Patent Publication Number: US-2023134921-A1

Title: Vessel harvesting apparatus and method

Description:
FIELD 
     An embodiments described herein relates to a surgical instrument and its use, and more particularly, to a surgical instrument for use in a vessel harvesting procedure. 
     BACKGROUND 
     Coronary artery bypass grafting (CABG) is a well-established surgical procedure in which arterial blockages of the heart are bypassed using autologous blood vessels (hereafter referred to as bypass conduits). Commonly-used autologous blood vessels for bypass include the internal thoracic artery, the radial artery, and the greater saphenous vein. Patency of the graft is greatly influenced by bypass conduit selection, surgical strategies and anastomotic techniques, patient characteristics such as disease state and comorbidities, in addition to numerous other factors. 
     Efforts to improve the patency of bypass conduits have focused on aspects such as the type of blood vessel used (arterial or venous) and method of harvest (open or endoscopic). Although attached internal thoracic artery grafts remain the gold standard with respect to long-term patency, they are limited in length, and thus in the number of bypasses that can be completed with each internal thoracic artery. For patients undergoing multiple bypasses in one operation, or repeat bypass surgery, radial artery and/or greater saphenous vein free grafts often are needed. These blood vessels are harvested either via open surgical access by making an incision through the skin over the entire length of vessel to be harvested, or less-invasively through the use of endoscopic devices. 
     Endoscopic vessel harvest (EVH) has been adopted as the standard of care in many parts of the world due to a substantial reduction in morbidity at the vessel harvest site and corresponding economic benefit, as well as other advantages such as improved cosmetics. However, concerns remain amongst some clinicians about the impact of EVH on conduit quality and about the use of venous conduits on long-term CABG patency. The quality of endoscopically-harvested bypass conduits may be affected by EVH device selection, endoscopic harvesting techniques, and post-harvest conduit handling. Consequently, advanced devices, refined techniques, and improved user training programs have been developed to address the weaknesses of the early EVH experience. Meanwhile, clinical evidence has also emerged suggesting that venous conduits harvested with their surrounding perivascular tissue (hereafter referred to as the tissue pedicle) rather than as skeletonized vessels per current practices can lead to improved long-term bypass graft patency. These pediculated or “no-touch” harvesting techniques, which are already employed for internal thoracic artery harvests, are believed to improve long-term performance of venous conduits by protecting the vessel from mechanical trauma during harvest, providing structural support to the conduit and allowing perfusion of the conduit wall upon arterialization, and facilitating beneficial biochemical processes such as nitric oxide release. 
     Although pediculated vessel harvest can be performed using commercially-marketed devices for EVH such as VASOVIEW HEMOPRO (Getinge Aft Sweden), existing device designs and published instructions for use have not been specifically optimized to accomplish removal of the tissue pedicle, and published clinical data for pediculated venous bypass conduits have employed conduits harvested via open surgical access. New apparatus and method for vessel harvesting that addresses the weaknesses of early or current EVH techniques are described herein. 
     SUMMARY 
     An apparatus for harvesting a vessel from a body, includes: a cannula having a dissector for advancing along the vessel to create a tunnel, the dissector having a transparent portion; and an energy tool moveably coupled to the cannula, wherein the energy tool is configured to separate a pediculated vessel having at least a segment of the vessel and a pedicle around the segment of the vessel from surrounding tissue, and wherein at least a part of the energy tool is visible through the transparent portion of the dissector during use of the energy tool. 
     Optionally, the energy tool has a retracted position and an extended position. 
     Optionally, the energy tool is configured to deflect towards a longitudinal axis of the apparatus as the energy tool moves from the retracted position to the extended position. 
     Optionally, the energy tool is slidably coupled to the cannula so that the energy tool is slidable along a direction that is parallel to a longitudinal axis of the cannula. 
     Optionally, the energy tool is steerable. 
     Optionally, the energy tool has an arcuate tip, a blunt tip, or a spatulate tip. 
     Optionally, the energy tool has forceps-type jaws. 
     Optionally, the energy tool is moveable along a curvilinear path circumferentially around a longitudinal axis of the cannula. 
     Optionally, the energy tool is rotatable to modify its orientation with respect to a longitudinal axis of the cannula. 
     Optionally, the apparatus further includes an imaging device, wherein the energy tool is moveable to a position distal to a distal end of the imaging device. 
     Optionally, the apparatus further includes a retractor moveably coupled to the cannula, wherein the retractor is configured to engage with the pediculated vessel. 
     Optionally, the apparatus further includes an imaging device, wherein the retractor is moveable to a position distal to a distal end of the imaging device. 
     Optionally, the cannula has a first side and a second side opposite from the first side, and wherein retractor is located closer to the first side of the cannula than to the second side of the cannula, and the energy tool is located closer to the second side of the cannula than to the first side of the cannula. 
     Optionally, the retractor is configured to deflect away from a longitudinal axis of the apparatus as the retractor moves from a retracted position to an extended position. 
     Optionally, the retractor is configured to change from a lower-profile when in a retracted position, to a larger-profile when in an extended position. 
     Optionally, the energy tool comprises an edge configured to cut tissue. 
     Optionally, the energy tool comprises a ring-shape structure. 
     Optionally, the ring-shape structure is mounted to a rod. 
     Optionally, the energy tool comprises a first heating element at a leading end of the ring-shape structure, and a second heating element at a circumferential exterior surface of the ring-shape structure for providing energy to control bleeding. 
     Optionally, the energy tool is configured to provide ultrasonic energy for tissue separation and/or sealing. 
     Optionally, the energy tool is configured to provide heat for tissue separation and/or sealing. 
     Optionally, the energy tool is configured to provide radiofrequency energy for tissue separation and/or sealing. 
     Optionally, the energy tool comprises a commercially available energy instrument that is detachably coupled to the cannula. 
     Optionally, the cannula comprises a lumen configured to house a first imaging device. 
     Optionally, the energy tool is located distal to a distal end of the lumen. 
     Optionally, the apparatus further includes the first imaging device. 
     Optionally, the first imaging device comprises an endoscope. 
     Optionally, the first imaging device comprises an electronic image sensor. 
     Optionally, the first imaging device comprises a distal end, and wherein an axis extending from the distal end of the imaging device to the energy tool traverses the transparent portion of the dissector. 
     Optionally, the apparatus further includes a second imaging device, wherein the first imaging device is configured for visualization of tissue dissection by the dissector, and the second imaging device is configured for visualization of an operation being performed by the energy tool. 
     Optionally, the apparatus has a central axis extending along a longitudinal length of the apparatus, the dissector is located at a first longitudinal axis offset from the central axis, and the energy tool is located at a second longitudinal axis offset from the central axis, the second longitudinal axis being different from the first longitudinal axis. 
     A method for harvesting a vessel from a body, includes: creating, by an apparatus, a tunnel from a skin incision for harvesting a vessel; and separating, by an energy tool, a pediculated vessel having at least a segment of the vessel and a pedicle around the segment of the vessel, wherein at least a part of the energy tool is visible through a transparent portion of the apparatus while the energy tool is being used. 
     Other and further aspects and features will be evident from reading the following detailed description of the embodiments, including the appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings illustrate the design and utility of embodiments, in which similar elements are referred to by common reference numerals. These drawings are not necessarily drawn to scale. In order to better appreciate how the above-recited and other advantages and objects are obtained, a more particular description of the embodiments will be rendered, which are illustrated in the accompanying drawings. These drawings depict exemplary embodiments and are not therefore to be considered limiting in the scope of the claims. 
         FIG.  1    illustrates an apparatus for harvesting a vessel. 
         FIG.  2 A  illustrates another apparatus for harvesting a vessel, particularly showing the apparatus having a retractor and an energy tool in retracted configurations. 
         FIG.  2 B  illustrates the apparatus of  FIG.  2 A , particularly showing the retractor and the energy tool in partially-extended configurations. 
         FIG.  2 C  illustrates the apparatus of  FIG.  2 A  and  FIG.  2 B , particularly showing the retractor and the energy tool in fully-extended configurations. 
         FIG.  2 D  illustrates the retractor having a lower-profile when in a retracted position. 
         FIG.  2 E  illustrates the retractor having a larger-profile when in an extended position. 
         FIG.  3    illustrates an image from an imaging device viewing through a dissector of the apparatus of  FIG.  2 A  when the retractor and the energy tool are in retracted configurations. 
         FIG.  4    illustrates an image from an imaging device viewing through a dissector of the apparatus of  FIG.  2 B  when the retractor and the energy tool are in extended configurations. 
         FIG.  5    illustrates a frontal view of the apparatus of  FIG.  2 A . 
         FIG.  6    illustrates a frontal view of the apparatus of  FIG.  2 B . 
         FIGS.  7 - 9    illustrate images from an imaging device viewing through a dissector of the apparatus of  FIG.  2    during a vessel harvesting procedure. 
         FIGS.  10 A- 10 B  illustrate engagement of the vessel by a retractor during the vessel harvesting procedure. 
         FIGS.  10 C- 12    illustrate additional images from an imaging device viewing through the dissector of the apparatus of  FIG.  2    during the vessel harvesting procedure. 
         FIG.  13    illustrates a method of vessel harvesting. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments are described hereinafter with reference to the figures. It should be noted that the figures are not drawn to scale and that elements of similar structures or functions are represented by like reference numerals throughout the figures. It should also be noted that the figures are only intended to facilitate the description of the embodiments. They are not intended as an exhaustive description of the embodiments of the disclosure or as a limitation on the scope of the inventions disclosed herein. In addition, an illustrated embodiment does not need to have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced in any other embodiments even if not so illustrated or explicitly described. 
       FIG.  1    illustrates an apparatus  10  for harvesting a vessel. The apparatus  10  has a sheath  12 , and a dissector tip  14  at one end of the sheath  12 . The dissector tip  14  is configured to be inserted into a patient through a skin incision, and be advanced along a target vessel  15 . The apparatus  10  also has a cutting element  16  with a ring shape. The ring-shape cutting element  16  is configured for placement circumferentially around the target vessel  15 , and to separate the tissue circumscribed by the cutting element  16  from its surrounding tissue, as the sheath  12  is advanced in a forward (or distal) direction along the target vessel  15 . The apparatus  10  also has an endoscope  18  housed in the sheath  12 . The endoscope  18  has a forward view through a transparent portion of the tip  14 . The apparatus  10  has several drawbacks with respect to its clinical safety and effectiveness. 
     First, in the apparatus  10 , because the distal end of the endoscope  18  is located distal to the cutting element  16 , the cutting element  16  is entirely out of the field of view of the endoscope  18 . Accordingly, while the cutting element  16  is being used to separate tissue, the user of the apparatus  10  cannot see the tissue that is being cut, nor can the user see the cutting element  16 . Thus, the apparatus  10  poses substantial risks in terms of clinical safety and effectiveness. In particular, because the user cannot see the tissue being operated on, there are substantial risks of unintended mechanical or thermal damage to the target vessel and surrounding tissues, including inadvertent severing of the target vessel. 
     In addition, the ring shape cutting element  16  in the apparatus  10  is configured to always hold the target vessel between the field of view of the endoscope  18  and a portion of the cutting element  16 . Accordingly, even if the apparatus  10  is modified to move the endoscope  18  proximally, so that the lens of the endoscope  18  is proximal to the cutting element  16 , the above visualization problem still exists. In particular, due to the geometry of the cutting element  16 , and the way that it is configured to separate tissue, the endoscope  18  cannot see the underside of the target vessel, nor can it see the bottom half of the cutting element  16  (because the target vessel will block the view of the endoscope  18 ). 
     Also, when using the apparatus  10 , the energy at the cutting element  16  is always activated during dissection. If the cutting element  16  were not activated during dissection, the tissue would be bluntly dissected solely by the pressure applied by the cutting element, and all blood vessels encountered within would be avulsed, resulting in bleeding. Accordingly, use of the apparatus  10  will require simultaneously cutting and sealing of vessel branches extending from the target vessel as the dissector tip  14  advances. In addition, because the cutting element  16  is always activated, to reduce the risk of thermal injury to target vessel, use of the apparatus  10  will require a single-pass maneuver, in which the cutting element  16  is always moved continuously distally. However, in an EVH procedure, even to achieve exposure of the upper/anterior surface of the vessel, the dissection process may involve repeated, small-scale, back-and-forth movements in a localized area. The user may also perform frequent pauses to identify tissues and to ascertain correct direction for device advancement. Thus, an EVH procedure using the continuously-activated heating element  16  of the apparatus  10  is likely to result in increased thermal exposure (due to a continuously activated cutting element  16  that is moved back-and-forth, or that is paused, next to target vessel), and consequently increasing the risk of inadvertent thermal damage to the target vessel. 
     Also, because the tissue being separated by the cutting element  16  is not visible to the user of the apparatus  10 , the user will not have sufficient information to make any adjustment in the speed of the movement of the cutting element  16  and/or any adjustment in the energy parameters for the cutting element  16 . For example, if there is a large vessel branch that is below the target vessel, the user will not be able to see the large branch because it is obscured from view by the target vessel. The user also will not be able to see the cutting element  16  treating the large branch because the contact point between the cutting element  16  and the large branch under the target vessel is likewise obscured from the view of the endoscope  18 . Accordingly, the user will not be able to make an adjustment by reducing the forward rate of advancement of the cutting element  16  to allow for slower coagulation (sealing) of the large vessel branch. This may result in uncontrolled bleeding at the target site. 
     Furthermore, the ring geometry of the cutting element  16  in the apparatus  10  poses another problem. In some cases, during the procedure, the user may encounter a large vessel branch. In such cases, the user may reduce speed of movement of the cutting element  16  accordingly to attempt to create a seal for the large branch. However, because all of the tissue to be cut is contacted by the energized ring-shape region of the cutting element  16 , all of the tissue surrounded by the cutting element  16  including the target vessel would be subjected to increased thermal exposure (due to the slower movement of the cutting element  16 ). This will create unintended thermal injury to the harvested vessel. The above assumes that the user of the apparatus  10  can see the large vessel branch. If the vessel branch is out of the view of the endoscope, the user cannot even see the vessel branch in time to make any adjustment in the energy delivery parameter. This can lead to an inadequate sealing of the vessel branch, and may even lead to conversion of the endoscopic procedure into open surgery due to loss of visibility from excessive blood in the endoscopic field from the inadequate sealing of the vessel branch. 
     Lastly, the ring geometry of the cutting element  16  has a fixed cross sectional opening that limits the tissue to be dissected to have a fixed pre-determined cross sectional dimension. Individual anatomical variations may present, such as parallel vein segments, which cannot be accommodated by the apparatus  10  without significant risk of unintended tissue injury or surgical error. 
       FIGS.  2 A and  2 B  illustrate another apparatus  200  for harvesting a vessel from a body (e.g., a human patient). The apparatus  200  includes a cannula  202  having a distal end  204  and a dissector  210  coupled to the distal end  204  of the cannula  202 . The dissector  210  is configured for advancing along a target vessel to create a tunnel next to the vessel e.g., from a skin incision of the patient, adjacent to the vessel to be harvested). The dissector  210  has a transparent portion for allowing an imaging device  260  housed in the cannula  202  to view therethrough. In one implementation, the dissector  210  has a cone shape, and an entirety of the cone shape dissector  210  may be transparent. 
     As shown in the figure, the apparatus  200  also includes an energy tool  220  moveably coupled to the cannula  202 . The energy tool  220  is configured to separate a pediculated vessel having at least a segment of the vessel and a pedicle around the segment of the vessel. In some embodiments, the energy tool  220  may be configured to provide monopolar or bipolar radiofrequency (RF) energy for tissue separation and/or sealing. In other embodiments, the energy tool  220  may be configured to provide heat (e.g., inductive heating, resistive heating, Joule heating, etc.) for tissue separation and/or sealing. In further embodiments, the energy tool  220  may be configured to provide ultrasonic energy for tissue separation and/or sealing. 
     In the illustrated embodiments, the apparatus  200  has a proximal handle  223  with a control  224  for allowing a user to control a delivery of power to an energy delivery element  225  on the energy tool  220 . For example, the control  224  may include one or more buttons for allowing the user to turn on the energy delivery element  225  to deliver energy, and to turn off the energy delivery element  225  to stop the delivery of energy. The control  224  may also include a button for allowing a user to adjust an amount of energy being delivered by the energy delivery element  225 . During use, the handle  223  is coupled to a power source (not shown), which supplies power for the apparatus  200 . In one implementation, the energy delivery element  225  may be one or more electrodes that provide RF energy. In another implementation, the energy delivery element  225  may be one or more heater elements that provide heat. In such cases, power may be supplied using a DC source to the heater element(s), which functions as resistive element(s) that heats up in response to the delivered direct current. In another implementation, the energy delivery element  225  may be one or more ultrasound applicators. In other embodiments, instead of implementing the control  224  at the handle  223 , the control  224  may be implemented as a foot switch. 
     The energy tool  220  is configured to move between a retracted position ( FIG.  2 A ) and an extended position ( FIG.  2 B ). In the retracted position, at least a distal portion of the energy tool  220  is housed within the cannula  202 . In the extended position, the distal portion of the energy tool  220  is outside the cannula  202 . The apparatus  200  may include a control  236  at the handle  223  configured to move the energy tool  220  from the retracted position to the extended position and vice versa. For example, the control  236  may be a button that can be pushed distally to extend the energy tool  220  from the cannula  202 , and be pulled proximally to retract the energy tool  220  back into the cannula  202 . 
     Also, in some embodiments, the energy tool  220  is configured to rotate with respect to the cannula  202 , so that the orientation of the energy tool  220  may be adjusted with respect to the cannula distal end  204 . The control for energy tool rotation may be incorporated into control  236 , or the apparatus  200  may include a separate control (not shown) at the handle  223  configured for rotating the energy tool  220 . In other embodiments, the energy tool  220  may be configured to deflect towards a longitudinal axis  240  (see broken line in a plurality of the figures) of the apparatus  200 /cannula  202  as the energy tool  220  moves from the retracted position to the extended position after deployed out of the cannula  202 . For example, the energy tool  220  may include an elastic elongated body that has a bent configuration. In such cases, the energy tool  220  is configured to bend radially inward towards the longitudinal axis  240  of the apparatus  200  as the energy tool  220  is deployed distally, and is configured to return to a relatively more rectilinear configuration after it is retracted back within the cannula  202 . This configuration is advantageous because it improves visibility of the energy tool  220  via the imaging device  260  housed inside the cannula  202 . The imaging device  260  will be described in further detail below. In other embodiments, the distal end of the energy tool (which comprises the energy delivery element  225 ) may be curved or angled inward toward the longitudinal axis  240 , for improved visibility by the imaging device  260 . In other embodiments, the distal tip(s) of the energy tool  220  may be tapered, to facilitate use for blunt dissection of tissues. In other embodiments, the energy tool  220  may be slidably coupled to the cannula, so that the energy tool  220  can move along a path that is parallel to the longitudinal axis  240  after the energy tool  220  is deployed out of the cannula  202 . 
     In the illustrated embodiments, the energy tool  220  is also moveable along a curvilinear path circumferentially around the longitudinal axis  240 . In particular, as shown in  FIG.  5   , the energy tool  220  is housed in a curvilinear slot  250 . The energy tool  220  may be extended out of the curvilinear slot  250  ( FIG.  6   ), and may be moveable circumferentially around axis  240 . This feature allows a user to place the energy tool  220  at a desired circumferential position with respect to the target tissue being operated on. This configuration also allows the energy tool  220  to move circumferentially around tissue surrounding a target vessel, and to separate such tissue from its surrounding tissue structure. The handle  223  of the apparatus  200  may have a control for allowing a user of the apparatus  200  to move the energy tool  220  circumferentially about the longitudinal axis  240  (or another axis) around the tissue. For example, the control may be a rotatable knob at the handle, which controls an amount of the circumferential movement of the energy tool  220 . In one implementation, the control may be the control  236 , and may include a button or a knob that can be slid (e.g., slid circumferentially) around a longitudinal axis of the handle  223  to thereby move the energy tool  220  within slot  250 . In addition to being movable circumferentially, the energy tool  220  may also be rotatable so that its orientation with respect to the longitudinal axis  240  (or another axis) may be optimized for tissue harvest. The axis about which the energy tool  220  rotates may be a longitudinal axis of the energy tool  220  (e.g., an axis that extends through the energy tool  220 ), or may be an axis that is parallel and spaced away from the longitudinal axis of the energy tool  220 . The control for rotation may be incorporated with the control  236 , or may be a separate control on the handle (not shown). 
     In some embodiments, the control  236  for moving (and, in some embodiments, rotating) the energy tool  220  and the control  224  for activating the energy tool  220  may be integrated on a handle portion of the handle  223  that is configured to move relative to another part of the handle  223 . In such cases, movement of the control  236  also results in movement of the control  224 . In other embodiments, the control  236  and the control  224  may be separately implemented on the handle  223  such that movement of the control  236  will not cause a corresponding movement of the control  224 . 
     As discussed, in some embodiments, the energy tool  220  may be configured to deflect towards the longitudinal axis  240  when it is deployed out of the cannula  102 . Such feature, when combined with the circumferential movement of the energy tool  220  (and, in some embodiments, rotation of the energy tool  220 ) is particularly advantageous. This is because while movement of the energy tool  220  allows a pediculated vessel (having tissue surrounding the target vessel) to be isolated, the deflection of the energy tool  220  may allow a user to control a thickness of the tissue in the pediculated vessel that is surrounding the target vessel. For example, in some cases, the amount of deflection may be controlled based on a degree in which the energy tool  220  is extended out of the cannula  202 . As the energy tool  220  is extended further out of the cannula  202 , the end of the energy tool  220  may move closer to the longitudinal axis  240 , and vice versa. 
     In some embodiments, the energy tool  220  is integrated with the cannula  202 , and is provided as a component of the apparatus  200 . In other embodiments, the apparatus  200  may not include the energy tool  220 . In such cases, the cannula  202  may have a lumen sized for accommodating an energy tool, which may be a commercially available energy instrument that can be detachably coupled to the cannula  202 . For example, a user of the apparatus  200  may select bipolar RF Maryland grasper forceps, VasoView HemoPro™ etc., as the energy tool  220 , and may insert such energy tool  220  into the cannula  202  for the vessel harvesting procedure. 
     The energy tool  220  may have an arcuate tip, a blunt tip, a sharp tip, a spatulate tip, a tapered tip, a forceps-style tip (e.g., straight, curved, or angled jaws), or a tip having any of other configurations. Any of these tip configurations may be tapered toward their distal ends, to facilitate blunt dissection of tissues. Alternatively, or additionally, the energy tool  220  may have an edge configured to cut tissue. For example, the energy tool  220  may include a blade. 
     In some embodiments, the energy tool  220  may be steerable. For example, the distal end of the energy tool  220  may include one or more steering wires configured to apply tension to pull the distal end of the energy tool  220  to thereby steer the energy tool  220  in one or more directions. In such cases, the handle of the apparatus  200  may include a steer control for allowing the user of the apparatus  200  to bend the distal end of the energy tool  220  in a desired direction. 
     As shown in  FIGS.  2 A,  2 B, and  2 C , the apparatus  220  further includes a retractor  230  moveably coupled to the cannula  202 . The retractor  230  is configured to engage with a portion of the pediculated vessel, and may be used to manipulate the portion of the pediculated vessel while the energy tool  220  is being used to operate on tissue to create other portion of the pediculated vessel. In some embodiments, the retractor  230  may be configured to lift the target vessel from the underside of the apparatus  200  to a position that improves visualization via the imaging device  260  of the target vessel and of the area to be treated (tissues to be harvested). This allows target tissue (that is to be operated by the energy tool  220 ) to be visible within the field of view of the imaging device  260 , rather than being obscured from view by the previously-harvested segment of target vessel. 
     The retractor  230  is configured to move from a retracted position ( FIG.  2 A ), to a partially-extended position ( FIG.  2 B ), and to a fully-extended position ( FIG.  2 C ), or vice versa. In the retracted position, at least a distal portion of the retractor  230  is housed within the cannula  202 . In the extended positions, the distal portion of the retractor  230  is outside the cannula  202 . The apparatus  200  may include a control  238  at the handle  223  configured to move the retractor  230  from the retracted position to the extended position and vice versa. For example, the control  238  may be a button that can be pushed distally to extend the retractor  230  from the cannula  202 , and be pulled proximally to retract the retractor  230  back into the cannula  202 . 
     As shown in the figure, the cannula  202  has a first side  232  and a second side  234  opposite from the first side  232 , and wherein retractor  230  is located closer to the first side  232  of the cannula  202  than to the second side  234  of the cannula  202 , and the energy tool  220  is located closer to the second side  234  of the cannula  202  than to the first side  232  of the cannula  202 . 
     In the illustrated embodiments, the retractor  230  is configured to translate along a path that is parallel to a longitudinal axis  240  of the apparatus  200 /cannula  202  as the retractor  230  moves from its retracted position to its extended position. In other embodiments, the retractor  230  is configured to deflect away from the longitudinal axis  240  as the retractor  230  moves from its retracted position to its extended position. In other embodiments, the retractor  230  may be configured to change from a lower-profile (e.g., with a collapsed geometry) when in a retracted position ( FIG.  2 D ) in a slot  231  to receive the retractor, to a larger-profile (e.g., with an expanded geometry) when in an extended position in which the retractor  230  is extended from the cannula  202  ( FIG.  2 E ). In some cases, the retractor  230  may comprise an elastic material, such as nitinol or a shape-memory alloy. In one implementation, the retractor  230  may include a spring wire. 
     In other embodiments, the retractor  230  is optional, and the apparatus  200  may not include the retractor  230 . 
     As shown in  FIG.  2 A , both the retractor  230  and the energy tool  220  are in retracted configurations. In this arrangement, the cannula  200  may be more easily inserted through a skin incision into the patient.  FIG.  3    illustrates an image from the imaging device  260  viewing through the dissector  210  of the apparatus  200  when the retractor  230  and the energy tool  220  are in retracted configurations. After the distal end  204  of the cannula  200  has been inserted into the patient and a short length of tunnel dissected adjacent to the target vessel, the retractor  230  and/or the energy tool  220  may be deployed into extended configurations ( FIG.  2 C ).  FIG.  4    illustrates an image from an imaging device viewing through a dissector of the apparatus of  FIG.  2 B  when the retractor and the energy tool are in extended configurations. In the configuration shown in  FIG.  2 B , at least a part of the retractor  230  and/or at least a part of the energy tool  220  is visible through the transparent portion of the dissector  210 . 
     As shown in  FIG.  2 A , the apparatus  200  further includes a lumen  262  in the cannula  202  configured for housing the imaging device  260 . The lumen  262  has a distal end  264 , and the energy delivery element  225  of the energy tool  220  can be extended distal of the lumen distal end  264  and distal end  268  of the imaging device  260 . Having the energy tool  220  be distal to the imaging device  260  during use of the energy tool  220  is advantageous because it allows the energy tool  220  to be viewable by the imaging device  260  while the energy tool  220  is operating on tissue. As shown in  FIG.  2 B , the imaging device  260  has a distal end  268 , and the energy tool  220  (i.e., the operative part of the energy tool  220 ) has been extended distal to the distal end  268  of the imaging device  260 . Also, as shown in  FIG.  2 B , an axis  270  extending from the distal end  268  of the imaging device  260  to the energy tool  220  traverses the transparent portion of the dissector  210 . This allows the energy tool  220  to be viewable by the imaging device  260  through the transparent portion of the dissector  210 . The imaging device  260  may be an endoscope (with lens and/or fiber optics), or may be an electronic image sensor (such as a CMOS device). 
     In some embodiments, the apparatus  200  may further optionally include a second imaging device. In such cases, the first imaging device (imaging device  260 ) may be configured for visualization of tissue dissection by the dissector  210 , and the second imaging device may be configured for visualization of an operation being performed by the energy tool  220 . The first and second imaging devices may be two endoscopes (e.g., with rod lens or fiber optics). Alternatively, one or each of the first and second imaging devices may include an electronic image sensor (e.g., CMOS device). 
     In the above embodiments, the longitudinal axis  240  of the apparatus  200 /cannula  202  is illustrated as corresponding with the dissector  210 . In other embodiments, the apparatus  200 /cannula  202  may have a longitudinal axis that is offset from the dissector  210 . For example, in some embodiments, the apparatus  200 /cannula  202  may have a central axis extending along a longitudinal length of the apparatus  200 , the dissector  210  is located at a first longitudinal axis offset from the central axis, and the energy tool  220  is located at a second longitudinal axis offset from the central axis, the second longitudinal axis being different from the first longitudinal axis. In such cases, the apparatus  200  may have two imaging devices associated with the dissector  210  and the energy tool  220 , respectively. For example, the apparatus  200  may have a first imaging device located at or close to the first longitudinal axis so that the first imaging device may be used to view the dissector  210  as the dissector  210  is operating on tissue. Similarly, the second imaging device may be located at or close to the second longitudinal axis so that the second imaging device may be used to view the energy tool  220  as the energy tool  220  is operating on tissue. The above feature is advantageous because during pedicle isolation, the energy tool  220  and the tissue being operated on may be visualized without the dissection tip  210  material in between them, which provides a clearer image of the endoscopic space during operation by the energy tool  220 . 
     A method for harvesting a vessel will now be described with reference to the apparatus  200 . The method will be described with reference to  FIGS.  7 - 12    which illustrate images provided from the imaging device  260  viewing through the dissector  210  of the apparatus of  FIG.  2 A  during a vessel harvesting procedure. 
     First, a skin of a patient is incised to create an entry point and to expose target vessel at the entry point (a proximal end of an endoscopic tunnel). 
     Next, a short length of the vessel at the entry point is mobilized. For example, such may be accomplished by dissecting around the entire circumference of the vessel at the entry point using standard surgical techniques. 
     Next, the apparatus  200  is inserted at the entry point. 
     Next, the apparatus  200  is advanced, while the dissector  210  is used to dissect a short length of tissue  700  along upper side of target vessel. An image obtained by the imaging device  260  viewing through the dissector  210  is shown in  FIG.  7   , particularly showing the short length of tissue  700  along the upper side of a target vessel. While the apparatus  200  is advanced, the energy tool  220  and the retractor  230  are retracted within the cannula  202 . As shown in  FIG.  8   , as the dissector  210  is advanced distally further, the image will show an extent  710  of the dissection. 
     Next, the apparatus  200  is retracted proximally so that the exposed length of tissue  700  and the mobilized section of the vessel at the entry point are in view through the transparent portion of the dissector  210 . An image obtained by the imaging device  260  viewing through the dissector  210  is shown in  FIG.  9   , particularly showing the extent  710  of the dissection, the tissue  700  along the upper side of the vessel, and the mobilized length  720  of the vessel. 
     Next, the retractor  230  is extended, and is positioned to engage against the mobilized length  720  of vessel at the entry point. The retractor  230  may be used to apply upward traction on the vessel. Thus, the positioning of the vessel may be affected by manipulation of the retractor  230 . In some cases, the degree of extension of the retractor  230  may be adjusted to vary the position of the vessel. The energy tool  220  is also extended from the cannula  202 , and is positioned along the vessel underside, while the retractor  230  is “lifting” the vessel, as shown in  FIG.  10 A  and  FIG.  10 B . An image obtained by the imaging device  260  viewing through the dissector  210  is shown in  FIG.  10 C , particularly showing both the retractor  230  and the energy tool  220  extended from the cannula  202 . As shown in the figure, in the extended configuration, the energy tool  220  is visible by the imaging device  260  viewing through the transparent portion of the dissector  210 . This allows the user of the apparatus  200  to view the tissue on which the energy tool  220  is operating. While the retractor  230  is lifting the mobilized length  720  of the vessel, the underside  730  of the mobilized length  720  of the vessel can be seen through the dissector  210  by the imaging device  260 . The user may then operate the energy device  220  to make a circumferential tissue separation  740  (and also sealing of blood vessels encountered during tissue separation) to separate tissue  750  (containing the target vessel  752 ) from its surrounding tissue  754 . In particular, the energy tool  220  may be moved substantially circumferentially (e.g., through a circumferential range that is more than 150°, or more than 180°, or more than 270°, more than 300°, etc., or 360°) around the tissue  750  that is surrounding the target vessel  752  to thereby circumferentially separate a pediculated segment of vessel. In some cases, the energy tool  220  may also be rotated to optimize the orientation of the energy delivery element  225  for tissue harvest. 
     The energy tool  220  may be used to bluntly dissect tissue below the vessel  752 . In some cases, if the energy tool  220  has a blade, the blade may be used to sharply dissect tissue below the vessel  752 . Alternatively, or additionally, the energy tool  220  may be activated to separate the tissue surrounding the vessel  752 . Also, the energy tool  220  may be activated to seal and sever branches of the target vessel, and/or to control localized bleeding during the tissue harvest. In some cases, the energy tool  220  may also be advanced and/or retracted and/or rotated or otherwise manipulated to optimize placement of the energy tool  220  at desired position(s) and/or orientations with respect to the target tissue. The energy tool  220  may be selectively manipulated and/or selectively activated to deliver energy until a desired length of pediculated vessel has been completely separated from the surrounding tissues. For example, as the energy tool  220  is being used to separate tissue  750  surrounding the target vessel  752  from the surrounding tissue  754 , the cannula  202  and/or the energy tool  220  may be advanced to separate a length (along the longitudinal axis of the vessel) of tissue  750  from the surrounding tissue  754 . An image obtained by the imaging device  260  viewing through the dissector  210  is shown in  FIG.  11   , particularly showing a length of pediculated vessel  778 , which includes tissue  750  surrounding the target vessel  752 . The mobilized length  720  of the vessel at the tunnel entry is also shown. Also, the surrounding tissue  754  (in a form of a channel  780 ) from which the tissue  752  is dissected is visible in the image. The channel  780  is a result of the length of the pediculated vessel  778  having separated from its surrounding tissue  754 . 
     After the segment of the pediculated vessel has been completely separated from the surrounding tissues  754 , the energy tool  220  and the retractor  230  are retracted into the cannula  202  to avoid inadvertent injury to the harvested tissue. 
     The above acts (i.e., advancing the cannula  202  to expose tissue above a length of target vessel, retracting the cannula  202 , extending the retractor  230 , extending the energy tool  220 , using the energy tool  220  to separate tissue, retracting the retractor  230  and the energy tool  220 ) are repeated until a desired length of pediculated vessel  778  has been isolated. An image obtained by the imaging device  260  viewing through the dissector  210  is shown in  FIG.  12   , particularly showing a desired length of pediculated vessel  778  that has been harvested. The pediculated vessel  778  includes tissue  750  surrounding the target vessel  752 . 
     Next, opposite ends of the isolated pediculated vessel are severed, and the harvested pediculated vessel is removed from the endoscopic tunnel. 
     The apparatus  200  and the above harvesting technique are advantageous in several aspects. First, when the retractor  230  and the energy tool  220  are extended distally relative to the cannula  202 , they are visible by the imaging device  260  viewing through the dissector  210 . Accordingly, the area undergoing treatment, i.e., tissue being sealed and cut by the energy tool, is fully visible by the user of the apparatus  200  during this portion of the procedure. This overcoming one of the main safety concerns exists in the apparatus  10  of  FIG.  1   . 
     Also, because the energy tool  220  is selectively activated by the user via the control  224  at the handle  223 , or by other methods (e.g., foot switch), the user is able to control when thermal energy is (or is not) applied to the tissue. Accordingly, the user is able to both precisely locate tissue to be operated on (i.e., via the imaging device  260  that views the tissue), and time energy delivery to the target tissue (i.e., via the control  224 ), rather than delivering energy continuously and indiscriminately to all tissue in contact with the cutting element of the apparatus  10  of  FIG.  1   . The ability to allow control of timing of energy delivery is advantageous. With the exception of procedures intended to induce cell necrosis (e.g., tissue ablation), it is desirable for safety and effectiveness to limit hyperthermic exposure of both the target and adjacent tissues. In the case of EVH, the ability to control the timing of energy delivery minimizes the risk of thermal injury to the CABG graft, injury that could negatively affect graft patency and revascularization efficacy. 
     In addition, with visibility of the area undergoing treatment, and with control of the timing and location of energy delivery provided by the energy tool  220 , the user is thus able to tailor his or her actions to optimize tissue sealing and cutting. For example, based on what the user can see through the transparent dissector  210 , the user may decide to bluntly and/or sharply dissect tissue with the energy tool without applying energy with the energy tool  220 , if needed. This minimizes the risk of inadvertent thermal injury to the harvested vessel. 
     Furthermore, the apparatus  200  and the method  1300  are advantageous because they allow a user to obtain a pediculated vessel  778  that includes the harvested vessel  752  surrounded by a layer of tissue  750 . Harvested vessel  752  that includes a surrounding perivascular tissue (tissue pedicle) may lead to improved long-term bypass graft patency, and therefore is advantageous over skeletonized vessel that does not have any tissue pedicle. The pediculated or “no-touch” harvesting technique and the resulting pediculated vessel may improve long-term performance of venous conduits used in CABG by protecting the vessel from mechanical trauma during harvest, providing structural support to the conduit and allowing perfusion of the conduit wall upon arterialization, and facilitating beneficial biochemical processes such as nitric oxide release. 
       FIG.  13    illustrates a method  1300  for harvesting a vessel from a body. First, an endoscopic space adjacent to a vessel to be harvested is created by a dissector, the dissector having a transparent portion (item  1304 ). In some embodiments, the dissector may be the dissector  210  described herein. Next, a pediculated vessel (having at least a segment of the vessel and a pedicle around the segment of the vessel) is separated by an energy tool, wherein at least a part of the energy tool is visible through the transparent portion of the dissector while the energy tool is being used (item  1306 ). In some embodiments, the energy tool may be the energy tool  220  described herein. 
     It should be noted that the energy tool  220  should not be limited by the examples of configurations discussed previously, and that the energy tool  220  may have other configurations in other embodiments. The energy tool  220  in  FIG.  7    through  FIG.  12    is shown as a monopolar RF electrode tip for simplicity (similar to one used for open-access, pediculated harvest of an internal thoracic artery), but can also be a forceps-type instrument such as VasoView HemoPro, or any other type of instrument configuration suitable for tissue coagulation and separation. For example, in other embodiments, the energy tool  220  may include a ring shape structure (e.g., the cutting element  16  described with reference to the apparatus  10  of  FIG.  1   ). The ring-shape structure may be mounted to a rod. Also, in some cases, the energy tool  220  may also include a first heating element at a leading end of the ring-shape structure, and a second heating element at a circumferential exterior surface of the ring-shape structure for providing energy to control bleeding. The second heating element may be proximal to the first heating element. The first and second heating elements may be selectively activated to perform different functions. For example, the first heating element may be selectively activated (e.g., by actuation of a first control at the handle  223 ) to cut tissue that is in contact by the leading end of the ring-shape structure as the ring-shape structure is advanced distally, and the second heating element may be selectively activated (e.g., by actuation of a second control at the handle  223 ) to control bleeding from tissue that has been cut by the leading end of the ring-shape structure. 
     In the embodiments disclosed a trocar such as a blunt tip trocar as described in U.S. Pat. No. 6,811,546, patent application Ser. No. 09/648660 filed Aug. 25, 2000 (herein incorporated by reference in its entirety), may be utilized and inserted through the incision or insertion point prior to the apparatus being introduced into the patient. 
     Although particular embodiments have been shown and described, it will be understood that they are not intended to limit the claimed inventions, and it will be understood to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the claimed inventions. The claimed inventions are intended to cover alternatives, modifications, and equivalents.