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Non-gated high-pitch computed tomography aortic angiography: Myocardial perfusion defects in patients with suspected aortic dissection
Journal of Cardiovascular Computed Tomography xxx (2017) 1e5
Contents lists available at ScienceDirect
Journal of Cardiovascular Computed Tomography journal homepage: www.JournalofCardiovascularCT.com
Research paper
Non-gated high-pitch computed tomography aortic angiography: Myocardial perfusion defects in patients with suspected aortic dissection Li-Ting Huang, M.D. a, Shih-Hung Chan, M.D. b, Chia-Chang Chuang, M.D. c, Yi-Shan Tsai, M.D. a, * a
Department of Diagnostic Radiology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, No.138, Sheng Li Road, Tainan, 704, Taiwan ROC Division of Cardiology, Department of Internal Medicine, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, No.138, Sheng Li Road, Tainan, 704, Taiwan ROC c Department of Emergency Medicine, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, No.138, Sheng Li Road, Tainan, 704, Taiwan ROC b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 9 January 2017 Received in revised form 20 March 2017 Accepted 11 April 2017 Available online xxx
Objectives: To investigate the diagnostic value of first-pass myocardial perfusion defects visualised in non-gated high-pitch computed tomography angiography (CTA) in patients admitted to the emergency department (ED) for suspected aortic dissection. Methods: We recruited 174 ED patients who underwent high-pitch CTA of the aorta because of suspected aortic dissection. We divided these patients into two groups (diseased and control groups) based on whether their clinical data fulfilled the third universal definition of acute myocardial infarction (AMI), specifically an increase in cardiac troponin (cTn) with at least one of the following: (a) symptoms of ischemia; (b) new ST-segment-T wave (ST-T) changes or new left bundle branch block (LBBB); (c) development of pathological Q wave; (d) new loss of viable myocardium or new regional wall motion abnormality; or (e) identification of an intracoronary thrombus by angiography or autopsy. Twenty-two patients with a clinical diagnosis of AMI were placed in the diseased group. Myocardial perfusion defects were evaluated qualitatively and quantitatively on the late arterial phase obtained 50 s post-threshold. Results: Of the 22 patients with a final diagnosis of AMI, visually identifiable perfusion defects were observed in 12 patients. The sensitivity, specificity, negative predictive value, and positive predictive value of any perfusion defect for predicting AMI were 54.6%, 94.7%, 93.5%, and 60.0%, respectively. Quantitative analysis indicated that CT attenuation was significantly lower within perfusion defects than within the normal myocardium (67.3 ± 29.5 HU vs. 92.8 ± 19.7 HU; p < 0.001). Conclusions: In patients with acute chest pain, the presence of myocardial perfusion defect observed on nongated high-pitch CTA of the aorta can be used to identify individuals with AMI with high specificity, but low sensitivity. © 2017 Published by Elsevier Inc. on behalf of Society of Cardiovascular Computed Tomography.
Keywords: Dual-source CT High pitch Myocardial perfusion Perfusion defect Myocardial infarction
1. Introduction Non-electrocardiogram (ECG)-gated contrast-enhanced computed tomography (CT) angiography (CTA) is available in most hospitals where patients with chest and/or back pain are admitted to the emergency department (ED).1 Mano et al.
* Corresponding author. E-mail address: [email protected] (Y.-S. Tsai).
investigated the role of perfusion defects in diagnosis of acute coronary syndrome in 154 consecutive patients admitted to the ED to differentiate acute aortic dissection from pulmonary thromboembolism (PE) by using non ECG-gated 64-slice CT. The results demonstrated a high sensitivity (93%) and negative predictive value (NPV, 98%) to identify acute myocardial infarction (AMI).1 Coronary CT angiography (coronary CTA) can detect coronary artery disease in patients with chest pain. The addition of CT perfusion (CTP) to coronary CTA improves its specificity and positive predictive value (PPV) regarding the presence of myocardial ischemia.2 The addition
http://dx.doi.org/10.1016/j.jcct.2017.04.003 1934-5925/© 2017 Published by Elsevier Inc. on behalf of Society of Cardiovascular Computed Tomography.
Please cite this article in press as: Huang L-T, et al., Non-gated high-pitch computed tomography aortic angiography: Myocardial perfusion defects in patients with suspected aortic dissection, Journal of Cardiovascular Computed Tomography (2017), http://dx.doi.org/10.1016/ j.jcct.2017.04.003
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L.-T. Huang et al. / Journal of Cardiovascular Computed Tomography xxx (2017) 1e5
of CTP to coronary CTA increases the sensitivity to identify acute coronary syndromes (ACS) from 77% to 90%.3 The demonstration of perfusion abnormalities in chest CT is difficult because the myocardium is less resolved in non-gated studies. With the second generation dual-source CT, the option to increase pitch above the traditional technical limit of 1.5, in single-source CT, has allowed to substantially reduce image acquisition time and to increase volume coverage.4 High-pitch dual-source CTA of the entire aorta without ECG synchronisation is feasible in a very short time period and renders motion-free imaging of the aorta.5 Although non-gated high-pitch aortic CTA has been established as an initial diagnostic imaging modality for acute aortic syndromes, its diagnostic value for detecting AMI in a population with suspected aortic dissection has not yet been investigated. This study determined the diagnostic value of first-pass myocardial perfusion defects visualized using non-gated high-pitch contrast-enhanced CTA in patients admitted to the ED for suspected acute aortic syndromes. 2. Methods 2.1. Patients This study was approved by the institutional review board of the hospital. All patients provided written informed consent for CT imaging. However, the requirement of informed consent was waived for retrospective chart review. We retrospectively recruited patients with acute chest pain who underwent non-gated highpitch CTA of the aorta to exclude acute aortic dissection in the ED from July 2010 to September 2014. We reviewed each medical chart to identify the final diagnosis for each admission. AMI diagnosis was confirmed by an attending physician or cardiologist according to the third universal definition of AMI released in 2012 by the ESC/ ACCF/AHA/WHF,6 which included a dynamic change of cardiac troponin (cTn) and at least one of the following: (a) symptoms of ischemia; (b) new ST-segment-T wave (ST-T) changes or new left bundle branch block (LBBB); (c) development of pathological Q wave; (d) new loss of viable myocardium or new regional wall motion abnormality; or (e) identification of an intracoronary thrombus by angiography or autopsy. Exclusion criteria were as follows: 1) history of coronary artery disease (CAD), 2) history of previous MI, 3) absence of ECG data at ED visit, 4) absence of two consecutive (within 24 h) cardiac troponin I (cTn-I) data at ED, and 5) poor imaging quality. We divided the recruited patients into two groups: the diseased group, comprising patients who had received a diagnosis of ST-elevation myocardial infarction (STEMI) or nonST-elevation myocardial infarction (NSTEMI), and a control group, comprising patients who had not received a diagnosis of STEMI or NSTEMI. 2.2. CT imaging protocol We used a high-pitch, 128-slice CT system (Definition Flash, Siemens, Forchheim, Germany) operated in single-source mode with a pitch of 2.0, collimation of 128 0.6 mm, rotation time of 0.28 s, tube potential of 120 kV, and 100e150 reference mAs. Data were acquired in the craniocaudal direction during a single breath hold. The imaging range extended from the upper thoracic aperture to the proximal femoral arteries. Patients were examined in the supine position. We injected 90 mL of an iodinated contrast material (iodine concentration of 400 mg/mL, Imeron 400, Bracco Imaging, Konstanz, Germany) at a flow rate of 3.5 cc/s by using an 18e20-G intravenous line followed by 50 mL of a saline chaser. CTA was automatically started based on a bolus-tracking measurement at the level of the ascending thoracic aorta at a threshold of 100 Hounsfield units (HU).The post-threshold delay scan for
early and late arterial phase was set to 13 s and 50 s, respectively. Transverse images were reconstructed at a 1.0-mm slice thickness with 0.7-mm increments by using a medium-soft convolution kernel (B30f) and a matrix size of 512 512. In addition, we reconstructed axial slices at a 5.0-mm thickness with 5.0-mm increment. 2.3. CT image analysis An experienced cardiac radiologist (YST, 14 years of experience) and a senior radiology resident (LTH, 3 years of experience) blinded to clinical and angiographic results jointly reviewed CTA of the aorta and reached consensus in cases of disagreement. Axial images reconstructed perpendicular to the long axis of the body were evaluated. The window width and centre of all images were set at 700 HU and 100 HU, respectively. Enhancement of the left ventricular myocardium was visually assessed on late arterial phase. According to previous studies, a perfusion defect was visually defined as a region of lower attenuation and/or wall thinning within the normally enhanced myocardium.7 Myocardial enhancement was measured in HU by circling the region of interest (ROIs) of approximately 10 mm2 within the perfusion defects, normal interventricular septum (IVS), and the paraspinal muscle at the level of T10, in three consecutive axial images. The average attenuation values were used for statistical analyses. DHU myocardium was calculated and defined as the enhancement difference between the normal IVS and the paraspinal muscle in the control group, and between the myocardial perfusion defect and paraspinal muscle in the diseased group. Myocardium ratio was defined as the IVS myocardium divided by the paraspinal muscle in the control group and the myocardial perfusion defect in the diseased group. Of the 174 image data sets, 20 were randomly analysed by a second observer to ensure interobserver reproducibility. 2.4. Statistical analysis Statistical analysis was performed using commercially available software (SPSS 17.0 for Windows; SPSS, Chicago, III). Continuous and categorical variables were expressed as medians ± standard deviations and percentages, respectively. The chi-square test was used for descriptive statistics. The independent t-test was used for evaluating the difference in average attenuation values and the adjusted attenuation value between the normal and infarcted regions. The receiver-operating characteristic (ROC) curves were constructed to assess the diagnostic accuracy of perfusion defects in AMI. Cut point estimates, 95% confidence interval (CI), and areas under the ROC curve (AUCs) were calculated. In addition, sensitivities and specificities at cut-off points were determined using the Youden index. A P value of <0.05 was considered statistically significant. Interrater reliability (IRR) was assessed using Kappa statistics. IRR was poor, fair, good, and excellent for Cronbach's alpha values < 0.40, between 0.40 and 0.59, between 0.60 and 0.74, and between 0.75 and 1.0, respectively.8 Intrarater reliability was evaluated using testeretest reliability. A Pearson correlation coefficient of >0.7 indicated good consistency.9 3. Results 3.1. Patients From July 2010 to September 2014, 618 patients visited the ED and underwent high-pitch CTA of the aorta because they were suspected to have acute aortic dissection. Of them, 174 were
Please cite this article in press as: Huang L-T, et al., Non-gated high-pitch computed tomography aortic angiography: Myocardial perfusion defects in patients with suspected aortic dissection, Journal of Cardiovascular Computed Tomography (2017), http://dx.doi.org/10.1016/ j.jcct.2017.04.003
L.-T. Huang et al. / Journal of Cardiovascular Computed Tomography xxx (2017) 1e5
recruited for final analysis after excluding 93 patients without ECG data, 342 patients without two consecutive c-TnI measurement results, 6 patients with a previous history of CAD and MI, and 3 patients with poor CTA imaging quality (Fig. 1). Based on clinical assessment, we identified 22 patients with AMI. The percentage of patients with diabetes and dyslipidaemia was significantly higher in the diseased group than in the control group (40.9% vs. 17.1%, P ¼ 0.020 and 50.0% vs. 12.5%, P < 0.001, respectively). Furthermore, the number of patients who underwent percutaneous coronary intervention was significantly higher in the diseased group than in the control group (Table 1). 3.2. Visual analysis results According to visual assessment, perfusion defects were present in CT in 12 patients with AMI (Fig. 2, DICOM File here). We recorded 10 false-negative and 8 false-positive cases, resulting in a sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of 54.6% (12/22), 94.7% (144/152), 93.5% (144/154), and 60.0% (12/20), respectively (Table 2).
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Table 1 Demographic data of the control and diseased groups. Control group N ¼ 152 Age 60.6 ± 16.8 Sex N(%) Female 50(32.9) Male 102(66.1) Hypertension N(%) 78(51.3) Diabetes N(%) 26(17.1) Dyslipidemia N(%) 19(12.5) PCI N(%) 6(4.0)
Diseased group N ¼ 22
P value
58.3 ± 13.4
0.542
6(27.3) 16(72.7)
0.777
13(59.1)
0.650
9(40.9)
0.020
11(50.0) 20(90.9)
0.001 <0.0001
Note. PCI ¼ percutaneous coronary intervention.
(Cronbach's alpha ¼ 0.956). The consistency of one observer's measurement of the myocardium in patients was good (Pearson correlation coefficient ¼ 0.98). 3.5. Radiation dose
3.3. Quantitative analysis results Quantitative analysis indicated that CT attenuation within perfusion defects was significantly lower than that within the normal myocardium (67.6 ± 29.5 HU vs. 92.2 ± 19.7 HU; P < 0.001). Furthermore, DHU myocardium and myocardium ratio were significantly lower in the diseased group than in the control group (13.5 ± 29.5 vs. 40.4 ± 21.7 HU; P < 0.001 and 1.27 ± 0.55 vs. 1.80 ± 0.48; P < 0.001, respectively; Table 3). ROC analyses demonstrated that the AUCs of DHU myocardium and myocardium ratio for predicting AMI were 0.75 (95% CI 0.68e0.81) and 0.75 (95% CI 0.67e0.81), respectively. The sensitivity and specificity for diagnosing AMI by using the optimised cut-off point of DHU myocardium (10.1 HU) were 54.6% and 95.4%, respectively, and those obtained using the optimised cut-off point of myocardium ratio (1.15) were 54.6% and 94.7%, respectively (Fig. 3). 3.4. Interobserver agreement and intrarater reliability The results of the two observers regarding the attenuation value of the myocardium in 20 patients exhibited excellent concordance
The average of the dose-length product provided by the CT system for estimating a radiation dose of each phase was 361.85 ± 169.77 mGy*cm. The effective radiation dose delivered in thoracoabdominal CTA was calculated using a method proposed by the European Working Group for Guidelines on Quality Criteria for CT.10 Because acquisitions of the chest, abdomen, and pelvis were performed using thoracoabdominal CTA, the mean of these regionspecific conversion coefficients (k ¼ 0.017 mSv/mGy*cm) was used as previously described.10 The average of the effective radiation dose of each phase in 174 patents was 6.15 ± 2.89 mSv. 4. Discussion The triage of patients with acute chest pain in the ED remains challenging, particularly in patients without changes in ECG or cardiac enzymes. Moreover, increased blood concentrations of troponin can also be observed in various other diseases such as sepsis, atrial fibrillation, heart failure, pulmonary embolism, myocarditis, myocardial contusion, and renal failure. Recently, ECGgated coronary CTA has been reported to play a major role from triage to treatment decisions in patients presenting with acute
Fig. 1. Flow chart of the selection process for patient enrolment in the final study.
Please cite this article in press as: Huang L-T, et al., Non-gated high-pitch computed tomography aortic angiography: Myocardial perfusion defects in patients with suspected aortic dissection, Journal of Cardiovascular Computed Tomography (2017), http://dx.doi.org/10.1016/ j.jcct.2017.04.003
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L.-T. Huang et al. / Journal of Cardiovascular Computed Tomography xxx (2017) 1e5
Fig. 2. Representative non-ECG-gated contrast-enhanced CTA image of a 67-year-old woman who presented with chest tightness, dyspnoea, and cold sweating. First-pass axial image of CTA of the aorta (a) revealed transmural perfusion defect in the territory of the anterior descending coronary artery (LAD). The average attenuation was 31.36. Percutaneous coronary intervention (b) revealed total occlusion at the mid portion of the left anterior descending coronary artery (arrow). After emergent percutaneous coronary intervention with stenting for LAD and anticoagulant and fibrinolytic therapy, her vital signs became stable. Cardiac ultrasound revealed adequate global LV systolic function (LVEF ¼ 55%), and akinesia at the apical anterior segment and apex of the LV.
chest pain in ED.11e14 Combined CTP and coronary CTA have a high specificity (100%) and PPV (91%) in patients with STEMI or possible ACS that present at emergency departments.15,16 CT examinations with a high table speed (pitch of 2.0) can be used to examine large volumes in a single scan without ECG gating. A high table feed leads to a coherent data set of the heart without interslice gaps or steps and high temporal resolution reduces motion artifacts.17 Although nongated high-pitch CTA of the aorta has been established as an initial diagnostic imaging modality for suspected acute aortic syndromes, its diagnostic efficiency for detecting AMI in patients admitted to the ED has not yet been investigated.5 In our retrospective study, perfusion defects detected through visual assessment on the late arterial phase in nongated high-pitch CTA of the aorta exhibited high specificity (94.7%) and a high NPV (93.5%) for the identification of patients with AMI. The CT attenuation of the infarcted myocardium (38.9 ± 14 HU) reported by Francone at al7 was much lower than that observed in our study (67.6 ± 29.5 HU). However, Schepis at al16 demonstrated a similar result with significantly reduced CT attenuation, as low as 59 ± 18 HU in cases with NSTEMI. Gosalia et al.18 reported a decrease of 20 HU, indicating reduction in myocardial enhancement. This value is quite similar with our result (about 25 HU). According to our result, myocardial perfusion defect can be detected on the late arterial phase acquired at 50 s post-threshold by nongated high-pitch CTA of the aorta in patients with AMI. The late thoracoabdominal CT scan obtained 50 s to 2 min after bolus injection provides information about visceral malperfusion, slow endograft leaks, late filling of the false lumen, contrast extravasation from rupture, and additional abdominal diagnoses.19,20 Shriki et al. also suggested that late arterial scan might be the appropriate scanning window for assessment of myocardial perfusion abnormality.21 To eliminate the scan protocol-associated difference in CT attenuation, we calculated DHU myocardium and myocardium ratio by using the density of the paraspinal muscle at the level of T10 for self-
calibration and achieved a significant difference in the diseased group (P < 0.001). Quantitative measurements obtained using values of DHU myocardium (10.1 HU) and myocardial ratio (1.15) had high specificity and a high NPV, facilitating to detect AMI. This study has some limitations. First, we excluded patients with a previous history of MI in the analysis. Therefore, this study cannot be extrapolated to a general population with acute chest pain. Second, the non-ECG-gated CT protocol may have affected the image quality and reduced the accuracy of visual assessment of perfusion defects, particularly when the heart rate and rhythm of the recruited patients were not controlled by using oral medication. Third, because we exclude patients with previous history of MI based on their medical records, patients with silent MI may have been included in our study population. A patient with an old infarct could be identified, even if the current infarct was in a different location. Fourth, the infero-lateral region of the myocardium was easily misinterpreted because of beam-hardening artifacts caused by LV cavity and descending aorta. It could be reduced by multiple reconstructions for myocardial perfusion defect assessment22 which was not available in nongated CTA of the aorta. Finally, using only axial images to visually evaluate the presence of perfusion defects might have underestimated the prevalence of inferior wall infarction, which would have been most clearly observed on coronal reconstructed images. 5. Conclusion Non-ECG-gated CTA of the aorta provided information for diagnosing AMI in patients presenting with acute chest pain at the
Table 3 Myocardial attenuation difference between the diseased and control groups. Attenuation value (Mean ± SD)
Table 2 Visual assessment of the left ventricular myocardial perfusion defect.
PD(þ) PD() Total
Control group
AMI(þ)
AMI()
Total
12 10 22
8 144 152
20 154
Note. PD ¼ perfusion defect, AMI ¼ acute myocardial infarction.
Normal IVS Perfusion defect Paraspinal muscle DHU Myocardium Myocardium Ratio
P value
Diseased group
92.2 ± 19.7 53.8 ± 8.8 40.4 ± 21.7 1.80 ± 0.48
67.6 53.2 13.5 1.27
± ± ± ±
29.5 9.5 29.5 0.55
<0.001 0.392 <0.001 <0.001
Note. IVS ¼ interventricular septum.
Please cite this article in press as: Huang L-T, et al., Non-gated high-pitch computed tomography aortic angiography: Myocardial perfusion defects in patients with suspected aortic dissection, Journal of Cardiovascular Computed Tomography (2017), http://dx.doi.org/10.1016/ j.jcct.2017.04.003
L.-T. Huang et al. / Journal of Cardiovascular Computed Tomography xxx (2017) 1e5
Fig. 3. Receiver operating characteristic (ROC) curves of DHU myocardium and myocardial ratio showed good accuracy and high specificity for exclusion AMI by using optimised cut-off points. Panel A: DHU myocardium (AUC: 0.75, specificity: 95.4%) Panel B: myocardium ratio (AUC: 0.75, specificity: 94.7%).
ED. In addition to visualization of myocardial perfusion defects, calculation of the attenuation difference between the myocardial perfusion defect and healthy myocardium (DHU myocardium) and of the ratio adjusted by the paraspinal muscle (myocardial ratio) strengthened the confidence in the AMI diagnosis when they were less than 10.1 HU and 1.15, respectively. Funding This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Conflict of interest All authors declare that there is no conflict of interest in this study and state that this work has not received any funding. Acknowledgements Nothing to disclose. Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jcct.2017.04.003. References 1. Mano Y, Anzai T, Yoshizawa A, Itabashi Y, Ohki T. Role of nonelectrocardiogram-gated contrast-enhanced computed tomography in the diagnosis of acute coronary syndrome. Heart vessels. Jan 2015;30:1e8. 2. Sorgaard MH, Kofoed KF, Linde JJ, et al. Diagnostic accuracy of static CT perfusion for the detection of myocardial ischemia. A systematic review and
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meta-analysis. J Cardiovasc Comput Tomogr. Nov - Dec 2016;10:450e457. 3. Pursnani A, Lee AM, Mayrhofer T, et al. Early resting myocardial computed tomography perfusion for the detection of acute coronary syndrome in patients with coronary artery disease. Circ Cardiovasc imaging. Mar 2015;8:e002404. 4. Flohr TG, Leng S, Yu L, et al. Dual-source spiral CT with pitch up to 3.2 and 75 ms temporal resolution: image reconstruction and assessment of image quality. Med Phys. Dec 2009;36:5641e5653. 5. Beeres M, Schell B, Mastragelopoulos A, et al. High-pitch dual-source CT angiography of the whole aorta without ECG synchronisation: initial experience. Eur Radiol. Jan 2012;22:129e137. 6. Thygesen K, Alpert JS, Jaffe AS, et al. Third universal definition of myocardial infarction. Circulation. Oct 16 2012;126:2020e2035. 7. Francone M, Carbone I, Danti M, et al. ECG-gated multi-detector row spiral CT in the assessment of myocardial infarction: correlation with non-invasive angiographic findings. Eur Radiol. Jan 2006;16:15e24. 8. Hallgren KA. Computing inter-rater reliability for observational data: an overview and tutorial. Tutorials quantitative methods Psychol. 2012;8:23e34. 9. Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet (London, Engl. Feb 8 1986;1:307e310. 10. Menzel H, Schibilla H, Teunen D. European guidelines on quality criteria for computed tomography. Luxemb Eur Comm. 2000:16262. 11. Litt HI, Gatsonis C, Snyder B, et al. CT angiography for safe discharge of patients with possible acute coronary syndromes. N. Engl J Med. Apr 12 2012;366: 1393e1403. 12. Hascoet S, Bongard V, Chabbert V, et al. Early triage of emergency department patients with acute coronary syndrome: contribution of 64-slice computed tomography angiography. Archives Cardiovasc Dis. Jun-Jul 2012;105:338e346. 13. Cury RC, Feuchtner GM, Batlle JC, et al. Triage of patients presenting with chest pain to the emergency department: implementation of coronary CT angiography in a large urban health care system. AJR Am J Roentgenol. Jan 2013;200: 57e65. 14. Weigold WG. Coronary computed tomography angiography in the emergency department: the high stakes game of low risk chest pain. J Am Coll Cardiol. Feb 26 2013;61:893e895. 15. Branch KR, Busey J, Mitsumori LM, et al. Diagnostic performance of resting CT myocardial perfusion in patients with possible acute coronary syndrome. AJR Am J Roentgenol. May 2013;200:W450eW457. 16. Schepis T, Achenbach S, Marwan M, et al. Prevalence of first-pass myocardial perfusion defects detected by contrast-enhanced dual-source CT in patients with non-ST segment elevation acute coronary syndromes. Eur Radiol. Jul 2010;20:1607e1614. 17. Busch JL, Alessio AM, Caldwell JH, et al. Myocardial hypo-enhancement on resting computed tomography angiography images accurately identifies myocardial hypoperfusion. J Cardiovasc Comput Tomogr. Nov-Dec 2011;5: 412e420. 18. Gosalia A, Haramati LB, Sheth MP, Spindola-Franco H. CT detection of acute myocardial infarction. AJR Am J Roentgenol. Jun 2004;182:1563e1566. 19. Abbara S, Kalva S, Cury RC, Isselbacher EM. Thoracic aortic disease: Spectrum of multidetector computed tomography imaging findings. Journal of cardiovascular computed tomography.1(1):40e54. 20. Goldstein SA, Evangelista A, Abbara S, et al. Multimodality imaging of diseases of the thoracic aorta in adults: from the american society of echocardiography and the european association of cardiovascular imaging: endorsed by the society of cardiovascular computed tomography and society for cardiovascular magnetic resonance. J Am Soc Echocardiogr. Feb 2015;28:119e182. 21. Shriki JE, Shinbane J, Lee C, et al. Incidental myocardial infarct on conventional nongated CT: a review of the spectrum of findings with gated CT and cardiac MRI correlation. AJR Am J Roentgenol. Mar 2012;198:496e504. 22. Bezerra HG, Loureiro R, Irlbeck T, et al. Incremental value of myocardial perfusion over regional left ventricular function and coronary stenosis by cardiac CT for the detection of acute coronary syndromes in high-risk patients: a subgroup analysis of the ROMICAT trial. J Cardiovasc Comput Tomogr. Nov-Dec 2011;5:382e391.
Please cite this article in press as: Huang L-T, et al., Non-gated high-pitch computed tomography aortic angiography: Myocardial perfusion defects in patients with suspected aortic dissection, Journal of Cardiovascular Computed Tomography (2017), http://dx.doi.org/10.1016/ j.jcct.2017.04.003
Contents lists available at ScienceDirect
Journal of Cardiovascular Computed Tomography journal homepage: www.JournalofCardiovascularCT.com
Research paper
Non-gated high-pitch computed tomography aortic angiography: Myocardial perfusion defects in patients with suspected aortic dissection Li-Ting Huang, M.D. a, Shih-Hung Chan, M.D. b, Chia-Chang Chuang, M.D. c, Yi-Shan Tsai, M.D. a, * a
Department of Diagnostic Radiology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, No.138, Sheng Li Road, Tainan, 704, Taiwan ROC Division of Cardiology, Department of Internal Medicine, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, No.138, Sheng Li Road, Tainan, 704, Taiwan ROC c Department of Emergency Medicine, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, No.138, Sheng Li Road, Tainan, 704, Taiwan ROC b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 9 January 2017 Received in revised form 20 March 2017 Accepted 11 April 2017 Available online xxx
Objectives: To investigate the diagnostic value of first-pass myocardial perfusion defects visualised in non-gated high-pitch computed tomography angiography (CTA) in patients admitted to the emergency department (ED) for suspected aortic dissection. Methods: We recruited 174 ED patients who underwent high-pitch CTA of the aorta because of suspected aortic dissection. We divided these patients into two groups (diseased and control groups) based on whether their clinical data fulfilled the third universal definition of acute myocardial infarction (AMI), specifically an increase in cardiac troponin (cTn) with at least one of the following: (a) symptoms of ischemia; (b) new ST-segment-T wave (ST-T) changes or new left bundle branch block (LBBB); (c) development of pathological Q wave; (d) new loss of viable myocardium or new regional wall motion abnormality; or (e) identification of an intracoronary thrombus by angiography or autopsy. Twenty-two patients with a clinical diagnosis of AMI were placed in the diseased group. Myocardial perfusion defects were evaluated qualitatively and quantitatively on the late arterial phase obtained 50 s post-threshold. Results: Of the 22 patients with a final diagnosis of AMI, visually identifiable perfusion defects were observed in 12 patients. The sensitivity, specificity, negative predictive value, and positive predictive value of any perfusion defect for predicting AMI were 54.6%, 94.7%, 93.5%, and 60.0%, respectively. Quantitative analysis indicated that CT attenuation was significantly lower within perfusion defects than within the normal myocardium (67.3 ± 29.5 HU vs. 92.8 ± 19.7 HU; p < 0.001). Conclusions: In patients with acute chest pain, the presence of myocardial perfusion defect observed on nongated high-pitch CTA of the aorta can be used to identify individuals with AMI with high specificity, but low sensitivity. © 2017 Published by Elsevier Inc. on behalf of Society of Cardiovascular Computed Tomography.
Keywords: Dual-source CT High pitch Myocardial perfusion Perfusion defect Myocardial infarction
1. Introduction Non-electrocardiogram (ECG)-gated contrast-enhanced computed tomography (CT) angiography (CTA) is available in most hospitals where patients with chest and/or back pain are admitted to the emergency department (ED).1 Mano et al.
* Corresponding author. E-mail address: [email protected] (Y.-S. Tsai).
investigated the role of perfusion defects in diagnosis of acute coronary syndrome in 154 consecutive patients admitted to the ED to differentiate acute aortic dissection from pulmonary thromboembolism (PE) by using non ECG-gated 64-slice CT. The results demonstrated a high sensitivity (93%) and negative predictive value (NPV, 98%) to identify acute myocardial infarction (AMI).1 Coronary CT angiography (coronary CTA) can detect coronary artery disease in patients with chest pain. The addition of CT perfusion (CTP) to coronary CTA improves its specificity and positive predictive value (PPV) regarding the presence of myocardial ischemia.2 The addition
http://dx.doi.org/10.1016/j.jcct.2017.04.003 1934-5925/© 2017 Published by Elsevier Inc. on behalf of Society of Cardiovascular Computed Tomography.
Please cite this article in press as: Huang L-T, et al., Non-gated high-pitch computed tomography aortic angiography: Myocardial perfusion defects in patients with suspected aortic dissection, Journal of Cardiovascular Computed Tomography (2017), http://dx.doi.org/10.1016/ j.jcct.2017.04.003
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L.-T. Huang et al. / Journal of Cardiovascular Computed Tomography xxx (2017) 1e5
of CTP to coronary CTA increases the sensitivity to identify acute coronary syndromes (ACS) from 77% to 90%.3 The demonstration of perfusion abnormalities in chest CT is difficult because the myocardium is less resolved in non-gated studies. With the second generation dual-source CT, the option to increase pitch above the traditional technical limit of 1.5, in single-source CT, has allowed to substantially reduce image acquisition time and to increase volume coverage.4 High-pitch dual-source CTA of the entire aorta without ECG synchronisation is feasible in a very short time period and renders motion-free imaging of the aorta.5 Although non-gated high-pitch aortic CTA has been established as an initial diagnostic imaging modality for acute aortic syndromes, its diagnostic value for detecting AMI in a population with suspected aortic dissection has not yet been investigated. This study determined the diagnostic value of first-pass myocardial perfusion defects visualized using non-gated high-pitch contrast-enhanced CTA in patients admitted to the ED for suspected acute aortic syndromes. 2. Methods 2.1. Patients This study was approved by the institutional review board of the hospital. All patients provided written informed consent for CT imaging. However, the requirement of informed consent was waived for retrospective chart review. We retrospectively recruited patients with acute chest pain who underwent non-gated highpitch CTA of the aorta to exclude acute aortic dissection in the ED from July 2010 to September 2014. We reviewed each medical chart to identify the final diagnosis for each admission. AMI diagnosis was confirmed by an attending physician or cardiologist according to the third universal definition of AMI released in 2012 by the ESC/ ACCF/AHA/WHF,6 which included a dynamic change of cardiac troponin (cTn) and at least one of the following: (a) symptoms of ischemia; (b) new ST-segment-T wave (ST-T) changes or new left bundle branch block (LBBB); (c) development of pathological Q wave; (d) new loss of viable myocardium or new regional wall motion abnormality; or (e) identification of an intracoronary thrombus by angiography or autopsy. Exclusion criteria were as follows: 1) history of coronary artery disease (CAD), 2) history of previous MI, 3) absence of ECG data at ED visit, 4) absence of two consecutive (within 24 h) cardiac troponin I (cTn-I) data at ED, and 5) poor imaging quality. We divided the recruited patients into two groups: the diseased group, comprising patients who had received a diagnosis of ST-elevation myocardial infarction (STEMI) or nonST-elevation myocardial infarction (NSTEMI), and a control group, comprising patients who had not received a diagnosis of STEMI or NSTEMI. 2.2. CT imaging protocol We used a high-pitch, 128-slice CT system (Definition Flash, Siemens, Forchheim, Germany) operated in single-source mode with a pitch of 2.0, collimation of 128 0.6 mm, rotation time of 0.28 s, tube potential of 120 kV, and 100e150 reference mAs. Data were acquired in the craniocaudal direction during a single breath hold. The imaging range extended from the upper thoracic aperture to the proximal femoral arteries. Patients were examined in the supine position. We injected 90 mL of an iodinated contrast material (iodine concentration of 400 mg/mL, Imeron 400, Bracco Imaging, Konstanz, Germany) at a flow rate of 3.5 cc/s by using an 18e20-G intravenous line followed by 50 mL of a saline chaser. CTA was automatically started based on a bolus-tracking measurement at the level of the ascending thoracic aorta at a threshold of 100 Hounsfield units (HU).The post-threshold delay scan for
early and late arterial phase was set to 13 s and 50 s, respectively. Transverse images were reconstructed at a 1.0-mm slice thickness with 0.7-mm increments by using a medium-soft convolution kernel (B30f) and a matrix size of 512 512. In addition, we reconstructed axial slices at a 5.0-mm thickness with 5.0-mm increment. 2.3. CT image analysis An experienced cardiac radiologist (YST, 14 years of experience) and a senior radiology resident (LTH, 3 years of experience) blinded to clinical and angiographic results jointly reviewed CTA of the aorta and reached consensus in cases of disagreement. Axial images reconstructed perpendicular to the long axis of the body were evaluated. The window width and centre of all images were set at 700 HU and 100 HU, respectively. Enhancement of the left ventricular myocardium was visually assessed on late arterial phase. According to previous studies, a perfusion defect was visually defined as a region of lower attenuation and/or wall thinning within the normally enhanced myocardium.7 Myocardial enhancement was measured in HU by circling the region of interest (ROIs) of approximately 10 mm2 within the perfusion defects, normal interventricular septum (IVS), and the paraspinal muscle at the level of T10, in three consecutive axial images. The average attenuation values were used for statistical analyses. DHU myocardium was calculated and defined as the enhancement difference between the normal IVS and the paraspinal muscle in the control group, and between the myocardial perfusion defect and paraspinal muscle in the diseased group. Myocardium ratio was defined as the IVS myocardium divided by the paraspinal muscle in the control group and the myocardial perfusion defect in the diseased group. Of the 174 image data sets, 20 were randomly analysed by a second observer to ensure interobserver reproducibility. 2.4. Statistical analysis Statistical analysis was performed using commercially available software (SPSS 17.0 for Windows; SPSS, Chicago, III). Continuous and categorical variables were expressed as medians ± standard deviations and percentages, respectively. The chi-square test was used for descriptive statistics. The independent t-test was used for evaluating the difference in average attenuation values and the adjusted attenuation value between the normal and infarcted regions. The receiver-operating characteristic (ROC) curves were constructed to assess the diagnostic accuracy of perfusion defects in AMI. Cut point estimates, 95% confidence interval (CI), and areas under the ROC curve (AUCs) were calculated. In addition, sensitivities and specificities at cut-off points were determined using the Youden index. A P value of <0.05 was considered statistically significant. Interrater reliability (IRR) was assessed using Kappa statistics. IRR was poor, fair, good, and excellent for Cronbach's alpha values < 0.40, between 0.40 and 0.59, between 0.60 and 0.74, and between 0.75 and 1.0, respectively.8 Intrarater reliability was evaluated using testeretest reliability. A Pearson correlation coefficient of >0.7 indicated good consistency.9 3. Results 3.1. Patients From July 2010 to September 2014, 618 patients visited the ED and underwent high-pitch CTA of the aorta because they were suspected to have acute aortic dissection. Of them, 174 were
Please cite this article in press as: Huang L-T, et al., Non-gated high-pitch computed tomography aortic angiography: Myocardial perfusion defects in patients with suspected aortic dissection, Journal of Cardiovascular Computed Tomography (2017), http://dx.doi.org/10.1016/ j.jcct.2017.04.003
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recruited for final analysis after excluding 93 patients without ECG data, 342 patients without two consecutive c-TnI measurement results, 6 patients with a previous history of CAD and MI, and 3 patients with poor CTA imaging quality (Fig. 1). Based on clinical assessment, we identified 22 patients with AMI. The percentage of patients with diabetes and dyslipidaemia was significantly higher in the diseased group than in the control group (40.9% vs. 17.1%, P ¼ 0.020 and 50.0% vs. 12.5%, P < 0.001, respectively). Furthermore, the number of patients who underwent percutaneous coronary intervention was significantly higher in the diseased group than in the control group (Table 1). 3.2. Visual analysis results According to visual assessment, perfusion defects were present in CT in 12 patients with AMI (Fig. 2, DICOM File here). We recorded 10 false-negative and 8 false-positive cases, resulting in a sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of 54.6% (12/22), 94.7% (144/152), 93.5% (144/154), and 60.0% (12/20), respectively (Table 2).
3
Table 1 Demographic data of the control and diseased groups. Control group N ¼ 152 Age 60.6 ± 16.8 Sex N(%) Female 50(32.9) Male 102(66.1) Hypertension N(%) 78(51.3) Diabetes N(%) 26(17.1) Dyslipidemia N(%) 19(12.5) PCI N(%) 6(4.0)
Diseased group N ¼ 22
P value
58.3 ± 13.4
0.542
6(27.3) 16(72.7)
0.777
13(59.1)
0.650
9(40.9)
0.020
11(50.0) 20(90.9)
0.001 <0.0001
Note. PCI ¼ percutaneous coronary intervention.
(Cronbach's alpha ¼ 0.956). The consistency of one observer's measurement of the myocardium in patients was good (Pearson correlation coefficient ¼ 0.98). 3.5. Radiation dose
3.3. Quantitative analysis results Quantitative analysis indicated that CT attenuation within perfusion defects was significantly lower than that within the normal myocardium (67.6 ± 29.5 HU vs. 92.2 ± 19.7 HU; P < 0.001). Furthermore, DHU myocardium and myocardium ratio were significantly lower in the diseased group than in the control group (13.5 ± 29.5 vs. 40.4 ± 21.7 HU; P < 0.001 and 1.27 ± 0.55 vs. 1.80 ± 0.48; P < 0.001, respectively; Table 3). ROC analyses demonstrated that the AUCs of DHU myocardium and myocardium ratio for predicting AMI were 0.75 (95% CI 0.68e0.81) and 0.75 (95% CI 0.67e0.81), respectively. The sensitivity and specificity for diagnosing AMI by using the optimised cut-off point of DHU myocardium (10.1 HU) were 54.6% and 95.4%, respectively, and those obtained using the optimised cut-off point of myocardium ratio (1.15) were 54.6% and 94.7%, respectively (Fig. 3). 3.4. Interobserver agreement and intrarater reliability The results of the two observers regarding the attenuation value of the myocardium in 20 patients exhibited excellent concordance
The average of the dose-length product provided by the CT system for estimating a radiation dose of each phase was 361.85 ± 169.77 mGy*cm. The effective radiation dose delivered in thoracoabdominal CTA was calculated using a method proposed by the European Working Group for Guidelines on Quality Criteria for CT.10 Because acquisitions of the chest, abdomen, and pelvis were performed using thoracoabdominal CTA, the mean of these regionspecific conversion coefficients (k ¼ 0.017 mSv/mGy*cm) was used as previously described.10 The average of the effective radiation dose of each phase in 174 patents was 6.15 ± 2.89 mSv. 4. Discussion The triage of patients with acute chest pain in the ED remains challenging, particularly in patients without changes in ECG or cardiac enzymes. Moreover, increased blood concentrations of troponin can also be observed in various other diseases such as sepsis, atrial fibrillation, heart failure, pulmonary embolism, myocarditis, myocardial contusion, and renal failure. Recently, ECGgated coronary CTA has been reported to play a major role from triage to treatment decisions in patients presenting with acute
Fig. 1. Flow chart of the selection process for patient enrolment in the final study.
Please cite this article in press as: Huang L-T, et al., Non-gated high-pitch computed tomography aortic angiography: Myocardial perfusion defects in patients with suspected aortic dissection, Journal of Cardiovascular Computed Tomography (2017), http://dx.doi.org/10.1016/ j.jcct.2017.04.003
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L.-T. Huang et al. / Journal of Cardiovascular Computed Tomography xxx (2017) 1e5
Fig. 2. Representative non-ECG-gated contrast-enhanced CTA image of a 67-year-old woman who presented with chest tightness, dyspnoea, and cold sweating. First-pass axial image of CTA of the aorta (a) revealed transmural perfusion defect in the territory of the anterior descending coronary artery (LAD). The average attenuation was 31.36. Percutaneous coronary intervention (b) revealed total occlusion at the mid portion of the left anterior descending coronary artery (arrow). After emergent percutaneous coronary intervention with stenting for LAD and anticoagulant and fibrinolytic therapy, her vital signs became stable. Cardiac ultrasound revealed adequate global LV systolic function (LVEF ¼ 55%), and akinesia at the apical anterior segment and apex of the LV.
chest pain in ED.11e14 Combined CTP and coronary CTA have a high specificity (100%) and PPV (91%) in patients with STEMI or possible ACS that present at emergency departments.15,16 CT examinations with a high table speed (pitch of 2.0) can be used to examine large volumes in a single scan without ECG gating. A high table feed leads to a coherent data set of the heart without interslice gaps or steps and high temporal resolution reduces motion artifacts.17 Although nongated high-pitch CTA of the aorta has been established as an initial diagnostic imaging modality for suspected acute aortic syndromes, its diagnostic efficiency for detecting AMI in patients admitted to the ED has not yet been investigated.5 In our retrospective study, perfusion defects detected through visual assessment on the late arterial phase in nongated high-pitch CTA of the aorta exhibited high specificity (94.7%) and a high NPV (93.5%) for the identification of patients with AMI. The CT attenuation of the infarcted myocardium (38.9 ± 14 HU) reported by Francone at al7 was much lower than that observed in our study (67.6 ± 29.5 HU). However, Schepis at al16 demonstrated a similar result with significantly reduced CT attenuation, as low as 59 ± 18 HU in cases with NSTEMI. Gosalia et al.18 reported a decrease of 20 HU, indicating reduction in myocardial enhancement. This value is quite similar with our result (about 25 HU). According to our result, myocardial perfusion defect can be detected on the late arterial phase acquired at 50 s post-threshold by nongated high-pitch CTA of the aorta in patients with AMI. The late thoracoabdominal CT scan obtained 50 s to 2 min after bolus injection provides information about visceral malperfusion, slow endograft leaks, late filling of the false lumen, contrast extravasation from rupture, and additional abdominal diagnoses.19,20 Shriki et al. also suggested that late arterial scan might be the appropriate scanning window for assessment of myocardial perfusion abnormality.21 To eliminate the scan protocol-associated difference in CT attenuation, we calculated DHU myocardium and myocardium ratio by using the density of the paraspinal muscle at the level of T10 for self-
calibration and achieved a significant difference in the diseased group (P < 0.001). Quantitative measurements obtained using values of DHU myocardium (10.1 HU) and myocardial ratio (1.15) had high specificity and a high NPV, facilitating to detect AMI. This study has some limitations. First, we excluded patients with a previous history of MI in the analysis. Therefore, this study cannot be extrapolated to a general population with acute chest pain. Second, the non-ECG-gated CT protocol may have affected the image quality and reduced the accuracy of visual assessment of perfusion defects, particularly when the heart rate and rhythm of the recruited patients were not controlled by using oral medication. Third, because we exclude patients with previous history of MI based on their medical records, patients with silent MI may have been included in our study population. A patient with an old infarct could be identified, even if the current infarct was in a different location. Fourth, the infero-lateral region of the myocardium was easily misinterpreted because of beam-hardening artifacts caused by LV cavity and descending aorta. It could be reduced by multiple reconstructions for myocardial perfusion defect assessment22 which was not available in nongated CTA of the aorta. Finally, using only axial images to visually evaluate the presence of perfusion defects might have underestimated the prevalence of inferior wall infarction, which would have been most clearly observed on coronal reconstructed images. 5. Conclusion Non-ECG-gated CTA of the aorta provided information for diagnosing AMI in patients presenting with acute chest pain at the
Table 3 Myocardial attenuation difference between the diseased and control groups. Attenuation value (Mean ± SD)
Table 2 Visual assessment of the left ventricular myocardial perfusion defect.
PD(þ) PD() Total
Control group
AMI(þ)
AMI()
Total
12 10 22
8 144 152
20 154
Note. PD ¼ perfusion defect, AMI ¼ acute myocardial infarction.
Normal IVS Perfusion defect Paraspinal muscle DHU Myocardium Myocardium Ratio
P value
Diseased group
92.2 ± 19.7 53.8 ± 8.8 40.4 ± 21.7 1.80 ± 0.48
67.6 53.2 13.5 1.27
± ± ± ±
29.5 9.5 29.5 0.55
<0.001 0.392 <0.001 <0.001
Note. IVS ¼ interventricular septum.
Please cite this article in press as: Huang L-T, et al., Non-gated high-pitch computed tomography aortic angiography: Myocardial perfusion defects in patients with suspected aortic dissection, Journal of Cardiovascular Computed Tomography (2017), http://dx.doi.org/10.1016/ j.jcct.2017.04.003
L.-T. Huang et al. / Journal of Cardiovascular Computed Tomography xxx (2017) 1e5
Fig. 3. Receiver operating characteristic (ROC) curves of DHU myocardium and myocardial ratio showed good accuracy and high specificity for exclusion AMI by using optimised cut-off points. Panel A: DHU myocardium (AUC: 0.75, specificity: 95.4%) Panel B: myocardium ratio (AUC: 0.75, specificity: 94.7%).
ED. In addition to visualization of myocardial perfusion defects, calculation of the attenuation difference between the myocardial perfusion defect and healthy myocardium (DHU myocardium) and of the ratio adjusted by the paraspinal muscle (myocardial ratio) strengthened the confidence in the AMI diagnosis when they were less than 10.1 HU and 1.15, respectively. Funding This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Conflict of interest All authors declare that there is no conflict of interest in this study and state that this work has not received any funding. Acknowledgements Nothing to disclose. Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jcct.2017.04.003. References 1. Mano Y, Anzai T, Yoshizawa A, Itabashi Y, Ohki T. Role of nonelectrocardiogram-gated contrast-enhanced computed tomography in the diagnosis of acute coronary syndrome. Heart vessels. Jan 2015;30:1e8. 2. Sorgaard MH, Kofoed KF, Linde JJ, et al. Diagnostic accuracy of static CT perfusion for the detection of myocardial ischemia. A systematic review and
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meta-analysis. J Cardiovasc Comput Tomogr. Nov - Dec 2016;10:450e457. 3. Pursnani A, Lee AM, Mayrhofer T, et al. Early resting myocardial computed tomography perfusion for the detection of acute coronary syndrome in patients with coronary artery disease. Circ Cardiovasc imaging. Mar 2015;8:e002404. 4. Flohr TG, Leng S, Yu L, et al. Dual-source spiral CT with pitch up to 3.2 and 75 ms temporal resolution: image reconstruction and assessment of image quality. Med Phys. Dec 2009;36:5641e5653. 5. Beeres M, Schell B, Mastragelopoulos A, et al. High-pitch dual-source CT angiography of the whole aorta without ECG synchronisation: initial experience. Eur Radiol. Jan 2012;22:129e137. 6. Thygesen K, Alpert JS, Jaffe AS, et al. Third universal definition of myocardial infarction. Circulation. Oct 16 2012;126:2020e2035. 7. Francone M, Carbone I, Danti M, et al. ECG-gated multi-detector row spiral CT in the assessment of myocardial infarction: correlation with non-invasive angiographic findings. Eur Radiol. Jan 2006;16:15e24. 8. Hallgren KA. Computing inter-rater reliability for observational data: an overview and tutorial. Tutorials quantitative methods Psychol. 2012;8:23e34. 9. Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet (London, Engl. Feb 8 1986;1:307e310. 10. Menzel H, Schibilla H, Teunen D. European guidelines on quality criteria for computed tomography. Luxemb Eur Comm. 2000:16262. 11. Litt HI, Gatsonis C, Snyder B, et al. CT angiography for safe discharge of patients with possible acute coronary syndromes. N. Engl J Med. Apr 12 2012;366: 1393e1403. 12. Hascoet S, Bongard V, Chabbert V, et al. Early triage of emergency department patients with acute coronary syndrome: contribution of 64-slice computed tomography angiography. Archives Cardiovasc Dis. Jun-Jul 2012;105:338e346. 13. Cury RC, Feuchtner GM, Batlle JC, et al. Triage of patients presenting with chest pain to the emergency department: implementation of coronary CT angiography in a large urban health care system. AJR Am J Roentgenol. Jan 2013;200: 57e65. 14. Weigold WG. Coronary computed tomography angiography in the emergency department: the high stakes game of low risk chest pain. J Am Coll Cardiol. Feb 26 2013;61:893e895. 15. Branch KR, Busey J, Mitsumori LM, et al. Diagnostic performance of resting CT myocardial perfusion in patients with possible acute coronary syndrome. AJR Am J Roentgenol. May 2013;200:W450eW457. 16. Schepis T, Achenbach S, Marwan M, et al. Prevalence of first-pass myocardial perfusion defects detected by contrast-enhanced dual-source CT in patients with non-ST segment elevation acute coronary syndromes. Eur Radiol. Jul 2010;20:1607e1614. 17. Busch JL, Alessio AM, Caldwell JH, et al. Myocardial hypo-enhancement on resting computed tomography angiography images accurately identifies myocardial hypoperfusion. J Cardiovasc Comput Tomogr. Nov-Dec 2011;5: 412e420. 18. Gosalia A, Haramati LB, Sheth MP, Spindola-Franco H. CT detection of acute myocardial infarction. AJR Am J Roentgenol. Jun 2004;182:1563e1566. 19. Abbara S, Kalva S, Cury RC, Isselbacher EM. Thoracic aortic disease: Spectrum of multidetector computed tomography imaging findings. Journal of cardiovascular computed tomography.1(1):40e54. 20. Goldstein SA, Evangelista A, Abbara S, et al. Multimodality imaging of diseases of the thoracic aorta in adults: from the american society of echocardiography and the european association of cardiovascular imaging: endorsed by the society of cardiovascular computed tomography and society for cardiovascular magnetic resonance. J Am Soc Echocardiogr. Feb 2015;28:119e182. 21. Shriki JE, Shinbane J, Lee C, et al. Incidental myocardial infarct on conventional nongated CT: a review of the spectrum of findings with gated CT and cardiac MRI correlation. AJR Am J Roentgenol. Mar 2012;198:496e504. 22. Bezerra HG, Loureiro R, Irlbeck T, et al. Incremental value of myocardial perfusion over regional left ventricular function and coronary stenosis by cardiac CT for the detection of acute coronary syndromes in high-risk patients: a subgroup analysis of the ROMICAT trial. J Cardiovasc Comput Tomogr. Nov-Dec 2011;5:382e391.
Please cite this article in press as: Huang L-T, et al., Non-gated high-pitch computed tomography aortic angiography: Myocardial perfusion defects in patients with suspected aortic dissection, Journal of Cardiovascular Computed Tomography (2017), http://dx.doi.org/10.1016/ j.jcct.2017.04.003