Abstract:
A device for positioning a reference element during aortic valve implantation surgery. The device includes a first extension member having a proximal end and a distal end, a connection member adapted to connect the first extension member to a support, and a coupling having a first end connected to the connection member and a second end connected to the proximal end of the first extension member so that the first extension member is moveable in multiple planes relative to the support. At least one reference datum is operatively connected to the distal end of the first extension member and extends in a straight line, the reference datum being moveable between a first position and a second position to enable precise locating of the reference datum during the aortic valve implantation surgery.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of the filing date of U.S. Provisional Application No. 61/559,933, filed Nov. 15, 2011, the disclosure of which is hereby incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Heart valve disease, and particularly aortic heart valve disease, has been a medical problem for many years. Over time, natural aortic valves may leak, causing aortic insufficiency or regurgitation, or may become blocked or exhibit limited function due to aortic stenosis. Early heart disease treatments included insertion of either a mechanical or prosthetic valve through a median sternotomy and open heart surgery. 
         [0003]    Although improvements to open heart surgery have been made over the years, resulting in a significant lessening of mortality and morbidity rates, open heart surgery still remains a very involved and complicated undertaking. Moreover, post-operative recovery is often lengthy. Efforts therefore continue to develop non-surgical techniques for managing heart valve disease. 
         [0004]    One such non-surgical technique involves percutaneous aortic valve replacement. With this technique, a valve is transported to the heart via, for example, the femoral vein through a small incision made in the groin. However, no matter how successful, this technique also exhibits limitations. For example, the path from the groin to the aortic valve via the femoral vein is relatively lengthy and requires crossing of the mitral valve. Crossing of the mitral valve can itself induce mitral insufficiency and reduced cardiac output. 
         [0005]    More recently, surgeons have been opting for a transapical approach to aortic valve replacement. Under this approach, surgeons reach the native aortic valve with a catheter pre-loaded with a replacement valve. Generally, the catheter and valve assembly are placed through the apex of the heart in an antegrade approach. With this technique, precise and exact positioning of the replacement valve is required. Heretofore, surgeons manipulated the catheter delivery device exclusively by hand. However, it would be advantageous to assist with the process by providing both stability for the catheter delivery device and a reference datum for the surgeon. It would also be beneficial to provide novel surgical methods for taking advantage of such a fixed reference mechanism. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    The present invention addresses these and other needs. In accordance with an embodiment of the invention, a device for positioning a reference element during aortic valve implantation surgery may include a first extension member having a proximal end and a distal end; a connection member adapted to connect the first extension member to a support; a first coupling having a first end connected to the connection member and a second end connected to the proximal end of the first extension member so that the first extension member is moveable in multiple planes relative to the support; and at least one reference datum operatively connected to the distal end of the first extension member and extending in a straight line, the reference datum being moveable between a first position and a second position to enable precise locating of the at least one reference datum during the aortic valve implantation surgery. The support may be selected from the group consisting of surgical tables and surgical retractors. 
         [0007]    The at least one reference datum may be a rigid rod. The at least one reference datum may also include a first rigid rod extending in a first direction, a second rigid rod extending in a second direction orthogonal to the first direction, and a third rigid rod extending in a third direction orthogonal to the first and second directions. 
         [0008]    The first coupling may have a first portion fixedly connected to the connection member and a second portion fixedly connected to the proximal end of the first extension member. The first coupling may include a moveable joint interposed between the first portion and the second portion. The moveable joint may be a ball and socket joint. 
         [0009]    The positioning device may further include a reference block having first and second attachment mechanisms, the first attachment mechanism including an elongated bore for connecting the reference block to a rigid rod, and the second attachment mechanism being adapted to connect an aortic valve delivery catheter to the reference block. 
         [0010]    The positioning device may further include a second extension member having a proximal end and a distal end; and a second coupling having a first end connected to the distal end of the first extension member and a second end connected to the proximal end of the second extension member. 
         [0011]    Additionally, the positioning device may include a reference element operatively connected between the distal end of the first extension member and the at least one reference datum. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with the features, objects, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which: 
           [0013]      FIG. 1  is a diagrammatic view of a surgical arena, including a representative view of a reference fixture in accordance with certain aspects of the present invention; 
           [0014]      FIG. 2  is a perspective view of a representative reference fixture in accordance with certain aspects of the present invention; 
           [0015]      FIG. 3  is a perspective view of another reference fixture in accordance with certain aspects of the present invention; 
           [0016]      FIG. 4  is an enlarged perspective view of a portion of the reference fixture shown in  FIG. 3 ; 
           [0017]      FIG. 5  is an enlarged perspective view of another portion of the reference fixture shown in  FIG. 3 ; and 
           [0018]      FIG. 6  is a perspective view of a reference block in accordance with certain aspects of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Preferred embodiments of the transapical collapsible valve reference fixture are disclosed below in accordance with the present invention. Where like elements have been depicted in multiple embodiments, like reference numerals have been used in the multiple embodiments for ease of understanding. 
         [0020]    In this description, the terms “reference fixture” and “transapical collapsible valve reference fixture” are utilized interchangeably to refer to the transapical collapsible valve reference fixture of the present invention. The terms “proximal” and “distal” are to be taken as relative to the point at which the reference fixture of the present invention is attached or mounted to a fixed support, such as a table. “Proximal” is to be understood as relatively close to the fixed support when traveling along the length of the reference fixture, and “distal” is to be understood as relatively further away from the fixed support when traveling along the length of the reference fixture. 
         [0021]    Referring to  FIG. 1 , there is depicted a diagrammatical view of a surgical arena A. Within the arena A are a surgical table T and a patient P laying on the table. Attached to the table T is a reference fixture  100  in accordance with one embodiment of the present invention. As shown in  FIG. 1 , and as will be discussed in more detail below, the reference fixture  100  is attached to the table T at one end of the fixture. The reference fixture  100  extends outwardly from its connection with the table T and is positionable over the patient P, such as when the patient is undergoing transapical heart valve replacement. In other embodiments, the reference fixture may be attached to retractors used during the surgical procedure, or to other fixed points in the surgical arena A, rather than to the table T. As also will be discussed, the reference fixture  100  extends over the patient P to create a fixed reference point for the user (e.g., a surgeon or an interventional cardiologist) during the surgical procedure. 
         [0022]      FIG. 2  is a more detailed, perspective view of the representative reference fixture  100  in accordance with certain aspects of the present invention. The reference fixture may include a number of arms, such as first arm  102  and second arm  104 . Reference fixture  100  may have only a single arm, or may have more than two arms as desired. However, two arms are typically sufficient to provide structural stability while still permitting adequate movement and positioning about the surgical arena A. In this embodiment of  FIG. 2 , arms  102  and  104  are joined together by a joint  106  to enable relative movement between the two arms. At the proximal end  108  of arm  102  (and the proximal end of reference fixture  100 ) is a connection member for connecting reference fixture  100  to a fixed support, such as table T. As used herein, the term “fixed support” does not necessarily mean that the support is immovable. Rather, the term “fixed support” is intended to reflect the fact that the support is stable, and will not move unintentionally during the use of reference fixture  100 . Thus, while table T may be moveable when desired, it may be locked in place so as to not move during a valve replacement procedure. The connection member may be a standard two plate clamp  110  having a first plate  142  and a second opposed plate  144  that may be brought together or moved apart by a threaded lever  146 . Clamp  110  may be attached to arm  102  by a joint  112 . 
         [0023]    Rather than clamp  110 , fixation device  100  may utilize any other mechanism for secure attachment to a fixed support. For example, the proximal end  108  of arm  102  may be positioned within an appropriately sized aperture in the support and held in place therein by a tight frictional fit, or by a set screw. Alternatively, the proximal end  108  of arm  102  may fit through an aperture in the fixed support and may be held therein by a pin, nut, spring loaded arms, clamping member, or other securing mechanism. Still further, the proximal end  108  of arm  102  may be configured with a “quick clamp” to slidingly engage a side rail of a surgical table, as will be described more fully below. 
         [0024]    A datum block  116  may be connected to the distal end  114  of arm  104  (and the distal end of reference fixture  100 ). The datum block  116  may be a generally rectangular body with three reference datum  120   a,    120   b,    120   c  extending therefrom, preferably in mutually orthogonal directions. Thus, reference datum  120   a  may extend from one face of datum block  116  in a direction substantially orthogonal to arm  104 ; reference datum  120   b  may extend from another face of reference block  116  in a direction substantially orthogonal to both arm  104  and reference datum  120   a;  and reference datum  120   c  may extend from yet another face of datum block  116  in a direction substantially parallel with arm  104  and orthogonal to both reference datum  120   a  and reference datum  120   b.  Moreover, each pair of reference datum  120   a,    120   b  and  120   c  may be coplanar, with the third reference datum being substantially orthogonal to the plane defined by the other two. In a variant hereof, reference datum  120   a,    120   b,    120   c  may extend directly from arm  104  without the use of a datum block. Each of reference datum  120   a,    120   b  and  120   c  may be in the form of a straight rod projecting outwardly from the rectangular body. 
         [0025]    Reference fixture  100  may include more than three reference datum or less than three reference datum as needed. As few as one reference datum may be adequate. However, three reference datum provide a preferred number of reference lines giving the user a sufficient number of positioning options without unduly interfering in the surgical arena A. 
         [0026]    As stated above, arm  104  may be connected to arm  102  by a joint  106 , and arm  102  may be connected to clamp  110  by a joint  112 . Joints  106  and  112  are intended to provide a maximum amount of maneuverability between the connected elements, and therefore each may be in the form of a ball and socket joint. 
         [0027]    Joint  112  may include a post  122  that is threaded at one end  126  for connecting the post to another object; in the case of joint  112 , to clamp  110 . A knurled knob  124  at an intermediate position on post  122  may help to rotate the post relative to the clamp. Rather than a threaded connection, it is contemplated that post  122  may be securely joined to clamp  110  in other ways generally known in the art. At its opposite end, post  122  includes a ball  128 . The ball  128  represents the “ball” of ball and socket joint  112 . 
         [0028]    The “socket” portion of ball and socket joint  112  is provided at the proximal end  108  of arm  102 . In this regard, the proximal end  108  of arm  102  may be hollow, and may have a somewhat spherical internal shape adapted to complement the shape of ball  128 . Alternatively, the proximal end  108  of arm  102  may be provided with an insert having a somewhat spherical internal shape for mating with the shape of ball  128 . Where arm  102  includes an insert, the insert may be made from a polymer that reduces the friction and wear resulting from the movement of ball  128  relative to arm  102 . 
         [0029]    The proximal end  108  of arm  102  may also be provided with one or more slits or slots  130  extending in the length direction of the arm a short distance from the arm&#39;s free end. Slits or slots  130  split the proximal end  108  of arm  102  and any insert therein into segments that can flex radially outward so that ball  128  may be inserted into the split socket, and may freely rotate therein. The rotation of the ball  128  within the socket at the proximal end  108  of arm  102  enables the arm to be positioned at virtually any desired angle in three-dimensional space. A threaded rod  131   a  having a knob  131   b  on one end thereof may extend through an aperture in a segment of arm  102  on one side of slot  130  (and through the corresponding segment of the polymer insert where present) and threadedly engage a threaded aperture on a segment of arm  102  on the opposite side of slot  130 . By turning threaded rod  131   a  in a tightening direction, the segments of arm  102  on opposite sides of slot  130  (and the corresponding segments of the polymer insert where present) may be drawn closer to one another so that slot  130  narrows and the split socket tightly engages ball  128 . The frictional engagement between ball  128  and the segments of arm  102  on opposite sides of slot  130  (or between ball  128  and the segments of the polymer insert on opposite sides of slot  130 ) prevents the ball from rotating relative to the socket, thereby locking arm  102  in a fixed position relative to clamp  110 . 
         [0030]    Joint  106  has a similar structure to joint  112 . Thus, joint  106  includes a post  132  that is threaded on one end for connection to the distal end  109  of arm  102 . A knurled knob  134  at an intermediate position on post  132  may help to tighten the threaded engagement. The opposite end of post  132  includes a ball  136  that is receivable in a “socket” provided at the proximal end  115  of arm  104 . As with joint  112 , the socket may be formed by the internal shape of the hollow proximal end  115  of arm  104 , or by a polymer insert provided in the hollow proximal end of the arm. One or more slits or slots  138  extending in the length direction of arm  104  from the free proximal end  115  thereof define segments in the proximal end of the arm (and in any insert therein) that can flex radially outward so that ball  136  may be inserted into the split socket and may rotate freely therein. The rotation of the ball  136  within the socket at the proximal end  115  of arm  104  enables the arm to be positioned at virtually any desired angle in three-dimensional space relative to arm  102 . A threaded rod  140   a  having a knob  140   b  at one end thereof may extend through an aperture in a segment of arm  104  on one side of slot  138  (and through the corresponding segment of the polymer insert where present) and threadedly engage a threaded aperture on a segment of arm  104  on the opposite side of slot  138 . Turning threaded rod  140   a  in a tightening direction may draw the segments of arm  104  on opposite sides of slot  138  (and the corresponding segments of the polymer insert where present) closer to one another so that slot  138  narrows and ball  136  is unable to rotate relative to the socket, locking arm  104  in a fixed position relative to arm  102 . Where reference fixture  100  includes one or more additional arms, such arms may be connected in series with arms  102  and  104  using similar “ball and socket” type joints. It will be appreciated that joints  106  and  112 , and any similar joints in reference fixture  100 , may be formed as other types of joints in lieu of “ball and socket” joints, such as hinge joints, screw joints, planar joints and the like. 
         [0031]    While the ends of arms  102  and  104  have been described as forming the socket portion of the ball and socket joint, additional elements may be provided for this purpose. This may be particularly useful in reference fixtures in which the arms  102  and  104  are formed from materials which do not readily flex to receive the ball portion of the joint. Such materials may include, for example, lightweight plastic or carbon fiber. Where such materials are used for arms  102  and  104 , a companion structure, preferably of metal, may attach to each arm  102 ,  104 , such as by threaded engagement, welding, adhesive, force fit, or other types of connection. Such companion structure may include the slits or slots  130 ,  138  and the through aperture and threaded aperture on opposite sides of the slits or slots for receiving threaded rods  131 ,  140 . 
         [0032]    By providing two ball and socket joints, the reference fixture  100  of  FIG. 2  provides a great degree of adjustment for the user. This is true even though the connection between arm  104  and datum block  116  is shown as a simple threaded connection  118 . Rather than a threaded connection, datum block  116  could be connected to arm  104  by a rotatable post joint to enable datum block  116  to rotate about the central longitudinal axis of arm  104 . Such connection could also be a ball and socket joint similar to joints  106  and  112 , or another type of joint, such as an elbow joint, hinge joint, etc. 
         [0033]    A reference fixture  100 ′ utilizing a ball and socket joint in place of the threaded connection  118  is shown in  FIG. 3 . Thus, reference fixture  100 ′ includes three ball and socket joints, a first joint  160  between datum block  116 ′ and arm  104 ′, a second joint  106 ′ between arms  102 ′ and  104 ′, and a third joint  112 ′ between arm  102 ′ and clamp  110 ′. Similar to ball and socket joints  106  and  112  described above, each of joints  160 ,  106 ′ and  112 ′ includes a ball attached to the end of one member that fits within a split socket on the end of an adjacent member, wherein the connection between the ball and socket may be fixed by tightening a threaded fastener. 
         [0034]    It will be appreciated that the sockets in reference fixture  100 ′ are provided by socket connectors  146 ,  148  and  150 , which connect the end of one member to the ball at the end of a next adjacent member. For example, referring to  FIG. 3 , socket connector  146  may be fixedly connected to the proximal end of arm  104 ′, and may provide a split socket for connecting to the ball  136 ′ at the distal end of arm  102 ′. In addition, socket connector  150  may be fixedly connected to datum block  116 ′, and may provide a split socket for connecting to the ball at the distal end of arm  104 ′. 
         [0035]    Datum block  116 ′ includes reference datum  120   a ′,  120   b ′, and  120   c ′ extending therefrom. As previously described, it is preferred that these reference datum extend in mutually orthogonal directions, as depicted by the x, y and z axes in  FIG. 3 . Datum  120   b ′ extends along the x axis; datum  120   a ′ extends along the y axis in a direction that is orthogonal to the x axis and coplanar therewith; and datum  120   c ′ extends along the z axis in a direction that is orthogonal to both the x axis and the y axis. Datum block  116 ′ may include additional reference datum, and/or reference datum  120   a ′,  120   b ′ and  120   c ′ may extend in different directions than those shown, all depending on the needs of the user. 
         [0036]    Referring again to  FIG. 3 , mounted to reference datum  120   c ′ is a reference block  200 , the details of which will be described below. Reference block  200  enables catheter based valve delivery system  202  to be mounted to reference fixture  100 ′. A more detailed view of the connection of valve delivery system  202  to reference fixture  100 ′ is shown in  FIG. 4 . 
         [0037]    As noted above, the reference fixtures of the present invention may be connected to the rail of a surgical table so as to be slidable therealong.  FIG. 5  is a perspective view of a clamp  300  for making such connection. Clamp  300  may be connected to the side rail R of the table T using quick mount rail techniques well known to one of ordinary skill in the art. In that regard, clamp  300  may include a body, the main portion  302  of which confronts the front surface of rail R. A first jaw  304 , integrally formed with the main portion  302 , extends over the top of rail R and into engagement with the back surface of the rail. A second jaw  306 , formed separately from the main portion  302 , extends below the bottom of rail R and into engagement with the back surface of the rail. A threaded rod (not shown) may join jaw  306  to jaw  304 , and a knob  308  at the end of the threaded rod may be used to rotate the threaded rod so as to bring jaw  306  closer to jaw  304 , thereby tightening clamp  300  against the top and bottom surfaces of rail R. A second threaded rod (not shown), threadedly engaged through the main portion  302  of the clamp body, may be rotated by a knob  310  at one end thereof to fix a post  101 ′ at the proximal end of reference fixture  100 ′ to clamp  300 . With reference fixture  100 ′ fixed to clamp  300 , knob  308  may be turned to loosen jaws  304  and  306  from rail R. Clamp  300  may then be slid in either direction along rail R until reference fixture  100 ′ is in a desired position, at which point knob  308  may be turned in an opposite direction to tighten jaws  304  and  306  and fix the clamp to the rail. 
         [0038]      FIG. 6  is a perspective view showing the details of the reference block  200  referred to above. Reference block  200  includes a reference datum slot  202  sized and configured to slidingly engage any one of reference datum  120   a - c ,  120   a ′- c ′. The sliding engagement should be sufficiently loose that reference block  200  may be slid onto and along reference datum  120   a - c ,  120   a ′- c ′, but also sufficiently tight that the reference block will be fixed on the reference datum in a relatively tight relation when the pushing or pulling force is terminated. Reference block  200  also includes an arrangement appropriate for affixing a catheter delivery system thereto. One such arrangement is an aperture  204  extending through reference block  200  in a direction orthogonal to reference datum slot  202 . Aperture  204  may be sized to receive a luer fitting on the proximal end of the catheter delivery system. Although shown as a rounded body, the shape of reference block  200  is not critical, and may be square, rectangular, or any other geometric or non-geometric shape as desired or dictated by the procedure being performed and the apparatus with which the reference fixture is being used. Preferably, reference block  200  and all parts of the reference fixtures described herein are configured from a lightweight plastic or metal that may be sterilized and reused. 
         [0039]    The reference fixtures of the present invention enable a user to precisely position a catheter delivery system, particularly for a prosthetic cardiac valve, for improved surgical performance. Such reference fixtures may be positionable using only a single hand, and are particularly useful in a transapical valve replacement approach. In this regard, certain catheter delivery systems include sheaths that may move relative to one another and relative to the catheter in general. With the present invention, a fixed sheath may be connected to reference block  200 , for example through a female luer fitting, and aligned precisely for valve delivery into the patient. A moveable sheath may thereafter be maneuvered to deploy the prosthetic valve while the reference block and fixed sheath are held in a fixed position relative to the patient. 
         [0040]    In order to use reference fixture  100  or  100 ′ in a surgical procedure, the reference fixture is first attached to the operating table or to another fixed support, such as chest retractors, using clamp  110 , clamp  300  or other suitable clamp. The delivery catheter may then be connected to reference block  200  and the user may position the delivery catheter in an appropriate position and orientation vis-à-vis the native anatomy of the patient. After fine tuning the position and orientation, and making any necessary adjustments, the user may fix the members of the reference fixture relative to one another by turning knobs  131   b  and  140   b  to tighten joints  112  and  106 , respectively, and performing a similar procedure to tighten any other joints of the reference fixture. The user may then perform the valve replacement procedure using the fixed reference to hold the catheter&#39;s position during deployment of the prosthetic valve. 
         [0041]    Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. 
         [0042]    It will be appreciated that the various dependent claims and the features set forth therein can be combined in different ways than presented in the initial claims. It will also be appreciated that the features described in connection with individual embodiments may be shared with others of the described embodiments.