On a left ventricular pressure-volume loop, the end-systolic pressure-volume point shifts upward and to the left after intravenous adrenaline, increasing the slope of the line joining these points across several beats. What does this slope represent?

• A Ventricular compliance
• B Contractility (end-systolic elastance) ✓
• C Stroke volume
• D Systemic vascular resistance

Explanation

The end-systolic pressure-volume relationship is nearly linear, and its slope, the end-systolic elastance, is a load-independent index of contractility. Positive inotropes such as adrenaline steepen this line by shifting the end-systolic point up and left. Compliance describes the slope of the end-diastolic pressure-volume curve, a different limb of the loop. Stroke volume is the horizontal width of the loop, and systemic resistance alters loading conditions rather than defining the slope.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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