Clinical value of acute rest technetium-99m tetrofosmin tomographic myocardial perfusion imaging in patients with acute chest pain and nondiagnostic electrocardiograms

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.

Value of rest 18F-FDG myocardial imaging in the diagnosis of obstructive coronary artery disease in Chinese patients with suspected unstable angina: A prospective real-world clinical study

BACKGROUND

This study aimed to determine the clinical value of rest 18F-FDG imaging in Chinese patients with non-acute chest pain, normal ECG, negative troponin, and suspected UA.

METHODS

136 patients were prospectively included and underwent rest 18F-FDG PET imaging and coronary arteriography within 1 week.

RESULTS

Obstructive CAD was diagnosed in 71 patients, and stenosis ≥ 70% was confirmed in 130 vascular territories. At patients and vascular level, rest 18F-FDG imaging showed sensitivity of 62.0%, 47.7%, specificity of 92.3%, 94.2%, accuracy of 76.5%, 79.4%, PPV of 89.8% and 79.5%, and NPV of 69.0% and 79.4%. The AUCs were 0.771 and 0.710. Of 71 patients with obstructive CAD, rest 18F-FDG imaging showed sensitivity of 47.7% and 58.8%, specificity of 91.6% and 91.2%, accuracy of 64.8% and 80.4%, PPV of 89.9% and 76.9% and NPV of 52.8% and 81.6% in all vascular level and single-vessel disease. In patients with two- or three-vessel disease, rest 18F-FDG imaging had a diagnostic sensitivity, specificity, accuracy, PPV, and NPV of 43.8%, 93.3%, 50.5%, 97.7%, and 20.6%. The AUCs were 0.696, 0.750, and 0.685.

CONCLUSION

Rest 18F-FDG imaging performed certain overall diagnostic efficiency for obstructive CAD in Chinese patients with suspected UA, especially the excellent high PPV in identifying culprit ischemic territory in patients with multivessel disease.

Coronary Computed Tomography Angiography for Evaluation of Chest Pain in the Emergency Department

Coronary computed tomography angiography has emerged as an important diagnostic modality for evaluation of acute chest pain in the emergency department for patients at low to intermediate risk for acute coronary syndromes. Several clinical trials have shown excellent negative predictive value of coronary computed tomography angiography to detect obstructive coronary artery disease. Cardiac biomarkers such as troponins and creatine kinase MB, along with history, electrocardiogram, age, risk factors, troponin score, and Thrombolysis in Myocardial Infarction score should be used in conjunction with coronary computed tomography angiography for safe and rapid discharge of patients from the emergency department. Coronary computed tomography angiography along with high-sensitivity troponin assays could be effective for rapid evaluation of acute chest pain in the emergency department, but high-sensitivity troponins are not always available. Emergency department physicians are not quite comfortable making clinical decisions, especially if the coronary stenosis is in the range of 50% to 70%. In these cases, further evaluation with functional testing, such as nuclear stress testing or stress echocardiogram, is a common approach in many centers; however, newer methods such as fractional flow reserve computed tomography could be safely incorporated in coronary computed tomography angiography to help with clinical decision-making in these scenarios.

Major adverse cardiac event rates in moderate-risk patients: Does prior coronary disease matter?

BACKGROUND

Despite negative troponins and nonischemic electrocardiograms (ECGs), patients at moderate risk for acute coronary syndrome (ACS) are frequently admitted. The objective of this study was to describe the major adverse cardiac event (MACE) rate in moderate-risk patients and how it differs based on history of coronary artery disease (CAD).

METHODS

A secondary analysis of the HEART Pathway implementation study was conducted. This prospective interrupted time-series study accrued adults with possible ACS from three sites (November 2013-January 2016). This analysis excluded low-risk patients determined by emergency providers' HEART Pathway assessments. Non-low-risk patients were further classified as high risk, based on elevated troponin measures or ischemic ECG findings or as moderate risk, based on HEAR score ≥ 4, negative troponin measures, and a nonischemic ECG. Moderate-risk patients were then stratified by the presence or absence of prior CAD (MI, revascularization, or ≥70% coronary stenosis). MACE (death, myocardial infarction, or revascularization) at 30 days was determined from health records, insurance claims, and death index data. MACE rates were compared among groups using a chi-square test and likelihood ratios (LRs) were calculated.

RESULTS

Among 4,550 patients with HEART Pathway assessments, 24.8% (1,130/4,550) were high risk and 37.7% (1715/4550) were moderate risk. MACE at 30 days occurred in 3.1% (53/1,715; 95% confidence interval [CI] = 2.3% to 4.0%) of moderate-risk patients. Among moderate-risk patients, MACE occurred in 7.1% (36/508, 95% CI = 5.1% to 9.8%) of patients with known CAD versus 1.4% (17/1,207, 95% CI = 0.9% to 2.3%) in patients without known prior CAD (p < 0.0001). The negative LR for 30-day MACE among moderate-risk patients without prior CAD was 0.08 (95% CI = 0.05 to 0.12).

CONCLUSION

MACE rates at 30 days were low among moderate-risk patients but were significantly higher among those with prior CAD.

The role of coronary CT angiography for acute chest pain in the era of high-sensitivity troponins

Accurate and efficient diagnostic triage for acute chest pain (ACP) remains one of the most challenging problems in the emergency department (ED). While the proportion of patients that present with myocardial infarction (MI), aortic dissection, or pulmonary embolism is relatively low, a missed diagnosis can be life threatening. Coronary computed tomography angiography (CCTA) has developed into a robust diagnostic tool in the triage of ACP over the past decade, with several trials showing that it can reliably identify patients at low risk of major adverse cardiovascular events, shorten the length of stay in the ED, and reduce cost associated with the triage of patients with undifferentiated chest pain. Recently, however, high-sensitivity troponin assays have been increasingly incorporated as a rapid and efficient diagnostic test in the triage of ACP due to their higher sensitivity and negative predictive value of myocardial infarction. As more EDs adopt high-sensitivity troponin assays into routine clinical practice, the role of CCTA will likely change. In this review, we provide an overview of CCTA and high-sensitivity troponins for evaluation of patients with suspected ACS in the ED. Moreover, we discuss the changing role of CCTA in the era of high-sensitivity troponins.

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.

Acute chest pain in the high-sensitivity cardiac troponin era: A changing role for noninvasive imaging?

Management of patients with acute chest pain remains challenging. Cardiac biomarker testing reduces the likelihood of erroneously discharging patients with acute myocardial infarction (AMI). Despite normal contemporary troponins, physicians have still been reluctant to discharge patients without additional testing. Nowadays, the extremely high negative predictive value of current high-sensitivity cardiac troponin (hs-cTn) assays challenges this need. However, the decreased specificity of hs-cTn assays to diagnose AMI poses a new problem as noncoronary diseases (eg, pulmonary embolism, myocarditis, cardiomyopathies, hypertension, renal failure, etc) may also cause elevated hs-cTn levels. Subjecting patients with noncoronary diseases to unnecessary pharmacological therapy or invasive procedures must be prevented. Attempts to improve the positive predictive value to diagnose AMI by defining higher initial cutoff values or dynamic changes over time inherently lower the sensitivity of troponin assays. In this review, we anticipate a potential changing role of noninvasive imaging from ruling out myocardial disease when troponin values are normal toward characterizing myocardial disease when hs-cTn values are (mildly) abnormal.

Efficiency and safety of coronary CT angiography compared to standard care in the evaluation of patients with acute chest pain: a Canadian study

The optimal assessment of patients with chest pain and possible acute coronary syndrome (ACS) remains a diagnostic dilemma for emergency physicians. Cardiac computed tomographic angiography (CCTA) may identify patients who can be safely discharged home from the emergency department (ED). The objective of the study was to compare the efficiency and safety of CCTA to standard care in patients presenting to the ED with low- to intermediate-risk chest pain. This was a single-center before-after study enrolling ED patients with chest pain and low to intermediate risk of ACS, before and after implementing a cardiac CT-based management protocol. The primary outcome was efficiency (time to diagnosis). Secondary outcomes included safety (30-day incidence of major adverse cardiovascular events (MACE)) and length of stay in the ED. We enrolled 258 patients: 130 in the standard care group and 128 in the cardiac CT-based management group. The cardiac CT group had a shorter time to diagnosis of 7.1 h (IQR 5.8-14.0) compared to 532.9 h (IQR 312.8-960.5) for the standard care group (p < 0.0001) but had a longer length of stay in the ED of 7.9 h (IQR 6.5-10.8) versus 5.5 h (IQR 3.9-7.7) (p < 0.0001). The MACE rate was 1.6 % in the standard care group and 0 % in the cardiac CT group. In conclusion, a cardiac CT-based management strategy to rule out ACS in ED patients with low- to intermediate-risk chest pain was safe and led to a shorter time to diagnosis but increased length of stay in the ED.

Noninvasive cardiac imaging in suspected acute coronary syndrome

Noninvasive cardiac imaging has an important role in the assessment of patients with acute-onset chest pain. In patients with suspected acute coronary syndrome (ACS), cardiac imaging offers incremental value over routine clinical assessment, the electrocardiogram, and blood biomarkers of myocardial injury, to confirm or refute the diagnosis of coronary artery disease and to assess future cardiovascular risk. This Review covers the current guidelines and clinical use of the common noninvasive imaging techniques, including echocardiography and stress echocardiography, computed tomography coronary angiography, myocardial perfusion scintigraphy, positron emission tomography, and cardiovascular magnetic resonance imaging, in patients with suspected ACS, and provides an update on the developments in noninvasive imaging techniques in the past 5 years.

Adherence to an Accelerated Diagnostic Protocol for Chest Pain: Secondary Analysis of the HEART Pathway Randomized Trial

OBJECTIVES

Accelerated diagnostic protocols (ADPs), such as the HEART Pathway, are gaining popularity in emergency departments (EDs) as tools used to risk stratify patients with acute chest pain. However, provider nonadherence may threaten the safety and effectiveness of ADPs. The objective of this study was to determine the frequency and impact of ADP nonadherence.

METHODS

A secondary analysis of participants enrolled in the HEART Pathway RCT was conducted. This trial enrolled 282 adult ED patients with symptoms concerning for acute coronary syndrome without ST-elevation on electrocardiogram. Patients randomized to the HEART Pathway (N = 141) were included in this analysis. Outcomes included index visit disposition, nonadherence, and major adverse cardiac events (MACEs) at 30 days. MACE was defined as death, myocardial infarction, or revascularization. Nonadherence was defined as: 1) undertesting-discharging a high-risk patient from the ED without objective testing (stress testing or coronary angiography) or 2) overtesting-admitting or obtaining objective testing on a low-risk patient.

RESULTS

Nonadherence to the HEART Pathway occurred in 28 of 141 patients (20%, 95% confidence interval [CI] = 14% to 27%). Overtesting occurred in 19 of 141 patients (13.5%, 95% CI = 8% to 19%) and undertesting in nine of 141 patients (6%, 95% CI = 3% to 12%). None of these 28 patients suffered MACE. The net effect of nonadherence was 10 additional admissions among patients identified as low-risk and appropriate for early discharge (absolute decrease in discharge rate of 7%, 95% CI = 3% to 13%).

CONCLUSIONS

Real-time use of the HEART Pathway resulted in a nonadherence rate of 20%, mostly due to overtesting. None of these patients had MACE within 30 days. Nonadherence decreased the discharge rate, attenuating the HEART Pathway's impact on health care use.

Performance of the 2-hour accelerated diagnostic protocol within the American College of Radiology Imaging Network PA 4005 cohort

OBJECTIVES

The 2-hour accelerated diagnostic protocol (ADAPT) is a decision rule designed to identify emergency department (ED) patients with chest pain for early discharge. Previous studies in the Asia-Pacific region demonstrated high sensitivity (97.9% to 99.7%) for major adverse cardiac events (MACE) at 30 days. The objective of this study was to determine the validity of ADAPT for risk stratification in a cohort of U.S. ED patients with suspected acute coronary syndrome (ACS).

METHODS

A secondary analysis of participants enrolled in the American College of Radiology Imaging Network (ACRIN) PA 4005 trial was conducted. This trial enrolled 1,369 patients at least 30 years old with symptoms suggestive of ACS. All data elements were collected prospectively at the time of enrollment. Each patient was classified as low risk or at risk by ADAPT. Early discharge rate and sensitivity for MACE, defined as cardiac death, myocardial infarction (MI), or coronary revascularization at 30 days, were calculated.

RESULTS

Of 1,140 patients with complete biomarker data, MACE occurred in 31 patients (2.7%). Among 551 of the 1,140 (48.3%, 95% confidence interval [CI] = 45.4% to 51.3%), ADAPT identified for early discharge; five of the 551 (0.9%, 95% CI = 0.3% to 2.1%) had MACE at 30 days. ADAPT was 83.9% (95% CI = 66.3% to 94.5%) sensitive, identifying 26 of 31 patients with MACE. Of the five patients identified for early discharge by ADAPT with MACE, there were no deaths, one patient with MI, and five with revascularizations.

CONCLUSIONS

In this first North American application of the ADAPT strategy, sensitivity for MACE within 30 days was 83.9%. One missed adverse event was a MI, with the remainder representing coronary revascularizations. The effect of missing revascularization events needs further investigation.

The HEART Pathway randomized trial: identifying emergency department patients with acute chest pain for early discharge

BACKGROUND

The HEART Pathway is a decision aid designed to identify emergency department patients with acute chest pain for early discharge. No randomized trials have compared the HEART Pathway with usual care.

METHODS AND RESULTS

Adult emergency department patients with symptoms related to acute coronary syndrome without ST-elevation on ECG (n=282) were randomized to the HEART Pathway or usual care. In the HEART Pathway arm, emergency department providers used the HEART score, a validated decision aid, and troponin measures at 0 and 3 hours to identify patients for early discharge. Usual care was based on American College of Cardiology/American Heart Association guidelines. The primary outcome, objective cardiac testing (stress testing or angiography), and secondary outcomes, index length of stay, early discharge, and major adverse cardiac events (death, myocardial infarction, or coronary revascularization), were assessed at 30 days by phone interview and record review. Participants had a mean age of 53 years, 16% had previous myocardial infarction, and 6% (95% confidence interval, 3.6%-9.5%) had major adverse cardiac events within 30 days of randomization. Compared with usual care, use of the HEART Pathway decreased objective cardiac testing at 30 days by 12.1% (68.8% versus 56.7%; P=0.048) and length of stay by 12 hours (9.9 versus 21.9 hours; P=0.013) and increased early discharges by 21.3% (39.7% versus 18.4%; P<0.001). No patients identified for early discharge had major adverse cardiac events within 30 days.

CONCLUSIONS

The HEART Pathway reduces objective cardiac testing during 30 days, shortens length of stay, and increases early discharges. These important efficiency gains occurred without any patients identified for early discharge suffering MACE at 30 days.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique Identifier: NCT01665521.

Early resting myocardial computed tomography perfusion for the detection of acute coronary syndrome in patients with coronary artery disease

BACKGROUND

Acute rest single-photon emission computed tomography-myocardial perfusion imaging (SPECT-MPI) has high predictive value for acute coronary syndrome (ACS) in emergency department patients. Prior studies have shown excellent agreement between rest/stress computed tomography perfusion (CTP) and SPECT-MPI, but the value of resting CTP (rCTP) in acute chest pain triage remains unclear. We sought to determine the diagnostic accuracy of early rCTP, incremental value beyond obstructive coronary artery disease (CAD; ≥50% stenosis), and compared early rCTP to late stress SPECT-MPI in patients with CAD presenting with suspicion of ACS to the emergency department.

METHODS AND RESULTS

In this prespecified subanalysis of 183 patients (58.1±10.2 years; 33% women), we included patients with any CAD by coronary computed tomography angiography (CCTA) from Rule Out Myocardial Infarction Using Computer-Assisted Tomography I. rCTP was assessed semiquantitatively, blinded to CAD interpretation. Overall, 31 had ACS and 48 had abnormal rCTP. Sensitivity and specificity of rCTP for ACS were 48% (95% confidence interval [CI], 30%-67%) and 78% (95% CI, 71%-85%), respectively. rCTP predicted ACS (adjusted odds ratio, 3.40 [95% CI, 1.37-8.42]; P=0.008) independently of obstructive CAD, and sensitivity for ACS increased from 77% (95% CI, 59%-90%) for obstructive CAD to 90% (95% CI, 74%-98%) with addition of rCTP (P=0.05). In a subgroup undergoing late rest/stress SPECT-MPI (n=81), CCTA/rCTP had noninferior discriminatory value to CCTA/SPECT-MPI (area under the curve, 0.88 versus 0.90; P=0.64) using a noninferiority margin of 10%.

CONCLUSIONS

Early rCTP provides incremental value beyond obstructive CAD to detect ACS. CCTA/rCTP is noninferior to CCTA/SPECT-MPI to discriminate ACS and presents an attractive alternative to triage patients presenting with acute chest pain.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT00990262.

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.

Cost-effectiveness of a novel blood-pool contrast agent in the setting of chest pain evaluation in an emergency department

OBJECTIVE

We evaluated three diagnostic strategies with the objective of comparing the current standard of care for individuals presenting acute chest pain and no history of coronary artery disease (CAD) with a novel diagnostic strategy using an emerging technology (blood-pool contrast agent [BPCA]) to identify the potential benefits and cost reductions.

MATERIALS AND METHODS

A decision analytic model of diagnostic strategies and outcomes using a BPCA and a conventional agent for CT angiography (CTA) in patients with acute chest pain was built. The model was used to evaluate three diagnostic strategies: CTA using a BPCA followed by invasive coronary angiography (ICA), CTA using a conventional agent followed by ICA, and ICA alone.

RESULTS

The use of the two CTA-based triage tests before ICA in a population with a CAD prevalence of less than 47% was predicted to be more cost-effective than ICA alone. Using the base-case values and a cost premium for BPCA over the conventional CT agent (cost of BPCA ≈ 5× that of a conventional agent) showed that CTA with a BPCA before ICA resulted in the most cost-effective strategy; the other strategies were ruled out by simple dominance. The model strongly depends on the rates of complications from the diagnostic tests included in the model. In a population with an elevated risk of contrast-induced nephropathy (CIN), a significant premium cost per BPCA dose still resulted in the alternative whereby CTA using BPCA was more cost-effective than CTA using a conventional agent. A similar effect was observed for potential complications resulting from the BPCA injection. Conversely, in the presence of a similar complication rate from BPCA, the diagnostic strategy of CTA using a conventional agent would be the optimal alternative.

CONCLUSION

BPCAs could have a significant impact in the diagnosis of acute chest pain, in particular for populations with high incidences of CIN. In addition, a BPCA strategy could garner further savings if currently excluded phenomena including renal disease and incidental findings were included in the decision model.

Role of imaging for acute chest pain syndromes

Acute chest pain suggestive of ischemic cardiac origin, with a normal or nondiagnostic electrocardiogram and negative initial cardiac markers for myocardial necrosis represent a significant diagnostic dilemma for clinicians. Multiple imaging modalities play a pivotal role in early diagnosis and safe discharge of these patients. In this review, we compare the current imaging modalities available for these patients including their diagnostic accuracy, feasibility, and cost effectiveness. Acute rest myocardial perfusion imaging significantly improves the clinical outcome in these patients and reduces the overall cost when incorporated into the decision making pathway. The choice of imaging modality recommended should be based on local institutional expertise and the overall clinical presentation. The imaging modality with high diagnostic accuracy and negative predictive value will provide for precise risk stratification which is important to clinical decision making, including patients who require admission to the hospital and those who can be safely discharged.

Diagnostic performance of resting CT myocardial perfusion in patients with possible acute coronary syndrome

OBJECTIVE

Coronary CT angiography has high sensitivity, but modest specificity, to detect acute coronary syndrome. We studied whether adding resting CT myocardial perfusion imaging improved the detection of acute coronary syndrome.

SUBJECTS AND METHODS

Patients with low-to-intermediate cardiac risk presenting with possible acute coronary syndrome received both the standard of care evaluation and a research thoracic 64-MDCT examination. Patients with an obstructive (> 50%) stenosis or a nonevaluable coronary segment on CT were diagnosed with possible acute coronary syndrome. CT perfusion was determined by applying gray and color Hounsfield unit maps to resting CT angiography images. Adjudicated patient diagnoses were based on the standard of care and 3-month follow-up. Patient-level diagnostic performance for acute coronary syndrome was calculated for coronary CT, CT perfusion, and combined techniques.

RESULTS

A total of 105 patients were enrolled. Of the nine (9%) patients with acute coronary syndrome, all had obstructive CT stenoses but only three had abnormal CT perfusion. CT perfusion was normal in all other patients. To detect acute coronary syndrome, CT angiography had 100% sensitivity, 89% specificity, and a positive predictive value of 45%. For CT perfusion, specificity and positive predictive value were each 100%, and sensitivity was 33%. Combined cardiac CT and CT perfusion had similar specificity but a higher positive predictive value (100%) than did CT angiography.

CONCLUSION

Resting CT perfusion using CT angiographic images may have high specificity and may improve CT positive predictive value for acute coronary syndrome without added radiation and contrast. However, normal resting CT perfusion cannot exclude acute coronary syndrome.

Stress myocardial perfusion imaging in the emergency department--new techniques for speed and diagnostic accuracy

Emergency room evaluations of patients presenting with chest pain continue to rise, and these evaluations which often include cardiac imaging, are an increasing area of resource utilization in the current health system. Myocardial perfusion imaging from the emergency department remains a vital component of the diagnosis or exclusion of coronary artery disease as the etiology of chest pain. Recent advances in camera technology, and changes to the imaging protocols have allowed MPI to become a more efficient way of providing this diagnostic information. Compared with conventional SPECT, new high-efficiency CZT cameras provide a 3-5 fold increase in photon sensitivity, 1.65-fold improvement in energy resolution and a 1.7-2.5-fold increase in spatial resolution. With stress-only imaging, rest images are eliminated if stress images are normal, as they provide no additional prognostic or diagnostic value and cancelling the rest images would shorten the length of the test which is of particular importance to the ED population. The rapid but accurate triage of patients in an ED CPU is essential to their care, and stress-only imaging and new CZT cameras allow for shorter test time, lower radiation doses and lower costs while demonstrating good clinical outcomes. These changes to nuclear stress testing can allow for faster throughput of patients through the emergency department while providing a safe and efficient evaluation of chest pain.

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.

Performance of rest myocardial perfusion imaging in the management of acute chest pain in the emergency room in developing nations (PREMIER trial)

BACKGROUND

Rest myocardial perfusion imaging (MPI) is effective in managing patients with acute chest pain in developed countries. We aimed to define the role and feasibility of rest MPI in low-to-middle income countries.

METHODS AND RESULTS

Low-to-intermediate risk patients (n = 356) presenting with chest pain to ten centers in eight developing countries were injected with a Tc-99m-based tracer, and standard imaging was performed. The primary outcome was a composite of death, non-fatal myocardial infarction (MI), recurrent angina, and coronary revascularization at 30 days. Sixty-nine patients had a positive MPI (19.4%), and 52 patients (14.6%) had a primary outcome event. An abnormal rest-MPI result was the only variable which independently predicted the primary outcome [adjusted odds ratio (OR) 8.19, 95% confidence interval 4.10-16.40, P = .0001]. The association of MPI result and the primary outcome was stronger (adjusted OR 17.35) when only the patients injected during pain were considered. Rest-MPI had a negative predictive value of 92.7% for the primary outcome, improving to 99.3% for the hard event composite of death or MI.

CONCLUSIONS

Our study demonstrates that rest-MPI is a reliable test for ruling out MI when applied to patients in developing countries.

Coronary CT and the coronary calcium score, the future of ED risk stratification?

Accurate and efficient evaluation of acute chest pain remains clinically challenging because traditional diagnostic modalities have many limitations. Recent improvement in non-invasive imaging technologies could potentially improve both diagnostic efficiency and clinical outcomes of patients with acute chest pain while reducing unnecessary hospitalizations. However, there is still controversy regarding much of the evidence for these technologies. This article reviews the role of coronary artery calcium score and the coronary computed tomography in the assessment of individual coronary risk and their usefulness in the emergency department in facilitating appropriate disposition decisions. The evidence base and clinical applications for both techniques are also described, together with cost- effectiveness and radiation exposure considerations.

Cardiac CT in the emergency department

Current triage strategies are not effective in correctly identifying patients suffering from acute coronary syndrome (ACS). The diagnostic workup of patients presenting with acute chest pain continues to represent a major challenge for emergency department (ED) personnel. This statement holds especially true for patients with a low to intermediate likelihood for ACS. Taking current concepts for the diagnosis and management of patients presenting with acute chest pain to the ED into account, this article discusses the evidence and potential role of coronary computed tomography angiography to improve management of patients with possible ACS.

Prognostic value of real time dobutamine stress myocardial contrast echocardiography in patients with chest pain syndrome

The aims of this study were (1) to evaluate the prognostic value of negative wall motion (WM) and myocardial perfusion during contrast-dobutamine stress echocardiography (DSE), (2) to determine whether WM-myocardial contrast echocardiography (MCE) had incremental prognostic value over just WM during DSE in patients with chest pain in the emergency room (ER), and (3) to compare the prognostic value of negative DSE-WM, and DSE-WM-MCE to nuclear-myocardial perfusion imaging (N-MPI) in a similar patient population over the same time period. We retrospectively studied 569 patients with real time contrast DSE, and 147 patients underwent N-MPI for evaluation of chest pain. Follow-up for cardiac events was obtained between 12 and 25 months. The cumulative cardiac event-free survival was 94.5% in negative DSE-WM, 97.1% in negative DSE-WM-MCE and 96.7% in negative N-MPI group. Cardiac event-free survival of the negative DSE-WM-MCE group was significantly higher than the DSE-WM group (log rank P < 0.01), and similar in the DSE-WM-MCE group compared to the N-MPI group. Combined WM and perfusion during DSE was the strongest independent predictor for cardiac events. The negative predictive power of DSE-WM-MCE is superior to that of just negative DSE-WM and is comparable to that of N-MPI. Myocardial perfusion and WM analysis during DSE provide independent information for predicting cardiac events in patients with chest pain syndrome in the ER.

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.

Non-invasive imaging in acute chest pain syndromes

This review has the purpose of informing the reader about the current use of imaging techniques in patients presenting with acute chest pain to the emergency department. We will focus on three aspects of managing the patient with acute chest pain: Imaging to increase the number of correct diagnoses in the acute situation; Imaging to rule out other than coronary causes of chest pain; Use of imaging for risk stratification once myocardial infarction has been ruled out in the CPU. Special emphasis is given to how these management aspects are discussed in current guidelines on the management of patients with acute chest pain or acute coronary syndrome.

The CT-STAT (Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patients to Treatment) trial

OBJECTIVES

The purpose of this study was to compare the efficiency, cost, and safety of a diagnostic strategy employing early coronary computed tomographic angiography (CCTA) to a strategy employing rest-stress myocardial perfusion imaging (MPI) in the evaluation of acute low-risk chest pain.

BACKGROUND

In the United States, >8 million patients require emergency department evaluation for acute chest pain annually at an estimated diagnostic cost of >$10 billion.

METHODS

This multicenter, randomized clinical trial in 16 emergency departments ran between June 2007 and November 2008. Patients were randomly allocated to CCTA (n = 361) or MPI (n = 338) as the index noninvasive test. The primary outcome was time to diagnosis; the secondary outcomes were emergency department costs of care and safety, defined as freedom from major adverse cardiac events in patients with normal index tests, including 6-month follow-up.

RESULTS

The CCTA resulted in a 54% reduction in time to diagnosis compared with MPI (median 2.9 h [25th to 75th percentile: 2.1 to 4.0 h] vs. 6.3 h [25th to 75th percentile: 4.2 to 19.0 h], p < 0.0001). Costs of care were 38% lower compared with standard (median $2,137 [25th to 75th percentile: $1,660 to $3,077] vs. $3,458 [25th to 75th percentile: $2,900 to $4,297], p < 0.0001). The diagnostic strategies had no difference in major adverse cardiac events after normal index testing (0.8% in the CCTA arm vs. 0.4% in the MPI arm, p = 0.29).

CONCLUSIONS

In emergency department acute, low-risk chest pain patients, the use of CCTA results in more rapid and cost-efficient safe diagnosis than rest-stress MPI. Further studies comparing CCTA to other diagnostic strategies are needed to optimize evaluation of specific patient subsets. (Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patients to Treatment [CT-STAT]; NCT00468325).

Strain-encoded cardiac magnetic resonance during high-dose dobutamine stress testing for the estimation of cardiac outcomes: comparison to clinical parameters and conventional wall motion readings

OBJECTIVES

The purpose of this study was to determine the prognostic value of strain-encoded magnetic resonance imaging (SENC) during high-dose dobutamine stress cardiac magnetic resonance imaging (DS-MRI) compared with conventional wall motion readings.

BACKGROUND

Detection of inducible ischemia by DS-MRI on the basis of assessing cine images is subjective and depends on the experience of the readers, which may influence not only the diagnostic classification but also the risk stratification of patients with ischemic heart disease.

METHODS

In all, 320 consecutive patients with suspected or known coronary artery disease underwent DS-MRI, using a standard protocol in a 1.5T MR scanner. Wall motion abnormalities (WMA) and myocardial strain were assessed at baseline and during stress, and outcome data including cardiac deaths, nonfatal myocardial infarctions ("hard events"), and revascularization procedures performed >90 days after the MR scans were collected.

RESULTS

Thirty-five hard events occurred during a 28 ± 9 month follow-up period, including 10 cardiac deaths and 25 nonfatal myocardial infarctions, and 32 patients underwent coronary revascularization. Using a series of Cox proportional-hazards models, both resting and inducible WMA offered incremental information for the assessment of hard cardiac events compared to clinical variables (chi-square = 13.0 for clinical vs. chi-square = 26.1 by adding resting WMA, p < 0.001, vs. chi-square = 39.3 by adding inducible WMA, p < 0.001). Adding visual SENC or quantitative strain rate reserve to this model further improved the prediction of outcome (chi-square = 50.7 vs. chi-square = 52.5, p < 0.001 for both). In a subset of patients (n = 175) who underwent coronary angiography, SENC yielded significantly higher sensitivity for coronary artery disease detection (96% vs. 84%, p < 0.02), whereas specificity and accuracy were not significantly different (88% vs. 94% and 93% vs. 88%, p = NS for both).

CONCLUSIONS

Strain-encoded MRI aids the accurate identification of patients at high risk for future cardiac events and revascularization procedures, beyond the assessment of conventional atherogenic risk factors and resting or inducible WMA on cine images. (Strain-Encoded Cardiac Magnetic Resonance Imaging as an Adjunct for Dobutamine Stress Testing; NCT00758654).

Cost-effectiveness of coronary computed tomography and cardiac stress imaging in the emergency department: a decision analytic model comparing diagnostic strategies for chest pain in patients at low risk of acute coronary syndromes

Emergency department presentations with chest pain are expensive and often unrelated to coronary artery disease (CAD). Coronary computed tomographic angiography (CTA) may allow earlier discharge of low-risk patients, resulting in cost savings. We modeled clinical and economic outcomes of diagnostic strategies in patients with chest pain and at low risk of CAD: exercise electrocardiography (ECG), stress single-photon emission computed tomography (SPECT), stress echocardiography, and a CTA strategy comprising an initial CTA scan with confirmatory SPECT for indeterminate results. Our results suggest that a 2-step diagnostic strategy of CTA with SPECT for intermediate scans is likely to be less costly and more effective for the diagnosis of a patient group at low risk of CAD and a prevalence of 2% to 30%. The CTA strategies were cost saving (lower costs, higher quality-adjusted life-years) compared with stress ECG, echocardiography, and SPECT. Confirming intermediate/indeterminate CTA scans with SPECT results in cost savings and quality-adjusted life-year gains due to reduced hospitalization of patients who returned false-positive initial CTA test. However, CTA may be associated with a higher event rate in negative patients than SPECT, and the diagnostic and prognostic information for the use of CTA in the emergency department is evolving. Large comparative, randomized, controlled trials of the different diagnostic strategies are needed to compare the long-term costs and consequences of each strategy in a population of defined low-risk patients in the emergency department.

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."

Detection of intracoronary thrombus by magnetic resonance imaging in patients with acute myocardial infarction

BACKGROUND

Persistent intracoronary thrombus after plaque rupture is associated with an increased risk of subsequent myocardial infarction and mortality. Coronary thrombus is usually visualized invasively by x-ray coronary angiography. Non-contrast-enhanced T1-weighted magnetic resonance (MR) imaging has been useful for direct imaging of carotid thrombus and intraplaque hemorrhage by taking advantage of the short T1 of methemoglobin present in acute thrombus and intraplaque hemorrhage. The aim of this study was to investigate the use of non-contrast-enhanced MR for direct thrombus imaging (MRDTI) in patients with acute myocardial infarction.

METHODS AND RESULTS

Eighteen patients (14 men; age, 61±9 years) underwent MRDTI within 24 to 72 hours of presenting with an acute coronary syndrome before invasive x-ray coronary angiography; MRDTI was performed with a T1-weighted, 3-dimensional, inversion-recovery black-blood gradient-echo sequence without contrast administration. Ten patients were found to have intracoronary thrombus on x-ray coronary angiography (left anterior descending, 4; left circumflex, 2; right coronary artery, 4; and right coronary artery-posterior descending artery, 1), and 8 had no visible thrombus. We found that MRDTI correctly identified thrombus in 9 of 10 patients (sensitivity, 91%; posterior descending artery thrombus not detected) and correctly classified the control group in 7 of 8 patients without thrombus formation (specificity, 88%). The contrast-to-noise ratio was significantly greater in coronary segments containing thrombus (n=10) compared with those without visible thrombus (n=131; mean contrast-to-noise ratio, 15.9 versus 2.6; P<0.001).

CONCLUSION

Use of MRDTI allows selective visualization of coronary thrombus in a patient population with a high probability of intracoronary thrombosis.

Integrated SPECT/CT for assessment of haemodynamically significant coronary artery lesions in patients with acute coronary syndrome

PURPOSE

Early risk stratification in patients with non-ST elevation acute coronary syndromes (NSTE-ACS) is important since the benefit from more aggressive and costly treatment strategies is proportional to the risk of adverse clinical events. In the present study we assessed whether hybrid single photon emission computed tomography (SPECT)/coronary computed tomography angiography (CCTA) technology could be an appropriate tool in stratifying patients with NSTE-ACS.

METHODS

SPECT/CCTA was performed in 90 consecutive patients with NSTE-ACS. The Thrombolysis in Myocardial Infarction risk score (TIMI-RS) was used to classify patients as low- or high-risk. Imaging was performed using SPECT/CCTA to identify haemodynamically significant lesions defined as >50% stenosis on CCTA with a reversible perfusion defect on SPECT in the corresponding territory.

RESULTS

CCTA demonstrated at least one lesion with >50% stenosis in 35 of 40 high-risk patients (87%) as compared to 14 of 50 low-risk patients (35%; TIMI-RS<3; p<.0001). Of the 40 high-risk and 50 (16%) low-risk TIMI-RS patients, 16 (40%) and 8 (16%), respectively, had haemodynamically significant lesions (p=0.01). Patients defined as high-risk by a high TIMI-RS, a positive CCTA scan or both (n=45) resulted in a sensitivity of 95%, specificity of 49%, PPV of 35% and NPV of 97% for having haemodynamically significant coronary lesions. Those with normal perfusion were spared revascularization procedures, regardless of their TIMI-RS.

CONCLUSION

Noninvasive assessment of coronary artery disease by SPECT/CCTA may play an important role in risk stratification of patients with NSTE-ACS by better identifying the subgroup requiring intervention.