Cardiac Cycle and Hemodynamics · USMLE Step 1

Which phase of the cardiac cycle contributes most to ventricular filling at rest under normal physiology?

  1. Atrial systole (atrial kick)
  2. Isovolumetric contraction
  3. Early diastolic rapid filling
  4. Isovolumetric relaxation
Show answer and explanation

Correct answer: Early diastolic rapid filling

During early diastole, after semilunar valve closure and mitral valve opening, rapid passive ventricular filling delivers the majority of ventricular volume. Atrial systole contributes a smaller proportion at rest.

Difficulty: Medium Question 19 of 21

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