Patent Publication Number: US-2020298009-A1

Title: Lead Delivery for His-Bundle Pacing

Description:
RELATED APPLICATION 
     This application claims priority to U.S. patent application Ser. No. 15/267,195, filed Sep. 16, 2016, which is incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     Embodiments of this disclosure relate to catheters and treatment methods using such catheters to deliver a pacing lead to the bundle of His by way of right side access to the heart through the right subclavian vein. 
     BACKGROUND 
     Guiding catheters are well known devices used to locate and cannulate vessels for a variety of medical procedures. They are of particular use in cardiac access procedures such as those involved in the implantation of cardiac pacing leads. Cardiac pacing leads are flexible, and historically, stylets have been inserted into the lumen of hollow leads to stiffen and allow the lead to be bent to aid in lead placement. Stylets are still in common use but are inadequate to provide precise control to reach and place a lead at the small target His bundle. Typically, when right side approach is desired it involves accessing the heart via the left subclavian vein, the cephalic vein and more rarely the internal or external jugular vein, or femoral vein. For catheter lead placement, a guide wire is advanced into the heat from the access site. The guiding catheter is then advanced through the vasculature and into the heart over the guidewire; once in position the guidewire is removed. A pacing lead is then advanced through the guiding catheter to be deployed at various regions in the heart. 
     Typically, pacing leads are deployed to various locations in the heart depending on the nature of the heart condition necessitating the pacing procedure. Conventional ventricular pacing typically involves implanting a lead at the apex of the right ventricle. This placement is still often utilized today even in the face of published evidence of the deleterious effects of bypassing the His/Purkinje system, otherwise known as the cardiac conduction system. 
     Pacemaker lead electrodes have been placed in or on the heart in a position that bypasses the His/Purkinje system since the inception of pacing in 1957. Directly stimulating the myocardium is and has been the standard of care even though His bundle pacing has been known and tried occasionally. It is believed that His bundle pacing is not widely practiced because it presents a small target and is very hard to reach successfully. This increases “fluro time” which is a detriment to both patient and physician. Another factor is that there is no wide recognition of the value of His pacing. At present there is a paucity of catheters that can facilitate His bundle pacing. When, for various reasons, the pacemaker must be implanted on the patient&#39;s right side and right subclavian vein used to reach the heart the target is still the myocardium and not the His bundle. It should be noted for completeness that the His bundle is accessed on the atrial aspect of the annulus of the tricuspid valve, just above the attachment of the septal valve leaflet. 
     The present disclosure describes embodiments of a catheter and method for its use in delivering a pacing lead to the His bundle at the septal wall. The cardiac conduction system is comprised in part of His bundle which resides between the atrioventricular (AV) node, and the bifurcation of left bundle branch (LBB) and right bundle branch (RBB). This anatomic location is regarded as a difficult target to reach. Embodiments of the present invention have overcome this difficulty. 
     SUMMARY 
     Embodiments of the present disclosure are directed to a unique guiding catheter configuration which allows for the precise delivery of pacing leads to the septal wall of the right atrium, above the anterior tricuspid valve septal leaflet, in proximity to the His bundle and from a right side approach to the heart. The catheter interacts with the anatomy to allow both precise and quick access to the His bundle as it presents in the right heart. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional illustration of a human heart depicting the anatomy of the heart and its electrical system. 
         FIG. 2  is a cross-sectional illustration of a human heart wherein an embodiment of a guide catheter is shown advanced to a target site within the central fibrous body, between the tricuspid valve and the aortic valve and corresponding to the bundle of his. 
         FIG. 3  is an anatomical illustration of a patient and the manner in which the embodiment shown in  FIG. 2  initially accesses the vasculature prior to advancement into the heart. 
         FIG. 4  is a detailed view of the distal region and tip of the catheter shown in  FIGS. 2 and 3  at the target site. 
         FIG. 5  is a perspective view of the catheter embodiment shown in  FIGS. 2-4  in its preformed or default shape prior to insertion into a patient. 
         FIG. 6  is a side view of the catheter embodiment shown in  FIG. 5  illustrating the angle of the distal tip relative to the plane defined by the proximal region of the catheter. 
         FIG. 7  is a cross-sectional view of the catheter embodiment shown in  FIGS. 5-6 . 
         FIG. 8  is a side perspective view of an alternative embodiment of the catheter shown in  FIG. 5  having a pre-formed bend in the proximal region of the catheter shaft. 
     
    
    
     DETAILED DESCRIPTION 
     For contextual understanding, of how embodiments of the disclosure are intended to function,  FIG. 1  is included to illustrate the structure of a typical human heart  1  with relevant anatomical features shown. As mentioned, one embodiment of the disclosure is directed to a method for deploying an electrical lead to the His bundle  2  at a target site  10  along the septum  3  distal to the atrioventricular (AV) node  4 , but proximal to the left branch bundle (LBB)  5  and the right branch bundle (RBB)  6 . Such a target site  10  for proper deployment of a pacing lead, is depicted in  FIG. 1  at the crest of the ventricular septum  3  on the atrial aspect of the annulus of the tricuspid valve septal leaflet  7  within the right atrium  8 . The remaining  FIGS. 2-7  depict embodiments of a catheter suitable for accessing the heart and reaching the target site  10  and the manner in which such a catheter is used. 
     An example of a catheter  20  suitable for use in reaching the target site  10  from the subclavian vein is illustrated in  FIGS. 2-7 . 
       FIG. 2  is the schematic diagram of  FIG. 1  in which a distal portion or end region  22  of delivery catheter  20  is shown extending into the right atrium  8  of the heart  1 , from the superior vena cava  9  and the right subclavian vein  11 , with the distal tip  24  positioned at the target site  10 . 
     According to one method, an operator/physician positions guide wire  50  into the heart  1 , for example via a “sub-clavian stick” or central venous access procedure such as is illustrated in  FIG. 3 . Accordingly, the catheter  20  is passed over the guide wire and-advanced into the superior vena cava  9  from the right subclavian vein  11  and into the right atrium  8  such as is in the manner shown in  FIG. 2 . A wall  12  of the superior vena cava  9  provides back-up support for distal portion  22  as the operator maneuvers tip  24  into a proper substantially perpendicular orientation with the septum  3  at the target site  10 , such as in the manner shown in  FIG. 4 . 
     In  FIG. 4 , a close up view of the distal tip  24  is shown following advancement of medical electrical lead  30  though a lumen  26  of the catheter  20  to the target site  10 . The lead  30  is extended distally from distal tip  24  and implanted into the septum  3  by clockwise rotation of the lead body to provide pacing to the heart  1  via the bundle of his  2 . 
     As is shown in  FIG. 2 , the wall  12  of the superior vena cava  9  acts to provide a stabilizing surface or brace for distal portion  22  so as to direct and force the shaft  28  of the catheter  20  into the right atrium  8  from the subclavian vein  11 . Wall  12  forces a specialized zone of the catheter  20  to bend with the shape of the superior vena cava  9 . Because the default or at rest shape of the catheter  20  included a unique shape for aligning the distal tip  24  with the target site  10  (discussed in greater detail below), a guidewire  50  may be advanced through the lumen  26  to aid in tracking the catheter  20  through the confines of the vessel anatomy. Once the distal region  22  of the catheter  20  is within the right atrium  8  the guidewire  50  is removed. 
     The bracing affect provided by the vessel wall  12  imbues the proximal region  23  of the catheter  20  with a proximal bend  25 . This bend  25  cooperates with the unique shape of the distal region  22  such that once the catheter  20  is advanced from the subclavian vein  11 , and through the superior vena cava  9  and into the right atrium  8  the catheter tip  24  is automatically positioned to be perpendicularly oriented with the septum  3  wall in the area of the target site  10  such as in the manner shown in  FIG. 4 . 
     As indicated, the shape if the catheter  20  is unique. The catheter  20 , such as is shown in  FIGS. 5-7  is an elongate shaft  28 , which defines a central lumen  26  extending along its length, and having a substantially straight proximal region (“straight” meaning without bend, or having a curve of essentially infinite radius)  23  and a curved distal region  22 . The distal region  22  is of specialized shape and construction wherein a specific shape and curve is provided to the distal region  22 . As described above, this pre-formed shape cooperates with surrounding venous and heart anatomy, to ensure proper orientation and positioning of the distal tip  24  at the target site  10  when the catheter  20  is advanced into the right atrium  8  such as by the right side access procedure shown in  FIGS. 2 and 3 . It should also be noted that in some embodiments, the catheter  20  such as is shown in  FIGS. 5-7  may also be suitable for use in a left side access electrode implantation procedure such as is described in U.S. Pat. No. 8,606,369, issued on Dec. 10, 2013, the entire contents of which is incorporated herein by reference. 
     The particular shape of the distal region  22 , is illustrated in  FIG. 5  wherein it may be seen that the catheter  20  in an “at rest” state (prior to use) has a substantially straight proximal region  23  and a distal region  22  forming a semi-circular hook or J-shape. The shape of the distal region  22  defines a centerline radius a of approximately 180 degrees with a radius (indicated by line  40 ) of approximately 0.3-0.6 inches, as measured from the axis  44  of the catheter  20 . In at least one embodiment the radius  40  is 0.4 inches. In at least one embodiment radius  40  is 0.5 inches. 
     In addition, and as is shown in  FIG. 6 , the distal tip  24  forms the half turn of a left-hand helix having a pitch  47  of zero inches to about 0.4 inches as measured from the distal tip  24  to the plane  46  defined by the surface of the proximal region  23  in the at rest state and adjacent to the distal region  22 . In at least one embodiment the pitch  46  is 0.3 inches. 
     In an alternative embodiment to that in  FIGS. 5-6 , catheter  20  is provided with a proximal bend  25  when in the pre-insertion or default formed state. The embodiment shown in  FIG. 8  is distinct from that shown in  FIG. 5 , as the embodiment shown in  FIG. 5  requires the anatomy of the superior vena cava  9  and associated anatomy to imbue the proximal region  23  of the catheter  20  with the bend  25 , whereas in the embodiment shown in  FIG. 8  the proximal region  23  of the catheter  25  is formed with a bend  25 , and which is apparent even in the pre-insertion state shown. 
     The particular characteristic of the bend  25 , is that it has a radius  48  of approximately 2.0 inches to 4.0 inches, along a length  49  of the proximal region  23  of approximately 2.0 inches to 4.0 inches as well. In at least one embodiment, the radius  48  is approximately 3.0 inches and the length  49  is also approximately 3.0 inches. The bend  25  begins at a point approximately 3.0 inches to 4.0 inches distally from the distal region  22 ; that is to say, a substantially straight portion  45  of the proximal region  23  extends 3.0 to 4.0 inches between the distal end of the bend  25  and the distal region  22  of the catheter  20 . In at least one embodiment the length of the substantially straight portion  45  is approximately 3.5 inches. 
     In the embodiment shown in  FIG. 8  the pitch  47  of the distal tip  24 , may be the same as that in other embodiments and range from zero to about 0.4 inches; and in at least one embodiment is 0.3 inches. The depiction of this pitch  47  is identical to that shown in the embodiment of  FIGS. 5-6 . 
     In the embodiment shown in  FIG. 8  the bend  25  provides a shape that encourages the catheter  20  to advance through and around the anatomy of the right subclavian vein and superior vena cava with less resistance and ease of advancement in some anatomies. The preformed bend  25  also encourages perpendicular alignment of the distal tip  24  with the target site  10  as described above (and below) and shown in  FIG. 4 . 
     For purposes of describing the shape of the catheter  20 , here the terms “approximately” and “substantially” are used to take into account minor machine and formation tolerances. When the values mentioned above are measured with normal instruments readily available to one of ordinary skill in the art such as a protractor or ruler the describe values will be accurate. 
     The particular combination of the curvature of the distal region  22  and the out of plane angle of the distal tip  24  enables the catheter  20  to form a perpendicular angle γ with the septum  3  such as in the manner shown in  FIG. 4 . The ability of the catheter  20  to form a perpendicular angle relative to the septum  3  provides an idealized approach angle for the implantation of the electrical lead  30 , which makes it easier for the helical screw of the lead  30  to bite into the tough endocardial membrane of the septum  3  and more easily seat therein. Once the lead  30  is properly implanted into the septum  3  at the target site  10 , the catheter is removed. 
     By more accurately positioning the lead  30  at the target site  10 , and more readily penetrating into the septum  3 , the catheter  20  provides for a safer procedure and a total implant procedure time and fluoroscopy time that is feasible and acceptable to pacemaker implanters. In addition, by positioning the lead  30  in the manner described the lead is more effectively seated within septum to more efficiently pace the bundle of his. Published studies find a mean pacing capture thresholds that is one volt lower than the mean threshold of 2.5 volts that is reported using prior catheters, those not capable of perpendicular electrode placement. 
     The many features and advantages of the invention are apparent from the above description. Numerous modifications and variations will readily occur to those skilled in the art. Since such modifications are possible, the invention is not to be limited to the exact construction and operation illustrated and described. Rather, the present invention should be limited only by the following claims.