Impact of the electrocardiogram on the delivery of thrombolytic therapy for acute myocardial infarction

Electrocardiographic Early Repolarization in an Emergency Setting: The Subtleties of Electrocardiography

The electrocardiographic pattern of early repolarization (ER) is relatively common in the general population. In patients presenting to the emergency room with chest pain, it can be particularly challenging to distinguish ER from life-threatening subtle ST-segment elevation myocardial infarction (STEMI). A 37-year-old male presented to the emergency department with sudden-onset, severe, non-radiating, central chest pain. The ECG showed Q waves in the inferior leads and a widespread end-QRS notch with J-point elevation mimicking ST elevation in the inferior and lateral precordial leads. Initial cardiac biomarkers were within normal limits. Serial cardiac biomarkers were unremarkable. Echocardiography showed no wall motion abnormalities. A review of prior records from a month ago revealed a similar presentation with similar ECG findings when he underwent cardiac catheterization, revealing normal coronary arteries. Since the ECG was unchanged from the prior one with negative cardiac biomarkers and a negative angiographic study a month ago, no further ischemic risk stratification was indicated. Distinguishing ER from subtle STEMI in patients with acute chest pain can be challenging. A good clinical acumen, along with a comparison of prior ECGs, can aid in decision-making.

Kounis Syndrome Following Hypnale zara (Hump-Nosed Pit Viper) Bite in Sri Lanka

A 47-y-old man was bitten by a hump-nosed viper (Hypnale zara) and gradually developed retrosternal chest pain associated with ST segment elevation on electrocardiogram. He had normal troponin I levels and no evidence of coagulopathy. Initially, he was managed as having anterior ST elevation myocardial infarction with thrombolysis. Later, because troponin levels were normal, he was suggested to have the type I variant of Kounis syndrome (allergic coronary artery spasm). This was supported by high eosinophil counts in peripheral blood. He was successfully managed with supportive treatment and discharged 6 d after the snakebite. Cardiac complications are rarely reported after hump-nosed viper bites, and clinical reports of coronary vasospasm after snakebites are extremely rare in the literature. This is the first known report of Kounis syndrome after a hump-nosed viper bite.

Frequency of Non-ST Segment Elevation Myocardial Infarction (NSTEMI) in Acute Coronary Syndrome With Normal Electrocardiogram (ECG): Insights From a Cardiology Hospital in Pakistan

Introduction

Patients presenting to the emergency department with a non-ST segment elevation myocardial infarction (NSTEMI) frequently have unremarkable electrocardiography (ECG) reports, alluding to the unreliable nature of ECG in diagnosing NSTEMI. This study aims to assess the burden of NSTEMI in acute coronary syndrome (ACS) with unremarkable ECG, elucidating that in patients presenting with acute retrosternal chest pain, NSTEMI should not be excluded unless cardiac enzyme levels are assessed.

Methods

All patients who fulfilled the inclusion criteria in the Department of Cardiology, Tabba Heart Institute, Karachi were included. After obtaining informed written consent, a detailed history was taken. Clinical examination was consequently performed, and an ECG, along with the cardiac enzymes implicated in ACS, such as troponin I, was evaluated. The proportion of normal ECGs in the context of an NSTEMI was duly noted.

Result

A total of 215 patients with ACS presenting within 24 hours of the onset of symptoms, on a background of unremarkable ECG reports, were included. One hundred thirty-eight (64.2%) were males and 77 (35.8%) were females, with the mean age being 54.3 + 7.6 years. A confirmed diagnosis of NSTEMI was made in 49 (22.8%) of the total cases.

Conclusion

The frequency of patients presenting with an NSTEMI within 24 hours of the onset of symptoms, and having normal ECG findings, was strikingly high in patients presenting to the Tabba Heart Institute, Karachi, Pakistan. These findings were more common in males and in older patients.

Diagnostic Decision-Making in the Emergency Department

Emergency medicine requires diagnosing unfamiliar patients with undifferentiated acute presentations. This requires hypothesis generation and questioning, examination, and testing. Balancing patient load, care across the severity spectrum, and frequent interruptions create time pressures that predispose humans to fast thinking or cognitive shortcuts, including cognitive biases. Diagnostic error is the failure to establish an accurate and timely explanation of the problem or communicate that to the patient, often contributing to physical, emotional, or financial harm. Methods for monitoring diagnostic error in the emergency department are needed to establish frequency and serve as a foundation for future interventions.

Fragmented QRS and abnormal creatine kinase-MB are predictors of coronary artery disease in patients with angina and normal electrocardiographys

BACKGROUND/AIMS

Patients with symptoms of coronary artery disease (CAD) often display normal tracings or only nonspecific changes on electrocardiography (ECG). The aim of this study was to explore strategic elements of the ECG and other potential factors that are predictive of CAD in this scenario.

METHODS

This was an observational study of 142 patients with the chief complaint of chest pain, each of whom presented with a normal ECG and was subjected to emergency coronary angiography (CAG). Two population subsets were identified: those patients (n = 97) with no significant stenotic lesions and those (n = 45) with the significant stenotic lesions of CAD.

RESULTS

Those patients with normal or nonspecific ECGs and CAD (15.8%) were more likely to have left circumflex artery involvement (20% vs. 7%). In patients with normal ECGs and CAD (vs. normal CAG), male sex (86.7% vs. 68%, p = 0.023), creatine kinase-MB (CK-MB) levels > 10 U/L (13 vs. 10, p = 0.025), and fragmented QRS (fQRS) (38.6% vs. 21.6%, p = 0.042) occurred with greater frequency. In multivariable analysis, the following variables were significant predictors of CAD, given a normal ECG: male sex (odds ratio [OR], 2.593; 95% confidence interval [CI], 1.068 to 5.839); CK-MB (OR, 2.497; 95% CI, 0.955 to 7.039); and W- or M-shaped QRS complex (OR, 2.306; 95% CI 0.988 to 5.382).

CONCLUSIONS

In our view, male sex, elevated CK-MB (> 10 U/L), and fQRS complexes are suspects for CAD in patients with angina and unremarkable ECGs and should be considered screening tests.

State-of-the-Art Evaluation of Emergency Department Patients Presenting With Potential Acute Coronary Syndromes

It is well established that clinicians cannot use clinical judgment alone to determine whether an individual patient who presents to the emergency department has an acute coronary syndrome. The history and physical examination do not distinguish sufficiently between the many conditions that can cause acute chest pain syndromes. Cardiac risk factors do not have sufficient discriminatory ability in symptomatic patients presenting to the emergency department. Most patients with non-ST-segment-elevation myocardial infarction do not present with electrocardiographic evidence of active ischemia. The improvement in cardiac troponin assays, especially in conjunction with well-validated clinical decision algorithms, now enables the clinician to rapidly exclude myocardial infarction. In patients in whom unstable angina remains a concern or there is a desire to evaluate for underlying coronary artery disease, coronary computed tomography angiography can be used in the emergency department. Once a process that took ≥24 hours, computed tomography angiography now can rapidly exclude myocardial infarction and coronary artery disease in patients in the emergency department.

Incidence, angiographic features and outcomes of patients presenting with subtle ST-elevation myocardial infarction

BACKGROUND

Borderline electrocardiograms represent a challenge in ST-segment elevation myocardial infarction (STEMI) management and are associated with inappropriate discharges and delays to intervention.

OBJECTIVES

To assess angiographic characteristics and outcomes of patients presenting with subtle ST-elevation (STE) myocardial infarction.

METHODS

A total of 504 consecutive patients with suspected STEMI treated by systematic primary percutaneous coronary intervention were prospectively included. Subtle STE was defined as a maximal preinterventional STE of 0.1 to 1 mm. Angiograms were interpreted by investigators unaware of the electrocardiographic data.

RESULTS

The proportion of patients with subtle STE was 18.3%, 86% of them presented with Thrombolysis In Myocardial Infarction flow grade 0/1 and 91% underwent percutaneous coronary intervention. Despite having smaller infarcts, subtle STE patients associated more frequent multivessel disease (57% vs 44%, P = .02) and larger delays to reperfusion. During a follow-up of 19.0 ± 4.9 months, the rates of death or reinfarction were similar among groups (10.0% vs 12.6%, P = .467). Subtle STE was not associated with better outcomes neither in univariate nor after adjustment in a multivariate analysis (adjusted hazard ratio 0.79, 95% CI 0.37-1.69, P = .546).

CONCLUSIONS

Subtle STEMI is frequent in clinical practice and is usually associated with acute total coronary occlusion. Therefore, it should be diagnosed and treated in the same expeditiously manner as marked STEMI.

What decides the suspicion of acute coronary syndrome in acute chest pain patients?

Background

Physicians assessing chest pain patients in the emergency department (ED) base the likelihood of acute coronary syndrome (ACS) mainly on ECG, symptom history and blood markers of myocardial injury. Among these, the ECG has been stated to be the most important diagnostic tool. We aimed to analyze the relative contributions of these three diagnostic modalities to the ED physicians’ evaluation of ACS likelihood in clinical practice.

Methods

1151 consecutive ED chest pain patients were prospectively included. The ED physician’s subjective assessment of the patient’s likelihood of ACS (obvious ACS, strong, vague or no suspicion of ACS), the symptoms and the ECG were recorded on a special form. The ED TnT value was retrieved from the medical records. Frequency tables and logistic regression models were used to evaluate the contributions of the diagnostic tests to the level of ACS suspicion.

Results

Symptoms determined whether the physician had any suspicion of ACS (odds ratio, OR 526 for symptoms typical compared to not suspicious of ACS) since neither ECG nor TnT contributed significantly (ORs not significantly different from 1) to this assessment. ACS was suspected in only one in ten patients with symptoms not suspicious of ACS. Symptoms were also more important (OR 620 for typical symptoms) than ECG (OR 31 for ischemic ECG) and TnT (OR 3.4 for a positive TnT) for the assessment of obvious ACS/strong suspicion versus vague/no suspicion. Of the patients with ST-elevation on ECG, 71% were considered to have an obvious ACS, as opposed to only 6% of those with symptoms typical of ACS and 10% of those with a positive TnT.

Conclusion

The ED physicians used symptoms as the most important assessment tool and applied primarily the symptoms to determine the level of ACS suspicion and to rule out ACS. The ECG was primarily used to rule in ACS. The TnT level played a minor role for the assessment of ACS likelihood. Further studies regarding ACS prediction based on symptoms may help improve decision-making in ED patients with possible ACS.

ST segment elevations: always a marker of acute myocardial infarction?

Chest pain is one of the chief presenting complaints among patients attending Emergency department. The diagnosis of acute myocardial infarction may be a challenge. Various tools such as anamnesis, blood sample (with evaluation of markers of myocardial necrosis), ultrasound techniques and coronary computed tomography could be useful. However, the interpretation of electrocardiograms of these patients may be a real concern. The earliest manifestations of myocardial ischemia typically interest T waves and ST segment. Despite the high sensitivity, ST segment deviation has however poor specificity since it may be observed in many other cardiac and non-cardiac conditions. Therefore, when ST-T abnormalities are detected the physicians should take into account many other parameters (such as risk factors, symptoms and anamnesis) and all the other differential diagnoses. The aim of our review is to overview of the main conditions that may mimic a ST segment Elevation Myocardial Infarction (STEMI).

Frequency of non-ST-segment elevation injury patterns on prehospital electrocardiograms

INTRODUCTION

Prehospital electrocardiograms (ECGs) have been recommended to facilitate early diagnosis of ST-segment elevation myocardial infarction (STEMI). However, prehospital ECGs can also be used to triage patients with non-ST-segment elevation acute coronary syndromes, who comprise a majority of patients with ischemic events presenting by ambulance to overcrowded emergency departments.

OBJECTIVE

We assessed the frequency of non-ST-segment elevation injury patterns on prehospital ECGs in patients with a chief complaint of chest pain evaluated by the emergency medical services (EMS) system.

METHODS

We analyzed prehospital ECGs of patients with the chief complaint of chest pain during a nine-month period. The ECGs were divided into three categories: injury pattern; no injury pattern; and technically uninterpretable. Injury pattern criteria were as follows: 1) regional ST depression >or=1.0 mm; 2) regional T-wave inversion (TWI) >or=3 mm; 3) left bundle branch block (LBBB); and 4) regional ST-segment elevation >or=1.0 mm. Descriptive statistics with 95% confidence intervals (CIs) are presented.

RESULTS

Prehospital ECGs were obtained for 322 of 340 chest pain patients: 72% were men; the average age was 60 years (range 18-96 years). Seventy-seven ECGs (24%, 95% CI 19.3-28.9%) met the criteria for injury pattern, 230 (71%) did not show injury, and 15 (5%) were uninterpretable. Of the 77 ECGs that exhibited an injury pattern, 39 (51%) showed ST depression, seven (9%) TWI, seven (9%) LBBB, and 24 (31%) ST-segment elevation. Thus, non-ST-segment elevation injury patterns (ST depression/TWI/LBBB) accounted for 53 (17%, 95% CI 12.6-20.9) of the total 322 prehospital ECGs.

CONCLUSION

Our findings demonstrate a relatively high frequency (17%) of non-ST-segment elevation injury patterns on prehospital ECGs of patients who summon EMS because of chest pain. These results suggest the potential of prehospital ECGs to facilitate early triage in these high-risk chest pain patients who present to overcrowded emergency departments.

Frequency of acute coronary syndrome in patients with normal electrocardiogram performed during presence or absence of chest pain

OBJECTIVES

The authors hypothesized that patients with active chest pain at the time of a normal electrocardiogram (ECG) have a lower frequency of acute coronary syndrome (ACS) than patients being evaluated for chest pain but with no active chest pain at the time of a normal ECG. The study objective was to describe the association between chest pain in patients with a normal ECG and the diagnosis of ACS.

METHODS

This was a prospective observational study of emergency department (ED) patients with a chief complaint of chest pain and an initial normal ECG admitted to the hospital for chest pain evaluation over a 1-year period. Two groups were identified: patients with chest pain during the ECG and patients without chest pain during the ECG. Normal ECG criteria were as follow: 1) normal sinus rhythm with heart rate of 55-105 beats/min, 2) normal QRS interval and ST segment, and 3) normal T-wave morphology or T-wave flattening. "Normal" excludes pathologic Q waves, left ventricular hypertrophy, nonspecific ST-T wave abnormalities, any ST depression, and discrepancies in the axis between the T wave and the QRS. Patients' initial ED ECGs were interpreted as normal or abnormal by two emergency physicians (EPs); differences in interpretation were resolved by a cardiologist. ACS was defined as follows: 1) elevation and characteristic evolution of troponin I level, 2) coronary angiography demonstrating >70% stenosis in a major coronary artery, or 3) positive noninvasive cardiac stress test. Chi-square analysis was performed and odds ratios (ORs) are presented.

RESULTS

A total of 1,741 patients were admitted with cardiopulmonary symptoms; 387 met study criteria. The study group comprised 199 males (51%) and 188 females (49%), mean age was 56 years (range, 25-90 years), and 106 (27%) had known coronary artery disease (CAD). A total of 261 (67%) patients experienced chest pain during ECG; 126 (33%) patients experienced no chest pain during ECG. There was no difference between the two groups in age, sex, cardiac risk factors, or known CAD. The frequency of ACS for the total study group was 17% (67/387). There was no difference in prevalence of ACS based on the presence or absence of chest pain (16% or 42/261 vs. 20% or 25/126; OR = 0.77, 95% confidence interval = 0.45 to 1.33, p = 0.4).

CONCLUSIONS

Contrary to our hypothesis concerning patients who presented to the ED with a chief complaint of chest pain, our study demonstrated no difference in the frequency of acute coronary syndrome between patients with chest pain at the time of acquisition of a normal electrocardiogram and those without chest pain during acquisition of a normal electrocardiogram.

Electrocardiographic abnormalities mimicking myocardial infarction in a patient with intracranial haemorrhage: a possible pitfall for prehospital thrombolysis

The electrocardiogram, when applied in the prehospital setting, has a significant effect on a patient with chest pain. The potential effect includes both diagnostic and therapeutic issues, including the diagnosis of acute myocardial infarction and the indication for thrombolysis or invasive procedures. We report the case of a man who suffered from a syncope, with a prehospital electrocardiogram showing prominent ST-segment elevation. Out-of-hospital thrombolytic therapy was planned by the emergency department. Fortunately, thrombolysis did not start because the patient fared worse. He was taken to the emergency department and, because of mental status impairment, it was decided to perform a cranial computed tomographic scan. The diagnosis shifted to a haemorrhagic stroke. According to the guidelines, prehospital thrombolysis would have been inappropriate in this case because the patient did not have any chest discomfort. The pathophysiological mechanisms of electrocardiographic abnormalities in the setting of intracranial haemorrhage are reviewed, as well as the issue of thrombolysis administered or planned only on the basis of an electrocardiogram.

Implications of the failure to identify high-risk electrocardiogram findings for the quality of care of patients with acute myocardial infarction: results of the Emergency Department Quality in Myocardial Infarction (EDQMI) study

BACKGROUND

The impact of misinterpretation of the ECG in patients with acute myocardial infarction (AMI) in the emergency department (ED) setting is not well known. Our goal was to assess the prevalence of the failure to identify high-risk ECG findings in ED patients with AMI and to determine whether this failure is associated with lower-quality care.

METHODS AND RESULTS

In a retrospective cohort study of consecutive patients presenting to 5 EDs in California and Colorado from July 1, 2000, through June 30, 2002, with confirmed AMI (n=1684), we determined the frequency of the failure by the treating provider to identify significant ST-segment depressions, ST-segment elevations, or T-wave inversions on the presenting ECG. In multivariable models, we assessed the relationship between missed high-risk ECG findings and evidence-based therapy in the ED after adjustment for patient characteristics and site of care. High-risk ECG findings were not documented in 201 patients (12%). The failure to identify high-risk findings was independently associated with a higher odds of not receiving treatment among ideal candidates for aspirin (odds ratio [OR], 2.13; 95% confidence interval [CI], 1.51 to 2.94), beta-blockers (OR, 1.85; 95% CI, 1.14 to 3.03), and reperfusion therapy (OR, 7.69; 95% CI, 3.57 to 16.67). Among patients with missed high-risk ECG findings, in-hospital mortality was 7.9% compared with 4.9% among those without missed findings (P=0.1).

CONCLUSIONS

The failure to identify high-risk ECG findings in patients with AMI results in lower-quality care in the ED. Systematic processes to improve ECG interpretation may have important implications for patient treatment and outcomes.

Electrocardiogram differentiation of benign early repolarization versus acute myocardial infarction by emergency physicians and cardiologists

OBJECTIVES

ST-segment elevation (STE) related to benign early repolarization (BER), a common normal variant, can be difficult to distinguish from acute myocardial infarction (AMI). The authors compared the electrocardiogram (ECG) interpretations of these two entities by emergency physicians (EPs) and cardiologists.

METHODS

Twenty-five cases (13 BER, 12 AMI) of patients presenting to the emergency department with chest pain were identified. Criteria for BER required four of the following: 1) widespread STE (precordial greater than limb leads), 2) J-point elevation, 3) concavity of initial up-sloping portion of ST segment, 4) notching or irregular contour of J point, and 5) prominent, concordant T waves. Additional BER criteria were 1) stable ECG pattern, 2) negative cardiac injury markers, and 3) normal cardiac stress test or angiography. AMI criteria were 1) regional STE, 2) positive cardiac injury markers, and 3) identification of culprit coronary artery by angiography in less than eight hours of presentation. The 25 ECGs were distributed to 12 EPs and 12 cardiologists (four in academic medicine, four in community practice, and four in community academics [health maintenance organization] in each physician group). The physicians were informed of the patients' age, gender, and race, and they then interpreted the ECGs as BER or AMI. Undercalls (AMI misdiagnosed as BER) and overcalls (BER misdiagnosed as AMI) were calculated for each physician group.

RESULTS

Cardiologists correctly interpreted 90% of ECGs, and EPs correctly interpreted 81% of ECGs. The proportion of undercalls (missed AMI/total AMI) was 2.8% for cardiologists (95% confidence interval [CI] = 0.09% to 5.5%) compared with 9.7% for EPs (95% CI = 4.8% to 14.6%) (p = 0.02). The proportion of overcalls (missed BER/total BER) was 17.3% for cardiologists (95% CI = 11.4% to 23.3%) versus 27.6% for EPs (95% CI = 20.6% to 34.6%) (p = 0.03). The mean number of years in practice was 19.8 for cardiologists (95% CI = 19 to 20.5) and 11 years for EPs (95% CI = 10.5 to 12.0) (p < 0.001).

CONCLUSIONS

Although correct interpretation was high in both groups, cardiologists, who had significantly more years of practice, had fewer misinterpretations than EPs in distinguishing BER from AMI electrocardiographically.

Upwardly concave ST segment morphology is common in acute left anterior descending coronary occlusion

ST elevation (STE) in anterior precordial leads, in association with upwardly convex morphology (M) or straightM, is associated with anterior acute myocardial infarction (aAMI). Upwardly concaveM is characteristic of pseudoinfarction patterns such as early repolarization. A retrospective review was done of diagnostic electrocardiograms (EKG) of consecutive patients presenting to our Emergency Department (ED) who underwent emergent primary percutaneous intervention (PCI) and had proven left anterior descending (LAD) occlusion. If all leads from V2-V6 were upwardly concave, the EKG was classified as concaveM. If one lead was convex, the EKG had convexM. If no leads were convex and at least one was straight, it had straightM. Non-concaveM was defined as either convexM or straightM. Borderline STE was defined if the EKG did not have 2 consecutive leads with >or= 2 mm of STE. "Subtle," as opposed to "diagnostic," morphology was defined as concaveM without terminal QRS distortion. Data were analyzed with descriptive statistics. There were 37 patients identified who met the inclusion criteria and whose records were available for review. ConcaveM was found in 16 of 37 (43%), 4 with terminal QRS distortion. Measurements resulted in a classification of borderline STE in 15 of 37 (41%) (9 of whom had subtle morphology) for Rater 1 and 12 of 37 (32%) (7 of whom had subtle morphology) for Rater 2, while 19% to 24% had both "subtle" morphology and borderline ST elevation. ConcaveM, as compared with convexM or terminal QRS distortion, was associated with a shorter duration of symptoms (p < 0.05). It is concluded that concave morphology cannot be used to exclude STEMI with LAD occlusion. Many patients with LAD occlusion have borderline ST elevation with subtle morphology. Concave morphology is associated with a shorter duration of symptoms.

Acute coronary syndromes

Despite technologic advances in many diagnostic fields, the 12-lead ECG remains the basis for early identification and management of an acute coronary syndrome. This article reviews the use of the ECG in acute coronary syndromes.

ECG Patterns Confounding the ECG Diagnosis of Acute Coronary Syndrome: Left Bundle Branch Block, Right Ventricular Paced Rhythms, and Left Ventricular Hypertrophy

The ECG has limitations in the evaluation of the chest-pain patient, including the presence of confounding ECG patterns; the ECG patterns that confound the diagnosis of acute myocardial infarction(AMI) include left bundle branch block (LBBB), ventricular paced rhythms (VPR), and left ventricular hypertrophy (LVH). These patterns produce new ST-segment/T-wave abnormalities, which are the new normal findings in these patients and may lead the clinician astray in two distinct instances: (1) diagnosing ECG change related to acute coronary syndromes (ACS) when the abnormality results solely from the confounding pattern; and (2) not acknowledging the confounding nature of these ECG patterns in the evaluation of potential ACS, thereby placing excessive diagnostic confidence in the ECG. This article highlights the diagnostic dilemma encountered in these confounding ECG patterns; the discussion focuses on the expected ECG abnormalities in these patients and the findings seen in ACS.

Disagreement in the interpretation of electrocardiographic ST segment elevation: a source of error for emergency physicians?

Evaluation of the electrocardiogram (ECG) is a complex, subjective process with the potential for interobserver disagreement. The objective of this study was to determine the ECG patterns with discrepant interpretations, the rates of disagreement in the determination of both the presence of ST segment elevation (STE) and morphology. ECGs were reviewed in a retrospective fashion by attending EPs for STE and waveform morphology. Those ECGs that were interpreted in a discrepant fashion were then analyzed to detect patterns of disagreement. ECGs from 599 patients were reviewed. Two hundred eleven patients (35.2% of the total patient population surveyed) had STE as determined by at least one attending EP; 40 (19% of the STE population) patients had STE determined by 1 EP, 21 (10% of the STE population) patients by 2 EPs, and 150 (71% of the STE population) patients by 3 EPs. The STE of 61 (28.9%) ECGs were interpreted in a discrepant fashion. The average STE was 1.31 mm per lead for ECGs with disagreement and 2.93 mm per lead for ECGs with agreement (P<.05). ECGs with reciprocal ST depression were more likely to have agreement with regard to the STE (P<.05). Fourteen ECGs (8.2% of 171 ECGs with STE determined by at least 2 EPs) had ST segment morphology interpreted in a discrepant fashion. Disagreement in the determination of electrocardiographic ST segment elevation by EPs occurs frequently and is related to the amount of STE present on the ECG. Electrocardiographic patterns responsible for this interpretive disagreement of ST segment elevation can represent an unfortunate but potentially predictable source of error in emergency medical care.

Non-invasive estimation of myocardial infarction by means of a heart-model-based imaging approach: A simulation study

In the study, a new myocardial infarction (MI) estimation method was developed for estimating MI in the three-dimensional myocardium by means of a heart-model-based inverse approach. The site and size of MI are estimated from body surface electrocardiograms by minimising multiple objective functions of the measured body surface potential maps (BSPMs) and the heart-model-generated BSPMs. Computer simulations were conducted to evaluate the performance of the developed method, using a single-site MI and dual-site MI protocols. The simulation results show that, for the single-site MI, the averaged spatial distance (SD) between the weighting centres of the 'true' and estimated MIs, and the averaged relative error (RE) between the numbers of the 'true' and estimated infarcted units are 3.0 +/- 0.6/3.6 +/- 0.6 mm and 0.11 +/- 0.02/0.14 +/- 0.02, respectively, when 5 microV/10 microV Gaussian white noise was added to the body surface potentials. For the dual-site MI, the averaged SD between the weighting centres of the 'true' and estimated MIs, and the averaged RE between the numbers of the 'true' and estimated infarcted units are 3.8 +/- 0.7/3.9 +/- 0.7mm and 0.12 +/- 0.02/0.14 +/- 0.03, respectively, when 5 microV/10 microV Gaussian white noise was added to the body surface potentials. The simulation results suggest the feasibility of applying the heart-model-based imaging approach to the estimation of myocardial infarction from body surface potentials.

Cognitive forcing strategies in clinical decisionmaking

Cognitive errors underlie most diagnostic errors that are made in the course of clinical decisionmaking in the emergency department. These errors are universal and are prevalent in the special milieu of the ED. Their properties appear to be distinct from those associated with the performance of procedures. They are often costly, but, importantly for both the patient and the physician, they are also highly preventable. Recent developments in education theory provide a means for minimizing and avoiding diagnostic error. Through the process of metacognition, clinicians can develop cognitive forcing strategies to abort such latent errors. Three levels of cognitive forcing strategies are described: universal, generic, and specific. Specific cognitive forcing strategies provide a formal cognitive debiasing approach to deal with what have previously been described as pitfalls in clinical reasoning. This metacognitive approach can be taught to practicing clinicians and to those in training to inoculate them against making diagnostic errors. The adoption of this method provides a systematic approach to cognitive root-cause analysis in the avoidance of adverse outcomes associated with delayed or missed diagnoses and with the clinical management of specific cases.

Variation in patient management based on ECG interpretation by emergency medicine and internal medicine residents

This study was performed to determine the impact of electrocardiogram (ECG) interpretation on urgent patient care decisions by internal medicine (IM) and emergency medicine (EM) resident physicians. Six clinical scenarios and ECGs were given to 31 IM residents and 31 EM residents at a university medical center. Based on the ECG interpretation, the residents were asked to select the best patient management from a list of choices. IM and EM residents were equally likely to choose the correct management for complete heart block (90% IM v 97% EM, P = NS), and pulseless ventricular tachycardia (VT) (94% IM v 97% EM, P = NS). IM residents were less likely to choose the correct management for acute posterior wall myocardial infarction (MI) (26% IM v 74% EM, P <.0001) and unstable supraventricular tachycardia (SVT) (87% IM v 100% EM, P <.05). Residents in both programs were equally likely to misinterpret left ventricular hypertrophy (LVH) (23% IM and 16% EM, P = NS) and benign early repolarization (BER) (48% IM and 52% EM, P = NS) as acute myocardial ischemia when presented with a clinical history not suggestive of cardiac ischemia. IM and EM residents were equally likely to choose the correct management for complete heart block and pulseless VT. Compared with EM residents, IM residents were less likely to choose the correct management of posterior wall MI and unstable SVT. Both IM and EM residents were prone to misinterpreting LVH and BER as acute myocardial ischemia. Resident education in both specialties should focus on ECG interpretation skills to improve patient management decisions.

Electrocardiographic T-wave inversion: differential diagnosis in the chest pain patient

Inverted T waves produced by myocardial ischemia are classically narrow and symmetric. T-wave inversion (TWI) associated with an acute coronary syndrome (ACS) is morphologically characterized by an isoelectric ST segment that is usually bowed upward (ie, concave) and followed by a sharp symmetric downstroke. The terms coronary T wave and coved T wave have been used to describe these ischemic TWIs. Prominent, deeply inverted, and widely splayed T waves are more characteristic of non-ACS conditions such as juvenile T-wave patterns, left ventricular hypertrophy, acute myocarditis, Wolff-Parkinson-White syndrome, acute pulmonary embolism, cerebrovascular accident, bundle branch block, and later stages of pericarditis.

Ethnic differences in the ST segment of the electrocardiogram: a comparative study among six ethnic groups

Deviation of the ST segment of the electrocardiogram (ECG) may signify infarction or ischemia. Prior studies suggest that normal ECG patterns may differ among ethnic groups. We retrospectively reviewed the first thousand medical files of a multiethnic community, where all individuals shared similar living conditions. Only healthy adults, aged 15 to 60 years, were included. Along with age, the most common causes for exclusion were diabetes, hypertension, and ischemic heart disease. A total of 597 subjects (349 men) were included: 350 Saudi Arabians, 39 Filipinos, 95 Indians, 17 Sri-Lankans, and 57 Caucasians. Twenty men and one woman had an ECG pattern of early repolarization (ST segment elevation with upward concavity, notching on QRS, and large symmetrical T wave), with no difference in incidence among ethnic groups. ST segment elevation (2 mm in any of the leads V1-V4, or 1 mm in any of the other leads) without criteria of early repolarization occurred in 11.58%, 13.46%, 3.57%, 4.35%, 11.76%, 7.32% of Saudi, Indian, Jordanian, Filipino, Sri-Lankan, and Caucasian men, respectively (P =.61). Only one Jordanian and 2 Indian women had this pattern. However, Filipino men had higher median ST segment levels than others in leads V1 and V3. Among women, the median ST segment level was iso-electric in all leads in all ethnic groups. Only 3 subjects had ST segment depression >1 mm. Significant ST segment elevation is common in normal healthy men but may not fulfill criteria for early repolarization; it has no ethnic predilection. ST segment elevation is uncommon in normal women. ST segment depression is a rare finding in healthy adults regardless of ethnic origin.

Value of the ECG in suspected acute myocardial infarction with left bundle branch block

Uncomplicated left bundle branch block (LBBB) is characterized by true ST-segment shifts resulting from delayed repolarization in the left ventricle with respect to the right ventricle. When acute coronary occlusions develop in the setting of previous or new LBBB, 12-lead eCG manifestations of injury may also appear. They consist of a more pronounced ST-segment elevation, of ST-segment deviations opposite to those of uncomplicated LBBB, or both. We have reported that the only 3 independent ECG signs of acute MI during LBBB among patients with chest pain or history of coronary disease are: ST elevation > or = 1 mm in leads with a positive QRS, ST-depression > or = 1 mm in V1 to V3, and ST elevation > or = 5 mm in leads with a negative QRS. In our study, the clinical prediction rule score values of these signs were 5; 3; and 2, respectively. A score > or = 3 made a diagnosis of MI with a 90% specificity and a score of 2 with > 80%, specificity. Recent validation studies have confirmed that the presence of any of these ECG signs is associated with a sensitivity of 44 to 79% and a specificity of 93 to 100%. Sensitivity increases if serial or previous ECGs are available for comparison. Interobserver agreement is very high. While current practice guidelines recommend thrombolysis for all patients with chest pain and LBBB, concern among physicians about hemorrhagic stroke prevents many of these patients from receiving timely treatment. In a population with LBBB and chest pain where our proposed ECG criteria were not ascertained, only 73% of eligible patients received thrombolysis; on the other hand, 48% of patients with no biochemical evidence of MI were thrombolyzed. For the latter group, the clinical prediction rule had a score of 0. Instead, 79% of patients with confirmed acute MI had a prediction rule score > or =2. Similar values applied to a subgroup of patients with serial ECGs. We propose that thrombolysis among patients with chest pain and LBBB be decided on the basis of a systematic ECG review to "rule patients in". This provision may result in both a significant reduction in the number of patients without infarction who receive thrombolysis and in timely treatment of those who do have MI.

Comparison of an automated thrombolytic predictive instrument to both diagnostic software and an expert cardiologist for diagnosis of an ST elevation acute myocardial infarction

Because the electrocardiograms (ECGs) of patients with symptoms suggesting an acute thrombotic coronary occlusion are typically read by physicians relatively inexperienced in this skill, it is important to develop automated decision support. A Thrombolytic Predictive Instrument (TPI) is now available along with the standard diagnostic software in a commercially available electrocardiograph. This study evaluates the performance of the predictive software in comparison to both an expert cardiologist and standard diagnostic software. True sensitivity and specificity cannot be determined because acute coronary angiography was not performed. The specificities determined by this study were excellent (98% and 99%), and the sensitivities were very good (72% and 78%). These results that the TPI will be only rarely applied to patients who do not indeed have an acute coronary thrombosis. However, the reasons for even this small number of presumably falsely TPI positive patients should be determined and analyzed. It is unlikely that alterations of the thresholds for TPI activation will significantly improve on this very good level of sensitivity, without prohibitively decreasing specificity.

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.

Electrocardiographic diagnosis of acute myocardial infarction: Current concepts for the clinician

BACKGROUND

Over the past 2 decades, the 12-lead electrocardiogram has attained special significance for the diagnosis and triage of patients with chest pain because timely detection of myocardial injury and a rapid assessment of myocardium at risk proved pivotal to implementing effective reperfusion therapies during acute myocardial infarction. However, this wealth of information could still be underutilized by clinicians who may restrict their diagnostic quest in patients with chest pain to the more classic electrocardiographic signs.

METHODS

The medical literature on electrocardiographic manifestations of acute myocardial infarction was extensively reviewed.

RESULTS

The widespread utilization of both coronary angiography and methods to determine myocardial function and metabolism in patients with acute myocardial infarction over the last 10 years has provided the means for rigorous comparisons with electrocardiographic information. We summarize these electrocardiographic signs and patterns in terms of their relevance to the clinician to help reduce the incidence of "nondiagnostic electrocardiograms" and improve timely decision-making.

CONCLUSIONS

The electrocardiogram continues to be an invaluable tool in the initial evaluation of patients with chest pain. The plethora of data currently available on electrocardiographic changes correlating with myocardial injury allows clinicians to make faster and better decisions than ever before.

Electrocardiographic ST-segment elevation: correct identification of acute myocardial infarction (AMI) and non-AMI syndromes by emergency physicians

OBJECTIVE

To determine the emergency physician's (EP's) ability to identify the cause of ST-segment elevation (STE) in a hypothetical chest pain patient.

METHODS

Eleven electrocardiograms (ECGs) with STE were given to EPs; the patient in each instance was a 45-year-old male with a medical history of hypertension and diabetes mellitus with the chief complaint of chest pain. The EP was asked to determine the cause of the STE and, if due to acute myocardial infarction (AMI), to decide whether thrombolytic therapy (TT) would be administered (the patient had no contraindication to such treatment). Rates of TT administration were determined; appropriate TT administration was defined as that occurring in an AMI patient, while inappropriate TT administration was defined as that in the non-AMI patient.

RESULTS

Four hundred fifty-eight EPs completed the questionnaire; levels of medical experience included the following: postgraduate year 2-3, 193 (42%); and attending, 265 (58%). The overall rate of correct interpretation of the study ECGs was 94.9% (4,782 correct interpretations out of 5,038 instances). Acute myocardial infarction with typical STE, ventricular paced rhythm, and right bundle branch block were never misinterpreted. The remaining conditions were misinterpreted with rates ranging between 9% (left bundle branch block, LBBB) and 72% (left ventricular aneurysm, LVA). The overall rate of appropriate thrombolytic agent administration was 83% (1,525 correct administrations out of 1,832 indicated administrations). The leading diagnosis for which thrombolytic agent was given inappropriately was LVA (28%), followed by benign early repolarization (23%), pericarditis (21%), and LBBB without electrocardiographic AMI (5%). Thrombolytic agent was appropriately given in all cases of AMI except when associated with atypical STE, where it was inappropriately withheld 67% of the time.

CONCLUSIONS

In this survey, EPs were asked whether they would give TT based on limited information (ECG). Certain syndromes with STE were frequently misdiagnosed. Emergency physician electrocardiographic education must focus on the proper identification of these syndromes so that TT may be appropriately utilized.

Stress testing for risk stratification of patients with low to moderate probability of acute cardiac ischemia

In summary, this article focused on the use of stress testing to risk-stratify patients at the conclusion of their emergency evaluation for ACI. As discussed, those patients in the probably not ACI category require additional risk stratification prior to discharge. It should be kept in mind that patients in this category are heterogeneous, containing subgroups at both higher and lower risk of ACI and cardiac events. The patients with lower pretest probability for ACI may only need exercise testing in the ED. Patients with higher pretest probability should undergo myocardial perfusion or echocardiographic stress testing to maximize diagnostic and prognostic information. Prognostic information is the key to provocative testing in the ED. Prognostic information is the component that will help emergency physicians identify the patients who may be discharged home safely without having to worry about a 6% annual cardiac death rate and a 10% overall death rate over the next 30 months. Stress testing provides this key prognostic data, and it can be obtained in short-stay chest pain observation units in a safe, timely, and cost-effective fashion.

Errors in emergency physician interpretation of ST-segment elevation in emergency department chest pain patients

OBJECTIVE

To determine the rate of error in emergency physician (EP) interpretation of the cause of electrocardiographic (ECG) ST-segment elevation (STE) in adult chest pain patients.

METHODS

The authors conducted a retrospective ECG review of adult chest pain patients in a university hospital emergency department (ED) over a three-month period (January 1 to March 31, 1996). ST-segment elevation was determined to be present 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. Initial EP ECG interpretation was compared with the final interpretation by a cardiologist supported by the results of various clinical investigations. The rate of incorrect ECG diagnosis was calculated.

RESULTS

Two hundred two patients had STEs. The rate of ECG STE misinterpretation was 12 of 202 (5.9%). The most frequently misdiagnosed form of STE was left ventricular aneurysm, for which two of five cases were believed to represent acute myocardial infarction (AMI). The benign early repolarization (BER) pattern was the second most frequently misinterpreted STE entity-in a total of three cases, two were initially noted to represent pericarditis and one AMI. ST-segment elevation resulting from actual AMI was initially incorrectly noted to be noninfarction in etiology in two cases, one patient with BER and the other with left ventricular hypertrophy.

CONCLUSIONS

Emergency physicians show a low rate of ECG misinterpretation in the patient with chest pain and STE. The clinical consequences of this misinterpretation are minimal.

Strict reliance on a computer algorithm or measurable ST segment criteria may lead to errors in thrombolytic therapy eligibility

BACKGROUND

There is accumulating evidence that thrombolytic therapy is underused among eligible patients with acute myocardial infarction. We sought to determine whether potential errors in electrocardiographic diagnosis might be a contributing factor.

METHODS

Seventy-five electrocardiograms were interpreted on 2 separate occasions by 3 cardiologists. Two criteria were compared for thrombolysis eligibility: (1) measurement of > or =1 mm ST-segment elevation in 2 contiguous leads (measured) and (2) criterion 1 plus the subjective opinion that the changes represented acute transmural injury (interpretive). The results were compared with computerized interpretations by the Marquette 12SL system.

RESULTS

Raw agreement and agreement corrected for chance between raters for both criteria were excellent and tended to be better for interpretive compared with measured criteria (kappa = 0.89 vs 0.78, respectively). Strict reliance on measured electrocardiographic criteria alone would have resulted in overuse of thrombolysis among all 3 raters. Based on the consensus opinion, the absolute overuse of thrombolysis would have been approximately 15% (P <.0034). The computer algorithm had a specificity of 100% and a sensitivity of 61.5%. Reliance on the computerized interpretation alone would have lead to underuse of thrombolytic therapy compared with consensus opinion (21.3% vs 34. 6%; P <.005).

CONCLUSION

Agreement for suspected acute myocardial infarction tended to be better when the appearance of the ST segments was added to measurable ST elevation criteria. Strict reliance on measurable criteria may lead to the inappropriate overuse of thrombolysis. Although the Marquette 12SL system has excellent specificity, it has poor sensitivity for the diagnosis of thrombolysis-eligible AMI. Reliance on computerized electrocardiographic interpretation would lead to the inappropriate underuse of thrombolytic therapy in situations in which qualifying electrocardiographic criteria are actually met.

Clinical Utility of Electrocardiographic ST-Segment Area for Predicting Unsatisfactory Outcomes Following Thrombolytic Therapy

The bedside surface 12-lead electrocardiogram is a mainstay in the early diagnostic evaluation of patients with suspected acute myocardial infarction. The presence of ST-segment elevation exceeding 1.0 mm in two or more anatomically associated leads is a reliable marker of myocardial injury and, when considered along with concomitant ST-segment depression, reflects the extent of myocardial injury. Mounting evidence also suggests that prolonged repolarization is a marker of injury and predicts the likelihood of malignant ventricular arrhythmias. We questioned whether a measure of both ST-segment duration and deviation (ST-deviation area) would offer additional prognostic information. Methods/Results: Admission electrocardiograms from 200 consecutive patients with ischemic chest pain accompanied by ST-segment elevation in whom thrombolytic therapy was given within 6 hours from symptom onset were analyzed. The sum of ST-segment elevation (Sigma ST elevation) and ST-segment deviation (Sigma ST deviation) were calculated, as was the sum of ST-segment deviation area (Sigma ST deviation area). All ST measurements were performed 60 msec after the J point. Computerized planimetry was used to calculate ST-segment area. Sigma ST deviation and Sigma ST deviation area remained constant over time. Patients with large deviations (Sigma ST elevation > 20 mm (odds ratio 2.14, p = 0.02) and Sigma ST deviation area > 150 (odds ratio 1.92, p = 0.02) had a higher incidence of in-hospital unsatisfactory clinical outcome (defined as death, congestive heart failure, cardiogenic shock, recurrent myocardial infarction, or the need for coronary revascularization). These relationships were present for both inferior and anterior infarctions. Sigma ST deviation area correlated closely with Sigma ST elevation (r = 0.92; p = 0.0001) and significantly but much less strongly with the sum of Q waves (r = 0.18; p = 0.01). By univariate analysis, only site of infarction (p = 0.01), Sigma ST deviation area (p = 0.04), and the sum of Q waves (p = 0.005) were identified as predictors of a poor clinical outcome. The sum of Q waves was identified by multivariate analysis as the best independent predictor of an unsatisfactory clinical outcome. Conclusions: A clinician's ability to provide optimal care is influenced strongly by the availability of diagnostic and prognostic information. In the evaluation of patients with acute myocardial infarction, ST-segment deviation area derived from the admission surface electrocardiogram can be used to risk-stratify patients. The full clinical potential of this measure is unknown and will require further evaluation.

Electrocardiographic manifestations: patterns that confound the EKG diagnosis of acute myocardial infarction-left bundle branch block, ventricular paced rhythm, and left ventricular hypertrophy

The 12-lead electrocardiogram (EKG), a powerful tool used in evaluating the chest pain patient, has its shortcomings. One such failing is encountered in a patient with one of the following electrocardiographic patterns: left bundle branch block (LBBB), ventricular paced rhythm (VPR), and left ventricular hypertrophy (LVH). These patterns reduce the ability of the EKG to detect acute coronary ischemic change and acute myocardial infarction (AMI). Several strategies are available to assist in the correct interpretation of these complicated electrocardiographic patterns, including a knowledge of the ST segment-T wave changes associated with these confounding patterns, performance of serial EKGs, and comparison with previous EKGs if available. This article suggests guidelines and interpretive tools for diagnosing AMI on EKG in patients with these confounding patterns.

[The clinical management guidelines of the Sociedad Española de Cardiología in acute myocardial infarct]

In the recent years, new possibilities have emerged in the diagnosis and management of acute myocardial infarction with ST segment elevation and its complications. Moreover, a deep transformation has taken place in the health care system organization, particularly in aspects related to care of patients presenting non-traumatic chest pain, both in pre-hospital and hospital areas. All these issues warrant a consensus document in Spain dealing with the role that these important changes should play in the whole management of myocardial infarction patients. This document revises and updates all the main clinical issues of acute myocardial infarction patients from the moment they contact with the health care system outside the hospital until they return home, after staying at the coronary care unit and the general hospitalization ward. All those aspects are considered not only in the uncomplicated myocardial infarction but also in the complicated one. This review also includes a set of recommendations on structural and organisational aspects, mainly referred to the prehospital and emergency levels.

Electrocardiographic manifestations: benign early repolarization

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 (STE). The electrocardiogram (EKG) findings of BER include 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 the electrocardiographic findings useful in making the diagnosis as well as distinguishing BER from other STE syndromes.

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.

Factors associated with delay in giving thrombolytic therapy after arrival at hospital

OBJECTIVE

To identify factors associated with delay in administration of thrombolytic therapy for acute myocardial infarction.

DESIGN

Retrospective case note review of a six-month period in 1995. Data were obtained on age, sex, hospital arrival time, triage priority, assessment process in the emergency department, grade of emergency doctor, patient history, timing of and findings on electrocardiogram (ECG), type of infarct, timing and site of administration of thrombolytic therapy, and type of thrombolysis given.

SETTING

Tertiary referral hospital in Newcastle, New South Wales.

PARTICIPANTS

Eighty-five patients given thrombolytic therapy for acute myocardial infarction.

OUTCOME MEASURE

Time between hospital arrival and initiation of thrombolytic therapy.

RESULTS

The median time from hospital arrival to administration of thrombolytic therapy was 80 minutes (interquartile range [IR], 50-133). Only 26% of patients were triaged to Priority 1 or 2 (to be seen by a doctor within 10 minutes). Patients initially assessed by a specialist emergency physician received thrombolytic therapy a median of 38 (IR, 33-50) minutes after hospital arrival, compared with 65 (IR, 50-107) minutes if initially assessed by a medical registrar, and 148 (IR, 89-185) and 160 (IR, 95-163) minutes, respectively, if initially assessed by an intern or a resident medical officer (P < 0.001). Factors associated with increased delay in receiving thrombolytic therapy (after adjustment for possible confounders) were low triage priority, initial assessment by a junior doctor, atypical presenting history of myocardial infarction, and lesser degrees of ST-segment elevation on the presenting ECG (all P < or = 0.01).

CONCLUSIONS

Delay in administration of thrombolytic therapy in hospital results from a combination of hospital and patient factors. Changes in emergency department protocol may reduce these delays in some patients.

Determining appropriateness of coronary thrombolysis in the emergency department

STUDY OBJECTIVE

To estimate the appropriateness of decision-making by emergency physicians regarding coronary thrombolysis.

METHODS

We conducted a retrospective chart review of patients admitted over a period of 13 months from a tertiary care center emergency department with a diagnosis of an acute ischemic coronary syndrome. Both thrombolysed and nonthrombolysed patients were eligible for inclusion. The decisions of emergency physicians to use or not use thrombolytics were compared with standard Canadian guidelines, based on the blinded assessments of two reviewers. Appropriateness was estimated with the use of adjusted kappa statistics, and a hierarchical statistical model was developed to estimate the distribution of appropriate decision-making rates for individual emergency physicians.

RESULTS

The overall adjusted kappa for appropriateness was .85 (95% confidence interval [CI], .76 to .94). The appropriateness rate for thrombolysed patients was 80.6% (95% CI, 62.5 to 92.5), and for nonthrombolysed patients it was 97.2% (95% CI, 91.9 to 99.4). The distribution of individual emergency physician appropriateness rates had an estimated mean of 91.3% and a 95% CI of 81.3% to 97.7%. Complication rates were not significantly different from previously published rates.

CONCLUSION

This study demonstrates excellent agreement between emergency physicians' decisions regarding thrombolysis and standard Canadian guidelines, based on an adjusted kappa statistic. The distribution of individual emergency physician appropriateness rates and the appropriateness rate for nonthrombolysed patients are estimated for the first time.

How much do we gain by reducing time to reperfusion therapy?

Emphasis continues to be placed on the need to minimize the time elapsed between the onset of symptoms of myocardial infarction and the initiation of thrombolytic therapy. Numerous large-scale trials have revealed an inverse relation between time-to-treatment and the degree of reduction in the risk of adverse clinical outcomes. Still to be resolved is the question of whether additional benefit can be gained by treating within the first hour. Many factors that influence delays to presentation are also associated with a higher risk of mortality, and these factors vary with patient characteristics. These same factors are also associated with longer treatment delay and greater mortality risk. Although the greatest opportunity for reducing time-to-treatment lies in reducing presentation time, public education efforts have been largely unsuccessful. Despite the fact that treatment delay generally accounts for a smaller proportion of total delay time than does presentation delay, it may be more amenable to shortening through measures such as transmission of electrocardiograms from the field; emergency department protocols for the rapid triage, assessment, and treatment of patients with chest pain; training emergency department physicians to administer thrombolytic therapy without a cardiology consult; and storing thrombolytic agents in the emergency department.