A system for controlled dissection of a blood vessel wall (W), 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 (W), 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 (W), 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. <EOS>