In a pressure-volume loop analysis of the left ventricle, a patient starts on a baseline loop. After administering a pure vasodilator that reduces systemic vascular resistance without changing contractility or preload, how does the loop change?

• A The end-systolic pressure-volume relationship line shifts leftward, and the loop becomes taller
• B The end-systolic pressure-volume relationship line remains unchanged, but the loop becomes wider and shorter
• C The end-systolic pressure-volume relationship line shifts rightward, and the loop becomes narrower
• D The end-systolic pressure-volume relationship line remains unchanged, but the loop shifts leftward with a decreased end-systolic volume ✓

Explanation

Reducing afterload allows the ventricle to eject more completely, decreasing end-systolic volume. The end-systolic pressure-volume relationship (ESPVR) reflects contractility, which is unchanged, so its slope remains the same. The loop shifts leftward because the ventricle empties to a smaller volume, increasing stroke volume.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

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