Preload is defined as the filling pressure in the heart at the end of which phase?

Preload is defined as the filling pressure in the heart at the end of which phase?

• A. Systole
• B. Isovolumetric contraction
• C. Diastole
• D. Atrial contraction

Answer: (C)

Preload is the filling pressure in the ventricle at the end of diastole, just before the heart contracts. It reflects how much the ventricle has filled from venous return and corresponds to the end-diastolic pressure (and volume). Systole is the contraction after this filling phase, so preload isn’t defined during systole. The isovolumetric contraction phase occurs after diastole ends, when the ventricles contract but the volume doesn’t change yet, so filling isn’t happening there. Atrial contraction happens during late diastole and helps complete filling, but preload specifically refers to that end-diastolic state, the moment just before systolic contraction.

Preload is the filling pressure in the ventricle at the end of diastole, just before the heart contracts. It reflects how much the ventricle has filled from venous return and corresponds to the end-diastolic pressure (and volume). Systole is the contraction after this filling phase, so preload isn’t defined during systole. The isovolumetric contraction phase occurs after diastole ends, when the ventricles contract but the volume doesn’t change yet, so filling isn’t happening there. Atrial contraction happens during late diastole and helps complete filling, but preload specifically refers to that end-diastolic state, the moment just before systolic contraction.