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Q-bank · cardiac phys →3D heart →
Cardiovascular · 9 min
Cardiovascular physiology + valve disease
Wiggers, hemodynamics, valve targets, induction by lesion.
Mnemonic — MAP = CO × SVR
Hemodynamic Ohm's law analog
MAP = CO × SVR
- MAPMean arterial pressure (your goal)
- COCardiac output = HR × stroke volume (preload + afterload + contractility)
- SVRSystemic vascular resistance (vascular tone — drops in sepsis, drops with volatile anesthetic)
If MAP is low: figure out which side dropped. Hot/dry/distended = ↓SVR (give vasopressor). Cold/clamped = ↓CO (give fluid + inotrope).
Valve targets — induction
| Lesion | HR | Preload | Afterload | Contractility |
|---|---|---|---|---|
| AS — fixed | Normal-slow + sinus | Full | ↑↑ (no drops) | Maintain |
| AR — volume | Fast (less regurg) | Full | ↓ (forward) | Maintain |
| MS — diastolic fill | Slow + sinus | Cautious | Maintain | Maintain |
| MR — volume | Fast | Full | ↓ | Maintain |
| HCM | Slow | Full | ↑ | AVOID inotropes |
Rule
AS rule
Maintain SR. AVOID hypotension (no forward flow if perfusion pressure < gradient). Phenylephrine first-line. Treat HR aggressively (sinus only — atropine if brady, esmolol if tachy + ischemia). Spinal contraindicated in severe AS.
Hemodynamic patterns
- Hypovolemic shock: ↓CO ↑SVR ↓CVP/PCWP
- Cardiogenic: ↓CO ↑SVR ↑CVP/PCWP
- Septic (warm): ↑CO ↓SVR ↓-N CVP
- Obstructive (PE/tamponade): ↓CO ↑SVR ↑CVP
- Anaphylaxis: ↓CO ↓SVR ↓CVP