Patent Publication Number: US-2021177389-A1

Title: Guidewireless Transseptal Delivery System and Method

Description:
This application is a continuation of U.S. application Ser. No. 16/396,677, filed Apr. 27, 2019, which is a continuation of PCT/US2017/62913, filed Nov. 22, 2017, which claims the benefit of the following US Provisional Applications: U.S. 62/425,584, filed Nov. 22, 2016, U.S. 62/443,492, filed Jan. 6, 2017, U.S. 62/461,788, filed Feb. 21, 2017, and U.S. 62/473495, filed Mar. 20, 2017. 
    
    
     BACKGROUND 
     Considerable attention has been directed towards attempting to replace or repair mitral valves using transvascular techniques. More than  40  such novel mitral valve therapeutic devices (MVTDs) that are intended to be delivered using transvascular interventional techniques have been described at this time. Many MVTDs are delivery devices for use in delivering a mitral valve prosthesis. In order for these devices to be considered minimally invasive, interventional cardiology based procedures, they must cross from the right side of the heart to the left side across the inter-atrial septum in a well-established technique known as transseptal catheterization. Because of the size and odd shape of the mitral valve carried by the replacement MVTDs, this route has proven to be extremely difficult. 
     All current transseptal mitral valve delivery systems rely on the traditional interventional approach that requires that these large devices be pushed over a 0.035 in. guidewire that has been previously introduced across the interatrial septum, through the left atrium then across the mitral valve and into the left ventricle. This guidewire, used in all currently available transseptal interventional devices, provides a “rail” over which these large devices can potentially be forced into position. Unfortunately, the MVTDs generally are simply too big and too rigid to negotiate the tight bends that are required when crossing into and navigating through the left atrium. As a result, they can become “stuck” when attempting to negotiate the multiple turns required for positioning within the mitral valve ring. In some instances, physicians have attempted to force these devices over the guidewire, while using the wire and the device itself to deflect off of delicate cardiac tissues, in order to achieve proper positioning within the mitral valve ring. This use of force is best avoided to prevent damage to the cardiac tissue. 
     In the embodiments described in this application, guidewires are not utilized to drive movement of the MVTDs into their target position for treatment (e.g. repair or replacement) of the mitral valve. Instead, protected, coordinated and synergistic forces are used to safely position the MVTDs into place. These forces include a pulling force, a pushing force, and a steering force helping to safely advance the MVTD through the vasculature into position and properly orient it relative to the mitral valve. 
     Attempts have been made to facilitate guidewire delivery of MVTS&#39;s by using commercially available “snare devices” delivered retrograde from the aorta through the left ventricle and left atrium in an unprotected fashion to help direct the tips of the delivery systems. These efforts were abandoned when it was found that pulling on the MVTD with a snare resulted in pulling the snare with great force up (superiorly) and across both the aortic and mitral valve leaflets leading to simultaneous wide open insufficiency of both valves and loss of blood pressure in the patient. The disclosed system eliminates this problem, allowing maximum application of force to deliver any mitral therapeutic device safely into precise position within the mitral valve ring. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a side elevation view of a Right-to-Left conduit (“RLC”) assembled with a Brockenbrough needle and dilator. 
         FIG. 1B  is a side elevation view of the RLC of  FIG. 1A  assembled with a tracker balloon catheter. 
         FIG. 1C  is a side elevation view of the RLC of  FIG. 1A  assembled with a Left Ventricle Redirector (“LVR”). 
         FIG. 2A  is a side elevation view of the LVR with the distal end in the curved position to deploy the protective panel. 
         FIG. 2B  is a side elevation view of the LVR with the distal end in the straight position. 
         FIG. 2C  is a cross-section view of the shaft of the LVR taken along the plane designated  2 C- 2 C in  FIG. 2B . 
         FIG. 3A  is an elevation view of the cable. 
         FIG. 3B  is an elevation view of the tensioner. 
         FIG. 3C  shows an assembly of the cable, tensioner, MVTD and a cable lock. 
         FIG. 4A  schematically illustrates a section of the heart and shows the step of transseptal catheterization from the right atrium into the left atrium, using a Brockenbrough needle assembly through the RLC. 
         FIG. 4B  is a similar view to  FIG. 4A  and shows the balloon catheter deployed within the left atrium; 
         FIGS. 5A-5C  are schematic illustrations of the heart depicting the left atrium, the tracker balloon being carried by the flow of blood from the left atrium, into and through the aorta, to the femoral artery. 
         FIG. 6A  shows the snaring of the ball tip of the cable in the left femoral artery after the cable been passed through the RLC; 
         FIG. 6B  illustrates the step of advancing the LVR over the cable and the locking of the LVR to the cable; 
         FIG. 6C  illustrates the advancement of the LVR over the RLC; 
         FIG. 7  shows the LVR in the expanded configuration within the left ventricle after removal of the RLC; 
         FIGS. 8A and 8B  show the MVTD delivery system and tensioner on the cable being drawn by the cable across the interatrial septum towards the mitral valve ring. 
         FIG. 9A  shows the MVTD delivery system positioned at the mitral valve as the MVTD is being centered within the valve. 
         FIG. 9B  shows the mitral valve in place at the mitral valve ring MVTD following deployment from the MVTD. 
     
    
    
     DETAILED DESCRIPTION 
     The presently disclosed system is designed to aid in the delivery of a MVTD to a mitral valve location. The terms “mitral valve therapeutic device” or “MVTD” used here refer to any device that may be delivered to the native mitral valve site for a therapeutic purpose. In the description that follows, the MVTD is shown as a mitral valve delivery system carrying a replacement mitral valve, but it should be understood that the system and method described may be used to deliver other types of MVTD&#39;s such as those used to repair a mitral valve. 
     The disclosed system and method replaces the traditional interventional guidewire approach used for MVTD delivery with a percutaneous system that allows the MVTD to be safely towed to the mitral valve site within the heart. Although the system can easily be attached to any existing MVTD via the intrinsic 0.035 in. lumen present in all such interventional devices, it eliminates the need for a guidewire with the MVTD. 
     As will be appreciated from a review of the more detailed discussion that follows, the cable system functions to both push the proximal end of the MVTD while simultaneously pulling on the distal nose of it with equal and coordinated force to drive the MVTD across the interatrial septum. Pulling down further on the distal nose of the MVTD using the cable provides a steering force that serves to direct the stiff, bulky MVTD into position across the interatrial septum, into the left atrium and into position for deployment in the mitral valve ring (located below the interatrial septal entry point and to the patient&#39;s left). The MVTD is further positioned precisely in the center at an angle that is perpendicular to the MV plane by use of a steering mechanism present in a unique device referred to as the LV redirector (described in detail below). In some embodiments, an electronic drive unit may be used to deliver precisely coordinated pushing and pulling forces. 
     In the description of system and method below, the access points for the components of the system are described as the right femoral vein for the venous access and the left femoral artery for the arterial access. However, the system and method can just as readily be used with a different combination of venous and arterial access. For example, venous access may be gained via the right femoral vein and arterial access may be gained via the right femoral artery. Alternatively, both access points may be on the left side. In yet another embodiment, venous access is gained via the left femoral vein and arterial access is gained via the right femoral artery. 
     System 
     Referring to  FIG. 1A , the system includes a Right-to-Left conduit  10  (“RLC”), an elongate tubular catheter having a length sufficient to permit it to extend from the right femoral vein of a human adult to the right atrium, across the interatrial septum to the left atrium, through the aorta and into the femoral artery on the patient&#39;s left or right side. The RLC  10  includes a distal portion shape set into a curved configuration to help orient the needle used for transseptal puncture towards the interatrial septum. In alternative embodiments the RLC may be steerable using pullwires or alternative means. The durometer of the RLC is relatively low (eg 55 D) as known in the art for cardiovascular catheters so as to minimize tissue trauma, although a significant length on the proximal part of the catheter is formed of a higher durometer (e.g. 70 D) to give the conduit sufficient column strength to avoid buckling when used to push during advancement of the LVR as described below. This higher durometer section may be the part of the conduit that, when the conduit fully extends between the right femoral vein and right or left femoral artery, begins at or near the proximal end of the conduit and terminates within the inferior vena, and may be as much as a third of the length of the RLC. In  FIG. 1A , the RLC  10  is shown assembled with a Brockenbrough needle assembly  12  and dilator  14  for use in the transeptal catheterization step of the method. 
     The system further includes a tracker balloon catheter  16 , shown extending through the RLC  10  in  FIG. 1B , comprising an inflatable balloon on the distal end of the catheter. The balloon catheter  16  includes a guidewire lumen. The balloon may be inflated with a fluid or gas, including CO2 or saline, or it may be a self-expanding “vacuum balloon.” 
     In  FIG. 1C , the RLC  10  is shown assembled with a conveyor cable  18  and a left ventricle redirector or “LVR”  26 . Details of the LVR can be seen in  FIGS. 2A-2C . The LVR includes an elongate catheter shaft  28  having a proximal handle  32  with a luer port  40 . As shown in the cross-section view of  FIG. 2C . The shaft includes a lumen  29  accessible via the port  40 . This lumen extends to the distal tip of the shaft. Incorporated within the wall of the LVR shaft are a pullwire  26  and a return wire  38 . The pullwire exits the sidewall of the shaft  28  near the shaft&#39;s distal end, runs along the exterior of the shaft, and is affixed to the distal end of the shaft. Increasing tension on the pullwire  26  pulls the distal end of the shaft into a curve as shown in  FIG. 2A . The handle  32  includes actuators to actuate the pull wire to bend the shaft and to actuate the return wire to return the distal end of the shaft to the generally straight configuration (as in  FIG. 2B ). The return wire  38  may have a rectangular diameter as shown, with the long edges oriented to aid in preferential bending of the catheter. 
     A membrane  30  is positioned along a portion of the distal part of the shaft and along the external portion of the pullwire  26 . When the pullwire is relaxed and the shaft is in the straight configuration, the panel and pull wire run along the distal part of the shaft. The membrane forms the D-shaped barrier shown in  FIG. 2A  when the distal end is drawn into the curved configuration by action of the pullwire. The barrier forms a protective panel extending between the external part of the pullwire and the shaft  28 , substantially eliminating gaps between the two. The panel may be made of an elastomeric polymer or other material. 
     Note that the term “pullwire” is not intended to mean that the pullwires must be formed of wire, as that term is used more broadly in this application to represent any sort of tendon, cable, or other elongate element the tension on which may be adjusted to change the shape of the LVR or other catheter in which the pullwire is used. 
     The conveyor cable  18 , shown in  FIG. 3A  comprises an elongate cable having distal cable section  17   a  having a broadened distal tip  20  such as the ball tip feature shown in the drawings. The tip  20  may include a distal face having convex curvature and a cylindrical proximal part with a generally flat proximal face to facilitate engagement using a snare. A larger diameter intermediate section  17   b  is proximal to the distal section  17   a  and includes a polymer coating. A proximal section  19  comprises a stiff mandrel proximal to the intermediate section  17   a.  The proximal section is sufficiently stiff to give column support for pushing of the cable during the RLC removal discussed below. A radiopaque marker band  21  is positioned between the proximal mandrel section  19  and the intermediate section  17   b.  When the cable  18  is assembled with the segmental tensioner  22  (discussed below), the soft distal tip of the segmental tensioner mates with the marker band  21 , allowing the user to see on the fluoroscopic image the transition between the segmental tensioner and the intermediate (coated) section  17   b  of the cable. 
     Segmental tensioner  22 , shown in  FIG. 3B , is a short length (e.g. 30-35 mm) tubular component having a flexible tip section (e.g. 40 D) and a more rigid (e.g. 70 D) proximal hub section of broader diameter. The inner diameter of the hub section is proportioned to receive the distal tip of the MVTD. The segmental tensioner incorporates a deadstop within the shaft inner diameter to engage the polymer coated intermediate section  17   b  of the conveyor cable and to lock the MVTD  46  in position, preventing it from advancing independently of the conveyor cable as it is moved towards the mitral valve. 
     Method of Use 
     As an initial step, the RLC  10  is introduced using the well-known technique of transseptal catheterization from the right atrium (RA) into the left atrium (LA), such as by using a Brockenbrough needle assembly  12 ,  14  through the RLC  10 , which is positioned in the right femoral vein (RFV) as shown in  FIG. 4A . Once the distal end of the RLC  10  is disposed in the left atrium, the needle is withdrawn and the tracker balloon catheter  16  is passed through the RLC into the left atrium. The balloon may have a concave proximal face to increase the surface area of the balloon in the upstream direction. Once deployed within the left atrium, the flow of blood carries the tracker balloon into and through the aorta to the femoral artery as shown in  FIG. 5B . As discussed previously, this description describes left side access to the arterial vasculature, but in alternative methods the tracker balloon catheter  16  may be diverted to the right femoral artery (RFA). The RLC is the advanced over the tracker balloon catheter  16  towards the left or right femoral artery. See  FIG. 5C . 
     The tracker balloon catheter is withdrawn from the RLC, and the conveyor cable  18  is inserted into the RLC  10  on the patient&#39;s right ride and advanced. This directs the tip of the cable  18  into the left femoral artery. A snare introduced into the left femoral artery grasps the ball tip  20  of the conveyor cable as shown in  FIG. 6A . 
     Referring to  FIG. 6B , the left ventricle redirector (LVR)  26  is introduced over the cable. The lumen of the LVR slides over the ball tip and shaft of the cable  18 . The LVR is pushed towards the RLC while the RLC is pushed towards the LVR, causing the LVR to advance its distal end over the exterior surface of the RLC  10 . This eliminates the exposed section of cable  18  between the LVR and RLC, and because the conveyor cable is much more flexible than the LVR or RLC, this step removes flexibility from the assembly now extending through the vasculature and heart. A cable lock  44  is used to lock the proximal end of the LVR onto the conveyor cable outside the access point to the femoral artery so that the LVR and cable will move together. The user pulls on the cable  18  on the patient&#39;s venous side (in  FIG. 6B , the patient&#39;s right which is the left side of  FIG. 6B ). On the patient&#39;s arterial side (in  FIG. 6B , the patient&#39;s left which is the right side of  FIG. 6B ), the user pushes the LVR  26 . Note that since the LVR is locked to the conveyor cable  18 , the actions of pulling the cable  18  and pushing the LVR advance the LVR into the aorta. If the system is configured such that the LVR slides over the RLC, this step is accompanied by the pushing on the RLC  10  from the venous side. Pushing the RLC during advancement of the LVR pushes the loop of the RLC into the apex of the RV as indicated by the arrow in  FIG. 6B , keeping it away from delicate valve structures and chordae tendineae. If the RLC is not advanced, it may be withdrawn towards the venous access location as the LVR is advanced towards the left ventricle. 
     Once within the heart, the LVR is pushed strongly into the apex of the left ventricle by a pushing force applied to its proximal end. 
     The RLC is next withdrawn from the venous side while a pushing force is applied to the cable on that same side.  FIG. 7  shows the configuration after the RLC has been removed and the protective panel of the LVR has been deployed in the left ventricle via activation of the pullwire. The cable  18  is still in place as shown. The segmental tensioner  22  is positioned over the cable  18 , followed by the MVTD, with the distal tip of the MVTD being inserted into the hub of the segmental tensioner. A cable lock  48  locks the MVTD and segmented tensioner  22  assembly onto the cable  18 . The cable lock  44  locking the LVR to the cable  18  is removed. 
     In  FIG. 8B , the MVTD  46  has entered the venous circulation and is advancing toward the right atrium, led by the segmental tensioner  22 , as the system is pulled by the cable while the MVTD is simultaneously pushed along at the same rate in a coordinated manner. The segmental tensioner  22  leads the way as it crosses the interatrial septum and provides a gradual transition to the bigger and stiffer MVTD ( FIG. 8A ). 
     At this point, a significant pulling force is applied to the MVTD/tensioner assembly by the cable  18 . This force is slightly more than the “push force” force on the MVTD  46  so as to pull the distal nose of the MVTD down and to the patient&#39;s left through the interatrial septum. Despite the pushing force of the LVR into the apex, with ever increasing pull force, there is a strong tendency to cause the loop of the cable contained in the steerable section of the LVR to be pulled upward into the valve structures above. This tendency is overcome by the synergistic downward pushing force exerted by the segmental tensioner as it enters the lumen at the distal end of the LVR in the LV apex ( FIG. 8B ). It ensures that the cable  18  is positioned away from the aortic and mitral valve leaflets and chordae tendineae by maintaining the cable  18  safely away from the valve structures within the LVR&#39;s protective sleeve. 
     In addition to the importance of maintaining the cable  18  loop in the apex of the ventricle, another key function of the LVR is to aid in the final steering of the MVTD into the center of the mitral valve ring at an angle that is perpendicular to the mitral valve ring plane. The user fine tunes the MVTD position within the ring through a combination of adjustments to pull wire tension, torqueing of the LVR, and push-pull of the LVR from the handle. 
       FIG. 9A  shows the MVTD delivery system in place and centered in the mitral valve ring. After deployment of the mitral valve from the mitral valve delivery device, the arterial side of the cable is disconnected and withdrawn through the LVR as the mitral valve delivery device is withdrawn out of the body through the venous sheath. Finally, the LVR is withdrawn from the arterial sheath and the replacement valve alone remains in place ( FIG. 9B ). 
     It can be appreciated that an automated alternative to the manual method and system described above is conceivable and within the scope of this disclosure. Such a system would include drive elements that engage and selectively push/pull the instruments at the venous side, and drive elements that engage and selectively push/pull the instrument at the arterial side. In such an embodiment, the MVTD and cable are attached to a drive unit (which may be table mounted) after connection of the MVTD and deployment of the LVR, just before the MVTD is set to enter the venous sheath. The drive unit may be one configured to allow the cable  18  to be set between rollers that will cause a pulling force to be applied to the cable at the arterial side while the delivery sheath of the MVTD is set among the rollers at the that will cause the MVTD to be pushed forward at the venous side at the same rate, causing the MVTD to move toward the mitral valve position. Such a system might employ a wired or wireless user controller. The controller can include a first input (e.g. a button, slider, etc) used to selectively cause movement (pulling or pushing force) at the arterial side and a second input used to selectively cause equal pulling and pushing forces at the venous side in a reverse direction. The controller preferably includes “dead man” switches, so that all motion stops instantly if either button is released. (The controller might also include a single input or mode of operation that causes the drive unit to simultaneously pull the cable and push the MVTD at the same rate.) A third input is used to cause an increased rate of movement in the pull direction to be greater than the rate of movement in the pull direction in order to steer the tip of the MVTD down and to the patient&#39;s left when traversing the interatrial septum and left atrium. A fourth input can be employed to cause more push than pulling force in order to drive the segmental tensioner harder into the protective sleeve of the steering section of the LVR in order to keep it pushed into the LV apex during increased tension on the cable during transit of the MVTD. 
     The disclosed system and method are described here as “guidewireless” because the step of moving the MVTD into position across the mitral valve site is performed without guidewires. Note that other steps may utilize guidewires without departing from the scope of the invention. As a non-limiting example, should the practitioner observe the tracker catheter heading off course as it approaches the aorta, a guidewire may be introduced via the arterial side into the distal lumen opening at the balloon catheter tip so that the tracker balloon catheter can track over the guidewire to the target vessel in the arterial vasculature 
     All patents and patent applications referred to herein, including for purposes of priority, are fully incorporated herein by reference.