Preload is defined as which of the following?

Preload is defined as which of the following?

• A. The pressure after systole.
• B. The volume dependent on filling before contraction.
• C. The mean arterial pressure.
• D. The afterload of the ventricle.

Answer: (B)

Preload is the amount the ventricular muscle fibers are stretched at the end of diastole, which corresponds to the volume of blood filling the ventricle before it contracts. In other words, it’s the end-diastolic volume—the volume dependent on filling before contraction. It isn’t the pressure after systole, nor mean arterial pressure, nor afterload (the pressure the ventricle must overcome during ejection). The concept is central to how the heart increases force of contraction with greater filling (the Frank-Starling relationship) up to physiologic limits.

Preload is the amount the ventricular muscle fibers are stretched at the end of diastole, which corresponds to the volume of blood filling the ventricle before it contracts. In other words, it’s the end-diastolic volume—the volume dependent on filling before contraction. It isn’t the pressure after systole, nor mean arterial pressure, nor afterload (the pressure the ventricle must overcome during ejection). The concept is central to how the heart increases force of contraction with greater filling (the Frank-Starling relationship) up to physiologic limits.