1. (D) Abnormal findings suggestive of a fetal cardiac anomaly on obstetrical screening ultrasound is the most common reason to refer for formal fetal echocardiography, and in ˜40% to 50% of these pregnancies, CHD is confirmed. However, all of these are appropriate indications for performing a fetal echocardiogram. Of note, rubella is an extremely rare maternal infection, but does carry increased risk for CHD, especially pulmonary stenosis. Fetal rhythm abnormalities affect ˜1% to 2% of pregnancies and account for <10% of referrals for formal fetal echocardiography. PKU is a rare metabolic disorder that in pregnant women is associated with CHD, particularly when the mother’s diet is not well controlled. There is a 10- to 15-fold increased risk of CHD in the fetus when the mother has elevated maternal serum levels of phenylalanine >15 mg/dL. However, if the mother has good preconception control and maintains levels <10 mg/dL during the first trimester, the risk is greatly reduced and a fetal echocardiogram may not be necessary.

2. (C) The right ventricle ejects 55% to 60% of combined fetal cardiac output while the left ventricle ejects 40% to 45%. Cardiac output increases significantly during gestation, but the relative amounts of output from these two parallel circulations remain relatively the same.

3. (E) Retinoic acid is a vitamin A derivative used to treat severe acne and has been associated with increased risk of fetal anomalies in multiple organ systems (CNS, craniofacial, branchial arches, and cardiac). Cardiac anomalies most often seen in retinoic acid exposure included conotruncal defects and aortic arch anomalies. The other answers are paired incorrectly. Alcohol exposure has an increased risk of septal defects such as VSD in association with fetal alcohol syndrome. Salicylates such as NSAIDs (indomethacin) are associated with premature ductus arteriosus closure usually due to exposure with the highest risk in the third trimester. Fortunately, the constriction is usually mild and can be reversed with discontinuation of the drug if recognized early. Lithium is associated with Ebstein anomaly, but more recent studies have suggested lower risk level than previously thought.

4. (B) The standard four-chamber view of the heart is good for visualizing the atria, ventricles, atrioventricular valves, pulmonary veins, and ventricular septum. In addition, it is good for assessing cardiac size and position within the fetal thorax. The three-vessel view and three-vessel tracheal views are used to assess for arch anomalies such as vascular ring and right aortic arch. The outflow tract views are used to assess for conotruncal defects such as tetralogy of Fallot and d-TGA. The sagittal arch views are best for assessing the ductal and aortic arch for conditions such as coarctation, but the three-vessel tracheal view can also be used to assess these structures.

5. (C) Pulsed-wave Doppler of mitral valve inflow and aortic outflow can be used to assess irregular fetal rhythm (Figure 8.9). In addition, M-mode and TDI modalities can also be used to assess irregular fetal rhythm. PACs are the most common cause of fetal arrhythmia. Vascular ring, HLHS, d-TGA, and anomalies of the branch pulmonary arteries are best assessed using sweeps with 2D (grayscale) and color Doppler.

6. (A) Fetal arrhythmias occur in 1% to 3% of all pregnancies. PACs comprise the largest percentage of these rhythm abnormalities followed by PVCs. Fetal SVT, atrial flutter, and complete heart block account for <10% of all reported fetal arrhythmias.

7. (B) The normal fetal heart comprises about one-third of the fetal thorax, ranging from 25% to 35%.

8. (B) Obstructed TAPVR is still a surgical emergency because these patients cannot be fully stabilized with medical intervention alone. Due to the inability of blood to exit the lungs effectively and provide proper oxygen delivery to the body, these neonates are at risk for progressive hypoxia (cyanosis) and acidosis.

9. (D) This is the mechanical PR interval, measured from the beginning of atrial inflow (mitral A wave) to the beginning of ventricular ejection.

10. (E) With lack of antegrade flow across the atretic pulmonary valve, fetuses with pulmonary atresia with intact ventricular septum often have reversal of flow across the ductus arteriosus into the hypoplastic main pulmonary artery and branch pulmonary arteries. The other listed congenital heart lesions all typically have a normally functioning pulmonary valve with antegrade flow into the main pulmonary artery and ductus arteriosus.

11. (C) The normal fetal heart rate ranges from 100 to 180 bpm throughout gestation. Fetal bradycardia is defined as a sustained heart rate less than 100 bpm while fetal tachycardia as a sustained rate greater than 180 bpm.

12. (A) At term, 10% of fetal cardiac output perfuses the lungs. The remainder of this deoxygenated blood is directed through the ductus arteriosus to the descending aorta and placenta for oxygenation.

13. (A) The normal leftward axis of the fetal heart (relative to the midline) ranges from 30 degrees to 60 degrees.

14. (C) Because of limited antegrade blood flow across the critically stenotic aortic valve, flow within the aortic arch is supplied retrograde from the ductus arteriosus. The other listed congenital heart lesions all typically have a normally functioning aortic valve with antegrade flow into the ascending aorta and transverse aortic arch and antegrade flow from the ductus arteriosus to the descending aorta.

15. (1-D, 2-B, 3-A, 4-C, 5-E) Lithium has been shown in studies to be associated with fetal Ebstein anomaly as well as atrial septal defects and atrioventricular valve atresia. Fetal alcohol syndrome has been commonly associated with septal defects including atrial and ventricular septal defects and is less commonly associated with coarctation and conotruncal defects. Indomethacin is a potent ductal constrictor. Coarctation of the aorta and LVOT obstruction have been described in fetal hydantoin syndrome. Exposure to isotretinoin during gestation has been associated with fetal d-TGA as well as septal defects and conotruncal anomalies.

16. (A) Ebstein anomaly is associated with a 15% to 20% incidence of rhythm abnormalities, most notably Wolff-Parkinson-White syndrome and SVT.

17. (B) HLHS with restrictive atrial septum. In HLHS, there is often mitral and/or aortic atresia such that blood cannot exit the left heart. Therefore, HLHS requires an adequate atrial communication to allow the blood to exit the left atrium and join the rest of the circulation to the body. If there is not an adequate atrial communication, these patients can present like obstructed TAPVR due to back up of blood into the lungs resulting in severe pulmonary congestion, worsening hypoxia, and acidosis. These infants are often critically ill at birth and require either emergent opening of the atrial septum via catheterization or surgical septectomy.

18. (B) PGE infusion. This image shows a fetus with HLHS of the mitral atresia and aortic atresia variety. There is a single RV that has enlarged to take over the apex of the heart. The RA and LA are also seen with a wide-open atrial communication between them such that this child does not appear to be at risk for restrictive atrial septum, so a balloon atrial septostomy or immediate surgery should not be warranted. PGE infusion is indicated to maintain ductal patency for systemic blood flow and can be given through a peripheral IV, so placement of a central venous line is not always necessary. PGE causes the side effect of apnea in ˜50% of babies so intubation may be necessary, but not in all patients. Therefore, PGE1 is the only therapy that needs to be started in this patient with 100% certainty, shortly after birth.

19. (A) Hydrops. This image depicts a fetus with Ebstein anomaly (EA) as noted by the inferiorly displaced tricuspid valve leaflets, severe RA, and RV dilation with massive cardiomegaly (wall-to-wall heart). EA fetuses can develop all the problems listed above, but the highest risk and one of the greatest concerns is hydrops because it can lead to fetal demise. Development of hydrops and/or fetal demise has been reported in up to 45% of fetal EA cases. Rhythm disturbances have been reported in up to 17% of EA fetuses, with the most common being SVT. Growth restriction and prematurity also occur more frequently in EA and must be monitored closely. Polyhydramnios can be part of the constellation of hydrops and can also increase the risk for prematurity.

20. (D) Heart block. The diagnosis pictured is congenitally corrected transposition of the great arteries (ccTGA). Note that the left-sided ventricle has a lower attachment of the AV valve which is the tricuspid valve, has a moderator band across the apex, and is more trabeculated because it is the morphologic RV. By comparison, the more anterior and rightward ventricle has a higher-inserted AV valve which is the mitral valve, smooth-walled septum with no AV valve attachments, and bullet chamber with no moderator band. Not pictured here are the outflow tracts which are usually oriented in an L-TGA configuration with the aorta arising anterior and leftward from the left-sided RV and the pulmonary artery arising posterior and rightward to the aorta from the right-sided LV. There are often associated heart defects in ccTGA, such as VSD, pulmonary stenosis, and tricuspid valve abnormalities which can be seen in up to 80% of cases. Growth restriction, hydrops, and polyhydramnios are unlikely to occur in cases of ccTGA unless there is associated extracardiac disease, a genetic syndrome, or fetal CHF (in this case it was noted that the heart function and valve function were normal). SVT is rarely noted to occur in ccTGA, but heart block is a well-known risk due to the abnormal position of the AV node and bundle of His which can lead to early fibrosis. Up to 20% of fetuses with ccTGA have been reported to have varying degrees of AV block and associated bradycardia. If complete heart block develops, this can put the fetus at risk of developing hydrops if the ventricular escape rate is very slow. This would also change the delivery management.