hard · MCAT bio-biochem
An investigator infuses a positive inotrope that increases ventricular contractility without changing heart rate, preload, or afterload.
How does this shift the ventricular pressure-volume loop and the Frank-Starling curve simultaneously?
- The end-systolic pressure-volume line rotates leftward and steeper at every afterload, and the Frank-Starling curve simultaneously shifts upward at every preload.
- The PV loop widens only because end-diastolic volume itself rises, while the Frank-Starling curve stays unchanged since contractility is treated as a fully separate variable.
- The end-systolic pressure-volume relationship shifts rightward, lowering stroke volume, while the Frank-Starling curve shifts downward.
- Both curves stay unaffected because inotropic state only modifies heart-rate-dependent relaxation kinetics, never the pressure-volume relationship itself.
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