versus negative ED CK-MB patients. Similarly, the relative risk of death was 25.4 (95% CI 10.8-60.2) in positive ED CK-MB versus negative ED CK-MB patients.

CONCLUSIONS

Multicenter data support the hypothesis that CK-MB measurements can help risk-stratify ED chest pain patients whose initial ECGs are without diagnostic ST-segment elevation.

Prognostic value of the emergency department cardiogram for in-hospital complications of acute myocardial infarction [corrected]

STUDY OBJECTIVE

To identify patients who are admitted from the emergency department with chest discomfort who are at low risk for life-threatening complications.

DESIGN

Retrospective chart review.

SETTING

A 450-bed military medical center providing active duty and military beneficiaries.

TYPE OF PARTICIPANTS

Six hundred twenty-one patients admitted to an ICU from the ED with the chief compliant of chest discomfort.

MEASUREMENTS AND MAIN RESULTS

Study participants were placed into low- and high-risk groups based on clinical criteria and ECGs. The groups were compared with respect to occurrence of life-threatening complications during the hospital course. Three of the 262 patients in the low-risk group experienced life-threatening events; two died. Twenty-nine of the 224 high-risk patients experienced life-threatening events; 17 died . Results were statistically evaluated using Fisher's exact test. Significance was achieved at a value of P < .01.

CONCLUSION

Patients who meet low-risk group criteria have a low likelihood of immediate life-threatening events and could be admitted to an intermediate care unit.