The three vessels and trachea view (3VT) in fetal cardiac

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1 Ultrasound Obstet Gynecol 2002; 20: The three vessels and trachea view (3VT) in fetal cardiac Blackwell Science, Ltd scanning S. YAGEL*, R. ARBEL, E. Y. ANTEBY*, D. RAVEH and R. ACHIRON *Department of Obstetrics and Gynecology, Hadassah University Hospital, Mt. Scopus, Jerusalem, Israel, Department of Obstetrics and Gynecology, Hadassah University Hospital, Ein Kerem, Jerusalem, Israel, Department of Infectious Diseases, Shaare Zedek Medical Center, Jerusalem, Israel, and Department of Obstetrics and Gynecology, Chaim Sheba Medical Center, Tel Hashomer, Israel KEYWORDS: Fetal echocardiography, Great vessels, Prenatal diagnosis, Ultrasound ABSTRACT Objective Comprehensive evaluation of the fetal heart has become a major part of targeted organ scanning to rule out fetal malformations. Evaluation of the mediastinal major vessels seems to be the most difficult and time-consuming part of fetal heart examination. Our aim was to define and evaluate the three vessels and trachea (3VT) view, a novel and simple method to examine the great vessels in the mediastinum, and its applicability in the clinical practice of fetal echocardiography, while establishing nomograms for cardiac vessel measurements obtained in this view. Methods The three vessels and trachea view was examined in 379 low-risk gravidae between 14+0 and 23+6 weeks gestation. Six parameters in this plane were measured to establish nomograms. In another group of 984 mixed highand low-risk patients we compared the time required to identify the aortic arch using the 3VT view as compared to the long-axis view. Results The 3VT view was readily and satisfactorily demonstrated in all but two of the 1363 cases examined. In 17 cases (out of a total of 982) more than 10 min were required to identify the aortic arch using the 3VT view and in 71 patients when employing the long-axis view (P < 0.001). Conclusion The clinical applicability of the 3VT view to evaluate the anatomy of the major vessels in the mediastinum is demonstrated. Although a wide variation in the six parameters of the 3VT view used here precludes their use in diagnosing great vessel anomalies, some of the ratios between them have promising potential in the evaluation of great vessel malformations. Further, the 3VT view seems to be more efficient in identifying the aortic arch than does the long-axis view. INTRODUCTION The considerable progress made in the last decade in fetal ultrasound, coupled with the concomitant demand of the public for the most thorough prenatal screening possible, and the relatively high incidence of congenital heart defects, have contributed to increased demands on sonographers to identify most fetal cardiac lesions. This means that extended fetal heart examination should be applied to patients presenting for targeted organ scanning 1 5. In the past, fetal echocardiography was considered to be the domain of highly experienced specialists in ultrasound, because it was thought to be the most complex of prenatal ultrasound scans, and to demand lengthy examination time and specialized training. The challenge today is to develop a simplified method whereby these two seemingly contradictory demands can be addressed, and fetal echocardiography can be made exact and thorough, and accessible to the majority of examiners. To this end, Yoo et al. suggested the three-vessel view of the fetal upper mediastinum, which is a cross-sectional view of the major vessels 6,7. His approach significantly improved the examiner s ability to identify the great vessels quickly and accurately, and thereby to diagnose certain anomalies, but the aortic arch and trachea were not included in their methodology, the most difficult and time-consuming part of fetal heart examination. A method to overcome this difficulty was recently proposed 8. The aim of the present study was twofold: first, to define a comprehensive examination method of the great vessels in the fetal mediastinum; second, to establish nomograms of the great vessels and the trachea, that may be beneficial in the precise diagnosis of some great-vessel pathologies. The novelty of our method lies in its capacity to image the main pulmonary arteries, the ductus arteriosus, the upper part of the aortic arch, the superior vena cava, and the trachea. We propose adding this three vessel and trachea (3VT) view to Correspondence: Prof Simcha Yagel, Department of Obstetrics and Gynecology, Hadassah University Hospital Mt. Scopus, PO Box 24035, Jerusalem, Israel ( syagel@hadassah.org.il) Accepted ORIGINAL PAPER

2 the classic four-chamber view (FCV) and extended cardiac evaluation, to achieve an accessible, effective, and fast method of thoroughly and accurately scanning the fetal heart. METHODS a cross section of the trachea (Figures 2a and b). This view differs from the three-vessel view suggested by Yoo et al. 6,7, in which the aortic arch and trachea were not included. Fetal heart examinations were performed transabdominally or transvaginally as appropriate. The 3VT view The 3VT view was added to the classic or standard fetal echocardiography views. Color Doppler examination of the atrioventricular valves, the great vessel valves, and the foramen ovale was routinely performed. Pulse Doppler and M-mode echocardiography were performed wherever indicated. The 3VT view is one of seven ultrasonographic examination views or planes of the fetal heart. The first and most caudal is the transverse view of the upper abdomen. The second is the FCV; the third is the five-chamber view, in which the aortic valve is demonstrated. In the fourth, transverse view one can detect the bifurcation of the pulmonary arteries. Long-axis planes are obtained to visualize the right and left outflow tracts and aortic arch. The 3VT view is the most cephalad transverse view, located in the fetal upper mediastinum (Figures 1a and b). The 3VT view is easily obtained once the FCV is adequately visualized, by moving the transducer cephalad and slightly obliquely from the FCV plane (Figure 1c). All these transverse views are demonstrated by sliding the transducer from the upper abdomen to the upper mediastinum. A satisfactory 3VT view was defined as that which demonstrated the main pulmonary trunk in direct communication with the ductus arteriosus (DA) and, to the right of the MPA and DA, a transverse section of the aortic arch. A cross section of the superior vena cava was visualized, and posterior to it Figure 1 The three vessels and trachea view (3VT) plane of insonation in schematic representation (for illustration only). (a) The anatomical plane at which the 3VT is visualized, relative to the four-chamber view (FCV) plane. (b) Schematic representation of the 3VT cross section. (c) The FCV cross section. AO, aorta; DA, ductus arteriosus; PA, pulmonary artery; SVC, superior vena cava; T, trachea. Figure 2 The three vessels and trachea (3VT) view gray-scale image (a) and gray-scale image with color Doppler mapping (b). (c) Measurements taken in the 3VT plane of insonation. P, main pulmonary artery; (P)Ao, proximal aorta; (D)Ao, distal aorta; SVC, superior vena cava; DA, ductus arteriosus; T, trachea. Ultrasound in Obstetrics and Gynecology 341

3 Nomograms of the 3VT view We measured the pulmonary artery, ductus arteriosus, proximal and distal aortic arches, the anterior posterior diameter of the superior vena cava, and the anteri or posterior diameter of the trachea. The measurement of the pulmonary artery was at the widest diameter of the origin of the main pulmonary artery. The same approach was taken to measure the proximal part of the aortic arch of the 3VT view. To measure the ductus arteriosus and the distal part of the aortic arch, these vessels were divided into three segments and the vessel width was measured exactly between the second and third parts of the vessel under examination (Figure 2c). We decided to use this approach, as no constant, reliable and reproducible landmark could be identified in the distal parts of the ductus arteriosus or the aortic arch. All measurements cited were taken using the on on technique. The relationship between the vessels sizes and gestational age, femur length (FL) and biparietal diameter (BPD) were determined, as well as the ratios between some of the vessels measurements. The study was cross-sectional with only one set of measurements taken for each patient. The biometric parameters obtained included the BPD, head circumference (HC), FL, and abdominal circumference (AC). Cases with suspected fetal malformations were excluded from this study. In all cases gestational age was confirmed by early first-trimester ultrasonography. Identification of the aortic arch One of the most time consuming tasks of fetal echocardiography is the identification of the full length and function of the aortic arch. This problem is emphasized in busy clinical programs in which fetal echocardiography is an integral part of targeted organ screening. As one of the major advantages of the 3VT view is in the identification of the aortic arch, in 984 mixed low- and high-risk patients we compared the time required to identify the aortic arch using the long-axis view vs. 3VT view. The time was measured after obtaining the FCV, and included the gray-scale and color Doppler examination. parameters is shown in Table 2. Similar results were obtained for FL regression vs. 3VT parameters (data not shown). The wide variation apparent in all six measurements included in the 3VT method during the course of gestation precludes their use in diagnosing great-vessel anomalies. Therefore, we analysed the regression between pregnancy age and some of the ratios between our six proposed 3VT measurements (Table 3). Four ratios are described in Figure 4. We believe that these ratios may be particularly useful in diagnosing great-vessel anomalies, as will be discussed below. Follow-up of study subjects revealed only two neonates diagnosed postnatally with small ventricular septal defects (VSDs). Identification of the aortic arch Encouraged by our success in obtaining the 3VT view in a large group of patients, we further investigated the advantage of applying the 3VT method in identifying the aortic arch. Nine hundred and eighty four women with singleton pregnancies comprised the study group of this stage of the study. Mean maternal age was 31.7 years (range 19 47); mean parity was 2.8 (0 9); and mean gestational age 18+7 (14+0 to 24+6 weeks). In 982 patients the 3VT was clearly visualized, while in the other two cases maternal obesity impaired our ability to image this plane. We compared the time required to identify the aortic arch using the 3VT vs. the long-axis view. Results revealed that in 17 cases (1.73%) more than 10 min were required to visualize the aortic arch using 3VT method. Statistical methods For statistical processing we used the EpiInfo 6.04c program (CDC, USA), employing the chi square test, t-test and linear regression. Graphs were plotted with Sigma Plot 2.0 (Jandel, USA). RESULTS Nomograms Three hundred and seventy-nine women with singleton gestations comprised our study group, to establish nomograms of the 3VT view 9,10. The mean maternal age was 30.9 years (range 21 45, SD ± 4.6). The mean parity was 2.9 (range 0 9). Gestational age at time of the scans was between 14+0 and 23+6 weeks. In all cases a satisfactory 3VT view was visualized. The six 3VT view parameters are shown in Figure 3 and in Table 1. Regression of pregnancy age vs. the six 3VT view Figure 3 Six three vessels and trachea view parameters as functions of pregnancy age, with 5% and 95% confidence intervals. 342 Ultrasound in Obstetrics and Gynecology

4 Table 1 Mean and 95% confidence intervals (CI) for six 3VT parameters at weeks gestation Mean dimensions (mm) Pulmonary artery Ductus arteriosus Proximal aortic arch Distal aortic arch Superior vena cava Trachea Week n Mean (95% CI) n Mean (95% CI) n Mean (95% CI) n Mean (95% CI) n Mean (95% CI) n Mean (95% CI) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) Table 2 Regression of pregnancy age vs. six 3VT view ultrasonic parameters r 2 -value Slope Intercept Distal aortic arch Ductus arteriosus Trachea Proximal aortic arch Superior vena cava Pulmonary artery Data are arranged by increasing r 2 -values. However, employing the long-axis view, in 71 patients (7.23%) more than 10 min were required to visualize the aortic arch (P < 0.001). In 37 patients (3.77%) more than 20 min were required to image the aortic arch with this method, as compared to only two such cases (0.2%) using the 3VT view (Table 4, P < 0.001). In this group of 984 patients, six cases of fetal cardiac anomaly were diagnosed: Figure 4 Regression analysis between pregnancy age and four ratios of three vessels and trachea view parameters, with 5% and 95% confidence intervals. Table 3 Regression between pregnancy age and some ratios of the six 3VT view parameters r 2 -value Slope Intercept Ductus/proximal + distal aortic arch Tachea/distal aorta Trachea/ductus Ductus/proximal aortic arch Trachea/proximal aorta (Pulmonary + ductus)/(proximal aortic arch) Superior vena cava/ductus Proximal aortic arch/distal aortic arch Superior vena cava/proximal aorta (Pulmonary + ductus)/(proximal + distal aortic arch) Superior vena cava/distal aorta Trachea/pulmonary Trachea/superior vena cava Pulmonary/ductus Pulmonary/proximal aortic arch Pulmonary/(proximal + distal aortic arch) Superior vena cava/pulmonary Data are arranged in increasing order of r 2 -values. Ultrasound in Obstetrics and Gynecology 343

5 Table 4 Times taken for aortic arch identification with the 3VT view and long-axis methods Time taken (min) Number (and percentage) of the 982 patients 3VT method Long-axis method < (98.065%) 874 (89.002%) (1.731%) 71 (7.230%)* > 20 2 (0.204%) 37 (3.768%)* *P < Figure 5 Three vessels and trachea view of left superior vena cava anomaly. P, main pulmonary artery; AO, aorta; (L)SVC, left superior vena cava; DA, ductus arteriosus; T, trachea. Figure 6 Three vessels and trachea view of right aortic arch anomaly. PA, main pulmonary artery; AO, aorta; SVC, superior vena cava; the arrow points to the trachea. hypoplastic left heart (n = 1); pulmonary atresia (with VSD and d-transposition) (n = 1); complete atrioventricular canal (n = 1); transposition of the great arteries (n = 1); persistent left superior vena cava (n = 1, Figure 5); and right aortic arch without vascular ring (n = 1, Figure 6). Prenatally diagnosed anomalies were confirmed after birth; follow-up of pregnancy outcome in this group revealed another two cases of cardiac anomaly diagnosed postnatally: one VSD and one moderate pulmonary stenosis. DISCUSSION This study demonstrates the clinical applicability of a novel approach to fetal heart scanning to evaluate the anatomy of the major vessels in the mediastinum. In a cross-sectional study, the main pulmonary artery, ductus arteriosus, distal part of the aortic arch, superior vena cava and trachea were clearly and easily visualized in 99% of 1363 patients. This view facilitated the examination of this complicated part of the fetal heart, once the familiar FCV was obtained, as described above. The primary advantage of this methodology was demonstrated by shorter time required to visualize the aortic arch in comparison with the traditional long-axis view. In our methodology, the identification of the trachea is stressed because it is an indispensable structure in the 3VT plane. Its importance in the detection of intramediastinal anomalies stems from its constancy as a reference point: anomalous vessels or organs can be identified and described by their size or location (or both) relative to those of the trachea. This confirms our belief that the 3VT view is superior to the classical methods of evaluation of the major cardiac vessels in the mediastinum. Moreover, in this series we diagnosed one case of right aortic arch with left descending aorta and another of persistent left superior vena cava. From our observations, it seems that anomalies such as right aortic arch without postnatal sequelae, are more readily identified using the 3VT view, and may not be as rare as traditionally believed. Although it is impossible to draw any conclusion from this small number of cases, we believe that the 3VT view is of special benefit in diagnosing certain major vessel anomalies; this is described in the companion study to this one 11. We established nomograms of the six parameters scanned at the level of the 3VT. The wide variation in size of the main pulmonary arteries, aorta, ductus arterious, superior vena cava and trachea made these nomograms inefficient in diagnosing major vessel anomalies, such as pulmonic or aortic stenosis, or aortic coarctation. However, some of the ratios between these structures diameters are relatively constant during pregnancy, with narrow confidence limits. These nomograms are applicable to the 3VT view, and not intended to replace the nomograms extant in the literature for maximum vessel diameter. Despite the nomograms wide variance, when the 3VT view is properly obtained, according to the landmarks described, it can deviate by, at most, 2 3. We believe that the wide variance in measurements among fetuses is attributable to anatomical variation, not low reproducibility in the measurements themselves. Ratios between measurements of individual fetuses have a much narrower variance. As the ratios express the relative sizes of the vessels to each other, they may better demonstrate an anomaly than crude measurements of a single vessel. For example, the ratio between the pulmonary artery and the proximal + distal aorta, or that between the ductus arteriosus and the proximal + distal aorta, are fixed during pregnancy, with very narrow confidence limits. Therefore, these ratios may prove to be of great potential in diagnosing some cases of pulmonary stenosis, coarctation of the aorta, and others. Further study is required to test these nomograms on large populations of normal and anomalous fetal hearts. The applicability of this method in the diagnosis 344 Ultrasound in Obstetrics and Gynecology

6 of anomalies of the aortic arch is explored more extensively elsewhere 11. Additionally, as many of these pathologies evolve in the course of pregnancy 12 15, these ratios may serve in the follow-up of suspected cases. As stated above, we set out to find a better way to evaluate the anatomy of the great vessels in the mediastinum. We do not expect that this new methodology will significantly improve the accuracy of diagnosis of fetal heart anomalies, which is today reasonably high 1 5,12, However, in our center it appeared that the 3VT method simplified and streamlined our fetal echocardiographic examination, without compromising its diagnostic potential. The 3VT view includes the trachea and the superior vena cava. The relation of these structures to the great vessels may be beneficial in diagnosing major vessel pathologies that involve malposition of the vessels. This aspect of the 3VT was described by Yoo et al. using a similar plane of insonation 6,7. A matter for further investigation is the place of the 3VT methodology in the evaluation of the aortic arch and its associated anomalies. In summary, we showed that the 3VT view is a simple, reliable approach to the examination of major vessels in the fetal mediastinum. The use of this view is another step in the integration of thorough fetal heart examination in routine targeted organ screening. REFERENCES 1 Achiron R, Glaser J, Gelernter I, Hegesh J, Yagel S. Extended fetal echocardiographic examination for detecting cardiac malformations in low risk pregnancies. Br Med J 1992; 304: Gembruch U. Prenatal diagnosis of congenital heart disease. Prenat Diagn 1997; 17: Stumpflen I, Stumpflen A, Wimmer M, Bernaschek G. Effect of detailed fetal echocardiography as part of prenatal ultrasonographic screening on detection of congenital heart disease. Lancet 1996; 348: Ott WJ. The accuracy of antenatal fetal echocardiography screening in high- and low-risk patients. Am J Obstet Gynecol 1995; 172: Wyllie J, Wren C, Hunter S. Screening for fetal cardiac malformations. Br Heart J 1994; 71 (Suppl.): Yoo SJ, Lee YH, Kim ES, Ryu HM, Kim MY, Choi HK, Cho KS, Kim A. Three-vessel view of the fetal upper mediastinum: an easy means of detecting abnormalities of the ventricular outflow tracts and great arteries during obstetric screening. Ultrasound Obstet Gynecol 1997; 9: Yoo SJ, Young HL, Kyoung SC. Abnormal three-vessel view on sonography: a clue to the diagnosis of congenital heart disease in the fetus. AJR Am J Roentgenol 1999; 172: Yagel S, Cohen SM, Achiron R. Examination of the fetal heart by five short-axis views: a proposed screening method for comprehensive cardiac evaluation. Ultrasound Obstet Gynecol 2001; 17: Royston P, Wright EM. How to construct normal ranges for fetal variables. Ultrasound Obstet Gynecol 1998; 11: Royston R, Altman DG. Design and analysis of longitudinal studies of fetal size. Ultrasound Obstet Gynecol 1995; 6: Achiron R, Rotstein Z, Hegesh J, Bronshtein M, Zimand S, Lipitz S, Yagel S. Anomalies of the fetal aortic arch: a novel ultrasonographic approach to in-utero diagnosis. Ultrasound Obstet Gynecol 2002; in press. 12 Yagel S, Weissman A, Rotstein Z, Manor M, Hegesh J, Anteby E, Lipitz S, Achiron R. Congenital heart defects: natural course and in utero development. Circulation 1997; 96: Hornberger LK, Sanders SP, Rein AJ, Spevak PJ, Parness IA, Colan SD. Left heart obstructive lesions and left ventricular growth in the midtrimester fetus. A longitudinal study. Circulation 1995; 92: Hornberger LK, Sanders SP, Sahn DJ, Rice MJ, Spevak PJ, Benacerraf BR, McDonald RW, Colan SD. In utero pulmonary artery and aortic arch growth and potential for progression of pulmonary outflow tract obstruction in tetralogy of Fallot. J Am Coll Cardiol 1995; 25: Brown DL, Durfee SM, Hornberger LK. Ventricular discrepancy as a sonographic sign of coarctation of the fetal aorta: how reliable is it? J Ultrasound Med 1997; 16: Tometzki AJ, Suda K, Kohl T, Kovalchin JP, Silverman NH. Accuracy of prenatal echocardiographic diagnosis and prognosis of fetuses with conotruncal anomalies. J Am Coll Cardiol 1999; 33: Hafner E, Scholler J, Schuchter K, Sterniste W, Philipp K. Detection of fetal congenital heart disease in a low-risk population. Prenat Diagn 1998; 18: Tegnander E, Eik-Nes SH, Johansen OJ, Linker DT. Prenatal detection of heart defects at the routine fetal examination at 18 weeks in a non-selected population. Ultrasound Obstet Gynecol 1995; 5: Rustico MA, Benettoni A, D Ottavio G, Maieron A, Fischer-Tamaro I, Conoscenti G, Meir Y, Montesano M, Cattaneo A, Mandruzzato G. Fetal heart screening in low-risk pregnancies. Ultrasound Obstet Gynecol 1995; 6: Ultrasound in Obstetrics and Gynecology 345