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Quantification of Atherosclerotic Burden in the Descending Aorta by Transesophageal Echocardiography

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Quantification of Atherosclerotic Burden in the Descending Aorta by Transesophageal Echocardiography
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  Quantification of Atherosclerotic Burden in the Descending Aorta by Transesophageal Echocardiography zy   z nter- and Intraobserver Variability ZAHI KHOURY, M.D., CHON1 RINAT, JESAIA BENHORIN, M.D., SHLOMO STERN, M.D., FACC, and ANDRE KEREN, M.D., FACC Heiden Department of Cardiology, Bikur Cholim Hospital and the Hebrew University-Hadassah Medical School, Jerusalem, Israel zyx Atherosclerotic plaques had been imaged but not quantitated in the thoracic aorta using trans- esophageal echocardiography. The aim of this study was to describe a method for measuring the ath- erosclerotic plaque area in the descending aorta by transesophageal echocardiography (TEE) and to evaluate its reproducibility. TEE examinations were performed by two independent sonographers, in 21 patients with angiographically proven coronary artery disease. Two hundred fifty-six transverse segments (mean 12 zyxwv   zyxwvut   patient) of the descending aorta were adequately recorded. In each segment the plaque and the lumen areas in the half of the aortic segment distant from the transesophageal probe were measured by one reader in the two studies (intersonographer reproducibility). Interreader reproducibility was also evaluated. The correlation coefficient between the first and second study in- tersonographer reproducibility) was 0.81. The standard deviation of the difference between exami- nations equaled 0.137 cm2 and the mean absolute difference between examinations was 0.003 cmz (95 CI: -0.015; 0.021; P = 0.75 . The correlation coefficient between the two readers was 0.86, the standard deviation of the difference between readers was 0.175 cm2 and the mean absolute difference was 0.006 zyxwvutsr m (95 CI: -0.029; 0.018; P = 0.63). A method for quantitative measurement of aortic atherosclerotic plaque area was evaluated and found to have high intersonographer and intereader reproducibilities. This method might be used in the future for noninvasive evaluation of regression or progression of aortic atherosclerosis. (ECHOCARDIOGRAPHY, Volume 15, January 1998) aortic atherosclerosis, transesophageal echocardiography, plaque area, reproducibility Atherosclerosis of the descending aorta is common in patients with coronary artery'J and cerebrovascular di~ease.~ he extent of coronary atherosclerosis has been quantified by angiog- raphy and intravascular ultrasound.46 n the ca- rotid arteries, B-mode ultrasound and Doppler methods have been sucessfully used for quanti- tative analysis of atherosclerotic plaques and luminal narro~ings.~-'~ ecently, transesoph- ageal echocardiography (TEE) demonstrated atherosclerotic plaques in the thoracic a~rta.*~J~ There are, however, no data on quantitation of the extent of the atherosclerotic process in the descending aorta by an ultrasonic method, even though a reliable and reproducible ultrasonic method could Serve as a useful and low cost ool for follow-up of this process. This study describes a reproducible method for measurement of atherosclerotic plaque and Part of this investigation was presented at the 43rd zyxwvu n- nual Scientific Session of the American College of Cardiol- ogy, Atlanta, Georgia 1994. Address for correspondence and reprints: Zahi Khoury, M.D., The Heiden Department of Cardiology, Bikur Cholim Hospital, P.O. Box 492, Jerusalem 91004 Israel. Fax: 972-2-243599. lumen areas in the descending aorta. Vol. 15 No. 1 1998 ECHOCARDIOGRAPHY: A Jrnl. of CV Ultrasound Allied Tech. 59  KHOURY, ET AL. 60 zyxwvutsrqp CHOCARDIOGRAPm A Jrnl. of CV Ultrasound zyx   Allied Tech. Vol. 15, No. 1, 1998 Methods zyxwvu opulation Twenty-one consecutive patients with signif- icant coronary disease ( zyxwvut   709 stenosis in 1 major coronary artery by coronary angiogra- phy) underwent two blinded TEE examina- tions within 1 week of the angiogram; the stud- ies were performed and interpreted by experi- enced physicians. Of the 21 patients, 18 (86 ) were males, their age range was 41-80 years (mean 64 years). Hypercholesterolemia was found in zyxwvutsr 3 ; 53 were hypertensive; 57% were smokers; and 10 were diabetics. The study protocol was approved by the Hospital’s Medical Ethics Committee and all patients gave informed consent to undergo the echocar- diographic examinations. Echocardiographic Examinations The TEE examinations were performed us- ing a 5 MHz phased array biplane transducer connected to either a Hewlett-Packard Sonos 1000 or 1500 echocardiographic system (Hewlett-Packard, Andover, MA, USA). Pa- tients fasted at least 4 hours and the orophar- ynx was anesthetized with an aerosolized topi- cal solution of lidocaine. Patients were sedated using 5 mg of zyxwvu V diazepam. After a conven- tional cardiac examination, the descending thoracic aorta was divided into 15 segments in the transverse view, 1 cm apart from each other, beginning 25 cm below the incisors to the level of the diaphragm. This part of the aorta was chosen because it is relatively linear compared to the aortic arch. Each study lasted for 15 minutes and was recorded on a separate SVHS tape. The two sonographers were blinded to each other’s results, to the clinical status and to the coronary angiographic re- sults of the patients. At each level of the de- scending aorta a still frame was recorded. Echocardiograph ic Analysis Aortic intimal changes were graded simi- larly to Fazio et al.I5 The thoracic aorta was considered normal with respect to atheroscle- rotic disease when the intimal surface was smooth and continuous without lumen irregu- larities or increased echo density. Increased echo density or thicking of the aortic intimal surface was considered an aortic plaque. At each level only the half of the aortic cross sec- tion that was remote from the echocardio- graphic probe was analyzed because the half of the aortic cross section adjacent to the esophagus is usually out of focus (Fig. 1A). Af- ter defining the outer borders of the remote half of the aortic cross section by tracing at half the maximal anteroposterior aortic diam- eter (Fig. lB, Point Z), lumen and plaque ar- eas within each segment were calculated us- ing the software of the echocardiographic sys- tem (Figs. 1C and 1D). An average of 12 zyx   3 segments in each study and a total of 256 segments were adequately recorded and analyzed. Mean plaque and lu- men areas per patient were defined as the av- erage of plaque and lumen areas, respectively, in all segments studied in the same patient. To evaluate intersonographer reproducibil- ity, immediately following the first study, a second independent study was performed by a sonographer blinded to the findings of the first study. Interreader reproducibility was as- Figure 1. Transesophageal echocardiogram (TEE) demonstrating a transverse section of the descending aorta at 37 cm from the incisors demonstrating aor- tic plaque (A) (arrow) lumen area (C). Plaque area D) t the distal half of the cross section are marked. XY is the anteroposterior diameter and Z is half the anteroposterior diameter B).  MEASUREMENT OF ATHEROSCLEROSIS zyxw ~ z ABLE I Intersonographer Variability of Mean Aortic Plaque and Lumen Areas (n = 21) Plaque.Area (cm') Lumen Area (cm') Examinations Mean zyxwvuts   SD Range Mean zyx   SD Range ~~~ First 0.37 -C 0.31 0.06-1.26 2.18 k 0.57 1.09-3.87 Second 0.37 -C 0.29 0.05-1.27 2.16 .63 1.134.14 r 0.98 - 0.99 Absolute difference between examinations 0.001 t .039 0.02 zyx   0.095 95% CI (-0.017; 0.019) - (-0.028; 0.061) P 0.94 - 0.46 - CI = confidence intervals; P = student's paired t-test; r = Pearson correlation coefficient between first and second examinations. sessed by analyzing each study by two readers, each blinded to the interpretation given by the other. patient. segments we used repeat analysis of variance in 12 segments as repetitions within any given Statistical Analysis Results Intersonographer and interreader variabili- ties were assessed by Pearson's correlation co- efficient and the mean difference between ex- Intersonographer and Interreader Variability in 21 Patients aminations. To account for possible high corre- lations that are involved with significant systematic errors, all paired readings were lin- early regressed and then compared by the Stu- dent's paired t-test. In the second phase of the analysis, we ex- cluded the possibility that the reported repro- ducibilities (intersonographer and interreader) are dependent on specific aortic segments. To examine the homogeneity of the results across The correlations of mean plaque and lumen areas in the two echocardiographic studies are shown in Table I. The correlations for the same parameters analyzed from the same study by two independent readers are shown in Table 11. Correlation coefficients (r) ranged from 0.97-0.99. The mean absolute intersonogra- pher and interreader difference for the plaque area were 0.001 cm2 (0.3 ) and 0.006 cm2 (1.6%), respectively. These correlations were TABLE I1 Interrearder Variability of Mean Aortic Plaque and Lumen Areas (n = 21) Plaque Area (cm2) Lumen Area (cm') Readers Mean ? SD Range Mean D Range 1.09-3.87 irst 0.37 0.29 0.02-1.53 2.16 0.58 Second 0.37 -C 0.39 0.06-1.50 2.15 .6 r Absolute difference between readings 0.005 zyxwvuts   0.07 0.01 zyx   0.113 - 95% CI (-0.038; 0.027) (-0.039; 0.067) P 0.73 - 0.58 - 1.13-3.67 0.97 0.98 - CI = confidence interval; P = student's paired t-test; r = Pearson correlation coefficient between first and second readers. Vol. 15, No. 1,1998 ECHOCARDIOGRAPHY: A Jml. of CV zyxw ltrasound Allied Tech. 61  KHOURY, ET zyxw L /---/ / z   / j___ _ Y = zyx   29 1 013X R = 0 97 zyx   = 21 Y ,,,,I//,, Q I fll1IlI 0 01 02 03 zyxwvutsrqponmlkjihg 4 05 06 07 08 09 1 11 12 13 0 01 02 03 4 05 0.6 07 08 09 1 11 12 1.3 zyx A MEAN PLAQUE AREA, EXAMINATION 1 MEAN PLAQUE AREA, READER 2 B Figure 2 A zyxwvutsrq catter plot demonstrating the correlation between mean plaque area measurements by two sono graphers (A1 and two readers B) n 21 patients (cmZ). Correlation coeficients were zyx .98 and 0.97, respectively. confirmed by linear regression analysis (Figs. Repeated measures analysis of variance 2A and 2B). with 12 segments as repetitions within all pa- tients showed no significant differences (P > Correlation Between Repeated Measurements 0.05) across segments in intersonographer and of Plaque and Lumen Areas in 256 Aortic interreader reproducibilities for both plaque Segments and lumen area measurements. I1 and IiJ and Figs. 3A and 3B Correlation Between Plaque and Lumen Areas in 256 Segments he high correlation coefficients between re- peated plaque and lumen area measurments in - each segment analyzed by different readers or Figure 4 hows the lack of a strong correla- performed by different sonographers. The cor- tion (r = 0.42) between plaque and lumen ar- relation coefficients between measurements eas in the 256 segments analyzed. Segments based on 256 aortic segment were obviously with a large plaque area did not show a sig- somewhat lower than those based on mean Val- nificant reduction in lumen area; on the con- ues per patient. trary, there was a mild trend for compen- TABLE I11 Intersonographer Variability of Aortic Plaque and Lumen Area Measurements in 256 Segments Examinations Plaque Area (cm2) Lumen Area (cm7 Mean SD Range Mean t SD Range First 0.36 .33 0.0-2.04 2.17 ? 0.58 0.95-4.77 Second 0.36 0.31 0.0-1.63 2.15 .63 0.944.70 r Absolute difference 0.81 0.93 - between examinations 0.003 t 0.137 0.02 .024 - 95 CI (-0.015; 0.021) - (-0.012; 0.051 - P 0.75 - 0.23 - Abbreviations as in Table I. 62 ECHOCARDIOGRAPHY: A Jd. f CV Ultrasound Allied Tech. Vol. 15, No. 1,1998  MEASUREMENT OF ATHEROSCLEROSIS zyxw   z TABLE zyxwv V Interrearder Variability of Aortic Plaque and Lumen Area Measurements in 256 Segments Plaque Area (em2) Readers Mean zyxwvutsr   SD Range First 0.36 0.31 0.0-2.04 Second 0.36 _t 0.34 0.0-2.24 r Absolute difference 0.86 - between readings 0.006 0.175 - 95 CI (-0.029; 0.018) - P 0.63 Lumen Area (cm2) Mean ? SD Range 2.17 0.59 0.89-4.62 2.16 0.68 0.97-4.54 0.96 0.01 ? 0.130 (-0.018; 0.039) 0.20 Abbreviations as in Table 11. satory dilatation of segments with a large plaque area. Discussion This study indicates that the measurement of the atherosclerotic plaque area in the de- scending aorta is feasible by TEE. The repro- ducibility was high for both mean plaque area per patient and plaque area per segment. Lu- men areas had slightly better intersonographer and intereader reproducibilities than plaque areas. This reproducibility was achieved by careful definition of the probe level relative to the incisor teeth, without change in the angle of the distal probe during withdrawal. zyxwv Y 0 019 0 955X R- 0.81 256 zyxwvutsrqpon   05 15 2 A PLAQUE AREA, EXAMINATION 2 zyxwvutsrq Imaging zyx f Atherosclerosis Methods that had been previously used for detection of arterial luminal narrowings used primarily angiography and Doppler; however, their accuracy and reproducibility were lim- ited.5J6-1a n the extracranial carotid arteries, Doppler ultrasound has been used to accurately estimate the degree of stenosis.7-12 -mode ultra- sound was used to image the arterial wall, by measuring intimal-medial thickness for the grading of ather~~cler~~i~.~~~'~ ~ everal studies correlated the plaque morphology with the clin- ical outcome and clarified the association be- tween risk factors and plaque compo~ition.~~-~~ The chararcteristic B scan pattern of normal ca- Y= 0066rO905X R = 0 86 -i = 2113 I I 05 1 15 2 PLAQUE AREA, READER 2 B Figure 3. A scatter plot demonstrating the correlation between plaque area measurements by two sonographers (A) and two readers (B) in 256 aortic segments (cm2). Correlation coeficients were 0.81 and 0.86 respectiuely. Vol. 15, No. 1, 1998 ECHOCARDIOGRAPHY: A Jml. of CV Ultrasound Allied Tech. 63
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