Source / episode info
- **Episode:**401
- **Title:**Divine Intervention Episode 401 – USMLE Step 2/3 Rapid Review Series 78
- **Published:**2022-07-07
- Source:Episode page
One-liner
This episode provides a high-yield review of pediatric cardiology concepts including VSD physiology and cardiac murmurs (fixed vs. physiologic splits), alongside the detailed workup and management of pyloric stenosis, emphasizing associated metabolic derangements.
High-yield summary
- VSD Murmur Timing: A Ventricular Septal Defect (VSD) murmur may not be appreciated at birth but typically becomes louder over weeks to months of life due to increased pressure gradient between the left and right ventricles as pulmonary vascular resistance drops.
- Fixed Split S2: An Atrial Septal Defect (ASD) causes a fixed, wide split of the second heart sound (S2) because blood flow from the left atrium to the right atrium is constant regardless of respiratory cycle (inspiration/expiration).
- Right-Sided Murmur: A cardiac murmur that increases in intensity with inspiration suggests increased venous return and preload to the right side of the heart, consistent with a Y-pattern.
- Pyloric Stenosis Presentation: Classic signs include non-bilious, projectile vomiting and an palpable "olive-like mass" in the epigastrium. The diagnosis is best confirmed by ultrasound.
- Pyloric Stenosis Electrolytes: Vomiting gastric acid leads to a metabolic alkalosis and hypochloremia. Volume depletion activates RAAS, leading to potassium wasting (hypokalemia). Treatment must correct these electrolyte imbalances before surgery.
Learning objectives
- Describe the physiological changes in cardiac murmurs related to respiratory cycle and shunt location.
- Identify the classic signs, physical exam findings, and diagnostic imaging for pyloric stenosis.
- Explain the pathophysiology of metabolic alkalosis, hypochloremia, and hypokalemia resulting from gastric acid loss.
- Differentiate between fixed and physiologic splits of S2 heart sound.
- Outline the critical sequence of management for pyloric stenosis (electrolytes -> surgery).
Board exam buzzwords