Patent Publication Number: US-2005137575-A1

Title: Minimally invasive injection devices and methods

Description:
FIELD OF THE INVENTION  
      The present invention relates generally to the field of medical devices and methods. In especially preferred forms, the present invention relates to minimally invasive devices and methods to permit localized injections of a therapeutic agent.  
     BACKGROUND AND SUMMARY OF THE INVENTION  
      Cell transplantation to repopulate injured myocardium has shown to be an effective therapy for improving both systolic and diastolic ventricular function pre-clinically. Current cell delivery methods are either via an open surgical approach during coronary artery bypass or left ventricular assist device insertion or via a variation of endoventricular catheter delivery. Each of these conventional methods has benefits and limitations. For example, percutaneous catheter delivery of cells has the benefit of being minimally invasive but lacks direct visualization of the cell injection region. Open surgical delivery necessitates a sternotomy or thoracotomy but allows precise delivery of cells to the myocardium.  
      It would therefore be highly desirable if devices and/or methods could be provided which would allow the real time visual delivery of cells (or other therapeutic agents) to distinct organ locations in a minimally invasive manner. Such devices and/or methods could thereby obtain the benefits of precise therapeutic agent delivery under direct visualization. It is towards fulfilling such needs that the present invention is directed.  
      Broadly, the present invention is embodied in devices and methods whereby therapeutic agents may be injected into distinct organ locations in a minimally invasive manner. Most preferably the devices and methods of this invention employ a video-assisted thorascopic system (VATS) to enable a physician in real time to visually identify a distinct organ location into which therapeutic agent is to be injected.  
      In particularly preferred forms, the present invention is embodied in devices for injecting a therapeutic agent into a tissue site which include a proximal handle, and a tubular barrel distally extending from the handle. The barrel has an injection needle at a distal end thereof which is most preferably angled relative to the barrel&#39;s elongate axis. The internal space of the barrel is sized and configured to receive a cartridge containing a therapeutic agent to be injected into the tissue site. A plunger assembly and injection trigger assembly are provided so as to cause the plunger to expel a predetermined volume of the therapeutic agent from the cartridge to the needle and thereby allow injection thereof to the tissue site in response to operation of the trigger assembly.  
      A position dial may be provided so as to operably interconnect the barrel to the handle and to allow the barrel to be rotated about its longitudinal axis. Rotation of the position dial will therefore cause the barrel to rotate thereby allowing a selective change in the relative angular orientations of the injection needle.  
      In order to prevent inadvertent needle punctures while the device is being maneuvered, a needle guard is most preferably provided so as to sheath the needle. The needle guard is thus moveable between an advanced position wherein the injection needle is sheathed thereby, and a retracted position wherein the injection needle is exposed. Movements of the needle guard may be achieved by means of a pivotally moveable actuator lever attached to the patient external handle. An actuator rod operatively interconnects the actuator lever and the needle guard. As such, pivotal movements of actuator lever responsively moves the needle guard between its advanced and retracted positions.  
      These and other aspects and advantages will become more apparent after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof. 
    
    
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS  
      Reference will hereinafter be made to the accompanying drawings, wherein like reference numerals throughout the various FIGURES denote like structural elements, and wherein;  
       FIG. 1  is a side elevational view of an injection device in accordance with the present invention;  
       FIG. 2  is a view of the internal mechanisms associated with the device shown in  FIG. 1 ;  
       FIG. 3  is a greatly enlarged schematic view of a technique in accordance with the present invention for injecting a therapeutic agent into a discrete organ location. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      One particularly preferred form of an injection device  10  is depicted in accompanying  FIGS. 1 and 2 . Specifically, the device  10  includes a proximal handle body  12  which includes a depending pistol grip  12 - 1  sized and configured to be manually grasped and manipulated by an attending physician. An elongate rigid tubular barrel  14  extends distally from the handle  12  and terminates in a distally located angled injection needle  16 . The length of the barrel  14  is of course sufficient to allow placement of the distal injection needle  16  in the organ of interest. For example, when configured to inject cells into myocardium, the barrel length may be about 15 cm ± in length.  
      The handle  12  and barrel  14  are joined to one another via a rotatable dial  18 . More specifically, the rotatable dial  18  is coaxially fixed to the barrel  14  and is rotatable with respect to the handle  12 . Thus, the barrel  14  and dial  18  may be rotated about the barrel&#39;s elongate axis (arrow A r ) as a unit so as to allow the physician to change the orientation of the angled injection needle  16  as may be desired to facilitate its placement and injection of the therapeutic agent. Most preferably, the dial  18  may be provided with position markings to assist the physician in determining the relative positioning of the distal needle  16 .  
      A cartridge loading chamber  20  is provided in proximal axial section of the barrel  14 . The loading chamber  20  thus allows a cartridge or vial  22  containing the therapeutic agent (e.g., cells) to be loaded into the hollow of the barrel  14  proximally of the needle  16 . When positioned within the barrel  14 , the discharge port  22 - 1  of the cartridge  22  will therefore be in communication with the injection needle  16  to allow the contents of the cartridge  22  to be transferred to and through the needle  16 . A cover  24  attached to knob  26  allows the loading chamber  20  to be reciprocally slideably moved (arrow A c ) between an opened condition (as shown in solid line in  FIG. 1 ) and a closed condition (as shown in dashed line in  FIG. 1 ). While in the opened condition, therefore, the cartridge  22  may be positioned within the loading chamber, such that upon movement of the handle  26  the cover  24  will close the chamber  20  thereby retaining the cartridge  22  therein.  
      A tubular needle guard  28  is sleeved over a distal section of the barrel  14 . As is perhaps better shown in  FIG. 2 , the needle guard  28  is connected to an actuator lever  30  pivotally connected to the handle  12  by means of proximal and distal actuator rods  32 ,  34  and a pivotal linkage  36 . A tension spring  38  is connected operatively to the linkage  36  so as to bias its pivotal movement in a direction tending to cause the guard  28  to be in its normal advanced position with respect to needle  16 .  
      As shown in solid line in  FIG. 1 , the needle guard  28  is normally in an advanced position whereby the needle  16  is covered. However, manually squeezing the lever  30  will cause it to be moved pivotally in the direction of arrow A l  (see  FIGS. 1 and 2 ) toward the grip  12 - 1 . Such movement of the actuator  30  will responsively slideably move the guard  28  in a proximal direction (arrow A g  in  FIGS. 1 and 2 ) by virtue of the responsive retraction of the actuator rods  32 ,  34  and clockwise pivoting (as viewed in  FIG. 2 ) of the linkage  36  thereby exposing the needle  16 . In such a manner, the physician may selectively cover the needle  16  with the guard  28  so as to maneuver the needle  16  from one organ injection site to another safely and yet expose the needle once a new injection site has been located. The tension spring  38  ensure that, once manual squeezing pressure is released from the lever  30 , the lever  30  and hence the needle guard  28  will return to their respective normal conditions as shown in solid line in  FIGS. 1 and 2 .  
      A plunger  40  is provided at the distal-most end of a plunger control rod  42  mounted within the handle  12  for reciprocal rectilinear movements. The proximal-most end of the control rod  42  carries a knob  44 . The control rod  42  also includes a longitudinal section of ratchet teeth  46  engageable with ratchet pawl  48 . The knob  44  allows the control rod  42 , and hence the distal plunger  40  thereof, to be pulled manually into a retracted position as shown in solid line in  FIG. 1 , for example, by twisting the control rod  42  one quarter-turn so as to disengage the ratchet teeth and pawl  46 ,  48 , respectively, and then pulling rearwardly. Once in the retracted position, the quarter-turn may be reversed to thereby again re-engage the ratchet teeth and pawl  46 ,  48 , respectively.  
      Controlled advancement of the control rod  42 , and hence the distal plunger  40  thereof, is achieved by operation of the engaged ratchet teeth  46  and pawl  48  by means of the injection trigger  50 . As can be seen more clearly in  FIG. 2 , the pawl  48  and trigger  50  are each pivotally attached to the handle  12  at one location, and are pivotally interconnected to one another at another location via pivot linkage  52 . A tension spring  54  is connected operatively to the injection trigger  50  so as to bias it into its inactive position (shown in solid line in  FIG. 2 ). Pulling on the trigger  50  against the bias force of the spring  54  will therefore cause the pawl  48  to be pivotally moved via linkage  52  out of engagement with one of the ratchet teeth  46 . Releasing the trigger  50  will allow the bias force of the spring  54  to return the trigger to its inactive position which in turn responsively causes the pawl  48  to pivot back into engagement with a distally successive one of the ratchet teeth  46  and thereby forwardly advance the control rod an incremental longitudinal distance. As a result, the plunger will cause a corresponding incremental volume of therapeutic agent to be forcible expelled through the needle  16 .  
      The forward distance which the plunger advanced each time the trigger  50  is depressed and released is determined by the geometries of the teeth  46  and pawl  48 , as well as the dimensional “throw” of the pawl  48  (e.g., the number of adjacent teeth that are by-passed by the pawl when it disengages from a tooth and then re-engages with another one of the teeth proximally thereto). Most preferably, the pawl  48  is pivotally connected to a longitudinally slideable control member  58  which, in turn, is connected operatively to volume control dial  60 . Thus, turning movement applied to the control dial  60  will translate into longitudinal movements distally or proximally (i.e., in dependence upon the direction of turning movement applied to the dial  60 ) of the control member  58 . This longitudinal movement of control member  58  will thereby either increase or decrease the effective “throw” of the pawl  48  each time the trigger  50  is operated. Thus, by turning the control dial  60 , the pawl  48  may be caused to engage either the immediately next successive one of the teeth  46 , or every second, third, fourth etc. one of the teeth  46  each time the trigger  50  is operated. In such a manner, therefore, an attending physician may preselect the volume of therapeutic agent which is expelled from the needle  16  for each operable cycle of the trigger  50 .  
      In use, the distal end of the barrel is inserted through a minimally invasive surgical incision near the organ to be injected. Thus, when injecting cells into myocardium, minimally invasive cardiac procedures may be employed which are well known to those in this art. The attending physician guides the distal end of the barrel  14  with the needle  16  sheathed by guard  28  under thorascopic visual observation using a patient external monitor and patient internal video probe (not shown) associated with a video-assisted thorascopic system (VATS). Once the site for injection has been determined the needle  16  may be unsheathed by retraction of the guard  28  and the relative angular orientation of the needle  16  changed as may be desired or necessary by manipulation of the dial  18 . As shown in  FIG. 3 , the needle  16  may then be advanced into the myocardium M between the epicardium EPC and endocardium EDC tissue layers. The physician will select the volume amount of transplanted cells to be injected by manipulation of the volume control dial  60  and then operate the trigger  50  thereby causing such desired amount of transplanted cells TC to be injected into the myocardium M. The myocardium M may be stabilized physically by placement of an endo babcock EB adjacent the injection site.  
      While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.