How do changes in afterload influence the LV operating point on ESPVR, and does ESPVR slope change with afterload?

How do changes in afterload influence the LV operating point on ESPVR, and does ESPVR slope change with afterload?

• A. Afterload changes move the LV operating point along ESPVR; the slope Emax remains the same and reflects contractility.
• B. Afterload changes alter ESPVR slope, increasing Emax with higher afterload.
• C. Afterload changes shift ESPVR vertically but not horizontally.
• D. Afterload does not affect ESPVR at all.

Answer: (A)

The end-systolic pressure–volume relationship encodes how the ventricle behaves at the end of systole, with its slope (end-systolic elastance) reflecting contractility. When afterload is increased but contractility stays the same, the heart still reaches higher end-systolic pressure and leaves more volume in the ventricle, so the end-systolic state moves to a different point along the same ESPVR line. In other words, the operating point shifts along the ESPVR without changing the line itself. The slope of ESPVR, Emax, remains unchanged because it is a measure of the ventricle’s contractility, not the load against which it is pumping. Only if contractility itself changed would the slope of ESPVR change.

The end-systolic pressure–volume relationship encodes how the ventricle behaves at the end of systole, with its slope (end-systolic elastance) reflecting contractility. When afterload is increased but contractility stays the same, the heart still reaches higher end-systolic pressure and leaves more volume in the ventricle, so the end-systolic state moves to a different point along the same ESPVR line. In other words, the operating point shifts along the ESPVR without changing the line itself. The slope of ESPVR, Emax, remains unchanged because it is a measure of the ventricle’s contractility, not the load against which it is pumping. Only if contractility itself changed would the slope of ESPVR change.