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Obstetrics & Gynecology 1999;93:189-192
© 1999 by The American College of Obstetricians and Gynecologists
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ORIGINAL RESEARCH

Fetal Cardiac Asymmetry: A Marker for Congenital Heart Disease

JANET S. KIRK, MD, CHRISTINE H. COMSTOCK, MD, WESLEY LEE, MD, RAMADA S. SMITH, MD, THOMAS W. RIGGS, MD and ELLIOTT WEINHOUSE, MD

From the Division of Fetal Imaging, Department of Obstetrics and Gynecology, and Division of Pediatric Cardiology, Department of Pediatrics, William Beaumont Hospital, Royal Oak, Michigan.

Address reprint requests to: Janet S. Kirk, MD Department of Fetal Imaging Department of Obstetrics and Gynecology William Beaumont Hospital 3601 West Thirteen Mile Road Royal Oak, MI 48073


   Abstract
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Abstract
Materials and Methods
 Results
 Discussion
 References
 
Objective: To determine the sensitivity of prenatally detected fetal cardiac asymmetry as a sonographic marker for congenital heart disease.

Methods: The normal ratios of pulmonary artery to aorta diameters and of right ventricle to left ventricle diameters were derived from normal fetuses scanned at 17 weeks or more in a 65-month period. Cross-sectional diameters of cardiac ventricles and great arteries were measured at the level of the valves at the time of the scan. Fetuses with confirmed cardiac anomalies detected prenatally during the study were examined to identify how many had cardiac asymmetry, determined by abnormal ratios.

Results: Linear regression analysis of the group of 881 normal fetuses showed the normal pulmonary artery to aorta diameter ratio remained constant throughout pregnancy and the normal right ventricle to left ventricle ratio increased slightly with progressing gestational age. The 90% confidence intervals were 0.79, 1.24 for the right ventricle to left ventricle ratio and 0.84, 1.41 for the pulmonary artery to aorta ratio. Of the 73 fetuses with abnormal hearts, 66% had either ventricular or great artery asymmetry (at least one of the two ratios was abnormal). However, if no asymmetry was present, the cardiac defect was more likely to be a minor one.

Conclusion: Cardiac asymmetry was present in two-thirds of fetuses with cardiac anomalies diagnosed prenatally. If cardiac asymmetry is found, a more thorough examination of the fetal heart is indicated.

Prenatal detection of cardiac defects is difficult and often requires extensive experience. Various elements of cardiac examination have been evaluated for their value in detecting cardiac abnormalities. Studies suggest that a four-chamber view of the fetal heart detects between 5% and 81% of cardiac defects.1–12 A four-chamber view with outflow tracts or an echocardiogram can detect 14–83% of defects.13 An abnormal left cardiac axis has been found in 44–75% of abnormal cardiac cases.14,15 In our ultrasound unit, we noticed that many fetuses with cardiac defects had asymmetry between the right and left sides of their heart. In our previous report,16 the pulmonary artery to aortic root diameter ratio was evaluated in 316 normal fetuses and in 21 fetuses with cardiac defects. The current study extends our evaluation of the ratios of the great arteries to a larger number of cases and examines ventricular asymmetry. Our objective was to evaluate fetal cardiac asymmetry of the ventricles, the great arteries, or either as a marker for congenital heart disease.


   Materials and Methods
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Abstract
 Materials and Methods
Results
 Discussion
 References
 
We reviewed the ultrasound records of consecutive unselected singleton pregnancies scanned in our unit at 17 weeks or more, between February 1990 and July 1995, to identify all fetuses with cardiac measurements at the time of the scan. Only those delivered at our hospital were included. Fetuses with abnormal karyotypes or anomalies other than a single umbilical artery or choroid plexus cysts were excluded from the normal group. Fetuses correctly diagnosed prenatally during the study period with cardiac defects were identified. Neonatal echocardiograms and autopsies performed at William Beaumont Hospital were reviewed to confirm that the fetuses with suspected cardiac abnormalities were identified correctly as abnormal.

Ventricles were measured from the inner edge of the myocardial wall to the inner edge of the septal wall, at the level of the mitral and tricuspid valves, during diastole (Figure 1Go). The great arteries were measured at the level of the aortic and pulmonic valves (Figure 2Go), between the inner edges of the vessel walls. Cases with abnormal ratios are shown in Figures 3Go and 4Go. M-mode was not used to obtain measurements because no difference has been noted between M-mode and cross-sectional fetal cardiac measurements.17,18 Equipment consisted of the Acuson 128 XP/10, Acuson 128 (Acuson Corporation, Mountain View, CA), Aloka 650 (Corometrics Ultrasound Medical Systems, Wallingford, CT), and Philips Platinum (Philips Medical Systems, Santa Ana, CA). Three fetuses with cardiac defects had one or two fetal cardiac measurements that were not recorded in the report. These measurements were obtained from videotapes of the scans.



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  		Figure 1. Ventricular diameters at the level of mitral and tricuspid valves.

 


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  		Figure 2. Great artery diameters at the level of aortic and pulmonic valves. AO = aortic root; PA = pulmonary artery.

 


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  		Figure 3. Ventricular asymmetry with the right ventricle (KV) (arrows) larger than the left ventricle (LV). The right ventricle to left ventricle ratio is 1.56.

 


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  		Figure 4. Great artery asymmetry with a large aortic root (AO) and small pulmonary artery (PA) (arrows). The pulmonary artery to aortic root ratio is 0.45.

 
Ratios of the diameter of the right ventricle to left ventricle and of the pulmonary artery to aorta were calculated in normal fetuses and in fetuses with cardiac defects. Linear regression analysis was used to determine the relationship between gestational age and each of the ratios in the normal group.


   Results
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Abstract
 Materials and Methods
 Results
Discussion
 References
 
During the study period, 14,141 singleton fetuses were scanned in our unit, at 17 weeks or more, who delivered at our large suburban teaching hospital. After excluding fetuses with anomalies (other than a single umbilical artery or choroid plexus cysts) or abnormal karyotypes, there were 881 fetuses with cardiac measurements at the time of the scans. Almost all of them had fetal echocardiography for standard indications, such as family history or teratogen exposure. Also included were ten fetuses in whom there was a question on qualitative evaluation during a screening examination. During the study period, 93% of mothers who delivered at our hospital were white, and the mean maternal age at delivery was 29.5 years.

In the normal fetuses, the right ventricle to left ventricle ratio increased slightly with gestational age. The pulmonary artery to aorta ratio remained constant throughout pregnancy. The 90% confidence intervals (CI) were 0.79, 1.24 for right ventricle to left ventricle ratio and 0.84, 1.41 for pulmonary artery to aorta ratio. The confidence limits of the ratio of the great arteries are similar to those found in our smaller study of 1991.16

There were 73 fetuses correctly diagnosed prenatally with cardiac defects during the study period. The most common cardiac lesions detected were atrioventricular septal defects, tetralogy of Fallot, and isolated ventricular septal defects. Figure 5Go shows the right ventricle to left ventricle ratios of fetuses with cardiac defects, with the mean and 90% CI cutoffs from the normal group indicated. In Figure 6Go, the pulmonary artery to aorta ratios of the fetuses with cardiac defects are shown with means and 90% CIs. Note that some fetuses had more than one scan.



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  		Figure 5. Ratios of the right to left ventricular diameters (RV/LV) in fetuses with cardiac defects throughout pregnancy.

 


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  		Figure 6. Ratios of the pulmonary artery to aortic root diameters (PA/AO) in fetuses with cardiac defects throughout pregnancy.

 
If ventricular asymmetry alone was used to identify fetuses with cardiac defects, then 32 (44%) of 73 would have been identified. If great artery asymmetry alone was used, 35 (48%) of 73 would have been identified. If either ventricular or great artery asymmetry was present, then 48 (66%) of 73 fetuses with cardiac defects would have been identified. The 5% and 95% CI range is 55% to 77%.

Location of asymmetry involving ventricles or great arteries was analyzed. One third of fetuses with cardiac defects had no asymmetry. Of those with asymmetry, 13 had asymmetry of the ventricles only, 16 had asymmetry of the great arteries only, and 19 had asymmetry of both the ventricles and great arteries. Table 1Go shows predominant lesions by location (ventricles or great arteries). Of the fetuses with no asymmetry, the predominant lesion was either an isolated ventricular septal defect or atrioventricular septal defect. In fetuses with ventricular asymmetry only, atrioventricular septal defect was the most frequent lesion. In fetuses with asymmetry of the great arteries only, tetralogy of Fallot was the most common lesion. When both ventricles and great arteries were asymmetric, the predominant lesion was a hypoplastic left or right heart. If there was any asymmetry (ie, if either ratio was abnormal), the most common lesions were those involving the great arteries, such as tetralogy of Fallot, aortic coarctation, or transposition of the great arteries. Therefore, when there was no asymmetry, the lesion was more likely to be minor, such as an isolated ventricular septal defect. When there was any asymmetry, the lesions often involved great arteries.


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  		Table 1. Location of Asymmetry and the Predominant Lesion in Fetuses With Congenital Heart Disease
 
Some subjects were common to our previous16 and current studies. In the current study, there were six fetuses in the group with congenital heart disease and 196 fetuses in the normal group who were included in the previous study. The current study includes only fetuses delivered at our hospital and does not exclude those with growth retardation.


   Discussion
Top
Abstract
 Materials and Methods
 Results
 Discussion
References
 
Our results suggest that congenital heart disease can be suspected if fetal cardiac asymmetry is present. Two thirds of the fetuses with structural cardiac defects had at least one abnormal ratio, and the normal values were relatively constant throughout pregnancy. As reported in previous studies, there was little change in the pulmonary artery to aorta ratio throughout pregnancy,16,17 and there is a slight increase in the right ventricle to left ventricle ratio as gestational age increases.17,19

Other investigators considered the clinical use of ventricular asymmetry. In 1989, Benacerraf et al20 reported nine fetuses with abnormal right ventricle to left ventricle ratios. Four had aortic coarctation with ratios of 1.5–2.2 (all abnormal ratios by our criteria). One of nine had a small left ventricle and a parachute mitral valve, and one had a patent ductus arteriosus. The remaining three had normal cardiac evaluations. Not every fetus with an abnormal right ventricle to left ventricle ratio will have structural cardiac defects; the right ventricle to left ventricle ratio can be abnormally high in fetuses with growth retardation.19 Yet, growth-restricted fetuses were found to have no significant differences from normal fetuses in diameters of the great vessels.18

In most fetuses, determination of fetal cardiac asymmetry can be done qualitatively and does not require all the criteria inherent in a four-chamber view and views of the outflow tracts. Cardiac asymmetry can be determined easily by visualizing the diameters of the ventricles or the great arteries. We found that a qualitative evaluation for symmetry is useful in screening for fetal cardiac defects, particularly when it is not possible to obtain standard views, such as when visualization is limited by fetal size or position, oligohydramnios or polyhydramnios, a thick anterior placenta, maternal obesity, or previous lower abdominal surgery.21 Other factors that can influence visualization include operator experience and machine resolution. Even under the most difficult conditions, relative size of cardiac ventricles and great arteries can often still be evaluated.


   Footnotes
 
PII S0029-7844(98)00391-3

Received May 5, 1998. Received in revised form August 11, 1998. Accepted August 20, 1998.


   References
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Abstract
 Materials and Methods
 Results
 Discussion
 References
 
1. Chitty LS, Hunt GH, Moore J, Lobb MO. Effectiveness of routine ultrasonography in detecting fetal structural abnormalities in a low risk population. BMJ 1991;303:1165–9.

2. Constantine G, McCormack J. Comparative audit of booking and mid-trimester ultrasound scans in the prenatal diagnosis of congenital anomalies. Prenat Diagn 1991;11:905–14.[Medline]

3. Luck CA. Value of routine ultrasound scanning at 19 weeks: A four year study of 8849 deliveries. BMJ 1992;304:1474–8.

4. Shirley IM, Bottomley F, Robinson VP. Routine radiographer screening for fetal abnormalities by ultrasound in an unselected low risk population. Br J Radiol 1992;65:564–9.[Abstract]

5. Vergani P, Mariani S, Ghidini A, Schiavina R, Cavallone M, Locatelli A, et al. Screening for congenital heart disease with the four-chamber view of the fetal heart. Am J Obstet Gynecol 1992; 167:1000–3.[Medline]

6. Crane JP, Lefevre ML, Winborn RC, Evans JK, Ewigman BG, Bain RP, et al. A randomized trial of prenatal ultrasonographic screening: Impact on the detection, management, and outcome of anomalous fetuses. Am J Obstet Gynecol 1994;171:392–9.[Medline]

7. Goncalves LF, Jeanty P, Piper JM. The accuracy of prenatal ultrasonography in detecting congenital anomalies. Am J Obstet Gynecol 1994;171:1606–12.[Medline]

8. Kirk JS, Riggs TW, Comstock CH, Lee W, Yang SS, Weinhouse E. Prenatal screening for cardiac anomalies: The value of the routine addition of the aortic root to the four-chamber view. Obstet Gynecol 1994;84:427–31.[Abstract/Free Full Text]

9. Anderson N, Boswell O, Duff G. Prenatal sonography for the detection of fetal anomalies: Results of a prospective study and comparison with prior series. AJR Am J Roentgenol 1995;165:943–50.[Abstract/Free Full Text]

10. Levi S, Schaaps JP, De Havay P, Coulon R, Defoort P. End-result of routine ultrasound screening for congenital anomalies: The Belgian multicentric study 1984–92. Ultrasound Obstet Gynecol 1995; 5:366–71.[Medline]

11. 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;5:372–80.[Medline]

12. Buskens E, Grobbee DE, Frohn-Mulder IM, Stewart PA, Juttmann RE, Wladimiroff JW, et al. Efficacy of routine fetal ultrasound screening for congenital heart disease in normal pregnancy. Circulation 1996;94:67–72.[Abstract/Free Full Text]

13. Kirk JS, Comstock CH, Lee W, Smith RS, Riggs TW, Weinhouse E. Sonographic screening to detect fetal cardiac anomalies: A five-year experience with 111 abnormal cases. Obstet Gynecol 1997;89:227–32.[Abstract]

14. Shipp TD, Bromley B, Hornberger LK, Nadel A, Benacerraf BR. Levorotation of the fetal cardiac axis: A clue for the presence of congenital heart disease. Obstet Gynecol 1995;85:97–102.[Abstract]

15. Crane JM, Ash K, Fink N, Desjardins C. Abnormal fetal cardiac axis in the detection of intrathoracic anomalies and congenital heart disease. Ultrasound Obstet Gynecol 1997;10:90–3.[Medline]

16. Comstock CH, Riggs T, Lee W, Kirk J. Pulmonary to aorta diameter ratio in the normal and abnormal fetus. Am J Obstet Gynecol 1991;165:1038–44.[Medline]

17. Sharland GK, Allan LD. Normal fetal cardiac measurements derived by cross-sectional echocardiography. Ultrasound Obstet Gynecol 1992;2:175–81.[Medline]

18. Cartier MS, Doubilet PM. Fetal aortic and pulmonary artery diameters: Sonographic measurements in growth-retarded fetuses. AJR Am J Roentgenol 1988;151:991–3.[Abstract/Free Full Text]

19. Devore GR. Examination of the fetal heart in the fetus with intrauterine growth retardation using M-mode echocardiography. Semin Perinatol 1988;12:66–79.[Medline]

20. Benacerraf BR, Saltzman DH, Sanders SP. Sonographic sign suggesting the prenatal diagnosis of coarctation of the aorta. J Ultrasound Med 1989;8:65–9.[Abstract]

21. DeVore GR, Medearis AL, Bear MB, Horenstein J, Platt LD. Fetal echocardiography: Factors that influence imaging of the fetal heart during the second trimester of pregnancy. J Ultrasound Med 1993;12:659–63.[Abstract]




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