The pressure-volume (PV) loops in answer choice B represent an increase in afterload. With an increase in afterload, the end-diastolic volume remains the same. The point at which the aortic valve opens and ventricular ejection begins occurs at higher pressure. Aortic valve closure occurs at both higher end-systolic pressure and volume. The dashed line represents the end-systolic pressure-volume relation (ESPVR) and is related to contractility. The ESPVR is unchanged with a change in afterload.
The change depicted from the black to red PV loop in choice A represents an increase in preload. Note that end-diastolic volume increases. An increase in preload does not change the ESPVR. The stroke volume and ejection fraction increase with increased preload.
In choice C, there is an increase in the slope of ESPVR depicting an increase in contractility. This increases stroke volume and ejection fraction.
In choice D, there is a decrease in preload with lower end diastolic volume. This represents the inverse of choice A.
References:
Boron, W. and Boulpaep E.L. Medical Physiology, Second Edition. Chapter 22: The Heart as a Pump.
