The present technology is directed generally to devices, systems, and methods for capturing and cutting fibrous and trabeculated structures (such as synechiae) in vessel lumens. In one embodiment, the present technology includes an intraluminal tissue modifying system configured to capture the fibrous structures, put the fibrous structures in tension, and controllably cut through the fibrous structures without applying appreciable additional force to the vessel wall. The system may include an expandable capture device and a cutting device.