Patent Publication Number: US-2007100363-A1

Title: Aortic lancet

Description:
BACKGROUND OF THE INVENTION  
      1. Technical Field  
      The present invention is directed generally to methods and apparatus for effectuating surgical incisions. More specifically, the present invention is related to methods and apparatus for creating a hole in a vessel wall including an aorta wall.  
      2. Description of Related Art  
      During surgical procedures, such as placement of a ventricular assist device, blood vessel anastomosis, aortotomy, gastrotonomy, enterotomy, or access to other hollow organs and vessels, it is useful to have specialized tools to create a circular opening in the wall of the vessel or organ. Tools have been developed for use in surgery that create such openings. For example, often the goal of heart surgery is to produce a blood flow path around the diseased areas of coronary arteries. A saphenous vein graft can be used by forming an opening in the wall of an ascending aorta, and anastomosing the opening to a proximal end of the saphenous vein. To form the opening in the wall of the aorta, an incision can be made using surgical scalpels and/or scissors. An aortic punch can then be used in order to attempt to obtain a clean, accurate somewhat larger opening in the aortic wall. Obtaining a clean and accurate opening is extremely important since an opening which is not formed cleanly and accurately often is frayed, albeit microscopically. As a result, the connection of the proximal end of the saphenous vein thereto may not be as reliable, and complications during or after surgery may result. Because heart surgery necessarily often entails a difference between life and death of a patient, it is extremely important to maximize the probability of success of every aspect of the surgical procedure. To this end, it is desirable to try to obtain as clean and as accurate an opening as possible in the wall of the aorta before grafting the saphenous vein thereto.  
      Once such procedure is described and illustrated in U.S. Pat. No. 6,187,022. A conventional linear incision along an aorta vessel utilizing a conventional scalpel is first made. Such procedure requires the surgeon to make an educated guess as to the length of the incision. After the incision is made, a punch is inserted into the vessel wall through the incision to make a clean circular hole in the vessel wall. Unfortunately, the diameter of the hole made in the vessel wall is sometimes less than the length of the educated-guess incision made by the scalpel resulting in lateral nicks protruding from opposite sides of the hole in the vessel wall, as illustrated by  FIG. 2  of the &#39;022 Patent. These nicks necessitate special suturing to prevent blood leakage, and add points of weakness at the site of the vessel graft. Alternatively, a surgeon may make an incision that is smaller than the diameter of the punch such that lateral nicks might be avoided. However, such an incision necessitates stretching of the tissue for insertion of the aortic punch anvil. The stretching of the tissue can decrease the patency of the resulting graft or cause aortic dissection wherein the layers of the aortic wall separate from one another. The &#39;022 Patent&#39;s solution to this problem is to use a cruciate-shaped blade to make a cross-shaped incision for the initial incision into the vessel wall, and subsequently completing the opening with an aortic punch.  
      An additional problem a surgeon faces with making such incision is that the heart, in some procedures, is not arrested and is permitted to beat, which can impart some movement on the vessel that the surgeon is attempting to make an incision. Such movement can make an accurate incision more difficult. Further, if a surgeon applies too much pressure and pushes the scalpel or blade too far into the vessel, damage to the opposite or back wall of the vessel can occur. Consequently, a need exists for an improved incision device or lancet. The improved device should protect the surgeon&#39;s fingers from being cut with the blade, and it should provide a way to minimize or eliminate cuts that could be accidentally made during surgery. The improved device should minimize or eliminate nicks outside the diameter of the punched hole in the vessel wall and should provide a clean cut.  
      As discussed above, after an incision is made, an aortic punch is used to obtain the opening in the aortic wall. One example of such punch is illustrated by U.S. Pat. No. 5,827,316 (the &#39;316 Patent). One problem with prior art punches is that the distal end of the anvil is typically flat, or has a tip with a vertex having a large angle. As a result, sufficient pressure must be supplied to penetrate the incision. As the amount of pressure required increases, the potential for an undesirable fissure or tear in the vessel wall increases as well. Further, additional pressure can cause undesirable stretching of the tissue remaining after the hole in the vessel has been made. Consequently, a need exists for an aortic punch that can minimize or eliminate fissures, or tears, and/or stretching that can occur in a vessel wall.  
     SUMMARY OF THE INVENTION  
      The present invention relates to an improved system for making a precise incision and circular hole in a vessel wall. In one aspect, the system comprises a lancet having a retractable shield surrounding a blade. The retractable shield helps to prevent any accidental cutting that can occur during surgical conditions. When an incision is made, the shield simultaneously retracts as the blade penetrates the front vessel wall. The blade length is less than the inside diameter of the vessel wall to prevent accidental penetration of the back vessel wall. In one aspect, the system comprises a punch having a tapered cutter with a circumferential edge for receiving an anvil cutting edge. The anvil is placed through the incision in the front vessel wall and actuated to cause a helical shearing force as the anvil cutting edge axially slides past the rotary circumferential cutting edge to produce a clean-cut hole in the vessel wall.  
      The above as well as additional features and advantages of the present invention will become apparent in the following written detailed description.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will be best understood by reference to the following detailed description of illustrative embodiments when read in conjunction with the accompanying drawings, wherein:  
       FIG. 1  is an exploded perspective view of the lancet in accordance with one embodiment of the present invention.  
       FIG. 2  is a perspective view of the lancet in accordance with one embodiment of the present invention.  
       FIG. 3  is a partial side view of the lancet inserted in a vessel wall in accordance with one embodiment of the present invention.  
       FIG. 4  is a partial side view of the lancet in accordance with one embodiment of the present invention.  
       FIG. 5  is a side view of the aortic punch in accordance with one embodiment of the present invention.  
       FIG. 6  is a partial side view of the aortic punch inserted in a vessel wall in accordance with one embodiment of the present invention.  
    
    
     DETAILED DESCRIPTION  
       FIG. 1  is an exploded perspective view of the lancet in accordance with one embodiment of the present invention. The lancet  100  comprises a blade  120  attached to a handle  110 . In one embodiment, the handle comprises a first section and a second section that can be removably snap-fit together. In one embodiment, the first section of the handle  110  comprises at least one and preferably two male members  112  disposed through an aperture  122  in the blade  120  and into a female member  114  in the second section to attach the blade  120  to the handle  110 . The blade  120  thereby protrudes from the handle  110 . A retractable blade shield  130  is slidably attached to the handle  110  and surrounds the blade  120 . In one embodiment, the blade shield  130  is clear or transparent so that the blade  120  is visible.  
      The blade shield  130  helps to minimize accidental cutting that can occur in surgical conditions. For example, it should be noted that during surgical conditions, slippery fluids such as blood and sudden movements created by a beating heart in conjunction with the decreased tactile function that can occur with a surgeon wearing latex gloves create conditions that can result in an accidental cutting. Further, the blade shield  130  can be gripped by a surgeon&#39;s fingers to aid in initial placement of the blade  120 . Thus, the blade shield  130  can help protect the surgeon&#39;s fingers during surgical conditions and/or ensure that an incision is made only at the desired place on the vessel. In one embodiment, the retractable blade shield  130  is kept in an extended position around the blade  120  by a spring, or other equivalent resistance means. In one embodiment, the spring  140  comprises a resistance that is less than the insertion force required to make an incision into a vessel.  
       FIG. 2  is a perspective view of the lancet in accordance with one embodiment of the present invention.  FIG. 4  is a partial side view of the lancet in accordance with one embodiment of the present invention. Referring to  FIGS. 2 and 4 , a protective cover  200  can be press-fit over the retractable blade shield and blade and over a portion of the handle as an additional safety precaution. Further, the protective cover  200  can protect the blade  122  from potential contaminants when the lancet  100  is not in use.  
       FIG. 3  is a partial side view of the lancet inserted in a vessel wall in accordance with one embodiment of the present invention. As depicted in  FIG. 3 , the lancet is shown without a protective cover and with the retractable shield  130  in the fully retracted position. The blade  120  having a blade length BL is thereby exposed within the vessel  300 . The blade length BL is defined as the length of the blade  130  that is exposed when the blade shield is fully retracted. In one embodiment, the blade length BL is between about 1 millimeter and about 20 millimeters and more preferably between about 5 millimeters and about 15 millimeters. In one embodiment, the blade length BL is dimensioned such that during blade penetration of the front vessel wall  310 , the back wall  320  cannot be penetrated. Consequently, in one embodiment, the blade length BL is substantially less than or equal to the inner wall vessel diameter D. In one embodiment, the blade comprises a primary and secondary blade similar to that disclosed in U.S. Pat. No. 6,187,022 and makes a cruciate-shaped incision having an incision diameter ID. In one embodiment, the end of the handle is tapered  160  to provide a surgeon with a better finger grip.  
       FIG. 5  is a side view of the aortic punch in a vessel wall in accordance with one embodiment of the present invention.  FIG. 6  is an enlarged partial side view of the aortic punch in accordance with one embodiment of the present invention. Referring to  FIG. 5  and  FIG. 6 , the aortic punch  500  is shaped and designed to be used by a surgeon using one of his or her hands. The aortic punch includes a thumb button  510  pushable into an opening  512  in a finger grip body  514  which is a non-rotating member. A pair of finger seats  520  can be attached to the finger grip body  514  and can be shaped to be engaged by a surgeon&#39;s fingers. To operate the aortic punch  500 , a surgeon can grab the punch in his or her hand, place a thumb on the thumb button  510  and place both an index finger tip and a middle finger tip on the finger seats  520 . After an incision has been made by a lancet, the surgeon can maneuver the aortic punch  500  so that the parabolic-shaped anvil  600  on the end of the shaft is inserted into the incision in the front vessel wall  310  (shown in  FIG. 3 ).  
      After the anvil  600  is inserted into the incision in the front vessel wall  310 , the surgeon can push on the thumb button  510  with his or her thumb while holding the finger seats  520  with his or her fingers. As the thumb button  510  is pushed into the finger grip body  514  through the opening  512 , the hollow body member  516  attached to a tapered cutter  618  having a sharp circumferential edge  632  simultaneously rotates as the piston  640  and anvil  600  moves downward through the opening defined by the sharp circumferential edge  632 . An opening in the front vessel wall  310  is created by a helical shearing force as the anvil cutting edge  630  axially slides past the rotating circumferential cutting edge  632 . The helical shearing force imparted creates a clean-cut hole in the vessel wall. The helical shearing force also minimizes or eliminates fissures, tears, and/or stretching in the vessel area adjacent the hole. The diameter of the tapered piston  640  can be sized so as to prevent fluids and vessel tissue from entering the hollow body member  516  while permitting the piston  640  to slidably move in the axial direction within the tapered cutter  618 .  
      The parabolic shaped anvil  600  comprises a vertex  610  at the distal end of the anvil and an anvil cutting edge  630  having an anvil diameter AD at the proximal end of the anvil  600 . One advantage of the parabolic shape is that it permits easy perpendicular insertion of the anvil  600  through the incision which can help to minimize or eliminate stretching in the remaining tissue adjacent the hole formed by the anvil. The slope of the anvil sides  620  determines the penetration angle at which the anvil enters the vessel wall  310 . A smaller penetration angle (e.g. narrower parabola) results in less insertion force of the anvil  600  into the vessel which minimizes undesirable vessel fissures and is less likely to cause undesirable tearing upon insertion. Consequently, a relatively longer anvil length AL can be used to provide an anvil having the proper anvil diameter AD at the anvil cutting edge  630  and an optimal penetration angle.  
      In one embodiment, and referring to  FIG. 3  and  FIG. 6 , the incision diameter ID created by the blade  120  is less than or equal to the anvil diameter AD. This advantageously provides a hole having no lateral nicks that are common place in prior art devices. Hence, the punch of the present invention can be applied to a straight or cruciate incision. One advantage of the helical shearing force provided by the parabolic-shaped anvil  600  of the present invention is that it permits an incision diameter ID to be made that is smaller than the anvil diameter AD. Smaller incision diameters are desirable because it minimizes the undesirable fissures and/or tearing in the vessel wall because less insertion force is required to make smaller incisions. The present invention thereby provides a system for making a precise incision and circular hole in the aorta that eliminates lateral side notches from the aortotomy.  
      While this invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.