Abstract:
A dissection device for dissecting tissue from an elongate structure in a body is disclosed. The device comprises an elongate tubular member such as a cannula or other hollow tube and an inflatable elongate tubular balloon coupled to the elongate tubular member. The device further comprises device for connecting the elongate tubular balloon to an inflation source to inflate the elongate tubular balloon and device for deflating the elongate tubular balloon such as by a deflation valve. The elongate tubular balloon typically has multiple cylindrical chambers, is inverted during its uninflated state and everts during use.

Description:
FIELD OF THE INVENTION 
     This invention relates to harvesting blood vessels for coronary artery bypass grafting (hereinafter “CABG”), and more particularly to a device for facilitating harvesting internal mammary arteries for anastomosis to coronary arteries using minimally invasive procedures. Minimally invasive procedures are employed to minimize trauma to the patient in order to promote rapid healing and reduce the amount of pain during recovery. This invention relates particularly to a blood vessel harvesting apparatus that can be used for forming a small anatomic working space alongside an elongate vessel, particularly a blood vessel, and more particularly a small blood vessel such as an internal mammary artery (hereinafter “IMA”). The invention relates specifically to an assembly having a cannula and an assembled balloon. 
     BACKGROUND OF THE INVENTION 
     Diseases of the cardiovascular system affect millions of people each year and are a leading cause of death in the United States and throughout the world. The cost to society from such diseases is enormous both in terms of lives lost and the cost of treating cardiac disease patients through surgery. A particularly prevalent form of cardiovascular disease is a reduction in the blood supply to the heart caused by atherosclerosis or other conditions that create a restriction in blood flow in the arteries supplying blood to the heart. 
     Numerous surgical procedures have been developed to restore blood flow to the heart. For example, blockages can be treated with atherectomy or angioplasty, often followed by stent placement. But, when these methods of treatment cannot be used or have failed to clear the blocked artery, coronary bypass surgery may be indicated. 
     In the CABG procedure, the surgeon removes a portion of an artery or vein from another part of the body to use as a graft and installs the graft to bypass the obstruction. Alternatively, the surgeon dissects a healthy artery adjacent to the diseased artery, detaches one end of the healthy artery and connects that end to the coronary artery past the obstruction while leaving the other end attached to the natural arterial supply. Either of these two methods can restore normal blood flow to the heart. 
     The CABG procedure thus requires that one or more connections be established that bypass blockage in a diseased artery to restore an adequate blood flow. Typically, one end of a graft is sewn to the aorta, while the other end of the graft is sewn to a coronary artery, such as the left anterior descending artery (LAD), which provides blood flow to the left side of the heart. This procedure is known as a “free bypass graft.” Alternatively, the IMA pedicle may be dissected free of the chest wall, while still attached to its natural arterial supply, and its distal end attached to the blocked artery distal of the obstruction. This procedure is known as an “in situ bypass graft.” 
     In an in situ bypass graft, the IMA must be dissected free until there is sufficient length and slack in the IMA to ensure that the graft is not under tension and that it does not kink after it is repositioned. The IMAs, left and right, extend from the subclavian arteries in the neck to the diaphragm and run along the backside of the rib cage adjacent the sternum. They also contain side branches that require ligation to ensure that blood flow through the graft supplies the coronary artery, rather than being shunted off to other regions via various open branches. 
     Traditional methods for harvesting elongate vessels such as the IMAs involve the use of blunt probes that are pushed through body tissue to accomplish the dissection. (See Chin, U.S. Pat. No. 5,797,946, incorporated herein by reference). But, the force exerted during use of mechanical probes may lead to blood vessel trauma and branch avulsion. 
     Everting balloons, on the other hand, are more gentle and may be used to dissect along a vessel. But, it is difficult for the everting balloons presently available to follow vessels such as the IMAs. This is caused by the greater fixation that exists between these vessels and the tissue that surrounds them and to the characteristics of existing everting balloon dissectors. For example, a traditional everting balloon placed adjacent the saphenous vein in the leg, may squirt off in either direction upon inflation rather than track along the vein. This is due to the anatomical structures and to the fixation between the saphenous vein and the tissues that surround the vein. 
     Another problem associated with balloon dissectors adjacent a blood vessel is that after an initial dissection, a second dissection is more difficult. After connective tissue separating two layers of tissue has been ruptured due to an initial dissection, the healing process that ensues may involve formation of scar tissue. The scar tissue replacing the normal connective tissue is more difficult to dissect. The everting balloons presently available have difficulty tracking along a blood vessel through such scar tissue. 
     A need exists for new devices with adequate directional control to dissect small elongated cavities in tissue planes, particularly along the course of blood vessels, and more particularly, along the course of smaller blood vessels such as IMAs. A need also exists for new devices to dissect elongated cavities in tissue planes that have been dissected previously. 
     SUMMARY OF THE INVENTION 
     The present invention provides a cannula assembly for dissecting an elongated cavity in tissue planes, particularly along the course of a vessel, and more particularly along the course of a smaller blood vessel such as an IMA. The assembly includes an elongate tubular member comprising a hollow tube having a wall, proximal and distal ends and a lumen extending therethrough. In one embodiment, the hollow tube has a flattened or oval shaped distal end that is bent to facilitate insertion in between the ribs. Alternatively, the hollow tube can have an ogee offset at its distal end. 
     The dissection device also has means for connecting the hollow tube to an inflation source in order to inflate an elongate tubular balloon in fluid communication with the hollow tube. The means for connecting the hollow tube to an inflation source include an opening in the proximal end of the hollow tube or an opening in the wall of the hollow tube. Fluid, gas, or a liquid such as water or saline, can therefore be delivered from a syringe, a hand bulb pump, a piston pump, or the like to the interior of the elongate tubular balloon. 
     An elongate tubular balloon having an open proximal end and a closed distal end is coupled to the hollow tube and may be inverted and stored inside the hollow tube. The open proximal end of the elongate tubular balloon is coupled in a fluid-tight manner to the hollow tube. In one embodiment, the proximal end of the elongate tubular balloon is sealed around the outer wall of the hollow tube at its distal end. However, the open proximal end of the elongate tubular balloon may also be sealed to the lumen of the hollow tube or around the outer wall of the hollow tube at its proximal end. 
     The distal portion of the deflated elongate tubular balloon can be inverted toward the proximal portion and stored inside the hollow tube or in a reservoir formed in the balloon itself. Thus, in its deflated state, the distal end of the elongate tubular balloon may be stored proximal of its proximal end. Additional inward folds may be used to further shorten the length of the deflated elongate tubular balloon. 
     During inflation, this inverted embodiment of the elongate tubular balloon everts and advances beyond the distal end of the hollow tube until it is completely inflated. The fully inflated elongate tubular balloon can be as long as or longer than the hollow tube. 
     The dissection device also comprises a means for deflating the elongate tubular balloon, such as a vent or a deflation valve on the hollow tube. The elongate tubular balloon may be inflated and deflated multiple times during a single use. 
     The dissection device may also include means for retracting and re-inverting the elongate tubular balloon so that it can be re-inflated for multiple use during a surgical procedure. Means for retracting and re-inverting may include push rods, guide rods, or retraction lines comprising wire or string attached to the distal portion of the balloon. 
     It can be appreciated that the elongate tubular balloon of the present invention can have multiple chambers running substantially the entire length of the balloon. Multiple chambers serve to add lateral rigidity to the elongate balloon as it inflates while minimizing the cross-section of the dissected space created. The elongate tubular balloon can have one chamber, more preferably five chambers, more preferably four chambers, more preferably three chambers and most preferably two chambers. However, other embodiments having a greater number of chambers are also contemplated. 
     It has been found preferable to utilize a nonelastomeric balloon so that it is possible to control the shape of the dissected region. The fully inflated balloon can have an axial length of 5 to 30 inches, a width of 0.50 to 2.5 inches, and a height of 0.10 to 1.0 inches. The balloon can be formed as described in Kieturakis et al., U.S. Pat. No. 5,496,345, the entirety of which is incorporated herein by reference. 
     In one embodiment, the elongate tubular balloon has two cylindrical chambers running substantially the entire length of the balloon. The two chambers are in fluid communication with each other. A weld running substantially the entire length of the balloon may accomplish this double chambered configuration. The double chambered configuration decreases the likelihood that the everting balloon will track laterally off course as it everts, and it also eases insertion and tracking along the narrow space available between the sternum and the IMA and other surrounding tissue. 
     The double chambered configuration flattens the elongate tubular balloon, thus making it easier for the elongate tubular balloon to settle into a natural tissue plane. With a wider profile and a decreased height, the elongate tubular balloon is more likely to track along a natural tissue plane without changing its course laterally in an undesirable direction. If desired, the elongate tubular balloon may be curved to follow a desired path. 
     Moreover, with a left chamber and a right chamber, the lateral rigidity of the elongate tubular balloon increases for any given cross-section. This is because the width of an elongate tubular balloon that has been flattened by adding a weld along its length is greater than the height of the balloon. Thus, the moment of inertia will be higher in the plane defined by the width of the elongate tubular balloon than in the plane defined by the height of the elongate tubular balloon. Therefore, the double chambered configuration of the present invention will be less likely to bend transversely toward the left or right chambers as it everts along a natural tissue plane. Furthermore, it is not likely to bend in an upward or downward direction since it will be prevented from doing so by both the natural tissue layer above it and the natural tissue layer below it. Therefore, the double chambered everting elongate tubular balloon of the present invention is better suited for controlled dissection along smaller arteries such as the IMAs, which are tightly adhered to the tissue that surrounds them. 
     The flattened profile of the double chambered balloon is also desirable because the distance from the sternum to either the right or left IMA is about half an inch. This distance does not change substantially at any point along the length of either of the IMAs. Therefore, a flatter profile balloon is preferred to track along the narrow space available between the sternum and the IMA. Furthermore, a flat profile balloon is preferred over a thin and round balloon for dissecting along arteries such as IMAs for the reasons stated above with respect to lateral rigidity. 
     In a cannula assembly comprising a double chambered elongate tubular balloon, the balloon can be inverted by pulling or pushing the distal end of the balloon proximally through one of the chambers. Thus, in a deflated state, one of the chambers of the double chambered elongate tubular balloon is stored inside the other inverted chamber. Substantially the entire length of the deflated elongate tubular balloon can be stored inside the hollow tube. Upon inflation, the distal end of the balloon begins to evert outwardly and propagate in a distal direction until the balloon has completely everted and extends outside of the hollow tube. The propagation of the everting balloon can be facilitated by coating the internal surface, the external surface, or both surfaces of the balloon with a lubricant. 
     Alternatively, the two cylindrical chambers of the elongate tubular balloon can be formed by shifting the line of the weld to one side, thus resulting in one chamber having a larger cross-section than the other. This configuration may ease inversion and eversion, because there is a larger inverting chamber into which the smaller chamber follows during inversion and from which it exits during eversion. 
     In other embodiments of the present invention, the elongate tubular balloon has three, four or five chambers running substantially the entire length of the balloon. The chambers can be in fluid communication with each other or entirely separated and separately inflated. Welds running substantially the entire length of the balloon accomplish these configurations. Like the double-chambered elongate tubular balloon, the three, four and five-chambered configurations decrease the likelihood that the everting balloons will track off course as they evert, and they also ease insertion and tracking along the narrow space available between the sternum and the IMA. However, elongate tubular balloons having more than five chambers are also contemplated. 
     In another embodiment the dissection device is designed for use with an endoscope or laparoscope. The proximal end of the hollow tube of the dissection device is adapted to receive, and if necessary, seal around the scope. The scope can be inserted through the proximal end of the hollow tube and advanced toward the distal end of the hollow tube either while the elongate tubular balloon is being inflated or after the elongate tubular balloon is completely inflated and is in its everted position. In the case of a multi-chambered elongate tubular balloon, the scope can be, advanced through any one of the chambers. Alternatively, the scope can be independently inserted through the incision and advanced alongside the elongate tubular balloon as the balloon everts and dissects along the IMA or after the balloon is fully inflated. 
     Another embodiment of the dissection device comprises a guide rod, the distal end of which is inserted through the proximal end of the hollow tube and attached to the distal end of the elongate tubular balloon. Thus, eversion of the elongate tubular balloon and dissection along the IMA can be done either by advancing the guide rod along the IMA while inflating the balloon at the same time, or by advancing the guide rod along the IMA to the desired point and thereafter inflating the elongate tubular balloon. The guide rod can also be used to retract the elongate tubular balloon back into the hollow tube, at the same time re-inverting the elongate tubular balloon for withdrawal or subsequent use. A guide rod can be used either in a single chambered elongate tubular balloon or a multi-chambered elongate tubular balloon and may be attached to the distal end of the balloon, or may be loose. 
     Another embodiment of the dissection device comprises a guide rod, as above described, which is attached to a shorter balloon having a larger cross-section upon inflation. The hollow tube of this embodiment is longer than in the other embodiments earlier described to compensate for the decreased length of the balloon. Dissection is accomplished by 1) advancing the guide rod a short distance along, for example the IMA, for blunt dissection, probing between the IMA and the adjacent tissue in the plane initiated by this method of blunt dissection, 2) inflating the balloon to further dissect the IMA from the tissue adjacent to it, 3) deflating the balloon and 4) repeating steps one through three along the length of the IMA desired for the coronary artery bypass graft. 
     Another embodiment of the invention comprises a double-chambered elongate tubular balloon having a laterally extending thumb-shaped reservoir. A housing having a tubular balloon sleeve extending therefrom terminates the balloon and may receive a laparoscope. In its deflated and undeployed state, one chamber of the balloon is stored within the other chamber as previously described, and the distal portion of the balloon is stored inside the thumb-shaped reservoir. 
     Additional features of the invention will appear from the following description in which the preferred embodiments are set forth in detail in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Reference is next made to a brief description of the drawings, which are intended to illustrate devices for dissection adjacent elongate structures, particularly for harvesting blood vessels, particularly those useful in dissecting along IMAs. The drawings and detailed descriptions which follow are intended to be merely illustrative and are not intended to limit the scope of the invention as set forth in the appended claims. 
     FIG. 1 is a side elevational view of a dissection device of the present invention. 
     FIG. 1A is an alternate embodiment of the elongate tubular member of the dissection device of FIG. 1, wherein the elongate tubular member is flattened. 
     FIG. 1B is another alternate embodiment of the elongate tubular member of the dissection device of FIG. 1, wherein the distal end of the elongate tubular member has a round opening rather than a flattened opening. 
     FIG. 2 is a cross-sectional view taken along lines  2 — 2  in FIGS. 1 and 1B. 
     FIG. 3 is a cross-sectional view taken along lines  3 — 3  in FIGS. 1 and 1A. 
     FIG. 4 is a side elevational view of a dissection device of the present invention, said dissection device having an Ogee curve. 
     FIG. 4A is an alternate embodiment of the elongate tubular member of the dissection device of FIG. 4, wherein the distal end of the elongate tubular member has a flattened opening rather than a round opening. 
     FIG. 4B is another alternate embodiment of the elongate tubular member of the dissection device of FIG. 4, wherein the elongate tubular member is flattened. 
     FIG. 5 is a cross-sectional view taken along lines  5 — 5  in FIGS. 4 and 4A. 
     FIG. 6 is a cross-sectional view taken along lines  6 — 6  in FIGS. 4A and 4B. 
     FIG. 7 is a side elevational view of a hollow tube with an inverted elongate tubular balloon. 
     FIG. 7A is a cross-sectional view taken along lines  7 A— 7 A in FIG.  7 . 
     FIG. 8 is an alternate embodiment of the device depicted in FIG. 7, wherein the elongate tubular balloon is sealed to the luminal surface of the hollow tube. 
     FIG. 9 is another alternate embodiment of the device depicted in FIG. 7, wherein the elongate tubular balloon is wrapped over the proximal end of the hollow tube and sealed to the outer wall at the proximal end of the hollow tube. 
     FIG. 10 is a side elevational view of another alternate embodiment of the device depicted in FIG. 7, wherein the elongate tubular balloon has an inflation lumen. 
     FIG. 11 is a cross-sectional view taken along lines  11 — 11  in FIGS. 8 and 9. 
     FIG. 12 is a side elevational view of a hollow tube with an inverted elongate tubular balloon as fluid is introduced into the hollow tube. 
     FIGS. 12A,  12 B and  12 C are side elevational views of the elongate tubular balloon of FIG. 12 as it everts due to introduction of fluid. 
     FIGS. 13 is a side elevational view of a hollow tube with an inverted double-chambered elongate tubular balloon. 
     FIG. 13A is an alternative embodiment of the device depicted in FIG. 13, wherein the elongate tubular balloon has an inflation lumen. 
     FIG. 14 is a cross-sectional view taken along line  14 — 14  in FIG.  13 . 
     FIG. 15 is a side elevational view of a hollow tube with an inverted double-chambered elongate tubular balloon as fluid is introduced into the hollow tube. 
     FIGS. 15A,  15 B and  15 C are side elevational views of the double-chambered elongate tubular balloon of FIG. 15 as it everts due to introduction of fluid. 
     FIG. 16 is a plan view of an everted elongate tubular balloon. 
     FIG. 17 is a plan view of an everted double-chambered elongate tubular balloon. 
     FIG. 17A is a three-dimensional view of the double-chambered elongate tubular balloon of FIG.  17 . 
     FIG. 17B is a three-dimensional view of an alternate embodiment of the double-chambered elongate tubular balloon of FIG. 17, wherein one of the chambers has a smaller cross-sectional area than the other chamber. 
     FIG. 18 is a plan view of an everted three-chambered elongate tubular balloon. 
     FIG. 19 is a cross-sectional view taken along line  19 — 19  in FIG.  16 . 
     FIG. 20 is a cross-sectional view taken along line  20 — 20  in FIG.  17 . 
     FIG. 21 is a cross-sectional view taken along line  21 — 21  in FIG.  18 . 
     FIG. 22 is a side elevational view of another embodiment of a dissection device with a hollow tube and an inverted balloon attached thereto, the dissection device having a separate endoscope for use therewith. 
     FIG. 23 is a side elevational view of another embodiment of a dissection device with a hand operated inflation pump and separate endoscope for use therewith. 
     FIG. 24 is a side elevational view of another embodiment of a dissection device having an inverted elongate tubular balloon stored inside of a hollow tube and a longitudinally adjustable guide rod attached to the distal end of the inverted elongate tubular balloon. 
     FIG. 24A is a side elevational view of the device of FIG. 24, wherein the guide rod has pushed the uninflated elongate tubular balloon completely out of the hollow tube. 
     FIG. 24B is a side elevational view of the device of FIG. 24A, wherein the elongate tubular balloon is in a fully inflated state. 
     FIGS. 24C and 24D are side elevational views of two more embodiments of the fully inflated elongate tubular balloon depicted in FIG. 24B, wherein the elongate tubular balloons are shorter and have larger diameters than the elongate tubular balloon depicted in FIG.  24 B. 
     FIG. 24E is a top view of the device depicted in FIG. 24 with separate endoscope used therewith. 
     FIG. 25A is a cross-sectional view taken along line  25 — 25  in FIG. 24, showing a retractable piston stop in an upright, deployed position. 
     FIG. 25B is an alternative cross-sectional view taken along line  25 — 25 , showing a retractable piston stop in a retracted state. 
     FIG. 26 is a plan view of another embodiment of a dissection device illustrating the storage of the inverted double-chambered elongate tubular balloon of FIG. 13 within a thumb-shaped balloon reservoir. 
     FIG. 27 is a plan view of the apparatus of FIG. 26 showing the double-chambered elongate tubular balloon fully distended after inflation. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the embodiment illustrated in FIG. 1, an IMA dissection device  10  includes an elongate tubular member  20 , a deflation valve  30 , a hand pump  40 , an inflation port  50 , and a handle  60 . The elongate tubular member  20  comprises a hollow tube  21  having an opening  25  in its proximal end, the opening  25  being in fluid communication with the inflation port  50  and the deflation valve  30 . The distal end of the hollow tube  21  is bent to facilitate insertion in between the ribs and has an opening  27 , which can either be flattened, as shown in FIGS. 1,  1 A and  3 , or circular as shown in FIGS. 1B and 2. Furthermore, the entire length of the hollow tube  21  can be flattened as shown in FIG. 1A or can have a circular cross-section, as shown in FIG.  1 B. 
     Hand pump  40  is a means for inflating balloons that are stored in the hollow tube  21 , as shown in later figures. However, other means of inflation include a syringe in fluid communication with an inflation lumen, such as the inflation lumen  66 , shown in FIG.  10 . 
     The hollow tube  21  can have an ogee offset at its distal end as shown in FIGS. 4,  4 A and  4 B. The distal end of the hollow tube  21  can either have a circular opening, as shown in FIGS. 4 and 5, or a flattened opening, as shown in FIGS. 4A,  4 B and  6 . Furthermore, the entire length of the hollow tube  21  can be flattened as shown in FIG. 4B or can have a circular cross-section, as shown in FIG.  4 . 
     As shown in FIGS. 7,  8  and  9 , an elongate tubular balloon  70  is coupled to the hollow tube  21 . The elongate tubular balloon  70  has a proximal end  75  with an opening and a distal end  77  with no opening and an optional retraction line  72  attached to the luminal surface  73  of the inverted portion of the elongate tubular balloon  70  at its distal end  77 . The open proximal end  75  of the elongate tubular balloon  70  is coupled in a fluid-tight manner to the hollow tube  21  by sealing the entire circumference of the luminal surface  73  of the proximal uninverted end  75  of the elongate tubular balloon  70  around the outer wall  24  of the hollow tube  21  at its distal end. This is accomplished by pulling the opening of the proximal end  75  of the elongate tubular balloon  70  over the distal end and distal opening  27  of the hollow tube  21 , and using, for example, an adhesive material, a sealing ring or collar, or just a tight fit to seal the luminal surface  73  of the proximal uninverted end  75  of the elongate tubular balloon  70  to the outer wall  24  of the hollow tube  21  at its distal end. 
     The elongate tubular balloon  70  may be sealed to the hollow tube  21  in other configurations as well. For example, the outer wall  74  at the proximal end  75  of the elongate tubular balloon  70  may be sealed to the luminal surface  23  of the hollow tube  21 , as shown in FIG.  8 . In another example, the outer wall  74  at the proximal end  75  of the elongate tubular balloon  70  may be wrapped over the proximal opening  25  of the hollow tube  21  and sealed to the outer wall  24  at the proximal end of the hollow tube  21 , as shown in FIG.  9 . 
     Alternatively, it is contemplated that an elongate tubular balloon  69 , as shown in FIG. 10, has no openings, other than an opening  65  for connection to an inflation lumen  66 . The elongate tubular balloon  69  is inverted and stored inside the hollow tube  21 , but need not be sealed to the hollow tube  21 . Moreoever, the opening  65  may be on the lateral wall  67  of the elongate tubular balloon  69  and not on the proximal end  61  of the elongate tubular balloon  69 . Thus, both the proximal end  61  of the elongate tubular balloon  69  and the distal end  68  of the elongate tubular balloon  69  may be closed. The inflation lumen  66  may be introduced into the luminal space  22  of the hollow tube  21  through either the proximal opening  25  of the hollow tube  21  or a lateral opening  24  on the hollow tube  21 , as shown in FIG.  10 . 
     In the embodiments shown in FIGS. 7,  7 A,  8 ,  9 , and  11  the elongate tubular balloon  70  is in a deflated state and is inverted and stored in the luminal space  22  of the hollow tube  21 . FIG. 7A is a cross-section taken through line  7 A— 7 A of FIG.  7 . For the sake of visual clarity, FIG. 7A does not show contact between the luminal surface  73  of the inverted portion of the elongate tubular balloon  70  and the luminal surface  23  of the hollow tube  21 . However, it can be appreciated that the inverted balloon  70  may be in contact with the luminal surface  23  of the hollow tube  21  at various cross-sectional areas along the length of the elongate tubular balloon  70 . 
     FIG. 11 is a cross-section taken through  11 — 11  of FIGS. 8 and 9. Again for the sake of visual clarity, FIG. 11 does not show contact between the luminal surface  73  of the uninverted portion of the elongate tubular balloon  70  and the luminal surface  73  of the inverted portion of the elongate tubular balloon  70 . Likewise, there is no contact shown between the luminal surface  23  of the hollow tube  21  and the outer wall  74  of the elongate tubular balloon  70 . However, it can be appreciated that the luminal surface  73  of the uninverted portion of the elongate tubular balloon  70  and the luminal surface  73  of the inverted portion of the elongate tubular balloon  70  may be in contact at various cross-sectional areas along the length of the elongate tubular balloon  70 . Likewise, the luminal surface  23  of the hollow tube  21  and the outer wall  74  of the elongate tubular balloon  70  may also be in contact at various cross-sectional areas along the length of the elongate tubular balloon  70 . 
     Inflation of the elongate tubular balloon  70  is shown in FIGS. 12,  12 A,  12 B and  12 C. In the initial deflated and inverted state, distal end  77  of the elongate tubular balloon  70  is proximal of the proximal end  75  of the elongate tubular balloon  70 . However, as fluid is introduced into the luminal space  22  of the hollow tube  21  and inflation progresses, the proximal end  75  of the elongate tubular balloon  70  begins to inflate distally, pulling the distal end  77  in a distal direction toward the opening  27  of the hollow tube. Fluid forces the inverted elongate tubular balloon  70  to evert until the elongate tubular balloon  70  is fully inflated and entirely outside the luminal space  22  of the hollow tube  21 , as shown in FIG.  12 C. It can also be appreciated that in the case of either of the embodiments shown in FIGS. 8 and 9, fluid can be delivered directly to the luminal space  79  of the uninverted portion of the elongate tubular balloon  70 . Furthermore, in the embodiments shown in FIGS. 8 and 9 only the inverted portion of the elongate tubular balloon  70  will propagate distally and will advance outside the luminal space  22  of the hollow tube  21  upon inflation. The retraction line  72  can be used to retract and re-invert the elongate tubular balloon  70  back into the hollow tube  21  for multiple use during a procedure. 
     In another embodiment as shown in FIG. 13, the elongate tubular balloon  80  comprises two cylindrical chambers: an outer chamber  81  and an inner chamber  82 . As shown in FIG. 17, the two chambers  81  and  82  are in fluid communication with each other, but are separated for substantially the entire length of the elongate tubular balloon  80  by a weld  87 . The proximal end  85  of the double chambered elongate tubular balloon  80  comprises a single chamber  90 . The single chamber  90  splits into two chambers  81  and  82  at the point where the weld  87  begins. At the point where the weld  87  ends, which is at the distal end  89  of the double chambered elongate tubular balloon  80 , the two chambers  81  and  82  may converge into one. 
     Although FIG. 13 shows the two chambers  81  and  82  converging at the point  94  where the weld  87  ends, it is contemplated that the weld  87  may run to the very distal end  89  of the double-chambered elongate tubular balloon  80 . In an embodiment in which the weld  87  runs to the very distal end  89  of the elongate tubular balloon  80 , the two chambers  81  and  82  remain separated at the distal end  89 . 
     The two chambers  81  and  82  may be symmetrical as shown in FIG. 17A, or the outer chamber  81  may have a larger cross-section than the inner chamber  82  as shown in FIG.  17 B. In the deflated and inverted state, the two chambers  81  and  82  are stored in the luminal space  22  of the hollow tube  21 . Furthermore, chamber  82  is stored in the inverted outer chamber  81 . 
     FIG. 14 is a cross-sectional view of FIG. 13, showing the inner chamber  82  stored in the inverted outer chamber  81 . FIG. 14 also shows the weld  87  separating the two chambers  81  and  82 . For the sake of visual clarity, FIG. 14 does not show the inverted outer wall  83  of the outer chamber  81  in contact with the outer wall  86  of the inner chamber  82  at any point other than the weld  87 . Nor does FIG. 14 show contact between the inverted luminal surface  88  of the outer chamber  81  and the luminal surface  23  of the hollow tube  21 . However, it can be appreciated that there may be contact between the inverted outer wall  83  of the outer chamber  81  and the outer wall  86  of the inner chamber  82  at various cross-sectional areas along the length of the double chambered elongate tubular balloon  80 . Likewise, there may be contact between the inverted luminal surface  88  of the outer chamber  81  and the luminal surface  23  of the hollow tube  21  at various cross-sectional areas along the length of the double chambered elongate tubular balloon  80 . 
     In another embodiment as shown in FIG. 17B, the cross-sectional area of the outer chamber  81  is larger than the cross-sectional area of the inner chamber  82 . This asymmetrical configuration eases inversion because the greater diameter of the outer chamber  81  serves to decrease the amount of contact and friction between the inverted outer wall  83  of the outer chamber  81  and the outer wall  86  of the inner chamber  82 . Likewise, the asymmetrical configuration also eases eversion, because there is more space hence less friction between the inverted outer wall  83  of the outer chamber  81  and the outer wall  86  of the inner chamber  82  during eversion. Also, the double-chambered elongate tubular balloon  80  may be lubricated to decrease the amount of friction and ease inversion and eversion. For example, luminal surfaces  84  and  88  of the respective chambers  82  and  81  and/or the outer walls  86  and  83  of the respective chambers  82  and  81  may be lubricated. The lubricant used can be clear if an endoscope or laparoscope is to be inserted into the balloon for visualization of dissected tissue layers. 
     Inflation of the double chambered elongate tubular balloon  80  is shown in FIGS. 15,  15 A,  15 B and  15 C. In the initial deflated and inverted state, distal end  89  of the double chambered elongate tubular balloon  80  is proximal of the proximal end  85  of the double chambered elongate tubular balloon  80 . However, as fluid is introduced into the luminal space  22  of the hollow tube  21  and inflation progresses, the double chambered elongate tubular balloon  80  begins to inflate and evert distally from its proximal end  85 , pulling the distal end  89  in a distal direction toward the opening  27  of the hollow tube. Fluid forces the inverted outer chamber  81  of the double chambered elongate tubular balloon  80  to evert, while the inner chamber  82  is expelled, progressively rotating out of the outer chamber  81 . FIG. 15C shows the double chambered elongate tubular balloon  80  fully inflated and entirely outside the luminal space  22  of the hollow tube. 
     After the double chambered elongate tubular balloon  80  is fully inflated, it can be deflated by a variety of means including a deflation valve or a vent on the hollow tube  21 . Once the elongate tubular balloon  80  is deflated it can be removed from the patient, or it can be retracted and re-inverted back into the hollow tube  21  with a retraction line  92 . The retraction line  92  may be attached to the luminal surface of the elongate tubular balloon at its distal end  89  as shown in FIG.  15 C. Alternatively, if the weld  94  runs to the very distal end  89  of the elongate tubular balloon  80  so that the two chambers  81  and  82  are separated at the distal end, the retraction line  92  may be attached to the luminal surface  88  of the outer chamber  81  at its distal end. The retraction line  92  can be used to re-invert the double chambered elongate tubular balloon  80  for multiple use during a procedure. The retraction line may comprise, for example, wire, string or nylon thread. 
     The open proximal end  85  of the elongate tubular balloon  80  is coupled in a fluid-tight manner to the hollow tube  21  by sealing the entire circumference of the luminal surface  91  of the proximal uninverted end  85  of the elongate tubular balloon  80  around the outer wall  24  of the hollow tube  21  at its distal end. This is accomplished by pulling the opening of the proximal end  85  of the elongate tubular balloon  80  over the distal end and distal opening  27  of the hollow tube  21 , and using, for example, an adhesive material, a sealing ring or collar, or just a tight fit to seal the luminal surface  91  of the proximal uninverted end  85  of the elongate tubular balloon  80  to the outer wall  24  of the hollow tube  21  at its distal end. 
     The elongate tubular balloon  80  may be sealed to the hollow tube  21  in other configurations as well. For example, the outer wall  93  at the proximal end  85  of the elongate tubular balloon  80  may be sealed to the luminal surface  23  of the hollow tube  21 , as in the single chambered elongate tubular balloon  70  shown in FIG.  8 . In another example, the outer wall  93  at the proximal end  85  of the elongate tubular balloon  80  may be wrapped over the proximal opening  25  of the hollow tube  21  and sealed to the outer wall  24  at the proximal end of the hollow tube  21 , as in the single chambered elongate tubular balloon  70  shown in FIG.  9 . 
     Alternatively, it is contemplated that a double-chambered elongate tubular balloon  99 , as shown in FIG. 13A, has no openings, other than an opening  95  for connection to an inflation means  96 . The double-chambered elongate tubular balloon  99  is inverted, with one chamber stored inside the other as previously described. The double-chambered elongate tubular balloon  99  itself is stored inside the hollow tube  21 , but need not be sealed to the hollow tube  21 . Moreoever, the opening  95  may be on the lateral wall  97  of the elongate tubular balloon  99 , as shown in FIG. 13A, or on the proximal end  91  of the elongate tubular balloon  99 . The inflation lumen  96  may be introduced into the luminal space  22  of the hollow tube  21  through either a lateral opening  24  on the hollow tube  21 , as shown in FIG. 13A, or the proximal opening  25  of the hollow tube  21 . 
     Alternatively, as shown in FIGS. 18 and 21, the elongate tubular balloon  100  can comprise three chambers,  110 ,  111  and  112 . In an inverted three chambered configuration, two of the chambers would be stored inside the inverted outer wall of the third chamber. The three chambered configuration may have a large proximal opening such as the one shown in FIG. 18, or a small lateral or proximal opening for connection to an inflation means, such as shown in FIGS. 10 and 13A. For ease of inversion and eversion, the chamber storing the other two chambers during the deflated and inverted state can have a larger cross-section than the other two chambers. Lubricant may also be used on the outer and/or inner walls of the elongate tubular balloon to ease inversion and eversion. Furthermore, although not shown, configurations with more than three chambers are also contemplated. 
     In another exemplary embodiment illustrated in FIG. 22, a dissection device  200  includes a hollow tube  205 , an inflation valve  210 , a deflation valve  220 , an inverted elongate tubular balloon  230 , a valve, such as a duckbill valve  260 , to seal the proximal end  250 , and a scope seal  270 . The hollow tube  205  has an opening  280  on its distal end adapted to receive a scope, an opening  290  on its proximal end and a lumen extending therethrough. The lumen of the hollow tube  205  comprises a luminal surface  215  and a luminal space  217 . The inflation valve  210  and deflation valve  220  are in fluid communication with the lumen of the hollow tube  205 . 
     The elongate tubular balloon  280  in its inverted and inflated state is stored within the hollow tube  205 . The proximal end  235  of the elongate tubular balloon  230  may be sealed in a fluid-tight manner around the outer wall  225  of the hollow tube  205  at its distal end. Alternatively, the proximal end  235  of the elongate tubular balloon  230  may be sealed in a fluid-tight manner to the luminal surface  215  of the hollow tube  205  or around the outer wall  215  of the hollow tube  205  at its proximal end, such as in FIGS. 8 and 9. The elongate tubular balloon  230  may be multi-chambered such as shown in FIGS. 17,  17 A,  17 B,  18 ,  20  and  21 . The balloon  230  is preferably formed from a substantially transparent material to facilitate laparoscopic observation through the balloon  230  as described below. 
     The scope seal  270 , which can be made of silicone or other semi-rigid material, may be coupled to the luminal surface  215  of the hollow tube  205 , distal to the proximal opening  290  and proximal to the duckbill valve  260 . Alternatively, the scope seal  270  may be coupled to the hollow tube  205  by wrapping it around the outer wall  225  of the hollow tube  205  at the proximal end of the hollow tube  205 , or sealing it to the proximal end of the hollow tube  205 . The duckbill valve  260  can also be made of silicone or other semi-rigid material and may be coupled to the luminal surface  215  of the hollow tube  205  distal to the scope seal  270 . 
     The elongate tubular balloon  230  can be inflated with inflation means such as a syringe or a hand pump in fluid communication with the inflation port  210 . During inflation, the elongate tubular balloon  230  everts, propagating distally beyond the distal opening  280  of the hollow tube. The everting balloon  230  dissects tissue as it propagates within the mass of body tissue. Either during inflation or once the elongate tubular balloon  230  is fully inflated, the distal end  310  of the scope  300  can be inserted through the proximal opening  290  of the hollow tube  205 , pushed through the scope seal  270  and the duckbill valve  260 , and into the inflated elongate tubular balloon  230 . With the scope  300 , the surgeon can view a blood vessel, such as an IMA, its branches and the connective tissue that is dissected by the elongate tubular balloon  230 . Alternatively, the dissection device  200  can be made integrally with the scope  300 . 
     FIG. 23 shows the dissection device of FIG. 22 coupled to a piston pump  400 , which is used to inflate the elongate tubular balloon  230 . The piston pump  400  comprises a stationary handle  450 , a spring actuated trigger  410 , a pin  470 , a piston rod  430 , a piston head  420 , piston stops  480 , a one-way fluid intake valve  440 , and a scope port  460 . The trigger  410  is pivotally hinged by hinge  470  to the handle  450 . The trigger  410  has an upper arm  415  that is secured to the proximal end of the piston rod  430 . The distal end of the piston rod  430  is coupled to the proximal end of the piston head  420 . The piston rod  430  has an opening on its proximal end, an opening on its distal end, and a lumen extending therethrough. The piston head  420  has an opening on its proximal end, an opening on its distal end, and a lumen extending therethrough as well. The piston head  420  is secured to the piston rod  430 , and the proximal opening of the piston head  420  and the distal opening of the piston rod  430  are in fluid communication. 
     The elongate tubular balloon  230  is inflated by squeezing the trigger  410 , causing the upper arm  415  to pivot distally toward the dissection device  200 . The pivoting action of the upper arm  415  forces the piston rod  430  to push the piston head  420  distally, forcing fluid trapped inside the elongate tubular member  205  to inflate the elongate tubular balloon  230 . Valving can provide for multiple stroke operation of the pump  400 . The elongate tubular balloon  230  can be single chambered as shown in FIGS. 16 and 19 or multi-chambered as shown in FIGS. 17,  17 A,  17 B,  18 ,  20 , and  21 . As the piston head  420  moves distally, the fluid intake valve  440  is closed, thus sealing the inside of the hollow tube  205 . The trigger  410  will move back to its original position upon release due to the action of a spring (spring not shown). Thus, the upper arm  415  will move proximally away from the hollow tube  205 , pulling the piston rod  430 , which in turn pulls the piston head  420  until the piston head rests against the piston stops  480 . The distal movement of the piston rod  420  causes a suction effect due to the vacuum inside the lumen of the hollow tube  205 , opening the one-way fluid intake valve  440  and allowing fluid to enter the lumen of the hollow tube  205 . Thus, the elongate tubular balloon  230  can be inflated with further squeezing and releasing of the trigger  410 . 
     The scope  300  can be inserted into the scope port  460 , which has an opening adapted to receive a scope  300  and a scope seal  490 . The scope  300  is pushed past the scope seal  490  and through the hollow piston rod  430 . A duckbill valve  495 , secured to either the distal end of the hollow piston rod  430  or the lumen of the piston head  420 , extends into the hollow piston head  420 . The scope seal is pushed through the duckbill valve  495  and into the hollow tube  205 . This can be done either before inflation, during inflation, or after complete inflation of the elongate tubular balloon  230 , because the movement of the scope  300  is independent of the movement of the piston pump  400 . Once the elongate tubular balloon  230  is in an inflated and everted state, the scope can be advanced into the everted elongate tubular balloon  230  in order to view a blood vessel, such as an IMA, its branches and the connective tissue that is dissected by the elongate tubular balloon  230 . In the case of a multi-chambered elongate tubular balloon  230 , the scope can be advanced into whichever chamber is best positioned for viewing a particular area. Finally, the deflation valve  220 , can be used to deflate the elongate tubular balloon  230 . 
     The piston pump  400  can either be made integrally with the dissection device  200 , or can be made separately and adapted for use with the dissection device  200 . Moreover, the piston pump  400  can be made integrally with the scope  300 . 
     Alternatively, the scope  300  can be independently inserted through the same incision in which the dissection device  200  is inserted. The scope  300  can be advanced alongside the everting elongate tubular balloon  230 . 
     In an alternative embodiment, as shown in FIG. 24, the dissection device  200  of FIG. 22 can be used with a piston pump  500  adapted for use with a guide rod  600 . The piston pump  500  comprises an L-shaped trigger  510 , a handle  520 , an upper arm  550 , the proximal end of which is attached at an angle to the shoulder of the L-shaped trigger by a pin  560 , a piston head  530  and piston stops  540 . The piston head  530  has an opening on its proximal end, an opening on its distal end, and a lumen extending therethrough. A guide rod  600  has a handle  610 , a blunt end  620 , a shaft  630  extending from the handle  610  to the blunt end  620 , and multiple triangular piston stops  640  that look like dorsal fins when deployed along the shaft  630 . The dissection device  200  has supports  670  to guide the guide rod  600  through the hollow tube  205 . 
     The piston pump  500  inflates the elongate tubular balloon  230  in the same manner as previously described with respect to FIG.  23 . The blunt end  620  of the guide rod  600  can be secured to the inverted lumen  235  of the elongate tubular balloon  230  at the distal end of the elongate tubular balloon  230 . Thus, the guide rod  600  can be used to retract the elongate tubular balloon  230  after deflation for withdrawal or subsequent use. Alternatively, the guide rod  600  need not be secured to the elongate tubular balloon  230 . The guide rod  600  can be pushed manually through the elongate tubular balloon  230 , everting the balloon  230  as it propagates along a blood vessel, such as an IMA, as shown in FIGS. 24 and 24 a.  The guide rod  600  can be pushed either concurrent with or previous to balloon inflation. 
     Alternatively, the guide rod  600  can be advanced by squeezing the piston pump  500 , which will push the piston head  530  distally. The piston head  530  will push against one of the retractable piston stops, thus forcing the guide rod  600  forward. Releasing the trigger  510  will spring the trigger back into its original position (spring not shown), pulling the piston head  530  back against the piston stops  540 . The piston head  530  will depress and slide over the piston stops  640  that are in its way, because the piston stops  640  protrude from the shaft  630  of the guide rod  600  at an angle and retract into the shaft  630  when the piston head  530  slides over them from a distal to proximal direction. The shaft  630  can be hollow along its entire length or can have hollow sections in the areas of the piston stops  640  to accommodate for the retraction of the piston stops  640 . 
     FIGS. 25A and 25B show a cross-section through the guide rod  600  and one of the piston stops  640 , the piston stop  640  being in an upright, unretracted position in FIG. 25A and a retracted position in FIG.  25 B. The retractable piston stops  640  are spaced at distances which will allow the guide rod  600  to advance to a maximum distance at the same time that the elongate tubular balloon  230  is fully inflated, as shown in FIG.  24 B. The retractable piston stops  640  are also all retractable at the same time so that the guide rod  600  can be retracted proximally. As indicated in FIG. 24A, the guide rod  600  can be advanced to a maximum distance before the elongate tubular balloon  230  is inflated. 
     The elongate tubular balloon  230  can have various shapes. It can be multi-chambered as shown in FIGS. 17,  17 A,  17 B,  18 ,  20  and  21 , in which case, the guide rod  600  could be guided through any one of the chambers. It can also be shorter and have a larger cross-section such as the balloon  800  shown in FIG. 24C or the balloon  700  shown in FIG.  24 D. With respect to the balloon  700  shown in FIG. 24D, the hollow tube  710  can be longer to compensate for the shorter length of the balloon  700 . Dissection using the guide rod  600 , hollow tube  710  and balloon  700  can be carried out by first tunneling with the guide rod  600  and hollow tube  710 , followed by inflating the balloon  700 , then deflating the balloon, and finally repeating the above steps until dissection along the desired length of a blood vessel, such as an IMA, has been achieved. 
     Also, as shown in FIG. 24E, a scope  300  can be inserted through the incision alongside the dissection device  200 . With the scope  300 , the surgeon can view a blood vessel, such as an IMA, its branches and the connective tissue that is dissected by the blunt end  620  of the guide rod  600  and the elongate tubular balloon  230 . It must be appreciated that any openings in the balloon, whether for strings, rods or scopes must be appropriately sealed. 
     Another exemplary embodiment of a dissection device  900  according to the invention is illustrated in FIGS. 26 and 27. The dissection device  900  is provided with a laterally extending thumb-shaped reservoir  920 , which is itself part of the double-chambered elongate tubular balloon  910 . A housing  930  having a tubular balloon sleeve  960  extending therefrom terminates the balloon  910  and may receive a laparoscope (not shown) if visualization is required or desirable for the procedure contemplated. An instrument seal  940 , which may be of the type described in Fogarty et al., U.S. Pat. No. 5,690,668, is mounted in the housing  930  to provide a fluid-tight seal between the interior of the housing  930 , which is in fluid communication with the interior of the double-chambered balloon  910 , and a laparoscope. The balloon sleeve  960  may be formed integrally with the housing  930  or as a separate member. The balloon can be inflated through inflation lumen  950 , which is in fluid communication with an inflation means (not shown), a dissection device  900  includes a hollow tube  960  and a double-chambered elongate tubular balloon  910  having a laterally extending thumb-shaped reservoir  920 . 
     The double-chambered elongate tubular balloon  910  is substantially similar to the balloons utilized in connection with previous embodiments, such as those illustrated in FIGS. 13,  15 A,  15 B, and  15 C. Thus, elongate tubular balloon  910  in its uninflated state may be inverted with chamber  907  stored inside of chamber  905 . The two chambers are separated by weld  912 , which may run substantially the entire length of the balloon  910  or the entire length of the balloon  910 . If the weld runs the entire length of the balloon, then each chamber may be inflated with its own inflation lumen. 
     The balloon  910  may further be folded inwardly to reduce its predeployment length as shown in FIG.  27 . The proximal end of the balloon  910  is open and may be terminated in a fluid-tight manner in the housing  930 , as shown, or on an outer surface of the balloon sleeve  960 . The balloon  910  is preferably formed from a substantially transparent material to facilitate laparoscopic observation through the balloon  910 . 
     Prior to use, the deflated balloon  910  is inverted, with chamber  907  being stored in chamber  905 , and the distal portion of the balloon  908  is folded inwardly to shorten the overall length of the balloon  910 . The distal portion  908  of the inverted, folded balloon  910  is pushed into the reservoir  920 , as show in FIG.  27 . Additional folds may be provided, as necessary, to further shorten the deflated balloon  910  and to make it possible to store the majority of the balloon  910  in the reservoir  920 . 
     The specificity of the embodiments described is not intended to be limiting as to the scope of the invention.