Ventricular septation US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Ventricular septation. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Ventricular septation US Medical PG Question 1: A 27-year-old G2P1 female gives birth to a baby girl at 33 weeks gestation. The child is somnolent with notable difficulty breathing. Pulse pressure is widened. She is profusely cyanotic. Auscultation is notable for a loud single S2. An echocardiogram demonstrates an enlarged heart and further studies show blood from the left ventricle entering the pulmonary circulation as well as the systemic circulation. Which of the following processes was most likely abnormal in this patient?
- A. Formation of the interatrial septum
- B. Formation of the aorticopulmonary septum (Correct Answer)
- C. Closure of an aorticopulmonary shunt
- D. Formation of an atrioventricular valve
- E. Spiraling of the truncal and bulbar ridges
Ventricular septation Explanation: ***Formation of the aorticopulmonary septum***
- The symptoms described, such as **cyanosis**, widened pulse pressure, and a loud single S2, are classic signs of **truncus arteriosus**, a congenital heart defect.
- Truncus arteriosus results from the **failure of the aorticopulmonary septum to form**, leading to a single great artery overriding a ventricular septal defect, allowing blood to shunt from the left ventricle into both pulmonary and systemic circulations.
*Formation of the interatrial septum*
- Defects in the formation of the interatrial septum lead to **atrial septal defects (ASDs)**, which typically cause a left-to-right shunt and are associated with a fixed split S2 and potential for pulmonary hypertension, but not the severe cyanosis and single S2 seen here.
- While an enlarged heart can occur, the primary problem in ASDs is not the mixing of ventricular blood into both circulations in the manner described.
*Closure of an aorticopulmonary shunt*
- An aorticopulmonary shunt refers to a **patent ductus arteriosus (PDA)**, where the ductus arteriosus fails to close after birth. This typically causes a continuous "machine-like" murmur and pulmonary overcirculation, but not severe cyanosis unless associated with other complex lesions.
- The described findings of a single S2, widened pulse pressure, and severe cyanosis point away from an isolated PDA.
*Formation of an atrioventricular valve*
- Abnormalities in atrioventricular valve formation can lead to conditions like **tricuspid or mitral atresia** or **Ebstein's anomaly**. These often present with cyanosis and heart failure, but the specific description of blood from the left ventricle entering both pulmonary and systemic circulations, along with a single great artery and single S2, does not fit isolated AV valve malformations.
- The characteristic presentation strongly points to a truncal anomaly rather than an isolated AV valve issue.
*Spiraling of the truncal and bulbar ridges*
- Failure of the truncal and bulbar ridges to spiral correctly leads to **transposition of the great arteries (TGA)** or **tetralogy of Fallot**. TGA results in two separate circulations and severe cyanosis, while Tetralogy presents with a VSD, pulmonary stenosis, overriding aorta, and right ventricular hypertrophy.
- While spiraling is part of early septation, the specific findings in the case (single S2, widened pulse pressure, and blood shunting from left ventricle to both circulations) are more specifically indicative of truncus arteriosus (failure of septum formation rather than spiraling) than TGA or Tetralogy.
Ventricular septation US Medical PG Question 2: A 9-year-old boy is brought to the clinic by his parents for an annual wellness examination. He is a relatively healthy boy who was born at term via vaginal delivery. He is meeting his developmental milestones and growth curves and is up-to-date on his immunizations. The father complains that he is picky with his food and would rather eat pizza. The patient denies any trouble at school, fevers, pain, or other concerns. A physical examination demonstrates a healthy boy with a grade 3 midsystolic ejection murmur at the second intercostal space that does not disappear when he sits up. What is the most likely explanation for this patient’s findings?
- A. Physiologic conditions outside the heart
- B. Inflammation of the visceral and parietal pericardium
- C. Failure of the septum primum to fuse with the endocardial cushions
- D. Defect of the septum secundum (Correct Answer)
- E. Prolonged patency of the ductus arteriosus
Ventricular septation Explanation: **Defect of the septum secundum**
- A **grade 3 midsystolic ejection murmur** that does not disappear when sitting up in an otherwise healthy 9-year-old child is characteristic of an **atrial septal defect (ASD)**.
- Defects of the **septum secundum** are the most common type of ASD, allowing blood to shunt from the left to the right atrium, leading to increased pulmonary blood flow and the generation of such a murmur.
*Physiologic conditions outside the heart*
- A **physiologic murmur** (also known as a Still's murmur) is typically described as a grade 1-2 innocent murmur that often disappears or changes with positional changes (e.g., sitting up).
- The **grade 3 intensity** and persistence with positional changes make a common physiologic murmur less likely in this case.
*Inflammation of the visceral and parietal pericardium*
- **Pericarditis** typically presents with chest pain that can worsen with inspiration and lying down, and a characteristic **pericardial friction rub**, not a midsystolic ejection murmur.
- This condition is unlikely in an otherwise healthy child with no other systemic symptoms or signs of inflammation.
*Failure of the septum primum to fuse with the endocardial cushions*
- This describes a **primum ASD**, which is a type of ASD often associated with **endocardial cushion defects** and other congenital heart anomalies, such as cleft mitral valve.
- While it is a type of ASD, the description typically refers to the larger, more clinically significant defects and doesn't explicitly refer to the most common type of ASD, which is the septum secundum defect.
*Prolonged patency of the ductus arteriosus*
- A **patent ductus arteriosus (PDA)** produces a **continuous, machine-like murmur** that is typically heard best at the left upper sternal border.
- The murmur described in the patient is a **midsystolic ejection murmur**, which is distinct from the continuous murmur of a PDA.
Ventricular septation US Medical PG Question 3: 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
Ventricular septation 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.
Ventricular septation US Medical PG Question 4: Cardiac surgery is consulted on a newborn with a large ventricular septal defect. The child has poor weight gain and feeding difficulties. He requires furosemide and captopril to avoid dyspnea. On physical examination his temperature is 36.9°C (98.4°F), pulse rate is 158/min, respiratory rate is 30/min, and blood pressure is 94/62 mm Hg. Chest auscultation reveals a holosystolic murmur along the left lower sternal border and a mid-diastolic low-pitched rumble at the apex. Abdominal examination reveals the presence of hepatomegaly. An echocardiogram confirms a diagnosis of a membranous VSD while hemodynamic studies show a Qp:Qs ratio of 2.8:1. Which of the following is the best management option?
- A. Continue medical treatment and provide reassurance about spontaneous closure of the defect
- B. Hybrid surgery using both transcatheter device and surgical repair
- C. Transcatheter occlusion of the defect
- D. Surgical closure of the defect (Correct Answer)
- E. Addition of digoxin to the current medical regimen with regular follow-up until spontaneous closure occurs
Ventricular septation Explanation: ***Surgical closure of the defect***
* This newborn exhibits **symptoms of severe heart failure** due to a large VSD, including poor weight gain, feeding difficulties, and hepatomegaly, despite maximal medical therapy.
* A **Qp:Qs ratio of 2.8:1** indicates a significant left-to-right shunt, which, combined with the clinical picture, necessitates **surgical intervention** to prevent irreversible pulmonary vascular disease and improve prognosis.
*Continue medical treatment and provide reassurance about spontaneous closure of the defect*
* While some small VSDs close spontaneously, this child has a **large VSD** with **symptoms of severe heart failure** that require aggressive medical management (furosemide, captopril) and show no signs of improvement.
* **Reassurance of spontaneous closure** is inappropriate given the significant hemodynamic compromise and the potential for long-term complications without surgical intervention.
*Hybrid surgery using both transcatheter device and surgical repair*
* Hybrid approaches are typically reserved for **complex congenital heart defects** or specific anatomical challenges where a purely transcatheter or open surgical approach is not feasible or optimal.
* For a large membranous VSD requiring definitive closure, a **direct surgical approach** is generally preferred and more effective.
*Transcatheter occlusion of the defect*
* **Transcatheter occlusion** is generally indicated for **smaller, hemodynamically insignificant VSDs** or in specific anatomical situations, and it is usually performed in older children.
* A **large membranous VSD** with significant shunt and symptoms of heart failure is typically **not amenable to transcatheter closure** due to the size and location of the defect, and the risk of complications.
*Addition of digoxin to the current medical regimen with regular follow-up until spontaneous closure occurs*
* The child is already on **maximal medical therapy** (furosemide, captopril) and still experiencing severe symptoms, indicating medicine alone is insufficient.
* While digoxin can improve myocardial contractility, it is unlikely to significantly alter the natural history or **resolve the large shunt** in a VSD of this magnitude, and waiting for spontaneous closure would be detrimental.
Ventricular septation US Medical PG Question 5: During development, a fetus is found to have incomplete fusion of the neural tube. Which of the following structures would most likely be affected by this developmental defect?
- A. Notochord
- B. Somites
- C. Vertebral bodies
- D. Spinal cord and meninges (Correct Answer)
Ventricular septation Explanation: ***Spinal cord and meninges***
- Incomplete fusion of the neural tube directly results in defects of the **neural tube closure**, which include the formation of the **spinal cord** and its protective coverings, the **meninges**. [1, 2]
- Conditions like **spina bifida** (meningocele, myelomeningocele) are direct consequences of these fusion failures, exposing or abnormally developing the spinal cord and meninges. [1, 2]
*Notochord*
- The **notochord** is a transient embryonic structure that induces the formation of the neural tube by signaling to the overlying ectoderm; it is not directly formed by the neural tube itself.
- While it plays a critical role in neural tube development, its own structural integrity is typically not primarily affected by neural tube fusion defects.
*Somites*
- **Somites** are blocks of paraxial mesoderm that differentiate into sclerotome (vertebrae and ribs), myotome (skeletal muscle), and dermatome (dermis of the skin).
- While somite development is closely coordinated with neural tube formation, incomplete neural tube fusion primarily affects the neural structures themselves, not the somites directly.
*Vertebral bodies*
- **Vertebral bodies** develop from the sclerotome portion of the somites, which migrate to surround the neural tube and notochord.
- While vertebral defects can be associated with severe neural tube defects (e.g., in spina bifida, the vertebral arches may fail to close), the primary defect of incomplete neural tube fusion directly impacts the neural tissue (spinal cord and meninges), with skeletal defects being secondary or associated. [1, 2]
Ventricular septation US Medical PG Question 6: A 2-year-old boy is brought to a pediatrician because his parents have noticed that he seems to be getting tired very easily at home. Specifically, they have noticed that he is often panting for breath after walking around the house for a few minutes and that he needs to take naps fairly often throughout the day. He has otherwise been well, and his parents do not recall any recent infections. He was born at home, and his mom did not receive any prenatal care prior to birth. Physical exam reveals a high-pitched, harsh, holosystolic murmur that is best heard at the lower left sternal border. No cyanosis is observed. Which of the following oxygen tension profiles would most likely be seen in this patient? (LV = left ventricle, RV = right ventricle, and SC = systemic circulation).
- A. LV: normal, RV: normal, SC: normal
- B. LV: normal, RV: increased, SC: normal (Correct Answer)
- C. LV: decreased, RV: increased, SC: decreased
- D. LV: decreased, RV: normal, SC: decreased
- E. LV: normal, RV: normal, SC: decreased
Ventricular septation Explanation: ***LV: normal, RV: increased, SC: normal***
- The patient's presentation with easy fatigability, dyspnea on exertion, and a **holosystolic murmur** at the **lower left sternal border** strongly suggests a **ventricular septal defect (VSD)**. These symptoms result from a **left-to-right shunt**, leading to increased blood flow and pressure in the **right ventricle (RV)** and pulmonary circulation.
- In a VSD, highly oxygenated blood from the **left ventricle (LV)** shunts into the RV. This increases the **oxygen tension** in the RV, while the LV and systemic circulation (SC) typically maintain normal oxygen tension if the shunt is not so large that it causes **pulmonary hypertension** with **Eisenmenger syndrome**.
*LV: normal, RV: normal, SC: normal*
- This profile would indicate a **normal cardiovascular system** without any significant shunting or cardiac anomaly.
- It does not align with the patient's symptoms of easy fatigability, dyspnea, and the presence of a pathological murmur.
*LV: decreased, RV: increased, SC: decreased*
- A **decreased oxygen tension in the left ventricle** and **systemic circulation** typically indicates a **right-to-left shunt** or severe **pulmonary disease**, often associated with **cyanosis**, which is noted as absent in this patient.
- While RV oxygen tension *could* be increased in some complex congenital heart diseases with right-to-left shunting (e.g., mixing lesions), the overall profile does not fit the characteristic presentation of a VSD without cyanosis.
*LV: decreased, RV: normal, SC: decreased*
- This profile with **decreased oxygen tension in the left ventricle** and **systemic circulation** suggests a condition where oxygenated blood supply to the systemic circulation is compromised, such as severe **left ventricular dysfunction** or a **right-to-left shunt**.
- A **normal RV oxygen tension** without **cyanosis** makes this unlikely in the context of the patient's symptoms.
*LV: normal, RV: normal, SC: decreased*
- A **decreased oxygen tension in the systemic circulation** with **normal LV and RV oxygen tension** is inconsistent with a **VSD**.
- This profile might be observed in conditions like severe **anemia** or **hypoxia** without a primary cardiac shunt.
Ventricular septation US Medical PG Question 7: A 5-day-old boy is brought to the emergency department by his mother because of a 2-day history of difficulty feeding and multiple episodes of his lips turning blue. He was born at home via spontaneous vaginal delivery and Apgar scores were 7 and 8 at 1 and 5 minutes, respectively. Physical examination shows grunting and moderate intercostal and subcostal retractions. Echocardiography shows a single vessel exiting from the heart. Which of the following is the most likely underlying cause of this patient's condition?
- A. Abnormal placement of the infundibular septum
- B. Absent fusion of septum primum and septum secundum
- C. Failure of neural crest cell migration (Correct Answer)
- D. Insufficient growth of endocardial cushions
- E. Abnormal cardiac looping
Ventricular septation Explanation: ***Failure of neural crest cell migration***
- The echocardiography finding of a **single vessel exiting the heart** is characteristic of **truncus arteriosus**, a congenital heart defect.
- This condition arises from the **failure of neural crest cells** to migrate properly and spiralize the **aortopulmonary septum**, which normally divides the truncus arteriosus into the aorta and pulmonary artery.
*Abnormal placement of the infundibular septum*
- Abnormal placement of the infundibular septum is typically associated with **Tetralogy of Fallot**, leading to an overriding aorta, pulmonary stenosis, ventricular septal defect, and right ventricular hypertrophy.
- While Tetralogy of Fallot is a cyanotic heart disease, it presents with a **bifurcated outflow tract** not a single great vessel.
*Absent fusion of septum primum and septum secundum*
- The absent fusion of the **septum primum** and **septum secundum** results in a **patent foramen ovale** or an **atrial septal defect**.
- These defects primarily cause left-to-right shunting, leading to volume overload in the right heart, but do not explain the presence of a single great vessel.
*Insufficient growth of endocardial cushions*
- Insufficient growth of the **endocardial cushions** can lead to **atrioventricular septal defects** and certain types of **ventricular septal defects**.
- These conditions involve issues with valve formation and septal development but do not directly cause a single great vessel to exit the heart.
*Abnormal cardiac looping*
- Abnormal cardiac looping is associated with conditions like **dextrocardia** or **transposition of the great arteries**.
- While **transposition of the great arteries** also causes cyanosis, it involves **two great vessels** that are improperly connected, not a single great vessel.
Ventricular septation US Medical PG Question 8: Shortly after delivery, a female newborn develops bluish discoloration of the lips, fingers, and toes. She was born at term to a 38-year-old primigravid woman. Pregnancy was complicated by maternal diabetes mellitus. Pulse oximetry on room air shows an oxygen saturation of 81%. Echocardiography shows immediate bifurcation of the vessel arising from the left ventricle; the vessel emerging from the right ventricle gives out coronary, head, and neck vessels. An abnormality in which of the following developmental processes most likely accounts for this patient's condition?
- A. Alignment of infundibular septum
- B. Fusion of endocardial cushion
- C. Spiraling of aorticopulmonary septum (Correct Answer)
- D. Separation of tricuspid valve tissue from myocardium
- E. Division of aorta and pulmonary artery
Ventricular septation Explanation: ***Spiraling of aorticopulmonary septum***
- The description of a vessel arising from the left ventricle that immediately bifurcates (pulmonary artery) and a vessel from the right ventricle that gives off coronary, head, and neck vessels (aorta) is characteristic of **transposition of the great arteries (TGA)**.
- TGA results from a failure of the **aorticopulmonary septum** to spiral during embryological development, leading to the aorta originating from the right ventricle and the pulmonary artery from the left ventricle.
*Alignment of infundibular septum*
- Abnormal alignment of the infundibular septum is associated with conditions like **tetralogy of Fallot**, which involves a maligned interventricular septum and a shifted aorta, presenting with a different set of echocardiographic findings.
- While also a **cyanotic heart defect**, tetralogy of Fallot's anatomy (e.g., interventricular septal defect, pulmonary stenosis) differs from the described TGA.
*Fusion of endocardial cushion*
- Failure of fusion of the **endocardial cushions** leads to **atrioventricular septal defects**, which involve defects in both the atria and ventricular septa, and often affect the mitral and tricuspid valves.
- These defects typically present with heart failure symptoms and different echocardiographic findings than those described for TGA.
*Separation of tricuspid valve tissue from myocardium*
- An abnormality in the separation of tricuspid valve tissue from the myocardium is the cause of **Ebstein anomaly**, where the tricuspid valve leaflets are displaced downwards into the right ventricle, leading to tricuspid regurgitation.
- Ebstein anomaly is characterized by right atrial enlargement and a largely functional right ventricle, leading to issues with right heart output but not the great artery transposition described.
*Division of aorta and pulmonary artery*
- The division of the truncus arteriosus into the aorta and pulmonary artery is a normal developmental process, which when complete usually produces the correct great artery connections. However, the exact arrangement of these vessels is determined by the **spiraling of the aorticopulmonary septum**, not just the division itself.
- Failure of this division, resulting in a **persistent truncus arteriosus**, would present as a single great artery arising from both ventricles, which is distinct from the two separate but transposed vessels seen in TGA.
Ventricular septation US Medical PG Question 9: 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
Ventricular septation 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**.
Ventricular septation US Medical PG Question 10: A newborn presents with severe cyanosis, hypoplastic right ventricle, pulmonary atresia, and an intact ventricular septum. The cardiologist notes this differs from tetralogy of Fallot despite both having pulmonary atresia. The neonatologist questions whether to maintain ductal patency or pursue immediate surgical intervention. Evaluate the embryologic differences and synthesize the optimal management strategy.
- A. Both result from infundibular deviation; maintain ductus with prostaglandins and perform staged repair
- B. Pulmonary atresia with intact septum results from primary valve failure; urgent surgical valvotomy or perforation
- C. Both are conotruncal defects; immediate complete repair is preferred
- D. Pulmonary atresia with intact septum results from primary valve failure; maintain ductus and evaluate RV-dependent coronary circulation before intervention (Correct Answer)
- E. Different embryologic timing but similar management; prostaglandin with elective repair at 6 months
Ventricular septation Explanation: ***Pulmonary atresia with intact septum results from primary valve failure; maintain ductus and evaluate RV-dependent coronary circulation before intervention***
- Unlike Tetralogy of Fallot which is a **conotruncal defect**, Pulmonary Atresia with Intact Ventricular Septum (PA-IVS) is a primary **valvular failure** resulting in secondary right ventricular hypoplasia.
- It is critical to identify **RV-dependent coronary circulation** via sinusoids before any intervention, as decompressing the right ventricle in these patients can lead to fatal **myocardial ischemia**.
*Both result from infundibular deviation; maintain ductus with prostaglandins and perform staged repair*
- Only Tetralogy of Fallot results from the **anterior deviation** of the infundibular septum, whereas PA-IVS is characterized by a lack of communication between the RV and pulmonary artery without a VSD.
- While prostaglandins are used in both for **ductal patency**, the underlying embryologic mechanism and surgical risks differ significantly.
*Pulmonary atresia with intact septum results from primary valve failure; urgent surgical valvotomy or perforation*
- Although it is a primary valve failure, **urgent valvotomy** is contraindicated if there is **RV-dependent coronary circulation**.
- Releasing the high pressure in the RV can cause reversal of flow in **coronary sinusoids**, leading to sudden cardiac death.
*Both are conotruncal defects; immediate complete repair is preferred*
- PA-IVS is not a **conotruncal defect** because it lacks the malalignment of the outflow tract septum typically seen in Tetralogy or Transposition.
- **Complete repair** is often impossible in the neonatal period due to the **hypoplastic right ventricle** and anatomical constraints.
*Different embryologic timing but similar management; prostaglandin with elective repair at 6 months*
- Management is not similar because PA-IVS requires immediate mapping of the **coronary arteries** and high risk of **RV-dependent** flow.
- Elective repair at 6 months is often too late for stable management; these neonates require **prostaglandin (PGE1)** and early palliative or corrective intervention within the first weeks of life.
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