Differentiate passive ventricular filling from atrial contraction and identify which phase the atrial kick contributes to?

• A. Passive filling occurs in early diastole; atrial contraction (atrial kick) contributes late in diastole, increasing EDV.
• B. Passive filling occurs in late diastole; atrial kick contributes in early systole.
• C. Passive filling occurs during systole; atrial kick occurs during diastole.
• D. Atrial kick contributes to systole, not affected EDV.

Answer: (A)

Passive ventricular filling happens when the ventricle relaxes after systole and the mitral valve opens, letting blood flow from the left atrium into the ventricle without atrial contraction. This rapid flow mainly occurs in early diastole. Later in diastole, the atria contract to give a final push—the atrial kick—that sends additional blood into the ventricle, increasing the end-diastolic volume. This atrial contraction occurs at the end of diastole, just before the ventricle starts to contract, and it raises preload for the next beat. So the best description is: passive filling in early diastole; atrial contraction contributes late in diastole, increasing EDV.