(Radiographics. 2002;22:1137-1138.)
© RSNA, 2002
Invited Commentary • Author's Response
John P. McGahan, MD
Department of Radiology, University of California, Davis, Medical Center, Sacramento, California
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Commentary
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Congenital heart defects are often some of the most complex and challenging anomalies to diagnose prenatally. The difficulty in diagnosis is due to several factors. First, a comprehensive examination of the fetal heart usually cannot be performed until after 18 weeks. Second, no single view will suffice as an ideal screening modality for all congenital heart disease. Finally, even if a complete fetal cardiac examination is performed, certain abnormalities will fail to be diagnosed with US.
However, there is some good news. If a well-detailed four-chamber view of the heart is obtained, as outlined by Barboza and colleagues in the preceding article, then approximately 48%–69% of cardiac malformations will be detected with US. The defects that are detected are often the more severe defects such as univentricular lesions, such as hypoplastic left heart syndrome and atrial or ventricular defects, as outlined in their review (1–3). However, conotruncal abnormalities will not be diagnosed with a four-chamber view of the heart. These abnormalities may be ductus dependent, such as transposition of the great vessels, and are therefore important to diagnose before birth. They also are more amenable to corrective surgery than univentricular abnormalities.
Therefore, visualization of the great vessels is important. In most series, if views of the great vessels are included in examination of the fetal heart, then prenatal diagnosis of cardiac malformations increases to approximately 80% (1,2). Traditionally, visualization of the great vessels has included a long-axis view of the heart. More recently other methods, including a base view of the great vessels, have been used. This view is both easy to obtain and reliable in diagnosis of conotruncal abnormalities (4,5).
Two final points: Even with a more comprehensive fetal echocardiographic examination, we will not detect all cardiac malformations. This is especially true of some small atrial septal defects, small VSDs, minor valve abnormalities, anomalous pulmonary venous return, and coarctation of the aorta (1,2). Furthermore, experience is important! Like anything we do, with the exception of golf, repetition will improve our game. Isaksen et al (6) evaluated their success in prenatal diagnosis of congenital heart disease in two different periods. One period was from 1985 to 1989, and the second period was from 1990 to 1994. With their greater experience and technical advances in US, they increased their detection rate for all cardiac defects from 48% to 82% (6). While practice doesn't make perfect, it certainly helps.
In summary, the review by Barboza and colleagues presents a nice basic approach to examination of the fetal heart by incorporation of the base view of the great vessels with the four-chamber view. This approach or other similar approaches in examination of the fetal heart, if carefully performed, will improve diagnosis of fetal congenital heart disease.
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References
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- Achiron R, Glaser J, Gelernter I, Hegesh J, Yagek S. Extended fetal echocardiographic examination for detecting cardiac malformations in low risk pregnancies. BMJ 1992; 304:671-674.
- Bromley B, Estroff JA, Sanders SP, et al. Fetal echocardiography: accuracy and limitations in a population at high and low risk for heart defects. Am J Obstet Gynecol 1992; 166:1473-1481.[Medline]
- Sharland GK, Allan LD. Screening for congenital heart disease prenatally: results of a 2 1/2-year study in the South East Thames Region. Br J Obstet Gynaecol 1992; 99:220-225.[Medline]
- Yoo SJ, Lee YH, Kim ES, et al. 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; 9:173-182.[CrossRef][Medline]
- 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; 17:367-369.[CrossRef][Medline]
- Isaksen CV, Eik-Nes SH, Blaas HG, Tegnander E, Torp SH. Comparison of the prenatal ultrasound and postmortem findings in fetuses and infants with congenital heart defects. Ultrasound Obstet Gynecol 1999; 13:117-126.[CrossRef][Medline]
Author's Response
Jodi M. Barboza, MD
Department of Radiology, University of Arkansas for Medical Sciences, Little Rock, Arkansas
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Response
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We would like to thank Dr McGahan for his comments. As a resident in training, I have realized that there is a steep learning curve in all areas of radiology. However, US is one of the most challenging modalities to learn, as it requires a great deal of technical ability and hands-on experience. Experience and technical expertise are especially required in the area of prenatal fetal US, and the only way to gain this expertise is to practice scanning. Even though practice doesn't make perfect, it sure helps to decrease the anxiety experienced while looking at an abnormal fetal heart.
Related Article
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Prenatal Diagnosis of Congenital Cardiac Anomalies: A Practical Approach Using Two Basic Views
- Jodi M. Barboza, Nafisa K. Dajani, Lana G. Glenn, and Teresita L. Angtuaco
RadioGraphics 2002 22: 1125-1138.
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