Abstract: Medical methods and devices for treating aortic dissections. A catheter-based cutting device permits cutting a septum of acute or chronic aortic dissections, in a retrograde manner. The catheter includes a base section having a central lumen therethrough and two flexible arms extending from a distal end thereof. The flexible arms can each have a guide wire channel therethrough. With distal ends of the two flexible arms separated, the two arms form a Y-shape with the base section. In one embodiment, with distal ends of the two flexible arms together, the two arms have a longitudinal profile, about a periphery thereof, identical to a longitudinal profile of the base section. A cutting component resides between the two arms. The cutting component can face distally outward between the two arms with the distal ends of the two flexible arms separated.