Heart development US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Heart development. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Heart development US Medical PG Question 1: A 2-day-old boy is examined on day of discharge from the newborn nursery. He was born at 39 weeks by vaginal delivery to a primigravid mother. The pregnancy and delivery were uncomplicated, and the baby has been stooling, urinating, and feeding normally. Both the patient’s mother and father have no known past medical history and are found to have normal hemoglobin electrophoresis results. Compared to adult hemoglobin, the infant’s predominant hemoglobin is most likely to exhibit which of the following properties?
- A. Decreased affinity for 2,3-bisphosphoglycerate (Correct Answer)
- B. More likely to form hexagonal crystals
- C. More likely to cause red blood cell sickling
- D. Lower affinity for binding oxygen
- E. Increased affinity for 2,3-bisphosphoglycerate
Heart development Explanation: ***Decreased affinity for 2,3-bisphosphoglycerate***
- The baby's predominant hemoglobin is **hemoglobin F (HbF)**, which has a **gamma globin subunit** instead of the beta globin subunit found in adult hemoglobin (HbA).
- The gamma subunit of HbF results in a **reduced binding affinity to 2,3-bisphosphoglycerate (2,3-BPG)**, which in turn leads to a **higher affinity for oxygen** and more efficient oxygen transfer from the mother to the fetus.
*More likely to form hexagonal crystals*
- The formation of **hexagonal crystals** is characteristic of **hemoglobin C (HbC)** disease, a variant of adult hemoglobin, which is not predominant in a newborn.
- The parents have normal hemoglobin electrophoresis, ruling out the inheritance of significant hemoglobinopathies like HbC in a homozygous or compound heterozygous state.
*More likely to cause red blood cell sickling*
- **Red blood cell sickling** is a hallmark of **sickle cell anemia**, caused by hemoglobin S (HbS) which is an abnormal adult hemoglobin, not fetal hemoglobin.
- The parents have normal hemoglobin electrophoresis, meaning they are unlikely to carry the sickle cell trait, and the newborn's predominant HbF actually protects against sickling.
*Lower affinity for binding oxygen*
- HbF in newborns has a **higher affinity for oxygen** than adult hemoglobin (HbA) to facilitate efficient oxygen extraction from maternal blood across the placenta.
- A lower affinity for oxygen would be detrimental for a newborn as it would impair proper tissue oxygenation.
*Increased affinity for 2,3-bisphosphoglycerate*
- HbF has a **decreased affinity for 2,3-BPG**. An increased affinity for 2,3-BPG would lead to a reduction in oxygen binding affinity, which is the opposite of the physiological need in a newborn.
Heart development US Medical PG Question 2: A male neonate is being examined by a pediatrician. His mother informs the doctor that she had a mild fever with rash, muscle pain, and swollen and tender lymph nodes during the second month of gestation. The boy was born at 39 weeks gestation via spontaneous vaginal delivery with no prenatal care. On physical examination, the neonate has normal vital signs. Retinal examination reveals the findings shown in the image. Which of the following congenital heart defects is most likely to be present in this neonate?
- A. Double outlet right ventricle
- B. Atrial septal defect
- C. Patent ductus arteriosus (Correct Answer)
- D. Ventricular septal defect
- E. Tetralogy of Fallot
Heart development Explanation: ***Patent ductus arteriosus***
- This neonate has **congenital rubella syndrome (CRS)** based on maternal symptoms during the first trimester (fever, rash, lymphadenopathy) and the characteristic **"salt and pepper" retinopathy** shown on retinal examination
- **PDA is the most common cardiac defect** associated with CRS, occurring in approximately 50-85% of affected infants
- Other cardiac manifestations of CRS include peripheral pulmonary artery stenosis, but PDA predominates
- The classic triad of CRS includes cardiac defects, ocular abnormalities (cataracts, glaucoma, retinopathy), and sensorineural deafness
*Double outlet right ventricle*
- This is a **conotruncal anomaly** typically presenting with cyanosis in the neonatal period
- Not associated with maternal rubella infection or congenital rubella syndrome
- Would present with abnormal ventricular anatomy and significant hemodynamic compromise
*Atrial septal defect*
- While ASD is a common congenital heart defect, it is **not characteristically associated with CRS**
- Much less frequently linked to maternal viral infections compared to PDA
- Often asymptomatic in the neonatal period and detected later in childhood
*Ventricular septal defect*
- VSD is less commonly associated with **congenital rubella syndrome** compared to PDA
- When present, typically manifests with a holosystolic murmur at the left lower sternal border
- Can occur with maternal infections but is not the predominant cardiac finding in CRS
*Tetralogy of Fallot*
- Consists of four anatomic abnormalities: VSD, pulmonary stenosis, overriding aorta, and right ventricular hypertrophy
- Presents with **cyanosis** ("tet spells") and is not specifically linked to maternal rubella infection
- Not part of the congenital rubella syndrome spectrum
Heart development US Medical PG Question 3: An 8-year-old girl is brought to the physician by her parents for the evaluation of an episode of unconsciousness while at the playground that morning. She was unconscious for about 15 seconds and did not shake, bite her tongue, or lose bowel or bladder control. Her grandfather died suddenly at the age of 29 of an unknown heart condition; her parents are both healthy. An ECG shows sinus rhythm and a QT interval corrected for heart rate (QTc) of 470 milliseconds. Laboratory studies are within normal limits. Which of the following is the most likely additional finding in this patient?
- A. Oblique palpebral fissures
- B. Subvalvular ventricular outflow obstruction murmur
- C. Sensorineural hearing loss (Correct Answer)
- D. Brachial-femoral pulse delay
- E. Skin folds between the mastoid process and acromion
Heart development Explanation: ***Sensorineural hearing loss***
- This patient presents with an episode of syncope, a **prolonged QTc interval** (470 ms; normal <450 ms in prepubertal females, diagnostic threshold >460 ms), and a family history of **sudden cardiac death**, highly suggestive of **Long QT syndrome (LQTS)**.
- **Jervell and Lange-Nielsen syndrome** is a specific form of LQTS (autosomal recessive) characterized by both **prolonged QT interval** and **congenital sensorineural hearing loss**, making this the most likely additional finding.
*Oblique palpebral fissures*
- **Oblique palpebral fissures**, along with epicanthal folds and a flat facial profile, are characteristic features of **Down syndrome (Trisomy 21)**.
- These features are not typically associated with cardiac arrhythmias or Long QT syndrome, and there is no other information to suggest a chromosomal abnormality.
*Subvalvular ventricular outflow obstruction murmur*
- A **subvalvular ventricular outflow obstruction murmur** is indicative of conditions like **hypertrophic obstructive cardiomyopathy (HOCM)**.
- While HOCM can cause syncope and sudden cardiac death, the primary finding in this patient is a **prolonged QTc interval**, which is characteristic of LQTS, not HOCM.
*Brachial-femoral pulse delay*
- A **brachial-femoral pulse delay** is the classic physical exam finding for **coarctation of the aorta**, a congenital narrowing of the aorta.
- There is no clinical information to suggest coarctation, and it does not explain the prolonged QTc interval and family history of sudden cardiac death.
*Skin folds between the mastoid process and acromion*
- **Skin folds between the mastoid process and acromion** (webbed neck or pterygium colli) are a classic sign of **Turner syndrome (XO)** or **Noonan syndrome**.
- These conditions are not primarily associated with a prolonged QTc interval and exert their cardiac effects through structural defects like coarctation or pulmonary stenosis, not typically primary arrhythmias.
Heart development US Medical PG Question 4: 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
Heart development 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.
Heart development US Medical PG Question 5: A 56-year-old man is brought to the emergency department 25 minutes after the sudden onset of severe pain in the middle of his chest. He describes the pain as tearing in quality; it radiates to his jaw. He has hypertension. He has smoked one pack of cigarettes daily for the 25 years. Current medications include enalapril. His blood pressure is 154/95 mm Hg in his right arm and 181/105 mm Hg in his left arm. A CT scan of the chest is shown. The structure indicated by the arrow is a derivative of which of the following?
- A. Right horn of sinus venosus
- B. Primitive atrium
- C. Right common cardinal vein
- D. Truncus arteriosus (Correct Answer)
- E. Bulbus cordis
Heart development Explanation: ***Truncus arteriosus***
- This clinical scenario describes an **aortic dissection**, suggested by the sudden onset of **tearing chest pain radiating to the jaw**, significant **blood pressure differential** between arms, and presenting in a patient with **hypertension and smoking history**.
- The image likely shows a dilated aorta or an aortic dissection. The **truncus arteriosus** is the embryonic precursor to the **ascending aorta** and the **pulmonary trunk**, making it the correct derivative for the affected structure.
*Right horn of sinus venosus*
- The **right horn of the sinus venosus** primarily contributes to the formation of the **smooth-walled part of the right atrium** (sinus venarum).
- It does not give rise to the aorta, which is the structure involved in the described pathology.
*Primitive atrium*
- The **primitive atrium** develops into the **trabeculated parts** of both the **right and left atria** (atrial appendages).
- It is not involved in the formation of the great arteries like the aorta.
*Right common cardinal vein*
- The **right common cardinal vein** contributes to the formation of the **superior vena cava**.
- It is not a developmental source for the aorta.
*Bulbus cordis*
- The **bulbus cordis** gives rise to the **conus arteriosus** (infundibulum) of the right ventricle, the **aortic vestibule** of the left ventricle, and part of the **right ventricle**.
- While it is a component of the outflow tract, the primary structure from which the ascending aorta develops is the truncus arteriosus.
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