Which factor does NOT directly alter the ESPVR slope (Emax)?

Which factor does NOT directly alter the ESPVR slope (Emax)?

• A. Contractility
• B. Afterload
• C. Heart rate
• D. LV geometry

Answer: (A)

End-systolic elastance (the slope of the ESPVR, Emax) is a measure of the ventricle’s contractile state. It becomes steeper when contractility increases and shallower when contractility decreases, reflecting load-independent information about how much pressure the ventricle can generate at end-systole for a given volume. Changes in afterload shift the end-systolic point on the pressure–volume diagram but don’t directly change the slope of the ESPVR. If the inotropic state stays the same, increasing or decreasing afterload moves the PV loop without appreciably altering Emax. Heart rate and LV geometry can modify the overall loop shape and wall stress, and they can influence contractility indirectly, but the slope itself remains determined primarily by the contractile state. Thus, the factor that does not directly alter the ESPVR slope is afterload.

End-systolic elastance (the slope of the ESPVR, Emax) is a measure of the ventricle’s contractile state. It becomes steeper when contractility increases and shallower when contractility decreases, reflecting load-independent information about how much pressure the ventricle can generate at end-systole for a given volume.

Changes in afterload shift the end-systolic point on the pressure–volume diagram but don’t directly change the slope of the ESPVR. If the inotropic state stays the same, increasing or decreasing afterload moves the PV loop without appreciably altering Emax. Heart rate and LV geometry can modify the overall loop shape and wall stress, and they can influence contractility indirectly, but the slope itself remains determined primarily by the contractile state.

Thus, the factor that does not directly alter the ESPVR slope is afterload.