GET YOUR BEARINGS
Before interpreting intracardiac anatomy, what orientation should be established first?
Correct Response: What are fetal position and situs?
Teaching Pearl: Determine fetal lie/position and establish situs before assigning right and left or interpreting cardiac anatomy.
Which ventricle contains the moderator band?
Correct Response: What is the morphologic right ventricle?
Teaching Pearl: The moderator band and coarse trabeculations help identify the morphologic right ventricle.
In normal fetal circulation, blood crosses the foramen ovale in which direction?
Correct Response: What is from the right atrium to the left atrium?
Teaching Pearl: This right-to-left shunt preferentially directs relatively oxygenated placental blood toward the left heart and ultimately the coronary and cerebral circulations.
Which standard cardiac view best allows comparison of ventricular size, AV valve offset, and the crux of the heart?
Correct Response: What is the four-chamber view?
Teaching Pearl: The four-chamber view is foundational but cannot exclude many important conotruncal abnormalities. Evaluation of the outflow tracts and upper mediastinum is essential.
For accurate spectral Doppler velocity measurement, how should the ultrasound beam be oriented relative to the direction of blood flow?
Correct Response: What is as parallel to blood flow as possible?
Teaching Pearl: Doppler velocity measurements are angle dependent. A small angle of insonation improves accuracy, while larger angles can underestimate true velocity.
Which congenital heart defect is classically associated with trisomy 21?
Correct Response: What is an atrioventricular septal defect?
Teaching Pearl: AVSD has a strong association with trisomy 21, although AVSD can occur with other genetic conditions or without an identified chromosomal abnormality.
In the normal fetus, the cardiac apex points in what direction?
Correct Response: What is toward the fetal left?
Teaching Pearl: Normal levocardia describes a leftward-pointing apex. Cardiac position and situs should still be described separately.
Which atrioventricular valve normally inserts more apically toward the cardiac apex?
Correct Response: What is the tricuspid valve?
Teaching Pearl: Normal AV valve offset helps distinguish the morphologic right ventricle from the left ventricle.
Which fetal vessel carries oxygenated blood from the placenta toward the fetus?
Correct Response: What is the umbilical vein?
Teaching Pearl: The umbilical vein carries oxygenated blood toward the fetus, while the two umbilical arteries return relatively deoxygenated blood to the placenta.
Which three vessels are normally visualized in the fetal three-vessel view?
Correct Response: What are the main pulmonary artery, ascending aorta, and superior vena cava?
Teaching Pearl: The three vessels have a characteristic arrangement and generally decrease in caliber from the pulmonary artery to the aorta to the SVC.
What Doppler pattern characterizes pathologic atrioventricular valve regurgitation?
Correct Response: What is a high-velocity retrograde jet occurring during systole?
Teaching Pearl: AV valve regurgitation occurs during ventricular systole. Color Doppler identifies the regurgitant jet, while spectral Doppler can characterize its timing and velocity when clinically useful.
A large ventricular septal defect, overriding aorta, right ventricular outflow tract obstruction, and right ventricular hypertrophy define which congenital heart defect?
Correct Response: What is Tetralogy of Fallot?
Teaching Pearl: Prenatally, the key findings are the VSD, overriding aorta, and the degree of RV outflow tract and pulmonary artery obstruction. Right ventricular hypertrophy is generally a postnatal manifestation and may not be prominent prenatally.
Clue: Approximately what angle does the normal fetal cardiac axis form relative to the anteroposterior midline?
Correct Response: What is approximately 45° to the left?
Teaching Pearl: A markedly abnormal cardiac axis can be an early clue to congenital heart disease or extracardiac thoracic pathology.
What feature of the left atrial appendage helps distinguish it morphologically from the right atrial appendage?
Correct Response: What is its narrow, finger-like morphology?
Teaching Pearl: Atrial morphology is defined by appendage anatomy, although atrial appendage morphology can be difficult to assess prenatally.
Which fetal shunt allows a portion of umbilical venous blood to bypass the hepatic circulation?
Correct Response: What is the ductus venosus?
Teaching Pearl: The ductus venosus provides a pathway from the umbilical venous circulation toward the IVC and facilitates preferential streaming of highly oxygenated blood.
Which vessel is normally the largest and most anterior-left vessel in the three-vessel view?
Correct Response: What is the main pulmonary artery?
Teaching Pearl: In fetal life, the main pulmonary artery is normally slightly larger than the ascending aorta and continues toward the ductal arch.
When assessing fetal rhythm using M-mode, which two types of structures should the cursor intersect simultaneously?
Correct Response: What are an atrial wall and a ventricular wall?
Teaching Pearl: Recording atrial and ventricular mechanical events simultaneously allows assessment of the relationship between atrial and ventricular contractions and helps classify fetal arrhythmias.
In complete transposition of the great arteries, which great artery arises from the morphologic right ventricle?
Correct Response: What is the aorta?
Teaching Pearl: Complete TGA is ventriculoarterial discordance: the aorta arises from the morphologic RV and the pulmonary artery from the morphologic LV. Failure of the great arteries to cross normally is an important prenatal clue.
The heart is located predominantly in the left chest, but its apex points toward the right. What term describes this orientation?
Correct Response: What is dextrocardia?
Teaching Pearl: Dextrocardia refers to a rightward-directed cardiac apex. Cardiac situs should be determined independently.
A markedly apically displaced tricuspid valve with atrialization of part of the right ventricle suggests what diagnosis?
Correct Response: What is Ebstein anomaly?
Teaching Pearl: The hallmark is apical displacement of the tricuspid valve, often accompanied by significant tricuspid regurgitation, right atrial enlargement, and atrialization of the right ventricle.
Name the three major physiologic shunts of the fetal circulation.
Correct Response: What are the ductus venosus, foramen ovale, and ductus arteriosus?
Teaching Pearl: These three shunts allow blood to partially bypass the liver and largely bypass the high-resistance, fluid-filled fetal lungs.
Which fetal arch has the classic "candy cane" appearance and gives rise to the head and neck vessels?
Correct Response: What is the aortic arch?
Teaching Pearl: The aortic arch gives rise to the brachiocephalic, left common carotid, and left subclavian arteries. The ductal arch has a broader "hockey stick" configuration and does not give rise to head and neck vessels.
A fetus has an atrial rate of approximately 450 beats per minute with a slower ventricular response. What rhythm is most likely?
Correct Response: What is atrial flutter?
Teaching Pearl: Fetal atrial flutter typically produces very rapid atrial activity, often 300–500 bpm, with variable AV conduction. A 2:1 conduction pattern is common.
A fetus has a severely hypoplastic left ventricle, mitral and aortic obstruction, and retrograde flow in the aortic arch. What diagnosis is most likely?
Correct Response: What is hypoplastic left heart syndrome?
Teaching Pearl: In HLHS, systemic circulation becomes ductal-dependent after birth. Prenatal assessment should also evaluate the atrial septum and pulmonary venous flow because restriction at the atrial level can significantly affect neonatal stability.
The heart is displaced into the right hemithorax, but the apex retains its usual leftward orientation. What is this called?
Correct Response: What is dextroposition?
Teaching Pearl: Cardiac position is not the same as cardiac axis. Extracardiac mass effect, such as a thoracic lesion, can shift the heart without reversing its intrinsic orientation.
The tricuspid valve and morphologic right ventricle are located on the fetal left. What fundamental cardiac relationships should you evaluate next?
What are the atrioventricular and ventriculoarterial connections?
Teaching Pearl: Morphologic identity matters more than geographic right or left. Discordant connections should raise concern for conditions such as congenitally corrected transposition of the great arteries.
In severe left-sided cardiac obstruction, what abnormal direction of flow may be seen across the foramen ovale?
Correct Response: What is left-to-right flow?
Teaching Pearl: Reversal or restriction of normal right-to-left atrial flow can be an important clue to severe left-heart obstruction. The adequacy of atrial-level communication may also have major implications for postnatal stability.
On the three-vessel-trachea view, the ductal and aortic arches normally converge toward which vessel?
Correct Response: What is the descending aorta?
Teaching Pearl: The normal aortic and ductal arches form a V-shaped configuration as they join the descending aorta to the left of the trachea. Abnormal vessel size, course, or relationship to the trachea may suggest arch pathology.
Reversed or absent a-wave flow in the ductus venosus most directly reflects abnormal pressure or compliance involving which side of the fetal heart?
Correct Response: What is the right heart or right atrium?
Teaching Pearl: The ductus venosus a-wave corresponds to atrial contraction. Abnormal a-wave flow may reflect increased right atrial pressure or impaired ventricular compliance, although the finding is not specific to a single disease.
A fetus has an atrioventricular septal defect, abnormal systemic venous anatomy, and interruption of the IVC with azygos continuation. What broader diagnosis should you strongly consider?
Correct Response: What is heterotaxy, particularly left atrial isomerism?
Teaching Pearl: Interrupted IVC with azygos continuation is strongly associated with left atrial isomerism. When suspected, perform a systematic evaluation of situs, systemic and pulmonary venous connections, intracardiac anatomy, and rhythm.