Comparison of myocardial perfusion imaging and cardiac troponin I in patients admitted to the emergency department with chest pain

The chest pain guidelines revisited: cherry picking from the frequentist tree

The new chest pain guideline document was recently released. The biggest changes are in the recommendations for intermediate and high-risk patients with known and unknown CAD. Coronary CT angiography has been recommended as the preferred imaging test for patients < 65 years old with chest pain. This paper will review the major evidence and omissions in the document that prompted that recommendation and provide thoughts on potential actions going forward.

Influences of radionuclides on left ventricular phase analysis of gated myocardial perfusion single-photon emission computed tomography images in ischemic heart disease

OBJECTIVE

Phase analysis is expected to improve the accuracy of myocardial ischemia diagnosis in conjunction with myocardial perfusion and wall motion imaging and quantification. Although previous studies have reported perfusion image disagreements in relation to radionuclides, a few reports have examined the influences of radionuclides on phase analysis. We evaluated the influences of different radionuclides on stress-induced left ventricular mechanical dyssynchrony by phase analysis using electrocardiogram (ECG)-gated myocardial perfusion single photon emission computed tomography (SPECT) (MPS) imaging in patients with ischemic heart disease (IHD).

METHODS

A total of 202 patients with suspected or known IHD were investigated retrospectively. All the patients underwent coronary arteriography and were subsequently classified into the following groups: 43 patients without any coronary lesion (0VD), 71 patients with single-vessel disease (1VD), 59 patients with two-vessel disease (2VD), and 29 patients with three-vessel disease (3VD). Both stress and rest gated-MPS were performed using 99mTc-methoxyisobutylisonitrile (MIBI)/tetrofosmin (TF) in 118 patients and with 201TlCl in 84 patients. Phase analysis was performed to obtain the peak phase, phase standard deviation (SD), and bandwidth. Finally, we investigated potential differences between the phase analysis indices and the respective radionuclides used.

RESULTS

The peak phase did not exhibit any significant differences in the numbers of affected branches in either 99mTc-MPS or 201Tl-MPS during stress or rest MPS. Furthermore, both the phase SD and bandwidth demonstrated a tendency to increase in patients with increased numbers of affected branches. A significant difference was observed in the stress MPS when 99mTc-MIBI/TF was used (p < 0.05), but no significant difference was observed in the stress MPS when 201TlCl was used. Both the phase SD and bandwidth of all patients in 99mTc-MPS during stress were significantly larger than those at rest (p < 0.05). Conversely, both the phase SD and bandwidth of all patients in 201Tl-MPS at stress was significantly smaller than that at rest (p < 0.05).

CONCLUSION

Phase analysis using 99mTc-MPS was considered to be useful for the detection of stress-induced left ventricular mechanical dyssynchrony, although it is necessary to be careful when using 201Tl-MPS.

Diagnosis and Prognosis of Coronary Artery Disease with SPECT and PET

PURPOSE OF REVIEW

Radionuclide myocardial perfusion imaging (MPI) continues to be the most reliable modality for diagnosis of hemodynamically significant coronary artery disease (CAD). The application of radionuclide MPI using single photon emission computed tomography (SEPCT) and positron emission tomography (PET) for CAD is reviewed, with emphasis on diagnosis and risk stratification.

RECENT FINDINGS

Contemporary studies have reported the diagnostic and prognostic value of novel imaging protocols, employing stress-first or stress-only approach. In addition, the superior diagnostic value of PET has been established with a role of assessment of myocardial blood flow to improve risk stratification. The utility of MPI in special populations, such as the elderly, women, and diabetic patients has also been recently evaluated. Furthermore, multicenter studies have reported a similar diagnostic and prognostic value of radionuclide MPI compared with other functional and anatomical techniques for CAD. Radionuclide MPI with SPECT and PET are efficacious for diagnosis and prognosis of CAD. Its universal application in varied patient populations highlights its excellent clinical effectiveness.

Imaging the myocardial ischemic cascade

Non-invasive imaging plays a growing role in the diagnosis and management of ischemic heart disease from its earliest manifestations of endothelial dysfunction to myocardial infarction along the myocardial ischemic cascade. Experts representing the North American Society for Cardiovascular Imaging and the European Society of Cardiac Radiology have worked together to organize the role of non-invasive imaging along the framework of the ischemic cascade. The current status of non-invasive imaging for ischemic heart disease is reviewed along with the role of imaging for guiding surgical planning. The issue of cost effectiveness is also considered. Preclinical disease is primarily assessed through the coronary artery calcium score and used for risk assessment. Once the patient becomes symptomatic, other imaging tests including echocardiography, CCTA, SPECT, PET and CMR may be useful. CCTA appears to be a cost-effective gatekeeper. Post infarction CMR and PET are the preferred modalities. Imaging is increasingly used for surgical planning of patients who may require coronary artery bypass.

Diagnostic parameters of CK–MB and myoglobin related to chest pain duration

Objective:

Cardiac marker sensitivity depends on chest pain duration at the time of sampling. Our objective was to estimate the sensitivity, specificity, and likelihood ratios of early CK–MB and myoglobin assays in patients presenting to the emergency department (ED) with nondiagnostic ECGs, stratified by the duration of ongoing chest pain at the time of ED assessment.

Methods:

This was a prospective observational study carried out in 10 US and 2 Canadian EDs. Patients &gt;25 years of age with ongoing chest pain and nondiagnostic ECGs were stratified by pain duration (0–4 h, 4–8 h, 8–12 h, &gt;12 h). CK–MB and myoglobin assays were drawn at T = 0 (ED assessment) and T = 1 hr. Patients were followed for 7–14 days to identify all cases of acute myocardial infarction (AMI). ED test results were correlated with patient outcomes.

Results:

Of 5005 eligible patients, 565 had AMI. Pain duration was 0–4 h in 3014 patients, 4–8 h in 961, 8–12 h in 487, and &gt;12 h in 543. Marker sensitivity increased with pain duration, ranging from 28%–77% for CK–MB and 39%–73% for myoglobin. The maximal sensitivity achieved by a T = 0 assay was 73%, and this was in patients with 8–12 or &gt;12 h of ongoing pain. No combination of tests achieved 90% sensitivity in any pain duration strata.

Conclusions:

Regardless of chest pain duration, single assays and early serial markers (0+1 hr) do not rule out AMI; therefore, serial assays over longer observation periods are required. Likelihood ratios derived in this study will help physicians who use Bayesian analysis to determine post-test AMI likelihood in patients with chest pain.

Stress myocardial perfusion imaging for the evaluation and triage of chest pain in the emergency department: a randomized controlled trial

BACKGROUND

Patients with acute coronary syndrome (ACS) often present atypically. In a randomized controlled trial, we studied whether adding stress myocardial perfusion imaging (SMPI) to an evaluation strategy for emergency department (ED) patients presenting with chest pain more effectively identifies patients with ACS.

METHODS

Participants were randomized to standard ED chest pain protocol (clinical assessment) or standard protocol supplemented with SMPI results. During 6 hours of electrocardiogram (ECG) monitoring and serial cardiac markers (creatine kinase-MB isoenzyme, troponin), participants developing ST segment changes or elevated cardiac markers were admitted. Those with a negative observation period underwent SMPI (N = 1,004) or clinical assessment (N = 504) based on randomization, and admitted if their SMPI scan was abnormal or senior clinicians found a high or intermediate risk for ACS.

RESULTS

SMPI participants had a significantly lower admission rate than clinical assessment participants (10.16% vs 18.45%), with no significant between-group differences in risk of cardiac events (CEs) after 30 days (0.40% vs 0.79%) or 1 year (0.70% vs 0.99%).

CONCLUSIONS

When added to a standard triage strategy incorporating clinical evaluation, serial ECGs, and cardiac markers, SMPI improved clinical decision making for chest pain patients, significantly reducing the need for hospitalization without an increase in adverse CE rates at 30 days or 1 year.

Imaging strategies for acute chest pain in the emergency department

OBJECTIVE

Echocardiography, radionuclide myocardial perfusion imaging (MPI), and coronary CT angiography (CTA) are the three main imaging techniques used in the emergency department for the diagnosis of acute coronary syndrome (ACS). The purpose of this article is to quantitatively examine existing evidence about the diagnostic performance of these imaging tests in this setting.

CONCLUSION

Our systematic search of the medical literature showed no significant difference between the modalities for the detection of ACS in the emergency department. There was a slight, positive trend favoring coronary CTA. Given the absence of large differences in diagnostic performance, practical aspects such as local practice, expertise, medical facilities, and individual patient characteristics may be more important.

ACR Appropriateness Criteria(®) acute nonspecific chest pain-low probability of coronary artery disease

This document outlines the usefulness of available diagnostic imaging for patients without known coronary artery disease and at low probability for having coronary artery disease who do not present with classic signs, symptoms, or electrocardiographic abnormalities indicating acute coronary syndrome but rather with nonspecific chest pain leading to a differential diagnosis, including pulmonary, gastrointestinal, or musculoskeletal pathologies. A number of imaging modalities are available to evaluate the broad spectrum of possible pathologies in these patients, such as chest radiography, multidetector CT, MRI, ventilation-perfusion scans, cardiac perfusion scintigraphy, transesophageal and transthoracic echocardiography, PET, spine and rib radiography, barium esophageal and upper gastrointestinal studies, and abdominal ultrasound. It is considered appropriate to start the assessment of these patients with a low-cost, low-risk diagnostic test such as a chest x-ray. Contrast-enhanced gated cardiac and ungated thoracic multidetector CT as well as transthoracic echocardiography are also usually considered as appropriate in the evaluation of these patients as a second step if necessary. A number of rest and stress single-photon emission CT myocardial perfusion imaging, ventilation-perfusion scanning, aortic and chest MR angiographic, and more specific x-ray and abdominal examinations may be appropriate as a third layer of testing, whereas MRI of the heart or coronary arteries and invasive testing such as transesophageal echocardiography or selective coronary angiography are not considered appropriate in these patients. Given the low risk of these patients, it is mandated to minimize radiation exposure as much as possible using advanced and appropriate testing protocols. The ACR Appropriateness Criteria® are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

The role of non-invasive imaging in patients with suspected acute coronary syndrome

This article gives an overview of the role of imaging in the diagnosis and management of acute coronary syndrome.

Evaluation of acute chest pain in the emergency department: "triple rule-out" computed tomography angiography

Triage of patients with acute, potentially life-threatening chest pain is one of the most important issues currently facing physicians in the emergency department. Appropriate evaluation of these patients begins with a skilled assessment of the individual patient's presenting symptoms and a careful review of his or her history and physical examination, often followed by serial recording of electrocardiograms and measurement of serum biochemical markers such as troponin and d-dimer. Stress testing, often accompanied by rest and stress myocardial perfusion imaging or echocardiography, and other diagnostic testing such as radionuclide lung scanning and invasive angiography may be required. A rapid, accurate, and cost-effective approach for the evaluation of emergency department patients with chest pain is needed. Development of newer generations of multidetector computed tomographic (MDCT) scanners, which are capable not only of performing high-quality noninvasive coronary angiography, but also concurrent aortic and pulmonary angiography, has led to increased use of MDCT for the so-called "triple rule out." MDCT is used for the detection of 3 of the most common life-threatening causes of chest pain-coronary artery disease, acute aortic syndrome, and pulmonary emboli. While triple rule-out protocol can be very useful and potentially cost effective when used appropriately, concern has risen regarding the overuse of this technology, which could expose patients to unnecessary radiation and iodinated contrast. The triple rule-out protocol is most appropriate for patients who present with acute chest pain, but are judged to have low to intermediate increased risk for acute coronary syndrome, and whose chest pain symptoms might also be attributed to acute pathologic conditions of the aorta or pulmonary arteries. MDCT should not be used as a routine screening procedure. Continued technical improvements in acquisition speed and spatial resolution of computed tomography images, and development of more efficient image reconstruction algorithms which reduce patient exposure to radiation and contrast, may result in increased popularity of MDCT for "triple rule-out."

Prediction of future cardiac events using myocardial perfusion SPECT: a middle-term follow-up study

BACKGROUND

Myocardial perfusion imaging (MPI) provides highly valuable information for risk stratification and determination of optimal clinical management. The goal of the present study was to assess the prognostic value of myocardial perfusion SPECT for the prediction of future cardiac events in Asian population.

METHODS

Five hundred and ten consecutive patients, who had undergone myocardial perfusion SPECT between 2005 and 2006, were prospectively followed-up. Patients' data were collected from recorded files. Follow-ups were performed by scripted telephone interviews by a physician blinded to the patients' MPI results and also from the hospital records. The total completed follow-ups consisted of 482 patients (follow-up rate, 94.5%).

RESULTS

Over the mean follow-up period of 434 ± 62 days, 14 out of 482 patients (2.9%) died from cardiac events. Also in 61 patients (12.7%), the clinical condition led to a cardiac intervention (Percutaneous coronary intervention or coronary artery bypass grafting). Those patients without cardiac events on follow-up (including cardiac death or myocardial infarction) were younger and with less severity of MPI abnormalities. Severe MPI abnormalities (Summed Stress Score > 13) were found in 42.9% of those with cardiac death, while in 17.2% of those with myocardial infarction. The rate of cardiac death had a direct relationship with the severity of scan abnormalities, however, the same association was not found between the severity of MPI abnormality and the rate of myocardial infarction.

CONCLUSION

MPI is a valuable tool for risk stratification and prediction of future fatal cardiac events in Asian population. The risk of cardiac death as a mid-term outcome of coronary artery disease increases significantly with severity of MPI abnormalities.

Assessment of cardiac ischaemia and viability: role of cardiovascular magnetic resonance

Over the past years, cardiovascular magnetic resonance (CMR) has proven its efficacy in large clinical trials, and consequently, the assessment of function, viability, and ischaemia by CMR is now an integrated part of the diagnostic armamentarium in cardiology. By combining these CMR applications, coronary artery disease (CAD) can be detected in its early stages and this allows for interventions with the goal to reduce complications of CAD such as infarcts and subsequently chronic heart failure (CHF). As the CMR examinations are robust and reproducible and do not expose patients to radiation, they are ideally suited for repetitive studies without harm to the patients. Since CAD is a chronic disease, the option to monitor CAD regularly by CMR over many decades is highly valuable. Cardiovascular magnetic resonance also progressed recently in the setting of acute coronary syndromes. In this situation, CMR allows for important differential diagnoses. Cardiovascular magnetic resonance also delineates precisely the different tissue components in acute myocardial infarction such as necrosis, microvascular obstruction (MVO), haemorrhage, and oedema, i.e. area at risk. With these features, CMR might also become the preferred tool to investigate novel treatment strategies in clinical research. Finally, in CHF patients, the versatility of CMR to assess function, flow, perfusion, and viability and to characterize tissue is helpful to narrow the differential diagnosis and to monitor treatment.

Assessment of acute myocardial infarction: current status and recommendations from the North American society for Cardiovascular Imaging and the European Society of Cardiac Radiology

There are a number of imaging tests that are used in the setting of acute myocardial infarction and acute coronary syndrome. Each has their strengths and limitations. Experts from the European Society of Cardiac Radiology and the North American Society for Cardiovascular Imaging together with other prominent imagers reviewed the literature. It is clear that there is a definite role for imaging in these patients. While comparative accuracy, convenience and cost have largely guided test decisions in the past, the introduction of newer tests is being held to a higher standard which compares patient outcomes. Multicenter randomized comparative effectiveness trials with outcome measures are required.

Comparison of myocardial contrast echocardiography versus rest sestamibi myocardial perfusion imaging in the early diagnosis of acute coronary syndrome

BACKGROUND

It remains unclear whether myocardial contrast echocardiography (MCE) is as accurate as myocardial perfusion imaging with technetium-99m sestamibi (MPI) for the diagnosis of acute coronary syndrome (ACS). We sought to directly compare the diagnostic accuracy of MCE with resting MPI in a head-to-head fashion.

METHODS

We prospectively enrolled 98 consecutive patients (mean age; 59+/-9 years, 68 males) who presented to the emergency department with chest pain suggestive of acute myocardial ischemia. Early MCE was performed by using continuous infusion of perfluorocarbon-exposed sonicated dextrose albumin (PESDA) during intermittent power Doppler harmonic imaging. Myocardial perfusion defects observed in at least one coronary territory were considered positive. Sestamibi was injected immediately after MCE and MPI was obtained within 6 hours of tracer injection.

RESULTS

ACS was confirmed in 67 patients. There were 32 patients with acute myocardial infarction (AMI) and 35 patients with unstable angina requiring urgent revascularization. The sensitivities of MCE and MPI for the diagnosis of ACS were 72% and 61%, respectively, which were significantly higher than those of ST segment change (24%, p<0.001 vs. MCE and vs. MPI) and troponin I (27%, p<0.001 vs. MCE and vs. MPI), with similar specificities of 90% to 100%. On a receiveroperating characteristics curve demonstrating diagnostic accuracy for ACS, the area under the curve of MCE was significantly larger than that of MPI (0.86 vs. 0.77, respectively; p=0.019).

CONCLUSION

MCE and MPI overcome the low sensitivity of routine triage tests for detecting ACS, and MCE is more accurate than MPI for the diagnosis of ACS in the emergency department.

A predictive instrument using contrast echocardiography in patients presenting to the emergency department with chest pain and without ST-segment elevation

OBJECTIVE

Risk stratification of patients presenting to the emergency department (ED) with suspected cardiac chest pain (CP) and an undifferentiated electrocardiogram (ECG) is difficult. We hypothesized that in these patients a risk score incorporating clinical, ECG, and myocardial contrast echocardiography (MCE) variables would accurately predict adverse events occurring within the next 48 hours.

METHODS

Patients with CP lasting for 30 minutes or more who did not have ST-segment elevation on the ECG, were enrolled. Regional function (RF) and myocardial perfusion (MP) were assessed by MCE. A risk model was developed in the initial 1166 patients (cohort 1) and validated in subsequent 720 patients (cohort 2). Any abnormality or ST changes on ECG (odds ratio [OR] 2.5; 95% confidence interval [CI], 1.4-4.5, P = .002, and OR 2.9, 95% CI, 1.7-4.8, P < .001, respectively), abnormal RF with normal MP (OR 3.5, 95% CI, 1.8-6.5, P < .001), and abnormal RF with abnormal MP (OR 9.6, 95% CI, 5.8-16.0, P < .001) were found to be significant multivariate predictors of nonfatal myocardial infarction or cardiac death.

RESULTS

The estimate of the probability of concordance for the risk model was 0.82 for cohort 1 and 0.83 for cohort 2. The risk score in both cohorts stratified patients into 5 distinct risk groups with event rates ranging from 0.3% to 58%.

CONCLUSION

A simple predictive instrument has been developed from clinical, ECG, and MCE findings obtained at the bedside that can accurately predict events occurring within 48 hours in patients presenting to the ED with suspected cardiac CP and an ECG that is not diagnostic for acute ischemic injury. Its application could enhance care of patients with CP in the ED. For instance, patients with a risk score of 0 could be discharged from the ED without further workup. However, this needs to be validated in a multicenter study.

Rest myocardial perfusion imaging in a patient with atypical chest pain and a nondiagnostic electrocardiogram

ACC/AHA guidelines assign a class I indication for use of myocardial perfusion imaging (MPI) for the evaluation of chest pain in patients with acute coronary syndromes and a nondiagnostic ECG. However, MPI is not a widely used modality for the evaluation of patients who present to the ER with chest pain and an intermediate pretest probability for coronary artery disease.We report a case in which resting MPI was pivotal in diagnosing acute myocardial infarction and expedited the appropriate reperfusion strategy.

Cardiac radionuclide imaging in stable coronary artery disease and acute coronary syndromes

INTRODUCTION

The increasing number of available cardiac imaging techniques has made the investigation of coronary artery disease (CAD) more complex. Appropriate patient referral depends on an understanding of the pre-test likelihood of CAD and the information provided by each test.

SOURCES OF DATA

This article describes myocardial perfusion scintigraphy (MPS) and summarizes evidence for its role in stable CAD and acute coronary syndromes with particular reference to current guidelines.

AREAS OF AGREEMENT

MPS has been extensively validated for the cost-effective diagnosis and prognosis of functionally significant CAD in both the acute and chronic settings. Its use is emphasized in the current NICE, national and international guidelines.

AREAS OF CONTROVERSY

Although normal MPS is associated with good outcomes, assessments of subclinical atherosclerosis such as coronary artery calcium scoring and computed tomography coronary angiography (CTA) demonstrate that non-flow-limiting CAD remains prognostically important.

GROWING POINTS

Technological developments, such as attenuation correction to improve diagnostic accuracy or analysis of left ventricular phase to detect dyssynchrony, carry the possibility of increasing the information that can be usefully gained from a single MPS study.

AREAS TIMELY FOR DEVELOPING RESEARCH

Of particular importance will be the role of MPS in an integrated imaging strategy that involves both anatomical and functional cardiac assessments. The use of hybrid technology that combines techniques such as MPS and CTA into a single imaging unit requires careful consideration with regard to diagnostic usefulness and cost-effectiveness.

Use and Misuse of Cardiac Troponins in Clinical Practice

Cardiac troponins are very sensitive and specific markers of myocardial injury. Elevated troponin levels in the setting of acute coronary syndrome are diagnostic of acute myocardial infarction and provide guidance to clinicians with regard to appropriate use of intensive medical and revascularization therapies. However, elevated troponin levels are commonly seen in several noncoronary ischemia presentations and create considerable confusion among clinicians in these settings. In this review article, we discuss the utility of troponins in various clinical settings and present a "common sense" approach to interpreting troponin elevation outside the setting of acute coronary syndrome.

The role of cardiovascular imaging techniques in the assessment of patients with acute chest pain

Chest pain is the most common presenting symptom of coronary artery disease. The assessment and appropriate management of patients with acute chest pain and non-diagnostic electrocardiograms (ECGs) remain a continuing clinical problem, with major logistic and financial implications for health-care providers. Cardiovascular imaging is at the forefront of health care, experiencing rapid changes over the recent years, particularly with the use of advanced medical technologies. Imaging techniques like acute rest myocardial perfusion imaging (MPI), echocardiography, electron beam computed tomography (CT), cardiac magnetic resonance imaging (MRI) and multi-detector CT (MDCT) have been used recently in the evaluation and triage of patients with chest pain in addition to the conventional investigations such as ECGs and cardiac biomarkers in the chest pain units. The annual potential cost savings, by incorporating the routine use of acute rest MPI in patients with low-to-moderate risk and non-diagnostic ECGs are substantial. The high negative predictive value of a normal resting MPI in patients with chest pain for myocardial infarction and future cardiac events is well established. Echocardiography is also considered to be useful but the technique is operator dependent and at present there is insufficient data to support its use. Cardiac MRI is expensive and time consuming and there is insufficient diagnostic and prognostic data to make it suitable for chest pain patients at present. There has been increasing interest in MDCT recently, especially with the advent of 64-slice CT but the sensitivity and specificity in chest pain patients are no better than MPI so far.

Yield of early rest and stress myocardial perfusion single-photon emission computed tomography and electrocardiographic exercise test in patients with atypical chest pain, nondiagnostic electrocardiogram, and negative biochemical markers in the emergency department

There are no studies in which diagnostic yield of early rest myocardial perfusion gated single-photon emission computed tomography (SPECT), electrocardiographic exercise testing, and stress SPECT were compared in patients with atypical chest pain, nondiagnostic electrocardiograms (ECGs), and negative markers of myocardial damage in the emergency department. A prospective study of 96 patients who presented with atypical chest pain and nondiagnostic ECG, but without elevated markers of necrosis, was performed. All underwent rest gated SPECT using technetium-99m methoxyisobutyl isonitrile within 6 hours after pain subsided followed by an electrocardiographic exercise test to obtain stress-rest SPECT images. After 1 year, there were no deaths and coronary artery disease was confirmed in only 5 patients. Negative predictive values of the 3 techniques were high (99%, 96%, and 100%, respectively), but positive predictive values were low (27%, 22%, and 14%, respectively). Sensitivities of early SPECT (80%) and stress SPECT (100%) were higher than for the electrocardiographic exercise test (40%). In conclusion, in patients with atypical chest pain, nondiagnostic ECG, and negative biochemical markers, negative predictive values of the 3 tests analyzed are very high. The sensitivity of radionuclide tests is higher, but their widespread use does not appear warranted because their positive predictive value and incidence of complications is low.

Noninvasive cardiac imaging in the evaluation of suspected acute coronary syndromes

Optimal management of patients presenting with chest pain to the emergency department is a major challenge, both in terms of a diagnostic dilemma and consumption of resources. The triage of such patients can be aided vastly by the appropriate use of noninvasive imaging. Noninvasive imaging modalities such as echocardiogram, radionuclide perfusion studies, positron emission tomography, cardiac magnetic resonance imaging and computed tomography have all been demonstrated to have favorable diagnostic and prognostic value, with an enhanced sensitivity to detect acute ischemia. A normal noninvasive evaluation in the appropriate clinical setting presents a strong argument against acute ischemia as an etiology of the chest pain. Randomized trials of both rest and stress imaging in the emergency department have confirmed a reduction in unnecessary hospitalizations and cost savings without compromising the safety of the patient. Cardiac magnetic resonance and computed tomography would provide an insight into subendocardial ischemia, the detection of which has previously been difficult, using single-photon emission tomography and echocardiography. In this review, novel hot-spot imaging modalities are discussed including infarct-avid imaging agents and ischemia-avid imaging agents, thus elucidating the pathophysiology of reperfusion-induced cell death. These agents represent work in evolution and are likely to be used routinely in the future as understanding of coronary syndromes and coronary artery disease becomes clearer.

Emergency cardiac imaging: state of the art

Multiple strategies and testing modalities are available to evaluate patients presenting to the emergency department with cardiac complaints. Many provide anatomic and prognostic information about coronary stenosis and long-term out-comes. Although nuclear and stress echo imaging have the ability to predict outcomes in patients in the emergency department population, the newer modalities of cardiac imaging (EBCT, MDCT,and CMR) continue to show promising results and may soon be incorporated into emergency department chest pain centers. Protocols can be developed within an institution to meet the needs of the patient population while minimizing risk and improving outcomes for all patients.

Imaging in the evaluation of the patient with suspected acute coronary syndrome

Over the last decade, major advances have been made in the treatment of acute coronary syndromes (ACSs). However, effective implementation of these treatments requires timely and accurate identification of the high-risk patient among all those presenting to the emergency department (ED) with symptoms suggestive of ACS. The opportunity for improving outcomes is time-dependent, so that early identification of the patient who has true ACS is essential. This necessity further increases the need for rapid triage tools, especially in the current setting of ED and hospital overcrowding that has become the norm in large urban centers.

Efficacy of myocardial contrast echocardiography in the diagnosis and risk stratification of acute coronary syndrome

We examined the hypothesis that myocardial contrast echocardiography (MCE) is superior to conventional electrocardiographic, echocardiographic, and troponin I criteria for the diagnosis of acute coronary syndrome. We prospectively enrolled 114 consecutive patients (60+/-10 years of age, 73 men) who presented to the emergency room with chest pain on exertion and at rest. Exclusion criteria included an age<40 years, presence of Q wave or ST-segment elevation, and a poor echocardiographic window. Echocardiography and MCE were performed to assess regional wall motion abnormalities (RWMAs) and myocardial perfusion defects by using continuous infusion of perfluorocarbon-exposed sonicated dextrose albumin. Acute coronary syndrome was confirmed in 87 patients. There were no deaths; 46 patients had acute myocardial infarction, and 41 patients required urgent revascularization. On multiple logistic regression analysis, myocardial perfusion defect (odd ratio 87, p<0.001) was the only independent variable for diagnosing acute coronary syndrome. Myocardial perfusion defect (odd ratio 21, p=0.001) and troponin I levels (odd ratio 3, p=0.009) were independent predictors for acute myocardial infarction. The sensitivity of myocardial perfusion defect for diagnosing acute coronary syndrome was 77%, which is significantly higher than the sensitivities of ST change, troponin I increase, and RWMA (28%, 34%, and 49%, respectively), with similar specificities of 85% to 96%. In conclusion, MCE is more sensitive than the currently used electrocardiographic and troponin I criteria, and evaluation of myocardial perfusion defect by MCE complements RWMA analysis by conventional echocardiography for accurate diagnosis of acute coronary syndrome.

Chest Pain Units: Management of Special Populations

Chest pain units provide an important alternative to traditional hospital admission for patients who present to the emergency department with symptoms compatible with acute coronary syndrome and a normal or inconclusive initial evaluation. Although patient subgroups such as women, diabetics, those with established coronary artery disease,and those with symptoms related to stimulant use present unique challenges,management in a chest pain unit appears to be appropriate in these populations. Judicious application of accelerated diagnostic protocols and current testing methods can promote safe, accurate, and cost-effective risk stratification of special populations to identify patients who can be safely discharged and patients who require hospital admission for further evaluation.

Diagnostic Accuracy and Prognostic Value of Dobutamine Stress Myocardial Contrast Echocardiography in Patients with Suspected Acute Coronary Syndromes

BACKGROUND

Both early stress testing and cardiac troponin I (cTnI) measurements are useful in assessing the prognosis of patients with acute coronary syndrome (ACS). We sought to determine the accuracy and prognostic value of wall motion analysis (WMA) and myocardial perfusion analysis (MPA) with real-time myocardial contrast echocardiography (RTMCE) during dobutamine stress in this patient population.

METHODS

We performed dobutamine stress RTMCE to assess perfusion in 158 consecutive patients (mean age: 61 +/- 13 years) with chest pain and possible ACS. Of these, 119 had normal cTnI, while 39 had isolated elevations of cTnI (range: 0.5-9.0 ng/ml). Quantitative angiography was performed within 1 month of RTMCE in 61 patients. Patients were followed for 16 months (range: 6-46 months). Cardiac events included death, nonfatal myocardial infarction, recurrent unstable angina, or need for urgent revascularization.

RESULTS

The sensitivity, specificity, and accuracy of MPA for detecting a >50% coronary stenosis were 92%, 77%, and 88%, respectively, while they were 62%, 85%, and 67% for WMA. Three-year event-free survival was 87% in patients with negative WMA and MPA, 49% in those with positive WMA and MPA, and 51% in patients with negative WMA but positive MPA. Age-adjusted multivariate analysis demonstrated that the only independent predictors of cardiac events were a positive MPA (hazard ratio = 3.23; 95% CI = 1.23-8.49) and male sex (hazard ratio = 3.29; 95% CI = 1.21-8.97).

CONCLUSIONS

In patients suspected of having an ACS, RTMCE improved the accuracy of dobutamine stress echocardiography for detecting coronary artery disease, and was an independent predictor of outcome.

Assessment of patients with low-risk chest pain in the emergency department: Head-to-head comparison of exercise stress echocardiography and exercise myocardial SPECT

OBJECTIVES

The aim of the study was to compare head-to-head the performance of exercise tolerance test-stress echocardiography (ex-Echo) and exercise stress-perfusion nuclear imaging (exercise-single-photon emission computed tomography [ex-SPECT]) for the diagnosis of coronary artery disease (CAD) in patients evaluated at the chest pain unit with delay from chest pain (CP) onset.

BACKGROUND

As an early triage strategy for CAD in emergency medicine, ex-Echo could have the advantage of widespread availability and low costs.

METHODS

In the years 2000-2002, 503 consecutive patients (mean age 60 years) with recent (<24 hours) CP and nonischemic electrocardiogram (ECG), in whom CAD remained undiagnosed after first line 6-hour work-up including serum markers of myocardial injury and resting echocardiogram, underwent ex-Echo and ex-SPECT within 24 hours. Patients with (+)ex-Echo or (+)ex-SPECT or (+)ex-ECG or abnormal troponin I were referred to coronary angiography; otherwise, they were discharged and followed up. End points were coronary stenosis > or =50% and cardiovascular events at 6-month follow-up.

RESULTS

Ninety-nine patients (20%) had (+)ex-Echo and 121 (24%) (+)ex-SPECT; CAD was diagnosed in 81% and 67%, respectively; positive tests were concordant in 69%. In negative ex-Echo and ex-SPECT, final evidence of CAD emerged in 14 and 13, respectively. Ex-Echo demonstrated higher accuracy than ex-SPECT (93% +/- 1% vs 89% +/- 1%), optimal specificity (95% +/- 5% vs 90% +/- 5%), and positive predictive value (81% +/- 4% vs 67% +/- 4%); moreover, in the case of (-)ex-ECG, observed effective likelihood ratio indicates a (+)synergy between ex-ECG and ex-Echo.

CONCLUSIONS

Ex-Echo can be an effective diagnostic strategy in the early triage of CP patients, improving diagnosis in case of (-)ex-ECG and reducing unnecessary angiography number. Its drawback is represented by the 5% of missed diagnosis.

Efficacy of Multislice Computed Tomography for the Detection of Acute Coronary Syndrome in the Emergency Department

BACKGROUND

The diagnosis of acute coronary syndrome (ACS), especially non-ST-elevation myocardial infarction and unstable angina in the emergency department (ED) still remains a challenge. Multislice computed tomography (MSCT) allows assessment of not only coronary artery stenoses and occlusions, but also assessment of coronary artery plaques and myocardial perfusion status.

METHODS AND RESULTS

MSCT was performed in 31 patients who were admitted to the ED because of chest pain persisting at least 30 min and non-diagnostic ECG changes and normal serum enzyme concentrations. Using MSCT, ACS was defined by coronary artery stenosis > or = 75% accompanied by computed tomography (CT)-low-density plaques, and/or by the presence of myocardial perfusion defects. ACS was confirmed by coronary stenosis > or = 75% by coronary angiography and/or subsequent elevation of troponin I concentration. In total, 22 patients were diagnosed as having ACS. MSCT detected stenoses with CT-low-density plaques in 21 and non-transmural myocardial perfusion defect in 3 patients. There was 1 false-positive and 1 false-negative result. The sensitivity and specificity of MSCT to identify ACS was 95.5% and 88.9%, respectively.

CONCLUSION

MSCT provides diagnostic operating characteristics suitable for triage of patients with ACS in the ED.

B-type natriuretic peptide: a novel early blood marker of acute myocardial infarction in patients with chest pain and no ST-segment elevation

AIMS

This study was undertaken to determine the diagnostic value of admission B-type natriuretic peptide (BNP) for acute myocardial infarction (AMI) in patients with acute chest pain and no ST-segment elevation.

METHODS AND RESULTS

A prospective study with 631 consecutive patients was conducted in the emergency department. Non-ST elevation AMI was present in 72 patients and their median admission BNP level was significantly higher than in unstable angina and non-acute coronary syndrome patients. Sensitivity of admission BNP for AMI (cut-off value of 100 pg/mL) was significantly higher than creatine kinase-MB (CKMB) and troponin-I on admission (70.8 vs. 45.8 vs. 50.7%, respectively, P<0.0001) and specificity was 68.9%. Simultaneous use of these markers significantly improved sensitivity to 87.3% and the negative predictive value to 97.3%. In multiple logistic regression analysis, admission BNP was a significant independent predictor of AMI, even when CKMB and troponin-I were present in the model.

CONCLUSION

BNP is a useful adjunct to standard cardiac markers in patients presenting to the emergency department with chest pain and no ST-segment elevation, particularly if initial CKMB and/or troponin-I are non-diagnostic.

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.

Improving care in patients with acute coronary syndromes: the Erlanger quality improvement initiative

Quality improvement (QI) in emergency department (ED) patients with acute coronary syndromes (ACS) is a complex and dynamic phenomenon. ED physicians are faced with the challenge of multitasking a variety of patient complaints. This chaotic environment frequently hampers the ED physician's ability to properly evaluate and treat chest pain patients. Just as an airplane pilot would never take off without performing the comprehensive preflight operational checklist, the ED physician should have a standardized protocol for the evaluation and treatment of chest pain patients. In this report, we describe Erlanger Medical Center's 10-year QI initiative in developing a successful chest pain protocol for the rapid evaluation and treatment of patients with suspected ACS. Our initiative resulted from a collaborative effort among emergency physicians, cardiologists, nuclear radiologists, nursing staff, and administration. The systematic step-wise approach we utilized at our institution consisted of identification of the problem, development of standardized protocols, hospital-based QI initiatives, and continuation of QI efforts through national initiatives. Through this "building of bridges" among physicians, nursing, and administration, we hope that other institutions will modify our protocols to assist them in the development of their own successful QI program for improving the evaluation, treatment, and disposition of patients with suspected ACS.