Devices and methods for assisting valve function, replacing venous valves, and predicting valve treatment successes. In at least one exemplary embodiment of an endograft body configured for expansion within a luminal organ of the present disclosure, the endograft body comprises (a) a first portion having a proximal end defining a proximal end aperture and a distal end defining a distal end aperture, the first portion configured to increase a velocity of fluid flowing therethrough, (b) a second portion having a second portion proximal end defining a second portion proximal end aperture and a second portion distal end defining a second portion distal end aperture.
