Aortic stenosis

Aortic Stenosis (AS): aortic valve narrows, restricting blood flow from the heart’s left ventricle. Presents with “SAD” symptoms. Syncope, Angina, Dyspnea.

Causes:

• Calcific degeneration (elderly)

• Congenital bicuspid valve (younger patients)

• Rheumatic disease (less common)

Key Concept:

Remember the Law of LaPlace:

❤️ Cardiac Application (Left Ventricle)

$$T = \frac{P \cdot r}{2h}$$

• h = wall thickness, P = pressure, r = radius, T = wall tension

Key Insight:

• Increased radius (dilated ventricle) → ↑ wall tension → ↑ oxygen demand
  • Factors of myocardial oxygen demand (3): HR, Wall tension, contractility
• Increased wall thickness (hypertrophy) → ↓ wall tension

💡 Aortic stenosis connection:

• LV hypertrophy develops to reduce wall stress
• But → worsens diastolic compliance

Severity	Aortic Valve Area (cm²)	Peak Velocity (m/s)	Mean Gradient (mmHg)
Normal	3.0 – 4.0	< 2.0	< 10
Mild	> 1.5	< 3.0	< 20
Moderate	1.0 – 1.5	3.0 – 4.0	20 – 40
Severe	< 1.0	> 4.0	> 40
Critical	< 0.7	Often > 5.0	Often > 60

Anesthesia Approach:

1. Preload — Maintain

• These patients are preload dependent
• Avoid hypovolemia
• Be cautious with neuraxial techniques

2. Afterload — Maintain or Slightly Increase

• Coronary perfusion depends on diastolic pressure
  • Coronary perfusion pressure = Aortic Diastolic pressure – LVEDP (usually 60-80 mmHg)
• Hypotension = ischemia → rapid decompensation

3. Heart Rate — Slow to Normal

• Ideal: ~60–80 bpm
• Tachycardia → ↓ diastolic filling + ↓ coronary perfusion
• Bradycardia (too slow) → ↓ cardiac output

4. Rhythm — Sinus Rhythm is Critical

• Loss of atrial kick (e.g., afib) can cause collapse

5. Contractility — Maintain

• Avoid myocardial depression