Abstract:
The present disclosure describes a method and apparatus for guide catheterization. In one embodiment, a guiding catheter system includes a flexible shaft having a distal end shaped for accessing a target vessel. A handle assembly is movably coupled to the flexible shaft. The flexible shaft is selectably movable between a plurality of discrete positions of a first degree-of-freedom defined relative to the flexible shaft. The flexible shaft restrained in the first degree-of-freedom at each position of the plurality of discrete positions. The flexible shaft movable through a predetermined displacement of a second degree-of-freedom defined relative to the flexible shaft at each position of the plurality of discrete positions. Motion of the flexible shaft relative to the handle assembly results in a controllable sweeping motion at the distal end of the flexible shaft.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates generally to catheter systems, and, more particularly, to a method and apparatus for positioning guide catheters.  
       BACKGROUND  
       [0002]     Guiding catheters are indispensable medical devices that allow a physician to locate and cannulate vessels in a patient&#39;s anatomy for performing various medical procedures. Guiding catheters are commonly used in cardiac access procedures such as heart vessel mapping (venography) and implanting of cardiac pacing devices. Cannulating heart vessels typically requires navigating a small diameter, flexible guide through convoluted vasculature into a heart chamber, and then into a destination heart vessel. Once the destination heart vessel is reached, the catheter acts as a conduit for insertion of payloads into the vessel.  
         [0003]     In one example of a cardiac implant procedure, pacing devices may be implanted on both sides of the heart. One pacing device is placed in the right ventricle and the other pacing device is placed in the great coronary vein. A guiding catheter can be used to implant this second device into the coronary vein by cannulating the coronary sinus ostium (located in the right atrium) with the catheter.  
         [0004]     The ostium of the coronary sinus is a relatively small opening in the right atrium that provides access to the coronary sinus. As a result, the procedure involved in locating the ostium can be time consuming and difficult. The physician may have various aids in locating the coronary sinus, such as imaging or sensors. Notwithstanding such aids, locating the ostium can still be hit or miss, as it relies on the skill of the physician in properly manipulating the proximal end of the catheter. A more organized way of allowing the physician to search for a vessel such as the coronary sinus is desirable.  
       SUMMARY  
       [0005]     The present disclosure describes a method and apparatus for guide catheterization. In one embodiment, a guiding catheter system includes a flexible shaft having a distal end shaped for accessing a target vessel. A handle assembly is movably coupled to the flexible shaft. The flexible shaft is selectably movable between a plurality of discrete positions of a first degree-of-freedom defined relative to the flexible shaft. The flexible shaft restrained in the first degree-of-freedom at each position of the plurality of discrete positions. The flexible shaft movable through a predetermined displacement of a second degree-of-freedom defined relative to the flexible shaft at each position of the plurality of discrete positions. Motion of the flexible shaft relative to the handle assembly results in a controllable sweeping motion at the distal end of the flexible shaft.  
         [0006]     In one arrangement, the first degree-of-freedom includes a longitudinal displacement relative to the flexible shaft, and the second degree-of-freedom includes an axial rotation relative to the flexible shaft. In another arrangement, the first degree-of-freedom includes an axial rotation relative to the flexible shaft, and the second degree-of-freedom includes a longitudinal displacement relative to the flexible shaft. The handle assembly may include a guide member attached to the shaft, and a housing movable coupled to the guide member via a slot and pin arrangement. The handle assembly may include a tightening member between the flexible shaft and the handle assembly, the tightening member providing a releasable coupling between the flexible shaft and the handle assembly.  
         [0007]     In another embodiment of the present invention, a method of locating a destination vessel, involves introducing a catheter shaft into an access vessel that provides access to the destination vessel. Until the destination vessel is located by a distal end of the catheter shaft, the following is repeatedly performed: 1) mechanically restraining a proximal end of the catheter shaft from travel in a first degree-of-freedom relative to the catheter shaft at one of a plurality of positions of the first degree-of-freedom, 2) moving the proximal end of the catheter shaft through a mechanically limited displacement of a second degree-of-freedom defined relative to a centerline of the catheter shaft. The destination vessel is then cannulated with the distal end of the catheter shaft.  
         [0008]     In one aspect of the method, the first degree-of-freedom includes a longitudinal displacement relative to the flexible shaft, and the second degree-of-freedom includes an axial rotation relative to the flexible shaft. In another aspect, the first degree-of-freedom includes an axial rotation relative to the flexible shaft, and the second degree-of-freedom includes a longitudinal displacement relative to the flexible shaft. The method may also involve moving the shaft through mechanically limited displacement via a handle assembly movably coupled to the catheter shaft. The method may further involve adjustably locating the handle assembly on the proximal end of the catheter shaft.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a cutaway view of a heart showing a guiding catheter according to embodiments of the present invention positioned in the right atrium;  
         [0010]      FIG. 2  is a side view of a guiding catheter handle showing relative longitudinal motion of the catheter shaft according to embodiments of the present invention;  
         [0011]      FIG. 3  is a side view of a guiding catheter handle showing relative axial rotation of the catheter shaft according to embodiments of the present invention;  
         [0012]      FIG. 4  is a cross-sectional view of the guiding catheter handle according to embodiments of the present invention;  
         [0013]      FIG. 5  is a perspective view of a slotted guide member according to embodiments of the present invention;  
         [0014]      FIG. 6  is a perspective view of a slotted guide member with an alternate slot arrangement according to embodiments of the present invention; and  
         [0015]      FIG. 7  is a cross-sectional view of an alternate arrangement of the guide handle according to embodiments of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0016]     In the following description of the illustrated embodiments, references are made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration, various embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized, and structural and functional changes may be made without departing from the scope of the present invention.  
         [0017]     In broad and general terms, the present invention is directed to a method and apparatus for guide catheterization that is suitable for placing devices in anatomical locations such as cardiac vessels. In one embodiment, the catheter includes an improved guide handle to assist in a methodical and thorough search for an anatomical feature at the catheter&#39;s distal end.  
         [0018]     With reference to  FIG. 1 , a guiding catheter assembly  100  is illustrated according to embodiments of the present invention. The guiding catheter assembly  100  includes an elongated, flexible shaft  102  that can be introduced in anatomical passageways to support medical procedures. The medical procedures may include delivery of drugs, sensors, pacing leads, defibrillation leads, or other diagnostic objects into the heart  110  and associated vessels.  
         [0019]     The flexible shaft  102  may be formed of an extruded tube of a single polymer material. Alternatively, the shaft  102  may be assembled using a multiple-layer construction. Typically, multi-layer shafts include a core tubing portion with various coatings/layers on inner and outer surfaces to impart desired properties to those surfaces while still keeping the shaft reasonably flexible. Typically, outer surface coatings are chosen to provide an impermeable and smooth outer surface, while inner surfaces may include lubricous coatings that allow easier movement of devices within the lumens. Other features may be included with the shaft  102 , such as an embedded stainless steel or fiber braid, which provides longitudinal stiffness.  
         [0020]     The flexible shaft  102  includes a pre-shaped distal end  104  that may be introduced into the target vessel. In this example, the distal end  104  is shown located in the right atrium  112  of the heart  110 . The distal end  104  is shaped to access a particular target vessel. The target vessel may include heart vessels such as the coronary sinus  114 . The coronary sinus  114  is often approached via an access vessel  116  of the vasculature such as the cephalic vein. An incision  117  is made in an access vessel  116  and the catheter assembly  100  introduced into the heart  110  from the incision  117 . In the illustrated access path, the catheter enters the heart  110  through the superior vena cava  118  and into the right atrium  112 .  
         [0021]     While maneuvering the flexible shaft  102  to its destination, the distal end  104  may be placed in the general vicinity of the target vessel  114 . The physician must carefully move a proximal end  120  of the flexible shaft  102  to locate the distal end  104  in an opening  122  of the target vessel  114 . In this example, the opening includes the coronary sinus ostium  122 . The physician may be assisted in locating the ostium  122  using visualization techniques such as X-ray fluoroscopy, and/or be assisted by sensors placed on the catheter shaft  102 .  
         [0022]     Even with visual and/or sensory aids, placing the distal end  104  of the catheter  100  into the ostium  122  can be difficult. The physician is manipulating a long and relatively flexible shaft  102  from the shaft&#39;s proximal end  120  while the shaft  102  is located in a tortuous venous pathway. This may result in exaggerated and uncontrolled movements (e.g., “whipping”) at the proximal end  120 . The flexible shaft  102  may offer little or no tactile feedback to the physician. This makes it difficult for the physician to perform a systematic probing of a particular area to locate the target vessel  114  or other anatomical feature.  
         [0023]     To overcome these difficulties, the catheter  100  includes a handle  124  adapted to aid the physician in performing a systematic search for anatomical features at the distal end  104 . Relative movement between the flexible shaft  102  and handle  124  is controlled in such a way that the physician can perform a systematic search for an anatomical feature at the catheter&#39;s distal end  104 . The handle  100  includes features that provide more controlled movement at the shaft&#39;s distal end  104 , as well as providing indexing features that allow the physician to perform the search in a methodical and repeatable fashion.  
         [0024]     In general, the handle  124  and shaft  102  may be relatively moveable both in longitudinal translation and axial rotation. The movements of the handle  124  and shaft  102  can be controlled in the translational and rotational directions to assist in a systematic search. In reference now to  FIG. 2 , a side view of the catheter  100  shows relative translational motion between the catheter handle  124  and shaft according to embodiments of the present invention. The shaft  102  can move in through all or part of the handle  124  in a longitudinal direction as indicated by the arrow  202 . The effect of longitudinal motion is to displace the distal end  104  as indicated by the displaced end  204  drawn in broken lines.  
         [0025]     In  FIG. 3 , a side view of the catheter  100  shows relative rotation between the catheter handle  124  and shaft according to embodiments of the present invention. The shaft  102  may be rotated along its longitudinal axis relative to all or part of the handle  124  as indicated by the curved arrow  302 . The effect of longitudinal motion is to rotate the distal end  104 , as indicated by the rotated position  304  shown in broken lines.  
         [0026]     It will be appreciated that the physician can longitudinally and rotationally move the shaft  102  without the use of the handle  124 . The handle  124 , however, provides a restraint on this motion, thereby allowing such movements to be systematic and controllable. One arrangement of a handle  124  and shaft  102  for enhanced shaft control according to embodiments of the present invention is shown in  FIG. 4 . The handle  124  includes an outer housing  402  that can be gripped by the physician. The housing  402  may contain features that provide easier holding and manipulation, such as a textured outer surface and/or a thumb handle  404 .  
         [0027]     The flexible shaft  102  may be fixably attached to a guide member  406 . The guide member  406  has an inner bore  408  through which the flexible shaft  102  can pass. A sealing cap  410  attaches to a threaded portion  412  of the bore  408 . The sealing cap  410  can be made from a standard rotating hemostatic valve (RHV) cap. When the sealing cap  410  is tightened, the cap  410  attaches the flexible shaft  102  to the guide member  406 .  
         [0028]     A seal  414  (e.g., an RHV seal) may be located between the guide member  406  and the flexible shaft  102 . The seal  414  may be compressed by tightening of the sealing cap  410  to create a fluid-impermeable seal between the guide member  406  and the flexible shaft  102 . Once the sealing cap  410  is tightened, the flexible shaft  102  and guide member  406  can be moved as a single unit.  
         [0029]     The guide member  406  is movable within a bore  416  of the housing  402 . To provide a smooth and low-friction interface between the guide member  406  and bore  416 , bearings  418  may be employed. The bearings  418  may be separate elements such as pressed-in bushings. In other configurations, the bearings  418  may be formed as one or more features of the bore  416 .  
         [0030]     The movement of the guide member  406  within the bore  416  may be controlled via the interactions of a pin  420  and slot  422  arrangement. As shown, the pin  420  extends from the inner surface of the bore  416  and the slot  422  is formed in the guide member  406 . A spring  423  can provide a compressive or tensile force that keeps the pin  420  and slot  422  from unintentionally shifting positions. It will be appreciated that a reverse configuration, with the pin  420  extending from the guide member  406  and the slot  422  formed in the bore  416 , will provide a similar result as the illustrated arrangement.  
         [0031]     The slot  422  may be formed as a serpentine path that includes a plurality of circumferential channels  424 . These circumferential channels  424  correspond to a rotational movement between the catheter shaft  102  and handle  124  at fixed longitudinal orientations. The circumferential channels  424  are joined by axial segments  426  that provide transitions between adjacent fixed longitudinal orientations of the catheter shaft  102  and handle  124 .  
         [0032]     A perspective view of the slotted guide member  406  is shown in  FIG. 5 . The slot  422  includes circumferential channels  424  and axial segments  426  arranged on the outer surface of the guide member  406  in a channels  424 . The spacing distance  502  may be a constant or variable distance between adjacent pairs of circumferential channels  424 . The circumferential channels  424  each define a fixed longitudinal orientation within the total longitudinal travel length  504 . In each fixed longitudinal orientation, the catheter shaft can rotate axially, but cannot move longitudinally relative to the handle.  
         [0033]     The length of each circumferential channel  424  defines a rotation angle  506 . The rotation angle  506  defines the maximum angle that the catheter shaft can be rotated for a given longitudinal location. The circumferential channels  424  may be of substantially identical length, so that the rotation angle  506  is the same at each longitudinal orientation. In other arrangements, the rotation angle  506  may be different at different longitudinal orientations. It will be appreciated that the movement of the guide member  406  may be adjustably limited to a lesser longitudinal travel length  504  and rotation angle  506  than provided by the slot arrangement  422 . For example, an adjustable stop member may be placed between the guide member  406  and the housing  402  (see  FIG. 4 ) to limit one or both of relative rotation and longitudinal travel.  
         [0034]     The slot  422  configuration shown in  FIG. 5  is only one possible configuration that can provide a catheter assembly with guiding features according to the present invention. For example, the axial segments  426  may be formed as curved segments that more smoothly join adjacent circumferential channels  424 . In another configuration, the axial segments  426  may be joined into a single channel that extends across the entire longitudinal travel length  504 , so that the slot arrangement  422  resembles a ladder.  
         [0035]     In general, any slot arrangement that allows a user to perform a systematic traversal of a search area may be used with an apparatus as described herein. In general, the slot arrangement fixes the catheter shaft in discrete positions of a first degree-of-freedom while allowing the catheter to move though a displacement of a second degree-of-freedom. For example,  FIG. 6  illustrates an alternate slot arrangement  422 A for a guide member  406 A of a catheter according to embodiments of the present invention. This slot arrangement  422 A include a plurality of axial channels  602  that are joined by circumferential segments  604  to form a serpentine shape. In contrast to the slot  422  shown in  FIG. 5 , the slot  422 A allows constant longitudinal translation at a plurality of fixed rotational angles. Each of the axial channels  602  corresponds to a fixed rotational angle.  
         [0036]     Mechanical apparatuses other than a pin-slot arrangement may be used to movably couple a catheter shaft and handle as described.  FIG. 7  illustrates an alternate catheter handle assembly  124 A that may be used with a catheter assembly according to embodiments of the present invention. The handle  124 A includes an outer housing  700  that may be gripped by the user.  
         [0037]     The outer housing  700  has a bore  701  in which a slide housing  702  is placed. A rotating member  704  is located within the slide housing  702 . The rotating member  702  has an inner bore  708  through which the flexible shaft  102 A can pass. The flexible shaft  102 A can be fixably attached to the rotating member  704  using an RHV sealing cap  706  or similar apparatus.  
         [0038]     The rotating member  704  can turn within the slide housing  702 . One or more bearings  714  may be employed to provide a low-friction rotational interface between the rotating member  704  and the slide housing  702 . The extent that the rotating member  704  may turn within the slide housing  702  may be limited to an angle analogous to the rotation angle  506  shown in  FIG. 5 . The rotation angle may be limited by features (not shown) on the rotating member  704  or slide housing  702 . These rotational limits may be fixed or adjustable.  
         [0039]     The slide housing  702  is longitudinally movable relative to the outer housing  700 , and this motion is typically limited to discrete steps. A longitudinal indexing mechanism  716  may be used to provide discrete control of longitudinal motion between the slide housing  702  and the outer housing  700 . The indexing mechanism  716  may include such features as a ratchet  718  and linear gear  720  for moving or indexing the slide housing  702  in discrete steps. Other mechanical features known in the art may be also used as an indexing mechanism  716 , such as thumbwheels, ball and detent arrangements, frictional stops, etc. A spring  722  may be used provide a compressive or tensile force to assist the operation of the indexing mechanism  716 .  
         [0040]     Referring again to  FIG. 1 , the guiding catheter assembly  100  may be used in procedures that require anatomical access via a convoluted pathway. Guiding catheters are commonly utilized in heart treatments because of the indirect access routes used to enter the heart. In one example, provided for purposes of illustration, a congestive heart failure treatment may involve implanting a pacing lead into the coronary sinus  114 . In some implantation procedures, the guiding catheter assembly  100  is introduced through an incision  117  in the upper vasculature. The catheter shaft  102  can be introduced through this incision and into a guide vessel  116  of the vasculature. The distal end  104  of the catheter shaft  102  enters into the right atrium  112  through the superior vena cava  118 .  
         [0041]     After the shaft&#39;s distal end  104  is located in the right atrium  112 , the shaft  102  must be manipulated to place the shaft&#39;s distal end  104  in the coronary sinus  114 . The ostium  122  of the coronary sinus  114  is located on a wall of the atrium  112  and the procedure typically requires considerable manipulation to place the catheter shaft  102  into the ostium  122 . The shaft  102  may include a shaped distal end  104  specially designed for this task.  
         [0042]     After the catheter shaft  102  is located in the atrium  112 , the handle assembly  124  may be slid over a distal part of the flexible shaft  102  and tightened into place. It will be appreciated that the handle assembly  124  may be formed integrally with the catheter shaft  102 , so that the handle assembly  124  is already located at a distal part of the shaft  102  during this part of the procedure. In either case, the physician may have the ability adjust the location of the handle assembly  124  relative to the shaft  102  to so that the handle assembly  124  is positioned for maximum control and comfort.  
         [0043]     Once an optimum location of the handle assembly  124  is found, the handle assembly can be tightened on the shaft  102 , such as by using an RHV seal cap  410  (see  FIG. 4 ). Other adjustments may also be required before or after tightening the handle assembly  124 , such as setting the appropriate rotational orientation and/or setting adjustable stops that control relative movement between the shaft  102  and handle assembly  124 . The physician can then begin to move the shaft  102  within the handle assembly  124  to provide a sweeping motion at the shaft&#39;s distal end  104 . The sweeping motion continues until the ostium  122  is located.  
         [0044]     Other features known in the art may be included with the guiding catheter assembly  100  to assist in this search for the ostium  122 . A steering apparatus (not shown) may be used in the catheter shaft  102  to allow deflection of the distal end  104  during access procedures. Such steering apparatuses typically include tensile members slidably deployed in lumens of the shaft  102  and fixed near the distal end  104  of the shaft. The tendons are pulled at the catheter assembly&#39;s proximal end  120  to change a bend angle of the distal end  104 . During a sweeping search using the handle assembly  124 , various bend angles may be set at the distal end by using a steering apparatus.  
         [0045]     The catheter assembly  100  may also utilize sensors (not shown) mounted on the distal end  104  of the shaft  102 . These sensors may include any combination of temperature, ultrasound, visual, pressure, velocity, conductivity, and/or fluid flow sensors, as well as electrodes (e.g., mapping electrodes). Outputs of the sensors can be monitored during the sweeping search for the ostium  122 . By utilizing a handle assembly  124  for a smooth and controllable sweeping search, the output of such sensors will tend to be less erratic and therefore be more useful to assist in finding the ostium.  
         [0046]     It will, of course, be understood that various modifications and additions can be made to the embodiments discussed hereinabove without departing from the scope of the present invention. Accordingly, the scope of the present invention should not be limited by the particular embodiments described above, but should be defined only by the claims set forth below and equivalents thereof.