Detection of Myocardial Ischemia/Infarction in the Emergency Department Patient with Chest Discomfort

A critical pathway for patients with acute chest pain and low risk for short-term adverse cardiac events: role of outpatient stress testing

STUDY OBJECTIVE

We evaluate the safety and feasibility of a critical care pathway protocol in which patients with acute chest pain who are low risk for coronary artery disease and short-term adverse cardiac outcomes receive outpatient stress testing within 72 hours of an emergency department (ED) visit.

METHODS

We performed an observational study of an ED-based chest pain critical pathway in an urban, community hospital in 979 consecutive patients. Patients enrolled in the protocol were observed in the ED before receiving 72-hour outpatient stress testing. The pathway was primarily analyzed for rates of death or myocardial infarction in the 6 months after ED discharge and outpatient stress testing. Secondary outcome measures included need for coronary intervention at initial stress testing and within 6 months after discharge, subsequent ED visits for chest pain, and subsequent hospitalization.

RESULTS

Of 871 stress-tested patients aged 40 years or older, who had low risk for coronary artery disease and short-term adverse cardiac events, and had 6-month follow-up, 18 (2%) required coronary intervention, 1 (0.1%) had a myocardial infarction within 1 month, 2 (0.2%) had a myocardial infarction within 6 months, 6 (0.7%) had normal stress test results after discharge but required cardiac catheterization within 6 months, and 5 (0.6%) returned to the ED within 6 months for ongoing chest pain. Hospital admission rates decreased significantly from 31.2% to 26.1% after initiation of the protocol (P<.001).

CONCLUSION

For patients with chest pain and low risk for short-term cardiac events, outpatient stress testing is feasible, safe, and associated with decreased hospital admission rates. With an evidence-based protocol, physicians efficiently identify patients at low risk for clinically significant coronary artery disease and short-term adverse cardiac outcomes.

Anxiety and depression following myocardial infarction: gender differences in a 5-year prospective study

OBJECTIVE

The aim of this study was to examine the impact of the first myocardial infarction (MI) and the relative influence of preexisting confounding factors on anxiety and depression in the following 5 years.

METHODS

A total of 23,693 participants, 35-79 years of age at baseline, attended two population-based prospective studies in 1984-1986 and in 1995-1997. They underwent physical examination and self-reported demographic, lifestyle, psychosocial, and medical health characteristics in both surveys. Outcome measure was the Hospital Anxiety and Depression rating Scale (HADS).

RESULTS

Five hundred twelve participants suffered their first MI in the last 5 years before follow-up. Women showed an increased risk for both anxiety and depression in the first 2 years post-MI, followed by a significant symptom reduction. In contrast, the risk for depression in men increased after 2 years post-MI. Anxiety and depression, low educational level, obesity, daily smoking, and physical inactivity pre-MI significantly predicted a poor psychiatric outcome at follow-up.

CONCLUSION

Five-year follow-up after MI revealed gender-specific outcomes of anxiety and depression not previously described.

ELECTROCARDIOGRAPHIC DIAGNOSIS OF ACUTE MYOCARDIAL INFARCTION

The widely recognized benefits of early diagnosis and treatment of acute myocardial infarction (AMI) have only emphasized the importance of emergency physician (EP) competence in electrocardiographic interpretation. As such, the EP must be an expert in the interpretation of the electrocardiogram (ECG) in the emergency department chest pain center patient. The ECG is a powerful clinical tool used in the evaluation of patients, assisting in making the diagnosis of AMI and other syndromes, selecting appropriate therapies (including thrombolysis and primary angioplasty), securing the location of an adequate inpatient disposition, and predicting the risk of cardiovascular complications and death. This article will discuss the appropriate uses of the ECG in the patient with possible or confirmed AMI and review the typical electrocardiographic findings of AMI, diagnostically confounding patterns, mimickers of infarction, and new techniques.

Identification of chest pain patients appropriate for an emergency department observation unit

There are no perfect tests or algorithms to exclude ACI. Because acute coronary occlusion often occurs in patients with low-grade coronary stenosis, the diagnostic goal of a chest pain diagnostic protocol is not to identify patients with CAD, but rather to identify patients who may be safely discharged home without the development of complications such as MI, unstable angina, death, shock, or CHF over the next 1 to 6 months. There is an advantage to evaluating patients at the time of their symptoms. Patients who have a small plaque that is ruptured, leading to intracoronary thrombosis and ischemia, will manifest ischemia on diagnostic testing that could missed in routine outpatient testing when their plaque were stable. The diagnosis and risk stratification of acute coronary ischemia in the ED depends on a careful history and interpretation of the ECG. Multiple regression models using readily available data (e.g., history, physical examination, and ECG) provide the best tools for risk stratification. If one is deciding how to select patients for an EDOU chest pain evaluation, diagnostic tools that have previously been tested and validated in this setting are preferable. These include the Multicenter Chest Pain Study derived tools (i.e., Goldman, Lee), the ACI and ACI-TIPI tools, and sestamibi risk stratification tools. This is not to say that other tools may not play a role at individual institutions. It is probably better to select a consistent approach and evaluate its performance, rather than to allow random variation to dictate practice. The future direction probably will involve standardization of the ED chest pain population. This allows outcome and cost-effectiveness comparative research of various strategies for patients with normal or nondiagnostic ECGs and normal biomarkers. Although this approach allows more precise stratification, the risk will never be zero, meaning that there will never be a substitute for good clinical judgment and close follow-up care.

Cause of ST segment abnormality in ED chest pain patients

The objective of this study was to determine the electrocardiographic diagnoses of chest pain patients with ST segment elevation (STE) on the 12-lead electrocardiogram (ECG). This study was a retrospective ECG review of adult chest pain patients in a university hospital emergency department (ED) over a 3-month period (January 1, 1996 to March 31, 1996). STE was determined if the ST segment was elevated >/=1 mm in the limb leads and >/=2 mm in the precordial leads in at least two anatomically contiguous leads. Results showed 902 patients who met entry criteria and of whom 202 (22.4%) had STE. Thirty-one (15%) patients had STE acute myocardial infarction (AMI) as the final hospital diagnosis which caused the STE; 171 (85%) patients with STE had non-AMI diagnosis responsible for the ST segment elevation, including left ventricular hypertrophy (LVH) 51 (25%), left bundle branch block (LBBB) 31 (15%), benign early repolarization (BER) 25 (12%), right bundle branch block 10 (5%), nonspecific bundle branch block 10 (5%), left ventricular aneurysm 5 (3%), acute pericarditis 2 (1%), ventricular paced rhythm 2 (1%), and undefined ST segment elevation 35 (17%). Forty-four patients had AMI as the final diagnosis of whom 31 showed STE on presentation to the ED. In 2 of 31 (6%) cases of STE AMI, the ST segment waveform was atypical for acute infarction. We concluded that AMI is not the most common cause of STE in ED chest pain patients. LVH is most often responsible for electrocardiographic STE followed by AMI and LBBB which occur at equal frequencies.

The added diagnostic value of automated QT-dispersion measurements and automated ST-segment deviations in the electrocardiographic diagnosis of acute cardiac ischemia

The purpose of this study was to determine the added value of automated QT dispersion and ST-segment measurements to physician interpretation of 12-lead electrocardiograms (ECGs) in patients with chest pain. To date, poor reproducibility of manual measurements and lack of shown added value have limited the clinical use of QT dispersion. Twelve-lead ECGs (n = 1,161) from the Milwaukee Prehospital Chest Pain Database were independently classified by 2 physicians into 3 groups (acute myocardial infarction (AMI), acute cardiac ischemia (ACI), or nonischemic), and their consensus was obtained. QT-end and QT-peak dispersions were measured by a computerized system. The computer also identified ST-segment deviations. Sensitivity, specificity, and positive predictive values (PPVs) and negative predictive values (NPV) for AMI and ACI were evaluated independently and in combinations. For AMI, physicians' consensus classification was remarkably good (sensitivity, 48%, specificity, 99%). Independent classification by QT-end and QT-peak dispersions or ST deviations was not superior to the physicians' consensus. Optimal classification occurred by combining automated QT-end dispersion and ST deviations with physicians' consensus. This combination increased sensitivity for the diagnoses of AMI by 35% (65% vs 48%, P < .001) and ACI by 55% (62% vs 40%, P < .001) compared with physicians' consensus, while maintaining comparable specificity. This study supports a potential clinical role for automated QT dispersion when combined with other diagnostic methods for detecting AMI and ACI.

Electrocardiographic left ventricular hypertrophy in chest pain patients: differentiation from acute coronary ischemic events

Electrocardiographic left ventricular hypertrophy (LVH) and related repolarization changes alter the morphology of the ST segment and/or the T wave. Such electrocardiographic abnormalities--all features that are encountered in patients with acute ischemic heart disease--may confound the early emergency department evaluation of the chest pain patient. In the instance of the chest pain patient demonstrating ST segment/T wave abnormality, the correct electrocardiographic diagnosis must be made not only to offer appropriate management for that particular illness but also to avoid the incorrect application of potentially dangerous therapies such as thrombolysis. This report presents two cases in which the electrocardiogram demonstrated significant repolarization changes consistent with LVH, and focuses on the recognition of the expected ST segment/T waves changes and their differentiation from the primary ST segment/T wave changes associated with acute ischemic heart disease.

Benign early repolarization: electrocardiographic manifestations and differentiation from other ST segment elevation syndromes

Early repolarization, also known as benign early repolarization (BER) or normal variant, is noted in approximately 1% of the population and in up to 48% of patients seen in the emergency department with chest pain. BER represents a benign variant of the normal electrocardiogram and is one of several syndromes producing electrocardiographic ST segment elevation. BER electrocardiographically includes diffuse or widespread ST segment elevation, upward concavity of the initial portion of the ST segment, notching or slurring of the terminal QRS complex, and concordant T waves of large amplitude. This article focuses on BER and includes a discussion of the electrocardiographic tools useful in making this diagnosis and in distinguishing BER from other ST segment elevation syndromes.

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.

Serial ECGs are less accurate than serial CK-MB results for emergency department diagnosis of myocardial infarction

HYPOTHESIS

Serial creatine kinase-MB (CK-MB) levels provide more accurate predictive information regarding myocardial infarction than serial ECGs in emergency department patients with chest discomfort and no ST-segment elevation on the initial ECG.

DESIGN

Prospective, observational study.

SETTING

University hospital and university-affiliated Veterans Affairs Medical Center EDs.

PARTICIPANTS

Two hundred sixty-one patients 30 years or older with chest discomfort warranting an ECG and consenting to observation. Exclusions included hemodynamic or rhythm instability and ST-segment elevation of 0.1 mV or more in two or more electrically contiguous leads at presentation.

MEASUREMENTS

ECGs were obtained at presentation and three to four hours after presentation. Significant serial ECG changes sought on comparison of initial and three- to four-hour ECGs were 0.05 mV or more ST elevation or depression, Q-wave development, or T-wave inversion changes in two or more electrically contiguous leads. CK-MB levels were obtained at presentation and hourly for three hours (positive level, 8 or more ng/mL). Myocardial infarction was determined by record review and was based on independent CK-MB measurements.

RESULTS

Twenty-eight (11%) patients were diagnosed with a myocardial infarction. Thirty-eight (15%) patients had a serial ECG change. Eleven of the myocardial infarction patients (39%) had a serial ECG change compared with 27 (12%) of the non-myocardial infarction patients (P < .001). Sensitivities and specificities of a serial ECG change versus serial CK-MBs for myocardial infarction were 39% versus 68% (sensitivity) and 88% versus 95% (specificity), respectively. Serial CK-MBs were more accurate than a serial ECG change for predicting myocardial infarction (P < .03).

CONCLUSION

Serial changes in ECGs during a three- to four-hour interval were associated with the diagnosis of myocardial infarction but were infrequent and less accurate than serial CK-MB levels obtained for the same interval.

The diagnosis of acute myocardial infarction in the emergency department; Part 1

Despite major advances in treatment, the accurate diagnosis of acute myocardial infarction (AMI) in the emergency department (ED) remains a difficult clinical problem and is still mainly based on the history and interpretation of the electrocardiogram. Although the physician's clinical impression is a highly sensitive indicator for AMI, at least 4% of patients presenting to the ED with AMI may be mistakenly sent home. Although chest pain is the most common chief complaint, the clinical presentation can be extremely variable, particularly in the elderly. Complaints of sharp chest pain or chest wall tenderness should not be relied upon to exclude AMI. Radiation of chest pain is an important symptom. With careful analysis, the electrocardiogram may yield a higher diagnostic sensitivity than is commonly accepted.

A method to describe physician decision thresholds and its application in examining the diagnosis of coronary artery disease based on exercise treadmill testing

The authors developed a method that utilizes logistic regression analysis to 1) calculate the disease probability with confidence intervals at which any specified proportion of physicians reaches a clinical decision, 2) statistically test whether factors other than disease probability affect this clinical decision, and 3) statistically test whether physician decision making in relation to disease probability varies by other factors. They apply the method to analyze the relationship between disease probability and the proportion of physicians who diagnosed coronary artery disease (CAD) in 127 consecutive subjects who completed the treadmill exercise tolerance test (ETT) at two hospitals. Twenty-five percent of the physicians decided that CAD was possible or definite at a post-ETT disease probability of 0.24 (95% CL= 0.07-0.35); 50% at 0.54 (95% CL = 0.43-0.70); and 75% at 0.82 (95% CL = 0.67-1.0). Multivariate logistic regression analysis revealed three factors significantly and independently related to the diagnosis of CAD: post-ETT disease probability, positive ETT result, and cigarette smoking. The proportion of physicians who reached a diagnosis of CAD did not differ by hospital setting (VA versus university), level of training (attending versus housestaff/fellow), or diagnosing service (cardiology versus other internal medicine). It is concluded that factors other than disease probability may affect physician diagnostic decisions.

Value and limitations of current methods of evaluating patients presenting to the emergency room with cardiac-related symptoms for determining long-term prognosis

The goal of this study was to determine the value and limitations of the current approach for evaluating patients in the emergency room (ER) with cardiac-related symptoms in terms of predicting long-term outcome. Accordingly, 274 consecutive prospectively identified patients presenting to the ER with such symptoms were evaluated, and follow-up was obtained at 20 +/- 9 months in 265 of them (97%). Adverse cardiovascular events were defined as: nonfatal myocardial infarction, death, cerebrovascular accident with neurologic deficit, life-threatening arrhythmia and cardiac surgery. Eighty-three patients (31%) had a cardiovascular event during follow-up; 42 occurred within 48 hours of ER presentation, whereas 41 occurred in the ensuing months. Findings on physical examination and electrocardiogram provided additional prognostic information, compared with that of history alone, when added sequentially into a Cox model. However, by discriminant function analysis, only 63% of actual events were correctly predicted by the model. Events occurring after 48 hours of ER presentation were correctly predicted only 50% of the time compared with those occurring within 48 hours of ER presentation, which were correctly predicted 75% of the time (p = 0.04). It is concluded that patients presenting to the ER with cardiac-related symptoms are at high risk for adverse cardiovascular events. The likelihood of an event occurring after 48 hours of presentation is as high as one occurring within 48 hours. Current methods of evaluating such patients have limited prognostic value, particularly for those at long-term risk for events.

Acute myocardial infarction presenting as flank pain and tenderness: report of a case

Studies have demonstrated that 4% to 10% of patients with chest pain and acute myocardial infarction (AMI) are discharged from the emergency department. The patient with an atypical presentation of AMI is difficult to diagnose and has been demonstrated to have an associated increased risk of morbidity and mortality. A case is reported of a patient with AMI presenting to the emergency department with flank pain and tenderness, mimicking acute renal colic.

Safety of immediate treadmill testing in selected emergency department patients with chest pain: a preliminary report

To determine the feasibility and safety of an immediate, symptom-limited, treadmill test on selected emergency department (ED) patients, a convenience sample of 28 patients underwent an exercise treadmill test (ETT) within the first several hours after hospital arrival using the modified Bruce protocol. Patients were included in the study if they presented with otherwise unexplained chest pain consistent with (but not characteristic for) angina pectoris and had a normal electrocardiogram. A negative ETT was seen in 23 of 28 patients, and five of 28 patients had a positive ETT. No patients had serial enzyme or electrocardiogram evolution suggestive of myocardial ischemia, and all patients with a negative ETT were discharged after a full inpatient evaluation designed to rule out unstable coronary disease. At a mean follow-up period of 6.1 months there has been no cardiac morbidity or mortality in the patients with negative ETTs. It was concluded that early ETTS of selected ED patients with chest pain is safe, and an exercise test administered during the ED visit which is negative can preclude unnecessary hospitalization.

Do CK-MB results affect chest pain decision making in the emergency department?

STUDY OBJECTIVE

To analyze the effect of creatine kinase isoenzyme (CK-MB) results on decision making in the evaluation of emergency department patients with chest pain.

DESIGN

Prospective, controlled observational study of clinical decision making.

SETTING

EDs of two teaching hospitals, a Veterans Affairs medical center, and a medical school university hospital.

TYPE OF PARTICIPANTS

Patients more than 30 years old complaining of chest discomfort warranting an ECG. Excluded were hemodynamically unstable patients and patients with ECG evidence of an acute myocardial infarction (AMI).

INTERVENTIONS

After the initial assessment including ECG but not CK-MB data, physicians answered questions regarding estimated probability of AMI and disposition plans. CK-MB levels were drawn every hour for as long as three hours (from one to four CK-MBs) with results readily available. Physicians could admit their patients into the hospital at any time. At disposition after reviewing a second ECG and all available CK-MB data, the physicians answered the same questions and rank ordered the contribution to disposition of the following six factors: initial and serial clinical evaluations, initial and serial ECGs, and initial and serial CK-MB enzymes, respectively. The absolute log likelihood ratio test measured the contribution of CK-MB to decision certainty.

MEASUREMENTS AND MAIN RESULTS

Three hundred seventy-six patients were studied: 29 (7.7%) with AMI and 347 without AMI (nonAMI). Physicians indicated that CK-MB levels were useful for more than one third of study patients. When considered useful, CK-MB results strengthened the impression of AMI in AMI patients and decreased the impression of AMI for nonAMI patients; CK-MB also correlated with the perceived need for cardiac care unit admission in AMI patients and with a reduced need to admit nonAMI patients. The use of CK-MB results did not significantly increase ED release rates.

CONCLUSION

The rapid availability of serial CK-MB results appears to affect decision making in one third of ED patients with chest pain and nondiagnostic ECGs. CK-MB levels appear to complement clinical evaluation of the ED chest pain patient in a manner analogous to the ECG.

Lipoprotein analysis in the evaluation of chest pain in the emergency department

Apolipoproteins were measured in a prospective blinded fashion in blood specimens from patients with chest pain in the emergency department. A definitive diagnosis for the chest pain (non-cardiac-related in 32% and angina or myocardial infarction in 68%) was available in 136 of the 162 patients originally enrolled in the study. Logistic regression and multivariate analysis failed to show any usefulness of apolipoprotein determinations in distinguishing patients with cardiac ischemia from those without it. The clinician's initial impression of the chest pain, the electrocardiogram, a history of previous angina, myocardial infarction, or peripheral atherosclerosis, and male sex were strongly associated with the final diagnosis. We conclude that, although apolipoprotein analysis has proved useful in epidemiologic studies, the most reliable indicators of ischemic pain remain the medical history, the electrocardiogram, and the clinician's overall initial impression.

Missed myocardial ischaemia in the accident & emergency department: E.C.G. a need for audit?

Accident & Emergency Department Senior House Officers rely heavily on their ECG interpretation skills in the diagnosis and management of patients with chest pain. This prospective double-blind study was designed to test the accuracy with which Accident & Emergency Senior House Officers interpret ECGs, by comparing their interpretation with that of a Consultant Cardiologist. ECGs from 279 of 314 consecutive patients with chest pain were analysed. Ninety per cent of normal electrocardiographs and 57% of abnormal ECGs were correctly interpreted. Despite the inaccurate interpretation of 43% of abnormal ECGs, 96.5% of the patients in the study were considered to have been managed correctly. Audit of all ECGs recorded in the Accident & Emergency Department should be undertaken by someone with experience of ECG interpretation. New A&E staff should receive training in the interpretation of ECGs.

Patient flow in the emergency department: the chest pain patient

Prompt treatment of the chest pain patient in the emergency department (ED) is crucial. To ensure prompt treatment, identification of factors that delay flow of these patients through the department is essential. To identify factors that delay patient flow through the ED, the authors conducted a prospective study of all chest pain patients, using a time-flow analysis. Eighty-eight (36%) of 245 patients required critical unit admissions and had an average department stay of 3 1/2 hours. Flow differences were seen between critical and noncritical care patients. Three primary sources of delay were identified: critical unit bed availability, the registration process, and the role of the unit admitting resident. Additional findings confirmed the efficacy and role of the triage nurse in patient flow. Nursing and medical education and staffing needs were addressed. The use of the community's emergency medical services was examined by analyzing the disposition of patients arriving at the ED by ambulance.

The diagnostic impact of prehospital 12-lead electrocardiography

STUDY HYPOTHESIS

It is feasible to apply prehospital 12-lead electrocardiography to most stable prehospital chest pain patients. Prehospital diagnostic accuracy is improved compared with single-lead telemetry.

POPULATION

One-hundred sixty-six stable adult patients who sought paramedic evaluation for a chief complaint of nontraumatic chest pain.

METHODS

One-hundred fifty-one prehospital 12-lead ECGs of diagnostic quality were obtained by paramedics on 166 adult patients presenting with nontraumatic chest pain. Paramedics and base station physicians were blinded to the information on acquired prehospital 12-lead ECGs and treated patients according to current standard of care-clinical diagnosis and single-lead telemetry. Final hospital diagnoses were classified into three groups: acute myocardial infarction (24); suspected angina or ischemia (61); and nonischemic chest pain (66). Paramedics and base station physicians' clinical diagnoses and prehospital and emergency department ECGs were similarly classified and compared. Prehospital and ED 12-lead ECGs were read retrospectively by two cardiologists.

RESULTS

Paramedics achieved a high success rate (98.7%) in obtaining diagnostic quality prehospital 12-lead ECGs in 94.6% of eligible prehospital patients. For patients with acute myocardial infarction, prehospital ECG alone had significantly higher specificity than did the paramedic clinical diagnosis (99.2% vs 70.9%; P less than .001), and significantly higher positive predictive value (92.9% vs 32.7%; P less than .001). For patients with angina, combining the paramedic clinical diagnosis and the prehospital ECG significantly improved sensitivity (90.2% vs 62.3%; P less than .001) and increased negative predictive value (88.9% vs 71.3%; P less than .02) compared with paramedic clinical diagnosis alone. There was a high concordance between prehospital and ED ECG diagnosis (99.3% for acute myocardial infarction and 92.8% for angina). Furthermore, ten patients whose prehospital ECGs demonstrated ischemia and who had final hospital diagnoses of angina or acute myocardial infarction were mistriaged by paramedics and/or received no base station physician-directed therapy.

CONCLUSION

It is feasible to apply prehospital 12-lead electrocardiography to most stable prehospital chest pain patients. Prehospital 12-lead ECGs have the potential to significantly increase the diagnostic accuracy in chest pain patients, approach congruity with ED 12-lead ECG diagnoses, and may allow for consideration of altering and improving prehospital and hospital-based management in this patient population.