Figure 9.

Volumetric growth and contractile adaptation following a sustained increase in afterload with (red) and without (black) contractile fatigue. (A,B) Frequency and systolic contractility increase in response to volumetric growth. For simulating contractile fatigue, both contractile parameters subsequently decrease to the values prior to mechanical perturbation. (C,D) Shear and circumferential stress are restored by long-term growth and contractile adaptation. Circumferential stress can remain at homeostatic levels following contractile fatigue, but shear stress cannot. (E,F) Unloaded thickness and midwall diameter increase in response to a sustained increase in afterload. Reference geometry further increases following contractile fatigue. (G) EDD decreases because radial growth leads to a decreased inner diameter, but changes in contractility do not directly affect EDD. Growth also leads to a decrease in ESD which assists in maintenance of ejection fraction, but contractile fatigue leads to an increase in ESD and decrease of ejection fraction. (H) Volumetric growth results in a decrease of average outflow rate, and contractile fatigue results in a further decrease in outflow rate.