Patent Publication Number: US-2020289102-A1

Title: Intravascular devices, systems, and methods for the controlled dissection of body lumens

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 14/972,006, filed Dec. 16, 2015, which claims the benefit of U.S. Provisional Patent Application No. 62/092,809, filed Dec. 16, 2014, entitled “INTRAVASCULAR DEVICES, SYSTEMS, AND METHODS FOR CONTROLLED DISSECTION OF BODY LUMENS,” both of which are incorporated herein by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present technology relates generally to devices and methods for intravascular modification of body lumens. Some embodiments of the present technology relate to the intravascular creation of valve leaflets within blood vessels. 
     BACKGROUND 
       FIGS. 1A and 1B  are schematic cross-sectional views of a normal human vein V. The vein V includes a valve formed of two leaflets L.  FIG. 1A  shows the valve in an open position in which the leaflets L separate to allow blood to flow towards the heart in the direction indicated by arrows A 1 .  FIG. 1B  shows the valve in a closed position in which the leaflets L come together to block the flow of blood away from the heart in the direction indicated by arrows A 2 .  FIG. 1C  shows a vein V′ having a diseased or otherwise damaged valve comprised of leaflets L′. As shown in  FIG. 1C , the leaflets L′ are structurally incompetent and allow venous reflux, or the flow of venous blood away from the heart (arrows A 2 ). Venous reflux can lead to varicose veins, pain, swollen limbs, leg heaviness and fatigue, and skin ulcers, amongst other symptoms. 
     Venous reflux can occur anywhere throughout the venous system, which includes superficial veins (veins closer to the skin) and deep veins. Because deep veins are harder to access, deep veins are also harder to treat surgically. Existing methods for treating damaged or diseased vein valves in deep veins include surgical repair of the diseased vein and/or valve, removal of the damaged vein, and/or vein bypass. However, all of the foregoing treatment options include relatively lengthy recovery times and expose the patient to the risks involved in any surgical procedure, such as infection and clotting. Experimental treatments such as implantable venous valves, external venous valve banding, and heat-induced vein shrinkage have been attempted but each treatment has significant shortcomings. In addition, compression stockings are sometimes used to ameliorate symptoms but do not address the underlying problem. Accordingly, there exists a need for improved devices, systems, and methods for treating damaged or diseased valves. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present technology can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on illustrating clearly the principles of the present disclosure. 
         FIGS. 1A and 1B  are schematic cross-sectional views of a normal human vein. 
         FIG. 1C  is a schematic cross-sectional view of an irregular human vein having a damaged or diseased valve. 
         FIG. 2A  is a front-elevated, splayed view of a blood vessel showing an opening at an interior surface of the blood vessel wall and a space within the blood vessel wall. 
         FIG. 2B  is a cross-sectional end view of the space shown in  FIG. 2A . 
         FIG. 2C  is a front-elevated, splayed view of the blood vessel in  FIGS. 2A and 2B  showing a dissection pocket within the blood vessel wall. 
         FIG. 2D  is a cross-sectional end view of the dissection pocket shown in  FIG. 2C . 
         FIG. 2E  is a front-elevated, splayed view of the blood vessel in  FIGS. 2A-2D , showing a leaflet formed of the blood vessel wall having a mouth. 
         FIG. 2F  is a side cross-sectional view showing the leaflet of  FIG. 2E . 
         FIG. 3A  is a side view of a distal portion of a dissection device configured in accordance with an embodiment of the present technology. 
         FIG. 3B  is a top view of the distal portion shown in  FIG. 3A . 
         FIG. 3C  is a top isolated view of a dissection device in a low-profile state configured in accordance with an embodiment of the present technology. 
         FIG. 3D  is a top isolated view of a dissection device in a deployed state configured in accordance with an embodiment of the present technology. 
         FIG. 4A  is a cross-sectional side view of a dissection device in a low-profile state configured in accordance with an embodiment of the present technology. 
         FIG. 4B  is a top view of the dissection device shown in  FIG. 4A . 
         FIG. 4C  is a cross-sectional side view of the dissection device shown in  FIG. 4A  in the deployed state configured in accordance with an embodiment of the present technology. 
         FIG. 4D  is a top view of the dissection device shown in  FIG. 4C . 
         FIG. 5A  is a top view of a dissection device configured in accordance with another embodiment of the present technology, shown in a deployed state. 
         FIG. 5B  is a partial cross-sectional end view of the dissection device of  FIG. 5A  shown deployed in a blood vessel wall. 
         FIG. 6A  is a top view of a dissection device in a low-profile state configured in accordance with an embodiment of the present technology. 
         FIG. 6B  is an end view of the dissection device shown in  FIG. 6A . 
         FIG. 6C  is a top view of the dissection device of  FIG. 6A  in a deployed state configured in accordance with an embodiment of the present technology. 
         FIG. 6D  is an end view of the dissection device shown in  FIG. 6C . 
         FIG. 7  shows another embodiment of a dissection device having an outer membrane configured in accordance with the present technology. 
         FIG. 8A  is a side view of a dissection device in a low profile state configured in accordance with another embodiment of the present technology. 
         FIG. 8B  is an end view of the dissection device shown in  FIG. 8A . 
         FIG. 8C  is an end view of the dissection device shown in  FIG. 8A  in a deployed state configured in accordance with an embodiment of the present technology. 
         FIGS. 9A and 9B  are isometric views of another embodiment of a dissection device in a low-profile state and a deployed state, respectively, configured in accordance with the present technology. 
         FIG. 10  is an isometric view of another embodiment of a dissection device configured in accordance with the present technology, shown in a deployed state. 
         FIG. 11A  is an isometric view of a dissection device configured in accordance with another embodiment of the present technology, shown in a low-profile state. 
         FIG. 11B  is an isometric view of the dissection device shown in  FIG. 11A , shown in a partially-deployed state. 
         FIG. 11C  is an isometric view of the dissection device shown in  FIGS. 11A and 11B , shown in a fully-deployed state. 
         FIGS. 12A-12C  are isometric views of a dissection device configured in accordance with another embodiment of the present technology, shown during various stages of deployment. 
         FIGS. 13A and 13B  are isometric views of another embodiment of a dissection device configured in accordance with the present technology, shown during various stages of deployment. 
         FIG. 13C  is an isometric view of a cutting device configured for use with the dissection devices of the present technology. 
         FIGS. 14A and 14B  are isometric views of another embodiment of a dissection device configured in accordance with the present technology, shown during various stages of deployment. 
         FIG. 14C  is an isometric view of a cutting device configured for use with the dissection devices of the present technology. 
         FIGS. 15A and 15B  are isometric views of another embodiment of a dissection device configured in accordance with the present technology, shown in a low-profile state and a deployed state, respectively, 
         FIGS. 16A and 16B  are isometric views of another embodiment of a dissection device configured in accordance with the present technology, shown during various stages of deployment. 
         FIG. 17  is an isometric view of a cutting device of the dissection device shown in  FIGS. 16A and 16B , shown isolated from the dissection device. 
         FIGS. 18-20  are front views of cutting devices that are useful with dissection devices of the present technology. 
         FIG. 21A  is a perspective, partially cross-sectional side view of a dissection device configured in accordance with another embodiment of the present technology, shown in a deployed state. 
         FIG. 21B  is an end view of the dissection device of  FIG. 21A . 
         FIG. 22A  is a top perspective view of the dissection device of  FIGS. 21A and 21B  in a low-profile state configured in accordance with an embodiment of the present technology. The delivery catheter constraining the device has been removed for ease of illustration. 
         FIG. 22B  is a top perspective view of the dissection of  FIGS. 21A and 21B  in a first deployed state configured in accordance with an embodiment of the present technology. 
         FIG. 22C  is a top perspective view of the dissection of  FIGS. 21A and 21B  in a second deployed state configured in accordance with an embodiment of the present technology. 
         FIG. 23  is a schematic end view of a portion of a vessel wall, showing a dissection pocket during formation using the dissection devices configured in accordance with the present technology. 
         FIG. 24A  is an axial perspective view of another embodiment of a dissection device configured in accordance with the present technology. 
         FIG. 24B  is an end view of the dissection device shown in  FIG. 24A . 
         FIG. 25  is a side perspective view of another embodiment of a dissection device configured in accordance with the present technology. 
         FIG. 26  is an isometric view of another embodiment of a dissection device configured in accordance with the present technology. 
         FIG. 27A  is a side view of a dissection device in a low-profile state configured in accordance with an embodiment of the present technology. 
         FIG. 27B  is a side view of the dissection device shown in  FIG. 27A  in a first deployed state configured in accordance with an embodiment of the present technology. 
         FIG. 27C  is a top view of the dissection device shown in  FIGS. 27A and 27B  in a second deployed state configured in accordance with an embodiment of the present technology. 
         FIGS. 28A-28D  are top views of a dissection device showing various states of deployment configured in accordance with an embodiment of the present technology. 
         FIG. 29A  is a top view of a dissection device configured in accordance with an embodiment of the present technology. 
         FIG. 29B  is an end view of the dissection device shown in  FIG. 29A . 
         FIGS. 30A-30C  are top views of a dissection device during various stages of deployment configured in accordance with an embodiment of the present technology. 
         FIG. 31  is a top perspective view of a dissection device shown within a blood vessel and configured in accordance with an embodiment of the present technology. The blood vessel is shown in partial cross-section for ease of illustration. 
         FIG. 32A  is a top perspective view of a dissection device shown within a blood vessel and configured in accordance with an embodiment of the present technology. The blood vessel is shown in partial cross-section for ease of illustration. 
         FIG. 32B  is a top, isolated view of the dissection device shown in  FIG. 32A  configured in accordance with an embodiment of the present technology. 
         FIG. 32C  is an end view of the dissection device shown in  FIG. 32B  configured in accordance with an embodiment of the present technology. 
         FIG. 33A  is a top perspective view of a dissection device shown within a blood vessel and configured in accordance with an embodiment of the present technology. The blood vessel is shown in partial cross-section for ease of illustration. 
         FIG. 33B  is a top, isolated view of the dissection device shown in  FIG. 33A  configured in accordance with an embodiment of the present technology. 
         FIG. 33C  is an end view of the dissection device shown in  FIG. 33B  configured in accordance with an embodiment of the present technology. 
         FIG. 34A  is a top perspective view of a dissection device shown within a blood vessel and configured in accordance with an embodiment of the present technology. The blood vessel is shown in partial cross-section for ease of illustration. 
         FIG. 34B  is a cross-sectional end view of a gel deployed within the vessel wall. 
     
    
    
     DETAILED DESCRIPTION 
     The present technology provides devices, systems, and methods for the controlled dissection of tissue adjacent a body lumen. For example, some embodiments of the present technology are directed to the intravascular creation of one or more dissection pockets within a blood vessel wall, as well as the intravascular creation of one or more valve leaflets from a blood vessel wall. An overview of the novel methodology of the present technology in conjunction with general aspects of one of the anatomical environments in which the disclosed technology operates is described below under heading 1.0 (“Overview”) with reference to  FIGS. 2A-2F . Particular embodiments of the technology are described further under heading 2.0 (“Representative Embodiments”) with reference to  FIGS. 3A-26 . Additional embodiments are described under heading 3.0 (“Additional Embodiments”) with reference to  FIGS. 27A-34B . 
     1.0 Overview 
       FIGS. 2A-2F  are schematic, splayed views of a blood vessel V (e.g., a vein) showing the interior of the blood vessel V during various stages of a method for the intravascular creation of a dissection pocket and/or a valve leaflet from a blood vessel wall W in accordance with the present technology.  FIGS. 2A and 2B  illustrate a first stage of the method in which an opening O is made in the interior surface IS of the vessel wall W to gain access to an interior portion of the vessel wall W. During this first stage, an access space S is created within the vessel wall W for the subsequent delivery of one or more dissection devices of the present technology. Creation of the opening O and/or space S can be achieved using a dissection device of the present technology and/or a separate device, such as one or more of the dissection assemblies and/or inner members disclosed in U.S. patent application Ser. No. 14/667,670, filed Mar. 24, 2015, U.S. patent application Ser. No. 13/035,752, filed Feb. 25, 2011, and U.S. patent application Ser. No. 13/450,432, filed Apr. 18, 2012, all of which are incorporated herein by reference in their entireties. Once the dissection device is positioned within the space S, the dissection device can be deployed to separate tissue at the periphery P ( FIG. 2B ) of the space S. As shown in  FIGS. 2A-2D , the enlarged space S forms a dissection pocket DP having a predetermined size and shape and extending along a dissection plane P within the vessel wall W. To transform the dissection pocket DP into a leaflet L (shown in  FIGS. 2E and 2F ), the dissection device and/or a separate cutting device of the present technology can be used to cut the tissue at the proximal edge E of the dissection pocket DP adjacent the opening O. For example, the dissection device and/or cutting device can cut the vessel wall tissue at the edge of the dissection pocket DP that extends laterally away from the opening O, as indicated by arrows A in  FIG. 2C . 
     It will be appreciated that the foregoing description is intended as a reference as and does not limit the description of the present technology presented herein. Additionally, with regard to the terms “distal” and “proximal” within this description, unless otherwise specified, the terms can reference a relative position of the portions of a dissection device and/or an associated delivery device with reference to an operator and/or a location in the vasculature. 
     2.0 Representative Embodiments of Controlled Dissection Devices and Methods of Use 
       FIG. 3A  is a side view of a distal portion of a dissection device  300  in a low-profile state configured in accordance with the present technology. The dissection device  300  can include an elongated shaft  310  having a proximal portion (not shown) and a distal portion  303  configured to be delivered intravascularly to a treatment site proximate the wall of a body lumen (e.g., a blood vessel) and positioned within the wall at the treatment site. In some embodiments, the elongated shaft  310  can be configured to be slidably received within a lumen of a delivery and/or guide catheter (not shown) for intravascular delivery to the treatment site. As shown in  FIG. 3A , the dissection device  300  can include one or more moveable arms (referred to collectively as dissection arms  302 , referred to individually as first and second dissection arms  302   a ,  302   b ) configured to extend laterally beyond the shaft  310  and into a portion of the lumen wall adjacent the shaft  310 , thereby separating the portion into two distinct layers, as described in greater detail below. 
       FIG. 3B  is a top view of the distal portion of the dissection device  300  shown in  FIG. 3A . Referring to  FIGS. 3A and 3B  together, the distal portion  303  of the elongated shaft  310  can include a rounded, atraumatic end region  314  and an aperture  318  ( FIG. 3A ) proximal of the end region  314  that extends laterally through the shaft  310 . In some embodiments, the end region  314  can alternatively include a sharpened tip (not shown) configured to gain access to the interior portion of the lumen wall. The aperture  318  can be bounded by a distal sidewall  305 , a bottom sidewall  304 , a proximal sidewall  309 , and a top sidewall  320 . As such, the shaft  310  can include a first opening  324  at one side of the aperture  318  and a second opening  326  at the opposite side of the aperture  318 . At least the distal portion  303  can be positioned within the aperture  318  such that, when deployed, the first and second dissection arms  302   a ,  302   b  extend laterally through the first and second openings  324 ,  326 , respectively. In some embodiments (not shown), one or more of the sidewalls  305 ,  307 ,  309  and  320  can be modular to facilitate device assembly. For example, in some embodiments, the top sidewall  320  can be a separate piece that, during assembly, can be fixed in place after positioning the dissection arms  302  within the aperture  318 . 
       FIG. 3C  is a top view of the dissection device  300  in a low-profile state, and  FIG. 3D  is a top view of the dissection device  300  in a deployed state. The elongated shaft  310  is shown in phantom lines to better illustrate the dissection arms  302 . Referring to  FIGS. 3A-3D  together, the dissection device  300  includes an elongated actuation member  312  configured to move from the low-profile state of  FIG. 3C  to the deployed state of  FIG. 3D . Although the dissection device  300  is shown with two dissection arms  302  in  FIGS. 3A-3D , in other embodiments the dissection device  300  can have a single arm or more than two arms. As shown in  FIGS. 3C-3D , the dissection arms  302  can individually include a proximal region  315  rotatably coupled to the elongated actuation member  312  via a linkage  308 , a distal region  317 , and a curved slot (labeled individually as first and second slots  320   a ,  320   b ) positioned between the proximal and distal regions  315 ,  317 . The curved slots  320  can be configured to receive a coupling element  307  extending from or affixed to the elongated shaft  310 . For example, in the embodiment shown in  FIGS. 3A-3D , the coupling element  307  can be a pin or other mechanical-linkage that extends from the elongated shaft  310  across the aperture  318  through the first and second slots  320   a ,  320   b.    
     As best shown in  FIGS. 3C and 3D , in some embodiments the dissection arms  302  can be generally flat and can have a rectangular shape with rounded corners. In other embodiments, the individual dissection arms  302  can have a slight bend along a longitudinal direction (e.g., non-flat) and/or can have any suitable shape and/or configuration. Although the slots  320  shown in  FIGS. 3C and 3D  are curved, in other embodiments the slots  320  can be linear and/or contain one or more linear segments. In the illustrated embodiment, a cutting element  321  (labeled individually as first and second cutting elements  321   a ,  321   b ) is attached to at least a portion of the outer edge  313  of each of the dissection arms  302 . As such, the dissection arms  302  can have an atraumatic distal portion  317  configured for blunt dissection, and a sharpened portion along the length of the cutting element  321   a ,  321   b . In some embodiments (not shown), the dissection arms  302  may not include any cutting element. Additionally, in particular embodiments, the entire outer edge  313  can be sharp or beveled to facilitate the outer edge  313  being able to cut through the vessel wall during deployment, if desired. In other embodiments, the outer edge  313  of each of the dissection arms  302  can be atraumatic. 
     Although the slots  320  shown in  FIGS. 3C and 3D  have a single bend, in other embodiments the slots  320  can have multiple bends, segments and/or can comprise complex shapes. For example, the shape of the slots  320  and/or position of the slots  320  along the dissection arms  302  can be chosen to affect a particular rotation of the dissection arms  302  around the coupling element  307 , thereby creating a dissection pouch of a desired geometry within the vessel wall. Moreover, in some embodiments the dissection arms  302  can have slots  320  of the same size and/or shape, and in some embodiments the dissection arms  302  can have slots  320  of different sizes and/or shapes. 
     Referring still to  FIGS. 3A-3D , the actuation member  312  can have a proximal portion (not shown) and a distal portion  311 , and can be configured to move axially within the elongated shaft  310  to affect rotation of the dissection arms  302 . The actuation member  312  can extend distally from the proximal portion through a lumen of the elongated shaft  310  to the distal portion of the shaft  310  and/or the aperture  318 . In some embodiments, the actuation member  312  can be a push/pull rod. In other embodiments, other suitable actuation devices and methods known in the art can be used to deploy the dissection arms  302  of the dissection device  300 . 
     In the low-profile state ( FIG. 3C ), the dissection arms  302  of the dissection device  300  can be generally aligned with the elongated shaft  310  (shown in phantom lines) such that the majority of each arm  302  lies within the lateral boundaries of the elongated shaft  310 . In some embodiments, each of the arms  302  in their entireties lies within the lateral boundaries of the elongated shaft  310 . To deploy the dissection device  300 , the actuation member  312  can be pushed distally as indicated by arrow A (e.g., from the proximal portion), thereby urging the dissection arms  302  in a distal direction. As shown in  FIG. 3D , as the dissection arms  302  are urged distally, the individual slots  320   a ,  320   b  slide along the coupling element  307 , thereby forcing the dissection arms  302  to rotate based on the shape of each slot  320   a ,  320   b . As the dissection arms  302  rotate, they extend laterally through the openings  324 ,  326  ( FIG. 3A ) in the elongated shaft  310  and engage the lumen wall tissue adjacent the shaft  310 . The edge  313  of the individual dissection arms  302  separates layers or stratums of the wall tissue from each other as the dissection arms  302  move outwardly and away from the longitudinal axis of the shaft  310 . The edge  313  of each arm  302  can separate the tissue by shear force (atraumatic edges) or by cutting the tissue (sharp edges), or both. As such, movement of the dissection arms  302  separates the tissue at the periphery of the space S ( FIGS. 2A and 2B ) in which it sits within the vessel wall and creates a dissection pocket DP ( FIGS. 2C and 2D ) having a geometry dictated, at least in part, by the size and shape of the dissection arms  302 , as well as the path of the edges  313  of the dissection arms  302  through the tissue. For example, as shown in  FIG. 3D , the dissection arms  302  of the dissection device  300  can be configured to create a dissection pocket having a rounded distal-most edge. A rounded distal periphery can be advantageous, especially when forming autologous leaflets within the vasculature, as the rounded contour promotes the flushing of old blood out of the dissection pocket DP during each venous pumping cycle, thereby preventing clotting within the dissection pocket DP. 
     Although the dissection arms  302  of  FIGS. 3C-3D  are shown rotating about 30 degrees from a longitudinal axis of the elongated shaft  310 , in other embodiments the slots  320  and/or dissection arms  302  can be configured to rotate any suitable distance to achieve a desired dissection pocket shape (such as that shown in  FIG. 2B ). 
     One method for using the dissection device  300  is described with reference to  FIGS. 2A-2F . The dissection device  300  can be positioned within the blood vessel V (e.g., a vein) proximate a treatment site. The dissection device  300  can then be inserted through the opening O ( FIG. 2A ) in the vessel wall W and be positioned within the access space S within the vessel wall W. In some embodiments, the dissection  300  can be used to create the opening O and/or access space S. For example, in some embodiments the dissection device  300  can have a sharp distal edge that can penetrate the vessel wall W. Upon placement of the distal portion  303  within the vessel wall W, the actuation member  312  can be advanced distally to expand the dissection arms  302  laterally away from a longitudinal axis of the dissection device  300 . As the dissection arms  302  move outwardly, the edges  303  of the dissection arms  302  separate the vessel wall tissue into two layers (e.g., via blunt dissection and/or sharp dissection) to form a dissection pocket DP having a desired size and shape. Once the dissection pocket DP is formed, the dissection device  300  can be pulled proximally such that the cutting elements  321  engage tissue at a proximal edge E of the dissection pocket DP extending laterally from the opening O and cut the tissue to transform the opening O into a mouth M ( FIG. 2C ), thereby forming a leaflet L. In other embodiments, the opening O can be widened with a separate device. The mouth can extend along a circumferential length of the vessel wall between 90 or about 90 degrees and 330 or about 330 degrees. Depending on the size of the mouth M desired, the actuation member  312  can be withdrawn proximally to move the dissection arms  302  inwardly towards the longitudinal axis of the device  301 , before retraction of the device  301 , thereby decreasing the reach of the cutting elements  321  (and thus the size of the mouth M). In some embodiments, the device  301  can widen the opening O while being retracted in the low-profile state, as the proximal portion of the cutting elements  321  create the mouth M. 
       FIGS. 4A and 4B  are cross-sectional top and end views, respectively, of an alternate dissection device  400  in a low-profile state configured in accordance with an embodiment of the present technology. The dissection device  400  can include a tubular shaft  410  and an actuation member  420  configured to be slidably received by the shaft  410 . The actuation member  420  can include an elongated push/pull rod  412  and an expander  414  coupled to a distal portion of the push/pull rod  412 . The tubular shaft  410  can include a proximal portion  411 , a tapered portion  408 , and a distal portion  406 . As shown in  FIG. 4A , the inner diameter of the proximal portion  411  can be greater than the inner diameter of the distal portion  406 . For example, the shaft  410  can comprise a deformed hypotube (e.g., made of Nitinol, stainless steel, etc.). The distal portion  406  of the shaft  410  can include a first slot  403  and a second slot  405  ( FIG. 4B ) spaced apart from the first slot  403  along the circumference of the distal portion  406 . The first and second slots  403 ,  405  can extend along the length of the distal portion  406 , thereby dividing the distal portion  406  into a first arm  402   a  and a second arm  402   b . As such, the first and second arms  402   a ,  402   b  are configured to bend relative to at least the proximal portion  411  of the shaft, as well as freely of one another. 
       FIGS. 4C and 4D  are cross-sectional top and end views, respectively, of the dissection device  400  in a deployed state configured in accordance with an embodiment of the present technology. As shown in  FIGS. 4C and 4D , as the actuation member  420  is advanced distally, the expander  414  forces the first and second arms  402   a ,  402   b  outwardly, away from the longitudinal axis of the device  400 . In some embodiments, the slots  403 ,  405  can occupy the same circumference of the distal portion and be spaced 180 degrees or about 180 degrees apart from one another such that arms  402   a ,  402   b  expand outwardly within generally the same plane, as shown in  FIG. 4D . 
       FIG. 5A  is an end view of a dissection device  500  having angled arms  502   a ,  502   b  configured in accordance with the present technology (the actuation member is not shown for ease of illustration). The dissection device  500  of  FIG. 5A  can be generally similar to the dissection device  400  of  FIG. 4A , except the first slot  503  of  FIG. 5A  takes up a larger portion of the circumference of the distal portion than the second slot  505 . As a result, the first and second arms  502   a ,  502   b  extend outwardly from the shaft at a non-180 degree angle with respect to one another (and thus not within the same plane). Such a configuration can be advantageous, especially when used for creation of dissection pockets within tubular or curved body lumens, such as blood vessels. Because access to the interior portion of the vessel wall is limited to a narrow access channel C within the wall (see  FIG. 2B ), dissection of the wall begins at the narrow access channel and propagates from both sides of the channel laterally away from the channel along the circumference of the vessel. As the wall tissue can be fragile, it can be advantageous to reduce the amount of stretching of the newly-created wall layers, especially in a direction perpendicular to the longitudinal axis of the vessel. As shown in the anatomical end view of  FIG. 5B , the angled arms  502  of the dissection device  500  reduces such stretching by providing a separating force in an angled plane that closely mimics the curvature of the vessel wall V. As such, the slots  503 ,  505  can have any suitable sizing and/or configuration to achieve a desired arm angle based on the size and curvature of the targeted lumen L. For example, in this and any embodiment of the present technology, the arms can deploy at an angle θ (see  FIG. 5A ) of between about 100 degrees and about 179 degrees. In some embodiments, the angle θ can be between about 115 degrees and 205 degrees. Additionally, the angle θ can be between about 120 degrees and about 140 degrees. In a particular embodiment, the angle θ can be about 130 degrees. 
       FIG. 6A  is a top view of another embodiment of a dissection device  600  in a low-profile state configured in accordance the present technology.  FIG. 6B  is an end view of the dissection device  600  shown in  FIG. 6A . Referring to  FIGS. 6A and 6B  together, the dissection device  600  can include an elongated pull member  606  slidably positioned at least partially within a shaft  604 . The pull member  606  can include a proximal portion (not shown) and a distal portion  607 . The shaft  604  can include a distal portion  603  having first and second arms  602   a ,  602   b . For example, in the embodiment shown in  FIGS. 6A and 6B , the distal portion  603  of the shaft  604  is bifurcated, and the bifurcations form the first and second arms  602   a ,  602   b . In these and other embodiments, one or more regions of the shaft  604  can be removed at the distal portion  603  to form the first and second arms  602   a ,  602   b . The distal portion  607  of the pull rod  606  can be coupled to a distal portion of each of the arms  602   a ,  602   b  via a coupling element  610 , such as a pin or other suitable mechanical linkage. Alternatively, the distal portion  607  of the pull rod  606  can be coupled to a distal portion of each of the arms  602   a ,  602   b  via a solder, weld, or swage joint. 
       FIG. 6C  is a top view of the dissection device  600  in the deployed state configured in accordance with an embodiment of the present technology.  FIG. 6D  is an end view of the dissection device  600  shown in  FIG. 6C . Referring to  FIGS. 6C and 6D  together, to deploy the dissection device  600 , the pull rod  606  can be pulled proximally while the shaft  604  can remain relatively fixed. The proximal movement of the pull rod  606  pulls the distal portions of the arms  602   a ,  602   b  proximally and forces the arms  602   a ,  602   b  to bend outwardly away from the longitudinal axis of the shaft  604 . As shown in  FIG. 6D , the arms  602   a ,  602   b  can extend laterally generally within the same plane (e.g., the first and second arms  602   b  extend from the shaft  604  in first and second directions, respectively, that are 180 degrees or about 180 degrees of one another). In other embodiments, the arms  602   a  and  602   b  can extend at an angle θ with respect to one another that is between about 135 degrees and about 180 degrees. Such a configuration may be particularly advantageous if the desired dissection is within a curved surface, such as a vessel wall. 
       FIG. 7  is a top view of another embodiment of a dissection device  700  in a deployed state configured in accordance with the present technology. The dissection device  700  can have a shaft  704  and dissection arms  702   a ,  702   b  that are generally similar to the shaft  604  and dissections arms  602   a ,  602   b  of the dissection device  600  of  FIG. 6A . The dissection device  700  of  FIG. 7 , however, includes a smooth, deformable membrane  799  surrounding at least a portion of the arms  702   a ,  702   b . For example, the membrane can be made of silicone, urethane, nylon, latex, soft PEBAX, or any soft polymer or other suitable material. The membrane  799  reduces frictional forces between the dissection device  700  and the interior of the vessel wall, both during the initial insertion of the dissection device  700  into the wall, and during deployment within the wall. 
       FIG. 8A  is a side view of another embodiment of a dissection device  800  in a low-profile state,  FIG. 8B  is an end view of the dissection device  800  shown in  FIG. 8A , and  FIG. 8C  is an end view of the dissection device  800  in a deployed state. Referring to  FIGS. 8A-8C  together, the dissection device  800  can have a shaft  804  and a pull rod  806  that are generally similar to the shaft  604  and pull rod  606  of the dissection device  600  of  FIGS. 6A and 6B . The dissection device  800  of  FIGS. 8A-8C , however, has first and second dissection arms  802   a ,  802   b  that are configured to deploy at a non-180 degree angle (or multiples thereof) relative to one another. As shown in  FIGS. 8A-8C , the first and second dissection arms  802   a ,  802   b  can be positioned less than 180 degrees or less than about 180 degrees apart along the circumference of the pull rod  806  such that, when deployed, the first and second dissection arms  802   a ,  802   b  bend outwardly at angle relative to one another. 
       FIGS. 9A and 9B  illustrate another embodiment of a dissection device  900  configured in accordance with the present technology, shown in a low-profile state and a deployed state, respectively. The dissection device  900  can include an elongated shaft  904  and a pull rod  906  slidably disposed within the shaft  904 . The pull rod  906  can have an atraumatic distal end region  914 . The shaft  904  can have a distal portion  903  that includes dissection arms  902  and a distal end region  915 . In the embodiment shown in  FIGS. 9A and 9B , one or more regions of the shaft  904  have been removed along the distal portion  903  to form the dissection arms  902 . In other embodiments, the dissection arms  902  can be separate components coupled to the shaft  904 . The distal end region  915  of the shaft  904  can be fixed to the distal end region  914  of the pull rod  906 . As such, proximal movement of the pull rod  906  with respect to the elongated shaft  904  (as indicated by arrow A in  FIG. 9B ) pulls the distal portions of the dissection arms  902  proximally and forces the dissection arms  902  to bend outwardly away from the longitudinal axis of the shaft  904 , as shown in  FIG. 9B . 
     The dissection arms  902  can include one or more segments  901  (referred to individually as first and second segments  901   a ,  901   b ) and one or more joints  930  (referred to individually as first-third joints  930   a - c ). The joints  930  can be positioned along the dissection arms  902  between successive segments  901  and/or at the portions of the arms  902  that meet the shaft  904  (e.g., the proximal and distal end portions of the arms  902 ). The joints  930  can be portions of the dissection arms  902  and/or shaft  904  configured to preferentially flex relative to the segments  901  and/or the shaft  904 . In some embodiments, one or more of the joints  930  can be formed by opposing recesses  912  at a desired location along the arm  902  (e.g., a living hinge), and in other embodiments one or more of the joints  930  can be one or more small pins, elastic polymeric elements, mechanical hinges and/or other devices that enable one segment  901  to pivot or bend relative to another. 
     In the embodiment shown in  FIGS. 9A and 9B , each of the dissection arms  902  includes a distal joint  930   a  at its distal end portion, a proximal joint  930   c  at its proximal end portion, and an intermediate joint  930  positioned along the length of the respective arm  902  between the proximal and distal joints  930   a ,  930   c . In response to longitudinal stresses caused by proximal movement of the pull rod  906 , the dissection arms  902  deform into a predetermined shape biased by the configuration and/or relative positions of the joints  930 . For example, in the illustrated embodiment, each of the dissection arms  902 , when deployed, includes a generally curved distal segment  901   a  and a generally linear proximal segment  901   b  that, taken together, enclose a rounded triangular or “shield-like” shape. In other embodiments, the number of segments  901 , the length of each segment  901 , the angle between segments  901 , and/or the shape of each segment  901  (e.g., linear, curved, etc.) can be varied along a single dissection arm and/or amongst a plurality of dissection arms to achieve a desired dissection pocket DP and/or leaflet L shape (see  FIG. 2C ). Moreover, the dissection arms  902  can have any suitable size and/or shape based on a desired bending stiffness, angle, and radius of curvature. Additionally, the deployed shape of the dissection arms  902  and/or the amount of tissue separated by the dissection arms  902  may be adjusted by varying the distance traveled by the pull rod  906  in a proximal direction. 
     One method of using the dissection device  900  is now described with reference to  FIGS. 2A-2F . To begin, the dissection device  900  can first be intravascularly positioned adjacent a treatment site within a blood vessel V (e.g., a vein). The dissection device  900  is then advanced through an opening O ( FIG. 2A ) in an interior surface IS of the vessel wall W and positioned in a space S ( FIGS. 2A and 2B ) within the vessel wall W. While positioned within the vessel wall W, the pull rod  906  can be pulled proximally to flex or bend the dissection arms  902  outwardly away from the longitudinal axis of the shaft  904 . As the dissection arms  902  move outwardly, the dissection arms  902  push against the tissue at the inner periphery P of the space S, thereby separating the tissue at the periphery to enlarge the space S within the vessel wall W. The dissection arms  902  may continue to expand until a dissection pocket DP ( FIG. 2B ) having a desired shape and/or size is formed within the vessel wall W. In some embodiments, the dissection device  900  can be repositioned within the dissection pocket DP) and/or collapsed and re-deployed one or more times (while remaining within the dissection pocket DP) until a desired dissection pocket DP configuration is achieved. For example, repositioning the dissection device  900  can include moving the dissection device  900 , pull rod  906 , and/or shaft  904  axially and/or laterally within the dissection pocket DP, as well as rotating the dissection device  900  about its longitudinal axis within the dissection pocket DP. 
       FIG. 10  shows another embodiment of a dissection device  1000  configured in accordance with the present technology. The dissection device  1000  can include a shaft  1004 , a pull rod  1006 , and dissection arms  1002  that are generally similar to the shaft  904 , pull rod  906 , and dissection arms  902  of the dissection device  900  shown in  FIGS. 9A and 9B . For example, the dissection arms  1002  can include two segments  1001  (individually referred to as first and second segments  1001   a ,  1001   b ) and three joints  1030  (referred to individually as first-third joints  1030   a - c ). In contrast to the embodiment shown in  FIGS. 9A and 9B , each of the dissection arms  1002  of the dissection device  1000  includes a cutting element  1021  having a sharp edge  1025  configured to cut vessel wall tissue adjacent an opening O in the vessel wall (see  FIGS. 2C-2F ). For example, the dissection arms  1002  can individually include a blunt or atraumatic dissection surface along the lengths of the second or proximal-most segment  1001   b , and the cutting element  1021  projects from the respective segment  1001   b  perpendicular to the blunt dissection surface to which it is affixed. In some embodiments, the cutting elements  1021  can project from the surface of the respective dissection arm  1002  a distance of between about 0.2 mm and 2.0 mm. Additionally, the cutting elements  1021  can project a distance of between about 0.5 mm and about 1.5 mm. In a particular embodiment, the cutting element  1021  can project a distance of about 1 mm, or 1 mm. 
     The individual cutting elements  1021  can extend along all or a portion of the length of the respective second segment  1001   b  and/or dissection arm  1002 . In a particular embodiment, a proximal portion of each of the cutting elements  1021  is positioned adjacent to and/or abuts the shaft  1004  when the arms  1002  are in a deployed state. In some embodiments, the cutting elements  1021  can be integral with the dissection arms  1002 . In other embodiments, the cutting elements  1021  are separate components attached to the dissection arms  1002 . In such embodiments, each of the cutting elements  1021  can be soldered, welded, glued, or otherwise mechanically fixed to the corresponding dissection arm  1002 . For example, the proximal segments of the dissection arms  1002  may contain a slot along their respective lengths, and the corresponding cutting element  1021 , such as a sharpened blade, can be positioned in the slot and soldered, welded, or otherwise adhered into place. In some embodiments, the sharpened edge of each of the cutting elements  1021  faces away from the respective dissection arm  1002  within a dissection plane defined by the deployed dissection arms  1002 . In other embodiments, the dissection device  1000  is configured such that the sharpened portions of the cutting elements  1021  lie in a plane that makes an angle between 0 and 100 degrees with the dissection plane. Moreover, the shape and/or configuration of the dissection arms  1002  and/or cutting elements  1021  can be selected to achieve a desired cutting path of the cutting elements  1021 . 
     In one method of using the dissection device  1000 , the dissection device  1000  can be positioned within a space S within a blood and deployed to separate vessel wall tissue and create a dissection pocket DP as detailed above with respect to  FIGS. 9A-9B . With reference to  FIGS. 2A-2F , the deployed dissection device  1000  can then be pulled proximally within the dissection pocket DP such that the sharpened edges  1025  of the cutting elements  1021  engage and cut tissue at the proximal edge E of the dissection pocket DP, thereby widening the opening O into a mouth M and transforming the dissection pocket DP into a leaflet L ( FIGS. 2C-2F ). In other embodiments, the cutting elements  1021  can cut the tissue before and/or while the dissection arms  1002  are deployed. If desired, the dissection device  1000  may be repositioned after the dissection pocket DP has been created and before widening the opening O to better position the arms  1002  and/or cutting elements  1021  relative to the opening O. In certain procedures, it may be desirable to collapse and deploy the dissection device  1000  one or more times within the dissection pocket DP (with or without re-positioning the dissection device  1000 ) and/or pull the cutting elements  1021  proximally one or more times to accomplish a desired dissection pocket DP configuration and/or leaflet L configuration. 
       FIGS. 11A-11C  illustrate another embodiment of a dissection device  1100  configured in accordance with the present technology.  FIG. 11A  shows the dissection device  1100  in a collapsed or low-profile state, and  FIGS. 11B and 11C  show the dissection device  1100  in a first deployed state and a second deployed state, respectively. The dissection device  1100  can include an outer sleeve  1150 , an elongated shaft  1104  slidably disposed within the outer sleeve  1150 , and a pull rod  1106  slidably disposed within the elongated shaft  1104 . The pull rod  1106  can have an atraumatic distal end region  1114 . The elongated shaft  1104  can have a distal portion  1103 , dissection arms  1102  at the distal portion  1103 , and a distal end region  1115  coupled to the distal end region  1114  of the pull rod. In the embodiment shown in  FIGS. 11A and 11B , one or more regions of the shaft  1104  have been removed along the distal portion  1103  to form the dissection arms  1102 . The dissection arms  1102  can be similar to the arms  1002  of the dissection device  1000  shown in  FIG. 10 , except the arms  1102  have four joints  1130  (referred to individually as first-fourth joints  1130   a - 1130   d ) and three segments  1101  (individually labeled first-third segments  1101   a - 1101   c ). Additionally, each of the dissection arms  1102  include a cutting element  1121  extending outwardly along a length of the second or intermediate segment  1101   b . The cutting element  1121  can have a sharp edge  1125  along all or a portion of its length that is configured to cut vessel wall tissue. In the particular embodiment shown in  FIGS. 11A-11C , the third or proximal-most segment  1101   c  (shown only in  FIG. 11C ) does not include a cutting element. In other embodiments, the proximal-most segment and/or the third segment  1101   c  may also include a cutting element. 
     One method of using the dissection device  1100  will now be described with reference to  FIGS. 2A-2F . The dissection device  1100  can be intravascularly positioned adjacent a treatment site within a blood vessel V and advanced through an opening O ( FIG. 2A ) at an interior surface IS of a blood vessel wall W to be positioned in a space S within the wall W. While positioned in the space S, the dissection device  1100  is configured to (1) transform from the low-profile state ( FIG. 11A ) to the first deployed state ( FIG. 11B ) to create a dissection pocket DP within a vessel wall ( FIGS. 2C and 2D ), and (2) transform from the first deployed state to the second deployed state ( FIG. 11C ) to widen the opening O ( FIGS. 2C-2F ) into a mouth M ( FIGS. 2E and 2F ), thereby transforming the dissection pocket DP into a leaflet L ( FIGS. 2E and 2F ). To transform the dissection arms  1102  from the low-profile state to the first deployed state, the pull rod  1106  is pulled proximally relative to the outer sleeve  1150  and shaft  1104  (as indicated by arrow A 1 ), thereby forcing the arms  1102  to flex or bend outwardly away from the longitudinal axis of the shaft  1104  such that the sharp edges  1125  of the cutting elements  1121  along the second segments  1101   b  face proximally. As the pull rod  1106  is pulled proximally, the outer sleeve  1150  remains positioned over the proximal-most or third segments  1101   c  of the arms  1102 , thereby preventing the third segments  1101   c  from deploying. Accordingly, proximal movement of the pull rod  1106  only deploys the non-constrained first and second segments  1101   a ,  1101   b . As such, the resulting dissection pocket DP ( FIGS. 2C and 2D ) can have a shape defined by an outline of only the first and second segments  1101   a ,  1101   b.    
     After forming the dissection pocket DP having a desired shape and size, the outer sleeve  1150  can be retracted as indicated by arrow A 2  ( FIG. 11C ) to fully deploy the third or proximal-most segments  1101   c , thereby transforming the dissection device  1100  from the first deployed state to the second deployed state. Releasing the third segments  1101   c  from the outer sleeve  1150  causes the proximal ends of the second segments  1101   b  to swing outwardly away from the longitudinal axis of the shaft  1104  such that a longitudinal dimension of the second segments  1101   b  are generally parallel to a longitudinal dimension of the pull rod  1106  and the sharp edges  1125  of the cutting elements  1121  face laterally away from a longitudinal axis of the shaft  1104 . For example, the shaft  1104  and/or arms  1102  can be made of a superelastic and/or shape memory material (e.g., Nitinol) that is heat set during manufacturing to form a predetermined deployed shape. As the second segments  1101   b  move away from the shaft  1104 , the sharp edges  1125  of the cutting elements  1121  engage the vessel wall tissue surrounding the opening O and cut the tissue laterally away from either side of the opening O along the proximal edge E of the dissection pocket DP (see arrows A in  FIG. 2C ), thereby widening the opening O into a mouth M ( FIGS. 2E and 2F ) to transform the dissection pocket DP into a leaflet L. If desired, the dissection device  1100  may be repositioned after the dissection pocket DP has been created and before widening the opening O to better position the arms  1102  and/or cutting elements  1102  relative to the opening O. 
     In certain procedures, it may be desirable to transition back and forth between the first deployed state and the second deployed state (with or without re-positioning the dissection device  1100 ) to accomplish a desired dissection pocket DP and/or leaflet L configuration. To transform the dissection device  1100  from the second deployed state to the first deployed state, a clinician can (1) push the pull rod  1106  distally while holding the shaft  1104  and the outer sleeve  1150  stationary relative to the pull rod  1106  to force the dissection arms  1102  to collapse towards the pull rod  1106 , (2) advance the outer sleeve  1150  distally over the third segments  1101   c , and (3) pull the pull-rod  1106  distally to re-deploy the first and second segments  1101   a ,  1101   b  of the arms  1102 . 
     In some embodiments, the dissection device  1100  does not include an outer sleeve  1150 . In such embodiments, the third or proximal-most segments  1101   b  of the dissection arms  1102  are non-constrained or otherwise free to bend outwardly away from the longitudinal axis of the shaft  1104  as the pull rod  1106  is moved proximally relative to the shaft  1104 . Accordingly, the dissection device  1100  transitions directly from the low-profile state of  FIG. 11A  to the deployed state shown in  FIG. 11C , thereby (1) enlarging the space S ( FIGS. 2A-2B ) to form a dissection pocket DP ( FIGS. 2C-2D ) and (2) widening the opening O (cutting tissue outwardly) to form the mouth M in a single step. 
       FIGS. 12A-12C  illustrate another embodiment of a dissection device  1200  configured in accordance with the present technology, shown in a first, second, and third deployed state, respectively. The dissection device  1200  can include an outer sleeve  1250 , an elongated shaft  1204  slidably disposed within the outer sleeve  1250 , an inner shaft  1240  slidably disposed within the elongated shaft  1204 , and a pull rod  1206  slidably disposed within the inner shaft  1240 . The pull rod  1206  can have an atraumatic distal end region  1214 . The elongated shaft  1204  can have a distal portion  1203 , dissection arms  1202  at the distal portion  1203 , and a distal end region  1215  coupled to the distal end region  1215  of the pull rod  1206 . In the embodiment shown in  FIGS. 12A and 12B , one or more regions of the shaft  1204  at the distal portion  1203  have been removed to form the arms  1202 . In other embodiments, the arms  1202  can be separate components coupled to the shaft  1204  at the distal portion  1203 . The arms  1202  can be similar to the arms  1102  of the dissection device  1000  shown in  FIGS. 11A-11C . For example, the arms  1202  can include four joints  1230  (referred to individually as first-fourth joints  1230   a - 1230   d ) and three segments  1201  (individually labeled first-third segments  1201   a - 1201   c ). Additionally, each of the arms  1202  include a cutting element  1221  extending outwardly along a length of the second or intermediate segment  1201   b.    
     In the embodiment shown in  FIGS. 12A-12C , the inner member  1140  includes two pairs of struts  1242  (only one pair visible in  FIGS. 12A-12C ) configured to pivot about the inner shaft  1240 . Each of the struts  1242  can have a distal portion  1244  coupled to the inner shaft  1240  and a proximal portion  1246  ( FIG. 12C ) coupled to a respective arm  1202 . In the illustrated embodiment of the dissection device  1200 , the proximal portion  1246  of each of the struts  1242  is fixed to a respective third joint  1230   c . In some embodiments, the proximal portion  1246  of each of the struts  1242  includes a tab configured to mate with a slot on a corresponding dissection arm  1202 . In other embodiments, the struts  1242  can be coupled to the dissection arms  1202  via other suitable mechanical coupling devices. 
     In use, the dissection device  1200  is configured to: (1) transform from the low-profile state (not shown) to the first deployed state ( FIG. 12A ) to create a dissection pocket DP within a vessel wall V ( FIGS. 2C and 2D ), (2) transform from the first deployed state to the second deployed state ( FIG. 12B ), and (3) transform from the second deployed state to the third deployed state ( FIG. 12C ) to widen the opening O into a mouth M ( FIGS. 2C-2F ), thereby transforming the dissection pocket DP into a leaflet L ( FIGS. 2E and 2F ). To transform the dissection arms  1202  from the low-profile state to the first deployed state, the pull rod  1206  is pulled proximally relative to the outer sleeve  1250 , the shaft  1204 , and the inner member  1240  (as indicated by arrow A 1  in  FIG. 12A ), thereby forcing the arms  1202  to bend outwardly away from the longitudinal axis of the shaft  1204 . The outer sleeve  1250  remains positioned over the proximal-most or third segments  1201   c  of the arms  1202  as the pull rod  1206  moves proximally, thereby preventing the third segments  1201   c  from deploying. Accordingly, only the non-constrained first and second segments  1201   a ,  1201   b  deploy to form the dissection pocket DP within the vessel wall. 
     After forming the dissection pocket DP having a desired geometry, the outer sleeve  1250  can be retracted as indicated by arrow A 2  ( FIG. 12B ) to expose the proximal-most or third segments  1101   c , thereby transforming the dissection device  1200  from the first deployed state to the second deployed state. Once the third segments  1201   c  have been exposed, the inner shaft  1240  can be pulled proximally as indicated by arrow A 3  ( FIG. 12C ) relative to the pull rod  1206  and shaft  1204 . As the inner shaft  1204  moves proximally, the proximal portion  1246  of the struts  1242  extend away from the longitudinal axis of the inner shaft  1240  and push the third joints  1230   c  outwardly. Pushing the third joints  1230   c  outwardly swings the cutting elements  1221  laterally away from the longitudinal axis of the inner shaft  1240  to engage and cut the vessel wall tissue adjacent the opening O, thereby widening the opening O into a mouth M ( FIGS. 2C-2F ) to create a leaflet L from the dissection pocket DP. If desired, the dissection device  1200  may be repositioned after the dissection pocket DP has been created and before widening the opening O to better position the arms  1202  and/or cutting elements  1221  relative to the opening O. 
     In certain procedures, it may be desirable to transition back and forth between the first, second, and/or third deployed states (with or without re-positioning the dissection device  1200 ) to accomplish a desired dissection pocket DP and/or leaflet L configuration. To transform the dissection device  1200  from the third deployed state to the second deployed state, a clinician can push the inner shaft  1240  distally while holding the shaft  1204 , outer sleeve  1250 , and pull rod  1206  stationary relative to the inner shaft  1240  to force the proximal portions  1246  of the struts  1242  to collapse towards the inner shaft  1240 . To transform the dissection device  1200  from the second deployed state to the first deployed state, a clinician can advance the outer sleeve  1250  distally over the third segments  1202   c.    
     In some embodiments, the dissection device  1200  does not include the outer sleeve  1250 , and the third segments  1202   c  remain exposed as the pull rod  1206  is retracted to deploy the first and second segments  1202   a - b . In such embodiments, the dissection device  1200  transitions directly from the low-profile state of  FIG. 12A  to the deployed state shown in  FIG. 12C , thereby (1) enlarging the space S ( FIGS. 2A-2B ) to form a dissection pocket DP ( FIGS. 2C-2D ) and (2) widening the opening O (cutting tissue outwardly) to form the mouth M in a single step. It will be appreciated that, regardless of whether the arms  1202  are configured to bend away from the shaft  1204  automatically or with the help of the struts  1242 , it may be beneficial to include the struts  1242  as an additional deployment option and/or to fortify one or more of the joints  1230 . Moreover, although the dissection device  1200  described with reference to  FIGS. 12A-12C  includes two pairs of struts  1242  (four struts total), in other embodiments the dissection device  1200  can include more or fewer total struts  1242  and/or more or fewer struts  1242  per arm  1202  (e.g., one strut  1242  per arm  1202 , etc.). 
     In some embodiments of the present technology, the dissection device can include a separate cutting device. For example,  FIGS. 13A and 13B  show one embodiment of a dissection device  1300  configured in accordance with the present technology that is configured to receive a separate cutting device  1360  (only a portion shown in  FIGS. 13A and 13B ).  FIGS. 13A and 13B  show the dissection device  1300  in distal and proximal deployed states, respectively. The dissection device  1300  includes an elongated shaft  1304  and a pull member  1306  slidably disposed within the shaft  1304 . The pull member  1306  can be a hollow tubular structure having a distal end region  1314 , and the cutting device  1360  can be configured to be slidably disposed within a lumen of the pull member  1306 . The elongated shaft  1304  can have a distal portion  1303 , dissection arms  1302  at the distal portion  1303 , and a distal end region  1315  coupled to the distal end region  1314  of the pull member  1306 . 
     In the embodiment shown in  FIGS. 13A and 13B , one or more regions of the shaft  1304  at the distal portion  1303  have been removed to form the dissection arms  1302 . As such, the dissection arms  1302  can be continuous and/or integral with the shaft  1304 . In other embodiments, dissection arms  1302  can be separate components coupled to the distal portion  1303  of the shaft  1304 . The arms  1302  can include three joints  1330  (referred to individually as first-third joints  1330   a - 1330   c ) and two segments  1301  (individually labeled first and second segments  1301   a ,  1301   b ). 
     The elongated shaft  1304  can further include two slots  1334  along at least a portion of its length. (Only one slot  1334  is visible in  FIGS. 13A and 13B .) In some embodiments, the slots  1334  can be positioned at circumferentially opposing portions of the shaft  1304 . In other embodiments, the slots  1334  can have other suitable spacing about the circumference of the shaft  1304 . In the embodiment shown in  FIGS. 13A and 13B , each of the slots  1334  extend distally along the shaft  1304  to the second or proximal-most segment  1301   b  of a respective arm  1302 . In other embodiments, the slots  1334  may extend to other locations along the shaft  1304  and/or corresponding arm  1302 , such as a location distal to the second or proximal-most segment  1301   b.    
     The pull member  1306  can also include two slots  1336  along at least a portion of its length. (Only portions of one slot are visible in  FIGS. 13A and 13B .) In some embodiments, the slots  1336  can be positioned at circumferentially opposing portions of the pull member  1306 . In other embodiments, the slots  1336  can have other suitable spacing about the circumference of the pull member  1306 . In the embodiment shown in  FIGS. 13A and 13B , each of the slots  1336  extend distally along the pull member  1306  to a location that is distal to a portion of the pull member  1306  longitudinally aligned with a proximal end of the corresponding arm  1302  in the deployed state. The pull member  1306  can be positioned within the shaft  1304  such that the slots  1336  along the pull member  1306  circumferentially align with the slots  1334  along the shaft  1304 . 
       FIG. 13C  is an isolated view of the cutting device  1360 . The cutting device  1360  can include an elongated shaft  1364 , two cutting elements  1321  coupled to a distal region of the shaft  1364 , and an actuator  1312  extending through at least a portion of the shaft  1364 . Each of the cutting elements  1321  can have a sharp edge  1325  configured to cut vessel wall tissue. The elongated shaft  1364  can further include an aperture  1367  at its distal region, and can terminate distally at a rounded or atraumatic distal tip portion  1317  (also visible in  FIG. 13A ). The aperture  1367  can have lateral openings  1324  (only one visible in  FIG. 13C ). The cutting elements  1321  can be rotatably coupled to the shaft  1364  by a first linkage  1369  and configured to pivot or rotate about the first linkage  1369  between a low-profile or collapsed state (not shown) and a deployed state in which the cutting elements  1321  extend outwardly away from a longitudinal axis of the shaft  1364  in a distal direction. In the embodiment shown in  FIG. 13C , the first linkage  1369  is a pin that extends from the elongated shaft  1364  across the aperture  1367  through a slot in each of the cutting elements  1321 . In other embodiments, the cutting elements  1321  can be coupled to the shaft  1364  by other suitable mechanical linkages. The cutting elements  1321  can be coupled to a distal portion of the actuator  1312  by a second linkage (not visible in  FIG. 13C ). In the embodiment shown in  FIG. 13C , the second linkage is a pin that extends from the actuator  1312  through a thickness of each of the cutting elements  1321 . In other embodiments, the cutting elements  1321  can be coupled to the actuator  1312  by other suitable mechanical linkages. The first linkage  1369  can be fixed relative to the elongated shaft  1364 , while the second pin can move axially relative to the shaft  1364 . 
     In the low-profile state (not shown), the cutting elements  1321  can be generally aligned with the elongated shaft  1364  such that the majority of each cutting element  1321  lies within the lateral boundaries of the elongated shaft  1364 . In some embodiments, each of the cutting elements  1321  in their entireties lies within the lateral boundaries of the elongated shaft  1364 . Moreover, in the low-profile state, a portion of each slot (not shown) in the cutting elements  1321  can be aligned. To deploy the cutting device  1360 , the actuator  1312  can be pushed distally (e.g., from the proximal portion), thereby urging the cutting elements  1321  in a distal direction. As the cutting elements  1321  are urged distally, the individual slots slide along the first linkage  1369 , thereby forcing the cutting elements  1321  to rotate based on the shape of each slot (similar to the mechanism of action detailed with respect to  FIGS. 3A-3D ). As the cutting elements  1321  rotate, they extend laterally through the openings  1324  in the elongated shaft  1364 . In other embodiments, the cutting device  1360  can be configured such that proximal movement of the actuator  1312  can deploy the cutting elements  1321 . 
     The cutting device  1360  can be positioned within the pull member  1306  such that the cutting elements  1321  are circumferentially aligned with the slots  1334 ,  1336  along the shaft  1304  and pull member  1306 , respectively. Accordingly, when the cutting elements  1321  are in the deployed state, the cutting elements  1321  extend outwardly through the slots  1334 ,  1336  away from the longitudinal axis of the shaft  1364 . The cutting elements  1321  can extend from the shaft  1364  in a distal direction such that the cutting elements  1321  are angled with respect to the longitudinal axis of the shaft  1364 . In the embodiment shown in  FIGS. 13A and 13B , the sharp edges  1325  of the cutting elements  1321  face proximally when the cutting elements  1321  are in a deployed state. In other embodiments, the sharp edges  1325  can face distally when the cutting elements  1321  are in a deployed state. 
     One method of using the dissection device  1300  will now be described with reference to  FIGS. 2A-2F . The dissection device  1300  is first advanced through an opening O in a vessel wall W and positioned within an access space S ( FIGS. 2A and 2B ). The pull member  1306  can be pulled proximally relative to the elongated shaft  1304  and the cutting device shaft  1364  to bend the arms  1302  away from the longitudinal axis of the shaft  1304  to form a dissection pocket DP ( FIGS. 2C and 2D ). The cutting device  1360  can then be advanced and/or otherwise positioned within the pull member  1306  in a low-profile state (not shown) such that the cutting elements  1321  are adjacent a distal portion of the slot  1336 . The cutting device  1360  is then actuated to pivot the cutting elements  1321  into the deployed state, away from the longitudinal axis of the pull member  1306 . As shown in  FIG. 13A , the cutting elements  1321  can deploy within an interior region defined by the deployed arms  1302  (e.g., within the dissection pocket DP). The shaft  1364  of the cutting device  1360  can then be pulled proximally relative to the shaft  1304  and the pull member  1306  to pull the cutting elements  1321  through the slots  1334  along the second or proximal-most segments  1301   b  of the dissection arms  1302 . As the cutting elements  1321  pass through the slots  1334  in the respective arms  1302 , all or a portion of the length of each sharp edge  1325  engages and cuts tissue adjacent the opening O in the vessel wall W to form a mouth M ( FIGS. 2C-2F ). In some embodiments, the degree of rotation of the cutting elements  1321  and/or the angle at which the cutting elements  1321  extend from the shaft  1364  can be adjusted depending on the length or shape of the mouth M desired. Likewise, the distance the shaft  1364  is pulled proximally can also be varied to achieve a desired length or shape of the mouth M. 
       FIGS. 14A and 14B  are isometric views of another embodiment of a dissection device  1400  configured in accordance with the present technology, shown at various stages of deployment. The dissection device  1400  can be generally similar to the dissection device  1300  shown in  FIGS. 13A and 13B . For example, the dissection device  1400  can include an elongated shaft  1404 , dissection arms  1402 , a pull member  1406 , a cutting device  1460 , and cutting elements  1421  similar to the shaft  1304 , arms  1302 , pull member  1306 , cutting device  1360 , and cutting elements  1321  respectively, of  FIGS. 13A and 13B . The cutting device  1460  of the dissection device  1400  of  FIGS. 14A and 14B , however, is configured such that, when the cutting elements  1421  are in the deployed state, the cutting elements  1421  extend outwardly from the pull member  1406  in a distal direction such that the cutting elements  1421  are angled with respect to the longitudinal axis of the pull member  1406 . In the embodiment shown in  FIGS. 14A and 14B , the cutting elements  1421  include sharp edges  1425  that face proximally when the cutting elements  1421  are in a deployed state. In other embodiments, the sharp edges  1425  can face distally when the cutting elements  1421  are in a deployed state. 
       FIG. 14C  is an isolated view of a variation of the cutting device  1460  shown in  FIGS. 14A and 14B . The cutting device  1460  can include an elongated shaft  1464 , two cutting elements  1421  coupled to a distal region of the shaft  1464 , and an actuator  1412  (not shown in  FIGS. 14A and 14B ) extending through at least a portion of the shaft  1464 . Each of the cutting elements  1421  can have a sharp edge  1425  configured to cut vessel wall tissue. The elongated shaft  1464  can further include an aperture  1467  at its distal region, and can terminate distally at a rounded or atraumatic distal tip portion  1417  (also visible in  FIG. 14B ). The aperture  1467  can have lateral openings  1424  (only one visible in  FIG. 14C ). The cutting elements  1421  can be rotatably coupled to the shaft  1464  by a first linkage  1469  positioned at or near a distal end of the shaft  1464 . The cutting elements  1421  can be configured to pivot or rotate about the first linkage  1469  between a low-profile or collapsed state (not shown) and a deployed state in which the cutting elements  1421  extend outwardly away from a longitudinal axis of the shaft  1464 . In the embodiment shown in  FIGS. 14A and 14B , the cutting elements  1421  extend outwardly perpendicular to the shaft  1404  and/or slightly in a distal direction, while in  FIG. 14C , the cutting elements  1421  extend outwardly away from the shaft  1464  in a proximal direction. However, in the embodiment shown in  FIGS. 14A and 14B  and the embodiment shown in  FIG. 14C , the sharp edges  1425  faces in a distal direction when the cutting elements  1421  are in a deployed state. 
     In the embodiment shown in  FIG. 14C , the first linkage  1469  is a pin that extends from the elongated shaft  1464  across the aperture  1467  through a slot in each of the cutting elements  1421 . In other embodiments, the cutting elements  1421  can be coupled to the shaft  1464  by other suitable mechanical linkages. The cutting elements  1421  can be coupled to a distal portion of the actuator  1412  by a second linkage (not visible in  FIG. 14C ). In the embodiment shown in  FIG. 14C , the second linkage is a pin that extends from the actuator  1412  through a thickness of each of the cutting elements  1421 . In other embodiments, the cutting elements  1421  can be coupled to the actuator  1412  by other suitable mechanical linkages. The first linkage  1469  can be fixed relative to the elongated shaft  1464 , while the second pin can move axially relative to the shaft  1464 . 
     In the low-profile state (not shown), the cutting elements  1421  can be generally aligned with the elongated shaft  1464  such that the majority of each cutting element  1421  lies within the lateral boundaries of the elongated shaft  1464 . In some embodiments, each of the cutting elements  1421  in their entireties lies within the lateral boundaries of the elongated shaft  1464 . Moreover, in the low-profile state, a portion of each slot (not shown) in the cutting elements  1421  can be aligned. To deploy the cutting device  1460 , the actuator  1412  can be pushed distally (e.g., from the proximal portion), thereby urging the cutting elements  1421  in a distal direction. As the cutting elements  1421  are urged distally, the individual slots slide along the first linkage  1469 , thereby forcing the cutting elements  1421  to rotate based on the shape of each slot (similar to the mechanism of action detailed with respect to  FIGS. 3A-3D ). As the cutting elements  1421  rotate, they extend laterally through the openings  1424  in the elongated shaft  1464 . In other embodiments, the cutting device  1460  can be configured such that proximal movement of the actuator  1412  can deploy the cutting elements  1421 . 
     The cutting device  1460  can be positioned within the pull member  1406  such that the cutting elements  1421  are circumferentially aligned with the slots  1434 ,  1436  along the shaft  1404  and pull member  1406 , respectively. Accordingly, when the cutting elements  1421  are in the deployed state, the cutting elements  1421  extend outwardly through the slots  1434 ,  1436  away from the longitudinal axis of the shaft  1464 . The cutting elements  1421  can extend from the shaft  1464  in a distal direction such that the cutting elements  1421  are angled with respect to the longitudinal axis of the shaft  1464 . In the embodiment shown in  FIGS. 14A and 14B , the sharp edges  1425  of the cutting elements  1421  face proximally when the cutting elements  1421  are in a deployed state. In other embodiments, the sharp edges  1425  can face distally when the cutting elements  1421  are in a deployed state. 
     In one method of use, the dissection device  1400  can be advanced through an opening O in a vessel wall W and positioned within an access space S ( FIG. 2A ). The pull member  1406  can be pulled proximally relative to the elongated shaft  1204  and the cutting device shaft  1464  to bend the arms  1402  away from the longitudinal axis of the shaft  1404  and separate tissue within the vessel wall to form a dissection pocket DP ( FIG. 2B ). The cutting device  1460  can then be advanced and/or otherwise positioned within the pull member  1406  in a low-profile state (not shown) such that the cutting elements  1421  are adjacent a portion of the slots  1434 ,  1436  that are proximal to the second or proximal-most segments  1401   b  of the dissection arms  1402  in the deployed state. The members  1423  of the cutting device  1460  can then be actuated to rotate or pivot the cutting elements  1421  into the deployed state, away from the longitudinal axis of the pull member  1406 . As shown in  FIG. 14A , the cutting elements  1421  can deploy outside of an interior region defined by the deployed arms  1402  (e.g., outside the dissection pocket DP). The shaft  1464  of the cutting device  1460  can then be pushed distally relative to the shaft  1404  and the pull member  1406  (indicated by arrow A in  FIG. 14B ) to push the cutting elements  1421  through the slots  1434  along the second or proximal-most segments  1401   b  of the dissection arms  1402 . As the cutting elements  1421  pass through the slots  1434  in the respective arms  1402 , all or a portion of the length of each sharp edge  1425  engages tissue along the proximal edge E the dissection pocket DP ( FIGS. 2C-2D ) from outside the dissection pocket DP, while the second or proximal-most segments  1401   b  of the dissection arms  1402  support tissue at or adjacent the proximal edge E from inside the dissection pocket DP. Each of the sharp edges  1425  move distally through the slots  1434  and cut the tissue extending laterally from the opening O, thereby forming a mouth M ( FIGS. 2C-2F ). In some embodiments, the degree of rotation of the cutting elements  1421  and/or the angle at which the cutting elements  1421  extend from the shaft  1464  can be adjusted depending on the length or shape of the mouth M desired. Likewise, the distance the shaft  1464  is pulled proximally can also be varied to achieve a desired length or shape of the mouth M. 
       FIGS. 15A and 15B  illustrate a further embodiment of a dissection device  1500  configured in accordance with another embodiment of the present technology.  FIGS. 15A and 15B  show the dissection device  1500  in a low-profile state and a deployed state, respectively. The dissection device  1500  can include an outer shaft  1551  and an inner shaft  1504  slidably disposed within the outer shaft  1504 . The outer shaft  1551  can have a distal portion  1553  and two longitudinal slots  1555  (only one visible in  FIGS. 15A and 15B ) extending along a length of the distal portion  1553 . The inner shaft  1504  can have a distal portion  1503 , dissection arms  1502  at the distal portion  1502 , and a tapered distal region  1513 . In the embodiment shown in  FIGS. 15A and 15B , one or more regions of the inner shaft  1504  have been removed at the distal portion  1503  to form the dissection arms  1502 . 
     The inner shaft  1504  and the outer shaft  1551  can be coupled at their respective distal regions, and the inner shaft  1504  can be positioned within the outer shaft  1551  such that the dissection arms  1502  circumferentially align with the slots  1553  in the outer shaft  1551 . Proximal movement of the outer shaft  1551  with respect to inner shaft  1504  (as indicated by arrow A in  FIG. 15B ) pulls the distal portions of the dissection arms  1502  proximally and forces the dissection arms  1502  to bend outwardly away from the longitudinal axis of the inner shaft  1504  through the respective slots  1555  in the outer shaft  1551 . 
     Because the dissection device  1500  does not include a pull member, a central lumen of the shaft  1504  can be used to house and/or deliver one or more additional devices, such as, for example, a separate cutting device (e.g., the cutting device  1360  of  FIGS. 13A and 13B , the cutting device  1460  of  FIGS. 14A and 14B , etc.), an inner dilator and/or a guide member (e.g., a guide wire, a guide needle, etc.). For example, in some embodiments, the dissection device  1500  can be positioned over an inner dilator and/or guide member and advanced to a desired dissection location within a vessel wall. Once the dissection device  1500  is positioned, the inner dilator and/or guide member may be withdrawn and replaced with a cutting device (e.g., the cutting device  1360  of  FIGS. 13A and 13B , the cutting device  1460  of  FIGS. 14A and 14B , etc.). In such embodiments, the cutting device can include a distal portion configured to mate with a distal portion of the dissection device (e.g., via a spring latch, a press fit, a screw fit, etc.). Accordingly, proximal movement of the cutting device relative to the inner and outer shafts  1504 ,  1551  of the dissection device  1504  can deploy the dissection arms  1502 . In other embodiments, the dissection device  1504  does not include an outer shaft  1551 . 
       FIGS. 16A and 16B  show another embodiment of a dissection device  1600  configured in accordance with the present technology. The dissection device  1600  can include an elongated shaft  1604 , a pull rod  1606  slidably disposed within the elongated shaft  1604 , and a separate cutting device  1660  configured to be slidably disposed over at least a portion of the shaft  1604 . In some embodiments, the cutting device  1660  may be positioned between shaft  1604  and pull rod  1606 . The pull rod  1606  can have an atraumatic distal end region  1614 . The shaft  1604  can have a distal portion  1603  ( FIG. 16A ), dissection arms  1602  at the distal portion  1603 , and a distal end region  1615  coupled to the distal end region  1614  of the pull rod  1606 . In the embodiment shown in  FIGS. 16A and 16B , one or more regions of the shaft  1604  have been removed along the distal portion  1603  to form the dissection arms  1602 . In other embodiments, the dissection arms  1602  can be separate components coupled to the shaft  1604 . Proximal movement of the pull rod  1606  with respect to the elongated shaft  1604  pulls the distal portions of the dissection arms  1602  proximally and forces the dissection arms  1602  to bend outwardly away from the longitudinal axis of the shaft  1604 , as shown in  FIGS. 16A and 16B . 
     The dissection arms  1602  can include one or more segments  1601  (referred to individually as first-third segments  1601   a - c ) and one or more joints  1630  (referred to individually as first-fourth joints  1630   a - d ) configured to preferentially flex relative to the segments  1601  and/or the shaft  1604 . The elongated shaft  1604  can further include two slots  1634  along at least a portion of its length. In some embodiments, the slots  1634  can be positioned at circumferentially opposing portions of the shaft  1604 . In other embodiments, the slots  1634  can have other suitable spacing about the circumference of the shaft  1604 . In the embodiment shown in  FIGS. 16A and 16B , each of the slots  1634  extend distally along the shaft  1604  to the second segment  1601   b  of the corresponding arm  1602 . In other embodiments, the slots  1634  may extend to other locations along the shaft  1604  and/or corresponding arm  1602 , such as a location distal or proximal to the second segment  1601   b.    
       FIG. 17  is an isolated view of the cutting device  1660 . The cutting device  1660  can include an elongated shaft  1664  (only a portion shown) configured to be positioned over the shaft  1604 . The shaft  1664  can have a bifurcated distal portion  1663 . The bifurcations of the distal portion  1663  can form two arms  1662 . In other embodiments, the arms  1662  are separate components coupled to the shaft  1664  via a hinge joint, a solder, a weld, or other suitable attachment means. In a particular embodiment, the arms  1662  can include one or more joints (not shown) along their lengths (e.g., at a proximal end portion) that bias the arms  1662  to preferentially flex when deployed. 
     The cutting device  1660  can be positioned over the shaft  1604  such that the arms  1662  circumferentially align with the dissection arms  1602 . Each of the arms  1662  can include a coupling element  1672 , such as a tab or protrusion, that extends around at least a portion of the circumference of the respective dissection arm  1602 , thereby securing each of the arms  1662  to a respective dissection arm  1602  and ensuring that a cutting element  1621  of the arms  1662  extends through the slot  1634  in the respective dissection arm  1602 . Each of the coupling elements  1672  can be configured to slide along at least a portion of the respective dissection arm  1602 . In other embodiments, the coupling elements  1672  can be a component of the dissection arms  1602 , and in yet other embodiments, the coupling elements  1672  are separate components from both the cutting device  1660  and the dissection arms  1602 . 
     As shown in  FIG. 17 , each of the arms  1662  can include a cutting element  1621 , such as a sharpened blade. For example, in the embodiment shown in  FIG. 17 , each of the arms  1662  has a slot  1665  along a portion of its respective distal region, and the corresponding cutting element  1621  is fixed within the slot  1665  (e.g., via soldering, welding, glue, a press fit, etc.). In other embodiments, one or more of the cutting elements  1621  can be integral with the arms  1662 . In a deployed state, the cutting elements  1621  can extend distally from the shaft  1664  at an angle. Each of the cutting elements  1621  can have a sharp edge  1625  configured to cut vessel wall tissue. The cutting elements  1621  can be positioned such that, when the cutting device  1660  is in a low-profile state, the sharp edges  1625  face radially inwardly. 
     The cutting device  1660  can be positioned over the shaft  1604  such that the arms  1602  and/or cutting elements  1621  circumferentially align with the slots  1634  along the shaft  1604 . Accordingly, in use the cutting device  1660  can be pushed distally over the shaft  1604 . As the arms  1662  are advanced distally over the deployed arms  1602 , the arms  1662  are forced to bend outwardly away from the longitudinal axis of the shaft  1664  to conform to the deployed shape of the third or proximal-most segment  1601   c  of the dissection arms  1602 . The sharp edge  1625  of the cutting element  1621  slides along the slot  1634  in the respective arm  1602  and projects through the slot  1634  to engage and cut vessel wall tissue. 
       FIGS. 18-20  are side views of cutting devices having different cutting elements configured in accordance with the present technology. For example,  FIG. 18  shows a cutting device  1860  having arms  1862  and a cutting element  1821  coupled to each arm  1862 . Each cutting element  1821  has a curved sharp edge  1825 . The distance which the cutting element  1821  extends from the arm  1862  varies along the length of the cutting element  1821 .  FIG. 19  illustrates another embodiment of a cutting device  1960  having arms  1962  and a cutting element  1921  coupled to each arm  1962 . Each cutting element  1921  can include a leading point and a sharp edge  1925  that faces distally. The cutting element  1921  is configured such that the sharp edge  1925  slides under the tissue to be cut.  FIG. 20  shows a further embodiment of a cutting device  2060  having arms  2062  and a triangular cutting element  2021  coupled to each arm  2062 . Each cutting element  2021  can include sharp edge  2025 . A point of the triangular cutting element  2021  is configured to pierce tissue, then cut the tissue as it slides along the tissue. 
       FIG. 21A  is a perspective, partial cross-sectional side view of a dissection device  2100  in a deployed state having tensioning members  2182  configured in accordance with the present technology.  FIG. 21B  is an end view of the dissection device  2100  shown in  FIG. 21A . Referring to  FIGS. 21A-21B  together, the dissection device  2100  can include an outer shaft  2104  (e.g., a hypotube), an inner shaft  2184  (e.g., a hypotube) slidably disposed within at least a portion of the outer shaft  2104 , and a pull member  2106  slidably disposed within at least a portion of the inner shaft  2184 . The outer shaft  2104  has a proximal portion (not shown) and a distal portion  2115 , and the inner shaft  2184  has a proximal portion (not shown) and a distal portion  2125 . The outer shaft  2104 , the inner shaft  2184 , and the pull member  2106  can be coaxially aligned and coupled at an atraumatic distal tip  2106  (e.g., via an adhesive, solder, a weld, or other suitable mechanical fixation devices). 
     The dissection device  2100  can further include one or more dissection arms  2102  extending distally from the outer shaft  2104  and one or more tensioning arms  2182  extending distally from the inner shaft  2184 . In one embodiment, the dissection arms  2102  are formed from portions of the outer shaft  2104 , and the tensioning arms  2182  are formed from portions of the inner shaft  2184 . The dissection arms  2102  can alternatively be separate components attached to the outer shaft  2104 , and/or the tensioning arms  2182  can be separate components attached to the inner shaft  2184 . Additionally, in some embodiments (not shown), the dissection arms  2102  can be coupled to the inner shaft  2184  while the tensioning arms  2182  can be coupled to the outer shaft  2104 . Upon axial movement of the outer shaft  2104 , the inner shaft  2184 , and/or the pull member  2106  relative to one another, one or more of the dissection arms  2102  and/or tensioning arms  2182  can extend radially outwardly from a longitudinal axis L of the dissection device  2100  to create a dissection pocket within a vessel wall, as described in greater detail below. 
     The outer shaft  2104  and the dissection arms  2102  together can define a dissection unit, and they can be made from stainless steel, Nitinol, PEEK and other generally suitable materials with sufficient stiffness and bending characteristics (e.g., elastic or super elastic) that can impart the desired forces. The dissection arms  2102  can be spaced apart about the circumference of the outer shaft  2104  such that, in a low-profile state (see  FIG. 22A ), the distal portion  2115  of the outer shaft  2104  includes a plurality of openings between the dissection arms  2102  that extend along a length of the outer shaft  2104 . Although in  FIGS. 21A-21B  the dissection device  2100  includes two dissection arms  2102 , in other embodiments the dissection device  2100  can have more or fewer than two dissection arms  2102  (e.g., one dissection arm, three dissection arms, four dissection arms, etc.). 
     As best shown in  FIG. 21B , the dissection arms  2102  can be positioned at circumferentially opposite portions of the outer shaft  2104  such that an angle θ d  between the dissection arms  2102  is about 180 degrees. In other embodiments, the dissection arms  2102  can be positioned at an angle θ d  that is between about 10 degrees and about 180 degrees, or between about 50 degrees and about 130 degrees (e.g., 60 degrees, 120 degrees, etc.). In some embodiments, it can be advantageous to increase the angle θ d  between the dissection arms  2102  to more closely mirror the curvature of the vessel wall (and thus reduce stress on the vessel wall), as discussed in greater detail below with reference to  FIGS. 22A-22B . 
     Referring still to  FIGS. 21A-21B , each of the dissection arms  2102  can include one or more segments  2101  and one or more joints  2130  between successive segments  2101 . The joints  2130  can be portions of the dissection arms  2102  configured to preferentially flex compared to the segments  2101 , such as by forming small opposing recesses at locations along the dissection arms  2102  shown in  FIG. 21A  (e.g., a living hinge), or the flexible joints  2130  can be small pins, elastic polymeric elements, or other devices that enable one segment  2101  to pivot or bend relative to another. In  FIGS. 21A-21B , the first and second dissection arms  2102  include three generally linear segments  2101  of substantially equal lengths. In other embodiments, the number of segments  2101 , the length of each segment  2101 , the angle between segments  2101 , and/or the shape of each segment  2101  (e.g., linear, curved, etc.) can be varied amongst a single dissection arm  2102  and/or a plurality of dissection arms  2102  to achieve a desired shape or geometry of the dissection pocket. 
     The dissection arms  2102  can be configured for blunt and/or sharp dissection of the vessel wall. For example, in the illustrated embodiment, the dissection arms  2102  individually include a blunt or atraumatic dissection surface along their lengths and a cutting element  2121  projecting from the blunt dissection surface of the proximal-most segment  2101 . In some embodiments, the cutting elements  2121  can project from the respective dissection arm  2102  perpendicular to the blunt dissection surface on which they are affixed. In some embodiments, one or more of the cutting elements  2121  can project from the surface of the respective dissection arm  2102  a distance of between about 0.2 mm and 2.0 mm. Additionally, the cutting elements  2121  can project a distance of between about 0.5 mm and about 1.5 mm. In a particular embodiment, one or more of the cutting elements  2121  can project a distance of about 1 mm, or 1 mm. Selection of an appropriate cutting element projection distance can be advantageous, as the projection distance can affect the amount of cutting force that the cutting element can apply to the wall tissue before “bottoming out” (e.g., when the wall tissue contacts the surface of the respective dissection arm surrounding the cutting element). For example, the greater the projection distance, the greater the cutting force that can be applied. The cutting elements  2121  can be soldered, welded, glued, or otherwise mechanically fixed to the dissection arms  2102 . In some embodiments (not shown), the proximal-most section of the dissection arms  2102  can be exclusively comprised of a cutting element. In other embodiments, the first and/or second dissection arms  2102  can be configured for sharp dissection along their entire lengths and/or configured for blunt dissection along their entire lengths. 
     Referring still to  FIG. 21A , the inner shaft  2184  and the tensioning arms  2182  can define a tensioning unit, and they can be made from stainless steel, Nitinol, PEEK and other generally suitable materials with sufficient stiffness and bending characteristics (e.g., elastic or super elastic) that can impart the desired forces). The tensioning arms  2182  can be spaced apart about the circumference of the inner shaft  2184  such that, in a low-profile state ( FIG. 22A ), the distal portion  2125  of the inner shaft  2184  includes openings between the tensioning arms  2182  that extend along a length of the inner shaft  2184 . Although in  FIGS. 21A-21B  the dissection device  2100  includes two tensioning arms  2182 , in other embodiments, the dissection device  2100  can have more or fewer tensioning arms  2182  (e.g., one tensioning arm, three tensioning arms, four tensioning arms, etc.). 
     As best shown in  FIG. 21B , the tensioning arms  2182  can be positioned at circumferentially opposite portions of the inner shaft  2184  such that an angle θ t  between the tensioning arms  2182  is about 180 degrees. In other embodiments, the tensioning arms  2182  can be positioned at an angle θ t  that is between about 10 degrees and about 180 degrees, or between about 50 degrees and about 130 degrees (e.g., 60 degrees, 120 degrees, etc.). Additionally, the inner shaft  2184  and the outer shaft  2104  can be positioned relative to one another such that the tensioning arms  2182  and the dissection arms  2102  are positioned at an angle θ a  that is generally uniform about the circumference of the dissection device  2100 . For example, as shown in  FIG. 21B , when the dissection device  2100  includes two dissection arms  2102  and two tensioning arms  2182 , the arms  2102 ,  2182  can deploy at an angle θ a  of about 90 degrees. In other embodiments, the dissection device  2100  can have other configurations. 
       FIG. 22A  shows the dissection device  2100  in a collapsed or low-profile state, a  FIG. 22B  shows the dissection device  2100  in a deployed state with only the tensioning arms  2182  deployed, and  FIG. 22B  shows the dissection device  2100  in a deployed state with only the dissection arms  2102  deployed. To deploy the tensioning arms  2182 , the inner shaft  2184  can be pushed distally relative to the pull member  2106  (or the pull member  2106  can be pulled proximally relative to the inner shaft  2184 ). To deploy the dissection arms  2102 , the outer shaft  2104  can be pushed distally relative to the pull member  2106 , or the pull member  2106  can be pulled proximally relative to the outer shaft  2104 . The tensioning arms  2182  can be deployed independently of the dissection arms  2102  (and vice versa) such that the tensioning arms  2182  can be deployed to a desired extent irrespective of the state of the dissection arms  2102 . 
     A method of using the dissection device  2100  will now be described with reference to  FIGS. 2A-2F  and  FIG. 23 . To begin, the dissection device  2100  can be intravascularly positioned in the low-profile state at a treatment site within the lumen of a blood vessel V. Although in some embodiments the dissection device  2100  is intravascularly delivered within a delivery device (e.g., a delivery sheath), such a delivery device is not shown in  FIGS. 22A-22C  to provide a better view of the dissection and tensioning arms  2102 ,  2182  in the low-profile state. Once positioned at the treatment site, the dissection device  2100  can then be advanced through an opening O ( FIG. 2A ) at an interior surface of the vessel wall W at the treatment site and positioned in a space S within the vessel wall W ( FIG. 2A ). Before and/or during deployment of the dissection arms  2102 , the tensioning arms  2182  can be deployed ( FIG. 22B ) to create a tension T ( FIG. 23 ) in the dissection pocket DP that is generally transverse to the plane of dissection (e.g., aligned with dissection force D in  FIG. 23 ). 
     Before, during, and/or after deployment of the tensioning arms  2182 , the outer shaft  2104  can be pushed distally relative to the pull member  2106  to deploy the dissection arms  2102 . As the dissection arms  2102  flex outwardly away from a longitudinal axis of the outer shaft  2104 , a surface of the leading segment (e.g., radially furthest from the longitudinal axis of the device  2100 ) of the respective dissection arm  2102  pushes outwardly against the vessel wall at the periphery of the space in which the dissection device  2100  is positioned, thereby forcing the tissue to separate (e.g., via blunt or sharp dissection). For example, the dissection arms  2102  can apply a dissection force D ( FIG. 23 ) that separates the vessel wall W into an outer layer OL and an inner layer IL (depicted schematically in  FIG. 23 ). The outer layer OL can include intimal, medial, and/or adventitial tissue, and the inner layer IL can include intimal, medial, and/or adventitial tissue. For example, expansion of the dissection arms  2102  can separate an intimal layer from a medial layer, a medial layer from an adventitial layer, a sub-medial layer from a sub-medial layer, an intimal and sub-medial layer from a sub-medial layer, etc. 
     In some procedures, it may be beneficial to deploy the dissection arms  2102  and the tensioning arms  2182  simultaneously. In such a scenario, the dissection arms  2102  can widen the dissection pocket DP in a direction D ( FIG. 23 ) while the tensioning arms  2182  can widen the dissection pocket DP in a direction T ( FIG. 23 ). This widening in a secondary direction can provide additional dissection force and further enlarge the space S and/or dissection pocket DP. 
     To widen the opening O to form a mouth M ( FIG. 2C ) (and thus a leaflet L), the dissection device  2100  can be pulled proximally, thereby forcing the cutting elements  2121  into contact with the vessel wall tissue adjacent the opening (e.g., extending laterally away from the opening O). Depending on the size of the mouth M desired, before retraction of the device  2100 , the pull member  2106  can be pulled proximally to move the dissection arms  2102  inwardly towards the longitudinal axis L of the device  2100 , thereby decreasing the reach of the cutting elements  2121  (and thus the size of the mouth M). In some embodiments, the device  2100  can widen the opening O while being retracted in the low-profile state, as the proximal portion of the cutting elements  2121  create the mouth M. This widening may also facilitate the ability of the cutting elements  2121  to create mouth M by putting the opening in tension as the cutting elements  2121  engage the tissue. 
     Because the inner shaft  2184  and the outer shaft  2104  can move axially independently of one another, the dissection arms  2102  and the tensioning arms  2182  can be controlled independently of one another such that they can be deployed or expanded at different times and at different rates. Such independent control of the dissection and tensioning arms  2102 ,  2182  ensures that a desired tensioning force (e.g., a constant force) is applied as the dissection propagates laterally within the vessel wall W and frees up additional slack tissue that requires additional tensioning. For this reason, fine control of the expansion rate of the tensioning arms  2182  can be advantageous for creation of a dissection pocket DP within a vessel wall W. It is believed that because the vessel wall is generally circular, tension does not increase linearly as the width of the dissection pocket and/or space within the vessel wall increases. For example, as the dissection arms  2102  begin to expand, it may be advantageous to increase the amount of perpendicular tension applied to the vessel wall (from within the dissection pocket DP and/or space S) at a relatively high rate, as even small increases in the width of the dissection pocket DP and/or space S can create relatively large lengths of slack tissue between the tensioning arm  2182  and the nearest edge of the growing dissection pocket DP and/or space S. As the dissection makes its way around the curvature of the dissection pocket DP and/or space S, small increases in the width of the dissection pocket DP and/or space S may require less tension than would the same increase in width earlier in the dissection process. For this reason, it may be advantageous for the tensioning arms  2182  to expand to a greater extent and/or rate in the early stages of expansion of the dissection arms  2102 , and then to a relatively lesser extent and/or rate near the end of the dissection arm expansion. 
       FIG. 24A  is an axial perspective view of another dissection device  2400  shown in a deployed state in accordance with the present technology, and  FIG. 24B  is an end view of the dissection device  2400  shown in  FIG. 24A . The dissection device  2400  can be generally similar to the dissection device  2100  shown in  FIGS. 21A-22C , except the dissection device  2400  includes four tensioning arms  2482  and two angled dissection arms  2402 . Referring to  FIGS. 24A and 24B  together, the centerline of the dissection arms  2402  are less than 180 degrees from each other (see, θ d  in  FIG. 24B ), such that the dissection arms  2402  do not expand outward along the same plane. In one such embodiment, the angle θ d  between the dissection arms  2402  is about 140 degrees. In other embodiments, the angle θ d  between the dissection arms  2402  is between about 100 and about 180 degrees. This angled dissection may be advantageous to accommodate the curvature of the vessel wall. 
     Additionally, in the embodiment shown in  FIGS. 24A and 24B , the dissection device  2400  does not include any tensioning arms at 0 and 180 degrees. In the illustrated embodiment, each tensioning arm  2482  expands outward at an angle of approximately 25 degrees from the central vertical axis (or between 0 and 50 degrees). This configuration may enhance the stability of the device relative to the vessel wall to inhibit or prevent unintended rotation of the entire device upon deployment of the tensioning arms  2482 . Furthermore, this configuration provides tension to the tissue in close proximity to the plane of dissection. 
       FIG. 25  is an axial perspective view of another dissection device  2500  shown in a deployed state in accordance with the present technology. The dissection device  2500  can be generally similar to the dissection device  2100  shown in  FIGS. 21A-21C , except the dissection device  2500  does not include an inner shaft, and the dissection arms  2502  and the tensioning arms  2582  are both coupled to the outer shaft  2504 . As such, the dissection arms  2502  and the tensioning arms  2582  are not controlled independently. Actuation can be accomplished by retracting the pull member  2506  relative to the outer shaft  2506 , or by advancing the outer shaft  2506  distally relative to the pull member  2506 . 
       FIG. 26  shows another embodiment of a dissection device configured in accordance with the present technology. The dissection device  2600  includes tensioning arms  2682 . Each of the tensioning arms  2682  can include a plurality of openings along its length. Such a configuration can provide improved flexibility to the tensioning arms  2682 . 
     3.0 Additional Embodiments of Dissection Devices 
       FIG. 27A  is a cross-sectional side view of a dissection device  2700  in a low-profile state configured in accordance with another embodiment of the present technology. As shown in  FIG. 27A , the dissection device  2700  can include a retractable sheath  2704  and a dissection device  2701  slidably positioned within the retractable sheath  2704 . The dissection device  2701  can include an outer member  2705  and an inner member  2709 . The inner member  2709  can include a proximal portion  2710  positioned within the outer member  2705  and an arm  2709  that extends distally from a distal portion of the proximal portion  2710 . The outer member  2705  can include a proximal portion  2707  which surrounds at least a portion of the proximal inner member  2710 . The outer member  2705  can also include a distal portion  2706  that extends distally from a distal portion of the proximal outer member  2707 . A distal region of the distal outer member  2706  can be coupled to a distal region of the distal inner member  2709 . As shown in  FIG. 27A , in the low-profile state, the dissection device  2701  can have a generally linear shape with a slight bend. For example, the distal inner member  2709  can have a radius of curvature that is slightly less than that of the distal outer member  2706 , such that the distal inner member  2709  sits within or “spoons” with the distal outer member  2706 . At least the distal inner member  2709  and the distal outer member  2706  can be made of a shape memory material such that, once the sheath  2704  is withdrawn, the distal inner and outer members  2709 ,  2706  can assume their natural, curved shapes, as shown in  FIG. 27B . 
       FIG. 27C  is a top view of the dissection device  2700  shown in  FIGS. 27A and 27B  in a second deployed state configured in accordance with an embodiment of the present technology. As shown in  FIG. 27C , the proximal portions (not shown) of the outer and inner members  2705 ,  2709  can be rotated in opposite directions to force the distal members  2706 ,  2709  to flex and fan out, together sweeping out at least a portion of the dissection pocket. 
       FIGS. 28A-28D  are top views of a dissection device  2800  showing various states configured in accordance with an embodiment of the present technology. As shown in  FIG. 28A , the dissection device  2800  can include a first elongated member  2802 , a second elongated member  2806  positioned generally parallel to the first elongated member  2802 , and a connecting member  2804  coupled to the distal regions of the first and second members  2802 ,  2806 . The first member  2802  can be coupled to a first side of the connecting member  2804 , and the second member  2806  can be coupled to a second side of the connecting member  2804  that is opposite the first side. As such, proximal and distal movement of the first and second members  2802 ,  2804  (similar to a train drive) can cause the connecting member  2804  to rotate about the distal regions, thereby sweeping out at least a portion of the periphery of a dissection pocket along its outermost edge. 
       FIG. 29A  is a top view of a dissection device  2900  in a deployed state configured in accordance with an embodiment of the present technology, and  FIG. 29B  is an end view of the dissection device  2900  shown in  FIG. 29A . As shown in  FIGS. 29A and 29B , the dissection device  2900  can include a dissection device  2901  and a retractable sheath  2906 . The dissection device  2901  can include a braided wire cage  2904  made of a spring material or shape memory material coupled to a support member  2902 . The cage  2904  can be configured to collapse into a low-profile state during delivery (within the sheath  2906 ). During deployment, the dissection device  2901  can be advanced distally from the sheath  2906  (or the sheath  2906  can be withdrawn), thereby allowing the cage  2904  to assume an expanded, deployed configuration. For example, the cage  2901  can have a rounded shape, or any shape desired for the dissection pocket. As best shown in  FIG. 29B , in one embodiment the cage  2901  can curve inwardly such that the lateral portions  2909  of the cage bend back towards the longitudinal axis of the support member  2902 . As such, the curved cage  2904  can better align the with curvature of the lumen at the treatment site. 
       FIGS. 30A-30C  are top views of a dissection device  3000  during various stages of deployment configured in accordance with an embodiment of the present technology. As shown in  FIGS. 30A-30C , the dissection device  3000  can include a shaft  3004  having an opening  3006  at a distal region and an expandable member  3002  positioned at least partially within a lumen of the shaft  3004 . The expandable member  3002  can have a proximal portion (not shown) and a distal portion configured to be advanced through the opening  3006  in the shaft  3004  during deployment. As the expandable member  3002  is advanced through the opening  3006 , the expandable member  3002  coils about itself, thereby amassing a larger surface area as more of the expandable member  3002  is fed through the opening  3006 . As such, the periphery of the expandable member  3002  can form at least a portion of the periphery of the dissection pocket. 
       FIG. 31  is a top perspective view of a dissection device  3100  shown within a blood vessel V and configured in accordance with an embodiment of the present technology. The blood vessel V is shown in partial cross-section for ease of illustration. As shown in  FIG. 31 , the dissection device  3100  can include an elongated tubular shaft  3104  and a coiled wire  3102  configured to be advanced through the shaft  3104  and deployed within the vessel wall to form or enlarge a dissection pocket DP. The wire  3102  can be made of a shape memory material. As such, when the wire  3102  is advanced past the shaft  3104 , it assumes a densely packed, coiled shape. 
       FIG. 32A  is a top perspective view of a dissection device  3200  shown within a blood vessel V and configured in accordance with an embodiment of the present technology. The blood vessel is shown in partial cross-section for ease of illustration.  FIG. 32B  is an isolated top view of the dissection component  3201  shown in  FIG. 32A , and  FIG. 32C  is an end view of  FIG. 32B . Referring to  FIGS. 32A-32C  together, the dissection device  3200  can include a delivery shaft  3212  and a dissection component  3210  which is curved for example in a bayonet shape and slidably positioned within the shaft  3212 . As shown in  FIGS. 32B and 32C , the dissection device  3201  can include a proximal portion  3209  (only a portion of which is shown in  FIG. 32B ), a cutting portion  3204  having a cutting edge  3206 , and a distal portion  3202 . The cutting portion  3204  can be positioned distal to a bend in the device  3201 , and proximal of the distal portion  3202 . The distal portion  3202  can be generally atraumatic. As shown in  FIG. 32A , the dissection device  3201  can be advanced distally from the delivery device shaft  3212  (positioned with the lumen of the vessel V), inserted into the vessel wall, and rotated to sweep out a dissection pocket DP in the vessel wall. 
       FIG. 33A  is a top perspective view of a dissection device  3300  shown within a blood vessel V and configured in accordance with an embodiment of the present technology. The blood vessel is shown in partial cross-section for ease of illustration.  FIG. 33B  is an isolated top view of the dissection device  3301  shown in  FIG. 33A , and  FIG. 33C  is an end view of  FIG. 33B . Referring to  FIGS. 33A-33C  together, the dissection device  3300  of  FIGS. 33A-33C  can be generally similar to the dissection device  3200  of  FIGS. 32A-32C , except the dissection device  3300  of  FIGS. 33A-33C  is generally linear and the delivery shaft  3312  is curved in a bayonet shape. 
       FIG. 34A  is a top perspective view of another embodiment of a dissection device  3400  shown within a blood vessel V and configured in accordance with an embodiment of the present technology. The blood vessel V is shown in partial cross-section for ease of illustration. As shown in  FIG. 34A , the dissection device  3400  can include an elongated hollow shaft  3402  and a gel  3404  configured to be delivered through the shaft  3402  and into the vessel wall at a specific pressure and flow rate configured to form or enlarge a dissection pocket DP.  FIG. 34B  is a cross-sectional end view of the gel  3404  shown positioned within the vessel wall. The gel  3404  may optionally be removed via aspiration via hollow shaft  3402  after the pocket is created. Alternately, the gel may be disbursed or reabsorbed. 
     4.0 Examples 
     The following examples are illustrative of several embodiments of the present technology: 
     1. A device for separating tissue within a wall of a blood vessel, the device comprising:
         an elongated shaft having a longitudinal axis, a proximal portion, and a distal portion configured to be (1) intravascularly delivered to a treatment site within the blood vessel, (2) advanced through an opening at an interior surface of the blood vessel wall to a space within the wall, and (3) positioned within the space within the wall of the blood vessel at the treatment site;   an elongated member slidably positioned within the elongated shaft;   a dissection arm at the distal portion of the shaft, the arm having a longitudinal axis and moveable between a low-profile state and a deployed state via axial movement of the elongated member relative to the shaft, and wherein—
           in the low-profile state, the longitudinal axis of the arm is parallel to the longitudinal axis of the elongated shaft,   in the deployed state, a portion of the arm flexes outwardly away from the longitudinal axis of the shaft, and   the arm is configured to be deployed within the space such that, as the arm moves from the low-profile state to the deployed state, the arm pushes against vessel wall tissue at a periphery of the space, thereby separating tissue at the periphery to form a dissection pocket having a predetermined shape.   
               

     2. The device of example 1 wherein the device further comprises a tensioning arm at the distal portion, the tensioning arm having a low-profile state and a deployed state, and wherein, in the deployed state, the tensioning arm flexes outwardly away from the longitudinal axis of the shaft. 
     3. The device of example 1 or example 2 wherein the dissection arm is configured to flex outwardly within a first plane, and wherein the device further comprises one or more tensioning arms at the distal portion, the tensioning arm having a low-profile state and a deployed state, and further wherein, in the deployed state, the tensioning arm flexes outwardly away from the longitudinal axis of the shaft within a second plane that is angled relative to the first plane. 
     4. The device of any of examples 1-3 wherein the arm is a first arm and wherein the device further includes a second arm at the distal portion, wherein an outline of the first and second arms in the deployed state defines the predetermined shape of the dissection pocket. 
     5. The device of any of examples 1-4 wherein the arm is integral with the shaft. 
     6. The device of any of examples 1-5 wherein a distal end portion of the elongated member is coupled to a distal end portion of the elongated shaft. 
     7. The device of any of examples 1-6, further comprising a cutting element positioned along at least a portion of the arm and configured to cut vessel wall tissue adjacent the opening to widen the opening. 
     8. The device of any of examples 1-7, further comprising:
         a tensioning arm at the distal portion, the tensioning arm having a low-profile state and a deployed state, and wherein, in the deployed state, the tensioning arm flexes outwardly away from the longitudinal axis of the shaft.   a cutting element positioned along at least a portion of the arm and configured to cut vessel wall tissue adjacent the opening to widen the opening.       

     9. A dissection device, comprising:
         an elongated shaft having a proximal region and a distal region, wherein the distal region is configured to be positioned within a space within a blood vessel at a treatment site;   a tensioning unit at the distal region of the shaft including a tensioning arm configured to flex outwardly away from the longitudinal axis of the shaft to create tension in the tissue surrounding the space; and   a dissection unit at the distal region of the shaft including a dissection arm configured to flex outwardly away from the longitudinal axis of the shaft to push against vessel wall tissue surrounding the space to separate the vessel wall tissue and enlarge the space.       

     10. The device of any of examples 1-9 wherein the dissection device does not include a balloon. 
     11. The device of any of examples 1-10 wherein the tensioning arm is a first tensioning arm, and wherein the tensioning unit includes a seconding tensioning arm positioned opposite the first tensioning arm about the circumference of the shaft. 
     12. The device of any of examples 1-10 wherein the dissection arm is a first dissection arm, and wherein the dissection unit includes a second dissection arm positioned opposite the first dissection arm about the circumference of the shaft. 
     13. The device of any of examples 1-12 wherein:
         the tensioning arm is a first tensioning arm, and wherein the tensioning unit includes a seconding tensioning arm positioned opposite the first tensioning arm about the circumference of the shaft; and   the dissection arm is a first dissection arm, and wherein the dissection unit includes a second dissection arm positioned opposite the first dissection arm about the circumference of the shaft.       

     14. The device of any of examples 1-3 wherein the dissection arm includes a cutting element having a sharp edge configured to cut vessel wall tissue. 
     15. The device of any of examples 1-14, further including an elongated member positioned within the shaft and configured to move axially relative to the shaft. 
     16. The device of any of examples 1-15 wherein the dissection unit is configured to be deployed independently of the tensioning unit. 
     17. A method, comprising:
         intravascularly positioning a dissection device within a blood vessel, wherein the dissection device includes an elongated shaft having a distal portion and a dissection arm at the distal portion;   advancing the distal portion through an opening in an interior surface of the blood vessel wall, thereby positioning the distal portion in a space within the wall; and   while the distal portion is positioned within the space, separating tissue at a periphery of the space with the dissection arm by flexing a portion of the arm outwardly away from a longitudinal axis of the shaft, thereby creating a dissection pocket within the vessel wall.       

     18. The method of example 17 wherein the dissection device further comprises an elongated member slidably disposed within the elongated shaft, and wherein the method includes axially moving the elongated member relative to the elongated shaft to flex the arm outwardly away from the longitudinal axis of the shaft. 
     19. The method of example 17 wherein the dissection device further comprises a tensioning arm at the distal portion, and wherein the method includes creating tension within the tissue surrounding the space with the tensioning arm by flexing the tensioning arm away from the longitudinal axis of the shaft into contact with the tissue. 
     20. The method of example 17 wherein creating tension within the tissue occurs before, during, and/or after separating vessel wall tissue with the dissection arm. 
     21. The method of example 17 wherein the dissection device further comprises a cutting element, and wherein the method further includes cutting vessel wall tissue adjacent the opening with the cutting element. 
     22. The method of example 21 wherein cutting vessel wall tissue occurs before, during, and/or after separating tissue at the periphery of the space. 
     23. The method of example 21, further including pushing the cutting element distally relative to the arm to cut the vessel wall tissue. 
     24. The method of example 21, further including pulling the cutting element proximally to cut the vessel wall tissue. 
     25. The method of example 21, further including pulling the cutting element proximally relative to the arm to cut the vessel wall tissue. 
     26. The method of example 21, further including advancing the cutting element along an outer surface of the arm to cut the vessel wall tissue. 
     27. The method of example 21, further including advancing the cutting element along a slot within the arm to cut the vessel wall tissue. 
     28. The method of example 21 wherein the cutting element is integral with the arm. 
     29. The method of example 21 wherein the cutting element is a separate component from the shaft, and wherein the method further includes positioning the cutting element at or near the opening by advancing the cutting element through or over the shaft. 
     30. The method of example 21 wherein the cutting element is a separate component from the shaft, and wherein the method further includes:
         removing the distal portion from the dissection pocket; and   positioning the cutting element at or near the opening.       

     31. The method of example 21 wherein cutting vessel wall tissue occurs at a first time, and wherein the method further includes cutting vessel wall tissue at a second time. 
     32. The method of example 31, further including repositioning the cutting element between cutting vessel wall tissue the first time and cutting vessel wall tissue the second time. 
     33. The method of example 32 wherein repositioning the cutting element occurs while a portion of the dissection device remains positioned within the dissection pocket. 
     34. The method of example 17 wherein the space within the vessel wall is a first space, and wherein the method further includes:
         flexing the arm outwardly away from a longitudinal axis of the shaft at a first time to separate tissue at the periphery of the space;   collapsing the arm towards the longitudinal axis of the shaft after flexing the arm the first time; and   after collapsing the arm, flexing the arm outwardly away from a longitudinal axis of the shaft at a second time to separate tissue.       

     35. The method of example 34, further including repositioning the distal portion before flexing the arm outwardly the second time. 
     36. The method of example 35 wherein repositioning the distal portion includes at least one of: moving the distal portion axially within the dissection pocket, moving the distal portion laterally within the dissection pocket, and rotating the distal portion about its longitudinal axis within the dissection pocket. 
     37. The method of example 17, further including separating tissue at the periphery of the space by ejecting a fluid from the distal portion while separating tissue at the periphery of the space with the arm. 
     38. The method of example 21 wherein cutting vessel wall tissue adjacent the opening with the cutting element and flexing the portion of the arm outwardly away from the longitudinal axis of the shaft to create the dissection pocket within the vessel wall occurs at the same time. 
     39. The method of example 21 wherein cutting vessel wall tissue adjacent the opening with the cutting element transforms the dissection pocket into a valve leaflet. 
     40. A device for separating tissue within a wall of a blood vessel, the device comprising:
         an first elongated shaft having a longitudinal axis, a proximal portion, and a distal portion configured to be (1) intravascularly delivered to a treatment site within the blood vessel, (2) advanced through an opening at an interior surface of the blood vessel wall to a space within the wall, and (3) positioned within the space within the wall of the blood vessel at the treatment site;   a second elongated shaft positioned within the first elongated shaft;   a dissection arm at the distal portion of the first elongated shaft, the arm having a longitudinal axis and moveable between a low-profile state and a deployed state via axial movement of the second elongated shaft relative to the first elongated shaft, and wherein—
           in the deployed state, a portion of the arm flexes outwardly away from the longitudinal axis of the shaft, and   the arm is configured to be deployed within the space such that, as the arm moves from the low-profile state to the deployed state, the arm pushes against vessel wall tissue at a periphery of the space, thereby separating tissue at the periphery to form a dissection pocket having a predetermined shape; and   
           a cutting device configured to be slidably received within a lumen of the second elongated shaft, the cutting device including a shaft and a cutting element rotatably coupled to the shaft, and wherein, in a deployed state, the cutting element is configured to extend outwardly away from the longitudinal axis of the shaft.       

     41. The device of any of examples 1-16 and 40 wherein the cutting element has a sharp edge, and wherein, in the deployed state, the sharp edge faces proximally. 
     42. The device of any of examples 1-16, 40 and 41 wherein the cutting element has a sharp edge, and wherein, in the deployed state, the sharp edge faces distally. 
     43. The device of any of examples 1-16 and 40-42 wherein the first elongated shaft includes a slot extending along at least a portion of its length, and wherein, when the cutting element is in a deployed state, the cutting element extends through the slot. 
     44. The device of any of examples 1-16 and 40-43 wherein the slot is a first slot and the second elongated shaft includes a second slot extending along at least a portion of its length, wherein the second elongated shaft is positioned within the first elongated shaft such that the first and second slots are circumferentially aligned, and wherein the cutting element is configured to extend through the first and second in a deployed state. 
     45. The device of any of examples 1-16 and 40-44 wherein the second elongated shaft includes a slot extending along at least a portion of its length, and wherein the cutting element is configured to extend through the slot in a deployed state. 
     46. The device of any of examples 1-16 and 40-45 wherein the dissection arm includes a slot extending along at least a portion of its length, and wherein the cutting element is configured to move in a longitudinal direction through the slot in a deployed state. 
     47. The device of any of examples 1-16 and 40-46 wherein the dissection arm includes a slot extending along at least a portion of its length, and wherein the cutting element is configured to move in a longitudinal direction through the slot when the cutting arm is in a deployed state and when the dissection arm is in a deployed state. 
     48. The device of any of examples 1-16 and 40-47 wherein the dissection arm includes a slot extending along at least a portion of its length, and wherein the cutting element is configured to move in a longitudinal direction through the slot when the cutting arm is in a deployed state and when the dissection arm is in a deployed state. 
     49. The device of any of examples 1-16 and 40-48 wherein the dissection arm includes a first segment and a second segment separated by a flexible joint. 
     50. The device of any of examples 1-16 and 40-49 wherein the dissection arm includes first, second, and third segments, and wherein the first and second segments are separated by a first flexible joint and the second and third segments are separated by a second flexible joint, and wherein the second segment includes a cutting element extending along at least a portion of its length. 
     51. The device of any of examples 1-16 and 40-50 wherein the dissection arm is a first dissection arm and the device includes a second dissection arm, and wherein the cutting element is configured to extend outwardly away from the shaft within an interior region defined by an outline of the first and second dissection arms in a deployed state. 
     5.0 CONCLUSION 
     The dissection devices of the present technology may have multiple advantages over conventional dissection devices, such as balloon-based systems. For example, cutting elements may be more easily integrated with the controlled dissection device because the general strength and rigidity of the dissection arms enable the cutting elements to be fixed to the arms via a variety of robust fixation methods (e.g., via welding, soldering, adhesive, mechanical fixation, etc.) and/or guided by the arms, for example, with slots or other coupling features. Conversely, cutting elements are generally limited to being affixed to the surface of conventional balloons using an adhesive because of the elasticity of balloons. Moreover, because the dissection arms are more rigid than balloons, the arms maintain their shape during deployment such that the surface along which the cutting elements are affixed does not bend or stretch during deployment. In contrast, the surface of a balloon stretches and changes shape during inflation, which can affect the shape of the cutting elements. 
     Another advantage of the controlled dissection devices of the present technology is that they provide precise control over the shape of the dissection pocket during dissection, as well as greater predictability of the resulting shape of the dissection pocket. Balloon-based dissection devices expand in the direction of least resistance; thus, there is very little control over the amount of tension applied at each point during the dissection. As a result, a balloon may over-stretch a thin flap (in the direction of the vessel lumen) prior to or instead of performing any lateral dissection. Such stretching can result in an unpredictable dissection pocket shape, leaflet tearing, and/or insufficient dissection. Conversely, the controlled dissection devices described with above reference to  FIGS. 2A-34B  are generally more rigid (e.g., non-elastic under operating forces) than balloons and expand to a substantially pre-defined shape or otherwise controlled configuration even in the presence of large and/or unpredictable tissue forces. 
     Yet another advantage of the controlled dissection devices of the present technology is that they enable complex dissection techniques. For example, the controlled dissection devices of the present technology can generate non-symmetric dissection pockets (i.e., non-symmetric if viewing the device end-on, about a latitudinal midline of the device). The lengths, angles, shapes, etc. of the dissection arms of the present technology can be configured to achieve a desired shape regardless of tissue forces present at the treatment site. Another complex dissection technique of the present technology is the independent control of the tensioning and dissection arms. The tensioning arms can expand along one or more particular planes, and the dissection arms can expand along one or more distinct planes as detailed above. 
     The controlled dissection devices configured in accordance with the present technology also provide high resolution and clarity of visualization during expansion under ultrasound as compared to an expandable balloon-based system. For example, the metallic surfaces of the dissection arms can include strands of polyvinyl alcohol (“PVA”) or other material viewable under ultrasound, and therefore the expansion can be monitored clearly. Various locations on and/or components of the controlled dissection devices (e.g., the dissection elements, the tensioning elements, the blades, etc.) can include such a viewable material that provides real-time monitoring of the shape of the dissection pocket during the procedure. In contrast, the surface of a urethane balloon, PET balloon, and/or latex balloon can be difficult to perceive under ultrasound, and thus it can be difficult to differentiate the balloon from thin layers of tissue surrounding the balloon. 
     Any of the dissection devices and/or components thereof (e.g., shaft, cutting elements, dissection arms, tensioning arms, pull rod, etc.) described herein, can be made from stainless steel, Nitinol, PEEK and other generally suitable materials with sufficient stiffness and bending characteristics (e.g., elastic or super elastic) that can impart the desired forces. For example, any of the dissection arms and/or tensioning arms described herein can be made of a superelastic and/or shape memory material and can be heat-set during manufacturing to be biased in a particular shape and/or bend direction that corresponds to a desired dissection pocket DP and/or leaflet L shape. Alternately, the bias may be created by pre-bending the components to the desired bend direction to impart some memory to the components. 
     In all of the above embodiments involving dissection and/or tension arms, the flexibility of the arms may be tailored to achieve a desired geometry and force on the tissue. For example the dissection or tensioning arms may vary in width. Alternately, the dissection or tensioning arms may have a cut out pattern that increases the flexibility of the arms in a bend direction while maintaining rigidity in a non-bend direction. For example the dissection arms may be wide but have a series of square holes to create a ladder pattern. This pattern allows the arms to bend more easily while resisting twisting and thus able to deliver more force in the plane of dissection. 
     In all of the above embodiments, the dissection device may also be configured to hydrodissect vessel wall tissue simultaneously with mechanical dissection. In a particular embodiment, the dissection device can include a hydrodissection device, such as a needle or tube fluidly coupled to a pressurized fluid source, such as a syringe, pressurized fluid bag, or pump. The tip of the needle can be configured to deliver a focused fluid flow through a nozzle, to create a hydrodissection force. In another embodiment, one or more shafts of the dissection device can be fluidly coupled to a pressurized fluid source and may include one or more fluid delivery ports at its distal portion. 
     In all embodiments, the dissection device is configured to fit through an opening in a vessel wall access, as well as a delivery device and/or system (for delivery through the vasculature and/or to gain access to an interior portion of the vessel wall) having an outer diameter which is less than or equal to 20 F, or less than or equal to 19 F, or less than or equal to 16 F, or less than or equal to 14 F (corresponding to outer diameters of 0.260 inches, 0.234 inches, 0.209 inches or 0.192 inches, respectively). This size range is appropriate for treatment of veins through a femoral venous or internal jugular access site, or for treatment of arteries through a femoral arterial or carotid artery access site, with the smaller sizes providing more options for access vessel size and access/closure methods. In some embodiments, the dissection device may have an outer diameter that is less than or equal to 0.150 inches, or less than or equal to 0.124 inches, or less than or equal to 0.099 inches, or less than or equal to 0.072 inches (for use with, for example, a delivery device and/or system having an outer diameter of 20 F, 19 F, 16 F, or 14 F, respectively). In these and other embodiments, the delivery device and/or system also includes a lumen for an intravascular imaging device, such as a 3.2 F intravascular ultrasound catheter with an imaging lumen of 0.060 inches inner diameter. In this embodiment, the lumen of the delivery device and/or system may be reduced to accommodate the imaging device lumen and associated wall dimensions. In such embodiments, for example, the dissection device may have an outer diameter that is less than or equal to 0.096 inches, or less than or equal to 0.060 inches, or less than or equal to 0.034 inches (for use with, for example, a delivery device and/or system having an outer diameter that is 20 F, 19 F, or 16 F, respectively). 
     Although many of the embodiments are described above with respect to devices, systems, and methods for intravascular creation of autologous venous valves and/or valve leaflets, other applications and other embodiments in addition to those described herein are within the scope of the technology. For example, the devices, systems, and methods of the present technology can be used in any body cavity or lumen or walls thereof (e.g., arterial blood vessels, venous blood vessels, urological lumens, gastrointestinal lumens, etc.) and used for surgical creation of autologous valves as well as repair of autologous and/or synthetic valves. Additionally, several other embodiments of the technology can have different states, components, or procedures than those described herein. For example, although several embodiments of the present technology include two dissection arms, in other embodiments the dissection device can have more or fewer than two dissection arms (e.g., one dissection arm, three dissection arms, four dissection arms, etc.) For example, in some embodiments, the dissection device can include a single dissection member having a first portion configured to extend laterally away from the longitudinal axis of the shaft in a first direction and a second portion configured to extend laterally away from the longitudinal axis of the shaft in a second direction opposite the first direction. Moreover, it will be appreciated that specific elements, substructures, advantages, uses, and/or other features of the embodiments described with reference to  FIGS. 2A-34B  can be suitably interchanged, substituted or otherwise configured with one another in accordance with additional embodiments of the present technology. For example, the tensioning arms described with reference to  FIGS. 21A-26  can be combined with any of the dissection devices shown in  FIGS. 2A-20 and 27A-34B . Likewise, the cutting elements described in  FIGS. 3A-3D, 10-22 and 24A-26  can be combined with any of the dissection arms, tensioning arms, and/or dissection devices described herein. 
     Furthermore, suitable elements of the embodiments described with reference to  FIGS. 2A-34B  can be used as standalone and/or self-contained devices. A person of ordinary skill in the art, therefore, will accordingly understand that the technology can have other embodiments with additional elements, or the technology can have other embodiments without several of the features shown and described below with reference to  FIGS. 2A-34B . For example, the dissection devices, systems, and methods of the present technology can be used with any of the device devices, systems, and methods disclosed in U.S. patent application Ser. No. 13/035,752, filed Feb. 2, 2011, U.S. patent application Ser. No. 13/926,996, filed Jun. 25, 2013, U.S. patent application Ser. No. 13/035,919, filed Feb. 25, 2011, U.S. patent application Ser. No. 13/450,432, filed Apr. 19, 2012, U.S. patent application Ser. No. 14/377,492, filed Aug. 7, 2014, PCT Application No. PCT/US2014/011209, filed Jan. 10, 2014, U.S. patent application Ser. No. 14/499,969, filed Sep. 26, 2014, U.S. Provisional Patent Application No. 61/969,262, filed Mar. 24, 2013, and U.S. Provisional Patent Application No. 61/969,263, filed Mar. 24, 2013, all of which are incorporated by reference herein their entireties.