Epidemiology

Etiology

Associations (High-Yield)
- Turner Syndrome (45,XO): High association (up to 15% of cases).
- Bicuspid Aortic Valve: Present in >50% of patients.
- Intracranial Berry Aneurysms (risk of subarachnoid hemorrhage).

Narrowing (stenosis) of the aortic lumen.
Infantile Type (Preductal): Stenosis proximal to the ductus arteriosus. Dependent on patent ductus arteriosus (PDA) for systemic perfusion.
Adult Type (Postductal): Stenosis distal to the ductus arteriosus (distal to left subclavian).

Neonatal (Pre-ductal):
- Heart failure, poor feeding, and shock as the PDA closes (typically day 3-10 of life).
- Differential cyanosis (cyanosis of the lower body, normal upper body).
Adult/Post-pediatric (Post-ductal):
- Asymptomatic HTN: Often incidental finding.
- UE vs. LE BP Differential: Systolic BP higher in arms than legs.
- Brachial-femoral pulse delay.
- Symptoms: Epistaxis, headaches (due to UE HTN), or LE claudication (due to LE ischemia).
- Auscultation
  - Midsystolic murmur heard best over the left interscapular area.
  - Continuous murmur in the left infraclavicular region and interscapular region c
    - Collateral Circulation: To bypass the obstruction, blood flows through enlarged collateral vessels, specifically the intercostal arteries.

Initial Clinical Step: BP measurement in all four extremities.
Best Initial Imaging: Echocardiogram (TTE); visualizes the shelf-like narrowing and confirms pressure gradient.
Confirmatory/Gold Standard: Cardiac Catheterization (used if TTE is non-diagnostic or for pre-intervention planning).
CXR findings:
- “3” Sign: Pre- and post-stenotic dilation of the aorta.
- Rib Notching: Erosion of the inferior surface of the 3rd–8th ribs by dilated intercostal collateral arteries. c
ECG: LVH (due to increased afterload).