In a pressure-volume (PV) loop of the left ventricle, end-systolic pressure-volume relationship (ESPVR) is a measure of cardiac contractility. An increase in preload with unchanged contractility produces which change in the PV loop?

• A The ESPVR line shifts to the left; stroke volume decreases
• B Both ESPVR and EDPVR lines shift upward, reflecting increased contractility
• C The loop widens to the right (increased EDV and increased stroke volume) while the upper-left corner of the loop still touches the same ESPVR line ✓
• D The area of the PV loop decreases, reflecting reduced stroke work

Explanation

On a pressure-volume diagram: (1) preload increase shifts end-diastolic volume (EDV) to the right along the end-diastolic pressure-volume relationship (EDPVR/passive filling curve); (2) with unchanged contractility, the ESPVR line remains in the same position; (3) the end-systolic point therefore moves along the same ESPVR line but to a higher position — the loop widens rightward and stroke volume (EDV - ESV) increases (Frank-Starling mechanism). The area of the PV loop (= stroke work) increases with increased preload. A leftward shift of ESPVR indicates increased contractility (inotropes), not changed preload. This concept is fundamental to distinguishing preload, afterload, and contractility effects on cardiac function.

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

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