Fetal circulation US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Fetal circulation. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Fetal circulation US Medical PG Question 1: A 5-week-old infant born at 36 weeks' gestation is brought to the physician for a well-child examination. Her mother reports that she previously breastfed her for 15 minutes every 2 hours but now feeds her for 40 minutes every 4 hours. The infant has six wet diapers and two stools daily. She currently weighs 3500 g (7.7 lb) and is 52 cm (20.4 in) in length. Vital signs are with normal limits. Cardiopulmonary examination shows a grade 4/6 continuous murmur heard best at the left infraclavicular area. After confirming the diagnosis via echocardiography, which of the following is the most appropriate next step in management of this patient?
- A. Surgical ligation
- B. Indomethacin infusion
- C. Reassurance and follow-up (Correct Answer)
- D. Percutaneous device closure
- E. Prostaglandin E1 infusion
Fetal circulation Explanation: ***Reassurance and follow-up***
- This 5-week-old infant (41 weeks postmenstrual age) with a PDA is **hemodynamically stable** with normal vital signs, appropriate weight gain (3500g), adequate urine output (6 wet diapers/day), and effective feeding despite longer feeding times.
- The change in feeding pattern (40 minutes every 4 hours vs 15 minutes every 2 hours) actually represents **improved feeding efficiency** with the same total daily feeding time but longer intervals between feeds.
- Despite the loud murmur (grade 4/6), there are **no signs of congestive heart failure** (no tachypnea, no hepatomegaly, no failure to thrive).
- In a **clinically stable infant** without heart failure symptoms, **watchful waiting with close follow-up** is appropriate as many PDAs close spontaneously, particularly in infants born at 36 weeks gestation.
- Intervention would be indicated if the infant develops signs of heart failure or failure to thrive.
*Indomethacin infusion*
- **Indomethacin** (a prostaglandin synthesis inhibitor) is only effective for PDA closure in the **early neonatal period** (typically first 7-10 days of life) when the ductus is still responsive to prostaglandins.
- At **5 weeks of age** (41 weeks postmenstrual age), the ductus arteriosus has undergone structural maturation and is **no longer responsive** to prostaglandin inhibitors.
- This infant is well past the window for pharmacologic closure with indomethacin.
*Surgical ligation*
- **Surgical ligation** would be indicated for a hemodynamically significant PDA causing heart failure symptoms that are refractory to medical management.
- This infant is **hemodynamically stable** without signs of heart failure, so surgical intervention is not warranted at this time.
- Surgery carries significant risks and should be reserved for cases where conservative management has failed.
*Prostaglandin E1 infusion*
- **Prostaglandin E1** is used to **maintain ductal patency** in ductal-dependent congenital heart lesions (e.g., critical coarctation, transposition of great arteries, pulmonary atresia).
- This would be contraindicated in PDA as it would **worsen** the condition by keeping the ductus open.
- The clinical picture suggests isolated PDA, not a ductal-dependent lesion.
*Percutaneous device closure*
- **Percutaneous device closure** is typically performed in **older infants and children** (usually >6 months old and >6 kg) with persistent hemodynamically significant PDA.
- This 5-week-old infant weighing 3500g is **too small** for device closure.
- Additionally, the infant is currently stable and may not require intervention if the PDA closes spontaneously.
Fetal circulation US Medical PG Question 2: A 38-year-old woman, gravida 2, para 1, at 24 weeks' gestation comes to the physician for a routine prenatal evaluation. She has no history of major medical illness and takes no medications. Fetal ultrasonography shows a cardiac defect resulting from abnormal development of the endocardial cushions. This defect is most likely to result in which of the following?
- A. Transposition of the great vessels
- B. Atrioventricular septal defect (Correct Answer)
- C. Dextrocardia
- D. Patent foramen ovale
- E. Sinus venosus defect
Fetal circulation Explanation: ***Atrioventricular septal defect***
- **Endocardial cushion defects** are a hallmark of atrioventricular septal defects, leading to a common atrioventricular valve and an interatrial and/or interventricular communication.
- This defect commonly presents in individuals with **Down syndrome (Trisomy 21)**, though it can occur in isolation.
*Transposition of the great vessels*
- This defect results from abnormal **spiraling of the conotruncal septum**, not from endocardial cushion malformation.
- It leads to the **aorta arising from the right ventricle** and the **pulmonary artery from the left ventricle**, a circulation incompatible with life without a shunt.
*Dextrocardia*
- **Dextrocardia** is a condition where the heart is located on the right side of the chest, usually due to abnormal embryonic folding, and is not directly caused by endocardial cushion defects.
- It can occur as an isolated finding or as part of a more complex syndrome like **Kartagener syndrome**.
*Patent foramen ovale*
- A **patent foramen ovale** is a common remnant of fetal circulation, occurring when the foramen ovale fails to close after birth.
- It is a defect of the **atrial septum secondary to incomplete fusion between the septum primum and septum secundum**, not an endocardial cushion defect.
*Sinus venosus defect*
- A **sinus venosus defect** is a type of atrial septal defect occurring near the entrance of the superior or inferior vena cava.
- It is caused by **abnormal development of the sinus venosus** and is not directly related to endocardial cushion malformation.
Fetal circulation US Medical PG Question 3: An investigator is studying the relationship between fetal blood oxygen saturation and intrauterine growth restriction using MRI studies. The magnetic resonance transverse relaxation time (T2) is inversely related to the concentration of deoxyhemoglobin so that high concentrations of deoxyhemoglobin produce a low signal intensity on T2-weighted MRI. In a normal fetus, the T2 signal is most likely to be the highest in which of the following vessels?
- A. Descending aorta
- B. Superior vena cava
- C. Ductus venosus (Correct Answer)
- D. Pulmonary veins
- E. Right atrium
Fetal circulation Explanation: ***Ductus venosus***
- The **ductus venosus** shunts highly oxygenated blood directly from the **umbilical vein** to the inferior vena cava, bypassing the liver.
- This vessel carries the most oxygen-rich blood in the fetal circulation (lowest deoxyhemoglobin concentration), resulting in the **highest T2 signal intensity**.
*Descending aorta*
- The descending aorta receives a mixture of oxygenated blood from the left ventricle and deoxygenated blood from the **pulmonary artery** via the **ductus arteriosus**.
- This mixing reduces its overall oxygen saturation compared to the umbilical vein and ductus venosus.
*Superior vena cava*
- The superior vena cava carries **deoxygenated blood** from the upper body and head back to the right atrium.
- This vessel has a low oxygen saturation and high deoxyhemoglobin concentration, leading to a **low T2 signal**.
*Pulmonary veins*
- In a normal fetal circulation, the **lungs are not fully functional**, and pulmonary blood flow is relatively low.
- The pulmonary veins carry only a small amount of moderately oxygenated blood returning from the developing lungs, which is significantly less oxygenated than blood in the ductus venosus.
*Right atrium*
- The right atrium receives **mixed blood** from both the superior and inferior vena cava.
- While it receives some oxygenated blood from the inferior vena cava via the ductus venosus, this is diluted by deoxygenated blood, resulting in lower oxygen saturation than the blood within the ductus venosus itself.
Fetal circulation US Medical PG Question 4: A 4-day-old boy is monitored in the well baby nursery. He was born to a G1P1 mother at 36 weeks gestation. The child is doing well, and the mother is recovering from vaginal delivery. On physical exam, there is an arousable infant who is crying vigorously and is mildly cyanotic. A red reflex is noted bilaterally on ophthalmologic exam. The infant's fontanelle is soft, and his sucking reflex is present. A positive Babinski sign is noted on physical exam bilaterally. A continuous murmur is auscultated on cardiac exam. Which of the following would most likely have prevented the abnormal finding in this infant?
- A. Prostaglandins
- B. Indomethacin (Correct Answer)
- C. Folic acid
- D. Betamethasone
- E. Oxygen therapy
Fetal circulation Explanation: ***Indomethacin***
- The continuous murmur and mild cyanosis in a premature infant (36 weeks gestation) suggest a **patent ductus arteriosus (PDA)**.
- **Prophylactic indomethacin** given to premature infants shortly after birth can prevent the development of a symptomatic PDA by inhibiting prostaglandin synthesis, which promotes ductal closure.
- Indomethacin, a **prostaglandin inhibitor**, prevents prostaglandin-mediated vasodilation and facilitates closure of the ductus arteriosus in the early postnatal period.
- This is particularly important in premature infants who are at higher risk for persistent PDA due to immature ductal responsiveness.
*Prostaglandins*
- **Prostaglandins** (specifically PGE1) are used to *keep* the ductus arteriosus open, which is desirable in certain cyanotic congenital heart defects that require ductal patency for systemic or pulmonary blood flow (e.g., transposition of great arteries, pulmonary atresia).
- Administering prostaglandins in this case would worsen the **patent ductus arteriosus** by preventing its closure.
*Folic acid*
- **Folic acid** supplementation during pregnancy is crucial for preventing neural tube defects such as spina bifida and anencephaly.
- It has no role in preventing or treating a **patent ductus arteriosus** or other cardiovascular abnormalities in newborns.
*Betamethasone*
- **Betamethasone** is a corticosteroid given to pregnant mothers at risk of preterm delivery (between 24-34 weeks) to accelerate fetal lung maturity and reduce respiratory distress syndrome.
- While it improves neonatal outcomes in premature infants, it does not directly prevent the development of **patent ductus arteriosus**.
*Oxygen therapy*
- **Oxygen therapy** is used to treat hypoxemia and improve tissue oxygenation in cyanotic infants.
- While increased oxygen tension can contribute to ductal constriction, oxygen therapy alone is not a primary or reliable preventative measure for PDA in premature infants.
- Indomethacin remains the definitive pharmacologic intervention for prevention of symptomatic PDA.
Fetal circulation US Medical PG Question 5: A newborn infant comes to the attention of the neonatal care unit because he started having heavy and rapid breathing. In addition, he was found to be very irritable with pale skin and profuse sweating. Finally, he was found to have cold feet with diminished lower extremity pulses. Cardiac auscultation reveals a harsh systolic murmur along the left sternal border. Notably, the patient is not observed to have cyanosis. Which of the following treatments would most likely be effective for this patient's condition?
- A. Prostaglandin I2
- B. Leukotriene E4
- C. Prostaglandin E2
- D. Prostaglandin E1 (Correct Answer)
- E. Thromboxane A2
Fetal circulation Explanation: ***Prostaglandin E1***
- The newborn's presentation with **respiratory distress, irritability, pale skin, profuse sweating, cold feet, diminished lower extremity pulses**, and a **harsh systolic murmur** without cyanosis is highly suggestive of **coarctation of the aorta**.
- **Prostaglandin E1 (PGE1)** is critical in maintaining the **patency of the ductus arteriosus**, which allows for blood flow to the lower body when there is severe obstruction like coarctation.
*Prostaglandin I2*
- **Prostaglandin I2 (PGI2)**, or **prostacyclin**, is a potent **vasodilator** and **platelet aggregation inhibitor**.
- While it has vascular effects, it is not the primary prostaglandin used to maintain ductal patency in newborns with critical congenital heart disease.
*Leukotriene E4*
- **Leukotrienes** are mediators of inflammation and allergic reactions, primarily involved in bronchoconstriction and vascular permeability.
- They do not play a significant role in the management of congenital heart defects requiring ductal patency.
*Prostaglandin E2*
- While **prostaglandin E2 (PGE2)** also contributes to maintaining ductal patency, **PGE1** is the preferred and more commonly used agent for this purpose in clinical practice.
- Both PGE1 and PGE2 are members of the E-series prostaglandins, but PGE1 is the standard pharmaceutical intervention.
*Thromboxane A2*
- **Thromboxane A2 (TXA2)** is a potent **vasoconstrictor** and promotes **platelet aggregation**.
- Its effects are opposite to what is desired in this patient, where maintained vessel patency (ductus arteriosus) is crucial.
Fetal circulation US Medical PG Question 6: A G1P0 mother gives birth to a male infant at 37 weeks gestation. She received adequate prenatal care and took all her prenatal vitamins. She is otherwise healthy and takes no medications. On the 1 month checkup, examination revealed a machine-like murmur heard at the left sternal border. Which of the following medications would be most appropriate to give the infant to address the murmur?
- A. Prostaglandin E1
- B. Prostaglandin E2
- C. Indomethacin (Correct Answer)
- D. Digoxin
- E. Bosentan
Fetal circulation Explanation: ***Indomethacin***
- A **machine-like murmur** heard at the left sternal border in an infant is highly characteristic of a **patent ductus arteriosus (PDA)**.
- **Indomethacin** is a **prostaglandin synthesis inhibitor** (NSAID) that promotes closure of a PDA by blocking prostaglandin production, which normally keeps the ductus arteriosus patent.
- **Clinical note:** While indomethacin is most effective when given to premature infants in the first 10-14 days of life, it remains the **pharmacological agent** for PDA closure, making it the correct answer among the options provided from a pharmacology perspective.
*Prostaglandin E1*
- **Prostaglandin E1 (alprostadil)** is used to *maintain* patency of the ductus arteriosus in **ductal-dependent congenital heart lesions** (e.g., transposition of great arteries, severe coarctation, pulmonary atresia).
- Administering PGE1 would worsen the PDA by preventing its closure, leading to increased left-to-right shunting and potential heart failure.
*Prostaglandin E2*
- Similar to PGE1, **prostaglandin E2** acts to *keep the ductus arteriosus open*, which is the opposite of the desired effect for a symptomatic PDA.
- PGE2 would exacerbate the infant's condition by preventing closure of the PDA.
*Digoxin*
- **Digoxin** is a cardiac glycoside that increases myocardial contractility by inhibiting Na⁺/K⁺-ATPase and is used to treat **congestive heart failure** and control ventricular rate in **atrial fibrillation/flutter**.
- While digoxin may be used for heart failure secondary to a large PDA, it does **not directly close the PDA** and does not address the underlying structural defect.
*Bosentan*
- **Bosentan** is an **endothelin receptor antagonist** used in the treatment of **pulmonary arterial hypertension**.
- It has no role in PDA closure and does not affect the patency of the ductus arteriosus.
Fetal circulation US Medical PG Question 7: A 3175-g (7-lb) male newborn is delivered at 39 weeks' gestation to a 29-year-old primigravid woman following a spontaneous vaginal delivery. Apgar scores are 8 and 9 at 1 and 5 minutes, respectively. Cardiac examination in the delivery room shows a continuous machine-like murmur. An echocardiogram shows a structure with blood flow between the pulmonary artery and the aorta. This structure is most likely a derivate of which of the following?
- A. 4th aortic arch
- B. 1st aortic arch
- C. 6th aortic arch (Correct Answer)
- D. 2nd aortic arch
- E. 3rd aortic arch
Fetal circulation Explanation: ***6th aortic arch***
- The description of a "continuous machine-like murmur" and a structure with blood flow between the pulmonary artery and the aorta is characteristic of a **patent ductus arteriosus (PDA)**.
- The **ductus arteriosus** is a remnant of the **6th aortic arch**, connecting the pulmonary artery to the aorta in fetal life.
*4th aortic arch*
- The **4th aortic arch** contributes to the formation of the **aortic arch** itself on the left side and the proximal **right subclavian artery** on the right.
- Abnormalities of the 4th arch can lead to conditions like **coarctation of the aorta** or **vascular rings**, which do not typically present as a PDA.
*1st aortic arch*
- The **1st aortic arch** largely disappears, but its remnants contribute to the formation of the **maxillary artery** and the **external carotid artery**.
- It is not involved in developmental anomalies of the major vessels between the pulmonary artery and aorta.
*2nd aortic arch*
- The **2nd aortic arch** also largely regresses, but its remnants contribute to the **stapedial artery** and part of the **hyoid artery**.
- It does not play a role in the formation of the ductus arteriosus or other major arteries of the heart.
*3rd aortic arch*
- The **3rd aortic arch** develops into the common carotid arteries and the proximal internal carotid arteries.
- Genetic disorders and malformations involving this arch typically affect the carotid system, not the connection between the pulmonary artery and aorta.
Fetal circulation US Medical PG Question 8: A 28-year-old man comes to the physician because of a persistent tingling sensation in the right side of his face. The sensation began after he underwent an extraction of an impacted molar 2 weeks ago. Examination shows decreased sensation of the skin over the right side of the mandible, chin, and the anterior portion of the tongue. Taste sensation is preserved. The affected nerve exits the skull through which of the following openings?
- A. Foramen rotundum
- B. Hypoglossal canal
- C. Foramen magnum
- D. Foramen ovale (Correct Answer)
- E. Stylomastoid foramen
Fetal circulation Explanation: ***Foramen ovale***
- This patient presents with **paresthesia** in the distribution of branches of the **mandibular nerve (V3)** following molar extraction. The affected areas (mandible, chin, and anterior tongue sensation) indicate injury to the **inferior alveolar nerve** (lower teeth, chin, lower lip) and/or **lingual nerve** (general sensation to anterior 2/3 of tongue).
- Both the **inferior alveolar nerve** and **lingual nerve** are branches of the **mandibular nerve (V3)**, which exits the skull through the **foramen ovale**. These nerves run in close proximity during molar extraction and are commonly injured together.
- Taste sensation is preserved because the **chorda tympani** (taste fibers from CN VII) travels with the lingual nerve but does not exit through foramen ovale.
*Foramen rotundum*
- The **foramen rotundum** transmits the **maxillary nerve (V2)**, which innervates the midface, upper teeth, and palate.
- Injury to this nerve would cause sensory deficits in the upper lip and cheek, not the mandible or chin.
*Hypoglossal canal*
- The **hypoglossal canal** transmits the **hypoglossal nerve (CN XII)**, which is a motor nerve to the intrinsic and extrinsic muscles of the tongue.
- Damage to this nerve would result in **tongue weakness** or **atrophy**, not sensory changes to the face or tongue.
*Foramen magnum*
- The **foramen magnum** is the largest opening in the skull, transmitting the **spinal cord**, vertebral arteries, and accessory nerve (CN XI).
- Damage here would likely involve severe neurological deficits, not isolated sensory loss to the lower face.
*Stylomastoid foramen*
- The **stylomastoid foramen** transmits the **facial nerve (CN VII)**, which is primarily responsible for facial expression and taste sensation to the anterior two-thirds of the tongue via the chorda tympani.
- While CN VII provides taste to the tongue, it does not provide general sensory innervation to the skin of the mandible or chin, and taste is preserved in this patient.
Fetal circulation US Medical PG Question 9: A newborn is rushed to the neonatal ICU after becoming cyanotic shortly after birth. An ultrasound is performed which shows the aorta coming off the right ventricle and lying anterior to the pulmonary artery. The newborn is given prostaglandin E1 and surgery is planned to correct the anatomic defect. Which of the following developmental processes failed to occur in the newborn?
- A. Failure of the membranous ventricular septum to fuse with the muscular interventricular septum
- B. Failure of the septum primum to fuse with the septum secundum
- C. Failure of the aorticopulmonary septum to spiral (Correct Answer)
- D. Failure of the ductus venosus to close
- E. Failure of the ductus arteriosus to close
Fetal circulation Explanation: ***Failure of the aorticopulmonary septum to spiral***
- **Transposition of the great arteries (TGA)**, characterized by the aorta originating from the right ventricle and the pulmonary artery from the left ventricle, results from the **aorticopulmonary septum** failing to spiral properly during embryological development.
- This defect leads to two separate circulatory systems, causing severe **cyanosis** shortly after birth and requiring **prostaglandin E1** to maintain a patent ductus arteriosus for mixing of oxygenated and deoxygenated blood.
- This is a ductal-dependent lesion requiring urgent intervention.
*Failure of the membranous ventricular septum to fuse with the muscular interventricular septum*
- This specific failure leads to a **ventricular septal defect (VSD)**, which allows blood to shunt between ventricles.
- While VSDs can cause cyanosis if large and associated with pulmonary hypertension (Eisenmenger syndrome), the description of **great artery transposition** is not caused by this developmental failure.
*Failure of the septum primum to fuse with the septum secundum*
- This developmental anomaly results in a **patent foramen ovale (PFO)** or an **atrial septal defect (ASD)**.
- These defects typically cause a left-to-right shunt and present with symptoms later in life, not with severe immediate cyanosis.
- In TGA, an ASD may actually be beneficial as it allows some mixing of blood.
*Failure of the ductus venosus to close*
- The **ductus venosus** shunts oxygenated blood from the umbilical vein directly to the inferior vena cava, bypassing the fetal liver during intrauterine life.
- Persistent patency of the ductus venosus after birth is rare and does not cause the severe cyanosis and specific great artery anatomy seen in TGA.
*Failure of the ductus arteriosus to close*
- A **patent ductus arteriosus (PDA)** allows blood to flow from the aorta to the pulmonary artery after birth, which can lead to pulmonary overcirculation.
- In **transposition of the great arteries**, a PDA is actually crucial for survival as it provides a pathway for mixing of oxygenated and deoxygenated blood; maintaining PDA patency with PGE1 is the initial management, not a cause of the condition.
Fetal circulation US Medical PG Question 10: A 28-year-old woman with corrected transposition of the great arteries (L-TGA) who has been asymptomatic presents for preconception counseling. She has a systemic right ventricle supporting systemic circulation and asks about pregnancy risks. Her cardiologist notes mild tricuspid regurgitation. Evaluate the embryologic basis of her condition and synthesize recommendations regarding pregnancy.
- A. Simple transposition with late correction; pregnancy is safe with standard monitoring
- B. Both AV and ventriculoarterial discordance creating physiologically corrected circulation; pregnancy acceptable if systemic RV function normal, but requires high-risk obstetric and cardiology co-management (Correct Answer)
- C. Uncorrected transposition incompatible with pregnancy; recommend adoption
- D. Iatrogenic correction; pregnancy safe as anatomy is normalized
- E. Partial transposition; standard prenatal care is sufficient
Fetal circulation Explanation: ***Both AV and ventriculoarterial discordance creating physiologically corrected circulation; pregnancy acceptable if systemic RV function normal, but requires high-risk obstetric and cardiology co-management***
- **L-TGA** involves **levo-looping** of the heart tube where the **morphologic right ventricle** (RV) supports the systemic circulation due to double discordance (atrioventricular and ventriculoarterial).
- Pregnancy is generally tolerated (maternal WHO class III) if **systemic RV function** is preserved, but requires multidisciplinary care to monitor for **heart failure**, **arrhythmias**, and worsening **tricuspid regurgitation**.
*Simple transposition with late correction; pregnancy is safe with standard monitoring*
- **D-TGA** (simple transposition) requires surgical correction (e.g., Arterial Switch) and has a distinct embryology involving failure of **conotruncal septation** spiral.
- Unlike L-TGA, corrected D-TGA carries different risks and would not be classified as having a "systemic right ventricle" if an **arterial switch** was performed.
*Uncorrected transposition incompatible with pregnancy; recommend adoption*
- **L-TGA** is "congenitally corrected," meaning blood flows in the correct physiological sequence; it is not inherently incompatible with pregnancy if the **systemic RV** is functional.
- Maternal mortality is not high enough to warrant absolute contraindication unless there is severe **RV dysfunction** or NYHA Class III/IV symptoms.
*Iatrogenic correction; pregnancy safe as anatomy is normalized*
- This condition is **congenitally corrected**, meaning the "correction" occurred during **embryogenesis** due to the double mismatch, not through surgery.
- The anatomy is never truly "normalized" because the **tricuspid valve** and **RV** are not designed for high-pressure systemic resistance, making pregnancy a high-risk event.
*Partial transposition; standard prenatal care is sufficient*
- There is no clinical entity termed "partial transposition" in this context; L-TGA is a complete, albeit **physiologically corrected**, malformation.
- Standard prenatal care is insufficient because the hemodynamic stress of pregnancy can trigger **systemic RV failure** or significant **heart block**.
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