A 43-year-old woman presents to her primary care provider with shortness of breath. She reports a 4-month history of progressively worsening difficulty breathing with associated occasional chest pain. She is a long-distance runner but has had trouble running recently due to her breathing difficulties. Her past medical history is notable for well-controlled hypertension for which she takes hydrochlorothiazide. She had a tibial osteosarcoma lesion with pulmonary metastases as a child and successfully underwent chemotherapy and surgical resection. She has a 10 pack-year smoking history but quit 15 years ago. She drinks a glass of wine 3 times per week. Her temperature is 98.6°F (37°C), blood pressure is 140/85 mmHg, pulse is 82/min, and respirations are 18/min. On exam, she has increased work of breathing with a normal S1 and loud P2. An echocardiogram in this patient would most likely reveal which of the following?

Right ventricular hypertrophy with a dilated pulmonary artery

Biventricular dilatation with a decreased ejection fraction

Left ventricular dilatation with an incompetent aortic valve

Left atrial dilatation with mitral valve stenosis

Left ventricular hypertrophy with a bicuspid aortic valve

A 15-month-old boy is brought to the pediatrician for immunizations and assessment. His parents report that he is eating well and produces several wet diapers every day. He is occasionally fussy, but overall a happy and curious child. The boy was born at 39 weeks gestation via spontaneous vaginal delivery. On physical examination his vital signs are stable. His weight and height are above the 85th percentile for his age and sex. On chest auscultation, the pediatrician detects a loud harsh holosystolic murmur over the left lower sternal border. The first and second heart sounds are normal. An echocardiogram confirms the diagnosis of the muscular ventricular septal defect without pulmonary hypertension. Which of the following is the best management strategy for this patient?

Reassurance of the parents and regular follow-up

Surgical closure of the defect using cardiopulmonary bypass

Oral digoxin and regular follow-up

Antibiotic prophylaxis against infective endocarditis

Transcatheter occlusion closure of the defect

A 2-year-old child is brought to the emergency department with rapid breathing and a severe cyanotic appearance of his lips, fingers, and toes. He is known to have occasional episodes of mild cyanosis, especially when he is extremely agitated. This is the worst episode of this child’s life, according to his parents. He was born with an APGAR score of 8 via a normal vaginal delivery. His development is considered delayed compared to children of his age. History is significant for frequent squatting after strenuous activity. On auscultation, there is evidence of a systolic ejection murmur at the left sternal border. On examination, his oxygen saturation is 71%, blood pressure is 81/64 mm Hg, respirations are 42/min, pulse is 129/min, and temperature is 36.7°C (98.0°F). Which of the following will most likely be seen on chest x-ray (CXR)?

Increased pulmonary vascular markings

Cardiomegaly with globular heart

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?

Failure of neural crest cell migration

Abnormal placement of the infundibular septum

Absent fusion of septum primum and septum secundum

Insufficient growth of endocardial cushions

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?

Spiraling of aorticopulmonary septum

Alignment of infundibular septum

Separation of tricuspid valve tissue from myocardium

Division of aorta and pulmonary artery

Congenital heart defects for USMLE Step 2 CK: High-Yield Anatomy Lessons

Cardiac Embryology - The Heart's Blueprint

Week 3: Heart development begins from the visceral mesoderm, forming the primary heart field.
Week 4: Lateral folding fuses paired heart tubes into a single primitive heart tube. This tube then undergoes dextral looping to establish right-left orientation.

Embryonic heart tube development and looping

Key Derivatives:
- Truncus Arteriosus → Trunks (Aorta/Pulmonary)
- Bulbus Cordis → Smooth parts of ventricles (outflow tracts)
- Primitive Ventricle → Trabeculated parts of ventricles
- Primitive Atrium → Trabeculated parts of atria
- Sinus Venosus → Smooth RA, Coronary Sinus

⭐ Dextrocardia, where the heart apex points right, results from abnormal heart looping. It's often associated with Kartagener syndrome (primary ciliary dyskinesia).

Acyanotic Defects - Shifty Lefties

Initial left-to-right (L→R) shunts that increase pulmonary blood flow. Patients are pink. Chronic L→R shunting can lead to pulmonary hypertension, shunt reversal (R→L), and late cyanosis (Eisenmenger syndrome).

Ventricular Septal Defect (VSD)
- Most common congenital heart defect.
- Harsh, holosystolic murmur at lower left sternal border.
Atrial Septal Defect (ASD)
- Loud S1, wide, fixed split S2.
- Ostium secundum type is most common.
Patent Ductus Arteriosus (PDA)
- Continuous, machine-like murmur.
- Associated with congenital rubella.
- Maintained by PGE₂; closed with indomethacin.

Anatomy of Atrial and Ventricular Septal Defects

⭐ Eisenmenger Syndrome: The irreversible point where a long-standing L→R shunt reverses to a R→L shunt due to severe pulmonary hypertension, causing late-onset cyanosis, clubbing, and polycythemia.

Cyanotic Defects - True Blue Trouble

Presents with early cyanosis (R→L shunts). 📌 Mnemonic: The 5 T's.

1. Truncus Arteriosus:
- Single arterial trunk overrides a VSD, supplying coronary, pulmonary, & systemic circulation.
2. Transposition of Great Arteries (TGA):
- Aorta from RV, pulmonary artery from LV. Incompatible with life unless a shunt (VSD, PDA, ASD) exists.
- Associated with maternal diabetes. CXR: "egg on a string."
3. Tricuspid Atresia:
- Absence of tricuspid valve & hypoplastic RV. Requires both ASD & VSD for viability.
4. Tetralogy of Fallot (TOF):
- Most common cyanotic CHD. 📌 PROVe: Pulmonary stenosis, RVH, Overriding aorta, VSD.
- CXR: "boot-shaped" heart.
⭐ "Tet spells" (cyanosis, syncope) are caused by crying/feeding, which ↑ pulmonary vascular resistance. Squatting ↑ SVR, reversing the shunt (L→R), improving cyanosis.
5. Total Anomalous Pulmonary Venous Return (TAPVR):
- Pulmonary veins drain into R. heart circulation (e.g., SVC).
- CXR: "snowman" appearance.

Tricuspid Atresia: Normal vs. Defective Tricuspid Valve

Obstructive Lesions - Blockage Blues

Aortic Stenosis (AS): Narrowing of aortic valve → left ventricular hypertrophy (LVH). Presents with Syncope, Angina, and Dyspnea on exertion (📌 SAD).
Coarctation of the Aorta (CoA): Constriction, typically near ductus arteriosus. Causes ↑ upper extremity BP and ↓ lower extremity BP. Look for rib notching on CXR (collateral flow).
- Associated with Turner syndrome and bicuspid aortic valves.
Pulmonary Stenosis (PS): Right ventricular outflow tract obstruction → RVH. Often associated with Noonan syndrome.

⭐ In Coarctation, brachial-femoral pulse delay and a blood pressure discrepancy of >20 mmHg between upper and lower extremities are key diagnostic clues.

High‑Yield Points - ⚡ Biggest Takeaways

Ventricular septal defect (VSD) is the most common congenital heart defect, often asymptomatic.

Atrial septal defect (ASD) is characterized by a fixed, split S2 on auscultation.

Patent ductus arteriosus (PDA) presents with a continuous, machine-like murmur.

Tetralogy of Fallot is the most common cyanotic defect; remember PROVe.

Transposition of the great arteries requires a shunt for viability; common in infants of diabetic mothers.

Coarctation of the aorta is associated with Turner syndrome and discrepant blood pressure between the arms and legs.

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