Patent Publication Number: US-7713190-B2

Title: Flexible instrument

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 10/012,586, filed Nov. 16, 2001, now U.S. Pat. No. 7,371,210 which is a continuation-in-part of U.S. application Ser. No. 09/827,503, filed Apr. 6, 2001 (now U.S. Pat. No. 6,432,112), which is a continuation U.S. application Ser. No. 09/746,853, filed Dec. 21, 2000 (now U.S. Pat. No. 6,692,485), which is a divisional of U.S. application Ser. No. 09/375,666 (now U.S. Pat. No. 6,197,017), filed Aug. 17, 1999, which is a continuation of U.S. application Ser. No. 09/028,550, filed Feb. 24, 1998 (now abandoned). This application is also a continuation-in-part of U.S. application Ser. No. 09/783,637, filed Feb. 14, 2001 (now abandoned), which is a continuation of PCT/US00/12553, filed May 9, 2000, which claims the benefit of priority of U.S. Application Ser. No. 60/133,407, filed May 10, 1999. This application is also a continuation-in-part of PCT/US01/11376, filed Apr. 6, 2001, which claims priority the benefit of priority of U.S. application Ser. No. 09/746,853, filed Dec. 21, 2000 (now U.S. Pat. No. 6,692,485), and Ser. No. 09/827,503, filed Apr. 6, 2001 (now U.S. Pat. No. 6,432,112). This application is also a continuation-in-part of U.S. application Ser. No. 09/746,853, filed Dec. 21, 2000 (now U.S. Pat. No. 6,692,485), and Ser. No. 09/827,503, filed Apr. 6, 2001 (now U.S. Pat. No. 6,432,112). This application is also a continuation-in-part of U.S. application Ser. No. 09/827,643, filed Apr. 6, 2001 (now U.S. Pat. No. 6,554,844), which claims the benefit of priority to U.S. application Ser. No. 60/257,869, filed Dec. 21, 2000, and Ser. No. 60/195,264, filed Apr. 7, 2000, and is also a continuation-in-part of PCT/US00/12553, filed May 9, 2000, from which U.S. application Ser. No. 09/783,637, filed Feb. 14, 2001, claims priority. 
     This application also claims the benefit of priority of U.S. application Ser. No. 60/293,346, filed May 24, 2001, Ser. No. 60/279,087, filed Mar. 27, 2001, Ser. No. 60/313,496, filed Aug. 21, 2001, Ser. No. 60/313,497, filed Aug. 21, 2001, Ser. No. 60/313,495, filed Aug. 21, 2001, Ser. No. 60/269,203, filed Feb. 15, 2001, Ser. No. 60/269,200, filed Feb. 15, 2001, Ser. No. 60/276,151, filed Mar. 15, 2001, Ser. No. 60/276,217, filed Mar. 15, 2001, Ser. No. 60/276,086, filed Mar. 15, 2001, Ser. No. 60/276,152, filed Mar. 15, 2001, Ser. No. 60/257,816, filed Dec. 21, 2000, Ser. No. 60/257,868, filed Dec. 21, 2000, Ser. No. 60/257,867, Dec. 21, 2000, Ser. No. 60/257,869, Dec. 21, 2000. 
     This application is also related to application Ser. Nos. 11/762,768, 11/762,770, 11/762,772, 11/762,773, and 11/762,774, all of which are filed on Jun. 13, 2007. 
     The disclosures of the foregoing applications are expressly incorporated herein by reference. This application further expressly incorporates herein by reference, U.S. application Ser. No. 10/014,145 (now U.S. Pat. No. 6,775,582), Ser. No. 10/012,845 (now U.S. Pat. No. 7,169,141), Ser. No. 10/008,964 (now abandoned), Ser. No. 10/013/046 (now abandoned), Ser. No. 10/011,450 (now abandoned), Ser. No. 10/008,457 (now U. Pat. No. 6,949,106), Ser. No. 10/008,871 (now U.S. Pat. No. 6,843,793), Ser. No. 10/023,024 (now abandoned), Ser. No. 10/011,371 (now U.S. Pat. No. 7,090,683), Ser. No. 10/011,449 (now abandoned), Ser. No. 10/010,150 (now U.S. Pat. No. 7,214,230), Ser. No. 10/022,038 (now abandoned), Ser. No. 10/012,586, all filed on Nov. 16, 2001. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates in general to a remote controlled flexible instrument comprising a flexible shaft, for introduction into a body cavity or body vessel to perform a medical procedure. 
     BACKGROUND OF THE INVENTION 
     Catheters are used extensively in the medical field in various types of procedures, including invasive procedures. Minimally invasive surgery involves operating through small incisions, through which instruments are inserted. These incisions are typically 5 mm to 10 mm in length. Minimally invasive surgery is typically less traumatic than conventional surgery, due, in part, to the significant reduction in incision size. Furthermore, hospitalization is reduced and recovery periods shortened as compared with conventional surgery techniques. Catheters may be tailored to a particular size or form, depending on the incision and the size of the body cavity or lumen. 
     Due to the small size of the incision, the bulk of the surgery is not visible. Although the surgeon can have visual feedback from the surgical site via a video camera or endoscope inserted into the patient, or via radiological imaging or ultrasonic scanning, the ability to control the relatively simple laparoscopic instruments remains difficult. Even with good visual feedback, the surgeon&#39;s tactile and positional senses are physically removed from the operative site, rendering endoscopic procedures slow and clumsy. 
     Current instrumentation, with forceps, scissors, etc., inserted into the body at the end of long slender push rods is not fully satisfactory. The use of such conventional instrumentation increases operative time, and potentially heightens risk. For example, tissue may be injured when the laparoscopic tool moves outside the visual field. Moreover, there are limitations on the type and complexity of procedures that may be performed laparoscopically due, in part, to the limitations on the instruments that are used. 
     Development work has been undertaken to investigate the use of robotic work in surgery. Typically, these robotic systems use arms that reach over the surgical table and manipulate surgical instruments. The known robotic systems are large, clumsy to operate and relatively expensive to manufacture. The presence of a robot at the surgical site is problematic particularly when the robot is large and may impede access to the patient during surgery. 
     SUMMARY OF THE INVENTION 
     In accordance with a first aspect of the present inventions, a method of performing a medical procedure on a patient is provided. The method comprises conveying control signals from a remote controller to a drive unit, and operating the drive unit in accordance with the control signals to intravenously introduce the catheter into a heart of the patient. The catheter may be intravenously introduced into the heart in any one of a variety of manners, but in one method, the catheter is introduced within the vena cava into the right atrium of the heart. The method further comprises using the catheter to create a puncture within a wall between two chambers (e.g., the left and right atria) of the heart. 
     In one method, the drive unit is operated in accordance with the control signals to create the puncture within the heart wall. In another method, the drive unit is operated in accordance with the control signals received from the remote controller to advance the catheter from one of the two chambers to another of the two chambers through the puncture. In still another method, the catheter has an expandable device, in which case, the expandable device can be actuated to anchor the catheter against the wall. In still another method, the catheter is a guide catheter, in which case, the drive unit may be operated in accordance with the control signals received from the remote controller to advance a working catheter within the guide catheter through the puncture. If the working catheter has an end effector, the drive unit may be operated in accordance with the control signals received from the remote controller to actuate the end effector within the heart; for example to repair a valve within the heart. 
     In accordance with a second aspect of the present inventions, another method of performing a medical procedure on a patient is provided. The method comprises conveying control signals from a remote controller to a drive unit, intravenously introducing the catheter into a heart of the patient (e.g., via the vena cava into the right atrium), and creating a puncture within a wall between two chambers (e.g., the left and right atria) of the heart. The method further comprises creating a puncture within a wall between two chambers of the heart, and operating the drive unit in accordance with the control signals to advance a working catheter within the guide catheter through the puncture. The working catheter and guide catheter can be operated in the same manner described above to perform a medical procedure (e.g., heart valve repair). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Numerous other objects, features and advantageous of the invention should now become apparent upon a reading of the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a simplified block diagram illustrating basic components of a system constructed in accordance with the present invention; 
         FIG. 2  illustrates further details of input devices at the master unit; 
         FIG. 3  is a schematic diagram illustrating one embodiment of the present invention in which the flexible instrument system includes multiple separate nested catheters; 
         FIGS. 3A-3C  illustrate different forms of catheter control in according with aspects of the present invention; 
         FIG. 4  is an illustrative diagram showing the use of the catheter of the present invention in connection with mitral valve repair; 
         FIG. 5  is schematic diagram of the catheter system of the present invention as deployed through the urethra for a surgical procedure in the bladder; 
         FIG. 6  is a perspective view of one embodiment of a system embodying the catheter apparatus of the present invention; 
         FIG. 7  is a more detailed perspective view of the catheter apparatus; 
         FIG. 8  is an enlarged view of a portion of the catheter apparatus particularly at the distal end section thereof; 
         FIG. 9  is a cross-sectional view through the catheter apparatus as taken along line  9 - 9  of  FIG. 7 ; 
         FIG. 10  is a cross-sectional view through the catheter apparatus as the distal end section thereof, as taken along line  10 - 10  of  FIG. 7 ; 
         FIG. 11  is a cross-sectional view similar to that illustrated in  FIG. 9  for an alternate embodiment of the invention depicting dual-direction flexing; 
         FIG. 12  is one design of tool construction in accordance with the present invention employing inner and outer catheters and inner and outer cables; 
         FIG. 13  is a schematic diagram of the tool or mini-tool showing certain parameters relating to position control; 
         FIG. 14  is a block diagram of the controller used with the telerobotic system of this invention; 
         FIG. 15  is a block diagram of further details of the controller particularly details of the module board; 
         FIG. 16  is a block diagram of the control algorithm in accordance with the present invention; 
         FIG. 17  is a schematic diagram illustrating one mechanism for providing mitral valve repair employing a ring mechanism; 
         FIG. 18  illustrates schematically the concept of the present invention in connection with mitral valve repair; 
         FIG. 19  is a diagram of a heart muscle illustrating the position of the mitral valve; 
         FIG. 20  illustrates further detail of the mitral valve construction as well as the catheter and tool used in the procedure; 
         FIG. 21  is a more detailed cross-sectional drawing of the portion of the mechanical member, particularly the means for tightening the retaining means; 
         FIG. 22  shows further details of the structure of  FIG. 21 ; 
         FIG. 23  is a schematic illustration of a section of the mitral valve ring showing the fiber and the securing of one end of the fiber; 
         FIG. 24  illustrates somewhat further detail of a means for retaining the catheter in position; 
         FIG. 25  is a diagram illustrating alternate means for holding the catheter in place; 
         FIG. 26  illustrates a view of a mitral valve; 
         FIG. 27  is a schematic diagram of the mitral valve indicating the ring area and leaflets; 
         FIG. 28  is a schematic illustration showing the mitral valve construction and a mechanical member for retaining and tightening; 
         FIG. 29  is schematic diagram of another technique for mitral valve repair employing a wire to be tightened like a lasso; 
         FIG. 30  is a schematic diagram illustrating a catheter and tool construction containing a tether cable and anchor elements within the inner catheter; 
         FIG. 30A  shows a cable termination tool for crimping; 
         FIG. 30B  shows a tool for cutting; 
         FIG. 31  illustrates a staple array of the present invention; 
         FIG. 32  illustrates the mitral valve construction as well as the staple apparatus and technique of the present invention; 
         FIG. 33  is an illustration of the staple array when applied and secured to the valve annulus; 
         FIG. 34  is a schematic illustration of an alternate embodiment for the staple array; 
         FIGS. 35A and 35B  illustrate another version of the invention wherein the guide catheter is robotic; 
         FIG. 36  schematically represents a system of the present invention for repairing a mitral valve; 
         FIG. 36A  shows a pin for anchoring; 
         FIG. 37  illustrates the anchoring system engaged with the mitral valve; 
         FIG. 38  illustrates another version in accordance with the invention employing a balloon with the balloon in a deflated state; 
         FIG. 39  schematically represents portions of the heart muscle and the positioning of the balloon relative to the mitral valve; 
         FIG. 40  illustrates the balloon in its inflated state positioned at the mitral valve; 
         FIGS. 41A-41D  depict still another form of catheter in accordance with the present invention; 
         FIG. 42  is a perspective view of another embodiment of the present invention; 
         FIG. 42A  is an enlarged detail perspective view of the tool; 
         FIG. 43  is an exploded perspective view of, in particular, the interlocking modules of the flexible instrument system of  FIG. 42 ; 
         FIG. 44  is a partially broken away rear elevational view of the interlocking modules as seen along line  44 - 44  of  FIG. 42 ; 
         FIG. 45  is a cross-sectional side view through the interconnecting modules and as taken along line  45 - 45  of  FIG. 42 ; 
         FIG. 46  is a cross-sectional plan view through the instrument module taken along line  46 - 46  of  FIG. 45 ; 
         FIG. 47  is a cross-sectional plan view taken through the base module of the system of  FIG. 42 , and as taken along line  47 - 47  of  FIG. 45 ; 
         FIG. 48  is a cross-sectional end view taken along line  48 - 48  of  FIG. 47 ; 
         FIG. 48A  is a cross-sectional view taken along line  48 A- 48 A of  FIG. 48 ; 
         FIG. 48B  is a fragmentary plan view of a drive wheel engagement slot by itself as taken along line  48 B- 48 B of  FIG. 48A ; and 
         FIG. 49  is a schematic perspective view showing mechanical cabling between the drive unit and the flexible instrument system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides a system for remotely controlling a flexible instrument for use in medical applications, typically for operative or other medical procedures. The flexible instrument comprises a shaft or a tube of sufficient dimensions for passing through a small incision or natural body lumen or cavity and ultimately, for positioning a distal end of the shaft within the body at an internal target (operative) site. The flexible instrument can also support a tool at its distal end to allow more intricate medical procedures. A user or surgeon can control the position of the shaft from a master station, allowing operation from another part of the operating room, or even from another room or another building. In one aspect of the invention, the shaft can comprise one or more flexible segments, which a user can controllably bend, providing finer control in directing the shaft toward the target site. The control can result in, for example, a deflection or turning of the shaft, for guiding this shaft through or within various body cavities or lumens. The controllable bending is also useful for more precise positioning of a distal end of the flexible instrument at a desired operative site. 
     Preferably, the flexible instrument is used to perform minimally invasive procedures. “Minimally invasive procedure,” refers herein to a surgical procedure in which a surgeon operates through small cut or incision, the small incision being sufficiently necessary to access the operative site. In one embodiment, the incision length ranges from 1 mm to 20 mm in diameter, preferably from 5 mm to 10 mm in diameter. This procedure contrasts those procedures requiring a large cut to access the operative site. Thus, the flexible instrument is preferably used for insertion through such small incisions and/or through a natural body lumen or cavity, if necessary, so as to locate the catheter at an internal target site for a particular surgical or medical procedure. Examples of such minimally invasive procedures include intravascular procedures, such as the repair of a cardiac valve. The introduction of the flexible instrument into the anatomy may be by percutaneous or surgical access to a lumen or vessel, or by introduction through a natural orifice in the anatomy. 
       FIG. 1  is a block diagram schematically illustrating the three main components of the remote control system of the present invention. A surgeon or user can input control actuations at master station  1 , typically through an input device (not shown). Slave station  3  is separate and remote from the master station and controls the motion of the flexible instrument, in accordance with the user input from master station  1 . Master station  1  and slave station  3  may be in relatively close proximity to each other, such as in the same operating room, or can be displaced from each other by miles. Controller  2  provides a telecommunications or electronic communications link coupled between the master station and the slave station. Controller  2  typically includes a computer. Controller  2  receives a command from the input device of master station  1  and relays this command to slave station  3 . 
       FIG. 6  is a schematic of the remote control system of the present invention. The system includes: (1) A master station comprising a user interface or surgeon&#39;s interface  11 ; (2) A slave station comprising a flexible instrument including shaft  30  which supports tool  18 . Shaft  30  is connected to and is controllable from mechanically drivable mechanism  26 , which in turn is engageably received by receiver  24 , both of which are mechanically driven by drive unit  13 , (alternatively mechanical drive  13 ); and (3) a controller or computation system  12  to translate a user&#39;s commands from user interface  11  to drive unit  13 , which then drives the articulations of shaft  30  and tool  18 .  FIG. 6  illustrates a system where a user or surgeon can control shaft  30  and tool  18  by manipulating interface handles  30 A of user interface  11 . The movement of handle  30 A causes responsive movement of tool  18  through the coordinating action of computation system  12 . For example, tool  18  can be a pair of graspers, scissors, staplers, etc. and manipulation of handle  30 A can cause the jaws of tool  18  to open and close. 
     Surgeon&#39;s interface  11  is in electrical communication with computing system  12 , which is, in turn, in electrical communication with drive unit  13 . In one embodiment, drive unit  13  comprises a plurality of motors. The drive unit  13  is in mechanical communication with shaft  30  via conduit  23 , which houses a plurality of mechanical cables driven by the plurality of motors in drive unit  13 . In one embodiment, drive unit  13  is solely in mechanical communication with shaft  30 . Because of the mechanical communication with shaft  30 , the electromechanical components in drive unit  13  are disposed in an area remote from the operative site, and preferably in an area outside the sterile field. Preferably, objects that are difficult to sterilize, e.g. motors or electromechanical components, are kept at a sufficient distance from the patient to avoid contamination. This distance is readily ascertainable by doctors, nurses, and other appropriate medical professionals. In one embodiment, the sterile field has the rest surface of the operating table as its lower boundary. Thus, drive unit  13  is preferably located below the plane of the sterile field, i.e. below the rest surface of the operating table. The patient or subject may be further protected from drive unit  13  with a sterile barrier, such as a sterile cloth. With respect to the drive unit, such as drive unit  13  in  FIG. 6 , reference is made to co-pending provisional application No. 60/279,087, which is incorporated by reference herein. In accordance with the system of  FIG. 6 , all of the drive motors in drive unit  13  are disposed away from the sterile field and thus the need for a sterile barrier is eliminated. Furthermore, since all of the motors and electronics are within a single, self-contained unit, design, testing and manufacturing of the system is greatly simplified. 
     Accordingly, one aspect of the present invention provides a drive unit capable of remotely driving articulation of a flexible instrument, where the drive unit is remote from the subject and the flexible instrument. The slave station of the present invention employs, to a large part, a mechanical arrangement that is effected remotely and includes mechanical cables and flexible conduits coupling to a remote motor drive unit. This provides the advantage that the instrument is purely mechanical and does not need to be contained within a sterile barrier. The instrument may be autoclaved, gas sterilized or disposed in total or in part. 
     In  FIG. 6 , drive unit  13  mechanically drives the flexible instrument (comprising shaft  30  and tool  18 ) through conduit  23 , receiver  24  and mechanically drivable mechanism  26  (alternatively known as mechanically drivable interface or shaft mount). Conduit  23  houses a plurality of separate mechanical cables to mechanically connect drive unit  13  with receiver  24 . The mechanical cables physically contact and drive the motions of shaft  30  and tool  18 . Conduit  23  is engageable and disengageable with drive unit  13 , i.e. attachable and detachable (see discussion of  FIG. 49 , below). Although two conduits  23  are depicted here, it is understood that more or fewer conduits may be used, depending on the particular application. In one embodiment, drive unit  13  comprises a plurality of motors, which drive the mechanical cables extending through conduit  23  and terminating at receiver  24 . Receiver  24  interlockably receives mechanically drivable interface  26 , which engages a separate set of cables extending through shaft  30  and at least one cable line operating tool  18 . Thus, engaging drivable interface  26  with receiver  24  provides a mechanical (physical) connection from drive unit  13  to control certain motions of shaft  30  and tool  18 . Receiver  24 , which is supported by a carriage, is capable of moving along a linear path represented by the arrow  22  via rails  25 . 
     Cables in conduit  23  also mechanically drives the translation of receiver  24  along rails  25 . The rails, and thus the linear translation extend at an acute angle with respect to the operating table, as well as the subject. This angular arrangement disposes the flexible instrument system in a convenient position over the patient. This arrangement also minimizes the number of components that operate within the sterile field, as drive unit  13  is maintained at a location remote from the sterile field. 
       FIG. 49  shows a schematic perspective view of the cabling pathway for mechanically coupling one of an array of motors of a drive unit with a tool supported on a distal end of a shaft. In general, the cabling pathway comprising a plurality of mechanical cables extends from the drive unit to the receiver. Another separate set of mechanical cables connects the mechanically drivable mechanism, situated at a proximal end of the shaft, to the tool and any controlled flexible segments positioned along the shaft. Interlocking the receiver with the mechanically drivable mechanism results in connecting the two separate sets of mechanical cables, thereby extending the cabling pathway from the drive unit to the distal end of the shaft. Thus, each of the mechanically drivable mechanism and the receiver can be considered as a coupler, which interlocks or couples with each other. 
     More specifically,  FIG. 49  shows drive motor  675  positioned within a drive unit, such as drive unit  13  of  FIG. 6 . The first cabling pathway comprises a set of cabling, which engages with and extends from drive motor  675  through idler pulley  682 . The cables continue through idler pulleys  630  and  632  to drive wheel  622 , which resides in receiver  506  (equivalent to receiver  24  of  FIG. 6 ). A second separate set of cables extends about the drive wheel  624 , guided by cam  626  and continues through flexible instrument shaft  528 . Tool  534  links to shaft  528  via joint  601 , which provides a wrist pivot about axis  532  in the direction of arrows J 4 . The two separate sets of cables are interlocked by interlocking drive wheel  622  of receiver  506  with drive wheel  624  of mechanically drivable mechanism  526  (equivalent to drivable mechanism  26  of  FIG. 6 ). Specifically, the interlocking involves slotting a blade  606  into a corresponding slot within wheel  624  (see further discussion of  FIG. 43  below). 
     In one embodiment, the interlocking mechanism can comprise a magnetic attachment, where a first series of magnets in the mechanically drivable mechanism interacts with a second series of magnets in the receiver. Each series of magnets can couple with the mechanical cables. 
       FIG. 49  also shows the output of motor  675  at a coupler pulley  677 , which is adapted to rotate with an output shaft of the motor. The rotational arrow  680  indicates this rotation. 
     For the sake of simplicity,  FIG. 49  only illustrates one cabling pathway. It can be appreciated that several other cabling pathways can be constructed and arranged to control other motions of the shaft and tool through other motors of the drive unit. 
     Regarding the interface  11 , computer system  12  and drive unit  13 , reference is also made to co-pending application PCT Serial No. PCT/US00/12553 filed May 9, 2000, and U.S. Provisional Application Ser. No. 60/279,087 filed Mar. 27, 2001, both of which are incorporated by reference herein in their entirety. 
     A more detailed discussion of the master station, the slave station and computation system or controller  12  is provided below. 
     Master Station 
       FIG. 2  schematically depicts the components of master station  1 . Master station  1  can include any one or a combination of input devices A-E and a display F. Input device A is a point-and-touch device. Input device B is a computer mouse. Input device C is a pointing device that may employ a pen or stylus. Input device D is a joystick. Input device E is a hand interface, that provides finer control of the shaft, or a tool positioned at the distal end of the shaft. 
     In one embodiment, input device E features handles that control the motion of the shaft and a tool. Referring back to  FIG. 6 , the master station features input device  11  comprising handles  30 A. Handles  30 A are held by the surgeon, who can then torque, translate or rotate catheter member  30  and tool  18  by performing the corresponding motions on handles  30 A. A rotation of a handle  30 A via rotation of the surgeon&#39;s hand can control rotation of, for example, the outer shaft  32  about the co-axis. Flexing or bending of flexible section  42  can be controlled by the surgeon flexing his hand at the wrist and activating flex cable  52 , as shown in  FIG. 8  (see discussion of  FIG. 8 , below). A surgeon can manipulate tool  18  by, for example, closing and opening the jaws of handles  30 A to simulate opening and closing of jaws of tool  18 . 
     Reference may also be made to application serial number application Ser. No. 10/008,457, filed Nov.  16 ,  2001 , now U.S. Pat. No. 6,949,106, which discloses other details of a master station input device (master positioner) that may be used in carrying out the control described herein. 
     Display F provides a direct video image of the site surrounding the distal end of the shaft. An endoscope supporting a camera is inserted into the body of a subject, providing the video feed of the operative site. The camera can be mounted on or housed at the distal end of the shaft. The camera can provide a view of the operative site, or may be positioned away from the site to provide additional perspective on the surgical operation. 
     Other detection systems may be used for providing different images useful in assisting the surgeon in performing the medical procedure. Thus, various signals may be utilized in conjunction with or in alternative to the video image, such as ultrasound (echocardiography, Doppler ultrasound), angiography, electrophysiology, radiology or magnet resonance imaging (MRI). Also, an audio signal could be used for guiding the shaft. These detection techniques can be operated with the flexible instrument of the present invention to enhance guidance of the shaft to the site as well as manipulation at the site. 
     In association with the input devices of  FIG. 2 , there are various feedback techniques can be used for feeding certain parameters sensed at the slave station back to the master station. The following are parameters that may be sensed, including but not limited to: 1. Force. 2. Position. 3. Vibration. 4. Acoustics, auditory. 5. Visual. 6. Neurological stimulus. 7. Electropotential 8. Biochemical sensing. Controller 
     As discussed previously,  FIG. 6  illustrates a computer system  12 , which interfaces the surgeon interface  11  and drive unit  13  of the slave station. The drive unit  13  contains a series of motors that control cables coupled by way of conduit  23  to control certain movements of the catheter apparatus. The controller  12 , depicted in  FIG. 6  essentially links the slave station to the surgeon interface. The user input device electronically sends commands, which are translated by the controller and sent to drive unit  13 . Drive unit  13  then mechanically effects the motion of the shaft, particularly the flexible segment and the tool. 
       FIGS. 14 and 15  are block diagrams of an embodiment of a motor control system that may be employed in a drive unit of the present invention. Regarding the master station side, there is at least one position encoder associated with each of the degrees-of-motion or degrees-of-freedom. At least some of these motions are associated with a motor that may be represented by a combination of motor and encoder on a common shaft. Thus, controlling the motor ultimately controls such parameters as a force feedback to the master station. The present system can comprise a multiaxis, high performance motor control system, which can support anywhere from 8 to 64 axes simultaneously using either eight-bit parallel or pulse width modulated (PWM) signals. The motors themselves may be direct current, direct current brushless or stepper motors with a programmable digital filter/commutator. Each motor accommodates a standard incremental optical encoder. 
     The block diagram of  FIG. 14  represents the basic components of the system. Host computer  700  is connected by digital bus  702  to interface board  704 . Host computer  700  can be, for example, an Intel microprocessor based personal computer (PC) at a control station preferably running a Windows NT program communicating with the interface board  704  by way of a high-speed PCI bus  702  (5.0 KHz for eight channels to 700 Hz for 64 channels) The PC communicates with a multi-channel controller electronic card, providing up to 28 axes of motion control, each with a 1.5 kHz sampling rate. The controller is efficient, scalable and robust. 
     Communication cables  708  intercouple interface board  704  to eight separate module boards  706 . Interface board  704  can be a conventional interface board for coupling signals between digital bus  702  and individual module boards  706 . Each module board  706  includes four motion control circuits  710 , as illustrated in  FIG. 15 . Each circuit  710  can be, for example, a Hewlett-Packard motion control integrated circuit, such as an IC identified as HCTLL1100. 
       FIG. 15  depicts a further sub unit of this system, particularly a power amplifier sub unit  712 . Power amplifier sub unit  712  is based on National Semiconductor&#39;s H-bridge power amplifier integrated circuits for providing PWM motor command signals. Power amplifier  712  is associated with each of the blocks  710 , which couples to a motor X. Associated with motor X is encoder Y. Although the connections are not specifically set forth, it is understood that signals intercouple between block  710  and interface  704  as well as via bus  702  to host computer  700 . 
     The motor control system may be implemented in two ways. In the first method the user may utilize the four types of control modes provided by the motor control sub unit  706 : positional control; proportional velocity control; trapezoidal profile control; and integral velocity control. The use of any one of these modes can involve simply specifying desired positions or velocities for each motor, and necessary control actions are computed by motion control IC  710  of the motor control sub unit, thereby greatly reducing the complexity of the control system software. However, in the case where none of the onboard control modes are appropriate for the application, the user may choose the second method in which the servo motor control software is implemented at the PC control station. Appropriate voltage signal outputs for each motor are computed by the PC control station and sent to the motor control/power amplifier unit ( 706 ,  712 ). Even if the computation load is mostly placed on the PC control station&#39;s CPU, the use of high performance computers as well as high speed PCI bus for data transfer can overcome this problem. 
       FIG. 16  describes the overview of the control algorithm for the present invention, mapping out motions of the catheter to that of the surgeon&#39;s interface handle in three-dimensional space. Such precise mapping can create the feel of the tool being an extension of the surgeon&#39;s own hands. The control algorithm can assume that both the surgeon&#39;s interface as well as the catheter always starts at a predefined position and orientation, and once the system is started, it repeats a series of steps at every sampling. The predetermined positions and orientations, relate to the initial positioning at the master station. 
     First, the joint sensors (box  435 ), which are optical encoders in the present embodiment, of the surgeon&#39;s interface system are read, and via forward kinematics (box  410 ) computation of the interface system, the current positions (see line  429 ) and orientations (see line  427 ) of the interface handle can be performed. The translational motion of the surgeon&#39;s hand motion is scaled (box  425 ) whereas the orientations are kept identical, resulting in desired positions (see line  432 ) and orientations (see line  434 ) of the catheter&#39;s tool. The results are then inputted into the inverse kinematics algorithms for the catheter&#39;s tool, and finally the necessary joint angles and insertion length of the catheter system are determined. The motor controller (box  420 ) then commands the corresponding motors to positions such that the desired joint angles and insertion length are achieved. 
       FIG. 16  provides an initial start position for the handle, indicated at box  440 . The output of box  440  couples to a summation device  430 . The output of device  430  couples to scale box  425 . Initial handle position  440  is established by first positioning the handles at the master station so as to establish an initial master station handle orientation in three dimensional space. Initial handle position  440  is then compared to the current handle position at device  430 . The output from device  430  is then scaled by box  425  to provide the desired tool position on line  432  coupled to the catheter inverse kinematics box  415 . 
     Slave Station 
     The slave station comprises a flexible instrument, e.g. a shaft optionally supporting a tool at its distal end, for insertion into a subject. In one embodiment, the flexible instrument is a catheter. “Catheter” as defined herein refers to a shaft adapted for, but not necessarily limited to, insertion into a subject, and more particularly for insertion into natural body lumens, canals, vessels, passageways, cavities or orifices. The shaft is typically tubular, but any elongate shaft may be adaptable for insertion into the subject. The shaft can be solid or hollow. A subject can be a human, an animal, or even individual organs or tissues that are dead or living. 
     The introduction of the flexible instrument into the human or animal body, may be by percutaneous or surgical access to a lumen or vessel, or by introduction through a natural orifice in the body. In this regard, examples of natural lumens include body vessels such as a blood vessel (artery, chamber of the heart or vein), urinary system vessels (renal collection ducts, calix, ureter, bladder or urethra), hepatobilliary vessels (hepatic and pancreatic ducts, chyle ducts; common or cystic duct), gastrointestinal tract (esophagus, stomach, small and large intestine, cecum and rectum), gynecological tract (cervix, uterus, fallopian tube or milk ducts and mammary canals of breast), nasopharynx (eustacean tube, sinuses, pharynx, larynx, trachea, bronchus, bronchiole, tear duct) seminal vesicle, spinal canal, or ventricles of the brain. Examples of a natural orifice include oral, rectal, nasal, otic, optic, or urethral orifices. 
     The shaft can be constructed from a standard 9 French (2.67 mm diameter) coronary guiding catheter. 
     The shaft may support various forms of tools, typically at its distal end. As depicted in  FIG. 6 , a user can manipulate tool  18  along a single axis of motion where tool  18  is, for example, a grasper, scissors or general mechanism (such as a stapler or clip applier). It is easily understood by those of ordinary skill in the art, however, that tools may be located at a position other than the distal end of the shaft. Preferably the tools aid in carrying out various surgical or medical procedures, including, but not limited to: 1. Grasp; 2. Cut/lyse/puncture; 3. fill/drain; 4. Secure (suture, staple, anchor); 5. Implant, i.e., any procedure that leaves an object in the body after withdrawal of the flexible instrument; 6. Remove; 7. Deliver e.g. drug/therapeutic agents; 8. Hemostasis; 9. Anastomosis; 10. Repair/reconstruct; 11. Dilate/constrict/occlude; 12. Retraction, e.g. backward or inward movement of an organ or part; 13. Coagulate; 14. Laser application; 15. Heat/cool; 
     Exemplary objects implanted in a subject include staples, tacks, anchors, screws, stents, sutures, and a variety of other objects implanted by physicians and medical professionals. 
     The procedure of delivering (procedure  7 , above) can further include delivery of agents including, but not limited to: 1. Adhesives. 2. Cryonics. 3. Drugs. 4. Biologic agents. 5. Radioactive elements. 6. Bulking agents. 
     Furthermore, the flexible instrument can be used as a sensor. Parameters that may be sensed include, but are not limited to: 1. Force. 2. Pressure. 3. Electrophysiological signals. 4. Chemical, oxygen, Ph, blood gas. 5. Temperature. 6. Vibration. 
     The slave station also comprises a drive unit capable of articulating the flexible instrument, particularly the shaft and the tool. The drive unit is to drivably coupled to a receiver for receiving the mechanically drivable mechanism. In one embodiment, this coupling occurs via cables. The drive unit is electronically controllable from the master station, as there is an electronic link between the drive unit and a user input device of the master station. 
     When the receiver receives the mechanically drivable mechanism, the drive unit then has a direct pathway for controlling operation of the shaft and tool. If the shaft has a controlled flexible segment, the drive unit is capable of activating or bending the flexible segment via the mechanically drivable mechanism, for actuation of the shaft, the tool and positioning of the tool at an operative site within the subject. In one embodiment, drive unit is capable of bending the flexible segment via a first set of cables which couple the drive unit to the receiver, and a second set of cables which drivably couple the mechanically drivable mechanism to the flexible segment and the tool. 
     One aspect of the present invention provides a remote controlled outer (guide) catheter having a distal end disposed at or in an area about an operative site, preferably in the immediate area of an operative site. A coaxial inner (working) catheter nested within the outer catheter can then be used to perform the surgical or medical procedure. Previous surgical procedures involve insertion of a trocar or cannula into the subject at a relatively short depth to provide an opening for receipt of the catheter, which is then guided to the operative site. Typically the catheter is not disposed at the immediate area around the operative or target site. Thus, if the surgeon needs a second catheter, the first catheter must be withdrawn and the second catheter is guided to the target site. Such repeated insertions can aggravate trauma experienced by the patient. 
     The feature of the present invention, on the other hand, employs an outer catheter disposed at the target site, which allows more than one shaft to be inserted and withdrawn with minimal irritation or trauma experienced at the passageway leading to the operative site. In one embodiment, the outer catheter housing a coaxial inner catheter is disposed at the target site. The inner catheter can immediately function at the operative site. If a second inner catheter is required, the first inner catheter can be quickly withdrawn through the outer guide catheter and the second inner catheter inserted through the outer catheter with minimal injury to the subject. 
     A feature of this aspect of the present invention allows coaxial multiple shafts to be remote controlled independently of each other.  FIG. 3  depicts a system of remote controlled coaxial catheters. This system employs three coaxial or nested catheters L 1 -L 3 . Dashed line I represents an incision or entry point of the patient.  FIG. 3  also illustrates computer controls C 1 -C 3 , which are outside of and remote from the patient. “Remote from the patient” refers herein to any location outside the sterile field. Computer controls C 1 -C 3  are associated with corresponding actuators A 1 , A 2  and A 3 , (i.e. drive units) which in turn are associated with shafts L 1 -L 3 , respectively. Thus, in  FIG. 3 , for example, the controller C 1  controls an actuator A 1  which, in turn, controls a certain action or movement of the outer shaft L 1 . Those of ordinary skill in the art would readily appreciate that only one computer can be used with software capable of independently controlling actuators A 1 -A 3 . In another embodiment, shafts L 1 -L 3  can be independently controlled by one actuator, which independently drives specific cables leading to each of shafts L 1 -L 3 . Ultimately, the present invention allows shafts L 1 -L 3  to be remote controlled independently from each other. For example, shaft L 1  can remain stationary while shaft L 2  undergoes linear translations or rotations about the co-axis. The distal end of shaft L 3  can also carry out these motions as well as a bend or flex independent of shafts L 1  or L 2 . Shaft L 2  can be controlled to, for example, provide a rotational movement so as to enable rotation of a distal tool. The control of a tool supported at a distal end of a shaft is independent of the motions of shafts L 1 -L 3 . Alternatively, all shafts L 1 -L 3  can undergo a simultaneous bend or deflection at a single operative segment or flexible segment, labeled as O in  FIG. 3 . 
       FIG. 7  illustrates the outer and inner shafts. In  FIG. 7 , shaft  30  comprises an outer shaft  32  housing and coaxial with inner shaft  34 . Outer shaft  32  and inner shaft  34  extend from and within mechanically drivable interface  26 . Interface  26  mechanically couples a drive unit (shown in  FIG. 6 ) with shaft  30 . Interface  26  further comprises a series of control elements, such as pulleys  64  and  72 , which run cable lines  52  and  28 , and gears  60  and  68  for controlling rotation of the shafts. 
     The rotation of outer shaft  32  and inner shaft  34  about the co-axis can be controlled independently. Control element  60 , or gear  60  in interface  26  encircles outer shaft  30  and controls the rotational position of guide shaft  32  in the direction indicated by rotational arrow  65 . Gear  68  in interface  26  encircles inner shaft  34 . Control element  68  controls the rotational position of the inner shaft  34  in the direction indicated by rotational arrow  69 . Rotational arrows  65  and  69  indicate rotation about the “shaft lumen axis”, i.e. the axis tangential to the cross section of the shaft lumen. 
     If a tool were supported at the distal end of inner shaft  34 , control element  68  would control the rotational position of the tool about the shaft lumen axis as well. If the distal end were flexed, the shaft would curve and rotation of the shaft would cause the tool to trace a circle, and not cause the tool to rotate about its internal axis. As described below, another control can be positioned in the mechanically drivable interface for solely controlling the tool independent of the shaft controls. 
     Another aspect of the present invention provides a remote controlled flexible instrument capable of controlled bending, as controlled by a user at a master station. A flexible instrument comprises a shaft having at least one section that is flexible. “Flexible” refers herein to a material that is inherently and sufficiently deformable to readily pass atraumatically through a natural body lumen, cavity, vessel, orifice and the like. In one embodiment, the shaft is sufficiently flexible to readily flex and/or conform to a pathway in an anatomic vessel, lumen, cavity or the like. Non-flexible or rigid catheters can be distinguished from flexible instruments by the following test. By knowing the dimensions of a rigid catheter and the point of entry into the subject, one can calculate the position of the catheter end point inside the subject. In contrast, even if the dimensions and point of entry of a flexible shaft were known, the position of its end point within the subject cannot be calculated with precision because the flexible shaft may bend. 
     Flexible instruments of the present invention can also be distinguished from other known catheters that mimic bending motions solely through a series of rigid sections linked by joints. Thus, a “bend” is not the result of a deformation of the catheter material but by the pivoting or rotation of two rigid sections about a joint. In contrast, flexible instruments of the present invention include at least one flexible segment that is bendable without requiring the use of joints. The bending is remotely controlled, allowing deflection at these flexible segments away from the lumen axis of the segment. Bending in this sense is possible by choice of inherent flexibility of the instrument coupled with an induced deflection at the flexible segment. Inherent flexibility can be achieved by choice of a deformable material, such as. Inherent flexibility can also be achieved by designed construction using a more rigid material, for example carving out segments of the material, i.e. slotting the material, such that the material is sufficiently thin for bending. Of course, the flexible instrument can comprise rotatable or pivotable joints, but the flexible capability is not the result of employing such joints, but by the deformability of the shaft material. In one embodiment, the bending is remotely controlled via a drive unit drivably coupled to the receiver for receiving a mechanically drivable mechanism or shaft mount. The shaft mount is then drivably coupled to the controlled flexible segment, thereby providing a drivable bending mechanism. 
     Those of ordinary skill in the art can appreciate that the shaft can be tailored for a particular body lumen. Factors of the shaft construction include resiliency of the walls of the lumen, curvature of the passageway, location of the target site, diameter of the lumen, etc. For example, a shaft for passing through a colon can be, but is not necessarily, manufactured from a material that is less deformable than a shaft for passing through a small, delicate blood vessel. Lumens that present passageways of high curvature may also require a more easily deformable, and thus more flexible, shaft than does a relatively straight lumen. Deformability of the shaft can also be tailored by varying the dimensions, particularly the diameter, of the shaft. 
     In this aspect of the invention, a user can controllably bend or flex at least a section of the flexible instrument. In one embodiment, this controlled bend can be provided by a shaft having at least one flexible segment, alternatively a controlled flexible segment. By manipulating controls at the master station, a user can induce a bend in the shaft at the flexible segment. Preferably, the bend at the flexible segment is actuated mechanically, thus distinguishing this aspect of the present invention from prior art catheters where the bends are induced electrically. For example, U.S. Pat. No. 5,238,005 describes a bending mechanism caused by varying the electrical resistance through a catheter material having a negative coefficient. Heating one area of a catheter by increasing its electrical resistance results in contraction of that area, causing the catheter to deflect toward the contracted area. In contrast, the present catheter responds to mechanical forces. 
       FIGS. 7 and 8  illustrate one embodiment of a controlled flexible segment.  FIG. 7  shows controlled flexible segment  42  residing between proximal end  36  and distal end  38  of shaft  30 . It is understood, however, that flexible segment  42  can be positioned on any portion of shaft  30 .  FIG. 8  provides an expanded view of flexible segment  42  and illustrates one construction of flexible segment  42 . Here, flexible segment  42  is constructed by providing inner shaft  34  as a flexible material nested within outer shaft  32 . Outer shaft  34  is split into rigid proximal and distal sections  36  and  38 , both encircling inner shaft  34 . Thus, flexible segment  42  is the gap between proximal and distal sections  36  and  38 . Shrink-wrap pieces  44  and  45  extend over the respective facing ends of the proximal and distal shaft sections  36  and  38  and adhere these facing ends to the flexible inner shaft. 
     Alternatively, flexible segment  42  may be in the form of a metal coil of diameter similar to the diameter of outer shaft sections  36  and  38 . 
     Although  FIG. 8  illustrates outer shaft  32  as being rigid, it can be appreciated that outer shaft  32  can be constructed of a flexible material as well, although its flexibility is preferably less than that of inner shaft  34 . 
     Referring to both  FIGS. 7 and 8 , the bending of flexible segment  42  is controlled through flex wire  52  extending from mechanically drivable mechanism  26  and through flexible segment  42 , terminating at point  54  of distal end  38  (see  FIG. 8 ). Flex wire  52  is preferably disposed between inner shaft  34  and outer shaft  32 .  FIG. 8  shows termination point  54  residing on the outer surface of distal end  38 , although conceivably other surfaces of distal end  38  can serve as termination points. The other end wire  52  resides within drivable mechanism  26  on control pulley  64 . Turning pulley  64  has the effect of pulling wire  52  in a direction parallel to shaft  30  pointing towards drivable mechanism  26 . Because wire  52  is terminated at  54 , this pull causes the distal shaft section  38  to deflect in a direction indicated by the arrow  55 , as shown in  FIG. 7 . 
     More than one flex wire can be spaced about the circumference of outer shaft  32  to allow bending along multiple directions different from arrow  55  yet orthogonal to shaft  30 . For example,  FIG. 11  illustrates an embodiment where two cables actuate bending the bending.  FIG. 11  is a cross-sectional view of outer shaft  32  receiving inner shaft  34  at termination point  52 . Two cables  52  A and  52  B terminate on outer  32  on opposite sides of distal shaft section  38 . Cables  52 A and  52 B may be manipulated so as to deflect the distal shaft section in opposite directions, in a manner described previously. Those of ordinary skill in the art can readily appreciate that employing multiple cables results in a shaft capable of deflecting in any number of directions. 
     If inner shaft  34  supports a tool at its distal end, the bending motions, along with the rotation about the co-axis, serves to place the tool at any place in three-dimensional space. Another control element, i.e. pulley  72  controls cable  28 , which extends through the hollow area of inner shaft  34 , thereby allowing control of a specific tool operation. Depending on the complexity of the device, one or more cables leading to the tool may be required. In one embodiment,  FIG. 12  depicts a distal end of shaft  30 , showing operative segment O (e.g. flexible segment  42 ) and tool  18 .  FIG. 12  shows two coaxial catheters including an outer shaft O 1  (such as outer shaft  32 ) and inner shaft O 2  (such as inner shaft  34 ). Also disclosed are two stainless steel cables, including outer cable O 3  and inner cable O 4 . Outer shaft O 1  provides translational and rotary motion. Outer cable O 3 , which is disposed between outer and inner shafts O 1  and O 2 , provides the lateral rotation (or yaw motion) of tool  18 . Inner shaft O 2  rotates tool  18  and inner cable O 4  actuates the jaws of tool  18 . The tool of  FIG. 12  provides a single degree-of-freedom in order to actuate a gripper, scissors or generic mechanism (such as a stapler or clip applier). An example may be a bi-directional gripper 5 mm in length and 2.67 in diameter. 
     In one embodiment, the system comprising the flexible instrument comprises tool or mini-tool ( 18 ), the operative segment ( 42 ), the catheter stem ( 32 ,  34 ), the coupler ( 24 ,  26 ) comprising the mechanically drivable mechanism  26  and the receiver  24 , the drive unit ( 13 ), the controller ( 12 ) and the surgeon&#39;s interface ( 11 ). The coupler provides a translational degree-of-freedom achieved by using a sliding mechanism, i.e. rails  25 , onto which the coupler is mounted, as illustrated in  FIG. 6 . The operative or controlled flexible segment provides a number of articulations in order to position and orient tool  18 . The catheter ( 30 ) has four (4) degrees-of-freedom, i.e. one translation and three rotations, as shown in  FIG. 7 . A fifth degree-of-freedom may be provided by the actuation of the mini-tool, as tool  18  can provide at least a single axis of motion for a grasper, scissors or general mechanism (such as a stapler or clip applier). The combination of one translation and two rotations allows the operative segment to arbitrarily position the mini-tool in three dimensional space. A final degree-of-freedom rotates the mini-tool axially. 
     The following describes the mathematical mapping of the physician&#39;s command input to the motion of the catheter system.  FIG. 13  schematically illustrates the various degrees of freedom by which the catheter can be manipulated, particularly the axial and lateral rotations, or the translation motion allowing independent control of the tool position within the surgical space, as well as axial rotation of the tool. For example, the system of  FIG. 6  provides a physician with seven independent command inputs, including position (X i , Y i , Z i ), orientation (θ i , ω i , Ψ i ) and tool grip angle α i . The controller calculates the position of the five (5) independent degrees-of-freedom of the catheter system. given by (X c , θ c , ω c , Ψ c , α c ), by determining the position (x, y, z) of the tool ,given by X =X c  +r cos ω c , Y =−r sin ω c sin θ c , z =r sin ω c cos θ c Ψ=X c α=α c , where X c , θ c , ω c α c  are the independent inputs to the catheter system, and r is the distance from the lateral joint to tip of the mini-tool. The resulting position is X c =X−r cos ω c , θ c , =tan −1 (−y/z), ω c ,=sin −1 (z/r cos θ c ), Ψ c =Ψ, α c =α. If λ is chosen as a scaling value, the following mapping between command input and independent catheter input is x c =λ i −r cos ω c θ c =tan −1 (−Y i /Z i ), ω c =sin −1 (λZ i /r cos θ c ), Ψ c ,=Ψ, α c =α. It is noted that the axial rotation and grip position are not scaled. 
       FIG. 42  is a perspective view of another embodiment of the slave station for a remote controlled flexible instrument.  FIG. 42  depicts flexible instrument system  500  supported from support bracket  502 , which extend to the operating table (see  FIG. 6 ). Usually the support bracket is supported from the side of the operating table and may be adjustable in position relative to the operating table, to dispose system  500  in a convenient position over the patient. In one embodiment, bracket  502  is secured to the operating table at one end. The other end of bracket  502  supports the entire flexible instrument by means of a two-piece structure similar to that described in copending U.S. Provisional Application Ser. No. 60/279,087 filed Mar. 27, 2001. A knob may be provided on support base  504 , not shown in  FIG. 42 . Once the support base  504  is fixed to the support bracket  502 , then the flexible instrument system is maintained in a fixed position at base  504 , providing a stable and steady structure during the medical procedure. Like  FIG. 6 , system  500  can be positioned at an acute angle with respect to the operating table. 
     Flexible instrument system  500  comprises flexible instrument  510  having a shaft  528  extending to mechanically drivable mechanism  526 , which interlocks with base (or receiver)  506 . Base  506  is supported on carriage  508 . Carriage  508  in turn is adapted for linear translation and supported by elongated rails  512  and  514 . Rails  512  and  514  terminate at one end via end piece  516 , which provides further support. Support base  504  terminates rails  512  and  514  at their other end. Carriage  508  includes bearings or bushings  509  that support the carriage from rails  512  and  514 . 
     Flexible instrument system  500  employs two separate cable bundles for mechanically driving the flexible instrument along rails  512  and  514 . Pulley  521  (dotted outline), residing within carriage control module  520 , receives a first pair of cables  518 . Pulley  521  also receives a second set of cable (see cabling sections  513  and  515  of corresponding  FIG. 43 ), which runs through carriage  508  to a further pulley  522  supported by end piece  516 . The second set of cables controls the translational motion of carriage  508  and terminates at point  519  (see  FIG. 45 ). 
       FIG. 42  also shows a set of cables  524  for driving control elements, e.g. pulleys within receiver  506 . These control elements move the shaft and the tool in several degrees-of-freedom. Arrow J 1  indicates the linear translation via module  520 . Rotational arrow J 2  indicates rotation of flexible shaft  528  of flexible instrument  510  about the inner axis parallel with the shaft length. Arrow J 3  represents the flexing or bending of flexible shaft  528  at controlled flexible segment  530 . In this embodiment, flexible segment  530  is positioned directly adjacent tool  534  at the distal end of shaft  528 . Arrow J 4  represents the pivot action of a wrist joint, which links tool  534  to shaft  528 , about axis  532 . In this embodiment, tool  534  is exemplified as a grasper, and arrows J 5  and J 6  represent the opening and closing actions of the tool jaws. Motions indicated by arrows J 2 -J 6  are controlled from cabling  524  originating at receiver  506 . 
       FIG. 42A  provides an enlarged perspective view of the distal end of shaft  528  including flexible segment  530  and tool  534 . Tool  534  comprises upper grip or jaw  602  and lower grip or jaw  603 , both supported from link  601 . Base  600  is affixed to or integral with flexible shaft  528 . Link  601  is rotatably connected to base  600  about axis  532 . A pivot pin may be provided for this connection. Upper and lower jaws  602  and  603  are rotatably connected to link  601  about axis  536  and again, a pivot pin can provide this connection. 
       FIG. 42A  shows eight cables at  538  extending through the hollow inside of shaft  528  for control of tool  534  and flexible segment  530 . Two of these cables operate the bend of flexible segment  530 , two cables operate one of the jaws  602 , two cables operate the other of the jaws  603  and the last two cables operate the wrist action about the axis  532 . All of these cables travel through the hollow shaft  528  and through appropriate holes in flexible segment  530 , e.g. wire  525 , as well as holes in base  600 . Each of these pairs of cables operates in concert to open and close jaws, pivot about the wrist, and bend flexible segment  530 . 
     One pair of cables travels through shaft  528  and through appropriate holes in the base  600 , wrapping around a curved surface of the link  601  and then attaching to the link. Tension on this pair of cables rotates the link  601  along with the upper and lower grips or jaws  602  and  603  about axis  532 . 
     Two other pairs of cables also extend through the shaft  528  and through holes in the base and then pass between fixed posts  612 . These posts constrain the cables to pass substantially through axis  532 , which defines rotation of link  601 . This construction essentially allows free rotation of link  601  with minimal length changes in the cables passing to jaws  602  and  603 . Thus, the cables actuating jaws  602  and  603  are essentially decoupled from the motion of link  601  and are not effected by any rotation of link  601 . Cables controlling jaw movement terminate on jaws  602  and  603 . These cables permit independent operation of the jaws  602  and  603  in respective clockwise and counter clockwise directions with respect to axis  536 . A similar set of cables is present on the under-side of the link  601  (not shown). Each of the jaws  602  and  603 , as well as the link  601 , may be constructed of metal. Alternatively, link  601  may be constructed of a hard plastic material. Base  600  may also be constructed of a plastic material and may be integral with shaft  528 . 
     Bending of flexible segment  530  is provided via diametrically disposed slots  662 , which define spaced ribs  664 . Flexible segment  530  also has a longitudinally extending wall  665  through which cabling may extend, particularly for the operation of the tool. One of the pairs of cables of bundle  538  controlling flexible segment  530  terminates where base  600  intercouples with shaft  528 . This pair of cables works in concert to cause bending as indicated by arrow J 3 , i.e. in a direction orthogonal to the pivoting provided at wrist axis  532 . In  FIG. 42A  only one cable  525  of two is illustrated. 
       FIG. 43  is an exploded prospective view showing carriage  508 , receiver  506  and drivable mechanism  526 . Carriage  508  is adapted for motion along rails  512  and  514 . Pulleys  521  and  522  receive cabling, i.e. cable sections  513  and  515 , which terminate at the carriage base at point  519 . Other sections of this cable extend through an elongated hole or passage within carriage  508 . 
     Receiver  506  and drivable mechanism  526  each comprise enclosed housings supporting a plurality of control elements, such as intercouplable drivewheels and associated pulleys or cams. Inter-engaging gears  540  and  542  are supported respectively in the modules  506  and  526 . A pair of cables from bundle  524  engages pulley  544  (see  FIG. 45 ) which, in turn, drives gear  540 , and which further, in turn, drives gear  542  for providing rotation of shaft  528 . Collar  546  is provided at the terminus of the proximal end of shaft  528  for supporting shaft  528 , which is driven by gear  542 . Cabling extending through collar  546  and shaft  528  couple mechanical actions from drivable mechanism  526  through the flexible instrument shaft  528  to the distal end thereof. 
     Drivable mechanism  526  interlocks with receiver  506 , providing the mechanical connection that allows the drive unit to run cabling in flexible instrument  510 . Blades  606 , jutting out from the housing of receiver  506 , engage with corresponding slots  608  associated with drivable mechanism  526 . Projecting from the proximal end of receiver  506  is ridge  610 , which is substantially U-shaped and provides another interlocking feature for mating with a similarly shaped slot  614  at the same end of drivable mechanism  526 . Posts  616  protruding from the housing of receiver  506  are adapted to releasably mate with holes  618  in drivable mechanism  526 . Posts  616  and holes  618  to interlock with each other, but may be released from each other via side-disposed buttons  620 , as illustrated in  FIG. 46 .  FIG. 43  also shows the cam locking screws  615 . 
       FIG. 44  is a partial broken away rear elevational view of interlocking interfaces as seen along line  44 - 44  of  FIG. 42 .  FIG. 44  shows alignment posts  616  each having a groove  617 , which is engaged by the corresponding button  620 . Button  620  is in the form of a plate member biased to a locked position by means of spring  621 . A plate for button  620  has a keyhole slot for receiving and holding post  616  therein. Button  620 , however, may be manually depressed to release posts  616  and enable ready detachment of drivable mechanism  526  from receiver  506 . A retaining pin  625  may also be used to limit the travel of the button between in and out positions. 
       FIG. 45  is cross-sectional side view through the interconnecting modules taken along line  45 - 45  of  FIG. 42 .  FIG. 45  shows details of drive wheels (or pulleys) in the modules  506  and  526 . Four drive wheels  622  are supported within the housing of receiver  506 . Drive wheels  622  receive cabling for controlling the motions of the shaft and the tool, where the cable protrudes from cable bundle  524  in  FIG. 43 . Each of these pairs of cables is controlled from a corresponding motor, which is part of the drive unit (see discussion of  FIG. 49 , below). 
       FIG. 45  also shows output blades  606 , previously shown in  FIG. 43 , which extend into corresponding slots  608 . These slots are disposed in respective intergaging drive wheels  624  of the drivable mechanism  526 . Blades  606  have a rectangular end construction for engaging with similar rectangular slots  608  associated with the module  526 .  FIG. 45  also shows the gears  540  and  542  in engagement to allow drive to occur from bundle  524 . 
       FIGS. 45 and 46  show a series of idler cams  626 , one associated with each of drive wheels  624 .  FIG. 46  is a plan cross-sectional plan view through receiver  506  as taken along line  46 - 46  of  FIG. 45 .  FIG. 46  shows the placement of cams  626 . A cable wraps around each of drive wheels  624  and is held in position by its associated cam  626 .  FIG. 46  also shows all of the cables running parallel to each other at region  627 , where the cables run from respective drive wheels  624 , through collar  546  and extending down inside shaft  528  to the distal end. With the use of the placement and adjustment of cam  626 , the cables are all directed in a manner to easily couple into shaft  528 . 
     Each of cams  626  has an off-center axis  631 . As viewed in  FIG. 46 , cam  626  may be rotated clockwise to tighten its associated cable. Rotation counterclockwise loosens the tension. Cam locking screws  615  secure cam  626  in an adjusted-to position (see  FIG. 48 , a cross-sectional view taken along line  48 - 48  of  FIG. 47 ).  FIG. 48A  is a cross-sectional view taken along line  48 A- 48 A of  FIG. 48 . As depicted in  FIGS. 46 and 48A , the cable associated with each wheel  624  may be secured in a cable clamping hole  633  via a cable clamping screw  635 . A similar clamping arrangement is associated with wheels  622 . A roll pin fixes each wheel  622  to each spindle  607 . 
       FIG. 47  is a cross sectional plan view taken through receiver  506 , as taken along line  4747  of  FIG. 45 . The cross-sectional view of  FIG. 47  illustrates drive wheels  622  associated with receiver  506 . Drive wheels  622  receive cabling from cable bundle  524 . Each of a pair of idler pulleys  630  are associated with drive wheels  622 . At the very input to receiver  506 , idler pulleys  632  are used for directing the cable to idler pulleys  630  and from there to drive wheels  622 . 
       FIG. 48B  is a fragmentary plan view of a drive wheel engagement slot by itself as seen along line  48 B- 48 B of  FIG. 48A . The cross-sectional views of  FIGS. 48A and 48B  illustrate drive wheels  622  within receiver  506  having associated end blades  606 . End blade  606  is a screwdriver-type blade that engages a slot previously identified as slot  608  in  FIG. 43 . This slot  608  is in drive wheel  624  of receiver  526 . In  FIG. 48B , slot  608  displays a tapered portion. The tapered portion allows easy registration of end blade  606  and slot  608 , and thus easy registration between drive wheel  622  and drive wheel  624 . 
     As described to this point, the bending or deflection of the shaft can be actuated by mechanical means such as a wire extending along a length of the shaft. Thus, actions at the distal end of shafts may be controlled by mechanical elements, such as cables, wires or other tendons. 
     Alternatively, actuation of the controlled bending can occur by other means, such as by remote electromagnetic signal couplings.  FIG. 41A  illustrates shaft  850  having a central lumen. Residing in the central lumen is an operative or controlled flexible segment O, in the form of a plurality of spaced electromagnetic rings  852 , separately labeled as R 1 , R 2 , R 3  and R 4 . Each of rings R 1 -R 4  is associated with wires  854 , similarly labeled as wires W 1 , W 2 , W 3  and W 4 . Rings  852 , once energized, provide bending of shaft  850  at flexible segment O.  FIGS. 41A and 41D  are meant to be schematic, while  FIGS. 41B and 41C  are actual implementations for actuation of the rings by means of coils or windings  853 . As illustrated in  FIG. 41B , each ring may be electrically energized via a winding  853  associated therewith.  FIG. 41B  shows a fully wound winding, while  FIG. 41C  shows a half wound winding. Ring  852  may also have two separate half wound coils on opposite sides thereof. Wires  854  (in pairs) are selectively energized to energize windings  853  on the rings, which in turn, provide either attraction or repulsion of the rings.  FIG. 41D  illustrates the results of regions of rings  852  being energized to attract or repel adjacent rings. For example, a certain direction of current flow through windings  853  can create an attraction of the coils at the bottom and a repulsion of coils at the top. This cooperative action causes a bending at the operative or controlled flexible segment O. 
     The flexible instrument depicted in  FIGS. 6 and 7  provides only the distal end as being remotely controlled. It can readily be appreciated that a controlled flexible segment may be provided, not necessarily for action at a target site, but to control certain movements of the catheter to assist in reaching a target site. 
       FIGS. 4 and 5  illustrate the advantages of a flexible instrument, particularly a catheter having controlled flexibility via controlled flexible or operative segments, for use in performing a procedure or for guiding the instrument through a natural body lumen.  FIG. 4  provides a schematic cross-sectional diagram, illustrating a catheter K for use in mitral valve repair, to be discussed in more detail below.  FIG. 4  also shows catheter K supporting a tool  18  for carrying out certain procedures at the mitral valve annulus, also described in further detail below. In  FIG. 4 , catheter K is shown entering the femoral vein V by a percutaneous access at S. From the femoral vein V, catheter K must bend prior to entering the right atrium R. Catheter K then passes through a septal wall of the heart to the left atrium L, which is directly above the mitral valve M. In this particular embodiment, the operative segment of the catheter K is illustrated at O and is positioned near the very distal end of the catheter K. Thus, at the sharp, almost 90.degree. bend prior to entering right atrium R, a user can controllably bend catheter K at the operative segment, to perform a procedure with tool  18 . Also, the ability to controllably bend catheter K prevents tool  18  from conceivably being trapped within femoral vein V, causing damage to the walls of vein V. In this embodiment, it may be preferable to have at least some length of catheter K constructed of a deformable or flexible material, enabling the catheter to easily pass through the body lumen by essentially conforming to vein configurations, such as that of femoral vein V. 
       FIG. 5  provides a schematic cross-sectional diagram illustrating a surgical procedure where catheter K 1  enters a natural body orifice, such as the urethra for carrying out procedures in, for example, the bladder. In  FIG. 5  catheter K 1  is shown extending into bladder B 1 . In this example, the computer controlled segment, identified as operative or flexible segment O in  FIG. 5 , is positioned at a more proximal section of catheter K 1 . Bladder B 1 , being an open cavity, does not have lumens leading from the urethra that would naturally guide a catheter towards any particular operative site. Upon entering bladder B 1 , catheter K 1  can bend in any direction and not necessarily in the direction of the operative site. In this embodiment, because of the more proximal positioning of operative segment O, a surgeon can controllably bend the distal end of catheter K towards the operative site. In the embodiment shown in  FIG. 5 , the distal end of the catheter, labeled P 1 , can be rigid or be “passively” flexible, i.e. made of a flexible material and not necessarily controlled for flexure under remote computer control. 
     In the illustration of  FIG. 4 , the catheter K may be fed through the femoral vein by direct surgeon manipulation, in which case only the operative segment O is under computer control from a master station. Alternatively, the catheter may translate linearly through the vein under remote master station control, where the catheter can have other operative segments disposed at different locations of catheter K. Each of these operative segments can be controlled from a master station for assistance in the guiding of the catheter to a predetermined target site. Thus, the catheter may be inserted manually and also have remote computer control for at least limited linear translation. 
       FIGS. 3A-3C  show different embodiments of flexible instruments with multiple operative or controllable flexible segments. Shafts having multiple operative segments can be very useful for procedures in a body cavity, as discussed previously, but can also be useful in navigating the shaft through intricate or delicate body lumens.  FIGS. 3A-3C  schematically illustrate controller CT and a slave portion of the system comprising actuators or drive units A 1 -A 4  and shaft KA, KB or KC having three operative segments O 1 -O 3 . In accordance with each of these embodiments, a surgeon inputs commands from a master station to cause certain corresponding movements of the shaft at the slave station. A surgeon&#39;s manipulations at the master station are coupled to controller CT where these manipulations are mapped to actions at operative segments O 1 -O 3 . Thus, a surgeon, at an appropriate input device, may carry out a first manipulation to control a segment O 1 , a second different manipulation to control the segment O 2  and still a third manipulation to control the segment O 3 , either simultaneously or sequentially. A fourth manipulation may control the tool G. 
       FIG. 3A  shows shaft KA having three operative segments, O 1 , O 2 , and O 3 , and tool G at its distal end. Actuators A 1 , A 2  and A 3  are associated respectively with operative segments O 1 , O 2  and O 3 . Actuator A 4  controls tool G. Each of actuators O 1 -O 3  is controlled from controller CT. Operative segments O 1 , O 2  and O 3  are spaced a certain distance apart from each other, allowing shaft KA to simultaneously experience controlled bends. This arrangement may be necessary for lumens with multiple bends, or for hard to reach operative sites. 
       FIG. 3B , shows catheter KB having tool G 1 . In this embodiment, three operative segments O 1 , O 2  and O 3  are spaced from each other along the length of catheter KB. Segments O 1 -O 3  can be controllably bent to form an arc having an imaginary radius point P. Thus, this arrangement of operative segments can actuate particularly acute bends. In another embodiment, catheter KC in  FIG. 3C  employs three operative segments O 1 -O 3 , which are contiguous. The radius of curvature can be increased. 
     It is understood that non-operative segments of the catheter in  FIGS. 3A-3C  can comprise either a flexible or a rigid material. It can be appreciated that one or more controlled flexible segments can be incorporated in the shaft, depending on the particular application. 
     Another aspect of the present invention provides a remote controlled flexible instrument operable within the sterile field, and disposable after use. The sterility of reusable medical instruments and implements are maintained by well-known methods such as exposure to sterile solutions and/or autoclaving. For some medical implements, it can be more cost effective to manufacture them from low cost materials and dispose them after a single use, or use on a single patient. But for certain other medical instruments, its manufacture from low cost materials still results in a costly product due to the intricate nature of the individual parts and the labor required to manufacture complex components. 
     It is another feature of the present invention to provide a design for a remote controlled flexible instrument having disposable components, particularly those components that are exposed to the sterile field. The present design allows the use of injection-molded plastic parts. The disposable component can be easily and quickly engaged into and disengaged from a non-disposable, reusable base. The components can be locked onto the base by snapping or interlocking matched parts, without having to thread cable wires or attach any intricate components. 
     One aspect of the present invention provides a disposable implement comprising a disposable mechanically drivable mechanism, a disposable shaft extending from the drivable mechanism, and optionally a disposable tool supported on a distal end of the shaft. Referring back to  FIG. 7 , mechanically drivable mechanism  26  comprising gears  60  and  68  and pulleys  64  and  72 , can be manufactured from injection molded plastic, as well as shaft  30  extending from drivable mechanism  26 . The sides of pulleys  64  and  72  feature a first semicircular planar disc stepped up from a second matching semicircular planar disc. The sides of the pulleys in receiver base  24  correspondingly match the stepped up pattern of pulleys  64  and  72 . Engaging drivable mechanism  26  onto receiver  24  requires matching and interlocking the respective pulley discs. Thus, the interlocking feature in effect extends the cabling pathway from the first set of cables running from the drive unit to receiver  24 , to a second separate set of disposable cables contained within drivable mechanism  26  and shaft  30 . No tying or threading of cables is required to engage the disposable portion onto receiver  24 . 
     Another design for a disposable implement is illustrated in  FIG. 42 . In  FIG. 42 , the flexible instrument  510 , comprising drive mechanism  526  and shaft  528 , can be a single piece disposable unit that is readily engageable and disengageable relative to the base module  506 . 
     Disposable implement  510  may be considered as comprising a disposable, mechanically drivable mechanism such as the coupler or module  526  interconnected to a tool  534  through an elongated disposable flexible shaft or stem  528 . This disposable and flexible implement is mounted so that the mechanically drivable mechanism may be connectable to and drivable from a drive mechanism, such as illustrated in  FIGS. 6 and 7 . In the illustrated embodiment the drive mechanism may be considered as including the coupler or module  506  and the associated drive motors. The disposable elongated flexible instrument is generally inserted into a body vessel or cavity of a subject along a selected length of the disposable elongated instrument with the elongated flexible instrument being disposable together with the disposable mechanically drivable mechanism. 
     The disposable implement is purely mechanical and can be constructed relatively inexpensively thus lending itself readily to being disposable. It may be difficult to make only the tool disposable, due to the intricate nature of the tool parts, which may require the user to perform intricate maneuvers and cable threading into the base of the slave station. Here, the disposable implement, i.e. the tool, shaft and drivable mechanism are manufactured as a single piece disposable unit, thus eliminating the need for intricate instrument or tool exchange procedures. 
     Ideally, the base of the slave station, which contacts the disposable implement, is easily cleanable. It is preferred that the disposable implement, which operates within the sterile field, experiences minimal contamination by contacting the slave station. In one embodiment of the present invention, as illustrated in  FIG. 43 , the interlocking drivable mechanism  526  and receiver  506  features substantially planar surface at the point of contact between the two modules. Regarding receiver  506 , the planar surface is easy to clean and the inner intricate pulleys and cabling are protected from contamination by the housing. Regarding mechanically drivable mechanism  526 , the housing can be made of injection-molded plastic that is simple to manufacture and is easily disposable. 
     One advantage of the present invention is the ease of engaging and disengaging the disposable implement. In a particular medical procedure, a multitude of instrument exchanges may be required, and the system of the present invention is readily adapted for quick and easy instrument exchange. Because the receiver is maintained in a fixed position, the surgeon can easily exchange instruments by readily decoupling at the modules  506  and  526 . The ease of exchanging instruments lends to the portability of the slave station. This portable nature of the slave unit comes about by virtue of providing a relatively simple flexible instrument in combination with an adaptor (module  506 , module  520 , carriage  508  and associated components) for supporting the flexible instrument. Overall, the slave station is of a relatively small configuration. Because the slave unit is purely mechanical, and is decouplable from the drive unit, the operator can readily position the slave unit. Once in position, the slave unit is then secured to the support, and the mechanical cabling of the slave unit is then attachable to the drive unit. This makes the slave unit both portable and easy to position in place for use. 
       FIG. 49  shows an embodiment where pulley  677  is readily manually decouplable from motor  675 . For this purpose pulley  677  may be a two-piece pulley arrangement comprising a coupler spindle and a coupler disk with the coupler disk secured to the output shaft of the motor. This enables the entire assembly to be disconnected at the motor so that the flexible instrument system  500  with its flexible instrument  510  may be positioned relative to the patient, independent of any coupling with the drive motors. Once the system illustrated in  FIG. 42  is in place, then the coupling of the cables can be made at pulley  677  to provide drive to the flexible instrument system. 
     Another aspect of the present invention provides a system for repairing a cardiac valve, such as a mitral valve. Current mitral valve repair techniques, either open or minimal access, require the surgeon to place the patient on cardiopulmonary bypass and stop the heart. The left atrium is then opened and exsanguinated to allow the surgeon to perform the repair. This aspect of the present invention provides a minimally invasive mitral valve annuloplasty technique featuring the following advantages: (1) peripheral venous access; (2) the heart can continue to beat during the repair; and (3) assessment of the correction of valve incompetence in real-time using, for example, Doppler ultrasound guidance. 
     In one embodiment, the present cardiac valve repair system employs a guide shaft extending from a site outside a patient to an area about the cardiac valve. The guide shaft receives a flexible inner shaft for disposing a tool at the area about the cardiac valve, where the tool is supported at the distal end of the guide shaft. Preferably, the inner shaft has a relatively small diameter enabling percutaneous intravascular and endoscopic surgery. Even more preferably, the inner shaft, and optionally the guide shaft, is capable of accessing the mitral valve from the peripheral circulation, eliminating the need for incisions through the chest wall. In one embodiment, the inner shaft can have a diameter ranging from 8 to 15 French (2.5-5.0 mm). The outer catheter may be constructed from a standard 9 French coronary guide catheter, having a diameter of 2.67 mm and a wall thickness of 0.1 mm. In other embodiments, the inner catheter can have an outer diameter of 1.1 mm and an inner diameter of 0.09 mm. In yet another embodiment, the braided stainless steel cables are 0.63 mm in diameter and are capable of transmitting 178 Newtons (40 lbs. approx.). 
     A feature of this aspect of the present invention is that the percutaneous access to the mitral valve can be accomplished on a beating heart, eliminating the risks associated with cardiopulmonary bypass (CPB). To enable a procedure on the beating heart, preferably the procedure can be performed under physiologic conditions. The physician may monitor the procedure by, for example, transesophageal echocardiography, instead of a video image. This technique enables real-time assessment of the correction of the mitral valve regurgitation (MR) during the procedure, further enabling intra-operative provocative cardiac testing, with preload and afterload challenges and cardiac pacing all under trans-esophageal echo and trans-thoracic ultrasound guidance to optimize repair. 
     The tool can be remote controlled, as described herein, and can be designed for use in any procedure of the cardiac valve repair process. For example, a first set of tools is capable of percutaneous mitral valve annuloplasty. This represents a paradigm shift in management of disease from MIS and open surgical to intraluminal interventions. While this catheter-based intervention is described in connection with mitral annuloplasty, the technique can also be applied to other structures such as, by way of example and not limiting, the billiary tree, the genitourinary tract and intraventricular neurosurgery. 
     The system further includes a retainer at the area of the cardiac valve, where the retainer is attached to an annulus of the cardiac valve. As will be described in greater detail below, the retainer is closeable via the tool to draw the annulus into a smaller diameter. 
     In one embodiment, a trans-septal guide catheter is used to guide and support an inner catheter. The guide catheter is introduced by percutaneous access, and allows the clinician to access the left atrium via the venous circulation, i.e. through the heart wall (see  FIG. 4 ). The guide catheter may be non-robotic, i.e. simply manipulated manually by the surgeon. Alternatively, the guide catheter may be robotically controlled from surgeon manipulations at an input device of the master station. 
     Once access to the left atrium is established, the inner catheter is threaded into the left atrium through the guide catheter. The inner catheter contains attachment anchors for deployment at desired points around the mitral valve annulus. A remote controlled 5-degree-of-freedom tool and wrist can be utilized to precisely reach the annulus. Ultrasound may be used to visualize the system and guide the anchor positioning and placement. This ultrasound may be trans-esophageal ultrasound or trans-thoracic ultrasound, for example. Furthermore, electrophysiologic signals of the heart may be used to aid in precisely locating the position of the tool at the fibrous mitral valve annulus. 
     There is now described a number of techniques employing the catheter apparatus of the present invention. These techniques are described herein primarily in connection with mitral valve repair. 
       FIG. 19  is a schematic representation of the heart muscle showing the left ventricle  218 , the right ventricle  219 , the left atrium  220 , the right atrium  221  and the aorta  222 . Between the left atrium and the left ventricle, blood flow is from the left atrium through the mitral valve  210  to the left ventricle  218 .  FIG. 26  illustrates an expanded view of a mitral valve at  210  including annulus  211  and leaflets  213 .  FIG. 27  illustrates schematically the leaflets  213  of the mitral valve  210  with the mitral valve annulus  211 . As a heart muscle ages, it is typical for the annulus of the mitral valve  210 , illustrated in  FIG. 19  at  211 , to expand in diameter causing problems with the leaflets  213 . If the leaflets fail to close properly, regurgitation may result, causing leakage by the mitral valve in the reverse direction and resulting in improper blood flow through the heart. Thus, mitral valve repair involves, at least in part, shrinking the diameter of the annulus to allow the leaflets to operate properly. 
     In one embodiment, threading or sewing a ring about the annulus reduces the annulus diameter, where the ring is closeable. The annulus comprises relatively tough tissue just above the top of leaflets. As viewed in  FIG. 19 , the opposite end of the annulus at  217  tends to expand outwardly.  FIG. 19  illustrates an area at the annulus of the mitral valve (that annulus being at the top in  FIG. 19 ) identified as trigone area  215 , where the valve ring is more rigid and remains stationary. Because this area is relatively stable and rigid, it is thus difficult to contract, and most of the expansion of diameter of the ring occurs away from the trigone area. This, again, is illustrated in  FIG. 20  by the positions shown in solid and in dotted outline. 
       FIG. 20  shows schematically parts of the heart such as the left atrium  220  and the left ventricle  218 , with the mitral valve  210  disposed therebetween.  FIG. 20  illustrates the annulus of the mitral valve in solid position, at a smaller diameter where the leaflets operate properly. The dotted outline  217  represents the expanded diameter of the base of the mitral valve, the state at which mitral valve leakage can occur. 
     To carry out the technique of the present invention, a guide catheter  230  is employed, such as a transseptal atrial guide catheter. The access for catheter  230  is via the vena cava to the right atrium  221 . This access may be from above via the jugular vein or below by way of the femoral vein. A puncture is made in the wall  238  of the right atrium into the left atrium  220 , allowing distal end  232  of catheter  230  to pass into the left atrium  220 . 
       FIG. 17  illustrates one method of shrinking the diameter of the annulus.  FIG. 17  shows a metal wire ring  100  in place about the mitral valve annulus. The ring  100  may be initially secured at the trigone area  103  of the mitral valve annulus. The technique illustrated in  FIG. 17  may rely upon a catheter apparatus, such as depicted in  FIGS. 6 and 7  herein with an operative segment. At least limited linear translation of the catheter may be accomplished with an apparatus similar to that described in  FIG. 6 , although a guide catheter may also be manually inserted at least partially by the surgeon through percutaneous access via the femoral vein. The ring  100 , although depicted in a ring configuration in  FIG. 17 , can be first inserted through the catheter in a straightened configuration. The metal wire or ring  100  is preferably constructed of a material such as Nitinol. The characteristics of this material include the ability to retain its form or to be stretched to a straight position. Once the material is passed through the catheter, it can spring back to its ring configuration. The surgeon preferably matches the configuration of the ring, particularly as to its size, to provide a proper fit for the particular mitral valve that is being repaired. 
     Once the straightened wire  100  has passed through the catheter, it assumes the position shown in  FIG. 17 . The ring, once in place, is secured to the annulus via wire clips  106  and/or sutures  102 . By drawing on these sutures with the tool, the diameter of the mitral valve annulus is reduced so that it conforms to the size of the wire loop  100 . As with other techniques described herein, the control is supplemented by visual considerations such as with the use of ultrasound or electrophysiological feedback. 
       FIG. 18  provides another embodiment of the present invention employing a catheter system for mitral valve repair.  FIG. 18  provides a schematic representation of a ring  210  of a cardiac valve, such as a mitral valve. Fiber  212  is looped about or sewn around the annulus (base) of the valve. A number of different types of stitches may be used. The fiber may be a thread or a wire. In the embodiment of  FIG. 18 , the fiber is actually sewn through the annulus of the valve. After the fiber is sewn in this manner, tension is applied to ends  214  of the fiber. The tightening reduces the diameter of the ring, brings the valve leaflets into their proper position so as to avoid valve regurgitation. 
       FIG. 20  also illustrates a balloon  234  that may be supported at the distal end  232  of the catheter  230 . Once the catheter  230  is in place, balloon  234  is inflated to further support the guide catheter in place with the end  232  extending slightly into left atrium  220 . Once balloon  234  is inflated or opened, it can be snugged back against the septal wall  238  between left atrium  220  and right atrium  221 . The inner diameter of the catheter  230  may be on the order of approximately 5 mm in diameter.  FIG. 24  shows an enlarged view of catheter  230 , with its end  232  and the associated balloon  234  holding catheter  230  in place. 
     As an alternate to the use of a balloon  234 , a malecot  236  may be used. This is a mechanical device with expandable wings, as illustrated in  FIG. 25  and associated with catheter  230  so as to hold the end  232  of the catheter in place relative to the septal wall  238 . 
       FIG. 20  also illustrates a flexible catheter  240  with its associated tool  242  extending from the guide catheter  230 . Tool  242  may be a pair of jaws operable for threading or sewing fiber. These jaws can be controlled externally at a user interface by a surgeon. With regard to flexible catheter  240 , reference is made to co-pending provisional application, U.S. Ser. No. 60/269,200, as well as pending application PCT serial number PCT/US00/12553, filed Nov. 16, 2000, both documents of which are hereby incorporated by reference herein. 
     In  FIG. 23  reference is also made to the fiber  212  and an end piece  245  that is secured to one end of the fiber  212 . Fiber  212  is shown sewn through wall  247 .  FIG. 23  also schematically illustrates the tool  242  engaging the fiber  212 . 
     After guide catheter  230  is in place with the balloon  234  inflated to secure it in position, flexible catheter  240  is threaded through guide catheter  230  to a position just about the mitral valve, as illustrated in  FIG. 20 . Fiber  212  may also, at the same time, be threaded through the catheter member  230  with end piece  245  being accessible for being secured to the valve ring. As illustrated in  FIG. 20 , the beginning position of the threading or sewing of the fiber  212  is at a position close to or at the trigone area  215  of mitral valve  210 . 
     After a single threading or sewing has occurred, such as in  FIG. 23 , then the jaws of tool  242  loop stitch the fiber  212 , which may be a small but rigid wire, about the mitral valve in the manner illustrated in  FIG. 18 . Staples  249  may also be employed for holding the wire in place. 
       FIGS. 21 and 22  illustrate another embodiment to secure an end of fiber  212 . In this embodiment, the end of fiber  212  is pulled so as to close the diameter of the base ring of the mitral valve.  FIG. 21  illustrates guide catheter member  230  at its end  232 , being held in place against the septal wall  238  by balloon  234 . Flexible catheter  240  with its tool  242  has been withdrawn from catheter member  230 . Double-walled structure  250  comprises coaxially arranged inner and outer tubes  252  and  254 . Fiber  212  extends through these tubes and carries therealong a securing piece  256  and a retaining button  258 . The inner tube  252  is adapted to engage the retaining button  258  and the outer tube  254  is adapted to engage the securing piece  256 .  FIG. 22  shows securing piece  256  and retaining button  258 , along with the fiber  212 . 
     Initially, once the threading through the base of the valve ring is completed, the outer tube  254  engages securing piece  256  moving it downwardly in the view of  FIG. 21  while the fiber  212  is held in position. This tightens the securing piece  256  against the other side of the trigone area  215 , of  FIG. 20 . Once the diameter of the ring has been tightened, inner tube  252  is moved downwardly to engage retaining button  258 . Button  258  grabs fiber or wire  212  and at the same time retaining button  258  engages and interlocks with the securing piece  256 . In this way, both ends of the threaded fiber or wire  212  are secured roughly at the positions illustrated in  FIG. 20 . The pulled fiber  212  causes the mitral valve ring to draw into a smaller diameter such as the position shown in solid, rather than the in-dotted position of  FIG. 20 . 
     Once the securing piece and the retaining button are firmly held to the wire  212 , then the member  250  may be withdrawn through the guide catheter  230 . The flexible catheter member  240  may then be reinserted with a different tool such as a pair of scissors for cutting the exposed end of the fiber  212 . 
     Another possible technique for reducing the annular diameter involves a loop of cable that extends through hooks or anchors placed in the annulus, as illustrated in  FIG. 29 .  FIG. 29  shows the cable or wire  120  and schematically illustrates the anchors at  125 . In this technique the valve is reduced through a “lasso” technique, in which the cable exerts an equal force on all of the anchors. This technique uses an articulate catheter preferably inserted through a guide catheter, such as illustrated hereinbefore, to place the anchors one at a time into the mitral valve annulus. The cable onto which the anchors are suspended provides the closing force when tensioned by the operator. 
     In one embodiment, the flexible instrument comprises a guide catheter  150 , as illustrated in the diagram of  FIG. 30 . Inner catheter  155  houses an anchor and cable system depicted generally at  160 , including tensioning cable  162  and anchors  164 . Five degrees-of-freedom are provided: (1) rotary, (2) linear, (3) flexure motion with regard to the guide catheter  150  as well as (4) linear and (5) rotary motion with regard to the inner catheter  155 . 
     Guide catheter  150  may be approximately 8 French in diameter with a computer controlled flexible end portion, illustrated in  FIG. 30  as operative segment O. A computer controls three degrees-of-freedom with regard to the guide catheter  150 , along with two degrees-of-freedom of inner catheter  155 . Refer to  FIG. 30  and the corresponding motions F 1 -F 5 . 
       FIG. 30  depicts anchors  164  as having a loop and two legs, although other anchor designs can be readily contemplated. The legs of each anchor  164  may curl outwards. Once anchors  164  are deployed from the constraint of the inner catheter, they curl outwardly. The curling motion of the anchor legs secures them to the fibrous tissue of the mitral valve annulus. Preferably the anchors are fabricated from a super-elastic material such as Nitinol. 
     A tensioning cable, such as the cable or wire  162  illustrated in  FIG. 30  may pass through each of the loops of the anchor. This allows an equal force to be placed on each anchor and prevents the anchors from becoming loose in the bloodstream. The tensioning cable passes back through the robot inner catheter and out of the patient. The final tension is adjusted manually by the surgeon (or by computer) to optimize the annular size under direct visualization. Also, within the inner catheter is preferably disposed a deployment wire used to advance and fire the anchors into the annulus wall. 
       FIGS. 30A and 30B  depict a cable termination tool set. This set comprises two catheters used to: (1) crimp the end of the tether cable once the tension is placed on the annulus; and (2) cut off the remaining cable at the end of the procedure. Both of these catheters may use a four-bar linkage or other system. 
       FIG. 30A  shows a crimp tool  172  having a pair of jaws  174  that can be used to crimp member  176  about the tether cable  170 . Thus, the first catheter  172 , which may be referred to as a cable crimper, holds the crimp element  176  in the jaws  174  with the tether cable  170  pre-threaded through the crimp element and catheter shaft. The tensioning of the cable may be performed under ultrasound guidance. Although one tether cable  170  is shown in  FIG. 30A , opposite ends of the tether that come from the mitral valve site preferably extend through the crimp element  176 . Once the tether cable is tensioned, so as to bring the mitral valve into its proper diameter, then the crimp element  176  is actuated by the cable crimper  172  illustrated in  FIG. 30A . Once the proper tension is achieved, the crimper is actuated by applying tension on the push-pull drive cable  175  and by closing the crimp element at the jaws  174  so that the crimp element crimps the tether cable  170  in the proper position and at the proper tension. 
     After the crimping or securing step, then the cable crimper is removed and the cutting catheter  182  is introduced as also illustrated in  FIG. 30B . This catheter is also introduced over the tether cable  170  and through the guide catheter. It is advanced up to the crimp, and severs the cable with its jaws  184  by tensioning the push-pull drive cable  185 . The procedure is now completed and the system catheters are then removed. 
     As indicated previously, the proximal end of the catheter is comprised of a disposable coupling mechanism that engages a drive mechanism, such as is shown in  FIGS. 6 and 7 . For this purpose, the coupler, identified in  FIGS. 6 and 7  as couplers  24  and  26  are adapted for disengagement therebetween. One coupler section may be considered as transmitting motion to the guide catheter while the other coupler section may be considered as transmitting motion to the inner catheter and the drive cable. This involves the mechanical coupling of the guide catheter with the coupler so that actions of the guide catheter are controllable from the mechanical control elements of the coupler. 
     In one embodiment, a drive unit is coupled with the inner shaft and the guide shaft independently, the drive unit capable of independently effecting movement of each shaft to at least one degree of freedom. 
     For each coupler element, rotary disks transmit motion from the remotely controlled drive system to the catheter articulations. By way of example, in a first coupler element, a horizontal disk may drive the distal flexure. Another element may include disks, which control the axial and/or rotary positions of the inner catheter and, for example, the advance of the anchors. All of the coupling elements are mounted on a slider or sliders, which allows independent control of the linear advance of the outer and inner catheters. Again, refer to  FIGS. 6 and 7 . The catheter system including the inner and outer portions, as well as the proximal coupling element are disposable and mount removably to the drive member. 
     In accordance with the technique, such as described in  FIG. 29 , when the last anchor is in place, the inner robot catheter and deployment wire are removed. The physician can manually (or under computer control) adjust the tension in the cable and thus the diameter of the mitral valve after the first element of the cable termination system is threaded over the cable and through the robot guide catheter. Since this procedure is performed on a beating heart, the annular size can be optimized under direct ultrasound guidance. Once the mitral valve annulus has been precisely adjusted, a cable termination system, such as the one depicted in  FIGS. 30A and 30B , clamps and cuts the cable. This completes the mitral valve repair procedure. 
     Another feature of the present invention provides a system for closing the base of a cardiac valve, such as a mitral valve. The closing can occur primarily by a stapling technique in which staples are attached to the valve ring or annulus to draw the annulus into a smaller diameter. In this way the leaflets are then more appropriately positioned for opening and closing. 
       FIG. 31  illustrates a staple array comprising delivery system  342  including storage housing  349  for a plurality of staples  350 . Each of staples  350  is a surgical staple movably mounted within housing  349 . Cable or wire  312  interconnects and loops through each of staples  350 . Each staple  350  includes a pair of pointed ends  351  and center loop  353 . The staple  350  at the most distal end of housing  351  (i.e. nearest the exit of housing  351 ) has cable  312  attached fixedly at loop  353 , to prevent losing staples in the subject. For the remaining staples, cable or wire  312  freely loops through center loop  353 . A release mechanism, not illustrated in  FIG. 31 , but which may be a standard design, can be used to move staples  350 , one at a time, out of the housing  349 .  FIG. 31  also schematically illustrates a clamping mechanism  352  at the distal end of housing  349 , for closing each of staples  350  as they exit housing  349 . 
       FIG. 32  illustrates another method for repairing a mitral valve, featuring the use of staples to secure a ring to the mitral valve annulus. As will be described in further detail, a tether cable or filament is threaded through an array of staples or anchors via a first inner catheter. Once the attachment anchors are placed around the annulus, the first inner catheter is removed and a second inner catheter is disposed in the guide catheter. This second inner catheter allows the clinician to apply tension to the cable to reduce the mitral valve annulus circumference, in effect, pulling on a lasso. The annuloplasty is monitored by real-time echocardiographic quantitation of regurgitant flow attenuation, with and without after-load reduction. The clinician monitors the cardiac physiology for resolution of regurgitation. When the hemodynamics are optimized, still a further inner catheter device may be used so as to place a stop or crimp on the cable. Still another inner catheter device may be used to cut the cable. These latter two inner catheter devices may be robotic or non-robotic catheters. 
       FIG. 32  features mitral valve  210  with trigone area  215 . Guide catheter  330  accesses the vena cava and passes to the right atrium  221 . This access may be from above via the jugular vein or below by way of the femoral vein. A puncture is made in septal wall  238  separating right atrium  221  from left atrium  220 , allowing distal end  332  of guide catheter  330  to access left atrium  220 . 
     Balloon  334  may be supported at distal end  332  of guide catheter  330 . Once guide catheter  330  is positioned at a desired location, balloon  334  is inflated to secure guide catheter  330  to the wall with end  332  extending into the left atrium. Once balloon  334  is inflated, it can be snugged back against the septal wall between left atrium  220  and right atrium  221 . The inner diameter of the catheter  330  may be on the order of approximately 5 mm in diameter. As an alternative to balloon  334 , a malecot may be used, i.e. a mechanical device having expandable wings capable of securing catheter  330  against septal wall  238 . 
     Guide catheter  330  coaxially nests flexible catheter  340  and its associated staple delivery system  342 . With regard to this catheter construction, reference is made to a co-pending provisional application, Ser. No. 60/269,200 filed Feb. 15, 2001, as well as pending application PCT serial number PCT/US00/12553, filed Nov. 16, 2000, both of which are incorporated by reference herein in their entirety. 
     After balloon  334  is inflated to secure guide catheter  330  in position, flexible inner catheter  340  is threaded through guide catheter  330  to a position just above mitral valve  210 , as illustrated in  FIG. 32 . Delivery system  342 , associated with inner catheter  340 , also passes through catheter  330 , holding fiber  312  and staples  350  to an area about the mitral valve. 
       FIG. 32  also illustrates fiber  312  tracing a circumference about annulus  211 , terminating at two end locations  345  and  356 . The area traced by fiber  312  and where the stapling occurs is at a ring of relatively tough tissue just above the top of leaflet  213 . The area not traced by fiber  312  is valve trigone area  215 , which is relatively fixed and not easily contracted. Thus, the repair of the mitral valve, involving decreasing diameter  217  from dotted line to solid line, occurs away from trigone area  215 . 
     Flexible catheter  340  is manipulated to cause a stapling about annulus  211  of mitral valve  210 . The releasing of each staple is controlled by a mechanism preferably within flexible catheter  340  and operable from a user interface station remote from the subject. Once all of the stapling has occurred, wire  312  is pulled in the direction of arrow  361  in  FIG. 32 . This pulling causes a closure of valve annulus  211 , as desired. Once the clinician is satisfied that the repair is complete, the cable  312  is then locked off with a crimp, such as illustrated at  365  in  FIG. 33 . This crimp may be facilitated by the insertion of a different catheter member  340  within the catheter  330 , all while the cable  312  is held in the proper cinched-down position. 
     A plurality of staples  350  having loops  353  encircling fiber  312 , secures fiber  312  to the annulus of the mitral valve, terminating at points  345  and  356 . The procedure of looping fiber  312  and stapling can be performed via remote control from a master station under surgeon control with multiple degrees-of-freedom of the tool so as to accurately locate the implant fiber  312  and staples  350 . 
     Fiber  312  is fixedly secured to end staple  350  at point  345 . The remaining staples are free to glide along fiber  312 . When all the staples are secured about the annulus, fiber  312  may be cinched down under ultrasonic guidance, watching for a reduction or elimination of the valve regurgitation. Once adequate tension has been placed on the cable  312 , tension can be maintained without disengaging the closure system. This allows the clinician to monitor the patient for some period of time to confirm that the repair has taken place. Once the clinician is satisfied with the repair, the cable can be locked off with a crimp or by some other technique and the cable may then be cut. 
     Another feature of the present invention is that the technique can be performed under physiologic conditions. The physician can monitor the procedure by, for example, transesophageal echocardiography, instead of a video image. The aforementioned “lasso” technique enables real-time assessment of the correction of the mitral valve regurgitation (MR) as the “lasso” is tightened. This enables performance of intra-operative provocative cardiac testing, with preload and afterload challenges and cardiac pacing all under trans-esophageal echo and trans-thoracic ultrasound guidance to optimize repair. 
       FIG. 33  illustrates an expanded view of the finished repair region. A staple  350  is fixedly attached to fiber  312  at position  345 . Pulling cable  312  through various loops  353  of staples  350  causes pulling of the annulus into a smaller diameter, thus closing the valve from an initially larger diameter, dotted outline  217 , to a smaller diameter, solid outline in  FIG. 32  at  217 . 
     An alternate embodiment of a staple is illustrated in  FIG. 34 . Staple  362  may be an elastic-like staple, such as a nitinol staple. Staple  362  is normally biased to a closed position. A delivery system employs rod  364 , or the like, to hold staple  362  open. As the rod is moved longitudinally to the array, each staple in sequence is sprung closed. Such an arrangement would avoid the necessity of a clamping mechanism  352  as illustrated in  FIG. 31 . 
       FIGS. 35A and 35B  illustrate other embodiments of an outer catheter  550  and an inner catheter  554  extending through septal wall  560 . These embodiments illustrate the outer (guide) catheter as a robotic catheter. It is understood that the instrument embodiments of  FIGS. 20 and 32  may also encompass systems where the guide shaft is robotic. In  FIG. 30 , the guide catheter is also robotic. In  FIGS. 35A and 35B , arrow  557  indicates rotation of outer catheter  550 , and arrow  559  indicates flexing of outer catheter  550 . In  FIGS. 35A and 35B , inner catheter  554  can experience linear motion along the co-axis (arrow  562 ) and rotational motion (arrow  564 ). The outer catheter  550  may also be capable of independent linear translation.  FIG. 35A  illustrates inner catheter  554  as being capable of a controlled flex or bend, i.e. inner catheter  554  has a controlled flexible segment. Thus, the inner catheter of  FIG. 35A  is capable of deflecting in the direction of arrow  566 . 
       FIG. 38  illustrates another embodiment of a catheter. Catheter  402  supports dumbbell-shaped balloon  414 . As illustrated in  FIG. 39 , catheter  402  can be introduced into the left ventricle  218  directed upwardly with balloon  414  disposed at mitral valve  210 . The mitral valve  210  separates the left ventricle  218  from the left atrium  220 . As shown in  FIG. 39 , associated with the mitral valve is a ring of relatively tough tissue (the annulus) just above the top of valve leaflets  213 . 
       FIG. 36  shows a cross-sectional view of the use of catheter  402  and balloon  414  for mitral valve repair.  FIG. 36  shows the plurality of peripherally disposed anchor pins  405 .  FIG. 36A  shows each anchor pin comprising a piercing end  426  and a loop end  428 . A fiber or tether  408 , as illustrated in  FIGS. 36 and 37  extends through each of the loop ends  428  and has its ends at  409  free to extend through the catheter  402  to an external site where the tether can be tightened, as will be described in further detail hereinafter. 
       FIG. 37  also shows the position wherein pins  405  have been inserted into wall  247 , which is a section of the ring of the mitral valve just above the leaflets. Pulling tether ends  409  together can close the ring, thus pulling loop ends  428  into a smaller diameter. This smaller diameter reduces the diameter of the ring of the mitral valve so as to minimize or prevent valve regurgitation. 
     Initially,  FIGS. 38 and 39  illustrates balloon  314  positioned at a desired location and in a deflated state.  FIG. 38  illustrates pins  405  disposed about a center section of balloon  414 . In the rest or deflated position as illustrated in  FIG. 38 , the pins disposed at their most inner diameter. This innermost diameter state is also represented in the cross-sectional view of  FIG. 36 . Tether  408  may extend by way of catheter  402  to an external site where it can be operated, e.g. outside the body. 
     Once the catheter and balloon are in place, such as illustrated in  FIG. 39 , the balloon is inflated by a balloon inflation lumen in the direction of arrow  439  in  FIG. 40 . Arrangements for inflating balloons are well known and are practiced, for example, in the angioplasty field. Inflation pressure may be coupled by way of the port  441  to the interior of balloon  414  causing the balloon to expand. In  FIG. 40  the balloon is shown only partially expanded. When fully expanded, the anchor pins  405  extend to the ring just above the leaflets as indicted at  445  in  FIG. 40 . The corresponding cross-sectional view is shown in  FIG. 37 , depicting the anchor pins  405  penetrating and anchoring the tissue.  FIG. 37  illustrates a placement of tether ends  409 . As the trigone portion of the base ring of the mitral valve is the most stable portion of the ring, it is preferred that tether ends  409  leave the loop at approximately the trigone area. In this way the drawing in of the diameter of the ring is more effective. 
     After the anchors are seated, as illustrated in  FIG. 37 , tether  408  can be tightened, thereby pulling the tissue together so as to repair the mitral valve and reduce or eliminate valve regurgitation. 
     Several different techniques may be used for guiding the catheter  402 . For example, transesophageal ultrasound or transthorasic ultrasound may be employed. Also, radiopaque dye fluoroscopy or electrophysiologic techniques may be employed for positioning of the catheter. 
     The tether can be placed about the mitral valve and tightened by using coaxial inner and outer catheters. The concepts illustrated in  FIGS. 39 and 40  may be practiced either with or without robotic control. 
     The aforementioned techniques for guiding the catheter may also be used for monitoring the effectiveness of the technique of the present invention. By monitoring the positioning of the balloon, one can assure that the ends of the tether are preferably at the trigone area. Also, as the tether is tightened, the surgeon may monitor the mitral valve activity to determine whether the valve base ring has closed properly so as to reduce or eliminate valve regurgitation. Tether ends may be secured by knotting the ends thereof so as to hold the tether in a closed position. 
     The techniques described herein may also be applied in other medical procedures involving repair of other anatomic body members. For example, the techniques described in  FIGS. 17-40  may be used in closing, tightening, or constricting other anatomic conduits including, but not limited to, lumens, valves, or sphincters. One example is in connection with drawing the sphincter into a smaller diameter. This smaller diameter is particularly useful in controlling “acid reflux” by constricting an expanded sphincter that couples between the stomach and esophagus. By tightening the sphincter, stomach acids are restricted to the stomach and don&#39;t pass back toward the esophagus. Access for such a technique may be via the patient&#39;s mouth. Of course, the techniques of the invention may also be applied in virtually any other medical procedures performed internally on the patient. 
     The present invention provides a relatively simple system, both in the construction and in its use. The capability to decouple components at the drive unit and the receiver results in a readily portable and readily manually insertable flexible instrument system that can be handled quite effectively by the surgeon or assistant when it is to be engaged with the patient. Only a minimal number of components are positioned within the sterile field, enabling facile manipulation about the surgical site. An advantage of the system of the present invention is the decoupling nature of the system. In the system of the present invention, the instrument, drive unit and controller are inherently decoupled (attachable and detachable). The decouplable design enables the slave station to be readily portable. The instrument can be maintained as sterile but the drive unit need not be sterilized. 
     The instrument of the present invention is relatively small because the actuators are not housed in any articulating structure in the system of this invention. Because the actuators are remote, they may be placed under the operating table or in another convenient location and out of the sterile field. Because the drive unit is fixed and stationary, the motors may be arbitrary in size and configuration. Finally, the design allows multiple, specialized instruments to be coupled to the drive unit, allowing a user to design the instrument for particular surgical disciplines. 
     Having now described a limited number of embodiments of the present invention, it should now be apparent to those skilled in the art that numerous other embodiments and modifications thereof are contemplated as falling within the scope of the present invention.