Preload-independent measures of cardiac contractility
Core concept
- The problem: every routine index of "contractility" is really an index of loading
- EF, cardiac output, fractional shortening, dP/dt max all change with preload and afterload without any change in intrinsic inotropy
- A normal EF in severe MR is not normal contractility - the regurgitant orifice has unloaded the ventricle
- The solution: measure the pressure-volume relationship across multiple loading conditions (transient IVC occlusion)
- ESPVR - end-systolic pressure-volume relationship
- Slope = Ees (Emax) = the reference load-independent index of contractility
- Steeper slope, leftward shift = inc contractility
- EDPVR - end-diastolic pressure-volume relationship; slope = stiffness, its inverse = compliance
- Upward/leftward shift = diastolic dysfunction (the HFpEF signature)
- ESPVR - end-systolic pressure-volume relationship
3 more sections, plus exam facts
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