|Current Concepts in Cardiac CT Angiography for Patients With Acute Chest Pain.|
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|PMID: 21217929 Owner: NLM Status: PubMed-not-MEDLINE|
|This article presents specific examples of delayed diagnosis of acute coronary syndrome, acute aortic dissection, and pulmonary embolism resulting from evaluating patients with nonspecific acute chest pain who did not undergo immediate dedicated coronary CT angiography (CTA) or triple rule-out protocol (TRO). These concrete examples of delayed diagnosis may advance the concept of using cardiac CTA (i.e., dedicated coronary CTA versus TRO) to triage patients with nonspecific acute chest pain. This article also provides an overall understanding of how to choose the most appropriate examination based on the specific clinical situation in the emergency department (i.e., dedicated coronary CTA versus TRO versus dedicated pulmonary or aortic CTA), how to interpret the CTA results, and the pros and cons of biphasic versus triphasic administration of intravenous contrast material during TRO examination. A precise understanding of various cardiac CTA protocols will improve the diagnostic performance of radiologists while minimizing hazards related to radiation exposure and contrast use.|
|Seung Min Yoo; Ji Young Rho; Hwa Yeon Lee; In Sup Song; Jae Youn Moon; Charles S White|
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|Type: Journal Article Date: 2010-11-30|
|Title: Korean circulation journal Volume: 40 ISSN: 1738-5555 ISO Abbreviation: Korean Circ J Publication Date: 2010 Nov|
|Created Date: 2011-01-10 Completed Date: 2011-07-14 Revised Date: 2013-05-29|
Medline Journal Info:
|Nlm Unique ID: 101247141 Medline TA: Korean Circ J Country: Korea (South)|
|Languages: eng Pagination: 543-9 Citation Subset: -|
|Department of Diagnostic Radiology, CHA Medical University Hospital, Seongnam, Korea.|
|APA/MLA Format Download EndNote Download BibTex|
Journal ID (nlm-ta): Korean Circ J
Journal ID (publisher-id): KCJ
Publisher: The Korean Society of Cardiology
Copyright © 2010 The Korean Society of Cardiology
Print publication date: Month: 11 Year: 2010
Electronic publication date: Day: 30 Month: 11 Year: 2010
Volume: 40 Issue: 11
First Page: 543 Last Page: 549
PubMed Id: 21217929
|Current Concepts in Cardiac CT Angiography for Patients With Acute Chest Pain|
|Seung Min Yoo, MD1|
|Ji Young Rho, MD1|
|Hwa Yeon Lee, MD2|
|In Sup Song, MD2|
|Jae Youn Moon, MD3|
|Charles S White, MD4|
1Department of Diagnostic Radiology, CHA Medical University Hospital, Seongnam, Korea.
2Department of Diagnostic Radiology, Chung-Ang University College of Medicine, Seoul, Korea.
3Department of Cardiology, CHA Medical University Hospital, Seongnam, Korea.
4Department of Diagnostic Radiology, University of Maryland, Baltimore, Maryland, USA.
|Correspondence: Correspondence: Charles S White, MD, Department of Diagnostic Radiology, University of Maryland, 22S South Greene Street, Baltimore, MD 21201, USA. Tel: 1-410-328-3477, Fax: 1-410-328-0641, email@example.com
The one-stop CT examination for chest pain, the so-called "triple rule-out (TRO) protocol" used to diagnose acute coronary syndrome (ACS), pulmonary embolism (PE), and acute aortic syndrome (AAS) is increasingly being performed in many institutions equipped with 64-slice multi-detector CT (MDCT) or newer generation MDCT scanners. Although there have been many articles dealing with TRO, these studies did not provide the specific examples of delayed diagnosis in assessing patients with nonspecific acute chest pain who do not undergo immediate cardiac CT angiography (CTA) (i.e., dedicated coronary CTA and TRO study).1-10) In addition, there is limited information regarding overall concepts such as how to choose the optimal examination (i.e., dedicated coronary CTA versus TRO versus dedicated PE or aortic CTA) based on the specific presentation to the emergency department (ED), how to interpret the results of TRO, and the pros and cons of biphasic versus triphasic administration of intravenous contrast material during TRO examination. This article focuses on these issues.
The cost to manage patients with nonspecific acute chest pain is 10 billion dollars in the United States annually.1), 2) However, only 15-25% of hospitalized patients with nonspecific acute chest pain prove to have ACS.11) In addition, 2-5% of all ACS is missed with the conventional chest pain protocol, even though ED physicians have a low threshold for admitting the patients with unspecified acute chest pain (Fig. 1).1), 2)
The diagnostic delay of AAS is also a serious problem worldwide. According to studies, the annual incidence of ACS, PE, and AAS is 440, 69, and 3 per 100,000 individuals, respectively.12), 13) As AAS is much less frequent compared with ACS and there is substantial overlap in clinical symptoms and signs between ACS and AAS, ED physicians tend to mistake AAS for ACS, and the reverse also occurs. One study reported that up to 39% of aortic dissections have a diagnostic delay of at least 24 hours (Fig. 2).14) Because the highest mortality of AAS occurs within the first 48 hours after onset of symptoms,15) there has been great interest in developing new approaches to reduce diagnostic delay or missed diagnosis. PE also has a nonspecific clinical presentation, rendering its immediate diagnosis difficult (Fig. 3).
The diagnosis of ACS is straightforward if a patient has at least two of following findings: typical chest pain; elevated serum cardiac enzymes; or typical electrocardiography (ECG) changes. In these patients, coronary catheterization should be immediately performed without further non-invasive imaging studies. However, the diagnosis of ACS can be difficult because the nature of acute chest pain is often nonspecific, serum cardiac enzymes may remain normal within the first 6 hours after onset of symptoms, and ECG changes are frequently nonspecific.
Serial follow-up of ECG and serum cardiac enzymes over 12-24 hours with or without performing bicycle stress testing or radionuclide stress perfusion imaging is the mainstay of the conventional protocol to triage patients with nonspecific acute chest pain. However, the conventional protocol is not cost-effective for the diagnosis of ACS.1), 2)
Furthermore, the diagnosis of unstable angina can be delayed with conventional protocols because serum cardiac enzymes are not elevated in patients with unstable angina.
When performing a diagnostic work up in patients with nonspecific acute chest pain, we have encountered occasions in which serial coronary angiography and chest CT are negative (Fig. 4). The final diagnosis in these cases may be esophageal, musculo-skeletal, or cryptogenic in origin. Such patients are the best candidates for TRO studies. Rogg et al.16) reported performing multiple diagnostic examinations (e.g., coronary angiography and dedicated PE CTA) to exclude at least two of ACS, PE, or AAS in 139 cases (22%) among 626 cases presenting with acute chest pain. The specific multiple examinations for combinations of ACS and PE, ACS and AAS, and ACS, PE, and AAS were performed in 121 (19%), 14 (2%), and 4 cases (0.6%), respectively.16)
Based on this investigation, patients with clinical concern for all three major acute chest pain diagnoses (i.e., ACS, PE, and AAS) are rare. In contrast, clinical scenarios where exclusion of either ACS and PE or ACS and AAS is necessary are fairly common.
As suggested in the previous section, the choice of MDCT protocol depends greatly on the clinical presentation. Dedicated coronary CTA is generally indicated in patients with acute chest pain with normal or nonspecific ECG changes and normal initial cardiac enzyme levels.2) TRO is associated with increased radiation exposure due to an extended z-axis compared with dedicated coronary CTA (Fig. 5). With respect to PE, one study reported that low clinical probability of PE (i.e., Well's criteria ≤4) supported by a negative D-dimer test was associated with a low 3-month incidence of a venous thrombo-embolic event (0.5%).17) With respect to AAS, von Kodolitsch et al.18) indicated that the probability of aortic dissection is low in patients lacking three variables (pulse or blood pressure differentials, mediastinal widening on chest radiography, and severe chest pain with sudden onset or ripping nature or both). Therefore, if the clinical pretest probability of PE and AAS is low and ACS is the only major concern, a dedicated coronary CTA is the most appropriate examination.
In contrast, if the clinical pretest probability of either PE or AAS is high, a dedicated PE or aortic CTA should be performed because these can be obtained without ECG-gating (i.e., lower radiation exposure compared with dedicated coronary CTA or TRO). Gallagher and Raff19) have suggested that most central PE and aortic dissections can be diagnosed with dedicated coronary CTA because the field of view of dedicated coronary CTA includes much of the lower two-thirds of the thorax. Specifically, the entire thoracic aorta, except the arch and both main pulmonary arteries, is largely located within the field of view of dedicated coronary CTA. Therefore, TRO may be restricted to patients in whom the pretest probability of ACS and PE or AAS is intermediate. The TRO has some advantages in evaluating PE and AAS compared with an aortic CTA or dedicated PE study because of ECG-gating, namely more precise evaluation of aortic valve and coronary artery involvement by a dissection flap and better demonstration of PE in the paracardiac pulmonary arteries.5)
There is concern that similar to the experience with PE CTA,13) TRO with an even higher radiation dose will be overused in the ED setting. Contraindications to the TRO protocol include clinical instability, severe arrhythmia, renal failure, allergy to contrast material, use in young women, and a high thrombolysis in myocardial infarction score (score ≥5). Rapid heart rate (>65 beats/min) is a relative contraindication to TRO on 64-slice MDCT because coronary artery motion artifact often impairs precise evaluation at higher heart rates.3) However, with the faster temporal resolution of newer scanners, such as the 128-slice dual source CT (75 msec), diagnostic imaging quality of the entire coronary arteries may be feasible, even with heart rates up to 75 beats/min and beyond. Finally, as severe coronary artery calcification may compromise evaluation of coronary artery stenosis, a high coronary artery calcium score (>1,000) can also be a relative contraindication of TRO.19)
It is best to have the CT room located in or near the ED because patients with acute chest pain have the potential to be unstable. As noted above, it is important to keep the patient's heart rate low to enable TRO imaging of optimal quality. This is generally done with beta-blockers, using one of two methods. The first is to administer an oral beta-blocker in the ED, and then, if the patient's heart rate remains high (>65 beats/min) in the CT room, an intravenous beta-blocker is also administered. In the second approach, an intravenous beta-blocker is initially used to control heart rate.20) The latter approach has the advantage of reducing the time for heart rate control but requires a physician to be present for the CT scan.
Once the examination is performed, rapid interpretation is mandatory to facilitate an immediate triage decision in patients with acute chest pain. Although advances in 3-dimensional software technology facilitate multi-planar reconstruction including volume rendering imaging, trans-axial CT images with or without curved multi-planar reformatted images are primarily used to establish the extent of coronary artery stenosis in patients with acute chest pain. When an experienced cardiac radiologist reads the TRO by this method, it can take approximately 30 minutes from the patient's arrival in the CT room to the final reading. For 24-hour coverage, remote reading may be a more cost-effective way to handle final interpretations, although on-site personnel with cardiac imaging training is the best option. For example, a remote reading capability is now provided by various venders and allows radiologists to interpret a TRO study from anywhere. Specific technical aspects of cardiac CTA protocols in patients with acute chest pain are not provided in this article because many previous articles have thoroughly discussed these points.1-3), 5-10), 19)
The recent ROMICAT trial reported that the negative predictive value for excluding ACS is 100% and showed no short-term major cardiac events in patients with acute chest pain who had no plaque on dedicated coronary CTA.21) Accordingly, it was possible to discharge these patients immediately. It should be stressed that there were seven cases of ACS (7/31, 23%) with non-obstructive coronary artery stenosis (<50%) on coronary CTA. This may have been caused by inaccuracies in the coronary CTAs to evaluate distal small coronary braches (i.e., <2 mm in diameter).22) It may also have resulted from embolism into the coronary artery, sustained spasm of coronary artery, or spontaneous thrombolysis.23), 24) Therefore, patients with acute chest pain and non-obstructive coronary artery stenosis (<50%) on coronary CTA should not be discharged immediately and may require serial ECG and serum cardiac enzyme follow-up.
Immediate coronary angiography is mandatory in patients with acute chest pain and critical coronary artery stenosis (>70%) (Fig. 6). For patients with indeterminate coronary artery stenosis (50-70%) or non-diagnostic coronary CTA caused by coronary motion artifact, severe calcified plaque, or low contrast-noise ratio, radionuclide stress perfusion imaging is a possible option to further triage these patients.25) However, if a patient has a positive result on radionuclide stress perfusion imaging, the total radiation exposure becomes quite high because coronary angiography is generally performed next. This is a drawback in using CT as part of the triage system to evaluate patients with acute chest pain. For this reason, alternative modalities that do not involve radiation exposure, such as stress echocardiography or stress MRI, may be considered to mitigate high radiation exposure in this subgroup of patients with acute chest pain, although there has not been a well-designed study addressing this scenario.
In contrast to dedicated coronary CTA, the pulmonary arteries, as well as the aorta and coronary arteries, must be well opacified in the TRO protocol to simultaneously evaluate these arteries. Therefore, a different approach to performing the CTA examination is necessary for TRO.2) In performing a TRO study with 64-slice MDCT, the intravenous administration of contrast material during the scanning time (approximately 10-15 seconds) plus a trigger delay (about 5 seconds) is used to opacify the aorta and coronary arteries. Because the pulmonary transit time (the time for contrast material to travel from pulmonary circulation to left circulation) is approximately 10 seconds, the total time necessary to administer the contrast material in TRO is approximately 25-30 seconds.26) This time is shorter for newer scanners such as 256-slice MDCT or 128-dual source CT because of shorter scan times, which permits a decrease in the amount of contrast material used (State the advantage of this to the patient).
Because of the relatively high amount of contrast material (i.e., flow rate of 4-5 mL/s) with iodine concentration of 350-400 mg/mL used in many institutions, irrespective of patient's body mass index (BMI), special care should be taken to restrict the amount of contrast material for emergent cardiac CTA, especially in slim patients. Iodine concentrations of 0.5 g/kg are sufficient to opacify the target vessels in TRO.4)
There are two methods to administer contrast material in a TRO protocol, the biphasic and triphasic method.1), 4-7) In the biphasic method, there are two phases during which 100% contrast material and saline flush are administered consecutively. In the triphasic method, a third phase is added consisting of a mixture of contrast material and saline between the first and last phases. The triphasic method has the advantage that there is less streak artifact within the right coronary artery caused by a high concentration of contrast material in the right atrium or ventricle compared with biphasic method. However, the triphasic method may lead to poorer contrast enhancement within the pulmonary artery because the pulmonary circulation is opacified by dilute contrast material during the second phase, so that a PE may be missed. Although there may be cases which have streak artifact through the right coronary artery with a biphasic administration of contrast material, streak artifact severe enough to disturb the evaluation of the right coronary artery appears to be rare with TRO using the biphasic method (Fig. 7).
Every possible strategy should be used to reduce radiation exposure associated with TRO. ECG-gated tube pulsing in which the radiation dose is automatically reduced in the systolic phase is one promising method which makes it possible to reduce the total radiation dose up to 50%.1), 2), 27), 28) ECG-gated tube pulsing is the best option to reduce radiation dose in an MDCT scanner that does not offer a "step and shoot method" (i.e., coronary CTA performed by prospective gating).
BMI-based kV and tube current should be used to reduce radiation dose whenever possible. Lower kV and tube current (e.g., 100 kV and 450 mA) are often sufficient to obtain diagnostic image quality in slim patients (BMI less than 25 kg/m2).29)
Recent MDCT scanners are equipped with prospective gating capabilities. With prospective gating, radiation is emitted only during a targeted time period, usually a mid-diastolic phase.29-31) One study reported that this method has better resolution compared with retrospectively gated image, because the CT table does not move while scanning is being performed (i.e., conventional versus spiral acquisition).29) However, prospective gating cannot be used in patients with an irregular or fast heart rate. In addition, no information about cardiac function is obtained with prospective gating because only a part of the cardiac cycle is imaged. Nevertheless, the radiation dose savings of prospective gating is considerable compared with retrospective gating with a higher radiation dose.1), 32), 33) According to one study using 64-slice MDCT, the average radiation dose of TRO using prospective gating was 9.2±2.2 mSv (BMI=28±5 kg/m2).7) In another study, the radiation dose of dedicated coronary CTA using prospective gating was less than 3.0 mSv (1.1-3.0 mSv) with lower BMI patients (BMI=26.1±4.0 kg/m2).29) Therefore, TRO can be performed with radiation exposures in the 6-8 mSv range in non-obese patients on 64-slice MDCT.
TRO is expected to be more widely used for patients with nonspecific acute chest pain because it can be performed with lower radiation exposure (<5 mSv) using the recently released 128-dual source MDCT if the patient's heart rate is regular and slow. The scanning time of TRO with this scanner is approximately one second. Further advances in temporal resolution of MDCT scanners may increase the number of patients who can undergo radiation-sparing prospectively gated TRO examinations and achieve a sufficient imaging quality. Because various MDCT scanners with different capabilities (64, 128, 256, and 320-slice MDCT) are used for TRO, the radiation dose and utilization of contrast material should be individualized according to the body configuration of the individual patient and the scanner type.
Various CT protocols exist for evaluating patients with nonspecific acute chest pain. Accordingly, the choice of an optimal CT examination should be individualized according to the specific clinical presentation. To avoid unnecessary radiation exposure and contrast use, it is advisable to restrict the TRO protocol to patients in whom the pretest probability of ACS and PE or AAS is intermediate.
|1.||Bastarrika G,Thilo C,Headden GF,Zwerner PL,Costello P,Schoepf UJ. Cardiac CT in the assessment of acute chest pain in the emergency departmentAJR Am J RoentgenolYear: 200919339740919620436|
|2.||Lee HY,Yoo SM,White CS. Coronary CT angiography in emergency department patients with acute chest pain: triple rule-out protocol versus dedicated coronary CT angiographyInt J Cardiovasc ImagingYear: 20092531932618853277|
|3.||Halpern EJ. Triple rule-out CT angiography for evaluation of acute chest pain and possible acute coronary syndromeRadiologyYear: 200925233234519703877|
|4.||Johnson TR,Nikolaou K,Wintersperger BJ,et al. Optimization of contrast material administration for electrocardiogram-gated computed tomographic angiography of the chestJ Comput Assist TomogrYear: 20073126527117414765|
|5.||Frauenfelder T,Appenzeller P,Karlo C,et al. Triple rule-out CT in the emergency department: protocols and spectrum of imaging findingsEur RadiolYear: 20091978979919015860|
|6.||Litmanovich D,Zamboni GA,Hauser TH,Lin PJ,Clouse ME,Raptopoulos V. ECG-gated chest CT angiography with 64-MDCT and triphasic IV contrast administration regimen in patients with acute nonspecific chest painEur RadiolYear: 20081830831717763855|
|7.||Shuman WP,Branch KR,May JM,et al. Whole-chest 64-MDCT of emergency department patients with nonspecific chest pain: radiation dose and coronary artery image quality with prospective ECG triggering versus retrospective ECG gatingAJR Am J RoentgenolYear: 20091921662166719457832|
|8.||Johnson TR,Nikolaou K,Becker A,et al. Dual-source CT for chest pain assessmentEur RadiolYear: 20081877378018034246|
|9.||Schertler T,Scheffel H,Frauenfelder T,et al. Dual-source computed tomography in patients with acute chest pain: feasibility and image qualityEur RadiolYear: 2007173179318817851666|
|10.||Takakuwa KM,Halpern EJ. Evaluation of a "triple rule-out" coronary CT angiography protocol: use of 64-Section CT in low-to-moderate risk emergency department patients suspected of having acute coronary syndromeRadiologyYear: 200824843844618641247|
|11.||Pozen MW,D'Agostino RB,Selker HP,Sytkowski PA,Hood WB Jr. A predictive instrument to improve coronary-care-unit admission practices in acute ischemic heart disease. A prospective multicenter clinical trialN Engl J MedYear: 1984310127312786371525|
|12.||Hagan PG,Nienaber CA,Isselbacher EM,et al. The International Rregistry of Acute Aortic Dissection (IRAD): new insights into an old diseaseJAMAYear: 200028389790310685714|
|13.||Abcarian PW,Sweet JD,Watabe JT,Yoon HC. Role of a quantitative D-dimer assay in determining the need for CT angiography of acute pulmonary embolismAJR Am J RoentgenolYear: 20041821377138115149977|
|14.||Klompas M. Does this patient have an acute thoracic aortic dissection?JAMAYear: 20022872262227211980527|
|15.||Viljanen T. Diagnostic difficulties in aortic dissection. Retrospective study of 89 surgically treated patientsAnn Chir GynaecolYear: 1986753283323579193|
|16.||Rogg JG,Neve JW,Huang C,et al. The triple work-up for emergency department patients with acute chest pain: how often does it occur?J Emerg MedYear: 2008 [Epub ahead of print].|
|17.||van Belle A,Büller HR,Huisman MV,et al. Effectiveness of managing suspected pulmonary embolism using an algorithm combining clinical probability, D-dimer testing, and computed tomographyJAMAYear: 200629517217916403929|
|18.||von Kodolitsch Y,Schwartz AG,Nienaber CA. Clinical prediction of acute aortic dissectionArch Intern MedYear: 20001602977298211041906|
|19.||Gallagher MJ,Raff GL. Use of multislice CT for the evaluation of emergency room patients with chest pain: the so-called "triple rule-out"Catheter Cardiovasc IntervYear: 200871929918098208|
|20.||Pannu HK,Alvarez W Jr,Fishman EK. Beta-blockers for cardiac CT: a primer for the radiologistAJR Am J RoentgenolYear: 20061866 Suppl 2S341S34516714607|
|21.||Hoffmann U,Bamberg F,Chae CU,et al. Coronary computed tomography angiography for early triage of patients with acute chest pain: the ROMICAT (Rule Out Myocardial Infarction using Computer Assisted Tomography) trialJ Am Coll CardiolYear: 2009531642165019406338|
|22.||Hamon M,Biondi-Zoccai GC,Malagutti P,et al. Diagnostic performance of multislice spiral computed tomography of coronary arteries as compared with conventional invasive coronary angiography: a meta-analysisJ Am Coll CardiolYear: 2006481896191017084268|
|23.||Dokainish H,Pillai M,Murphy SA,et al. Prognostic implications of elevated troponin in patients with suspected acute coronary syndrome but no critical epicardial coronary disease: a TACTICS-TIMI-18 substudyJ Am Coll CardiolYear: 200545192415629367|
|24.||Patel MR,Chen AY,Peterson ED,et al. Prevalence, predictors, and outcomes of patients with non-ST-segment elevation myocardial infarction and insignificant coronary disease: results from the can rapid risk stratification of unstable angina patients suppress adverse outcomes with early implementation of the ACC/AHA guidelines (CRUSADE) initiativeAm Heart JYear: 200615264164716996828|
|25.||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 painJ Am Coll CardiolYear: 20074986387117320744|
|26.||Fleischmann D,Lin M. Remy-Jardin M,Remy JContrast medium utilizationIntegrated Cardiothoracic Imaging with MDCTYear: 2008Berlin, GermanySpringer5363|
|27.||Jakobs TF,Becker CR,Ohnesorge B,et al. Multislice helical CT of the heart with retrospective ECG gating: reduction of radiation exposure by ECG-controlled tube current modulationEur RadiolYear: 2002121081108611976849|
|28.||Poll LW,Cohnen M,Brachten S,Ewen K,Mödder U. Dose reduction in multi-slice CT of the heart by use of ECG-controlled tube current modulation ("ECG pulsing"): phantom measurementsRofoYear: 20021741500150512471520|
|29.||Husmann L,Valenta I,Gaemperli O,et al. Feasibility of low-dose coronary CT angiography: first experience with prospective ECG-gatingEur Heart JYear: 20082919119718089704|
|30.||Stolzmann P,Scheffel H,Schertler T,et al. Radiation dose estimates in dual-source computed tomography coronary angiographyEur RadiolYear: 20081859259917909816|
|31.||Scheffel H,Alkadhi H,Leschka S,et al. Low-dose CT coronary angiography in the step-and-shoot mode: diagnostic performanceHeartYear: 2008941132113718519548|
|32.||Hirai N,Horiguchi J,Fujioka C,et al. Prospective versus retrospective ECG-gated 64-detector coronary CT angiography: assessment of image quality, stenosis, and radiation doseRadiologyYear: 200824842443018574140|
|33.||Ketelsen D,Luetkhoff MH,Thomas C,et al. Estimation of the radiation exposure of a chest pain protocol with ECG-gating in dual-source computed tomographyEur RadiolYear: 200919374118648818|
Keywords: Tomography, X-ray computed, Acute coronary syndrome, Acute aortic syndrome, Pulmonary embolism.
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