Methods, apparatuses, and systems are described for accessing a body lumen for subsequent treatment thereof. Systems include a cannula configured to penetrate a wall of a body lumen and to passively transition to a nonlinear shape within the body lumen as an elongate member is withdrawn from the distal section of the cannula. Other embodiments include a handle, a cannula removably disposed within a lumen of the handle, and a penetration member sized to advance through a lumen of the cannula, the cannula configured to passively transition to a nonlinear shape as the penetration member is withdrawn from a distal section of the cannula, and a cannula hub configured to selectively engage with a proximal end of the handle to selectively lock rotational movement of the cannula with respect to the handle.
