At rest, atrial systole contributes approximately what proportion of left ventricular end-diastolic volume?
- A About 25 percent ✓
- B About 5 percent
- C About 50 percent
- D About 75 percent
Correct answer: A. About 25 percent
Explanation
Most ventricular filling is passive and occurs early in diastole; atrial contraction tops up roughly 20 to 30 percent of end-diastolic volume at rest. Its contribution becomes far more significant at high heart rates when diastolic filling time is short, which is why loss of atrial systole, as in atrial fibrillation, is poorly tolerated in a stiff or hypertrophied ventricle. Options C and D grossly overstate the passive-to-active filling ratio.
Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.