J o u r n a l o f C a r d i o v a s c u l a r C o m p u t e d T o m o g r a p h y 8 ( 2 0 1 4 ) 3 5 9 e3 6 7
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.JournalofCardiovascularCT.com
Invited Review
Coronary CT angiography for acute chest pain in the emergency department Henrique Lane Staniak MD, PhDa, Marcio Sommer Bittencourt MD, PhDa, Christopher Pickett MDb,c, Michael Cahill MDb,c, David Kassop MDb,c, Ahmad Slim MDd, Ron Blankstein MDe,f, Edward Hulten MD, MPHb,c,* a
Division of Internal Medicine, Center for Clinical and Epidemiological Research, University of Sao Paulo, Sao Paulo, Brazil b Cardiology Service, Department of Medicine, Walter Reed National Military Medical Center, 8901 Wisconsin Avenue, Bethesda, MD 20889, USA c Uniformed Services University of Health Sciences, 8901 Wisconsin Avenue, Bethesda, MD 20889, USA d Cardiology Service MCHE-MDC, San Antonio Military Medical Center, Brooke Army Medical Center, San Antonio, TX, USA e Noninvasive Cardiovascular Imaging Program, Cardiovascular Division, Department of Medicine, Brigham and Women’s Hospital, Boston, MA, USA f Department of Radiology, Harvard Medical School, Boston, MA, USA
article info
abstract
Article history:
Acute chest pain in the emergency department (ED) is a common and costly public health
Received 8 July 2014
challenge. The traditional strategy of evaluating acute chest pain by hospital or ED obser-
Received in revised form
vation over a period of several hours, serial electrocardiography and cardiac biomarkers, and
1 August 2014
subsequent diagnostic testing such as physiologic stress testing is safe and effective. Yet this
Accepted 5 August 2014
approach has been criticized for being time intensive and costly. This review evaluates the current medical evidence which has demonstrated the potential for coronary CT angiography (CTA) assessment of acute chest pain to safely reduce ED cost, time to discharge, and
Keywords:
rate of hospital admission. These benefits must be weighed against the risk of ionizing ra-
Chest pain
diation exposure and the influence of ED testing on rates of downstream coronary angiog-
Coronary computed tomography
raphy and revascularization. Efforts at radiation minimization have quickly evolved,
angiography
implementing technology such as prospective electrocardiographic gating and high pitch
Cardiac
acquisition to significantly reduce radiation exposure over just a few years. CTA in the ED has
Emergency department
demonstrated accuracy, safety, and the ability to reduce ED cost and crowding although its big-picture effect on total hospital and health care system cost extends far beyond the ED. The net effect of CTA is dependent also on the prevalence of coronary artery disease (CAD) in the population where CTA is used, which significantly influences rates of post-CTA invasive procedures such as angiography and coronary revascularization. These potential costs and
Conflict of interest: The authors report no conflicts of interest. The opinions and statements herein are the authors alone and do not represent those of the Walter Reed Army Medical Center, US Army, or the Department of Defense. * Corresponding author. E-mail address: [email protected] (E. Hulten). 1934-5925/$ e see front matter Published by Elsevier Inc. on behalf of Society of Cardiovascular Computed Tomography. http://dx.doi.org/10.1016/j.jcct.2014.08.001
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J o u r n a l o f C a r d i o v a s c u l a r C o m p u t e d T o m o g r a p h y 8 ( 2 0 1 4 ) 3 5 9 e3 6 7
benefits will warrant careful consideration and prospective monitoring as additional hospitals continue to implement this important technology into their diagnostic regimen. Published by Elsevier Inc. on behalf of Society of Cardiovascular Computed Tomography.
1.
Introduction
Acute chest pain is a leading reason for patients to seek evaluation in the emergency department (ED),1 with up to 8 million visits per year, resulting in up to US $6 billion annual costs in cardiovascular investigation.2e4 However, only a small minority of patients evaluated have acute coronary syndrome (ACS).5 In those cases, however, 30-day mortality may reach 10%.6 Due to the clinical risk of missed ACS, which also conveys a high rate of malpractice litigation,5 conventional protocols suggest admission to rule out ACS even in low-to-intermediate risk patients.7 Those protocols traditionally suggest that the initial evaluation should include history, physical examination, electrocardiogram (ECG), and cardiac biomarkers during an initial observation period, followed by noninvasive stress testing when suspected ACS remains part of the differential diagnosis. Such testing most often includes exercise treadmill testing, exercise stress echocardiography, or stress singlephoton emission CT (SPECT). Stress cardiac magnetic resonance may also be considered although this has remained limited by the lack of the availability of scanner time and a lack of widespread expertise in stress cardiac magnetic resonance. The conventional means of assessing acute chest pain in the ED may result in increased rates of admissions, unnecessary follow-up noninvasive and invasive tests, and high cost to the hospital system and to medical practitioners in terms of time invested evaluating patients without actual ACS. Finally, patients endure anxiety, lost time, and cost of follow-up testing for false-positive diagnoses.8 More recently, coronary CT angiography (CCTA) has been used to rule-out coronary artery disease (CAD) and safely discharge low to intermediate pretest probability of CAD patients without coronary obstruction who present to the ED with chest pain (Figs. 1 and 2). Recent large randomized trials have demonstrated that compared with the current standard of care, the routine use of CCTA reduces ED stay and cost in addition to total hospital stay.9 However, total hospital cost and short-term cost including follow-up testing, such as 30day posthospital discharge, have not yet been extensively studied at this time.
2.
Evolution of CCTA and the role in ACS
Coronary CTA was initially developed using electron-beam CT (EBCT) in the 1990s.10 Since then, scanners have rapidly improved in various technical aspects. Current technology now includes the use of 64- to 320-row detectors, which have 75 to 200 ms of temporal resolution and approximately 0.5mm spatial resolution. These technologies allow for highquality 3-dimensional images of coronary arteries >1.5 mm.
Recently, technologies with 256- or 320-detector scanners or the use of a rapid table speed (high pitch) using dual-source technology have allowed for single heartbeat acquisition. This has the benefit of eliminating slab artifacts from combining data from multiple heartbeats into a single image. Beyond image quality, the improvement in technology also allowed significant reductions in radiation exposure. The use of reduced tube voltage, prospective electrocardiographic gating, iterative reconstruction, and other radiation-sparing techniques has allowed an average of 73% reduction in radiation exposure in the recent years; however, data suggest that combined strategies may reduce exposure as much as 90%.11e13 Although earlier generations of CTA at higher radiation doses had comparable radiation exposure to SPECT nuclear cardiac imaging (11.5 CTA vs 12.8 SPECT in the Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patients to Treatment trial; P ¼ .02), the Prospective Randomized Trial on Radiation Dose Estimates of CT Angiography in Patients Scanned With a Sequential Scan Protocol trial reduced radiation to 3.5 mSv for axial vs 11.2 mSv for helical acquisition (P < .001).14 Similarly, another multicenter study noted a significant reduction of effective radiation during CTA (P < .001) from 8.5 mSv
Fig. 1 e Patients evaluated by coronary CT angiography (CTA) in the emergency department (ED) for acute chest pain as compared to usual care or conventional clinical assessment have been randomized in 4 trials29e32 after initial normal electrocardiography (ECG) and at least 1 set of negative cardiac biomarkers. Such patients could undergo either immediate CTA or continued serial ECG and biomarkers followed by stress testing and were found to have a 44% to 77% reduction in time to diagnosis and a 25% to 27% reduction (7e8 hours) in total hospital stay. ED cost was reduced by 15% to 38% but only 1 study31 reported total hospital cost, which was not different for CTA vs usual care.
J o u r n a l o f C a r d i o v a s c u l a r C o m p u t e d T o m o g r a p h y 8 ( 2 0 1 4 ) 3 5 9 e3 6 7
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Fig. 2 e Coronary CT angiography (CTA) from a 55-year-old woman without known coronary artery disease (CAD) with acute atypical chest pain and dynamic inferior T wave inversions. Initial cardiac biomarkers were negative and the patient was observed overnight with serial electrocardiography (ECG) and enzymes. The following day, an exercise single-photon emission CT (SPECT) was equivocal for ischemia. CTA performed the next morning showed minimal CAD with no significant stenosis. This case illustrates how an initial strategy of CTA in the emergency department may have expedited her diagnosis. The patient was evaluated by usual care with an equivocal SPECT before CTA and remained inpatient for 48 hours. LAD, left anterior descending coronary artery; LCX, left circumflex coronary artery; RCA, right coronary artery.
(historical controls with retrospective ECG gating) to 5.4 mSv (prospectively ECG gated) to 2.5 mSv (high pitch).15 The improved technology also allowed the development of several accuracy studies, which established that CCTA can be performed with high accuracy when scanners with >64 rows of detectors are used.12 Those studies were soon followed by prognostic studies, which demonstrated the clinical significance of CCTA to risk stratify patients with suspected CAD.16,17 The use of CTA to rule out ACS, especially in low-tointermediate risk patients, is supported by the Society of Cardiovascular Computed Tomography’s (SCCT) 2010 guideline, which recommends CTA in the setting of either (1) normal initial ECG and biomarkers; (2) uninterpretable ECG; or (3) nondiagnostic ECG or equivocal biomarkers for patients with either low or intermediate pretest probability of CAD.18
3.
Technical aspects of CCTA
Detailed technical guidelines on the acquisition,12 interpretation, and reporting19 of CCTA have been previously published by the SCCT. In short, the patient preparation includes the placement of a peripheral intravenous catheter for a rapid contrast infusion (eg, 5 mL/s). To have adequate images for the current temporal resolution, a goal heart rate should be below 60 to 65 beats/min depending on the scanner technology. For patients with higher heart rates oral or intravenous beta-
blockers are usually recommended, as lower heart rates are associated with improved image quality. Additionally, sublingual nitrates are used to achieve coronary vasodilation immediately before scanning to improve image quality and diagnostic accuracy. Contrast injection protocols are usually individualized; however, they routinely include a dual-phase injection of contrast followed by a saline infusion. Image interpretation includes the reading of axial images and use of multiplanar oblique reconstructions from different viewpoints to further assess areas of possible coronary stenosis. The SCCT recommends that all CTA should be interpreted with the use of a 3-dimensional workstation. Images should be reconstructed with the thinnest slice width for optimal coronary evaluation. To perform CCTAs as part of a chest pain unit in the ED, workflow should include clear definition of the indications, contraindications, and standardization of the ordering process, patient preparation, and optimization of the CT image acquisition. Some investigators have considered whether acute chest pain ought to be evaluated with a “triple rule-out” protocol (ie, rule-out acute coronary syndrome, aortic dissection, and pulmonary embolus in a single scan), but there is no clear clinical benefit to this broad approach which has the disadvantage of significantly increased radiation, acquisition, and setup time, higher contrast dose, and longer interpretation and reporting time. Thus, routine use of a “triple rule-out” protocol is not currently recommended.20 As ED use of CCTA may include expanded hours of operation and training of a
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large team, a stepwise planning for the workflow has been proposed by SCCT,21 and guidelines on performance and interpretation of CCTA in the ED have been recently published.20
4. Clinical outcomes after the use of CCTA to evaluate acute chest pain in the ED Before engaging in a discussion about evaluation of acute chest pain by CCTA, a succinct mention of the interest in using noncontrast CT for evaluation of acute chest pain is warranted. In brief, noncontrast CT (coronary artery calcium scan [CAC]) can be performed rapidly at 1 to 2 mSv effective radiation, although it does require gated CT software and hardware and some experience in interpretation of scans. By comparison with CTA, CAC has the relative merits of being simpler, cheaper, and faster to conduct and interpret. The major disadvantage is the inability to visualize noncalcified plaque, which may be present in a large proportion of patients, even to an obstructive severity (Fig. 3) in a smaller percentage (1%e3%). Additionally, extensive nonobstructive plaque has important prognostic value which can be readily
assessed by CTA but not CAC.17 A second disadvantage is that a large percentage of ED patients may have positive CAC that will require additional testing, and this percentage of positive CAC will increase with older and less healthy populations. Although a small percentage of patients with zero CAC may have noncalcified plaque, future adverse events among such patients predominantly comprise coronary revascularization.22,23 A number of observational studies have compared CAC with CTA for accuracy and downstream outcomes, but because these cohorts are composed of patients undergoing both CAC and CTA, such studies are limited by the bias introduced by CTA results, influencing the management and subsequent prognosis of patients studied concurrently by CAC. Unfortunately, a randomized blinded comparison of these tests is not practical to conduct. Although CAC is not considered a first-line test among most practitioners because of its inability to rule out stenosis by noncalcified plaque as a cause of symptomatic angina, this test is mentioned (in passing) in an American consensus statement24 and (with a bit more endorsement) by the UK chest pain guidelines25 as a diagnostic option for use with Bayesian reasoning26 among lowto-intermediate pretest probability chest pain patients in the
Fig. 3 e Coronary CT angiography (CTA) from a 58-year-old woman who presented with acute rest chest pain found to have a focal noncalcified plaque with nearly complete occlusion (arrows) of the mid-left anterior descending (LAD) coronary artery: (A) volume-rendered 3-dimensional reconstruction; (B) curved multiplanar reconstruction; (C) LAD cross-section. Invasive angiography confirmed the stenosis (D, with inset) and the patient successfully underwent percutaneous coronary intervention (E). Although this case illustrates acute chest pain due to purely noncalcified plaque, the percentage of patients with stenosis due to purely noncalcified plaque is extremely small.23
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ED. Yet, for most patients with acute chest pain, CTA will remain a preferable option to noncontrast CAC for the aforementioned reasons. With recent technical advances, CTA has evolved into a powerful diagnostic tool that can provide a rapid and accurate evaluation of appropriately selected patients who present with acute chest pain in the ED concerning for ACS. With a high negative predictive value in a low-to-intermediate pretest probability chest pain population, CTA has become an attractive alternative to usual care evaluation of acute chest pain.27,28 At present, there have been 4 randomized controlled trials (RCTs) that have compared the use of CTA to usual care for patients presenting to the ED for suspected ACS,29e32 with a subsequent meta-analysis of these studies.9 The first RCT from Goldstein et al30 was a single-center analysis that demonstrated no major adverse cardiac events (MACE) in the index visit or 6-month follow-up in 99 patients with symptoms of possible ACS randomized to CTA vs usual care in the ED. Furthermore, during the index visit, CTA reduced diagnostic time compared with usual care (3.4 vs 15 hours; P < .001), and CTA patients required fewer repeat evaluations for recurrent chest pain. Similarly, the first multicenter RCT, the Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patients to Treatment trial, demonstrated no MACE in 361 patients randomized to CCTA vs usual care. Additionally, CTA resulted in a 54% reduction in time to diagnosis compared with usual care (P < .0001).29 Next, the American College of Radiology Imaging Network of Pennsylvania trial assigned low-to-intermediate risk patients presenting with possible ACS, in a 2 to 1 ratio, to undergo CTA or usual care evaluation of chest pain. In this study, among 640 patients with a negative CTA, none died or had a myocardial infarction within 30 days. Moreover, as compared with patients receiving usual care, those in the CTA group had a higher rate of discharge from the ED (49.6% vs 22.7%), a shorter length of stay (median, 18.0 vs 24.8 hours; P < .001), and a higher rate of CAD detection (9% vs 3.5%).32 Finally, the third multicenter RCT, the Rule out Myocardial Ischemia/Infarction Using Computer Assisted Tomography (ROMICAT) II trial, demonstrated no undetected ACS and no significant differences in MACE among 1000 patients randomized to early CTA vs usual care. Furthermore, the mean length of stay in the hospital was reduced by 7.6 hours (P < .001) and more patients were discharged directly from the ED (47% vs 12%; P < .001). However, after CTA, there was more downstream testing and higher radiation exposure.31 In a pooled analysis consisting of 1869 patients who underwent CTA in the 4 RCTs, Hulten et al9 showed that there were no deaths and no difference in the incidence of myocardial infarction, postdischarge ED visits, or repeat hospitalization compared with patients who underwent usual care. However, there was an increased incidence of invasive coronary angiography and coronary revascularization among patients evaluated by CTA, of uncertain clinical significance. For example, CTA patients most commonly do not undergo physiologic assessment such as with SPECT or fractional flow reserve before revascularization. The patients, if experiencing ischemia during ACS, likely benefit from revascularization. But if ischemia, which has not been assessed for, was not
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present and the CTA findings are incidental than increased, revascularization might be undesirable. In addition to these RCTs, several observational studies have demonstrated associations of CTA with downstream clinical outcomes. For example, Poon et al33 showed in a retrospective cohort comparing 894 patients who underwent CTA to matched controls undergoing a usual care evaluation, that CTA evaluation of ED chest pain was associated with reduced hospital admission (14% CTA vs 40% usual care; P < .001), time to ED discharge (7.7 vs 11.5 hours; P < .001), and downstream testing and invasive angiography but no difference in coronary revascularization. The lower incidence of invasive angiography contrasts with the aforementioned RCT, but one explanation, as the authors acknowledge, could be the comparatively low prevalence of obstructive CAD among the patients evaluated by CTA in Poon’s cohort (17 obstructive CAD of 894 [1.9%]). Although these studies were limited to short-term followup, the observational ROMICAT I study investigators completed longer-term follow-up in 333 patients over a 2-year period. In this study, all patients evaluated for acute chest pain in the ED underwent usual care and CTA, with caregivers and patients blinded to the CTA results. Among 183 patients (50%) with no CAD, there was no MACE in a 2-year follow-up. However, among 117 patients (32%) with nonobstructive CAD (50% stenosis), there was a 4.6% rate of MACE in the same period. Most importantly, this study showed that the absence of CAD on CTA provides a 2-year MACE-free warranty period.34 More recently, a large cohort study demonstrated that 585 patients with acute chest pain were safely evaluated by CTA, and among the 506 discharged home from the ED, there was no death, ACS, or coronary revascularization at 4year follow-up.35 In summary, the current evidence based on these prior studies has consistently demonstrated that CTA is an accurate, safe, and efficient alternative to usual care in low-tointermediate risk patients who present to the ED for acute chest pain. A large proportion of patients with acute chest pain symptoms are found to have no or mild CAD (65 years with a high prevalence of CAD) and concluded that evaluation of chest pain by CTA in a Medicare population was associated with increased cost compared with usual care.
7.
Conclusion
In summary, CCTA offers a safe rapid alternative to usual care for evaluation of acute chest pain in the ED for patients who
have at least 1 normal ECG and troponin. However, the test is associated with increased radiation exposure and could lead to increased testing if used indiscriminately among patients who otherwise do not require testing. Some studies have suggested that incidence of ICA and revascularization is increased after CTA in the ED, of unclear long-term clinical significance. CTA has a unique advantage of diagnosing extensive nonobstructive CAD, which has prognostic significance, and is not detected by traditional diagnostic tests for assessment of acute chest pain. CTA clearly offers potential to reduce ED crowding and cost, although its ultimate impact on total hospital and health care system cost is not yet rigorously studied.
references
1. Pitts SR, Niska RW, Xu J, Burt CW. National Hospital Ambulatory Medical Care Survey: 2006 emergency department summary. Natl Health Stat Rep; 2008: 1e38.
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2. Bhuiya FA, Pitts SR, McCaig LF. Emergency department visits for chest pain and abdominal pain: United states, 1999-2008. NCHS Data Brief; 2010:1e8. 3. Owens PL, Barrett ML, Gibson TB, Andrews RM, Weinick RM, Mutter RL. Emergency department care in the United States: a profile of national data sources. Ann Emerg Med. 2010;56:150e165. 4. Rubinshtein R, Halon DA, Gaspar T, et al. Usefulness of 64slice cardiac computed tomographic angiography for diagnosing acute coronary syndromes and predicting clinical outcome in emergency department patients with chest pain of uncertain origin. Circulation. 2007;115:1762e1768. 5. Pope JH, Aufderheide TP, Ruthazer R, et al. Missed diagnoses of acute cardiac ischemia in the emergency department. N Engl J Med. 2000;342:1163e1170. 6. Launbjerg J, Fruergaard P, Hesse B, Jorgensen F, Elsborg L, Petri A. Long-term risk of death, cardiac events and recurrent chest pain in patients with acute chest pain of different origin. Cardiology. 1996;87:60e66. 7. Amsterdam EA, Kirk JD, Bluemke DA, et al. Testing of low-risk patients presenting to the emergency department with chest pain: a scientific statement from the American Heart Association. Circulation. 2010;122:1756e1776. 8. Hollander JE, Robey JL, Chase MR, Brown AM, Zogby KE, Shofer FS. Relationship between a clear-cut alternative noncardiac diagnosis and 30-day outcome in emergency department patients with chest pain. Acad Emerg Med. 2007;14:210e215. 9. Hulten E, Pickett C, Bittencourt MS, et al. Outcomes after coronary computed tomography angiography in the emergency department: a systematic review and metaanalysis of randomized, controlled trials. J Am Coll Cardiol. 2013;61(8):880e892. 10. Moshage WE, Achenbach S, Seese B, Bachmann K, Kirchgeorg M. Coronary artery stenoses: three-dimensional imaging with electrocardiographically triggered, contrast agent-enhanced, electron-beam CT. Radiology. 1995;196:707e714. 11. Ghoshhajra BB, Engel LC, Major GP, et al. Evolution of coronary computed tomography radiation dose reduction at a tertiary referral center. Am J Med. 2012;125:764e772. 12. Abbara S, Arbab-Zadeh A, Callister TQ, et al. SCCT guidelines for performance of coronary computed tomographic angiography: a report of the Society of Cardiovascular Computed Tomography Guidelines Committee. J Cardiovasc Comput Tomogr. 2009;3:190e204. 13. Hausleiter J, Meyer T, Hermann F, et al. Estimated radiation dose associated with cardiac CT angiography. JAMA. 2009;301:500e507. 14. Hausleiter J, Meyer TS, Martuscelli E, et al. Image quality and radiation exposure with prospectively ECG-triggered axial scanning for coronary CT angiography: the multicenter, multivendor, randomized PROTECTION-III study. JACC Cardiovasc Imaging. 2012;5:484e493. 15. Chinnaiyan KM, Bilolikar AN, Walsh E, et al. CT dose reduction using prospectively triggered or fast-pitch spiral technique employed in cardiothoracic imaging (the CT dose study). J Cardiovasc Comput Tomogr. 2014;8:205e214. 16. Min JK, Dunning A, Lin FY, et al. Age- and sex-related differences in all-cause mortality risk based on coronary computed tomography angiography findings results from the International Multicenter CONFIRM (Coronary CT Angiography Evaluation for Clinical Outcomes: An International Multicenter Registry) of 23,854 patients without known coronary artery disease. J Am Coll Cardiol. 2011;58:849e860.
17. Bittencourt MS, Hulten E, Ghoshhajra B, et al. Prognostic value of nonobstructive and obstructive coronary artery disease detected by coronary computed tomography angiography to identify cardiovascular events. Circ Cardiovasc Imaging. 2014;7:282e291. 18. Taylor AJ, Cerqueira M, Hodgson JM, et al. ACCF/SCCT/ACR/ AHA/ASE/ASNC/NASCI/SCAI/SCMR 2010 appropriate use criteria for cardiac computed tomography. A report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, the Society of Cardiovascular Computed Tomography, the American College of Radiology, the American Heart Association, the American Society of Echocardiography, the American Society of Nuclear Cardiology, the North American Society for Cardiovascular Imaging, the Society for Cardiovascular Angiography and Interventions, and the Society for Cardiovascular Magnetic Resonance. J Cardiovasc Comput Tomogr. 2010;4:407.e401e407.e433. 19. Leipsic J, Abbara S, Achenbach S, et al. SCCT guidelines for the interpretation and reporting of coronary CT angiography: a report of the Society of Cardiovascular Computed Tomography Guidelines Committee. J Cardiovasc Comput Tomogr. 2014;8:342e358. 20. Raff GL, Chinnaiyan KM, Cury RC, et al. SCCT guidelines on the use of coronary computed tomographic angiography for patients presenting with acute chest pain to the emergency department: a Report of the Society of Cardiovascular Computed Tomography Guidelines Committee. J Cardiovasc Comput Tomogr. 2014;8(4):254e271. 21. Maroules CD, Blaha MJ, El-Haddad MA, Ferencik M, Cury RC. Establishing a successful coronary CT angiography program in the emergency department: official writing of the Fellow and Resident Leaders of the Society of Cardiovascular Computed Tomography (FiRST). J Cardiovasc Comput Tomogr. 2013;7:150e156. 22. Villines TC, Hulten EA, Shaw LJ, et al. Prevalence and severity of coronary artery disease and adverse events among symptomatic patients with coronary artery calcification scores of zero undergoing coronary computed tomography angiography: results from the CONFIRM (Coronary CT Angiography Evaluation for Clinical Outcomes: An International Multicenter) registry. J Am Coll Cardiol. 2011;58:2533e2540. 23. Hulten E, Bittencourt MS, Ghoshhajra B, et al. Incremental prognostic value of coronary artery calcium score versus CT angiography among symptomatic patients without known coronary artery disease. Atherosclerosis. 2014;233:190e195. 24. Greenland P, Bonow RO, Brundage BH, et al. ACCF/AHA 2007 clinical expert consensus document on coronary artery calcium scoring by computed tomography in global cardiovascular risk assessment and in evaluation of patients with chest pain: a report of the American College of Cardiology Foundation Clinical Expert Consensus Task Force (ACCF/AHA Writing Committee to Update the 2000 Expert Consensus Document on Electron Beam Computed Tomography) developed in collaboration with the Society of Atherosclerosis Imaging and Prevention and the Society of Cardiovascular Computed Tomography. J Am Coll Cardiol. 2007;49:378e402. 25. Skinner JS, Smeeth L, Kendall JM, Adams PC, Timmis A. NICE guidance. Chest pain of recent onset: assessment and diagnosis of recent onset chest pain or discomfort of suspected cardiac origin. Heart. 2010;96:974e978. 26. Greenland P, Bonow RO. How low-risk is a coronary calcium score of zero? The importance of conditional probability. Circulation. 2008;117:1627e1629.
J o u r n a l o f C a r d i o v a s c u l a r C o m p u t e d T o m o g r a p h y 8 ( 2 0 1 4 ) 3 5 9 e3 6 7
27. Mowatt G, Cook JA, Hillis GS, et al. 64-slice computed tomography angiography in the diagnosis and assessment of coronary artery disease: systematic review and metaanalysis. Heart. 2008;94:1386e1393. 28. Hulten EA, Carbonaro S, Petrillo SP, Mitchell JD, Villines TC. Prognostic value of cardiac computed tomography angiography: a systematic review and meta-analysis. J Am Coll Cardiol. 2011;57:1237e1247. 29. Goldstein JA, Chinnaiyan KM, Abidov A, et al. The CT-STAT (Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patients to Treatment) trial. J Am Coll Cardiol. 2011;58:1414e1422. 30. Goldstein JA, Gallagher MJ, O’Neill WW, Ross MA, O’Neil BJ, Raff GL. A randomized controlled trial of multi-slice coronary computed tomography for evaluation of acute chest pain. J Am Coll Cardiol. 2007;49:863e871. 31. Hoffmann U, Truong QA, Schoenfeld DA, et al. Coronary CT angiography versus standard evaluation in acute chest pain. N Engl J Med. 2012;367:299e308. 32. Litt HI, Gatsonis C, Snyder B, et al. CT angiography for safe discharge of patients with possible acute coronary syndromes. N Engl J Med. 2012;366:1393e1403. 33. Poon M, Cortegiano M, Abramowicz AJ, et al. Associations between routine coronary computed tomographic angiography and reduced unnecessary hospital admissions, length of stay, recidivism rates, and invasive coronary angiography in the emergency department triage of chest pain. J Am Coll Cardiol. 2013;62:543e552. 34. Schlett CL, Banerji D, Siegel E, et al. Prognostic value of CT angiography for major adverse cardiac events in patients with acute chest pain from the emergency department: 2year outcomes of the ROMICAT trial. JACC Cardiovasc Imaging. 2011;4:481e491. 35. Nasis A, Meredith IT, Sud PS, Cameron JD, Troupis JM, Seneviratne SK. Long-term outcome after CT Angiography in
36.
37.
38.
39.
40.
41.
42.
367
Patients with Possible Acute Coronary Syndrome. Radiology. 2014;272(3):674e682. Hulten E, Bittencourt MS, Singh A, et al. Coronary artery disease detected by coronary computed tomographic angiography is associated with intensification of preventive medical therapy and lower low-density lipoprotein cholesterol. Circ Cardiovasc Imaging. 2014;7(4):629e638. Einstein AJ, Henzlova MJ, Rajagopalan S. Estimating risk of cancer associated with radiation exposure from 64-slice computed tomography coronary angiography. JAMA. 2007;298:317e323. Schull MJ, Vermeulen M, Slaughter G, Morrison L, Daly P. Emergency department crowding and thrombolysis delays in acute myocardial infarction. Ann Emerg Med. 2004;44:577e585. Henzler T, Gruettner J, Meyer M, et al. Coronary computed tomography and triple rule out CT in patients with acute chest pain and an intermediate cardiac risk for acute coronary syndrome: part 2: economic aspects. Eur J Radiol. 2013;82:106e111. Miller AH, Pepe PE, Peshock R, et al. Is coronary computed tomography angiography a resource sparing strategy in the risk stratification and evaluation of acute chest pain? Results of a randomized controlled trial. Acad Emerg Med. 2011;18:458e467. Hulten E, Goehler A, Bittencourt MS, et al. Cost and resource utilization associated with use of computed tomography to evaluate chest pain in the emergency department: the Rule Out Myocardial Infarction Using Computer Assisted Tomography (ROMICAT) study. Circ Cardiovasc Qual Outcomes. 2013;6:514e524. Shreibati JB, Baker LC, Hlatky MA. Association of coronary CT angiography or stress testing with subsequent utilization and spending among Medicare beneficiaries. JAMA. 2011;306:2128e2136.
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Invited Review
Coronary CT angiography for acute chest pain in the emergency department Henrique Lane Staniak MD, PhDa, Marcio Sommer Bittencourt MD, PhDa, Christopher Pickett MDb,c, Michael Cahill MDb,c, David Kassop MDb,c, Ahmad Slim MDd, Ron Blankstein MDe,f, Edward Hulten MD, MPHb,c,* a
Division of Internal Medicine, Center for Clinical and Epidemiological Research, University of Sao Paulo, Sao Paulo, Brazil b Cardiology Service, Department of Medicine, Walter Reed National Military Medical Center, 8901 Wisconsin Avenue, Bethesda, MD 20889, USA c Uniformed Services University of Health Sciences, 8901 Wisconsin Avenue, Bethesda, MD 20889, USA d Cardiology Service MCHE-MDC, San Antonio Military Medical Center, Brooke Army Medical Center, San Antonio, TX, USA e Noninvasive Cardiovascular Imaging Program, Cardiovascular Division, Department of Medicine, Brigham and Women’s Hospital, Boston, MA, USA f Department of Radiology, Harvard Medical School, Boston, MA, USA
article info
abstract
Article history:
Acute chest pain in the emergency department (ED) is a common and costly public health
Received 8 July 2014
challenge. The traditional strategy of evaluating acute chest pain by hospital or ED obser-
Received in revised form
vation over a period of several hours, serial electrocardiography and cardiac biomarkers, and
1 August 2014
subsequent diagnostic testing such as physiologic stress testing is safe and effective. Yet this
Accepted 5 August 2014
approach has been criticized for being time intensive and costly. This review evaluates the current medical evidence which has demonstrated the potential for coronary CT angiography (CTA) assessment of acute chest pain to safely reduce ED cost, time to discharge, and
Keywords:
rate of hospital admission. These benefits must be weighed against the risk of ionizing ra-
Chest pain
diation exposure and the influence of ED testing on rates of downstream coronary angiog-
Coronary computed tomography
raphy and revascularization. Efforts at radiation minimization have quickly evolved,
angiography
implementing technology such as prospective electrocardiographic gating and high pitch
Cardiac
acquisition to significantly reduce radiation exposure over just a few years. CTA in the ED has
Emergency department
demonstrated accuracy, safety, and the ability to reduce ED cost and crowding although its big-picture effect on total hospital and health care system cost extends far beyond the ED. The net effect of CTA is dependent also on the prevalence of coronary artery disease (CAD) in the population where CTA is used, which significantly influences rates of post-CTA invasive procedures such as angiography and coronary revascularization. These potential costs and
Conflict of interest: The authors report no conflicts of interest. The opinions and statements herein are the authors alone and do not represent those of the Walter Reed Army Medical Center, US Army, or the Department of Defense. * Corresponding author. E-mail address: [email protected] (E. Hulten). 1934-5925/$ e see front matter Published by Elsevier Inc. on behalf of Society of Cardiovascular Computed Tomography. http://dx.doi.org/10.1016/j.jcct.2014.08.001
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benefits will warrant careful consideration and prospective monitoring as additional hospitals continue to implement this important technology into their diagnostic regimen. Published by Elsevier Inc. on behalf of Society of Cardiovascular Computed Tomography.
1.
Introduction
Acute chest pain is a leading reason for patients to seek evaluation in the emergency department (ED),1 with up to 8 million visits per year, resulting in up to US $6 billion annual costs in cardiovascular investigation.2e4 However, only a small minority of patients evaluated have acute coronary syndrome (ACS).5 In those cases, however, 30-day mortality may reach 10%.6 Due to the clinical risk of missed ACS, which also conveys a high rate of malpractice litigation,5 conventional protocols suggest admission to rule out ACS even in low-to-intermediate risk patients.7 Those protocols traditionally suggest that the initial evaluation should include history, physical examination, electrocardiogram (ECG), and cardiac biomarkers during an initial observation period, followed by noninvasive stress testing when suspected ACS remains part of the differential diagnosis. Such testing most often includes exercise treadmill testing, exercise stress echocardiography, or stress singlephoton emission CT (SPECT). Stress cardiac magnetic resonance may also be considered although this has remained limited by the lack of the availability of scanner time and a lack of widespread expertise in stress cardiac magnetic resonance. The conventional means of assessing acute chest pain in the ED may result in increased rates of admissions, unnecessary follow-up noninvasive and invasive tests, and high cost to the hospital system and to medical practitioners in terms of time invested evaluating patients without actual ACS. Finally, patients endure anxiety, lost time, and cost of follow-up testing for false-positive diagnoses.8 More recently, coronary CT angiography (CCTA) has been used to rule-out coronary artery disease (CAD) and safely discharge low to intermediate pretest probability of CAD patients without coronary obstruction who present to the ED with chest pain (Figs. 1 and 2). Recent large randomized trials have demonstrated that compared with the current standard of care, the routine use of CCTA reduces ED stay and cost in addition to total hospital stay.9 However, total hospital cost and short-term cost including follow-up testing, such as 30day posthospital discharge, have not yet been extensively studied at this time.
2.
Evolution of CCTA and the role in ACS
Coronary CTA was initially developed using electron-beam CT (EBCT) in the 1990s.10 Since then, scanners have rapidly improved in various technical aspects. Current technology now includes the use of 64- to 320-row detectors, which have 75 to 200 ms of temporal resolution and approximately 0.5mm spatial resolution. These technologies allow for highquality 3-dimensional images of coronary arteries >1.5 mm.
Recently, technologies with 256- or 320-detector scanners or the use of a rapid table speed (high pitch) using dual-source technology have allowed for single heartbeat acquisition. This has the benefit of eliminating slab artifacts from combining data from multiple heartbeats into a single image. Beyond image quality, the improvement in technology also allowed significant reductions in radiation exposure. The use of reduced tube voltage, prospective electrocardiographic gating, iterative reconstruction, and other radiation-sparing techniques has allowed an average of 73% reduction in radiation exposure in the recent years; however, data suggest that combined strategies may reduce exposure as much as 90%.11e13 Although earlier generations of CTA at higher radiation doses had comparable radiation exposure to SPECT nuclear cardiac imaging (11.5 CTA vs 12.8 SPECT in the Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patients to Treatment trial; P ¼ .02), the Prospective Randomized Trial on Radiation Dose Estimates of CT Angiography in Patients Scanned With a Sequential Scan Protocol trial reduced radiation to 3.5 mSv for axial vs 11.2 mSv for helical acquisition (P < .001).14 Similarly, another multicenter study noted a significant reduction of effective radiation during CTA (P < .001) from 8.5 mSv
Fig. 1 e Patients evaluated by coronary CT angiography (CTA) in the emergency department (ED) for acute chest pain as compared to usual care or conventional clinical assessment have been randomized in 4 trials29e32 after initial normal electrocardiography (ECG) and at least 1 set of negative cardiac biomarkers. Such patients could undergo either immediate CTA or continued serial ECG and biomarkers followed by stress testing and were found to have a 44% to 77% reduction in time to diagnosis and a 25% to 27% reduction (7e8 hours) in total hospital stay. ED cost was reduced by 15% to 38% but only 1 study31 reported total hospital cost, which was not different for CTA vs usual care.
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Fig. 2 e Coronary CT angiography (CTA) from a 55-year-old woman without known coronary artery disease (CAD) with acute atypical chest pain and dynamic inferior T wave inversions. Initial cardiac biomarkers were negative and the patient was observed overnight with serial electrocardiography (ECG) and enzymes. The following day, an exercise single-photon emission CT (SPECT) was equivocal for ischemia. CTA performed the next morning showed minimal CAD with no significant stenosis. This case illustrates how an initial strategy of CTA in the emergency department may have expedited her diagnosis. The patient was evaluated by usual care with an equivocal SPECT before CTA and remained inpatient for 48 hours. LAD, left anterior descending coronary artery; LCX, left circumflex coronary artery; RCA, right coronary artery.
(historical controls with retrospective ECG gating) to 5.4 mSv (prospectively ECG gated) to 2.5 mSv (high pitch).15 The improved technology also allowed the development of several accuracy studies, which established that CCTA can be performed with high accuracy when scanners with >64 rows of detectors are used.12 Those studies were soon followed by prognostic studies, which demonstrated the clinical significance of CCTA to risk stratify patients with suspected CAD.16,17 The use of CTA to rule out ACS, especially in low-tointermediate risk patients, is supported by the Society of Cardiovascular Computed Tomography’s (SCCT) 2010 guideline, which recommends CTA in the setting of either (1) normal initial ECG and biomarkers; (2) uninterpretable ECG; or (3) nondiagnostic ECG or equivocal biomarkers for patients with either low or intermediate pretest probability of CAD.18
3.
Technical aspects of CCTA
Detailed technical guidelines on the acquisition,12 interpretation, and reporting19 of CCTA have been previously published by the SCCT. In short, the patient preparation includes the placement of a peripheral intravenous catheter for a rapid contrast infusion (eg, 5 mL/s). To have adequate images for the current temporal resolution, a goal heart rate should be below 60 to 65 beats/min depending on the scanner technology. For patients with higher heart rates oral or intravenous beta-
blockers are usually recommended, as lower heart rates are associated with improved image quality. Additionally, sublingual nitrates are used to achieve coronary vasodilation immediately before scanning to improve image quality and diagnostic accuracy. Contrast injection protocols are usually individualized; however, they routinely include a dual-phase injection of contrast followed by a saline infusion. Image interpretation includes the reading of axial images and use of multiplanar oblique reconstructions from different viewpoints to further assess areas of possible coronary stenosis. The SCCT recommends that all CTA should be interpreted with the use of a 3-dimensional workstation. Images should be reconstructed with the thinnest slice width for optimal coronary evaluation. To perform CCTAs as part of a chest pain unit in the ED, workflow should include clear definition of the indications, contraindications, and standardization of the ordering process, patient preparation, and optimization of the CT image acquisition. Some investigators have considered whether acute chest pain ought to be evaluated with a “triple rule-out” protocol (ie, rule-out acute coronary syndrome, aortic dissection, and pulmonary embolus in a single scan), but there is no clear clinical benefit to this broad approach which has the disadvantage of significantly increased radiation, acquisition, and setup time, higher contrast dose, and longer interpretation and reporting time. Thus, routine use of a “triple rule-out” protocol is not currently recommended.20 As ED use of CCTA may include expanded hours of operation and training of a
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large team, a stepwise planning for the workflow has been proposed by SCCT,21 and guidelines on performance and interpretation of CCTA in the ED have been recently published.20
4. Clinical outcomes after the use of CCTA to evaluate acute chest pain in the ED Before engaging in a discussion about evaluation of acute chest pain by CCTA, a succinct mention of the interest in using noncontrast CT for evaluation of acute chest pain is warranted. In brief, noncontrast CT (coronary artery calcium scan [CAC]) can be performed rapidly at 1 to 2 mSv effective radiation, although it does require gated CT software and hardware and some experience in interpretation of scans. By comparison with CTA, CAC has the relative merits of being simpler, cheaper, and faster to conduct and interpret. The major disadvantage is the inability to visualize noncalcified plaque, which may be present in a large proportion of patients, even to an obstructive severity (Fig. 3) in a smaller percentage (1%e3%). Additionally, extensive nonobstructive plaque has important prognostic value which can be readily
assessed by CTA but not CAC.17 A second disadvantage is that a large percentage of ED patients may have positive CAC that will require additional testing, and this percentage of positive CAC will increase with older and less healthy populations. Although a small percentage of patients with zero CAC may have noncalcified plaque, future adverse events among such patients predominantly comprise coronary revascularization.22,23 A number of observational studies have compared CAC with CTA for accuracy and downstream outcomes, but because these cohorts are composed of patients undergoing both CAC and CTA, such studies are limited by the bias introduced by CTA results, influencing the management and subsequent prognosis of patients studied concurrently by CAC. Unfortunately, a randomized blinded comparison of these tests is not practical to conduct. Although CAC is not considered a first-line test among most practitioners because of its inability to rule out stenosis by noncalcified plaque as a cause of symptomatic angina, this test is mentioned (in passing) in an American consensus statement24 and (with a bit more endorsement) by the UK chest pain guidelines25 as a diagnostic option for use with Bayesian reasoning26 among lowto-intermediate pretest probability chest pain patients in the
Fig. 3 e Coronary CT angiography (CTA) from a 58-year-old woman who presented with acute rest chest pain found to have a focal noncalcified plaque with nearly complete occlusion (arrows) of the mid-left anterior descending (LAD) coronary artery: (A) volume-rendered 3-dimensional reconstruction; (B) curved multiplanar reconstruction; (C) LAD cross-section. Invasive angiography confirmed the stenosis (D, with inset) and the patient successfully underwent percutaneous coronary intervention (E). Although this case illustrates acute chest pain due to purely noncalcified plaque, the percentage of patients with stenosis due to purely noncalcified plaque is extremely small.23
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ED. Yet, for most patients with acute chest pain, CTA will remain a preferable option to noncontrast CAC for the aforementioned reasons. With recent technical advances, CTA has evolved into a powerful diagnostic tool that can provide a rapid and accurate evaluation of appropriately selected patients who present with acute chest pain in the ED concerning for ACS. With a high negative predictive value in a low-to-intermediate pretest probability chest pain population, CTA has become an attractive alternative to usual care evaluation of acute chest pain.27,28 At present, there have been 4 randomized controlled trials (RCTs) that have compared the use of CTA to usual care for patients presenting to the ED for suspected ACS,29e32 with a subsequent meta-analysis of these studies.9 The first RCT from Goldstein et al30 was a single-center analysis that demonstrated no major adverse cardiac events (MACE) in the index visit or 6-month follow-up in 99 patients with symptoms of possible ACS randomized to CTA vs usual care in the ED. Furthermore, during the index visit, CTA reduced diagnostic time compared with usual care (3.4 vs 15 hours; P < .001), and CTA patients required fewer repeat evaluations for recurrent chest pain. Similarly, the first multicenter RCT, the Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patients to Treatment trial, demonstrated no MACE in 361 patients randomized to CCTA vs usual care. Additionally, CTA resulted in a 54% reduction in time to diagnosis compared with usual care (P < .0001).29 Next, the American College of Radiology Imaging Network of Pennsylvania trial assigned low-to-intermediate risk patients presenting with possible ACS, in a 2 to 1 ratio, to undergo CTA or usual care evaluation of chest pain. In this study, among 640 patients with a negative CTA, none died or had a myocardial infarction within 30 days. Moreover, as compared with patients receiving usual care, those in the CTA group had a higher rate of discharge from the ED (49.6% vs 22.7%), a shorter length of stay (median, 18.0 vs 24.8 hours; P < .001), and a higher rate of CAD detection (9% vs 3.5%).32 Finally, the third multicenter RCT, the Rule out Myocardial Ischemia/Infarction Using Computer Assisted Tomography (ROMICAT) II trial, demonstrated no undetected ACS and no significant differences in MACE among 1000 patients randomized to early CTA vs usual care. Furthermore, the mean length of stay in the hospital was reduced by 7.6 hours (P < .001) and more patients were discharged directly from the ED (47% vs 12%; P < .001). However, after CTA, there was more downstream testing and higher radiation exposure.31 In a pooled analysis consisting of 1869 patients who underwent CTA in the 4 RCTs, Hulten et al9 showed that there were no deaths and no difference in the incidence of myocardial infarction, postdischarge ED visits, or repeat hospitalization compared with patients who underwent usual care. However, there was an increased incidence of invasive coronary angiography and coronary revascularization among patients evaluated by CTA, of uncertain clinical significance. For example, CTA patients most commonly do not undergo physiologic assessment such as with SPECT or fractional flow reserve before revascularization. The patients, if experiencing ischemia during ACS, likely benefit from revascularization. But if ischemia, which has not been assessed for, was not
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present and the CTA findings are incidental than increased, revascularization might be undesirable. In addition to these RCTs, several observational studies have demonstrated associations of CTA with downstream clinical outcomes. For example, Poon et al33 showed in a retrospective cohort comparing 894 patients who underwent CTA to matched controls undergoing a usual care evaluation, that CTA evaluation of ED chest pain was associated with reduced hospital admission (14% CTA vs 40% usual care; P < .001), time to ED discharge (7.7 vs 11.5 hours; P < .001), and downstream testing and invasive angiography but no difference in coronary revascularization. The lower incidence of invasive angiography contrasts with the aforementioned RCT, but one explanation, as the authors acknowledge, could be the comparatively low prevalence of obstructive CAD among the patients evaluated by CTA in Poon’s cohort (17 obstructive CAD of 894 [1.9%]). Although these studies were limited to short-term followup, the observational ROMICAT I study investigators completed longer-term follow-up in 333 patients over a 2-year period. In this study, all patients evaluated for acute chest pain in the ED underwent usual care and CTA, with caregivers and patients blinded to the CTA results. Among 183 patients (50%) with no CAD, there was no MACE in a 2-year follow-up. However, among 117 patients (32%) with nonobstructive CAD (50% stenosis), there was a 4.6% rate of MACE in the same period. Most importantly, this study showed that the absence of CAD on CTA provides a 2-year MACE-free warranty period.34 More recently, a large cohort study demonstrated that 585 patients with acute chest pain were safely evaluated by CTA, and among the 506 discharged home from the ED, there was no death, ACS, or coronary revascularization at 4year follow-up.35 In summary, the current evidence based on these prior studies has consistently demonstrated that CTA is an accurate, safe, and efficient alternative to usual care in low-tointermediate risk patients who present to the ED for acute chest pain. A large proportion of patients with acute chest pain symptoms are found to have no or mild CAD (65 years with a high prevalence of CAD) and concluded that evaluation of chest pain by CTA in a Medicare population was associated with increased cost compared with usual care.
7.
Conclusion
In summary, CCTA offers a safe rapid alternative to usual care for evaluation of acute chest pain in the ED for patients who
have at least 1 normal ECG and troponin. However, the test is associated with increased radiation exposure and could lead to increased testing if used indiscriminately among patients who otherwise do not require testing. Some studies have suggested that incidence of ICA and revascularization is increased after CTA in the ED, of unclear long-term clinical significance. CTA has a unique advantage of diagnosing extensive nonobstructive CAD, which has prognostic significance, and is not detected by traditional diagnostic tests for assessment of acute chest pain. CTA clearly offers potential to reduce ED crowding and cost, although its ultimate impact on total hospital and health care system cost is not yet rigorously studied.
references
1. Pitts SR, Niska RW, Xu J, Burt CW. National Hospital Ambulatory Medical Care Survey: 2006 emergency department summary. Natl Health Stat Rep; 2008: 1e38.
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2. Bhuiya FA, Pitts SR, McCaig LF. Emergency department visits for chest pain and abdominal pain: United states, 1999-2008. NCHS Data Brief; 2010:1e8. 3. Owens PL, Barrett ML, Gibson TB, Andrews RM, Weinick RM, Mutter RL. Emergency department care in the United States: a profile of national data sources. Ann Emerg Med. 2010;56:150e165. 4. Rubinshtein R, Halon DA, Gaspar T, et al. Usefulness of 64slice cardiac computed tomographic angiography for diagnosing acute coronary syndromes and predicting clinical outcome in emergency department patients with chest pain of uncertain origin. Circulation. 2007;115:1762e1768. 5. Pope JH, Aufderheide TP, Ruthazer R, et al. Missed diagnoses of acute cardiac ischemia in the emergency department. N Engl J Med. 2000;342:1163e1170. 6. Launbjerg J, Fruergaard P, Hesse B, Jorgensen F, Elsborg L, Petri A. Long-term risk of death, cardiac events and recurrent chest pain in patients with acute chest pain of different origin. Cardiology. 1996;87:60e66. 7. Amsterdam EA, Kirk JD, Bluemke DA, et al. Testing of low-risk patients presenting to the emergency department with chest pain: a scientific statement from the American Heart Association. Circulation. 2010;122:1756e1776. 8. Hollander JE, Robey JL, Chase MR, Brown AM, Zogby KE, Shofer FS. Relationship between a clear-cut alternative noncardiac diagnosis and 30-day outcome in emergency department patients with chest pain. Acad Emerg Med. 2007;14:210e215. 9. Hulten E, Pickett C, Bittencourt MS, et al. Outcomes after coronary computed tomography angiography in the emergency department: a systematic review and metaanalysis of randomized, controlled trials. J Am Coll Cardiol. 2013;61(8):880e892. 10. Moshage WE, Achenbach S, Seese B, Bachmann K, Kirchgeorg M. Coronary artery stenoses: three-dimensional imaging with electrocardiographically triggered, contrast agent-enhanced, electron-beam CT. Radiology. 1995;196:707e714. 11. Ghoshhajra BB, Engel LC, Major GP, et al. Evolution of coronary computed tomography radiation dose reduction at a tertiary referral center. Am J Med. 2012;125:764e772. 12. Abbara S, Arbab-Zadeh A, Callister TQ, et al. SCCT guidelines for performance of coronary computed tomographic angiography: a report of the Society of Cardiovascular Computed Tomography Guidelines Committee. J Cardiovasc Comput Tomogr. 2009;3:190e204. 13. Hausleiter J, Meyer T, Hermann F, et al. Estimated radiation dose associated with cardiac CT angiography. JAMA. 2009;301:500e507. 14. Hausleiter J, Meyer TS, Martuscelli E, et al. Image quality and radiation exposure with prospectively ECG-triggered axial scanning for coronary CT angiography: the multicenter, multivendor, randomized PROTECTION-III study. JACC Cardiovasc Imaging. 2012;5:484e493. 15. Chinnaiyan KM, Bilolikar AN, Walsh E, et al. CT dose reduction using prospectively triggered or fast-pitch spiral technique employed in cardiothoracic imaging (the CT dose study). J Cardiovasc Comput Tomogr. 2014;8:205e214. 16. Min JK, Dunning A, Lin FY, et al. Age- and sex-related differences in all-cause mortality risk based on coronary computed tomography angiography findings results from the International Multicenter CONFIRM (Coronary CT Angiography Evaluation for Clinical Outcomes: An International Multicenter Registry) of 23,854 patients without known coronary artery disease. J Am Coll Cardiol. 2011;58:849e860.
17. Bittencourt MS, Hulten E, Ghoshhajra B, et al. Prognostic value of nonobstructive and obstructive coronary artery disease detected by coronary computed tomography angiography to identify cardiovascular events. Circ Cardiovasc Imaging. 2014;7:282e291. 18. Taylor AJ, Cerqueira M, Hodgson JM, et al. ACCF/SCCT/ACR/ AHA/ASE/ASNC/NASCI/SCAI/SCMR 2010 appropriate use criteria for cardiac computed tomography. A report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, the Society of Cardiovascular Computed Tomography, the American College of Radiology, the American Heart Association, the American Society of Echocardiography, the American Society of Nuclear Cardiology, the North American Society for Cardiovascular Imaging, the Society for Cardiovascular Angiography and Interventions, and the Society for Cardiovascular Magnetic Resonance. J Cardiovasc Comput Tomogr. 2010;4:407.e401e407.e433. 19. Leipsic J, Abbara S, Achenbach S, et al. SCCT guidelines for the interpretation and reporting of coronary CT angiography: a report of the Society of Cardiovascular Computed Tomography Guidelines Committee. J Cardiovasc Comput Tomogr. 2014;8:342e358. 20. Raff GL, Chinnaiyan KM, Cury RC, et al. SCCT guidelines on the use of coronary computed tomographic angiography for patients presenting with acute chest pain to the emergency department: a Report of the Society of Cardiovascular Computed Tomography Guidelines Committee. J Cardiovasc Comput Tomogr. 2014;8(4):254e271. 21. Maroules CD, Blaha MJ, El-Haddad MA, Ferencik M, Cury RC. Establishing a successful coronary CT angiography program in the emergency department: official writing of the Fellow and Resident Leaders of the Society of Cardiovascular Computed Tomography (FiRST). J Cardiovasc Comput Tomogr. 2013;7:150e156. 22. Villines TC, Hulten EA, Shaw LJ, et al. Prevalence and severity of coronary artery disease and adverse events among symptomatic patients with coronary artery calcification scores of zero undergoing coronary computed tomography angiography: results from the CONFIRM (Coronary CT Angiography Evaluation for Clinical Outcomes: An International Multicenter) registry. J Am Coll Cardiol. 2011;58:2533e2540. 23. Hulten E, Bittencourt MS, Ghoshhajra B, et al. Incremental prognostic value of coronary artery calcium score versus CT angiography among symptomatic patients without known coronary artery disease. Atherosclerosis. 2014;233:190e195. 24. Greenland P, Bonow RO, Brundage BH, et al. ACCF/AHA 2007 clinical expert consensus document on coronary artery calcium scoring by computed tomography in global cardiovascular risk assessment and in evaluation of patients with chest pain: a report of the American College of Cardiology Foundation Clinical Expert Consensus Task Force (ACCF/AHA Writing Committee to Update the 2000 Expert Consensus Document on Electron Beam Computed Tomography) developed in collaboration with the Society of Atherosclerosis Imaging and Prevention and the Society of Cardiovascular Computed Tomography. J Am Coll Cardiol. 2007;49:378e402. 25. Skinner JS, Smeeth L, Kendall JM, Adams PC, Timmis A. NICE guidance. Chest pain of recent onset: assessment and diagnosis of recent onset chest pain or discomfort of suspected cardiac origin. Heart. 2010;96:974e978. 26. Greenland P, Bonow RO. How low-risk is a coronary calcium score of zero? The importance of conditional probability. Circulation. 2008;117:1627e1629.
J o u r n a l o f C a r d i o v a s c u l a r C o m p u t e d T o m o g r a p h y 8 ( 2 0 1 4 ) 3 5 9 e3 6 7
27. Mowatt G, Cook JA, Hillis GS, et al. 64-slice computed tomography angiography in the diagnosis and assessment of coronary artery disease: systematic review and metaanalysis. Heart. 2008;94:1386e1393. 28. Hulten EA, Carbonaro S, Petrillo SP, Mitchell JD, Villines TC. Prognostic value of cardiac computed tomography angiography: a systematic review and meta-analysis. J Am Coll Cardiol. 2011;57:1237e1247. 29. Goldstein JA, Chinnaiyan KM, Abidov A, et al. The CT-STAT (Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patients to Treatment) trial. J Am Coll Cardiol. 2011;58:1414e1422. 30. Goldstein JA, Gallagher MJ, O’Neill WW, Ross MA, O’Neil BJ, Raff GL. A randomized controlled trial of multi-slice coronary computed tomography for evaluation of acute chest pain. J Am Coll Cardiol. 2007;49:863e871. 31. Hoffmann U, Truong QA, Schoenfeld DA, et al. Coronary CT angiography versus standard evaluation in acute chest pain. N Engl J Med. 2012;367:299e308. 32. Litt HI, Gatsonis C, Snyder B, et al. CT angiography for safe discharge of patients with possible acute coronary syndromes. N Engl J Med. 2012;366:1393e1403. 33. Poon M, Cortegiano M, Abramowicz AJ, et al. Associations between routine coronary computed tomographic angiography and reduced unnecessary hospital admissions, length of stay, recidivism rates, and invasive coronary angiography in the emergency department triage of chest pain. J Am Coll Cardiol. 2013;62:543e552. 34. Schlett CL, Banerji D, Siegel E, et al. Prognostic value of CT angiography for major adverse cardiac events in patients with acute chest pain from the emergency department: 2year outcomes of the ROMICAT trial. JACC Cardiovasc Imaging. 2011;4:481e491. 35. Nasis A, Meredith IT, Sud PS, Cameron JD, Troupis JM, Seneviratne SK. Long-term outcome after CT Angiography in
36.
37.
38.
39.
40.
41.
42.
367
Patients with Possible Acute Coronary Syndrome. Radiology. 2014;272(3):674e682. Hulten E, Bittencourt MS, Singh A, et al. Coronary artery disease detected by coronary computed tomographic angiography is associated with intensification of preventive medical therapy and lower low-density lipoprotein cholesterol. Circ Cardiovasc Imaging. 2014;7(4):629e638. Einstein AJ, Henzlova MJ, Rajagopalan S. Estimating risk of cancer associated with radiation exposure from 64-slice computed tomography coronary angiography. JAMA. 2007;298:317e323. Schull MJ, Vermeulen M, Slaughter G, Morrison L, Daly P. Emergency department crowding and thrombolysis delays in acute myocardial infarction. Ann Emerg Med. 2004;44:577e585. Henzler T, Gruettner J, Meyer M, et al. Coronary computed tomography and triple rule out CT in patients with acute chest pain and an intermediate cardiac risk for acute coronary syndrome: part 2: economic aspects. Eur J Radiol. 2013;82:106e111. Miller AH, Pepe PE, Peshock R, et al. Is coronary computed tomography angiography a resource sparing strategy in the risk stratification and evaluation of acute chest pain? Results of a randomized controlled trial. Acad Emerg Med. 2011;18:458e467. Hulten E, Goehler A, Bittencourt MS, et al. Cost and resource utilization associated with use of computed tomography to evaluate chest pain in the emergency department: the Rule Out Myocardial Infarction Using Computer Assisted Tomography (ROMICAT) study. Circ Cardiovasc Qual Outcomes. 2013;6:514e524. Shreibati JB, Baker LC, Hlatky MA. Association of coronary CT angiography or stress testing with subsequent utilization and spending among Medicare beneficiaries. JAMA. 2011;306:2128e2136.
