Which statement about preload is correct?

• A. Afterload is the pressure in the ventricle at end-diastole
• B. Preload is the pressure in the ventricle at end-diastole
• C. Systemic resistance is preload
• D. Ejection fraction is preload

Answer: (B)

Preload is the filling stimulus for the ventricle. It reflects the amount of blood filling the ventricle just before it contracts, which we describe as the pressure (and volume) in the ventricle at end-diastole. This makes the statement that preload is the pressure in the ventricle at end-diastole the correct one.

Think of it in terms of how much stretch the ventricle has when it’s about to beat. A higher end-diastolic pressure/volume means more stretch and, via the Frank-Starling mechanism, typically a greater stroke volume (up to a point).

In contrast, afterload is what the ventricle must push against during ejection—the arterial pressure and systemic vascular resistance. Ejection fraction describes how much of the end-diastolic volume is ejected during systole, a measure of systolic function, not preload.