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 Table of Contents  
REVIEW ARTICLE
Year : 2017  |  Volume : 1  |  Issue : 1  |  Page : 47-54

Fetal echocardiography: A systematic approach


1 Department of cardiology, CHL Hospitals, Indore, Madhya Pradesh, India
2 Shweta Nagar Sonography Clinic and Imaging Centre, Indore, Madhya Pradesh, India

Date of Web Publication7-Apr-2017

Correspondence Address:
Atul Karande
3 Sainath Colony, Sector B, Indore - 452 018, Madhya Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jiae.JIAE_16_17

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  Abstract 

Congenital heart disease (CHD) is the most common birth defect worldwide. The optimal timing for performance of a comprehensive transabdominal fetal echocardiogram is 18–22 weeks gestation. All radiologists should perform screening of the heart during all obstetrical ultrasound studies beyond 18 weeks of gestation. Detailed fetal echocardiography can be performed only with the help of a technically well-quipped ultrasound machine. Skilled expertise and appropriate knowledge are required to perform detailed fetal echocardiography. Despite of limitations, fetal echocardiography can identify most of the CHDs which have major pre- and post-natal implications. This is necessary to delineate the high-risk group of fetuses who are suffering from complex cardiac defects and would require tertiary hospital setup for delivery. This further aids in appropriate postnatal medical as well as surgical management, antenatal parent counseling, and explaining risk factors as well as postnatal outcome.

Keywords: Congenital heart disease, fetal echocardiography, procedure


How to cite this article:
Karande A, Nagar S. Fetal echocardiography: A systematic approach. J Indian Acad Echocardiogr Cardiovasc Imaging 2017;1:47-54

How to cite this URL:
Karande A, Nagar S. Fetal echocardiography: A systematic approach. J Indian Acad Echocardiogr Cardiovasc Imaging [serial online] 2017 [cited 2020 Aug 11];1:47-54. Available from: http://www.jiaecho.org/text.asp?2017/1/1/47/204061


  Introduction Top


Congenital heart disease (CHD) is the most common birth defect, occurring at a rate of 8/1000 births.[1] Out of these, about 3/1000 are major defects which may require life-saving surgery in neonatal period. Nearly 180,000 children are born with heart defects each year in India. Of these, nearly 60,000–90,000 suffer from critical cardiac lesions requiring early intervention.[2] Recent studies have demonstrated that prenatal diagnosis of fetuses with heart defects improves the immediate outcome following delivery because they were born at tertiary hospital.[3],[4] The benefit of delivery at such center is that the newborn baby can be evaluated and prepared for surgery. In addition, fetal echocardiography allows for appropriate counseling to take place.


  Timing of Examination Top


Although fetal echocardiography can be performed at any time after 18 weeks of gestation, the optimal timing for performance of a comprehensive transabdominal fetal echocardiogram is 18–22 weeks of gestation. Images can be more difficult to obtain after 30 weeks gestation as the ratio of fetal body mass-to-amniotic fluid increases. The images of the fetal heart can be acquired at 12–18 weeks; however, it is difficult for interpretation and may require repeat assessment at 18–22 weeks.[5]


  Early Fetal Cardiac Screening Top


A preliminary fetal cardiac screening can be attempted as early as at 14 weeks gestation to look for; (a) color flow in the ductus venosus and spectral waveform. No abnormal color or pulsatile flow should be detected in normal fetuses. (b) Early pick up of tricuspid regurgitation. Any abnormality detected can be a strong marker for cardiac anomaly or chromosomal anomaly and these subjects will require further chromosomal screening and dedicated fetal echocardiography in the second trimester.


  Equipment Top


The technical requirements of fetal echocardiography are more stringent than for routine examinations and can be performed only with the help of a technically advanced ultrasound machine. It should have special grayscale presets such as good cine-loop acquisition, system settings adjusted to higher pulse repetition frequency to minimize persistence, and spatial averaging so as to increase the frame rate. Higher frame rates of 80–100 Hz are frequently needed to view important events occurring at fetal heart rate of 140 beats per minute. The ultrasound machine should have color Doppler, pulse Doppler, and excellent zoom facility without image distortion or any compromise on the image resolution. Appropriate dedicated volume software such as spatial-temporal image correlation, tomographic ultrasound imaging, and like the volume computer-aided diagnosis for multiplanar imaging can also provide additional advantage in image interpretation.


  Training Top


Performance and interpretation of fetal echocardiography require expertise with advanced skills and knowledge. Well-trained cardiologists or obstetrical radiologists who have acquired the appropriate knowledge, correct technique, and skilled expertise should perform fetal echocardiography.


  Indications Top


Maternal indications

(a) Family history of CHD. (b) Metabolic disorders, for example, diabetes, phenylketonuria. (c) Exposure to teratogens. (d) Exposure to prostaglandin synthetase inhibitors, for example, ibuprofen, salicylic acid, and indomethacin. (e) Rubella infection. (f) Autoimmune disease, for example, systemic lupus erythematosus, Sjogren's. (g)In vitro fertilization.[5],[6]

Fetal indications

(a) Abnormal obstetric ultrasound screening. (b) Previous sibling/pregnancy losses with any known cardiac/extra-cardiac abnormality. (c) Chromosomal abnormality. (d) Arrhythmia. (e) Hydrops. (f) Increased first-trimester nuchal translucency. (g) Multiple gestation and suspicion of twin-twin transfusion syndrome. (h) Intrauterine infections.

The highest yield of congenial heart diseases comes from the indication of cardiac or extracardiac structural abnormalities detected by radiologist on routine screening or targeted anomaly scan.[7] It is to be noted that detail echocardiography is indicated in all fetuses detected with increased nuchal translucency thickness during first-trimester screening even if chromosomes are normal.[8]


  Screening of Fetal Heart Top


All radiologists should perform screening of heart (four-chamber view and outflow tracts) during all obstetrical ultrasound studies beyond 18 weeks of gestation. Suspicion or detection of a fetal cardiovascular abnormality requires referral for a detailed fetal echocardiography.

Limited cardiac evaluation or screening of fetal heart can be done within 2–3 min by obtaining transverse view of the upper abdomen and thorax at various levels. The size of the fetus is small at 20 weeks gestation so that to obtain these views a gentle sweep is required up through the thorax.


  Procedure Top


Five views taken for examination of fetal heart are as follows [Figure 1],[Figure 2],[Figure 3],[Figure 4],[Figure 5]:[9]
Figure 1: Normal situs showing the stomach and aorta on the left side of the spine (left). Normal heart position, levocardia (right)

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Figure 2: Four-chamber view of the heart

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Figure 3: Left ventricular outflow tract view

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Figure 4: Right ventricular outflow tract view

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Figure 5: Three-vessel view

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  1. Upper abdominal view for abdominal situs
  2. Four-chamber view
  3. Left ventricular outflow tract (LVOT) view
  4. Right ventricular outflow tract (RVOT) view
  5. Three-vessel view.


Abdominal situs

The viscera-atrial situs can be identified by various ways but most specific of all is the orientation of vessels at the level of upper abdomen - [Figure 6] (a) Situs solitus: In normal controls, stomach and aorta are to the left of the spine, and inferior vena cava (IVC) is on right side slightly anterior to aorta. (b) Situs inversus: In situ s inversus, stomach and aorta are on the right of spine and IVC is on left side slightly anterior to aorta. (c) Right atrial isomerism (asplenia syndrome): In this condition, both aorta and IVC are on one side of spine either the left or right. (d) Left atrial isomerism (polysplenia syndrome): In this condition, IVC is absent at the level of the upper abdomen. Venous structure located posterior to aorta is the azygous or hemizygous vein which carries blood from lower part of body toward heart.
Figure 6: Diagram illustrating normal abdominal situs and other types of abnormal visceroatrial situs

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Four-chamber view

The four-chamber transaxial view acts as a reference plane for obtaining other views. Most of the heart defects can be detected on careful evaluation of four-chamber view in the apical and transverse planes. To obtain an ideal four-chamber view, the transducer is angled cranially from a good transaxial abdominal circumference section with a smooth rib outline and absence of stomach bubble. One should keep the following points in mind while analyzing four-chamber views:

  1. Heart size
  2. Heart position and axis
  3. Chamber symmetry
  4. Two normally and symmetrically opening atrioventricular (AV) valves
  5. Intact interventricular septum (IVS)
  6. Intact crux
  7. Pericardial effusion.


Heart size

Normal heart occupies <1/3rd of area of chest. Cardiomegaly is present when heart occupies more than 1/3rd of chest area [Figure 7].
Figure 7: Cardiomegaly

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Heart position and axis

Heart position [Figure 8]
Figure 8: Diagram illustrating various cardiac positions

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  • Levocardia - Normal heart is located in left hemithorax with apex toward left
  • Dextrocardia - When heart is located in the right hemithorax with apex toward right
  • Mesocardia - When heart is located in the middle of thorax with apex toward midline
  • Dextroposition - When heart is shifted toward the right side with apex toward the left. This is seen in extracardiac anomalies, for example, Diaphragmatic hernia.


Cardiac axis [Figure 9] and [Figure 10]
Figure 9: Normal cardiac axis

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Figure 10: Left axis deviation of the heart (black arrow denotes apex of the heart)

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If we draw two imaginary lines first passing through spine and anterior abdominal wall and another passing through interventricular septum, angle between these two lines is the cardiac axis. Normal axis is 45° ± 20°. Left axis deviation is seen in - Truncus arteriosus, transposition of great arteries (TGA), double outlet right ventricle (DORV), coarctation of aorta (COA), tetralogy of Fallot's (TOF), pulmonary stenosis, and Ebstein's anomaly.

Equal chambers

In normal heart, atria and ventricles are of equal size and contractility during the second trimester (LA = RA, LV = RV). Examples of chamber asymmetry are COA, hypoplastic left heart syndrome (HLHS) [Figure 11], hypoplastic right heart [Figure 12], and Ebstein's anomaly [Figure 13].
Figure 11: The left atrium and left ventricle are small in size in a case of hypoplastic left heart

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Figure 12: The right-sided chambers (black arrow shows hypoplastic right ventricle) are small as compared to left in hypoplastic right heart

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Figure 13: Right atrium is grossly enlarged (black arrow) with apical displacement of septal leaflet in a case of Ebstein's anomaly

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Two opening atrioventricular valves

In normal heart, two separate AV valves open into two separate ventricles. Examples of AV valve abnormality are tricuspid atresia [Figure 14], AV septal defect [Figure 15], and double inlet left ventricle [Figure 16].
Figure 14: Tricuspid atresia with hypoplastic right ventricle which is filling minimally through a ventricular septal defect (white arrow)

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Figure 15: Defective crux in a case of atrioventricular septal defect

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Figure 16: Postnatal echo of double inlet left ventricle

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Intact interventricular septum

A lateral four-chamber view [Figure 17] and [Figure 18] is ideal for the evaluation of IVS. Malalignment ventricular septal defect (VSD) can be excluded by obtaining LVOT view of heart.
Figure 17: Normal interventricular septum

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Figure 18: Inlet ventricular septal defect

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Intact crux

Crux is the junction of membranous part of the IVS, septum primum of interatrial septum, and septal leaflets of the mitral and tricuspid valves [Figure 19]. Crux of the heart is defective in AV septal defect [Figure 15].
Figure 19: Four-chamber view showing normal crux (white arrow)

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Pericardial effusion

Small amount of fluid posterior to the left ventricle which disappears in diastole is a normal finding. It is important only when fluid is noted at either surface of the heart. Pericardial effusion may be mild, moderate, or massive [Figure 20] and [Figure 21].
Figure 20: Minimal pericardial fluid (black arrow) Normal finding

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Figure 21: Pericardial effusion

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Outflow tract views

In this view, one should look for the normal opening semilunar valves of the outflow tracts and their thickness. Any significant asymmetry in the size of outflow tracts is considered abnormal. Interrelationship (crossing over) of outflow tracts is important to rule out TGA. CHDs which can be detected in the outflow tract views are – TOF [Figure 22], TGA [Figure 23], truncus arteriosus, pulmonary atresia, and DORV [Figure 24].
Figure 22: The aorta is seen overriding the interventricular septum on the left ventricle outflow view in tetralogy of Fallot

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Figure 23: Both the outflow tracts are running parallel to each other in a case of complete transposition of great artery

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Figure 24: In a case of double outlet right ventricle. Both the outflow tracts are arising from the right ventricle

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Three vessel view

This view can be obtained by sweeping the transducer cranially toward fetal neck from the scan plane of RVOT view. In this view, the three vessels, i.e., ductus arteriosus, transverse aortic arch, and superior vena cava are normally oriented from the left to right respectively with respect to the fetal spine. Any abnormal orientation or asymmetry if present should be noted. This view is very useful in detecting pulmonary atresia, aortic atresia, and COA, otherwise COA is difficult to diagnose in fetal life [Figure 25]. In normal fetuses, flow in ductus arteriosus and transverse aortic arch is in the same direction. Reverse flow in ductus arteriosus indicates pulmonary atresia [Figure 26] and small transverse arch showing reverse flow is diagnostic of HLHS [Figure 27].
Figure 25: Small transverse aortic arch (black arrows) in coarctation of aorta

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Figure 26: Reversal of flow in ductal arteriosus in pulmonary atresia

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Figure 27: Reversal of flow in transverse aortic arch in hypoplastic left heart syndrome (white arrow)

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Limitations of Fetal Echocardiography

Because of the small size of abnormal cardiac structures and limitations of resolution of equipment, several forms of CHDs are difficult to diagnose in fetal life, for example, small VSD, partial anomalous pulmonary venous connections, mild valvular stenosis, coronary artery anomalies, and COA. Out of these, only coronary artery anomalies and COA have significant clinical implications if at all they are missed during examination. Some CHDs may be missed at early pregnancy because they develop or progress in severity later in gestation, for example, TOF, COA, restrictive foramen ovale and valvular stenosis/atresia. Some lesions have been reported to resolve as the pregnancy advances, for example, VSD, atrial septal aneurysm. Because of fetal circulation, it is not possible to diagnose certain conditions, for example, PDA, ostium secundum ASD.


  Conclusion Top


The aim of fetal echocardiography is to identify CHDs which have major pre- and post-natal implications. This is necessary to identify the high-risk group of fetuses who are suffering from complex cardiac defects and would require tertiary hospital setup for delivery. It will guide us in providing appropriate antenatal parent counseling and thereby explaining the risk and postnatal outcome. Thereafter, it helps in planning appropriate postnatal medical as well as surgical management.

With the availability of high-resolution ultrasound machine, it is now possible to diagnose most of the major defects early in mid-trimester. As CHDs are more common even in low-risk population, training programs should be organized to guide radiologists on performing routine screening of the heart during any second-trimester obstetric examinations. We need a large number of good quality ultrasound machine and trained personnel who can perform detail fetal echocardiography. We also need enough number of tertiary cardiac units which can handle babies with CHD who require immediate care and intervention early during neonatal period to reduce the mortality and morbidity.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Fyler DC, Buckley LP, Hellenbrand WE. Report of the New England Regional Infant Cardiac Program. Pediatrics 1980;65 Suppl 2:375-461.  Back to cited text no. 1
    
2.
Working Group on Management of Congenital Heart Diseases in India. Consensus on timing of intervention for common congenital heart disease. Indian Pediatr 2008;45:117-26.  Back to cited text no. 2
    
3.
Verheijen PM, Lisowski LA, Stoutenbeek P, Hitchcock JF, Brenner JI, Copel JA, et al. Prenatal diagnosis of congenital heart disease affects preoperative acidosis in the newborn patient. J Thorac Cardiovasc Surg 2001;121:798-803.  Back to cited text no. 3
    
4.
Tworetzky W, McElhinney DB, Reddy VM, Brook MM, Hanley FL, Silverman NH. Improved surgical outcome after fetal diagnosis of hypoplastic left heart syndrome. Circulation 2001;103:1269-73.  Back to cited text no. 4
    
5.
Rychik J, Ayres N, Cuneo B, Gotteiner N, Hornberger L, Spevak PJ, et al. American Society of echocardiography guidelines and standards for performance of the fetal echocardiogram. J Am Soc Echocardiogr 2004;17:803-10.  Back to cited text no. 5
    
6.
Hansen M, Kurinczuk JJ, Bower C, Webb S. The risk of major birth defects after intracytoplasmic sperm injection and in vitro fertilization. N Engl J Med 2002;346:725-30.  Back to cited text no. 6
    
7.
Wood D, Respondek-Liberska M, Puerto B, Weiner S; World Association of Perinatal Medicine Ultrasonography Working Group. Perinatal echocardiography: Protocols for evaluating the fetal and neonatal heart. J Perinat Med 2009;37:5-11.  Back to cited text no. 7
    
8.
Ghi T, Huggon IC, Zosmer N, Nicolaides KH. Incidence of major structural cardiac defects associated with increased nuchal translucency but normal karyotype. Ultrasound Obstet Gynecol 2001;18:610-4.  Back to cited text no. 8
    
9.
Gardiner HM. Antenatal detection of heart defects is important and achievable. Ultrasound 2005;3:164-9.  Back to cited text no. 9
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17], [Figure 18], [Figure 19], [Figure 20], [Figure 21], [Figure 22], [Figure 23], [Figure 24], [Figure 25], [Figure 26], [Figure 27]



 

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  In this article
   Abstract
  Introduction
   Timing of Examin...
   Early Fetal Card...
  Equipment
  Training
  Indications
   Screening of Fet...
  Procedure
  Conclusion
   References
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