Utility and diagnostic accuracy of hand-carried ultrasound for emergency room evaluation of chest pain

This study examined the utility and accuracy of immediate hand-carried echocardiography in patients presenting to the emergency room with chest pain and a normal or nondiagnostic electrocardiogram. Hand-carried echocardiography was highly concordant (kappa = 0.8) with troponin T tests as well as the discharge diagnosis of acute coronary syndrome, had a 100% sensitivity for the detection of acute coronary syndrome, 93% specificity, and 71% and 100% positive and negative predictive values, respectively.     

An evaluation of cocaine-induced chest pain

STUDY OBJECTIVE: To determine if enzymatic evidence of acute myocardial injury is present in patients complaining of chest pain after cocaine use when the ECG is normal or nondiagnostic. DESIGN: Serial ECG and creatinine kinase (CK) and CK isoenzymes (CK-ISO) determinations were performed at time of emergency department presentation and every six hours over 12 hours on individuals complaining of chest pain within six hours of last cocaine use. SETTING: ED of an urban tertiary care center. TYPE OF PARTICIPANTS: Forty-two individuals with a mean age of 28.5 years. INTERVENTIONS: Patients with positive CK-ISOs were admitted immediately to formally rule out myocardial infarction. Patients developing ECG changes during observation period also were admitted even if CK-ISOs were normal. Patients with unchanged ECGs and normal CK-ISOs were discharged after 12 hours of observation. RESULTS: Eight patients (19%) had elevated CK and CK-ISO values at presentation. Two of these patients had elevated values on three sequential determinations and were believed to have sustained acute myocardial infarction. Six patients had elevated CK and CK-ISOs at presentation only. ECGs remained normal or nondiagnostic in all patients. CONCLUSIONS: Enzymatic evidence of acute myocardial injury may occur in patients who develop chest pain after cocaine use and have normal or nondiagnostic ECGs. This injury may reflect acute infarction or transient ischemia. Single or serial normal or nondiagnostic ECGs do not rule out ischemia or injury in this group of patients.     

Chest pain emergency units.

Each year in the United States, more than 2 million patients are hospitalized with chest pain suggestive of myocardial ischemia, with fewer than 20% of these patients having an acute coronary event. Chest pain emergency units have been created to facilitate urgent therapy for patients with a serious cardiovascular event and to triage lower risk patients to less intensive, more cost-effective inpatient care or discharge to home. The clinical history, physical examination, and initial electrocardiogram are key to initial stratification of patients for further management, but additional methods are necessary to clearly distinguish patients with inconclusive findings at presentation as high- and low-risk. Innovative electrocardiographic methods have increased sensitivity for detecting myocardial ischemia. Accelerated diagnostic protocols with new cardiac serum markers can detect myocardial ischemia or infarction with increasing accuracy. Early echocardiographic, scintigraphic, and treadmill stress protocols can further evaluate patients who have nondiagnostic electrocardiograms and negative serum markers. This review presents the current status of chest pain emergency units and the evolving management strategies they encompass.     

Coronary artery calcium by digital cinefluoroscopy in patients with pain suggestive of an acute coronary syndrome

BACKGROUND: Detection of coronary calcium may be a useful noninvasive approach for detecting coronary artery disease (CAD) in subjects presenting to the emergency department with chest pain. HYPOTHESIS: We tried to assess the diagnostic value of coronary artery calcium (CAC) detection by digital cinefluoroscopy in patients with new-onset chest pain suggestive of an acute coronary syndrome. METHODS: In 97 consecutive patients (70 men, 27 women, mean standard deviation [SD] age 55 (11) and 60 (8) years, respectively), with new-onset chest pain suggestive of an acute coronary syndrome, nondiagnostic electrocardiogram, and normal initial creatine kinase (CK)-MB, digital cinefluoroscopy was performed for CAC detection. RESULTS: All patients underwent routine clinical evaluation with treadmill exercise test, thallium scintigraphy, dobutamine stress echocardiography, and coronary angiography, as needed clinically and blinded to the cinefluoroscopy results. Coronary artery calcium was present in 27 of 33 (81.8%) of patients with and in 10 of 64 (15.6%) of patients without CAD, p < 0.0001. The presence of CAC had 82% sensitivity, 84% specificity, 73% positive predictive value, and 90% negative predictive value for CAD diagnosis (odds ratio = 24.3, 95% confidence interval 7.98-73.94). CONCLUSIONS: In patients with acute chest pain, nondiagnostic electrocardiogram and normal initial enzyme evaluation, CAC detection by digital cinefluoroscopy appears to have high sensitivity, specificity, and negative predictive value for CAD diagnosis.     

Candidates for thrombolysis among emergency room patients with acute chest pain. Potential true- and false-positive rates

STUDY OBJECTIVE: To assess the potential clinical impact of thrombolytic therapy for acute myocardial infarction by determining true-positive and false-positive rates of criteria for eligibility among emergency room patients with acute chest pain. DESIGN: Prospective multicenter cohort study. SETTING: Emergency rooms of three university and four community hospitals. PATIENTS: Emergency room patients (7734) with acute chest pain. MEASUREMENTS AND MAIN RESULTS: Only 261 (23%) of 1118 patients with acute myocardial infarctions were 75 years of age or younger, presented within 4 hours of the onset of pain, and had emergency room electrocardiograms showing probable acute myocardial infarction: 60 (0.9%) of the 6616 patients without infarction also met these criteria (positive predictive value, 261/321 = 81%; CI, 77% to 86%). The positive predictive value could increase to about 88% (CI, 82% to 93%) if eligibility were based on the official hospital electrocardiogram reading. CONCLUSIONS: Because experience from published studies suggests that about one third of patients who meet these three eligibility criteria have other contraindications to thrombolysis, we estimate that about 15% of patients with acute myocardial infarction would meet the criteria for eligibility for thrombolysis that have been used in clinical trials at the time of emergency room presentation. Further, for every eight patients with true-positive results who are treated, one to two patients with false-positive results may also be treated if decisions are based on the interpretation of a single electrocardiogram.     

Evaluation of patients with chest pain and nondiagnostic ECG using thallium-201 myocardial planar imaging and technetium-99m first-pass radionuclide angiography in the emergency department.

STUDY OBJECTIVE: The purpose of this study was to determine if thallium-201 myocardial planar imaging and technetium-99m first-pass radionuclide angiography, performed in the emergency department, could predict which patients with acute chest pain and nondiagnostic ECGs were more likely to have an acute myocardial infarction (AMI). DESIGN: Retrospective analysis. SETTING: Urban, county ED. TYPE OF PARTICIPANTS: Convenience sample of 47 patients with acute chest pain suggestive of myocardial ischemia and nondiagnostic ECG. INTERVENTIONS: Thallium-201 myocardial imaging and technetium-99m first-pass radionuclide angiography in the ED. MEASUREMENTS AND MAIN RESULTS: Four patients had an AMI (ie, CK-MB greater than or equal to 6% total CK). The combined scans had a sensitivity of 75%, (95% confidence interval [Cl], 19-99%), a specificity of 42% (95% CI, 27-58%), an accuracy of 45% (95% CI, 19-99%), a positive predictive value of 11% (95% CI, 2-29%), and a negative predictive value of 95% (95% CI, 75-100%) in predicting AMI. CONCLUSION: Thallium-201 myocardial planar imaging and technetium-99m first-pass radionuclide angiography performed in the ED do not appear to be useful in determining which patients with acute chest pain and nondiagnostic ECG are likely to have an AMI.     

Nuclear Cardiology in the Evaluation of Acute Chest Pain in the Emergency Department

Only a minority of patients presenting to the emergency department (ED) with acute chest pain will eventually be diagnosed with an acute coronary syndrome. The majority will have an electrocardiogram that is normal or nondiagnostic for acute myocardial ischemia or infarction. Typically, these patients are admitted to exclude myocardial infarction despite a very low incidence of coronary artery disease. However, missed myocardial infarctions in patients who are inadvertently sent home from the ED have significant adverse outcomes and associated legal consequences. This leads to a liberal policy to admit patients with chest pain, presenting a substantial burden in terms of cost and resources. Many centers have developed chest pain centers, using a wide range of diagnostic modalities to deal with this dilemma. We discuss the methods currently available to exclude myocardial ischemia and infarction in the ED, focusing on the use of myocardial perfusion imaging as both an adjunct and an alternative to routine testing. We review the available literature centering on the ED evaluation of acute chest pain and then propose an algorithm for the practical use of nuclear cardiology in this setting.     

Planar myocardial perfusion imaging for evaluation of patients with acute chest pain

BACKGROUND: Rest single-photon emission computed tomographic (SPECT) perfusion imaging identifies acute myocardial ischemia in patients with chest pain in the emergency department; however, the costs are high and radioisotopic services are usually not available 24 h a day. Planar imaging through a portable gamma camera may be useful in this setting. However, planar imaging might be associated with less predictive values in comparison with a gated SPECT imaging. We sought to evaluate rest planar myocardial perfusion imaging for evaluation and triage of patients with suspected acute cardiac ischemia. METHODS: Patients within 6 h of chest pain onset and nondiagnostic electrocardiograms (ECGs) underwent planar myocardial perfusion imaging. Studies showing perfusion defects were considered suggestive of acute coronary syndromes. The results of planar scintigraphy were compared with the clinical diagnosis and outcomes. All patients were followed up and monitored for the occurrence of major cardiac events 120 days after hospital discharge. RESULTS: 71 patients underwent scintigraphy. Twenty-one (30%) patients had acute coronary syndromes, 15 (21%) had major cardiac events (8 had myocardial infarction and 7 underwent myocardial revascularization). Planar scintigraphy demonstrated perfusion defects in 21 patients, 16 (76%) patients with acute coronary syndromes, 12 (80%) patients who had major cardiac events and in 7 (88%) patients with myocardial infarction. The negative predictive value of planar scintigraphy was 90% for diagnosis of acute coronary syndromes and 94% for detecting major cardiac events. CONCLUSION: Early planar myocardial perfusion imaging allowed rapid and accurate risk stratification of emergency departments patients with possible myocardial ischemia and nondiagnostic ECGs.     

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.     

Immediate exercise testing of low risk patients with known coronary artery disease presenting to the emergency department with chest pain

OBJECTIVES

The purpose of this study was to demonstrate the safety and utility of immediate exercise treadmill testing (IETT) of low risk patients presenting to the emergency department with known coronary artery disease (CAD).

BACKGROUND

More than 70% of the two million patients admitted to U.S. hospitals annually for suspected acute myocardial infarction (AMI) are found not to have had a cardiac event. We have previously demonstrated the safety and efficacy of IETT of selected low risk patients without known CAD presenting to the emergency department with chest pain. This study extends this approach to selected patients with a history of CAD.

METHODS

One hundred patients evaluated by the chest pain emergency room to rule out AMI underwent IETT using a modified Bruce protocol upon admission to the hospital (median time <1 h).

RESULTS

Twenty-three patients (23%) had positive exercise electrocardiograms (ExECGs); an uncomplicated non–Q wave AMI was diagnosed in two patients. Thirty-eight patients (38%) had negative ExECGs and 39 patients (39%) had nondiagnostic ExECGs. Of these 100 patients, 64 were discharged immediately after IETT, 19 were discharged in less than 24 h after negative serial cardiac enzymes and stable electrocardiograms and 17 were discharged after further evaluation and treatment. There were no complications from exercise testing and no late deaths or AMI during six-month follow-up.

CONCLUSIONS

Immediate exercise treadmill testing of low risk patients with chest pain and known CAD is effective in further stratifying this group into patients who can be safely discharged and those who require hospital admission.     

Utility of echocardiography for the early assessment of patients with nondiagnostic chest pain

A two-dimensional (2D) echocardiogram was recorded shortly after admission in 46 patients with nondiagnostic chest pain. Eighteen patients were studied during chest pain and 28 were studied following the resolution of chest pain. Of the 18 patients studied during chest pain, six of the eight patients who had a regional wall motion abnormality (RWMA) evolved an acute infarction and the remaining two patients had evidence of significant coronary artery disease. Only 1 of 10 patients without a RWMA evolved an infarction and none had significant coronary artery disease. Of the 28 patients studied following the resolution of chest pain, 8 of the 10 patients with a RWMA evolved an acute infarction and one patient had evidence of significant coronary artery disease, whereas of 18 patients without a RWMA, none evolved an acute infarction and five had evidence of significant coronary artery disease. These data suggest that in patients presenting with nondiagnostic chest pain, an early assessment of regional wall motion by 2D echocardiography can reliably differentiate patients with myocardial ischemia or early infarction from patients with nonischemic chest pain when performed during an episode of chest pain; can also identify those patients with early acute myocardial infarction, even when performed following the resolution of chest pain; but is not useful for the detection of patients with significant coronary artery disease without infarction when performed following the resolution of chest pain.     

The de Winter ECG Pattern in the Absence of Acute Coronary Artery Occlusion

A 26-year-old man presented to the emergency department with chest pain and electrocardiogram (ECG) changes compatible with the de Winter pattern. Emergent coronary angiography was used to rule out the presence of significant stenosis. Cardiac magnetic resonance imaging confirmed the diagnosis of myocarditis. This case underlines the lack of data regarding the positive predictive value of this ECG pattern for the diagnosis of acute myocardial infarction. Until further prospective studies are available, we believe that the de Winter ECG pattern should be considered as an “ST-elevation equivalent” when myocardial ischemia is suspected.     

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.     

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.     

Diagnostic value of Q waves outside standard precordial lead points in left anterior myocardial infarction undetectable by standard 12-lead electrocardiogram

Body surface potential maps were recorded for 52 patients with solitary anterior myocardial infarction and 57 normal subjects. All patients had pure anterior wall asynergy on a left ventriculogram but no diagnostic Q wave on the standard 12-lead electrocardiogram. Q wave (greater than 30 msec) distributions on the body surface of the patients and normals were compared. The frequency of Q waves in the area above V1-V2 and in the right middle chest was significantly higher in patients than in normals. The sensitivity of Q waves for asynergy in leads from both these areas was 19-60%. The positive predictive value was 67-94%. The frequency of Q waves was significantly higher in severe asynergy than in mild asynergy. A combination of two selected unipolar leads from these areas yielded a sensitivity and specificity of 33% and 95%, respectively. With a combination of three leads, these values were 42% and 93% and with four leads 48% and 88%, respectively. The results indicate that several unipolar leads from the area above V1-V2 and from the right middle chest in addition to the standard 12-lead electrocardiogram may improve the electrocardiographic diagnostic accuracy of myocardial infarction.     

Adenosine Stress Magnetic Resonance Imaging in Women With Low Risk Chest Pain: The Emory University Experience

ObjectivesThe purpose of this study was to evaluate the accuracy of adenosine stress magnetic resonance imaging (ASMRI) for the evaluation of women with low-risk chest pain (CP).BackgroundCoronary artery disease (CAD) can present differently among women than among men. There is increased interest in the use of ASMRI for lower risk patients in the emergency department to rule out CAD, and it would be valuable to assess its performance specifically in women.MethodsThis study included 82 women with low-risk CP who presented to the emergency department during a 2-year period at our institution and were evaluated by ASMRI. Clinical events were followed by review of medical records.ResultsThe specificity of ASMRI for ischemia detection in this small cohort of patients was 100%. Sensitivity was 94.9%, negative predictive value 100%, and positive predictive value 42.9%.ConclusionsASMRI may be used as the initial imaging modality for ruling out CAD in women with low-risk CP because of its very high sensitivity, specificity, and negative predictive value for the detection of ischemia. Further randomized controlled trials comparing ASMRI with established noninvasive nuclear and echocardiographic stress modalities are needed.     

Clinical Value of Acute Rest Technetium-99m Tetrofosmin Tomographic Myocardial Perfusion Imaging in Patients With Acute Chest Pain and Nondiagnostic Electrocardiograms

Objectives. We sought to evaluate the clinical use and cost-analysis of acute rest technetium-99m (Tc-99m) tetrofosmin single-photon emission computed tomographic (SPECT) myocardial perfusion imaging in patients with chest pain and a normal electrocardiogram (ECG).Background. Current approaches used in emergency departments (EDs) for treating patients presenting with chest pain and a nondiagnostic ECG result in poor resource utilization.Methods. Three hundred fifty-seven patients presenting to six centers with symptoms suggestive of myocardial ischemia and a nondiagnostic ECG underwent Tc-99m tetrofosmin SPECT during or within 6 h of symptoms. Follow-up evaluation was performed during the hospital period and 30 days after discharge. All entry ECGs, SPECT images and cardiac events were reviewed in blinded manner and were not available to the admitting physicians.Results. By consensus interpretation, 204 images (57%) were normal, and 153 were abnormal (43%). Of 20 patients (6%) with an acute myocardial infarction (MI) during the hospital period, 18 had abnormal images (sensitivity 90%), whereas only 2 had normal images (negative predictive value 99%). Multiple logistic regression analysis demonstrated abnormal SPECT imaging to be the best predictor of MI and significantly better than clinical data. Using a normal SPECT image as a criterion not to admit patients would result in a 57% reduction in hospital admissions, with a mean cost savings per patient of $4,258.Conclusions. Abnormal rest Tc-99m tetrofosmin SPECT imaging accurately predicts acute MI in patients with symptoms and a nondiagnostic ECG, whereas a normal study is associated with a very low cardiac event rate. The use of acute rest SPECT imaging in the ED can substantially and safely reduce the number of unnecessary hospital admissions.     

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.     

Beat-to-beat morphologic variability of the electrocardiogram for the evaluation of chest pain in the emergency room.

The value of electrocardiographic, morphologic variability in the early diagnosis of acute myocardial infarction (AMI) and myocardial ischemia was evaluated in 49 nonselected patients presenting to the emergency room with chest pain. High-resolution electrocardiography was used to determine the morphologic variability of consecutive electrocardiographic complexes, and the ratio of the variance of the QRS onset to that of the entire electrocardiogram was calculated. A final diagnosis of AMI was confirmed in 8 patients, acute coronary insufficiency in 8, angina pectoris in 19, and a noncardiac origin for chest pain in 14. Patients with AMI had a significantly higher beat-to-beat electrocardiographic morphologic variability of the QRS onset (1.4 +/- 0.2) than did those with acute coronary insufficiency (1.1 +/- 0.2), angina pectoris (0.9 +/- 0.1) or noncardiac chest pain (0.8 +/- 0.1) (p < 0.05). The sensitivity of the clinical presentation, typical electrocardiographic changes and creatine phosphokinase levels for the diagnosis of an acute ischemic event on admission to the emergency room was 62, 25 and 37.5%, respectively. Relative variance of the QRS onset of > 0.86 had a sensitivity of 75% and a specificity of 61% for diagnosing an acute ischemic event. Logistic regression of these variables showed that the QRS onset relative variability is an independent predictor for an acute ischemic event. It is concluded that an increased beat-to-beat electrocardiographic variability in patients with AMI is present on admission to the emergency room and may assist in establishing the diagnosis in this setting.     

Importance of posterior chest leads in patients with suspected myocardial infarction, but nondiagnostic, routine 12-lead electrocardiogram

Criteria for reperfusion therapy in acute myocardial infarction require the presence of ST elevation in 2 contiguous leads. However, many patients with myocardial infarction do not show these changes on a routine 12-lead electrocardiogram and hence are denied reperfusion therapy. Posterior chest leads (V7 to V9) were recorded in 58 patients with clinically suspected myocardial infarction, but nondiagnostic routine electrocardiogram. ST elevation >0.1 mV or Q waves in > or =2 posterior chest leads were considered to be diagnostic of posterior myocardial infarction. Eighteen patients had these changes of posterior myocardial infarction. All 18 patients were confirmed to have myocardial infarction by creatine phosphokinase criteria or cardiac catheterization. Of the 17 patients who had cardiac catheterization, 16 had left circumflex as the culprit vessel. We conclude that posterior chest leads should be routinely recorded in patients with suspected myocardial infarction and nondiagnostic, routine electrocardiogram. This simple bedside technique may help proper treatment of some of these patients now classified as having unstable angina or non-Q-wave myocardial infarction.