Abstract:
A hemostat-type device for ablative treatment of tissue, particularly for treatment of atrial fibrillation, is constructed with features that provide easy and effective treatment. A swiveling head assembly can allow the jaws to be adjusted in pitch and roll. Malleable jaws can permit curved lesion shapes. A locking detent can secure the jaws in a closed position during the procedure. An illuminated indicator provides confirmation that the device is operating. A fluid delivery system simplifies irrigated ablation procedures.

Description:
RELATED U.S. APPLICATION DATA  
       [0001]    This application claims priority from U.S. Provisional Patent Application No. 60/422,330 filed Oct. 30, 2002, incorporated herein by reference in its entirety. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to surgical tools and procedures generally and relates more particularly to the use of electrosurgical ablation to treat atrial fibrillation.  
           [0003]    In patients with chronic atrial fibrillation or having atrial tachycardia that is resistant to medical treatment, the Maze III procedure has been employed. This procedure controls propagation of the depolarization wavefronts in the right and left atria by means of surgical incisions through the walls of the right and left atria. The incisions create blind or dead end conduction pathways, which prevent re-entrant atrial tachycardias from occurring. While the Maze procedure is successful in treating atrial fibrillation, the procedure is quite complex and is currently practiced by only a few very skilled cardiac physicians in conjunction with other open-heart procedures. The procedure also is quite traumatic to the heart, as in essence the right and left atria are cut into pieces and sewed back together, to define lines of lesion across which the depolarization wavefronts will not propagate.  
           [0004]    It has been suggested that procedures similar to the Maze procedure could be instead performed by means of electrosurgical ablation, for example, by applying radiofrequency (RF) energy to internal or external surfaces of the atria to create lesions across which the depolarization wavefronts will not propagate. Such procedures are disclosed in U.S. Pat. No. 5,895,417, issued to Pomeranz, et al., U.S. Pat. No. 5,575,766, issued to Swartz, et al., U.S. Pat. No. 6,032,077, issued to Pomeranz, U.S. Pat. No. 6,142,944, issued to Swanson, et al., U.S. Pat. No. 5,871,523, issued to Fleischman, et al. and U.S. Pat. No. 6,502,575, issued to Jacobs et al., all incorporated herein by reference in their entireties. Hemostat type, electrosurgical or cryo-ablation devices for use in performing such procedures are described in U.S. Pat. No. 5,733,280 issued to Avitall, U.S. Pat. No. 6,237,605 issued to Vaska, et al, U.S. Pat. No. 6,161,543, issued to Cox, et al., PCT published Application No. WO99/59486, by Wang and in pending U.S. patent application Ser. No. 09/747,609 filed Dec. 22, 2000 by Hooven, et al., all incorporated herein by reference in their entireties. In order for such procedures to be effective it is desirable that the electrosurgically created lesions are continuous along their length and extend completely through the tissue of the heart (i.e. transmural lesions). These goals may be difficult to accomplish employing dry ablation electrodes or electrodes applied only to the interior or exterior surfaces of the heart tissue. Electrosurgical hemostats configured to allow fluid—assisted tissue ablation are generally described in U.S. Pat. No. 6,096,037, issued to Mulier, also incorporated by reference in its entirety.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention provides an ablation hemostat, particularly useful in performing a maze type procedure by applying ablation energy (e.g. RF energy) across the walls of the left and right atria by means of delivery means located on either side of the atrial walls. In a preferred embodiment of the invention, the hemostat is provided with elongated RF electrodes malleable to assume various straight and curved configurations to produce lesions that approximate the incisions that would occur during the Maze III procedure as described in the book ‘ Cardiac Surgery Operative Technique’  by Donald B. Doty, M. D. at pages 410-419, incorporated herein by reference in its entirety, or to allow creation of lines of lesion corresponding to the incisions that would be provided by other forms of the Maze procedure. The hemostat may be useful in conjunction with other procedures as well.  
           [0006]    The hemostat of the present invention is provided with a number of useful features, particularly adapted to ease its use in conjunction with creating elongated lines of lesion. While the disclosed and most preferred embodiments of the invention employ all of the improved features, each of the improved features discussed below is believed valuable in and of itself to improve the performance and ease of use of prior art electrosurgical hemostats.  
           [0007]    In order to allow the hemostat to produce straight and curved elongated lesions, the jaws of the hemostat are malleable to allow the physician to set the specific jaw configuration. The jaws are fabricated of a flexible plastic sheath enclosing elongated bendable or malleable backbones and electrodes to achieve this result. The backbones and electrodes may be shaped by the physicians&#39; fingers into a desired curvature and serve to retain the curvature imparted to them until reshaped for creation of a subsequent lesion. The backbones take the form of elongated plates having thicknesses substantially less than their widths to encourage bending of the jaws within a single plane so that the opposed electrodes can more readily be maintained in alignment along their lengths. The backbones are also preferably tapered along their length such that the width of the backbones diminishes as they approach the tips of the jaws, in turn making it easier to provide the jaws with the curvature extending over the entire length of the jaws.  
           [0008]    The hemostat includes an elongated handle portion or handle and a jaw assembly mounted at the distal end of the handle. The jaw assembly preferably includes two elongated jaws carrying RF electrodes or other ablation elements, extending along the lengths of the jaws and arranged so that they are located on opposite sides of tissue compressed between the jaws. In preferred embodiments, the electrodes take the form of fluid irrigated RF electrodes, however, other ablation mechanisms such as cyroablation, direct current ablation, microwave ablation, and the like may be substituted for RF ablation electrodes.  
           [0009]    The jaw assembly preferably includes a swiveling head assembly adapted to allow the jaws to be rotated relative to the axis of the handle (roll) and allowing the jaws to pivot around an axis perpendicular to the axis of the handle (pitch). Adjustment of the jaws relative to the handle (pitch and roll) is made manually by the physician, and the jaws are retained in their desired orientation relative to the handle by means of detent mechanisms.  
           [0010]    The jaws are mounted to one another at a pivot point and are opened and closed by means of a trigger, mounted to the handle, which applies tensile force to a cable or other tension member extending along the handle. The cable, when pulled, pulls the jaws toward one another to compress tissue between them. In the particular embodiments disclosed, the cable is anchored offset from the pivot point to a first one of the jaws. The first jaw is fixed, i.e. retains its location during jaw closure regardless of the pitch and roll adjustment made to the jaw assembly. The second, pivoting jaw, is mounted to the fixed jaw at a pivot point and the cable passes around an internal boss within the pivoting jaw, also offset from the pivot point. Application of tension to the tension member pulls the internal boss in the pivoting jaw toward the cable mounting point in the fixed jaw and thereby causes movement of the jaws toward one another. Tissue placed between the jaws can thus be engaged by the jaws and compressed between the jaws as the jaws close.  
           [0011]    The cable enters the jaw assembly along its rotational (roll) axis, so that rotation of the jaw assembly about the roll axis does not alter the operation of the cable. The cable extends around a shoulder internal to the fixed jaw, which shoulder remains essentially in the same location regardless of the pitch adjustment of the jaw assembly, so that pitch adjustment of the jaw assembly does not significantly effect operation of the cable to close the jaws.  
           [0012]    In preferred embodiments, the trigger mechanism is provided with a locking detent mechanism which may be engaged or disengaged and which, when engaged, retains the trigger in its position, in turn maintaining compression of the jaws against tissue located there between. The detent mechanism in a preferred embodiment is activated or deactivated by means of a sliding button, mounted to the handle.  
           [0013]    In preferred embodiments, irrigation fluid is provided to the electrodes by means of plastic tubing that is provided with in-line flow limiters, controlling the delivery rate of irrigation fluid to the electrodes. This feature allows the use of a simplified fluid pumping mechanism and also provides balanced, even fluid flow to the electrodes. In its preferred embodiment, the trigger, when released, also serves to block fluid flow to the electrodes, preventing irrigation while the hemostat is not in use.  
           [0014]    In one embodiment, the RF electrode assembly can take the form of an elongated porous material coupled to the fluid delivery lines and carrying elongated electrode wires on their inner, facing services. The electrode wires may be coupled to the porous material by means of a series of spikes extending from the electrode wires into the porous material. Other alternative electrode designs may of course be substituted, including electrodes comprised of elongated coil electrodes or perforated tubular electrodes with porous material located either inside of or surrounding the electrodes. For example, a perforated tubular electrode can be seated inside a porous polymeric support such the electrode is entirely within the support. In this embodiment, conductive fluid flows through the interior of the electrode, out of perforations in the electrode and through the porous support to facilitate ablation such that the polymeric support, not the electrode, is on the facing surfaces of the jaws to contact the tissue to be ablated.  
           [0015]    The hemostat may optionally also include a thermocouple, located along the jaws allowing for temperature controlled feedback of power provided to the RF electrodes and may also preferably includes an indicator LED mounted to the handle, activated to indicate that delivery of RF energy is underway. The hemostat is usable useable with conventional RF generators. Alternatively, the hemostat may be used in conjunction with an RF generator system, which incorporates a transmurality measurement and automatic shut off of ablation energy. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a plan view of an assembled hemostat according to one embodiment of the present invention.  
         [0017]    [0017]FIG. 2 is an exploded view of the jaw assembly of the hemostat of FIG. 1.  
         [0018]    [0018]FIG. 3A is a cross-section view through the jaw assembly of the hemostat of FIG. 1.  
         [0019]    [0019]FIG. 3B is a cross-section view through lines  3 B- 3 B of FIG. 3A.  
         [0020]    [0020]FIG. 4 is an end view in partial cross-section of the proximal end of the knuckle portion of the jaw assembly of the hemostat of FIG. 1.  
         [0021]    [0021]FIG. 5A is a plan view of an elongated tubular electrode used in the hemostat of FIG. 1.  
         [0022]    [0022]FIG. 5B is an enlarged cross-section view taken along lines  5 B- 5 B of the electrode illustrated in FIG. 5A.  
         [0023]    [0023]FIG. 6A is an end view of an electrode support as used in the jaw assembly of the hemostat of FIG. 1.  
         [0024]    [0024]FIG. 6B is a cross-section view taken along lines  6 A- 6 A of FIG. 6A illustrating the electrode support.  
         [0025]    [0025]FIG. 7A is an end view of an electrode sheath as included in the jaw assembly of the hemostat of FIG. 1.  
         [0026]    [0026]FIG. 7B is a cross-section view taken along lines  7 B- 7 B of FIG. 7A illustrating the electrode sheath.  
         [0027]    [0027]FIG. 8A is a plan view of the right half of the handle employed in the hemostat of FIG. 1.  
         [0028]    [0028]FIG. 8B is an enlarged plan view of the distal portion of the right handle half illustrated in FIG. 8A.  
         [0029]    [0029]FIG. 8C is a cross-section view taken along lines  8 C- 8 C through the right handle half of the hemostat of FIG. 1.  
         [0030]    [0030]FIG. 9A is a plan view of the left half of the handle employed in the hemostat of FIG. 1.  
         [0031]    [0031]FIG. 9B is an enlarged plan view of the distal portion of the left handle half illustrated in FIG. 9A.  
         [0032]    [0032]FIG. 9C is a cross-section view taken along lines  9 C- 9 C through the left handle half of the hemostat of FIG. 1.  
         [0033]    [0033]FIG. 10 is an enlarged view of the trigger portion of a hemostat as in FIG. 1 with the left handle half removed.  
         [0034]    [0034]FIG. 11A is a perspective view of a trigger lock as employed in the trigger assembly of the hemostat as in FIG. 1.  
         [0035]    [0035]FIG. 11B is a plan view of the trigger lock of FIG. 11A.  
         [0036]    [0036]FIG. 12A is a top plan view of a link arm as employed in the trigger assembly of an assembled hemostat as in FIG. 1.  
         [0037]    [0037]FIG. 12B is a side plan view of the link arm of FIG. 12A.  
         [0038]    [0038]FIG. 13A is a side plan view from the distal end of the trigger employed in the trigger assembly of the hemostat of FIG. 1.  
         [0039]    [0039]FIG. 13B is a cross-section view taken along lines  13 B- 13 B through the trigger of FIG. 13A.  
         [0040]    [0040]FIG. 14 is a cut-away view of the proximal portion of the hemostat of FIG. 1 with the left handle half removed.  
         [0041]    [0041]FIG. 15A is a sectional view through an alternative embodiment of an upper and lower jaw for use with a hemostat otherwise as in FIG. 1.  
         [0042]    [0042]FIG. 15B is a cross-sectional view taken along lines  15 B- 15 B of FIG. 15A.  
         [0043]    [0043]FIG. 16A is a plan view of an electrode extension employed in the alternative embodiment of the upper and lower jaw depicted in FIGS. 15A and 15B.  
         [0044]    [0044]FIG. 16B is an expanded view of a barb of the electrode extension depicted in FIG. 16A. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0045]    In reference to FIG. 1, a preferred embodiment of the hemostat of the present invention generally comprises an elongated handle assembly or handle  10  having a jaw assembly  90  mounted at handle distal end  15 , a trigger  20  intermediate the handle proximal and distal ends  95  and  15 , and a strain relief  60  located at handle proximal end  95 . An elongated cable is coupled to the strain relief  60  and comprises a fluid conduit  70  extending to a proximal fluid fitting  75  adapted to be coupled to a source of conductive fluid and a multi-conductor electrical cable  80  extending to a proximal electrical connector  85  adapted to be coupled to an electrosurgical unit. The trigger  20  is employed to move the jaws of the first or lower jaw assembly  40  with respect to the second or upper jaw assembly  30  of the jaw assembly  90  together to compress tissue therebetween to allow for creation of a linear RF ablation by electrically conductive fluid emitted from electrodes and contacting tissue or direct contact of the electrodes located along the upper and lower jaws  35  and  45 .  
         [0046]    The jaw assembly  90  includes the upper jaw assembly  30 , the lower jaw assembly  40 , and a swivel assembly  50 , discussed in more detail below. The upper jaw and lower jaw assemblies  30  and  40  have opposed upper and lower jaws  35  and  45 , respectively, each comprising a fluid assisted elongated electrode assembly. The upper and lower jaw assemblies  30  and  40  support elongated electrodes, discussed in more detail below, each coupled to one of the insulated conductors within conduit  70  extending proximately through the strain relief  60  to electrical connector  85 . Each of the jaws  35  and  40  of respective upper and lower jaw assemblies  30  and  40  are also coupled to fluid conduit  80  enabling delivery of saline or other conductive fluid from a source coupled to fitting  75  along the lengths of the opposed jaws  35  and  45 .  
         [0047]    The swivel assembly  50 , provides the physician with the opportunity to position the jaw assembly  90  in a variety of orientations relative to the handle  10 , to facilitate placing the  35  and  45  jaws against tissue to form desired lines of lesions, e.g., the heart wall in performance of the above-described Maze procedure. The physician can manually grasp and rotate the swivel assembly  50  and the jaw assembly  90  to provide a roll adjustment R, preferably through an arc of at least 300 degrees, relative to the axis of the distal end  15  of the handle  10  through interaction of components of the handle and swivel assembly described further below. In addition, the physician can grasp the jaw assembly  90  and adjust it in pitch P relative to the swivel assembly  50  through the interaction of components of the jaw assembly  90  and the swivel assembly  50  described further below. Preferably, the available arc of pitch P adjustment extends over at least 90 degrees. Moreover, the upper and lower jaws  35  and  45  are malleable as described further below. The combination of these features and the S-shape handle  10  make the hemostat highly versatile in use.  
         [0048]    The trigger  20  is employed to open (separate apart) and close (draw together) the jaws  35  and  45  and to compress tissue between the jaws  35  and  45  prior to application of RF energy to create an elongated lesion. A thumb slide  25  is provided in conjunction with an internal trigger lock, allowing the position of the trigger  20  and the jaws  35 ,  45  to be locked. After the trigger  20  is drawn toward the handle  10  to close the jaws  35  and  45 , the thumb slide  25  is moved distally relative to the handle  10  to cause an internal trigger lock to engage one of a series of ratcheting-lock points that define a set of locking locations for the jaws  35 ,  45 , as described further below. Movement of the thumb slide  25  proximally relative to the handle  10  releases the trigger  20  and the jaw assembly  90 , allowing the jaws  35 ,  45  to return to a fully open position. The interaction of the trigger  20 , thumb slide  25  and the associated trigger lock mechanism frees the physician from the need to maintain pressure on the trigger  20  to compress tissue between the jaws  35 ,  45  during the ablation, simplifying operation of the hemostat.  
         [0049]    Referring to FIG. 2, the upper jaw assembly  30  includes a pivotable, relatively rigid, upper jaw mount  300 , an elongated backbone  310 , an elongated insulated electrode sheath  320 , an elongated conductive electrode  330 , and an elongated electrode support  340 . Upper jaw mount  300  may be fabricated of plastic or other insulated material, and in preferred embodiments may be fabricated of Teflon filled polycarbonate plastic. Backbone  310  is preferably fabricated of malleable stainless steel or other malleable metal and is attached at a proximal end to upper jaw mount  300 . An insulated electrode sheath  320  is fitted over spine  310  with its proximal end located adjacent upper jaw mount  300 . The elongated conductive electrode  330  comprises a length of malleable conductive metal tubing as shown in FIGS. 5A and 5B is fitted into a lumen of the elongated electrode support  340 . The insulated electrode sheath  320  is formed with a channel that receives the sub-assembly of the elongated conductive electrode  330  and electrode support  340  disposed along the jaw  35 . Electrode sheath  320  may be fabricated of a flexible, electrically insulating, material, for example, silicone rubber. Elongated electrode support  340  is preferably fabricated of a porous material, such as Porex™ plastic, allowing for conductive fluid infiltration through its sidewall along its length and correspondingly delivery of conductive fluid along the length of jaw  35 . The jaw  35  can therefore be bent laterally with respect to the upper jaw mount  300  to form a curve along the length thereof.  
         [0050]    The lower jaw assembly  40  also includes a relatively rigid, lower jaw mount  400 , an elongated backbone  410 , an elongated insulated electrode sheath  420 , an elongated conductive electrode  430 , and an elongated electrode support  440  that are all formed of the same materials as the corresponding elements of the upper jaw assembly  30 . The assembly of the elongated backbone  410 , elongated insulated electrode sheath  420 , elongated conductive electrode  430 , and elongated electrode support  440  is also shown in FIG. 3B.  
         [0051]    The jaw  45  can therefore also be bent laterally with respect to the lower jaw mount  400  to form a curve along the length thereof. In use, the physician manually forms a lateral curve in both the upper and lower jaws  35  and  45  to fit the contour of the tissue, e.g., the heart wall.  
         [0052]    The lower jaw mount  400  is formed with a pair of spaced apart, parallel, plates or flanges  401  and  403  each bearing a series of notches  402  and  404 , respectively, along the edges thereof. When assembled, a proximal portion of the upper jaw mount  300  is fitted between the flanges  401  and  403 . A pin  480  extends through aligned holes through the proximal portion of upper jaw mount  300  and the flanges  401  and  403 . The ends of pin  480  are fixed to the flanges  401  and  403  allowing the proximal portion of the upper jaw mount  300  to be rotated about the pin  480 , thereby allowing jaws  35  and  45  to open and close. The upper and lower jaws  35  and  45  are separated apart a predetermined distance in the fully closed positions although the electrically insulated distal ends of the insulated electrode sheaths  320  and  420  may contact one another. A spring  450  urges the upper and lower jaws  35  and  45  apart from one another, facilitating opening of the jaws  35  and  45  upon release of the trigger  20  after application of RF energy.  
         [0053]    As shown in FIGS. 2 and 3A, the swivel assembly  50  includes a swivel  500  that may also be fabricated of Teflon filled polycarbonate plastic to have a tubular proximal swivel portion  506 , a pair of parallel plates or flanges  502  and  504  extending distally from swivel proximal portion  506  and a extending detent  501  extending laterally between flanges  502  and  504 . The jaw assembly  90  is mounted to the swivel assembly  50  by outwardly and laterally extending bosses  405  on the outer surfaces of flanges  401  and  403  that are fitted into bores  503  through swivel flanges  502  and  504 . The upper jaw mount  300  is mounted to the lower jaw mount  400  by pin  480  as described above, and the lower jaw mount is  400  pivotably mounted relative to the swivel  500 . Therefore, the upper and lower jaw assemblies  30  and  40  may be pivoted together relative to the swivel  500 , allowing for movement of the jaws  35  and  45  together through the range of pitch P adjustment. The selected pitch P adjustment is maintained by the engagement of the detent  501  into an opposed pair of notches  402  and  404 , stabilizing the upper and lower jaws  35  and  45  in a desired orientation relative to the swivel assembly  50 . In use, the physician adjusts the relative positions of the jaws  35  and  45  relative to the swivel assembly  50  by simply manually moving the jaw assemblies  30  and  40  in the pitch P direction around the pivot axis defined by bosses  405  within the corresponding bores  505  in swivel flanges  502  and  504 . The detent  501  simply rides over the ridges separating adjacent notches  402  and  404 .  
         [0054]    As noted above, the swivel assembly  50  and the upper and lower jaw assemblies  30  and  40  can be rotated around the axis of the distal end  15  of the handle  10  to a desired roll adjustment R to facilitate positioning the jaws  35  and  45  for creation of elongated lesions. The proximal portion  506  of swivel  500  is rotatably mounted within a collar  550  that is mounted fixedly to the distal end  15  of the handle  10  as shown in FIG. 3A. The collar  550  has a wavy or sinusoidal distally facing surface  551  of collar  550 . A washer-shaped insert  510  having a wavy or sinusoidal proximally facing surface  511  is fitted over the elongated proximal portion  506  of swivel  500  and attached to the swivel  500  through notches  514 , engaging corresponding bosses  557  and  567  (shown in FIG. 4) formed on swivel  500 . A C-clip  524  mounted in a circumferential groove formed in the proximal portion  506  of swivel  500  maintains the proximal portion  506  within the lumen of collar  550 . A spring washer  522  and a flat washer  520  are interposed between the C-clip  524  and the proximal end of collar  550 . Spring washer  522  urges the wavy or sinusoidal surfaces of collar  550  and insert  510  against one another, whereby a plurality of detent locations are defined that maintain a selected roll R adjustment relative to the distal end  15  of the handle  10 . In use, the physician adjusts the roll R of the jaw assembly  90  by simply turning the swivel assembly  50  relative to the handle  10 . The detent mechanism maintains the swivel assembly  50  in the selected desired roll R adjustment prior to and during closure of the jaws  35 ,  45  to compress tissue during application of RF energy.  
         [0055]    A cable  390  is also shown in FIGS. 3A and 4 that extends from the trigger  20  and that is employed to open and close the jaws  35  and  45 . Cable  390  passes through the internal lumen of proximal swivel portion  502 , through cable bore  565 , around shoulder  404  of lower jaw mount  400 , around boss  303  in upper jaw mount  300  and then upward into bore  408  in lower jaw mount  400 . The distal end of the cable  390  is maintained within bore  408  by ball  350 . When the cable  390  is pulled proximally by squeezing trigger  25 , boss  303  of upper jaw  300  is pulled toward bore  408  in lower jaw  400 , thereby pulling upper jaw  35  toward lower jaw  45 , allowing for compression of tissue there between. It should be noted that during this operation, the lower jaw mount  400  remains fixed relative to the swivel assembly  50  and only upper jaw mount  300  moves relative to the swivel assembly  50  or the handle  10 . Proximal movement of cable  380  does not affect the position of the lower jaw  45  relative to the handle  10 , nor does it affect the selected roll R adjustment of swivel  500 . Rotation of the jaw assembly  90  and swivel  500  about the roll axis does not affect the operation of the cable  390  because the cable  390  passes through the swivel  500  and enters the jaw assembly  90  along the roll axis. Pitch P adjustment of the jaw assembly  90  does not significantly effect operation of the cable  390  in opening or closing the jaws  35 ,  45  because shoulder  404  is at the center of rotation of lower jaw mount  400  relative to swivel  500  and remains essentially in the same location regardless of the pitch P adjustment.  
         [0056]    [0056]FIGS. 3A and 4 also internal electrical wiring and fluid delivery conduits of this embodiment of the invention including, insulated conductors  360  and  460  and fluid conduits  370  and  470  that both terminate at connections with the proximal ends of the upper and lower electrodes  330  and  430 , respectively. The fluid conduits  370  and  470  deliver conductive fluid into the lumens of the tubular upper and lower electrodes  330  and  430 , respectively. As shown in FIG. 4, the upper insulated conductor  360  and the upper fluid conduit  370  are routed to one side of the cable  390 , and the lower insulated conductor  460  and the lower fluid conduit  470  are routed to the other side of the cable  390  while passing through the lumen  534 .  
         [0057]    The elongated tubular electrodes  330  and  430  are illustrated in FIGS. 5A and 5B. The tubular electrodes  330  and  430  are preferably formed of thin-walled, malleable stainless steel tubing extending between a proximal open end  331 ,  431  and a distal closed end  333 ,  433 . A series of fluid ports  335 ,  435  are formed, e.g., by laser drilling, through the sidewall of the tubing from the lumen  339 ,  439  and extending in a single line, although the fluid ports could be formed in any selected array extending around the circumference of the sidewall of the tubing. The proximal ends  331 ,  431  are notched in alignment with the series of fluid ports  335 ,  435  to assist in assembly so that the fluid ports  335 ,  435  are directed in a particular alignment with the porous electrode support  340 ,  440 .  
         [0058]    The porous electrode support  340 ,  440 , depicted in FIGS. 6A and 6B, comprises a length of non-conductive, porous, malleable tubing having a channeled side  343 ,  443  adapted to fit within an elongated channel  323 ,  423  of the insulated electrode sheath  320 ,  420 , depicted in FIGS. 7A and 7B. The porous electrode support  340 ,  440  is conically shaped at the support distal end  347 ,  447  to fit within a conically shaped terminus  327 ,  427  of the elongated channel  323 ,  423  of the insulated electrode sheath  320 ,  420 . During assembly, the elongated tubular electrode  330 ,  430  is inserted into the elongated lumen  341 ,  441  of the porous electrode support  340 ,  440 . Preferably, the series of fluid ports  335 ,  435  are oriented toward the channeled side  343 ,  443  so that the conductive fluid emitted from the lumen through the series of fluid ports  335 ,  435  then migrates laterally through the pores of the porous electrode support  340 ,  440  and around its circumference to thoroughly and uniformly wet the porous electrode support  340 ,  440  along the upper and lower jaws  35  and  45 .  
         [0059]    The sub-assembly so formed is fitted into the shaped terminus  327 ,  427  and the elongated channel  323 ,  423  of the insulated electrode sheath  320 ,  420  as also shown in FIGS. 3A and 3B. Adhesive is applied to the contacting surfaces  323 ,  343  and  423 ,  443  to maintain the sub-assembly of the elongated tubular electrode  330 ,  430  inserted into the elongated lumen  341 ,  441  of the porous electrode support  340 ,  440  affixed to the insulated electrode sheath  320 ,  420 . The adhesive does not block migration of conductive fluid around the porous electrode support  340 ,  440 . Electrode sheathe  320 ,  420  is also formed having an elongated tapered internal recess  421   441  that receives the malleable backbone  310 ,  410  as shown in FIGS. 2 and 3. Again, adhesive may be applied to the contacting surfaces of the backbone  310 ,  410  and the elongated tapered internal recess  421   441 .  
         [0060]    The handle  10  is formed of a right handle half  600  depicted in FIGS.  8 A- 8 C and a left handle half  700  depicted in FIGS.  9 A- 9 C. Trigger sections  620  and  720  of the respective right and left handle halves  600  and  700  include downwardly opening recesses  621  and  721  in which trigger  20  is mounted (as shown in FIGS. 1 and 10) to pivot inward to apply tension on cable  390  or outward to release tension on cable  390 . Upward openings  627  and  727  in respective right and left handle halves  600  and  700  receive the thumb slide  25 . Inwardly extending projections  630  and  730  are also formed in respective right and left handle halves  600  and  700  that function to constrict the fluid conduits  370  and  470  to prevent conductive fluid flow therethrough when the trigger  20  is released as described further below.  
         [0061]    A set of circular matching, laterally opposed, sockets  623  and  723  are formed in the interior surfaces of the respective right and left handle halves  600  and  700 . The set of sockets  623 ,  723 , receive a pair of pivot bosses  206 ,  206 ′ of trigger  20  (shown in FIG. 13A) about which the trigger  20  pivots as described further below. A set of matching, laterally opposed, and slightly elongated or oblong, sockets  624  and  724  are formed in the interior surfaces of the respective right and left handle halves  600  and  700 . The set of sockets  624 ,  724  receive and guide a trigger lock  27  (shown in FIGS. 11A and 11B) that interacts with trigger  20  as described further below. The oblong shape of the set of sockets  624 ,  724  assists in allowing the trigger  20  to ratchet along the trigger lock  27  when trigger is drawn inward to tension the cable  390  during closing of the jaws  35 ,  45  as described further below.  
         [0062]    A further set of matching, laterally opposed, elongated sockets  625  and  725  are also formed in the interior surfaces of the respective right and left handle halves  600  and  700 . The set of sockets  625 ,  725  receive and guide a link arm  26  (shown in FIGS. 12A and 12B) that interacts with trigger  20  as described further below.  
         [0063]    As shown in FIGS. 8B and 9B, the distal portions of right and left handle halves  600  and  700  are formed with internal cylindrical recesses or sockets  612  and  712  that receive the laterally extending bosses  552  of collar  550  (FIG. 2). Internal grooves  611  and  711  are also formed within the distal portions of right and left handle halves  600  and  700  in which the c-clip  524 , flat washer  520  and spring washer  522  (FIGS. 2 and 3A) are fitted.  
         [0064]    As shown in FIGS. 8C and 9C, the right and left handle halves  600  and  700  are also provided with a series of laterally extending, perpendicular internal walls  628  and  728  that include slots and recesses for routing the fluid conduits or tubes  370  and  470 , the cable  390  and the insulated wire conductors  360  and  460  that extend through the length of handle  10 .  
         [0065]    The trigger  20 , thumb slide  25 , and the associated link arm  26  and trigger lock  27  are shown assembled to the right handle half  600  in FIG. 10 with the trigger  20  in the released position and the thumb slide  25  in the unlocked distal or retracted position. The trigger lock  27  is shown in greater detail in FIGS.  11 A- 11 B, the link arm  26  is shown in greater detail in FIGS.  12 A- 12 B, and the trigger  20  is shown in isolation in FIGS.  13 A- 13 B.  
         [0066]    Trigger  20  is provided with laterally extending cylindrical pivot bosses  206 ,  206 ′ that are mounted into sockets  723  and  623 , respectively. When released, trigger  20  extends outward through downwardly opening recesses  621  and  721 . When pulled, trigger  20  is pivoted inwardly into the handle recesses  621  and  721  about pivot bosses  206 ,  206 ′ to apply tension to the cable  390  that draws the upper and lower jaws  35  and  45  together. Cable  390  is mounted within a lubricious tube  391 , extending from the proximal wall  628  to the distal end  15  of the handle  10 , to allow the cable  390  to move freely within the handle  10  when trigger  20  is pulled or released.  
         [0067]    Trigger  20  is coupled to the proximal end of cable  390  through link arm  26 , illustrated in isolation in FIGS. 12A and 12B. Link arm  26  is provided at a distal end with two laterally extending bosses  262  and  262 ′ that are received in circular sockets  204  (one of which is shown in FIG. 13B) formed on the interior walls of the internal chamber  202  of trigger  20  to thereby pivotally mount the distal end of the link arm  26  to the trigger  20 . Link arm  26  is formed with a longitudinally extending slot  266 , allowing compression of the distal end of the link arm  26  to facilitate positioning of cylindrical bosses  262  and  262 ′ within the corresponding sockets  204  within the trigger  20 . As also shown in FIG. 13B, longitudinal slots  215  are provided in the interior  202  to assist insertion of the bosses  262 ,  262 ′ on link arm  26  into sockets  204  in trigger  20  during assembly. Link arm  26  is provided at its proximal end with two laterally extending, circular bosses  264  and  264 ′ that are received within the elongated slots  625  and  725 , respectively, in the respective right and left handle halves  600  and  700 . When trigger  20  is released, the circular bosses  264  and  264 ′ are disposed at the distal ends of the opposed elongated slots  625  and  725 , respectively. When trigger  20  is pulled inward, the proximal end of the link arm  26  is moved proximally within the opposed slots  625  and  725 , applying tension to cable  390 .  
         [0068]    Cable  390  is coupled to the link arm  26  by means of a swaged retainer  24 , mounted within a coil spring  28 . Coil spring  28  is fitted within a generally cylindrical chamber  266  formed extending at 90 degrees to the proximal end of link arm  26 . Cable  390  passes through an upwardly facing slot  270  in link arm  26  and through the interior of spring  28  to retainer  24 . Spring  28  is normally extended within chamber  266  but is compressed to provide protection against over tensioning of the cable  390 , if the upper and lower jaws  35  and  45  encounter significant resistance to further movement toward one another. The configuration of the trigger  20 , link arm  26  and slots  625  and  725  provide a mechanism whereby, the cable  390  is pulled proximally relatively quickly during initial upward movement of the trigger  20  to facilitate initial rapid closing of the jaws  35  and  45 . The cable  390  is pulled relatively more slowly during further upward movement of the trigger  20  to provide increased control to the physician during final compression of the jaws  35  and  45  against the tissue to be ablated.  
         [0069]    Trigger  20  is also provided with a distally extending projection  208  terminating with a laterally extending, generally cylindrical, boss  210  shown best in FIG. 13B. As illustrated in FIG. 10, when the trigger  20  is released and in its most downward position (corresponding to the point of maximum jaw opening), the fluid conduits or tubes  370  and  470  are disposed side by side and compressed between cylindrical boss  210  and the inwardly extending projections  630  and  730 . This compression of the fluid conduits or tubes  370  and  470  prevents flow of conductive fluid from the fluid source and out of the electrodes  330  and  430  and the electrode mounts  340  and  440  when the hemostat is not in use.  
         [0070]    The trigger  20  is also formed with a laterally extending slot  212  having an array of teeth  214  formed along one side of the slot  212 . A trigger lock mechanism is provided involving the interaction of the thumb slide  25  with the trigger  20  through a trigger lock  27  that is coupled at one end with the thumb slide  25  and selectively engages the teeth  214  to retain the upper and lower jaws  35  and  45  at a fixed position adjacent tissue to be ablated without requiring the physician to continually apply pressure to trigger  20 . Distal or forward movement of the thumb slide  25  causes the trigger lock  27  to engage the teeth  214 , and proximal or rearward movement of the thumb slide  25  releases the engagement. The trigger  20  can be operated freely by the physician to open or close the upper and lower jaws  35  and  45  when the thumb slide  25  is in the rearward position. With the thumb slide  25  in the forward position, the trigger  20  can be moved inward ratcheting over the teeth  214  to close the upper and lower jaws  35  and  45 , but the trigger  20  will not move outward upon release by the physician.  
         [0071]    The trigger lock  27  depicted in isolation in FIGS. 11A and 11B comprises an elongated link arm  275  having rods  272  and  278  laterally extending parallel to one another from opposed ends of the link arm  275 . As shown in FIG. 10, the rod  272  is inserted through the slot  202  so that the link arm  275  extends alongside the trigger  20  within the recess  721 . The rod  278  extends into a generally centrally located notch  252  of a resilient beam section  250  of the thumb slide  25 . Cylindrical pivot bosses  276  and  276 ′ extend laterally on either side of the link arm  275  in alignment with rod  272  and are inserted into sockets  724  and  624 , respectively.  
         [0072]    The rod  272  inserted through the slot  212  extending through the trigger  20  is formed with a laterally extending ramped tooth  274  that is selectively engagable with one of the ramped teeth  214  formed along the proximal edge of slot  212 , when the trigger lock  27  is pivoted forward from the position illustrated in FIG. 10 by distal or forward movement of the thumb slide  25  by the physician. Movement of the trigger  20  inwardly into the handle recess with the trigger lock  27  advanced forward from the position illustrated in FIG. 10 causes the interaction of the tooth  274  on the trigger lock  27  with the teeth  214  to retain the trigger  20  in position when pressure is released. The oblong configuration of sockets  624  and  724  that receive bosses  276 ′ and  276  of the trigger lock  27  allow the trigger lock  27  to move slightly forward during inward movement of the trigger  20  so that the tooth  276  on trigger lock  27  may ratchet along the ramped teeth  214  of trigger  20 . Interaction of the teeth  214  with the ramped tooth  274  on the trigger lock  27  prevents outward movement of the trigger  20  as long as the thumb slide  25  remains in the forward position in the slot formed by openings  627  and  727 .  
         [0073]    Release of the trigger  20  is accomplished by proximal or rearward movement of thumb slide  25 , pivoting the ramped tooth  274  out of engagement with a tooth of the teeth  214  along slot  212  which allows the upper and lower jaws  35  and  45  to open unless the physician holds the trigger  20  in position. The trigger  20  is urged outwardly out of the recess in handle  10  by spring  23  upon release of the trigger  20  and rearward movement of the thumb slide  25 . When the trigger  20  reaches its full outward position, flow of conductive fluid through fluid conduits  370  and  470  is terminated as the tubing is compressed between the laterally extending boss  210  and the inwardly extending projections  630  and  730 , as discussed above.  
         [0074]    The thumb slide  25  is provided with a resilient beam section  250 , having a generally centrally located notch  252  which engages the laterally extending rod  278  on trigger lock  27 , coupling the thumb slide  25  to the trigger lock  27 . The thumb slide  25  is preferentially retained at either the proximal, rearward or distal, forward point of its travel, without the necessity of the physician manually maintaining pressure on the thumb slide  25  due to the resilience of the beam  250  and the arcuate path of travel of the rod  278 .  
         [0075]    [0075]FIG. 14 illustrates a proximal portion of the assembled hemostat of FIG. 1 with the left handle half  700  removed to show the multi-conductor cable  80  and fluid conduit  70  extending through the strain relief  60  and their joinder to the wire conductors  360 ,  460  and the fluid conduits  370 ,  470 .  
         [0076]    The distal end of the fluid conduit  80  is coupled through a fitting  802  to proximal end of flexible tubing  804 . The distal end of flexible tubing  804  is coupled to the trunk of a Y-connector  806 , and the distal legs of the Y connector  806  are coupled to arms of a D-connector  810 . The D connector  810  is formed of a flexible plastic, e.g., silicone rubber, providing spaced apart fluid channels that are coupled to the proximal ends of the fluid conduits  370  and  470 .  
         [0077]    The fitting  804  supports a proximal flow controller or regulator  820  that has a precisely sized orifice that limits conductive fluid flow into the Y-connector  806 . The flow regulator  820  establishes a fixed flow rate and pressure within the Y-connector  806  regardless of the pressure of the fluid source that is available in the surgical theatre. The flow rate is established depending upon the upper and lower electrode area and design.  
         [0078]    The D connector  810  supports a pair of downstream flow regulators  822  and  824  that have equal, precisely sized orifices that further reduce the fluid flow rate and pressure of the conductive fluid entering the fluid conduits  370  and  470 . The downstream flow regulators  822  and  824  ensure that an even flow of conductive fluid is provided from within the Y connector  806  into the fluid conduits  370  and  470 . By this mechanism, the hemostat may be operated without the necessity of an associated pressurized fluid source and still provide controlled and even fluid flow to the upper and lower jaws  35  and  45  that contact the tissue to be ablated.  
         [0079]    An optional light emitter, e.g., an LED  830 , is depicted in FIG. 14 located within the strain relief  60  and coupled through an electrical junction  832  with the insulated wire conductors  360  and  460 . The wire conductors  360  and  460  can take the form of a twisted wire cable that extends distally from the electrical junction  832  through the length of the handle to the swivel assembly  50  where they are separated as shown in FIGS. 3A and 4. Separate wire conductors within a cable  834  extend from the electrical junction  832  to the LED  830 . In use, the LED  830  is illuminated in response to activation of an associated RF electrosurgical generator, and the LED illumination illuminates the strain relief  60 , which is preferably fabricated of a translucent flexible material, such as silicone rubber or the like. The physician will typically hold the handle  10  in orientations that make the strain relief  60  visible, and illumination of the LED  830  indicates to the physician that RF energy is being applied to the electrodes  
         [0080]    The proximal portion of the handle  10  may also optionally carry other electronic components including circuitry containing calibration information, for example calibrating a thermocouple if provided to sense electrode or tissue temperature. Circuitry containing identification information or providing re-use prevention may also be included, however such features are not believed to be essential to or a part of the present invention.  
         [0081]    [0081]FIGS. 15A and 15B illustrate an alternative embodiment of the electrode described above that can be employed in modified upper and lower jaw assemblies  30 A and  40 A corresponding generally to upper and lower jaw assemblies  30  and  40 . The upper and lower jaw assemblies  30 A,  40 A have a malleable backbone  310 ,  410  and a sheath  320 ,  420  as described above that are attached to the respective upper and lower jaw mounts  300  and  400  as shown in FIGS. 2 and 3. However, electrode  330 A,  430 A incorporates an exposed elongated electrode extension  350 A,  450 A extending to the outer surface of porous electrode support  340 A,  440 A and along the jaw  35 ,  45  that is intended to directly contact the tissue to be ablated. In this embodiment, conductive fluid is delivered as described above into the lumen of the internal tubular electrode  330 A,  430 A, which may be substantially the same as the tubular electrodes  330 ,  430 . An elongated electrode surface  352 A,  452 A of the electrode extension  350 A,  450 A and the contacted tissue are irrigated by conductive fluid emitted through the fluid ports of the internal tubular electrode  330 A,  430 A and conducted through the pores of the electrode support  340 A,  440 A.  
         [0082]    The electrode extension  350 A,  450 A is depicted prior to assembly with the electrode support  340 A,  440 A and the elongated tubular electrode  330 A,  430 A in FIGS. 16A and 16B. As formed, the electrode extension  350 A,  450 A includes an elongated straight portion  352 A,  452 A that is mounted against the exposed to the exterior of the electrode support  340 A,  440 A. A distally extending portion  360 A,  460 A is adapted to be inserted into the lumen of the electrode support  340 A,  440 A to extend alongside the elongated tubular electrode  330 A  430 A as shown in FIG. 15B.  
         [0083]    A series of barbed projections  354 A,  454 A extend laterally away from the elongated straight portion  352 A,  452 A. The electrode extension  350 A,  450 A is adapted to be bent back at junction  356 A,  456 A to enable insertion of the series of barbed projections  358 A,  458 A into the electrode support  340 A,  440 A. The proximal end  362 A,  462 A is electrically connected to the proximal ends of the tubular electrodes  330 A,  430 A and the distal ends of the wire conductors  360 ,  460 .  
         [0084]    This alternative exposed electrode embodiment can be formed by modifying the tubular electrode  330 ,  430  to have a conductive electrode band extending from the tubular electrode along the surface of the electrode support  340 ,  440 . Alternatively, this alternative electrode design can be accomplished without use of the tubular electrode  330 ,  430 , whereby conductive fluid is delivered to a lumen of the electrode support  340 ,  440  or to a fluid channel between the electrode support  340 ,  440  and the sheath  320 ,  420 , and the exposed electrode band is supported by the electrode support  340 ,  440 .  
         [0085]    The embodiments of the electrosurgical hemostat described above contain a number of valuable features and components, all of which contribute to provide a hemostat, which is convenient to use while providing substantial flexibility in use. However, many of the features of the hemostat could be employed in hemostats of other designs. For example, the trigger mechanism and/or the trigger lock mechanism of the above-described hemostat would certainly be of use in conjunction with cable activated hemostats having jaws of alternative designs to that described above. Similarly, the jaw assembly of the present hemostat might well be employed in conjunction with alternative trigger mechanisms. And/or in conjunction with alternative electrode designs, including electrodes which might not include provision for fluid irrigation and/or in the context of the hemostat having jaws that are rigid and not malleable by the physician to assume desired configurations. Further the specific electrode design employed in the hemostat design described above would be of significant use in conjunction with other hemostat types, including hemostats having jaws which are moved toward one another by alternative mechanisms. Similarly, a strain relief of the type described above including an LED indicator is believed to be of value in conjunction with any number of electrosurgical tools, particularly those in which the strain relief is within the physician&#39;s field of view, during normal operation of the hemostat. As such, the above description should be taken as exemplary, rather than limiting, with regard to the claims which follow.