- Email: [email protected]
Prevalence of an Increased Ascending Thoracic Aorta Diameter Diagnosed by Two-Dimensional Echocardiography Versus 64-Multislice Cardiac Computed Tomography
Prevalence of an Increased Ascending Thoracic Aorta Diameter Diagnosed by Two-Dimensional Echocardiography Versus 64-Multislice Cardiac Computed Tomography Sarah Kaplan, MDa, Wilbert S. Aronow, MDa,*, Chul Ahn, PhDc, Hoang Lai, MDa, Albert J. DeLuca, MDa, Melvin B. Weiss, MDa, Hajir Dilmanian, MDa, David Spielvogel, MDb, Steven L. Lansman, MD, PhDb, and Robert N. Belkin, MDa The prevalence of an enlarged ascending thoracic aortic diameter (AAD) diagnosed by 2-dimensional echocardiography compared with 64-slice cardiac computed tomography (MSCT) was investigated in 97 women and 117 men (mean age 65 ⴞ 12 years). Enlarged AADs were diagnosed in 42 of 214 patients (20%) by echocardiography and in 45 of 214 patients (21%) by MSCT (p ⴝ NS). The sensitivity, specificity, positive predictive value, and negative predictive value of echocardiography in diagnosing an enlarged AAD using MSCT were 69%, 93%, 74%, and 92%, respectively. A Bland-Altman plot showed that the agreement for AAD measured by echocardiography and MSCT was 95% inside the 2-SD limits. In conclusion, the sensitivity, specificity, positive predictive value, and negative predictive value of 2-dimensional echocardiography in diagnosing enlarged AAD using MSCT were 69%, 93%, 74%, and 92%, respectively. © 2008 Elsevier Inc. All rights reserved. (Am J Cardiol 2008;101:119 –121) To the best of our knowledge, the prevalence of an enlarged ascending thoracic aortic diameter (AAD) diagnosed by 2-dimensional echocardiography has not been compared with an enlarged AAD diagnosed by 64-slice cardiac computed tomography (MSCT). The present study was performed to report the prevalence of an enlarged AAD diagnosed using 2-dimensional echocardiography and MSCT in a cohort of 214 consecutive patients. Methods and Results Two hundred fourteen consecutive outpatients at an academic cardiology practice underwent 2-dimensional echocardiography and MSCT for the clinical indications of chest pain or positive stress test results. Clinical consent for performing 2-dimensional echocardiography and MSCT was obtained from all 214 patients. Echocardiographic and multislice computed tomographic procedure reports and demographic data for each patient were retrospectively reviewed. The 214 patients included 117 men and 97 women (mean age 65 ⫾ 12 years, range 24 to 87). Complete 2-dimensional echocardiographic and Doppler studies were performed according to conventional methods using Philips 5500 cardiac ultrasound systems (Philips Medical Systems, Eindhoven, The Netherlands). Images of the ascending thoracic aorta were obtained in the parasternal long-axis view. In addition to visualizing the most proximal segment of the aorta, our protocol includes routine angulaa
Department of Medicine, Cardiology Division, and bDepartment of Surgery, Division of Cardiothoracic Surgery, New York Medical College, Valhalla, New York; and cDepartment of Medicine, University of Texas School of Medicine, Houston, Texas. Manuscript received June 14, 2007; revised manuscript received and accepted July 9, 2007. *Corresponding author: Tel: 914-493-5311; fax: 914-235-6274. E-mail address: [email protected] (W.S. Aronow). 0002-9149/08/$ – see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.amjcard.2007.07.081
tion of the transducer to image as large a segment of the ascending aorta above the level of the sinuses of Valsalva as feasible. All echocardiograms were reviewed by 1 of 2 experienced physician echocardiographers, who made the inner-to-inner measurements from the 2-dimensional echocardiograms. Measurements of the ascending aorta at the level of the sinuses of Valsalva were indicated in the final echocardiographic reports. An AAD ⬎3.6 cm at any site was considered enlarged.1 If the measurement of the visualized segment of the ascending aorta above the sinuses of Valsalva was greater than this level, the measurement was noted in the echocardiographic report. MSCT was performed using a 64-slice Siemens Somatom Sensation Cardiac scanner (Siemens Medical Solutions, Forcheim, Germany). Patients were pretreated with oral and/or intravenous  blockers to achieve heart rates ⬍65 beats/ min. A test bolus technique was used to determine scan timing. Contrast volume was determined by scan time and flow rate. Flow rates of 4 to 6 ml/s were used. Scan collimation was 32 ⫾ 0.6 cm, with dual focal spots for each detector row to allow 64 slices per rotation.2,3 Rotation time was 330 ms, pitch factor 0.2, tube voltage 120 mV, and effective milliampere-seconds 750 to 850. Electrocardiographic pulsing was used to reduce radiation dose. Gated data were reconstructed at 5% intervals from 30% to 75% of the RR interval, with 0.6-mm slice thickness and 0.4-mm increments for the purpose of coronary artery analysis. A large window view to include the descending aorta at these reconstruction parameters was used to evaluate the thoracic aorta. All studies were reviewed by 1 of 2 cardiologists experienced in MSCT. Orthogonal measurements of the ascending and descending thoracic aorta were generally obtained in axial views at the level of the bifurcation of the pulmonary artery. The full extent of each vessel was routinely evaluated on review of axial images, or in other projections if necessary. If an abnormal dimension that was www.AJConline.org
120
The American Journal of Cardiology (www.AJConline.org)
Figure 1. Bland-Altman plot indicating agreement for AAD (in centimeters) measured by 2-dimensional echocardiography and MSCT, with 204 of 214 patients (95%) within the 2-SD limits.
Figure 2. Plot of AAD (in centimeters) measured by MSCT on the y-axis versus 2-dimensional echocardiography on the x-axis.
larger than that obtained at the level of the pulmonary artery bifurcation was noted, this value was recorded. There was not, however, a systematic effort to otherwise record maximal dimensions at other sites of the aorta. An AAD ⬎3.7 cm was considered enlarged.4 The 2-dimensional echocardiograms and multislice computed tomographic studies were analyzed blindly. Student’s t tests were used for the analysis of continuous variables. The sensitivity, specificity, positive predictive value, and negative predictive value of 2-dimensional echocardiography in predicting an enlarged AAD diagnosed by MSCT were calculated. A Bland-Altman plot (Figure 1) was constructed to compare AAD measured using 2-dimen-
sional echocardiography with that measured using MSCT. For each patient, the differences in AAD measurements were plotted against the mean of the 2 measurements within 95% limits of agreement. Aortic size was plotted by MSCT on the y-axis against aortic size by 2-dimensional echocardiography on the x-axis (Figure 2), and Pearson’s correlation coefficient was calculated. The mean AAD diagnosed by 2-dimensional echocardiography was 3.3 ⫾ 0.5 cm, and the mean AAD diagnosed by MSCT was 3.4 ⫾ 0.5 cm (p ⫽ NS). Enlarged AADs were present in 42 of 214 patients (20%) by 2-dimensional echocardiography and in 45 of 214 patients (21%) by MSCT (p ⫽ NS). Table 1 lists the sensitivity, specificity,
Miscellaneous/Ascending Thoracic Aorta Diameter Table 1 Sensitivity, specificity, positive predictive value, and negative predictive value of 2-dimensional echocardiography in predicting an enlarged ascending thoracic aorta diameter diagnosed by 64-slice cardiac computed tomography Variable
%
Sensitivity Specificity Positive predictive value Negative predictive value
69 93 74 92
positive predictive value, and negative predictive value of 2-dimensional echocardiography in predicting an enlarged AAD diagnosed by MSCT. Figure 1 shows a Bland-Altman plot, which indicated that the agreement for AAD measured by 2-dimensional echocardiography and MSCT was 95%, with 10 of 214 patients (5%) outside the 2-SD limits. Figure 2 shows that Pearson’s correlation coefficient for the plot of AAD size by MSCT versus 2-dimensional echocardiography was 0.78 (p ⬍0.0001). Eight of 214 patients (4%) had AADs measured by MSCT of ⱖ4.5 cm. Of these 8 patients, the AADs measured by 2-dimensional echocardiography were ⱖ4.5 cm in 2 patients (25%), 4.0 to 4.4 cm in 2 patients (25%), and ⬍3.7 cm in 4 patients (50%). Four of 214 patients (2%) had AADs measured by 2-dimensional echocardiography of ⱖ4.5 cm. The AADs measured by MSCT in these 4 patients were 5.0, 4.7, 4.4, and 3.9 cm.
121
The use of transthoracic echocardiography for the evaluation of AAD offers the advantages of wide accessibility to large numbers of patients, relatively low cost, and the lack of need for intravenous contrast and exposure to ionizing radiation. Our data indicate that AAD measured by echocardiography correlates well with that measured by MSCT, although important limitations are present. Although specificity and negative predictive value for an enlarged AAD were each ⬎90%, the detected sensitivity and positive predictive value were not as satisfactory. Furthermore, among the small number of patients with AADs ⱖ4.5 cm, echocardiography detected this degree of enlargement in only 25% of patients and detected normal AADs in 50% of these patients. Sources of disparity between echocardiographic and multislice computed tomographic measurements likely5 include imaging artifacts with ultrasound and the inability in many cases to image the ascending aorta above its most proximal segment with echocardiography. The overestimation of MSCT may also occur when axial images are used and an oblique measurement of AAD is made in a vessel that is not perpendicular to the axial plane. Tamborini et al5 found that transthoracic echocardiography is a feasible and accurate technique for the assessment and follow-up of thoracic aorta diameters in patients with known ascending aortic aneurysms. The identification of AAD enlargement by echocardiography is a clinically useful finding and may warrant further imaging. A lack of AAD enlargement by echocardiography does not exclude such enlargement, and in selected patients, further imaging studies may still be required.
Discussion To the best of our knowledge, the prevalence of an enlarged AAD diagnosed by 2-dimensional echocardiography has not been compared with that of an enlarged AAD diagnosed by MSCT. The present study showed that enlarged AADs were present in 20% of our 214 patients by 2-dimensional echocardiography and in 21% of our patients by MSCT (p ⫽ NS). The Bland-Altman plot showed that the agreement for AAD measured by 2-dimensional echocardiography was 95% within the 2-SD limits. Pearson’s correlation coefficient for the plot of AAD size by MSCT versus 2-dimensional echocardiography was 0.78 (p ⬍0.0001). Our study also showed that the sensitivity, specificity, positive predictive value, and negative predictive value of 2-dimensional echocardiography were 69%, 93%, 74%, and 92%, respectively, in diagnosing an enlarged AAD using MSCT.
1. Feigenbaum H, Armstrong W, Ryan T. Feigenbaum’s Echocardiography. 6th ed. Philadelphia, Pennsylvania: Lea & Febiger, 2005:673. 2. Raff GL, Gallagher JM, O’Neill W. Diagnostic accuracy of noninvasive coronary angiography using 64-slice spiral computed tomography. J Am Coll Cardiol 2005;46:552–557. 3. Leber AW, Becker A, Knez A, von Ziegler F, Sirol M, Nikolaou K, Ohnesorge B, Fayad ZA, Becker CR, Reiser M, et al. Accuracy of 64-slice computed tomography to classify and quantify plaque volumes in the proximal coronary system: a comparative study using intravascular ultrasound. J Am Coll Cardiol 2006;47:672– 677. 4. Hager A, Kaemmerer H, Rapp-Bernhardt U, Blucher S, Rapp K, Bernhardt TM, Galanski M, Hess J. Diameters of the thoracic aorta throughout life as measured with helical computed tomography. J Thorac Cardiovasc Surg 2002;123:1060 –1066. 5. Tamborini G, Galli CA, Maltagliati A, Andreini D, Pontone G, Quaglia C, Ballerini G, Pepi M. Comparison of feasibility and accuracy of transthoracic echocardiography versus computed tomography in patients with known ascending aortic aneurysm. Am J Cardiol 2006;98: 966 –969.
Department of Medicine, Cardiology Division, and bDepartment of Surgery, Division of Cardiothoracic Surgery, New York Medical College, Valhalla, New York; and cDepartment of Medicine, University of Texas School of Medicine, Houston, Texas. Manuscript received June 14, 2007; revised manuscript received and accepted July 9, 2007. *Corresponding author: Tel: 914-493-5311; fax: 914-235-6274. E-mail address: [email protected] (W.S. Aronow). 0002-9149/08/$ – see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.amjcard.2007.07.081
tion of the transducer to image as large a segment of the ascending aorta above the level of the sinuses of Valsalva as feasible. All echocardiograms were reviewed by 1 of 2 experienced physician echocardiographers, who made the inner-to-inner measurements from the 2-dimensional echocardiograms. Measurements of the ascending aorta at the level of the sinuses of Valsalva were indicated in the final echocardiographic reports. An AAD ⬎3.6 cm at any site was considered enlarged.1 If the measurement of the visualized segment of the ascending aorta above the sinuses of Valsalva was greater than this level, the measurement was noted in the echocardiographic report. MSCT was performed using a 64-slice Siemens Somatom Sensation Cardiac scanner (Siemens Medical Solutions, Forcheim, Germany). Patients were pretreated with oral and/or intravenous  blockers to achieve heart rates ⬍65 beats/ min. A test bolus technique was used to determine scan timing. Contrast volume was determined by scan time and flow rate. Flow rates of 4 to 6 ml/s were used. Scan collimation was 32 ⫾ 0.6 cm, with dual focal spots for each detector row to allow 64 slices per rotation.2,3 Rotation time was 330 ms, pitch factor 0.2, tube voltage 120 mV, and effective milliampere-seconds 750 to 850. Electrocardiographic pulsing was used to reduce radiation dose. Gated data were reconstructed at 5% intervals from 30% to 75% of the RR interval, with 0.6-mm slice thickness and 0.4-mm increments for the purpose of coronary artery analysis. A large window view to include the descending aorta at these reconstruction parameters was used to evaluate the thoracic aorta. All studies were reviewed by 1 of 2 cardiologists experienced in MSCT. Orthogonal measurements of the ascending and descending thoracic aorta were generally obtained in axial views at the level of the bifurcation of the pulmonary artery. The full extent of each vessel was routinely evaluated on review of axial images, or in other projections if necessary. If an abnormal dimension that was www.AJConline.org
120
The American Journal of Cardiology (www.AJConline.org)
Figure 1. Bland-Altman plot indicating agreement for AAD (in centimeters) measured by 2-dimensional echocardiography and MSCT, with 204 of 214 patients (95%) within the 2-SD limits.
Figure 2. Plot of AAD (in centimeters) measured by MSCT on the y-axis versus 2-dimensional echocardiography on the x-axis.
larger than that obtained at the level of the pulmonary artery bifurcation was noted, this value was recorded. There was not, however, a systematic effort to otherwise record maximal dimensions at other sites of the aorta. An AAD ⬎3.7 cm was considered enlarged.4 The 2-dimensional echocardiograms and multislice computed tomographic studies were analyzed blindly. Student’s t tests were used for the analysis of continuous variables. The sensitivity, specificity, positive predictive value, and negative predictive value of 2-dimensional echocardiography in predicting an enlarged AAD diagnosed by MSCT were calculated. A Bland-Altman plot (Figure 1) was constructed to compare AAD measured using 2-dimen-
sional echocardiography with that measured using MSCT. For each patient, the differences in AAD measurements were plotted against the mean of the 2 measurements within 95% limits of agreement. Aortic size was plotted by MSCT on the y-axis against aortic size by 2-dimensional echocardiography on the x-axis (Figure 2), and Pearson’s correlation coefficient was calculated. The mean AAD diagnosed by 2-dimensional echocardiography was 3.3 ⫾ 0.5 cm, and the mean AAD diagnosed by MSCT was 3.4 ⫾ 0.5 cm (p ⫽ NS). Enlarged AADs were present in 42 of 214 patients (20%) by 2-dimensional echocardiography and in 45 of 214 patients (21%) by MSCT (p ⫽ NS). Table 1 lists the sensitivity, specificity,
Miscellaneous/Ascending Thoracic Aorta Diameter Table 1 Sensitivity, specificity, positive predictive value, and negative predictive value of 2-dimensional echocardiography in predicting an enlarged ascending thoracic aorta diameter diagnosed by 64-slice cardiac computed tomography Variable
%
Sensitivity Specificity Positive predictive value Negative predictive value
69 93 74 92
positive predictive value, and negative predictive value of 2-dimensional echocardiography in predicting an enlarged AAD diagnosed by MSCT. Figure 1 shows a Bland-Altman plot, which indicated that the agreement for AAD measured by 2-dimensional echocardiography and MSCT was 95%, with 10 of 214 patients (5%) outside the 2-SD limits. Figure 2 shows that Pearson’s correlation coefficient for the plot of AAD size by MSCT versus 2-dimensional echocardiography was 0.78 (p ⬍0.0001). Eight of 214 patients (4%) had AADs measured by MSCT of ⱖ4.5 cm. Of these 8 patients, the AADs measured by 2-dimensional echocardiography were ⱖ4.5 cm in 2 patients (25%), 4.0 to 4.4 cm in 2 patients (25%), and ⬍3.7 cm in 4 patients (50%). Four of 214 patients (2%) had AADs measured by 2-dimensional echocardiography of ⱖ4.5 cm. The AADs measured by MSCT in these 4 patients were 5.0, 4.7, 4.4, and 3.9 cm.
121
The use of transthoracic echocardiography for the evaluation of AAD offers the advantages of wide accessibility to large numbers of patients, relatively low cost, and the lack of need for intravenous contrast and exposure to ionizing radiation. Our data indicate that AAD measured by echocardiography correlates well with that measured by MSCT, although important limitations are present. Although specificity and negative predictive value for an enlarged AAD were each ⬎90%, the detected sensitivity and positive predictive value were not as satisfactory. Furthermore, among the small number of patients with AADs ⱖ4.5 cm, echocardiography detected this degree of enlargement in only 25% of patients and detected normal AADs in 50% of these patients. Sources of disparity between echocardiographic and multislice computed tomographic measurements likely5 include imaging artifacts with ultrasound and the inability in many cases to image the ascending aorta above its most proximal segment with echocardiography. The overestimation of MSCT may also occur when axial images are used and an oblique measurement of AAD is made in a vessel that is not perpendicular to the axial plane. Tamborini et al5 found that transthoracic echocardiography is a feasible and accurate technique for the assessment and follow-up of thoracic aorta diameters in patients with known ascending aortic aneurysms. The identification of AAD enlargement by echocardiography is a clinically useful finding and may warrant further imaging. A lack of AAD enlargement by echocardiography does not exclude such enlargement, and in selected patients, further imaging studies may still be required.
Discussion To the best of our knowledge, the prevalence of an enlarged AAD diagnosed by 2-dimensional echocardiography has not been compared with that of an enlarged AAD diagnosed by MSCT. The present study showed that enlarged AADs were present in 20% of our 214 patients by 2-dimensional echocardiography and in 21% of our patients by MSCT (p ⫽ NS). The Bland-Altman plot showed that the agreement for AAD measured by 2-dimensional echocardiography was 95% within the 2-SD limits. Pearson’s correlation coefficient for the plot of AAD size by MSCT versus 2-dimensional echocardiography was 0.78 (p ⬍0.0001). Our study also showed that the sensitivity, specificity, positive predictive value, and negative predictive value of 2-dimensional echocardiography were 69%, 93%, 74%, and 92%, respectively, in diagnosing an enlarged AAD using MSCT.
1. Feigenbaum H, Armstrong W, Ryan T. Feigenbaum’s Echocardiography. 6th ed. Philadelphia, Pennsylvania: Lea & Febiger, 2005:673. 2. Raff GL, Gallagher JM, O’Neill W. Diagnostic accuracy of noninvasive coronary angiography using 64-slice spiral computed tomography. J Am Coll Cardiol 2005;46:552–557. 3. Leber AW, Becker A, Knez A, von Ziegler F, Sirol M, Nikolaou K, Ohnesorge B, Fayad ZA, Becker CR, Reiser M, et al. Accuracy of 64-slice computed tomography to classify and quantify plaque volumes in the proximal coronary system: a comparative study using intravascular ultrasound. J Am Coll Cardiol 2006;47:672– 677. 4. Hager A, Kaemmerer H, Rapp-Bernhardt U, Blucher S, Rapp K, Bernhardt TM, Galanski M, Hess J. Diameters of the thoracic aorta throughout life as measured with helical computed tomography. J Thorac Cardiovasc Surg 2002;123:1060 –1066. 5. Tamborini G, Galli CA, Maltagliati A, Andreini D, Pontone G, Quaglia C, Ballerini G, Pepi M. Comparison of feasibility and accuracy of transthoracic echocardiography versus computed tomography in patients with known ascending aortic aneurysm. Am J Cardiol 2006;98: 966 –969.