A system for controlled dissection of a blood vessel wall, the system comprising: a catheter assembly comprising (a) an elongated shaft having a proximal portion and a distal portion configured to be intravascularly delivered to a treatment site within a blood vessel lumen, (b) a support assembly at the distal portion of the elongated shaft, and (c) a lumen extending from the proximal portion to an opening along the support assembly; a valve creation assembly configured to be slidably received within the lumen of the catheter assembly and exit the lumen through the opening, the valve creation assembly configured to be positioned within a blood vessel wall, wherein the valve creation assembly includes-an outer shaft, an inner member extending through the outer shaft, a dissection arm carried by the outer shaft and configured to expand radially outwardly away from the outer shaft when the inner member moves proximally relative to the outer shaft, a tensioning arm configured to extend radially outwardly from the inner member within a plane at a non-zero angle with respect to the plane within which the dissection arm expands; and a handle assembly coupled to the elongated shaft and the valve creation assembly, the handle assembly including an actuator coupled to the outer shaft of the valve creation assembly, wherein movement of the actuator relative to the elongated shaft and/or handle assembly causes the valve creation assembly to expand and collapse. a catheter assembly comprising (a) an elongated shaft having a proximal portion and a distal portion configured to be intravascularly delivered to a treatment site within a blood vessel lumen, (b) a support assembly at the distal portion of the elongated shaft, and (c) a lumen extending from the proximal portion to an opening along the support assembly; a valve creation assembly configured to be slidably received within the lumen of the catheter assembly and exit the lumen through the opening, the valve creation assembly configured to be positioned within a blood vessel wall, wherein the valve creation assembly includes-an outer shaft, an inner member extending through the outer shaft, a dissection arm carried by the outer shaft and configured to expand radially outwardly away from the outer shaft when the inner member moves proximally relative to the outer shaft, a tensioning arm configured to extend radially outwardly from the inner member within a plane at a non-zero angle with respect to the plane within which the dissection arm expands; and an inner member extending through the outer shaft, a dissection arm carried by the outer shaft and configured to expand radially outwardly away from the outer shaft when the inner member moves proximally relative to the outer shaft, a tensioning arm configured to extend radially outwardly from the inner member within a plane at a non-zero angle with respect to the plane within which the dissection arm expands; and a handle assembly coupled to the elongated shaft and the valve creation assembly, the handle assembly including an actuator coupled to the outer shaft of the valve creation assembly, wherein movement of the actuator relative to the elongated shaft and/or handle assembly causes the valve creation assembly to expand and collapse.