- Email: [email protected]
Comparison of Lumens of Intermediate Coronary Stenosis Using 16-Slice Computed Tomography Versus Intravascular Ultrasound
Comparison of Lumens of Intermediate Coronary Stenosis Using 16-Slice Computed Tomography Versus Intravascular Ultrasound Christophe Caussin, MDa,*, Béatrice Daoud, MDa, Saïd Ghostine, MDa, Eric Perrier, MDb, Michel Habis, MDa, Bernard Lancelin, MDa, Claude-Yves Angel, MDa, and Jean-François Paul, MDa We aimed to quantify ambiguous coronary stenosis using the minimal lumen area with 16-slice computed tomography compared with intravascular ultrasound. The sensitivity, specificity, and accuracy for significant lesion classification was 68%, 86%, and 78%, respectively. The correlation between intravascular ultrasound and CT minimal lumen area was r ⴝ 0.73 (p <0.001), and the 95% confidence interval for CT measurement was ⴚ72% to ⴙ56%. © 2005 Elsevier Inc. All rights reserved. (Am J Cardiol 2005;96:524 –528) Sixteen-slice computed tomography (CT) has been shown to be effective in stenosis assessment compared with angiography.1–7 The sensitivity and specificity for ⬎50% stenosis determined by visual estimation was 72% to 92% and 86% to 99%, respectively, with a ⬎95% negative predictive value. However, because the stenosis assessment was based on visual estimation and because angiography is an imperfect technique, especially for intermediate lesion evaluation,8,9 the accuracy of 16-slice CT for ambiguous lesions is unknown. Intravascular ultrasound (IVUS) provides superior anatomic definition of the coronary arterial dimensions compared with angiography and a better assessment of the degree of narrowing.10,11 The minimal lumen area (MLA) evaluated with IVUS in the case of intermediate lesions correlated with the clinical outcome in contrast to the angiographic findings.9 Using the ability of CT to visualize the plaque and to reconstruct the arterial cross section,12–14 we aimed to quantify the MLA using 16-slice CT in intermediate ambiguous stenosis detected by angiography, with IVUS as the reference. •••
A total of 54 patients who were admitted to our institution for suspected myocardial ischemia and in whom angiography showed moderate stenosis (30% to 60% by visual assessment) were selected for the study. Suspicion for myocardial ischemia was present with clinically typical chest pain, chest pain and ST-T modification on an electrocardiogram at rest or exercise test or nuclear imaging with positive findings. The exclusion criteria were renal insufficiency, intolerance to iodinated contrast media, and the presence of arrhythmias. All patients underwent angiography, IVUS, and 16-slice CT within 72 hours and before revasculariza-
a
Hôpital Marie Lannelongue, Le Plessis Robinson, France; and bHôpital Inter-Armée Percy, Clamart, France. Manuscript received December 2004; revised manuscript received and accepted April 1, 2005. * Corresponding author: Tel: 33-1-40-94-28-00; fax: 33-1-40-94-55-84. E-mail address: [email protected]. (C. Caussin) 0002-9149/05/$ – see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.amjcard.2005.04.013
tion. The location of the target lesion was selected on the angiograms and IVUS scans and was defined using the American College of Cardiology/American Heart Association classification for CT analysis. The institutional review board approved the research protocol, and all patients gave informed consent. Angiography was performed by experienced operators. At least 2 orthogonal views were acquired to optimize the stenosis evaluation. The angiograms were reviewed by an operator unaware of the IVUS and CT results. Quantitative coronary angiography was performed using the CAAS II algorithm.15 Calibrating with the outer diameter of the contrast-empty catheter, the minimal lumen diameter in diastole from the “worst” view was determined. The diameter stenosis percentage was measured and the area stenosis percentage determined. Lesion significance was determined using 2 different methods as defined in previous studies: (1) using the minimal lumen diameter, a lesion was considered significant if the minimal lumen diameter was ⬍2.0 mm8 for the left main or ⬍1.5 mm9 for the other epicardial vessels; and (2) using the diameter stenosis percentage if the stenosis was ⬎50% regardless of the artery.16 IVUS was performed in the suspected target lesion, according to the angiographic findings, electrocardiographic findings, or ventricular damage. Another suspected culprit artery could be explored at the discretion of the operator if necessary. The IVUS catheter used was a 40-MHz Atlantis (Boston Scientific, Boston, Massachusetts). A first motorized pullback was performed at 0.5 mm/s, starting ⬎10 mm distal to the lesion and ending at the aorto-ostial junction. A second manual pullback was performed at the tightest sites, with a 5- to 8-ml saline flush to allow a better visualization of the lumen contour. Images were recorded on s-VHS videotape for off-line analysis. MLA was manually traced by 2 independent operators (CC and SG), who were unaware of the CT findings, according to the American College of Cardiology clinical expert consensus document.11 A significant lesion was defined as a ⱕ6 mm2 MLA8 for the www.AJConline.org
Coronary Artery Disease/16-Slice CT Versus IVUS in Intermediate Stenosis
525
Table 1 Demographic data, presentation, and culprit artery of selected population (n ⫽ 51) Variable
n (%)
Age (yrs) (mean ⫾ SD) Hypercholesterolemia ⬎240 mg/dl Smoker Diabetes mellitus Hypertension Previous myocardial infarction Previous coronary angioplasty Previous coronary bypass Acute myocardial infarction Unstable angina pectoris Stable angina pectoris Silent ischemia Culprit coronary artery Left main Left anterior descending Left circumflex Right
62 ⫾ 13 31 (61%) 25 (49%) 9 (18%) 32 (63%) 6 (12%) 10 (20%) 4 (8%) 5 (10%) 24 (46%) 11 (22%) 11 (22%) 10 (20%) 26 (51%) 3 (6%) 12 (24%)
left main and a ⱕ4 mm2 MLA9 for the other epicardial vessels. All patients underwent a retrospective electrocardiogram, gated 16-slice CT (Sensation 16, Siemens, Forchheim, Germany). Patients with a heart rate of ⬎60 beats/min received 100 mg of metoprolol 1 hour before performing CT to obtain optimal image quality. The rotation time was 420 ms, accounting for a total breath-hold of about 20 seconds. The CT images were acquired on 210 ms at the end of diastole. The position of the reconstruction window within the cardiac cycle was individually chosen to minimize motion artifacts. The slice thickness was 0.75 mm, with 0.5-mm increments of reconstruction. Maximal intensity projection and multiplanar reconstruction were used to select the tightest site. Then, the measurements were performed on cross-sectional artery reconstruc-
Figure 1. Scatterplots showing significant correlation (Y ⫽ 1.592 ⫹ 0.791X, r ⫽ 0.73, p ⬍0.001) between CT MLA and IVUS MLA.
Figure 2. MLA IVUS and CT Bland-Altman analysis. Solid line, systematic error (mean difference ⫺8%); hatched lines, limits of agreement (95% confidence interval ⫺72% to ⫹56%).
tion. MLA was manually drawn on cross-sectional reconstruction using a setting of 500-Hounsfield unit window and 150-Hounfield unit level. A significant lesion was defined as a ⱕ6 mm2 MLA for the left main and a ⱕ4 mm2 MLA for the other epicardial vessels. Two independent operators (JFP and BD), who were unaware of the IVUS findings, reconstructed the data and manually traced the contours. The reference value for IVUS comparison was the mean value of the 2 operators. The values are expressed as the mean ⫾ SD. Correlation between IVUS and CT was performed using Pearson’s correlation coefficient and Bland-Altman analysis. CT interobserver variability was expressed as the SD between the different CT operator findings. CT tracing variability was also assessed and expressed as the SD between operator tracings on the same image. The mean values of the 2 operators were compared with the IVUS findings. The sensitivity, specificity, accuracy, and Fisher’s exact test were used for significant lesion classification comparisons. Of the 54 patients screened, 1 was excluded because of a poor quality CT due to motion artifact, 2 were excluded because of IVUS problems (failure to cross the lesion for 1 because of proximal tortuosity and damage of the video tape for 1). All data were analyzed for the remaining 51 patients. The demographic data are listed in Table 1. The angiographic measurement revealed a reference diameter of 3.2 ⫾ 0.6 mm, minimal lumen diameter of 2.0 ⫾ 0.5 mm, diameter stenosis of 35.7 ⫾ 8.4%, and area stenosis of 53.7 ⫾ 16.1%. The MLA with IVUS was 5.7 ⫾ 2.5 mm2 and with CT was 6.1 ⫾ 2.7 mm2. Pearson’s correlation coefficient between CT MLA and IVUS MLA was r ⫽ 0.73 (p ⬍0.001; Figure 1). The interobserver variability for CT was 2.0 mm2 (36%). The CT tracing variability was 1.9 mm2 (31%). The variability for CT measurement compared with IVUS was 1.9 mm2 (32%). The systematic error (IVUS ⫺ CT) was ⫺8%.
526
The American Journal of Cardiology (www.AJConline.org)
Figure 3. Coronary angiogram (top left), 16-slice CT longitudinal (top right) and left main cross-sectional reconstruction (bottom right), and IVUS (bottom left) of 75-year-old woman admitted for typical rest chest pain. Angiogram shows significant 57% ostial left main stenosis, minimal lumen diameter was 1.6 mm. Longitudinal CT reconstruction showed left main moderate stenosis, MLA measured on cross-sectional reconstruction was nonsignificant (17 mm2); this was confirmed by IVUS (MLA 15 mm2).
Figure 4. Right coronary angiogram (left), 16-slice CT cross-sectional reconstruction (bottom right), and IVUS (top right) of 48-year-old patient admitted for chest pain and electrocardiogram showing transient D2, D3, VF ST-T depression. This patient had undergone previous coronary bypass grafting on left anterior descending artery, obtuse margin, and diagonal branch. Angiogram showed graft patency and moderate stenosis on mild right coronary artery (minimal lumen diameter 2.26 mm and percentage of stenosis 37%). CT showed large plaque burden with 4.0-mm2 MLA. IVUS confirmed CT findings with significant 3.5-mm2 MLA.
Coronary Artery Disease/16-Slice CT Versus IVUS in Intermediate Stenosis
527
Figure 5. Coronary angiogram (left), 16-slice CT cross-sectional reconstruction (bottom right), and IVUS (top right) of 64-year-old woman admitted for stable angina with positive bicycle test. Angiography showed only moderate stenosis on mild left anterior descending artery (minimal lumen diameter 1.68 mm and 26% stenosis). CT detected significant stenosis with 3-mm2 MLA, IVUS confirmed significant stenosis with 2.3-mm2 MLA.
The 95% confidence interval for MLA evaluation by CT was ⫺72% to ⫹56% (Figure 2 for Bland-Altman analysis). Regarding lesion classification, 22 of 51 lesions (43%) were considered significant using IVUS. The sensitivity, specificity, and accuracy for CT to classify significant lesions was 68%, 86%, and 78%, respectively (p ⬍0.0001). The sensitivity, specificity, and accuracy for quantitative angiography to classify significant lesions was 10%, 96%, and 59% (p ⫽ NS) for the stenosis percentage and 26%, 89%, and 61% for the minimal lumen diameter (p ⫽ NS), respectively. Figures 3 to 5 show the angiographic, IVUS, and CT films for 3 different patients. •••
The results of the present study have shown the feasibility of MLA quantification using 16-slice CT on cross-sectional artery reconstruction. An acceptable correlation between the IVUS and CT findings was found in ambiguous intermediate lesions by angiography. The severity of narrowing could be assessed with reasonable accuracy using MLA on crosssectional reconstruction. Despite a lower spatial resolution than angiography, CT measurement permitted direct atheroma visualization and lumen assessment. Concerning 16-slice CT atheroma evaluation, systematic use of IVUS provided an accurate reference for atheroma severity determination. As in other studies,8,9 our study showed quantitative angiography to lack accuracy in determining the severity of intermediate stenosis. Difficulties
with normal reference segment determination, complex and eccentric lesion assessment, and the inability to visualize the plaque directly may explain the poor accuracy in intermediate lesion quantification. Nevertheless, our population was selected with clinical symptoms and/or evidence of myocardial ischemia and moderate stenosis by angiography. This introduced a selection bias that did not allow a comparison between CT and angiography. Because of bright elements shadowing the lumen, lesion calcification has been shown to be hazardous when analyzed using CT.17 In our study, no lesion was excluded because of heavy calcium. Our patient population selection with limited previous cardiac events and 56% acute coronary syndromes involving possibly young nonstenotic plaques probably explains the reduced amount of heavy and diffuse calcified lesions.18 The use of cross-sectional reconstruction for measurement allows calcification localization regarding the lumen. Thus, lumen and plaque are well defined for acceptable contour tracing. Some difficulties were observed when calcification and contrast agent were in the same range of density. 1. Martuscelli E, Romagnoli A, D’Eliseo A, Razzini C, Tomassini M, Sperandio M, Simonetti G, Romeo F. Accuracy of thin-slice computed tomography in the detection of coronary stenoses. Eur Heart J 2004; 25:1043–1048. 2. Nieman K, Cademartiri F, Lemos PA, Raaijmakers R, Pattynama PM, de Feyter PJ. Reliable noninvasive coronary angiography with fast
528
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5.
6.
7.
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9.
10.
The American Journal of Cardiology (www.AJConline.org) submillimeter multislice spiral computed tomography. Circulation 2002;106:2051–2054. Ropers D, Baum U, Pohle K, Anders K, Ulzheimer S, Ohnesorge B, Schlundt C, Bautz W, Daniel WG, Achenbach S. Detection of coronary artery stenoses with thin-slice multi-detector row spiral computed tomography and multiplanar reconstruction. Circulation 2003;107: 664 – 666. Giesler T, Baum U, Ropers D, Ulzheimer S, Wenkel E, Mennicke M, Bautz W, Kalender WA, Daniel WG, Achenbach S. Noninvasive visualization of coronary arteries using contrast-enhanced multidetector CT: influence of heart rate on image quality and stenosis detection. AJR 2002;179:911–916. Kopp AF, Schroeder S, Kuettner A, Baumbach A, Georg C, Kuzo R, Heuschmid M, Ohnesorge B, Karsch KR, Claussen CD. Non-invasive coronary angiography with high resolution multidetector-row computed tomography: results in 102 patients. Eur Heart J 2002;23:1714 – 1725. Paul JF, Ohanessian A, Caussin C, Hennequin R, Dambrin G, Brenot P, Lancelin B, Angel C. Visualization of coronary tree and detection of coronary artery stenosis using 16-slice, sub-millimeter computed tomography: preliminary experience. Arch Mal Coeur Vaiss 2004;97: 31–36. Kuettner A, Trabold T, Schroeder S, Feyer A, Beck T, Brueckner A, Heuschmid M, Burgstahler C, Kopp AF, Claussen CD. Noninvasive detection of coronary lesions using 16-detector multislice spiral computed tomography technology: initial clinical results. J Am Coll Cardiol 2004;44:1230 –1237. Abizaid AS, Mintz GS, Abizaid A, Mehran R, Lansky AJ, Pichard AD, Satler LF, Wu H, Kent KM, Leon MB. One-year follow-up after intravascular ultrasound assessment of moderate left main coronary artery disease in patients with ambiguous angiograms. J Am Coll Cardiol 1999;34:707–715. Abizaid AS, Mintz GS, Mehran R, Abizaid A, Lansky AJ, Pichard AD, Satler LF, Wu H, Pappas C, Kent KM, Leon MB. Long-term follow-up after percutaneous transluminal coronary angioplasty was not performed based on intravascular ultrasound findings: importance of lumen dimensions. Circulation 1999;100:256 –261. Di Mario C, Gorge G, Peters R, Kearney P, Pinto F, Hausmann D, von Birgelen C, Colombo A, Mudra H, Roelandt J, Erbel R, for the Study Group on Intracoronary Imaging of the Working Group of Coronary Circulation and of the Subgroup on Intravascular Ultrasound of the
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Working Group of Echocardiography of the European Society of Cardiology. Clinical application and image interpretation in intracoronary ultrasound. Eur Heart J 1998;19:207–229. Mintz GS, Nissen SE, Anderson WD, Bailey SR, Erbel R, Fitzgerald PJ, Pinto FJ, Rosenfield K, Siegel RJ, Tuzcu EM, Yock PG. American College of Cardiology Clinical Expert Consensus Document on Standards for Acquisition, Measurement and Reporting of Intravascular Ultrasound Studies (IVUS). A report of the American College of Cardiology Task Force on Clinical Expert Consensus Documents. J Am Coll Cardiol 2001;37:1478 –1492. Achenbach S, Moselewski F, Ropers D, Ferencik M, Hoffmann U, MacNeill B, Pohle K, Baum U, Anders K, Jang IK, Daniel WG, Brady TJ. Detection of calcified and noncalcified coronary atherosclerotic plaque by contrast-enhanced, submillimeter multidetector spiral computed tomography: a segment-based comparison with intravascular ultrasound. Circulation 2004;109:14 –17. Caussin C, Ohanessian A, Lancelin B, Rahal S, Hennequin R, Dambrin G, Brenot P, Angel CY, Paul JF. Coronary plaque burden detected by multislice computed tomography after acute myocardial infarction with near-normal coronary arteries by angiography. Am J Cardiol 2003;92:849 – 852. Moselewski F, Ropers D, Pohle K, Hoffmann U, Ferencik M, Chan RC, Cury RC, Abbara S, Jang IK, Brady TJ, Daniel WG, Achenbach S. Comparison of measurement of cross-sectional coronary atherosclerotic plaque and vessel areas by 16-slice multidetector computed tomography versus intravascular ultrasound. Am J Cardiol 2004;94: 1294 –1297. Gronenschild E, Janssen J, Tijdens F. CAAS. II: a second generation system for off-line and on-line quantitative coronary angiography. Cathet Cardiovasc Diagn 1994;33:61–75. Baptista J, Arnese M, Roelandt JR, Fioretti P, Keane D, Escaned J, Boersma E, di Mario C, Serruys PW. Quantitative coronary angiography in the estimation of the functional significance of coronary stenosis: correlations with dobutamine-atropine stress test. J Am Coll Cardiol 1994;23:1434 –1439. Achenbach S. Detection of coronary stenoses by multidetector computed tomography: it’s all about resolution. J Am Coll Cardiol 2004; 43:840 – 841. Virmani R, Burke AP, Kolodgie FD, Farb A. Vulnerable plaque: the pathology of unstable coronary lesions. J Interv Cardiol 2002;15:439 – 446.
A total of 54 patients who were admitted to our institution for suspected myocardial ischemia and in whom angiography showed moderate stenosis (30% to 60% by visual assessment) were selected for the study. Suspicion for myocardial ischemia was present with clinically typical chest pain, chest pain and ST-T modification on an electrocardiogram at rest or exercise test or nuclear imaging with positive findings. The exclusion criteria were renal insufficiency, intolerance to iodinated contrast media, and the presence of arrhythmias. All patients underwent angiography, IVUS, and 16-slice CT within 72 hours and before revasculariza-
a
Hôpital Marie Lannelongue, Le Plessis Robinson, France; and bHôpital Inter-Armée Percy, Clamart, France. Manuscript received December 2004; revised manuscript received and accepted April 1, 2005. * Corresponding author: Tel: 33-1-40-94-28-00; fax: 33-1-40-94-55-84. E-mail address: [email protected]. (C. Caussin) 0002-9149/05/$ – see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.amjcard.2005.04.013
tion. The location of the target lesion was selected on the angiograms and IVUS scans and was defined using the American College of Cardiology/American Heart Association classification for CT analysis. The institutional review board approved the research protocol, and all patients gave informed consent. Angiography was performed by experienced operators. At least 2 orthogonal views were acquired to optimize the stenosis evaluation. The angiograms were reviewed by an operator unaware of the IVUS and CT results. Quantitative coronary angiography was performed using the CAAS II algorithm.15 Calibrating with the outer diameter of the contrast-empty catheter, the minimal lumen diameter in diastole from the “worst” view was determined. The diameter stenosis percentage was measured and the area stenosis percentage determined. Lesion significance was determined using 2 different methods as defined in previous studies: (1) using the minimal lumen diameter, a lesion was considered significant if the minimal lumen diameter was ⬍2.0 mm8 for the left main or ⬍1.5 mm9 for the other epicardial vessels; and (2) using the diameter stenosis percentage if the stenosis was ⬎50% regardless of the artery.16 IVUS was performed in the suspected target lesion, according to the angiographic findings, electrocardiographic findings, or ventricular damage. Another suspected culprit artery could be explored at the discretion of the operator if necessary. The IVUS catheter used was a 40-MHz Atlantis (Boston Scientific, Boston, Massachusetts). A first motorized pullback was performed at 0.5 mm/s, starting ⬎10 mm distal to the lesion and ending at the aorto-ostial junction. A second manual pullback was performed at the tightest sites, with a 5- to 8-ml saline flush to allow a better visualization of the lumen contour. Images were recorded on s-VHS videotape for off-line analysis. MLA was manually traced by 2 independent operators (CC and SG), who were unaware of the CT findings, according to the American College of Cardiology clinical expert consensus document.11 A significant lesion was defined as a ⱕ6 mm2 MLA8 for the www.AJConline.org
Coronary Artery Disease/16-Slice CT Versus IVUS in Intermediate Stenosis
525
Table 1 Demographic data, presentation, and culprit artery of selected population (n ⫽ 51) Variable
n (%)
Age (yrs) (mean ⫾ SD) Hypercholesterolemia ⬎240 mg/dl Smoker Diabetes mellitus Hypertension Previous myocardial infarction Previous coronary angioplasty Previous coronary bypass Acute myocardial infarction Unstable angina pectoris Stable angina pectoris Silent ischemia Culprit coronary artery Left main Left anterior descending Left circumflex Right
62 ⫾ 13 31 (61%) 25 (49%) 9 (18%) 32 (63%) 6 (12%) 10 (20%) 4 (8%) 5 (10%) 24 (46%) 11 (22%) 11 (22%) 10 (20%) 26 (51%) 3 (6%) 12 (24%)
left main and a ⱕ4 mm2 MLA9 for the other epicardial vessels. All patients underwent a retrospective electrocardiogram, gated 16-slice CT (Sensation 16, Siemens, Forchheim, Germany). Patients with a heart rate of ⬎60 beats/min received 100 mg of metoprolol 1 hour before performing CT to obtain optimal image quality. The rotation time was 420 ms, accounting for a total breath-hold of about 20 seconds. The CT images were acquired on 210 ms at the end of diastole. The position of the reconstruction window within the cardiac cycle was individually chosen to minimize motion artifacts. The slice thickness was 0.75 mm, with 0.5-mm increments of reconstruction. Maximal intensity projection and multiplanar reconstruction were used to select the tightest site. Then, the measurements were performed on cross-sectional artery reconstruc-
Figure 1. Scatterplots showing significant correlation (Y ⫽ 1.592 ⫹ 0.791X, r ⫽ 0.73, p ⬍0.001) between CT MLA and IVUS MLA.
Figure 2. MLA IVUS and CT Bland-Altman analysis. Solid line, systematic error (mean difference ⫺8%); hatched lines, limits of agreement (95% confidence interval ⫺72% to ⫹56%).
tion. MLA was manually drawn on cross-sectional reconstruction using a setting of 500-Hounsfield unit window and 150-Hounfield unit level. A significant lesion was defined as a ⱕ6 mm2 MLA for the left main and a ⱕ4 mm2 MLA for the other epicardial vessels. Two independent operators (JFP and BD), who were unaware of the IVUS findings, reconstructed the data and manually traced the contours. The reference value for IVUS comparison was the mean value of the 2 operators. The values are expressed as the mean ⫾ SD. Correlation between IVUS and CT was performed using Pearson’s correlation coefficient and Bland-Altman analysis. CT interobserver variability was expressed as the SD between the different CT operator findings. CT tracing variability was also assessed and expressed as the SD between operator tracings on the same image. The mean values of the 2 operators were compared with the IVUS findings. The sensitivity, specificity, accuracy, and Fisher’s exact test were used for significant lesion classification comparisons. Of the 54 patients screened, 1 was excluded because of a poor quality CT due to motion artifact, 2 were excluded because of IVUS problems (failure to cross the lesion for 1 because of proximal tortuosity and damage of the video tape for 1). All data were analyzed for the remaining 51 patients. The demographic data are listed in Table 1. The angiographic measurement revealed a reference diameter of 3.2 ⫾ 0.6 mm, minimal lumen diameter of 2.0 ⫾ 0.5 mm, diameter stenosis of 35.7 ⫾ 8.4%, and area stenosis of 53.7 ⫾ 16.1%. The MLA with IVUS was 5.7 ⫾ 2.5 mm2 and with CT was 6.1 ⫾ 2.7 mm2. Pearson’s correlation coefficient between CT MLA and IVUS MLA was r ⫽ 0.73 (p ⬍0.001; Figure 1). The interobserver variability for CT was 2.0 mm2 (36%). The CT tracing variability was 1.9 mm2 (31%). The variability for CT measurement compared with IVUS was 1.9 mm2 (32%). The systematic error (IVUS ⫺ CT) was ⫺8%.
526
The American Journal of Cardiology (www.AJConline.org)
Figure 3. Coronary angiogram (top left), 16-slice CT longitudinal (top right) and left main cross-sectional reconstruction (bottom right), and IVUS (bottom left) of 75-year-old woman admitted for typical rest chest pain. Angiogram shows significant 57% ostial left main stenosis, minimal lumen diameter was 1.6 mm. Longitudinal CT reconstruction showed left main moderate stenosis, MLA measured on cross-sectional reconstruction was nonsignificant (17 mm2); this was confirmed by IVUS (MLA 15 mm2).
Figure 4. Right coronary angiogram (left), 16-slice CT cross-sectional reconstruction (bottom right), and IVUS (top right) of 48-year-old patient admitted for chest pain and electrocardiogram showing transient D2, D3, VF ST-T depression. This patient had undergone previous coronary bypass grafting on left anterior descending artery, obtuse margin, and diagonal branch. Angiogram showed graft patency and moderate stenosis on mild right coronary artery (minimal lumen diameter 2.26 mm and percentage of stenosis 37%). CT showed large plaque burden with 4.0-mm2 MLA. IVUS confirmed CT findings with significant 3.5-mm2 MLA.
Coronary Artery Disease/16-Slice CT Versus IVUS in Intermediate Stenosis
527
Figure 5. Coronary angiogram (left), 16-slice CT cross-sectional reconstruction (bottom right), and IVUS (top right) of 64-year-old woman admitted for stable angina with positive bicycle test. Angiography showed only moderate stenosis on mild left anterior descending artery (minimal lumen diameter 1.68 mm and 26% stenosis). CT detected significant stenosis with 3-mm2 MLA, IVUS confirmed significant stenosis with 2.3-mm2 MLA.
The 95% confidence interval for MLA evaluation by CT was ⫺72% to ⫹56% (Figure 2 for Bland-Altman analysis). Regarding lesion classification, 22 of 51 lesions (43%) were considered significant using IVUS. The sensitivity, specificity, and accuracy for CT to classify significant lesions was 68%, 86%, and 78%, respectively (p ⬍0.0001). The sensitivity, specificity, and accuracy for quantitative angiography to classify significant lesions was 10%, 96%, and 59% (p ⫽ NS) for the stenosis percentage and 26%, 89%, and 61% for the minimal lumen diameter (p ⫽ NS), respectively. Figures 3 to 5 show the angiographic, IVUS, and CT films for 3 different patients. •••
The results of the present study have shown the feasibility of MLA quantification using 16-slice CT on cross-sectional artery reconstruction. An acceptable correlation between the IVUS and CT findings was found in ambiguous intermediate lesions by angiography. The severity of narrowing could be assessed with reasonable accuracy using MLA on crosssectional reconstruction. Despite a lower spatial resolution than angiography, CT measurement permitted direct atheroma visualization and lumen assessment. Concerning 16-slice CT atheroma evaluation, systematic use of IVUS provided an accurate reference for atheroma severity determination. As in other studies,8,9 our study showed quantitative angiography to lack accuracy in determining the severity of intermediate stenosis. Difficulties
with normal reference segment determination, complex and eccentric lesion assessment, and the inability to visualize the plaque directly may explain the poor accuracy in intermediate lesion quantification. Nevertheless, our population was selected with clinical symptoms and/or evidence of myocardial ischemia and moderate stenosis by angiography. This introduced a selection bias that did not allow a comparison between CT and angiography. Because of bright elements shadowing the lumen, lesion calcification has been shown to be hazardous when analyzed using CT.17 In our study, no lesion was excluded because of heavy calcium. Our patient population selection with limited previous cardiac events and 56% acute coronary syndromes involving possibly young nonstenotic plaques probably explains the reduced amount of heavy and diffuse calcified lesions.18 The use of cross-sectional reconstruction for measurement allows calcification localization regarding the lumen. Thus, lumen and plaque are well defined for acceptable contour tracing. Some difficulties were observed when calcification and contrast agent were in the same range of density. 1. Martuscelli E, Romagnoli A, D’Eliseo A, Razzini C, Tomassini M, Sperandio M, Simonetti G, Romeo F. Accuracy of thin-slice computed tomography in the detection of coronary stenoses. Eur Heart J 2004; 25:1043–1048. 2. Nieman K, Cademartiri F, Lemos PA, Raaijmakers R, Pattynama PM, de Feyter PJ. Reliable noninvasive coronary angiography with fast
528
3.
4.
5.
6.
7.
8.
9.
10.
The American Journal of Cardiology (www.AJConline.org) submillimeter multislice spiral computed tomography. Circulation 2002;106:2051–2054. Ropers D, Baum U, Pohle K, Anders K, Ulzheimer S, Ohnesorge B, Schlundt C, Bautz W, Daniel WG, Achenbach S. Detection of coronary artery stenoses with thin-slice multi-detector row spiral computed tomography and multiplanar reconstruction. Circulation 2003;107: 664 – 666. Giesler T, Baum U, Ropers D, Ulzheimer S, Wenkel E, Mennicke M, Bautz W, Kalender WA, Daniel WG, Achenbach S. Noninvasive visualization of coronary arteries using contrast-enhanced multidetector CT: influence of heart rate on image quality and stenosis detection. AJR 2002;179:911–916. Kopp AF, Schroeder S, Kuettner A, Baumbach A, Georg C, Kuzo R, Heuschmid M, Ohnesorge B, Karsch KR, Claussen CD. Non-invasive coronary angiography with high resolution multidetector-row computed tomography: results in 102 patients. Eur Heart J 2002;23:1714 – 1725. Paul JF, Ohanessian A, Caussin C, Hennequin R, Dambrin G, Brenot P, Lancelin B, Angel C. Visualization of coronary tree and detection of coronary artery stenosis using 16-slice, sub-millimeter computed tomography: preliminary experience. Arch Mal Coeur Vaiss 2004;97: 31–36. Kuettner A, Trabold T, Schroeder S, Feyer A, Beck T, Brueckner A, Heuschmid M, Burgstahler C, Kopp AF, Claussen CD. Noninvasive detection of coronary lesions using 16-detector multislice spiral computed tomography technology: initial clinical results. J Am Coll Cardiol 2004;44:1230 –1237. Abizaid AS, Mintz GS, Abizaid A, Mehran R, Lansky AJ, Pichard AD, Satler LF, Wu H, Kent KM, Leon MB. One-year follow-up after intravascular ultrasound assessment of moderate left main coronary artery disease in patients with ambiguous angiograms. J Am Coll Cardiol 1999;34:707–715. Abizaid AS, Mintz GS, Mehran R, Abizaid A, Lansky AJ, Pichard AD, Satler LF, Wu H, Pappas C, Kent KM, Leon MB. Long-term follow-up after percutaneous transluminal coronary angioplasty was not performed based on intravascular ultrasound findings: importance of lumen dimensions. Circulation 1999;100:256 –261. Di Mario C, Gorge G, Peters R, Kearney P, Pinto F, Hausmann D, von Birgelen C, Colombo A, Mudra H, Roelandt J, Erbel R, for the Study Group on Intracoronary Imaging of the Working Group of Coronary Circulation and of the Subgroup on Intravascular Ultrasound of the
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13.
14.
15.
16.
17.
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