Usefulness of two-dimensional echocardiography for immediate detection of myocardial ischemia in the emergency room

Inappropriate discharge from the emergency room of patients with acute chest pain may have serious consequences. Regional asynergy is one of the first signs of myocardial ischemia and can be detected with 2-dimensional echocardiography (2-DE). This study determines the value of 2-DE in the emergency room for immediate detection of myocardial ischemia causing acute chest pain at the time the electrocardiogram was nondiagnostic. Forty-three patients (32 men and 11 women) with a normal or nondiagnostic electrocardiogram during acute chest pain were studied with 2-DE. Only patients without a previous myocardial infarction and without known coronary artery disease (CAD) were studied. The entire left ventricular wall was examined for presence of regional asynergy. Coronary angiography was performed within 3 weeks. Cardiac enzyme levels were measured serially to establish or rule out an acute myocardial infarction. Sensitivity of 2-DE for detection of myocardial ischemia was 88% (22 of 25), specificity 78% (14 of 18), negative predictive accuracy 82% (14 of 17) and positive predictive accuracy 85% (22 of 26). Sensitivity of 2-DE for detection of acute myocardial infarction was 92% (12 of 13), specificity 53% (16 of 30) and negative predictive accuracy 94% (16 of 17). Thus, 2-DE during pain and a nondiagnostic electrocardiogram can readily identify patients with CAD in the emergency room, and it can accurately rule out an acute myocardial infarction.     

Eligibility for intravenous thrombolysis in suspected acute myocardial infarction

Based on the registration of all the 7,157 patients admitted during a 21-month period to the emergency ward of a single hospital in an urban area with chest pain or other symptoms suggestive of acute myocardial infarction, we studied eligibility for intravenous thrombolysis in suspected acute myocardial infarction. We have limited the present analysis to those 1,715 patients with a strong suspicion of myocardial infarction, and for these patients, we have calculated the percentages eligible for thrombolysis when various electrocardiographic and delay time criteria are applied, but we have not considered contraindications to thrombolysis. We have also calculated the proportions of all infarctions in this group that would thereby receive the treatment, and the proportions of patients treated that would develop a confirmed infarction. Using the criteria ST elevation on the initial electrocardiogram and arrival in hospital within 6 hours from onset of symptoms, 18% of patients would have been given early intravenous thrombolysis, 37% of confirmed infarctions would have been treated, and 91% of all treated patients would have developed a confirmed infarction; with a delay time criterion of 12 hours, these percentages would have been 20%, 41%, and 91%, respectively; with a criterion of 24 hours, they would have been 22%, 45%, and 90%, respectively. By not considering the initial electrocardiogram and applying only the criterion of delay time, these percentages would have been 70%, 72%, and 45%, respectively, for a delay time of 6 hours; 83%, 84%, and 45%, respectively, for a delay time of 12 hours; and 91%, 92%, and 44%, respectively, for a delay time of 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS)     

Chest pain unit: one-year follow-up

INTRODUCTION AND OBJECTIVES: In Spain there is little information available about chest pain units for the treatment of patients of low-to-medium risk with suspected acute coronary syndrome. PATIENTS AND METHOD: A prospective study was performed among emergency room patients who complained about acute chest pain and were suspected of suffering an acute coronary syndrome with a normal or unspecific initial evaluation. They underwent an early submaximum stress test to decide on possible hospitalization. The follow-up time was 1 year. RESULTS: Of 472 emergency room patients with suspected acute coronary syndrome, 179 performed the stress-test during the first hours of the triggering chest pain episode. None met the high-risk criteria for unstable angina. In 78.8% of the cases, the test results were negative and the patients were discharged. The results were positive in 15.1% and inconclusive in 6.1%; there were no complications during the procedure. Patients with a negative stress test had a more favorable outcome than the rest, with fewer following visits to the emergency room (11% vs 22%, p<0.001). One patient with a negative stress test died of a non-cardiovascular complication. None of the patients suffered acute myocardial infarction during follow-up and 89% of the patients with negative stress test had a favorable outcome (in terms of visits to the emergency room, unstable angina, acute myocardial infarction, or cardiovascular death). CONCLUSIONS: Chest pain units for the care of low-to-medium risk patients with acute chest pain allow a fast and safe hospital release with a favorable mid-term outcome.     

Clinical symptoms and myocardial infarction in left bundle branch block patients

In patients with left bundle branch block (LBBB) and acute chest pain, the association between the clinical presentation and the diagnosis of myocardial infarction has not been investigated. We sought to identify features in the clinical history of patients with LBBB and acute cardiopulmonary symptoms that predict myocardial infarction among candidates for reperfusion therapy. We retrospectively studied a consecutive cohort of 75 patients (94 presentations) who presented to a university emergency department from 1994 to 1997 with LBBB on initial electrocardiogram (ECG) and acute chest pain of >/=20 min duration or acute pulmonary edema. Among the 94 presentations meeting criteria for the cohort, 26 (28%) had confirmed myocardial infarction. Coronary heart disease risk factors, past cardiac history, prior LBBB on the ECG, and presenting symptoms did not predict whether patients were having myocardial infarction. The clinical history was not effective at distinguishing LBBB patients with myocardial infarction among patients who appeared to be candidates for acute reperfusion therapy.     

Patients admitted to the emergency room with symptoms indicative of acute myocardial infarction

All 7157 patients (55% men) admitted to the emergency room with chest pain or other symptoms indicative of acute myocardial infarction during a period of 21 months were registered consecutively. Chest pain was reported by 93% of the patients. On the basis of history, clinical examination, and electrocardiogram in the emergency room, all patients were prospectively classified in one of four categories: (i) obvious infarction (4% of all patients); (ii) strongly suspected infarction (20%); (iii) vague suspicion of infarction (35%); and (iv) no suspected infarction (41%). In patients with no suspected infarction (n = 2910), musculoskeletal (26%), obscure (21%) and psychogenic origins (16%) of the symptoms occurred most frequently. We conclude that few of the patients had an obvious infarction on admission, and that a musculoskeletal origin of the symptoms occurred most frequently in patients with no suspected infarction.     

The diagnostic value of troponin T testing in the community setting

BACKGROUND: Many patients presenting with chest pain to their family physician are referred to the emergency room, in part, due to lack of accurate objective diagnostic tools. This study aimed to assess the diagnostic value of bedside troponin T kit testing in patients presenting with chest pain to their family physician. DESIGN: Prospective, multi-center study. METHODS: Consecutive subjects with chest pain were recruited from 44 community clinics in Jerusalem. Following clinical assessment by the family physician, qualitative troponin kit testing was performed. Patients with a negative clinical assessment and negative troponin kit were sent home and all others were referred to the emergency room. The final diagnosis at the time of hospital discharge was recorded and telephone follow up was performed after 60 days. Positive predictive value, negative predictive value, sensitivity and specificity of troponin kit for myocardial infarction diagnosis and of family physician for hospitalization, were assessed. RESULTS: Of 392 patients enrolled, 349 (89%) were included in the final analysis. The prevalence of myocardial infarction was 1.7%. The positive and negative predictive values of the troponin kit for myocardial infarction diagnosis were 100% and 99.7%, respectively. The positive and negative predictive values of the family physician's assessment to predict hospitalization were 41.4% and 94.1%, respectively. CONCLUSIONS: Troponin kit testing is an important tool to assist the family physician in the assessment of patients with chest pain in the community setting. Troponin kit testing may identify otherwise undiagnosed cases of myocardial infarctions, and reduce unnecessary referrals to the emergency room.     

Ninety-minute accelerated critical pathway for chest pain evaluation

Rapid, efficient, and accurate evaluation of chest pain patients in the emergency department optimizes patient care from public health, economic, and liability perspectives. To evaluate the performance of an accelerated critical pathway for patients with suspected coronary ischemia that utilizes clinical history, electrocardiographic findings, and triple cardiac marker testing (cardiac troponin I [cTnI], myoglobin, and creatine kinase-MB [CK-MB]), we performed an observational study of a chest pain critical pathway in the setting of a large Emergency Department at the Veterans Affairs Medical Center in 1,285 consecutive patients with signs and symptoms of cardiac ischemia. The accelerated critical pathway for chest pain evaluation was analyzed for: (1) accuracy in triaging of patients within 90 minutes of presentation, (2) sensitivity, specificity, positive predictive value, and negative predictive value of cTnI, myoglobin, and CK-MB in diagnosing acute myocardial infarction (MI) within 90 minutes, and (3) impact on Coronary Care Unit (CCU) admissions. All MIs were diagnosed within 90 minutes of presentation (sensitivity 100%, specificity 94%, positive predictive value 47%, negative predictive value 100%). CCU admissions decreased by 40%. Ninety percent of patients with negative cardiac markers and a negative electrocardiogram at 90 minutes were discharged home with 1 patient returning with an MI (0.2%) within the next 30 days. Thus, a simple, inexpensive, yet aggressive critical pathway that utilizes high-risk features from clinical history, electrocardiographic changes, and rapid point-of-care testing of 3 cardiac markers allows for accurate triaging of chest pain patients within 90 minutes of presenting to the emergency department.     

Usefulness of technetium-99m tetrofosmin single-photon emission computed tomography for short-term risk stratification in patients with acute chest pain in the emergency room

OBJECTIVES: High-risk patients with acute coronary syndrome are difficult to distinguish from low-risk patients with chest pain in the emergency room. Technetium-99m (99mTc) tetrofosmin single-photon emission computed tomography (SPECT) was investigated to exclude high-risk patients with chest pain in the emergency room. METHODS: 99mTc-tetrofosmin SPECT was evaluated using a four-point scoring system in 228 patients (144 men, 84 women, mean age 68 +/- 12 years) with chest pain. Negative was defined as the myocardial segments with a defect score (DS) of < 2. The patients were divided into two groups; the negative group with DS < 2 (n = 78) and the positive group with DS > or = 2 (n = 150). Cardiac events (cardiac death, acute myocardial infarction and refractory angina) were evaluated within 30 days of onset. ST-segment elevation or depression > or = 0.1 mV was defined as positive in electrocardiography. The results of SPECT were compared with those of electrocardiography, transthoracic echocardiography and serum cardiac markers (troponin T and creatine kinase-MB) in 95 patients. RESULTS: The negative group had very few cardiac events (three patients with refractory angina) (3.8%). The negative predictive value of cardiac events evaluated by electrocardiography was calculated as 83.1%, whereas the negative predictive value by SPECT was 96.2% (p < 0.01). In addition, the negative predictive value of acute myocardial infarction by SPECT was 100%. The negative predictive values of cardiac events evaluated by SPECT, electrocardiography, transthoracic echocardiography and serum cardiac markers were 95.8%, 81.5% (vs 99mTc-tetrofosmin; NS), 84.9% (NS) and 60.4% (p < 0.05), respectively. CONCLUSIONS: 99mTc-tetrofosmin SPECT is a useful method to exclude high-risk patients among patients with chest pain in the emergency room.     

Laser facilitated angioplasty and thrombolysis in acute myocardial infarction complicated by prolonged or recurrent chest pain

To date, application of laser angioplasty in acute myocardial infarction (MI) has not been reported. In nine patients with acute myocardial infarction complicated by continuous or recurrent severe ischemia and chest pain, a mid-infrared, solid-state, pulse-wave holmium/thulium:YAG coronary laser was applied. In six of these patients the laser was specifically utilized for the purpose of coronary thrombolysis. In each case a guidewire was placed across the stenosis and a multifiber laser catheter was utilized, emitting 250–600 mJ/pulse at 5 Hz, followed by adjunctive balloon angioplasty. Laser success (defined as ability to cross the lesion, reduction of ±20% in stenosis and thrombolysis when a thrombus is present) was achieved in all patients. Final angiograms revealed residual stenosis ±30%, adequate thrombolysis and no major complication (MI, perforation, emergency CABGS, CVA, death) in each patient. Clinically, all nine patients improved, survived the acute infarction and were discharged. This initial clinical experience demonstrates the feasibility and safety of holmium/thulium:YAG laser application in thrombolysis and plaque ablation in selected patients who experience acute myocardial infarction complicated by prolonged or recurrent ischemia and chest pain.     

Usefulness of ST-segment changes in ≥2 leads on the emergency room electrocardiogram in either unstable angina pectoris or non-Q-wave myocardial infarction in predicting outcome

To determine the reliability of the admission electrocardiogram in predicting outcome in patients hospitalized for chest pain at rest, 90 patients were randomized into a trial of aspirin versus heparin in unstable angina or non-Q-wave myocardial infarction, and prospectively followed for 3 months. The emergency room admission electrocardiogram was analyzed for ST-segment deviation ≥1 mm/lead and T-wave changes. Unfavorable outcomes were recurrent ischemic pain, myocardial infarction and coronary revascularization with angioplasty or surgery. In patients who underwent coronary arteriography, a myocardium in jeopardy score ranging from 0 to 10 was assigned, based on the number of vessels with a diameter stenosis ≥70% and the location of the stenoses. Considering all 90 patients, an admission electrocardiogram with ST-segment deviation in ≥2 leads had a positive predictive value for adverse clinical events of 79% and a negative predictive value of 64%. In the subset of patients without left ventricular hypertrophy and whose admission electrocardiograms were recorded during chest pain (62 of 90), the positive predictive value of ST deviation in ≥2 leads improved to 89% and the negative value to 72%. Of the 62 patients, 53 underwent coronary arteriography. There was a positive linear correlation between the total number of leads with ST-segment deviation and the myocardium in jeopardy score (r = 0.80, p < 0.001). In patients with unstable angina or non-Q-wave myocardial infarction, an admission electrocardiogram recorded during pain and revealing ST-segment changes in ≥2 leads is by itself a reliable predictor of major clinical events. The total number of leads with ST changes predicts the extent of myocardium in jeopardy.     

Technetium-99m sestamibi myocardial perfusion imaging in the emergency room evaluation of chest pain

Objectives. The purpose of this investigation was to evaluate the practicality and short-term predictive value of acute myocardial perfusion imaging with technetium-99m sestamibi in emergency room patients with typical angina and a normal or nondiagnostic electrocardiogram (ECG).Background. Accuracy of emergency room chest pain assessment may be improved when clinical and ECG variables are used in conjunction with acute thallium-201 myocardial perfusion imaging. Technetium-99m sestamibi is a new radioisotope that is taken up by the myocardium in proportion to blood flow, but unlike thallium-201, it redistributes minimally after Injection. Technetium-99m sestamibi can thus be injected during chest pain, and images acquired 1 to 2 h later (when patients have been clinically stabilized) will confirm whether abnormalities of perfusion were present at the time of injection.Methods. One hundred two emergency room patients with typical angina (on the basis of a standardized angina questionnaire) and a normal or nondiagnostic ECG had a technetium-99m sestamibi injection during symptoms and were followed up for occurrence of adverse cardiac events (cardiac death, nonfatal myocardial infarction, coronary angioplasty, coronary surgery or coronary thrombolysis).Results. Univariate predictors of cardiac events included the presence of three or more coronary risk factors (p = 0.009, risk ratio 3.3) and an abnormal or equivocal acute technetium-99m sestamibi scan (p = 0.0001, risk ratio 13.9). Multivariate regression analysis identified an abnormal perfusion image as the only independent predictor of adverse cardiac events (p = 0.009). Of 70 patients with a normal perfusion scan, only 1 had a cardiac event compared with 15 patients with equivocal scans or 17 patients with abnormal scans, with a cardiac event rate of 13% and 71%, respectively (p = 0.0004).Conclusions. Initial myocardial perfusion imaging with technetium-99m sestamibi when applied in emergency room patients with typical angina and a normal or nondiagnostic ECG appears to be highly accurate to distinguishing between low and high risk subjects.     

Hospital protocols and policies that may delay early identification and thrombolytic therapy of acute myocardial infarction patients

Despite the compelling relationship between early treatment and outcome from reperfusion therapy in patients with acute myocardial infarction, significant delays in early treatment are imposed by the patient, prehospital systems, and hospital processes and protocols used in the identification and treatment of patients with myocardial infarction. A survey instrument designed to determine the prevalence of hospital policies and protocols that might delay or expedite treatment with thrombolytic therapy in patients with acute myocardial infarction was completed by 524 hospitals participating in the National Registry for Myocardial Infarction (NRMI). Participating hospitals had treated 17,646 patients with tissue plasminogen activator. The door to drug time for the entire population of patients treated at each hospital was available. Door to drug times were compared between those hospitals that had a positive response to a policy and those that had a negative response to that policy. Among respondent hospitals, thrombolysis was excluded by protocol in 34.4% for age above 75 and in 55% for presentation after 6 hours of chest pain onset. Furthermore, 29.4% of hospitals required routine laboratory testing other than electrocardiography (ECG), including chest x-ray, prior to determination of eligibility for thrombolysis. Door to drug times were shorter in those hospitals with prehospital 12-lead ECG availability, assessment of the 12-lead ECG by the emergency department nurse and physician as soon as it was available, and initiation of thrombolysis by the emergency physician (in patients with clear-cut ST elevation myocardial infarction) without bedside cardiology consultation. Door to drug times were longer in those hospitals in which predecision laboratory results were required, written informed consent was mandated, and drug was initiated in the cardiac intensive care unit rather than in the emergency department itself. Door to drug times were not significantly different in those hospitals with a designated chest pain center compared with those operating under a focused patient care protocol. We conclude that the earliest possible hospital treatment of acute myocardial infarction patients may be precluded by multiple components of emergency department policies and process, many of them inappropriate for safe, efficient, and effective identification and management of these patients.This research was presented in part at the Annual Scientific Session, American College of Cardiology, Atlanta, Georgia, March 1994     

Failure of Serial Electrocardiograms to Exclude a Large Anterior Myocardial Infarction and the Role of Transesophageal Echocardiogram in Acute Myocardial Infarction

When patients present with acute onset of chest pain suggestive of myocardial ischemia, immediate clinical decisions regarding thrombolysis, percutaneous transluminal coronary angioplasty, or both are usually based on the history and abnormal electrocardiograms and confirmed by the presence of abnormally elevated cardiac enzymes. However, there are potential limitations of the electrocardiograms and initial cardiac enzymes in the diagnosis and confirmation of acute myocardial infarction. We describe the case of a patient who presented with an acute onset of chest pain and had a normal electrocardiogram and initial cardiac enzymes yet was found by transesophageal echocardiography to have a large myocardial infarction.     

心室激动异常合并急性心肌梗死的心电图特点分析

心电图是公认的诊断急性心肌梗死最简单易行、价格低廉的重要辅助检查之一,是急性ST段抬高心肌梗死快速选择再灌注治疗方案的最重要依据之一。但心室激动异常（完全性左束支传导阻滞、右室起搏心律、预激综合征等）可能掩盖急性心肌梗死图形,导致误诊漏诊,可能延误急性心肌梗死的再灌注时机,严重影响患者预后。尤其是合并左束支传导阻滞的急性心肌梗死患者病死率可能更高,预后更差,但从急诊冠状动脉血运重建术中获益也最大。1996年Sgarbossa首次提出、2005年Reuben和Mann等进行简化的鉴别诊断,心室激动异常合并急性心肌梗死的心电图在原发性ST-T改变的基础上出现＂QRS波群———ST-T不一致＂法则,包括（1）QRS波群主波向上的导联ST段抬高〉0.1 mV;（2）QRS波群主波向下的导联ST段抬高〉0.5 mV（V1～V3导联常见）;（3）V1、V2和V3等S波为主的导联ST段压低〉0.1 mV。除左束支传导阻滞外,右室起搏心律和预激综合征也可掩盖急性心肌梗死图形。上述法则可辅助急诊科、心内科医生较快速地诊断心室激动异常合并急性心肌梗死,从而尽早选择下一步再灌注策略,有重要的临床意义。     

The importance of creatine kinase determination in identifying acute myocardial infarction among patients complaining of chest pain in an emergency room

The contribution of serum creatine kinase (CK) levels to the diagnosis of acute myocardial infarction (AMI) in an emergency room was studied in 252 patients presenting with chest pain. Thirty percent were ultimately diagnosed as having AMI. The electrocardiogram (ECG) identified 66% of patients with AMI who were evaluated within 4 h of onset of symptoms; while CK serum levels were elevated in only 9%. Among patients evaluated more than 4 h after the onset of symptoms, the ECG was helpful in diagnosing AMI in only 36.6%, while serum CK levels were high in 63.4%. CK testing added significantly to the diagnosis of AMI in patients already studied by ECG. We suggest that determination of serum CK levels in the emergency room is of value in the evaluation of patients complaining of chest pain 4 or more hours after the onset of symptoms.     

Efficiency of a physician-operated mobile intensive care unit for prehospital thrombolysis in acute myocardial infarction.

The efficiency of an emergency medical system for routinely performed prehospital thrombolysis is evaluated for 1 of the 7 physician-staffed mobile intensive care units (MICU) in former West Berlin. During 19 consecutive months the MICU had 4,920 missions, and 1,226 patients had chest pain of presumed cardiac origin. The diagnosis at hospital discharge was acute myocardial infarction (AMI) in 406 patients and "interrupted" infarction in 11 patients (total 417). Correct on-scene electrocardiographic diagnosis of acute injury was made in 268 patients (64%) and was false-positive in 4 patients (1%). In 8%, present ST elevations were not recognized. In 27%, the electrocardiogram on scene was nondiagnostic (16% with no ST elevation, 11% with bundle branch block). Of all 417 patients with later hospital evidence of AMI, 317 (76%) were seen by the MICU physician within 4 hours, and 173 (41%) within the first hour from symptom onset. Two hundred three patients seen within 4 hours had diagnostic ST elevation on the scene, of whom 124 (61%) received prehospital thrombolysis (74 patients [36%] within the first hour). There was no prehospital death; hospital mortality was 6.3%. Because greater than 50% of all patients in the community, hospitalized because of AMI, made use of the MICU and 3/4 of them had called within 4 hours from symptom onset, a large proportion of all patients with AMI were candidates for the actually received prehospital thrombolysis.     

Clinical policy: critical issues in the evaluation and management of adult patients presenting with suspected acute myocardial infarction or unstable angina. American College of Emergency Physicians

This clinical policy focuses on critical issues in the evaluation and management of patients with acute myocardial infarction or unstable angina. A MEDLINE search for articles published between January 1993 and December 1998 was performed using combinations of the key words chest pain, acute myocardial infarction, unstable angina, thrombolytics, primary angioplasty, 12-lead ECG, ST-segment monitoring, cardiac serum markers, and chest pain centers. Subcommittee members and expert peer reviewers also supplied articles with direct bearing on the policy. This policy focuses on 5 areas of current interest and/or controversy: (1) ECG eligibility criteria for fibrinolytic therapy, (2) role of primary angioplasty in patients with acute myocardial infarction, (3) use of serum markers to diagnose acute myocardial infarction, (4) serial 12-lead ECGs during the initial evaluation, and (5) chest pain evaluation units. Recommendations for patient management are provided for each of these 5 topics based on strength of evidence (Standards, Guidelines, Options). Standards represent patient management principles that reflect a high degree of clinical certainty; Guidelines represent patient management principles that reflect moderate clinical certainty; and Options represent other patient management strategies based on preliminary, inconclusive, or conflicting evidence, or based on panel consensus. This guideline is intended for physicians working in hospital-based emergency departments or chest pain evaluation units.     

Secondary splenic rupture after thrombolysis for acute myocardial infarction

Secondary splenic rupture after thrombolysis for acute myocardial infarction. HISTORY AND ADMISSION FINDINGS: A 67-year-old male patient was admitted with acute chest pain and signs of an acute anterior myocardial infarction in the ECG. The usual contraindications were excluded and after a systemic lysis with rt-PA the ECG-alterations as well as the symptoms of angina resolved completely. 2 hours later the patient developed an acute abdomen with a severe circulatory shock. INVESTIGATIONS: On ultrasound and CT a massive intraabdominal bleeding was found. TREATMENT AND COURSE: Emergency laparotomy revealed a splenic rupture. Retrospectively, 6 weeks before admission, the patient had fallen from a ladder to his left side. This is a rare case of a secondary splenic rupture during thrombolysis for acute myocardial infarction. 2 weeks later the patient developed rein-farction with angiographically shown two vessel disease. After angioplasty of the ramus interventricularis anterior (RIVA) he was stable. CONCLUSIONS: Intravenous thrombolysis in case of acute myocardial infarction is the method of choice. In the past a great number of patients were excluded from thrombolysis because of an extensive interpretation of contraindications. The aim to reach an alteration in this use may not risk health of patients by insufficient history.     

Accuracy of computer-interpreted electrocardiography in selecting patients for thrombolytic therapy. MITI Project Investigators

A prehospital computer-interpreted electrocardiogram (ECG) was obtained in 1,189 patients with chest pain of suspected cardiac origin during an ongoing trial of prehospital thrombolytic therapy in acute myocardial infarction. Electrocardiograms were performed by paramedics 1.5 +/- 1.2 h after the onset of symptoms. Of 391 patients with evidence of acute myocardial infarction, 202 (52%) were identified as having ST segment elevation (acute injury) by the computer-interpreted ECG compared with 259 (66%) by an electrocardiographer (p less than 0.001). Of 798 patients with chest pain but no infarction, 785 (98%) were appropriately excluded by computer compared with 757 (95%) by an electrocardiographer (p less than 0.001). The positive predictive value of the computer- and physician-interpreted ECG was, respectively, 94% and 86% and the negative predictive value was 81% and 85%. Prehospital screening of possible candidates for thrombolytic therapy with the aid of a computerized ECG is feasible, highly specific and with further enhancement can speed the care of all patients with acute myocardial infarction.     

Urinary thromboxane A2 metabolites in patients presenting in the emergency room with acute chest pain

Abstract. Objectives . The diagnosis of acute myocardial infarction (MI) is difficult in emergency rooms where large groups of patients present with chest pain. Confirmation of the diagnosis of MI based on the myocardial band of creatine phosphokinase may take a day. A more rapid diagnostic screening procedure is desirable and for this reason we evaluated urine thromboxane. Design . The study consisted of patients presenting with chest pain. Urine samples were obtained in the emergency room and on the following 5 days for those patients who were admitted to the hospital. The urine samples were used to determine the levels of immunoreactive 11-dehydro-thromboxane B₂ (i-11-dehydro-TXB₂) and 2,3-dinor-thromboxane B₂ (i-2,3-dinor-TXB₂). Myocardial infarction was defined as an increase in the myocardial band fraction of plasma creatine phosphokinase (> 5% of the total) and changes in the electrocardiogram. The patients' diagnoses were retrospectively correlated with thromboxane metabolite levels. Setting . The present study took place in the emergency rooms of two major hospitals: Georgetown University Medical Center. Washington DC, and Fairfax Hospital, Virginia, USA. Subjects . The study comprised 369 patients presenting with acute chest pain and consisted of 247 men and 122 women aged 30–94 years. Main outcome measures . The outcome measure of this study was the predictive value of i-11-dehydro TXB₂ and i-2,3-dinor-TXB₂, for the diagnosis of MI, in patients presenting in the emergency room with chest pain. Results . Patients undergoing an MI had significantly higher levels of both thromboxane metabolites in their urine in the emergency room, when compared to patients undergoing a cardiac event other than an MI or to patients with unstable angina. Thromboxane metabolite levels rapidly returned to normal on the days following admission to the hospital. Aspirin intake appeared to significantly decrease the levels of i-11-dehydro-TXB₂, but not that of i-2,3-dinor-TXB₂. Conclusions . The measurement of thromboxane metabolites in the urine may provide a more rapid, accurate and cost-effective means of diagnosing MIs in patients presenting with chest pain.