Patent Publication Number: US-8532733-B2

Title: Mapping guidelet

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part to application Ser. No. 11/555,004 filed on Oct. 31, 2006 now abandoned, the disclosure of which is incorporated in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to medical devices and, more particularly, to delivery of implantable medical device leads. 
     BACKGROUND 
     Most commercially available cardiac pacing and defibrillation leads are placed by means of a stylet which is inserted into a central lumen through the lead, and is used to assist in pushing the lead through the vascular system and guiding it to a desired location. A guidewire, possessing a smaller diameter than a stylet, may also be used to place a lead. Guidewires extend entirely through the lead and out its distal end. The approach of using a guidewire to place cardiac pacing leads and cardioversion leads is disclosed in U.S. Pat. No. 5,003,990 issued to Osypka, U.S. Pat. No. 5,755,765 issued to Hyde et al, U.S. Pat. No. 5,381,790 issued to Kenasaka and U.S. Pat. No. 5,304,218 issued to Alferness. 
     Lead placement into the left heart is difficult since the veins are very small. Consequently, a stylet is initially used to get the lead down to the right atrium and locate the left coronary vein returning from the left outer area of the heart. From that point, a stylet is considered too big to enter the small left ventricle veins. The guidewire is then used for final placement of the lead in the small left ventricle veins. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Aspects and features of the present invention will be appreciated as the same becomes better understood by reference to the following detailed description of the embodiments of the invention when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  is a block diagram of an implantable medical device; 
         FIG. 2  is a plan view of a delivery device used in a medical lead; 
         FIG. 3  is a cross-sectional view of a delivery device of  FIG. 2 ; 
         FIG. 4  is an enlarged view of a proximal joint of the delivery device depicted in  FIG. 3 ; 
         FIG. 5  is an enlarged view of a distal joint of the delivery device depicted in  FIG. 3 ; 
         FIG. 6  is an enlarged view of a tip joint of the delivery device depicted in  FIG. 3 ; 
         FIG. 7A  is a plan view of a mapping guidelet that electronically maps potential sites to position the lead; 
         FIG. 7B  is a plan view of another embodiment of a mapping guidelet configured to map potential sites to position the lead; 
         FIG. 7C  is a plan view of another embodiment of a mapping guidelet configured to map potential sites to position the lead through bi-polar sensing; 
         FIG. 8A  depicts a plan view of a delivery device controller in an unlocked position; 
         FIG. 8B  depicts a plan view of a delivery device controller in a locked position; 
         FIG. 9  depicts a plan view of a proximal end of a delivery device controller; 
         FIG. 10  is a flow diagram related to manufacture of medical electrical lead; 
         FIG. 11A  depicts a plan view of a conductive element used to form a spring; 
         FIG. 11B  depicts a cross-sectional view of the conductive element shown in  FIG. 11A . 
     
    
    
     DETAILED DESCRIPTION 
     The following description of embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers are used in the drawings to identify similar elements. 
     The present invention is directed to a delivery device that eases placement of a medical lead in the heart (e.g. coronary vein, left heart etc.) of a patient. Additionally, a lower manufacturing cost exists to produce the delivery device. For example, a single delivery device replaces both a guidewire and a stylet to place a lead in the left heart. 
     The delivery device is a hybrid of a guidewire and a stylet. The medical lead delivery device includes an elongated body, a controller, a first and second spring, and a sleeve. The elongated body includes a proximal end and a distal end. The controller is disposed at the proximal end and provides enhanced control of the distal tip of the elongated body. In particular, the delivery device can be advanced beyond the tip of the lead to provide a “rail” for the medical lead to track. The first and second springs are coupled to the distal end of the elongated body. A sleeve is coupled to the elongated body and to the first and second springs through first, second and third solder elements. The delivery device is able to place a lead in the small left ventricle vein(s) without using both a guidewire and a stylet. 
       FIG. 1  depicts a medical device system  100 . A medical device system  100  includes a medical device housing  102  having a connector module  104  that electrically couples various internal electrical components of medical device housing  102  to a proximal end  105  of a medical lead  106 . A medical device system  100  may comprise any of a wide variety of medical devices that include one or more medical lead(s)  106  and circuitry coupled to the medical lead(s)  106 . An exemplary medical device system  100  may take the form of an implantable cardiac pacemaker, an implantable cardioverter, an implantable defibrillator, an implantable cardiac pacemaker-cardioverter-defibrillator (PCD), a neurostimulator, or a muscle stimulator. Medical device system  100  may deliver, for example, pacing, cardioversion or defibrillation pulses to a patient via electrodes  108  disposed on distal end  107  of one or more lead(s)  106 . In other words, lead  106  may position one or more electrodes  108  with respect to various tissue (e.g. cardiac tissue etc.) locations so that medical device system  100  can deliver pulses to the appropriate locations. 
     Lead  106  is provided with an elongated insulative lead body (e.g. insulative polymeric tube etc.), which carries a coiled conductor therein. Other lead body types may be substituted within the context of the present invention, including lead bodies employing multiple lumen tubes and/or stranded or braided conductors as disclosed in U.S. Pat. No. 5,584,873 issued to Shoberg et al, and incorporated herein by reference in relevant part. Alternatively, the lead may include additional conductors arranged either within a multi-lumen lead body or concentrically, as disclosed in U.S. Pat. No. 4,355,646 issued to Kallok et al and incorporated herein by reference in relevant part. Additional pacing electrodes, sensors, or defibrillation electrodes, may of course be added to the lead body and coupled to additional conductors. 
     At the proximal end of the lead body is a connector assembly (e.g. industrial standard (IS)-1, IS-4 connector assemblies etc.) used in commercially available cardiac pacing leads. The connector assembly includes a conductive connector pin which is coupled by means of the conductor within the lead body to a tip electrode located at the distal tip of lead  106 . 
       FIGS. 2-6  depict details of a delivery device  200  (or delivery wire) inserted into a lumen (not shown) of lead  106  in order to position lead  106  in a patient&#39;s body (e.g. left heart etc.). Delivery device  200  has a proximal end  204  and a distal end  206 . Delivery device  200  comprises a controller  208 , an elongated member  202 , a sleeve  216 , conductive springs (or coils)  218 ,  220  and solder coupled to springs  218 ,  220  and to sleeve  216 . Elongated member  202  comprises a conductive material (e.g. stainless steel, NiTiNOL (i.e. a family of nickel (Ni)-titanium (Ti) alloys etc.)) with a length up to L 1  and a diameter that ranges from D 1  to D 4 . At proximal end  204  is controller  208 . Controller  208  is an ergonomic member or knob configured to allow more control of the distal tip of elongated member  202  relative to lead  106 . In particular, controller  208  assists in advancing delivery device  200  beyond the distal tip of lead  106  to provide a “rail” for the lead  106  to track. In one embodiment, controller  208  is permanently attached to elongated member  202 . An exemplary permanent attachment includes an adhesive between controller  208  and elongated member  202 . In another embodiment, controller  208  is temporarily coupled to elongated member  202  to allow controller  208  to be removed from elongated member  202 . For example, controller  208  may be screwed onto the proximal end  204  of elongated member  202 . Other suitable means may be used to connect controller  208  with proximal end  204 . In another embodiment, controller  208  and elongated member  202  may be formed as a single part without any attachments therebetween. 
     In one embodiment, controller  208  comprises a gripping member  210  and a tapered distal end  211  with a length of about L 2 . Gripping member  210  is substantially cylindrically shaped and includes a diameter of about D 1  and a length that extends L 3 . During insertion of a lead  106  into a patient, gripping member  210  is typically held between the thumb and the forefinger of the person attempting to place the lead  106  in the left heart. In one embodiment, gripping member  210  includes elongated recessed regions  212  to enhance the person&#39;s ability to hold gripping member  210 . Other suitable ergonomic features (e.g. crossed recessed regions, rough textured outer surface etc.) may be used. At the distal end of gripping member  210  is a tapered distal end  211 . Tapered distal end  211  includes a diameter D 4 , a length L 4 , and angle θ formed by first and second sides  236 ,  238 . Angle θ ranges from about 120 degrees (°) to about 170°. Tapered distal end  211  of controller  208  is configured to receive the proximal end of elongated member  202 . The proximal end of elongated member  202  includes a diameter D 13 . 
     A distal portion of elongated member  202  is surrounded by cylindrical sleeve  216  with spring  218  disposed between an inner wall of sleeve  216  and elongated member  202 . Sleeve  216  provides lubricity for moving within a lead body and also assists in coil alignment between springs  218 ,  220 . The lubricous nature of sleeve  216  is due, at least in part, to being comprised of polyethylene terephthalate. Sleeve  216  extends a length of L 5  and includes an inner diameter of D sleeve . Solder  224  (also referred to as a second solder element) connects sleeve  216  to elongated member  202 , and to springs  218 ,  220 . Solder  224  is introduced over spring  218  and sleeve  216  at a high temperature. Referring briefly to  FIGS. 4-6 , the proximal joint, distal, tip joints, also include high temperature solder  219 . 
     Elongated member  202  extends a length of L 6 , which is comprised of regions defined by lengths L 7 , L 8 , and L 9 . The L 7  region includes a diameter D 13  whereas the L 8  region is tapered at its distal end and contacts sleeve  216 . The L 8  region has a diameter that ranges from about D 8   small  to about D 8   large . The L 9  region is tapered and includes regions L 10 , L 11 , L 12 , and L 13 . The L 10  region includes a tapered section of elongated member  202  defined by a diameter that ranges from about D 10   small  to about D 10   large . At the distal end of the L 10  region is solder element  222  formed from high temperature solder. Solder element  222 , also referred to as a third solder element, connects sleeve  216  with spring  218  and elongated member  202 . Region L 11  depicts spring  218  around elongated member  202 . Region L 11  includes a tapered section of elongated member  202  defined by a diameter that ranges from about D 11   small  to about D 11   large . The L 12  region extends from solder elements  224  and  214 . The distal tip of elongated member  202  extends into solder  214  which increases isodymetry and body (or stiffness) to elongated member  202 . As shown, the distal tip of elongated member  202  does not extend beyond solder  214  (also referred to as the first solder element). Solder  214  has a diameter of about D 5 . Solder  214 , comprising a low temperature solder, is placed over the tip of the coil and to the distal tip of elongated member  202 . 
     Springs  218 ,  220  are formed from any desired conductive material, selected based on the application of the elongated member being manufactured. Conductive material includes conductive metals or alloys, and/or conductive polymers. For example, springs  218 ,  220  may be formed from silver, platinum, gold, copper, a conductive alloy, or any other conductive material suitable for use in a medical lead  106 . 
     Provided in Table 1 are the general dimensions for a delivery device  200  made to deliver 4 and 6 French leads. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Dimensions of a delivery device. 
               
            
           
           
               
               
               
            
               
                   
                 Dimension of a 4 French 
                 Dimension of a 6 French 
               
               
                 Element designation 
                 delivery device 
                 delivery device 
               
               
                   
               
               
                 L1 
                 43.01 inches  
                 43.01 inches  
               
               
                 L2 
                 0.49 inches 
                 0.49 inches 
               
               
                 L3 
                 0.395 inches  
                 0.395 inches  
               
               
                 L4 
                 0.093 inches  
                 0.093 inches  
               
               
                 L5 
                 8.66 inches 
                 8.66 inches 
               
               
                 L6 
                 42.52 inches  
                 42.52 inches  
               
               
                 L7 
                 28.7 inches 
                 29.1 inches 
               
               
                 L8 
                 3.15 inches 
                 2.76 inches 
               
               
                 L9 
                 11.02 inches  
                 11.02 inches  
               
               
                 L10 
                 5.12 inches 
                 5.91 inches 
               
               
                 L11 
                 3.54 inches 
                 2.76 inches 
               
               
                 L12 
                 2.36 inches 
                 2.36 inches 
               
               
                 L13 
                 0.08 inches 
                 0.08 inches 
               
               
                 D1 
                 0.19 inches 
                 0.19 inches 
               
               
                 D2 
                 0.0024 inches  
                 0.0024 inches  
               
               
                 D3 
                 0.009 inches  
                 0.012 inches  
               
               
                 D4 
                 0.125 inches  
                 0.125 inches  
               
               
                 D5 
                 0.012 inches  
                 0.012 inches  
               
               
                 D13 
                 0.014 inches  
                 0.014 inches  
               
               
                   
               
            
           
         
       
     
     Another embodiment of length of L 1  is about 34 inches. Yet another embodiment of length of L 1  is about 51 inches. L 1  can range from about 34 inches to about 51 inches with the remaining lengths being adjusted (i.e. increased or decreased) to accommodate the lengths of L 1 . In another embodiment, L 1  is greater than 51 inches. 
     The discussion now turns to conventional guidewires that merely move inside a lumen without passing electrical signals therethrough to a programmer (not shown) to map potential placement sites of a lead. More specifically, conventional guidewires are placed in a certain position by an implanting physician and then pacing may be performed. The location of the conventional lead may not be the optimal location, which compels the physician to continue to seek the proper location of the lead. 
     Another embodiment of the claimed invention relates to a mapping guidelet  300  (also referred to as a mapping hybrid stylet/guidewire), depicted in  FIGS. 7A-7C . Mapping guidelet  300  aids in delivery of lead  106  by simultaneously guiding and electrically mapping potential sites for placement of lead  106  into a vein or artery of a patient. In particular, an implanting physician is able quickly subselect the various vein locations/pacing sites through measured electrical values for desired pacing locations prior to placing the left heart lead. Consequently, mapping guidelet  300  reduces time spent and discomfort to the patient in properly locating lead  106  in the patient&#39;s vein or artery. 
     Mapping guidelet  300  includes proximal and distal ends  302 ,  304 , respectively. Additionally, mapping guidelet  300  further comprises an electrically active distal segment  314   a, b , an uncoated conductive segment  312 , a first, second, and third coated segments  306 ,  308 ,  310 , respectively. Referring briefly, to  FIGS. 7A-7B , active distal segment  314   a,b  may be a straight distal tip  314   a  or a curved distal tip  314   b  that is electrically active with a surface area of about 3 to 7 square millimeters. Curved distal tip  314   b  possesses an angle φ that ranges from about 45 degrees (°) to about 60°. In one embodiment, the electrically active wire surface area of distal segment  314   a, b , is treated with an enhanced sensing surface such as titanium nitride (TiN) or a platinum black oxide. Treating the electrically active wire surface area of distal segment  314   a,b  with TiN or a platinum black oxide improves the ability to sense R-waves in the coronary vein locations. 
     Each coated segment  306 ,  308 ,  310  may have a coat thickness that ranges from about 0.0002 inches to about 0.002 inches. The coat thickness is created by applying multiple coats over elongated member  202 . First, second, and third coated segments  306 ,  308 ,  310 , may be coated with a variety of materials. Exemplary coating materials include hydrolytically stable polyimide (e.g. soluble imide (SI) polyimide material (formerly known as Genymer, Genymer SI, and LARC SI), polytetrafluorethylene (PTFE), parlyene (e.g. parlyene C), or other suitable materials. SI polyimide is typically stiffer than PTFE and parylene. In contrast to hydrolytically stable polyimide and PTFE, parylene is vacuum deposited; therefore parylene generally forms very thin thicknesses (e.g. &lt;0.0002 inches, or sometimes microns to Angstroms thick etc.). 
     In one embodiment, second coated segment  308  consists essentially of parlyene and third coated segment consists essentially of PTFE. In another embodiment, first, second, and third coated segments  306 ,  308 ,  310 , are each coated with different materials. In yet another embodiment, first, second, and third coated segments  306 ,  308 ,  310 , are each coated with the same materials. 
     Uncoated conductive segment  312  (bare wire etc.) is located at proximal end  302 . Essentially, uncoated conductive segment  312  is a portion of elongated member  202  without any material being disposed thereon. Retaining rings  316  are disposed at the proximal and distal ends of conductive element  312 . Retaining rings  316  serve the purpose of keeping a programmer clip (i.e. cable connection) (not shown) within the conductive area of conductive segment  312 . U.S. Pat. No. 6,325,756 issued to Webb et al, incorporated herein by reference in relevant part, discusses programmers in greater detail. Retaining rings  316  hold the programmer clip (not shown) when electrical thresholds are sampled via a programmer cable, measuring R-waves from the exposed distal tip  314   a,b . The implanting physician may leave the programmer clip attached and continuously or periodically sample the voltage at the distal tip of elongated member  202  as it is passed and placed in the coronary veins. 
     In one embodiment, the sampled electrical data relates to voltage levels obtained the exposed distal tip  314   a,b . The amplitude from a sampled voltage level is compared to the amplitude of a reference voltage level. In one embodiment, mapping guidelet  300  is unipolar in its sensing ability since a reference voltage level is obtained from uncoated segment  310 . In another embodiment, mapping guidelet  300  is bipolar in its sensing ability since an amplitude of the reference voltage level is obtained from a conductive ring  311 , shown in  FIG. 7C , and compared to the amplitude of the actual voltage from active distal tip  314   a,b . Conductive ring  311  is electrically active and includes a positive clip zone for receiving the pacing clip from the programmer. 
     Another embodiment of the claimed invention relates to controller  400  of a delivery device  200  depicted in  FIGS. 8A-8B , and  9 . Controller  400  is slideably adjustable along the length of a proximal end of lead  106 . Controller  400  has a proximal and distal ends  402 ,  404  respectively and comprises a lever  406 , a body  410  and a pin  412 . Lever  406  is used to engage and disengage controller  400  from elongated body of lead  106 . Body  410  has a locking interference fit to clamp onto about a 0.01 inch to 0.016 inch outer diameter of elongated member  202 . The interference fit should allow up to 0.005 inches. More particularly, an interference range should be 0.0003 to about 0.0005 inches. The interference fit between body  410  and elongated member  202  occurs when lever  406  is engaged ( FIG. 8B ), thereby clamping onto elongated member  202 . 
       FIG. 10  is a flow diagram that depicts an operation for producing a medical electrical lead. At block  500 , a mapping guidelet is configured to map a location of the medical electrical lead. At block  510 , the mapping guidelet is configured to place the lead without requiring the use of both a stylet and a guidewire. Instead, the mapping guidelet uses a single elongated member to place a lead. At block  520 , the mapping guidelet is also configured to pass through a lumen of a medical electrical lead. At block  530 , the mapping guidelet is coupled to a lead body of the medical electrical lead. 
     Various embodiments of the invention have been described. There are a variety of additional embodiments related to delivery device  200  that are within the scope of the claimed invention. For example, elongated member  202  (also referred to as the central core wire) may have various dimensional combinations to alter the stiffness of the delivery device  200  along its length. Elongated member  202  could also be comprised of differing raw materials depending on the specific clinical application of the wire. In addition, the distal and proximal coils that cover the core wires may be replaced with a polymeric sleeve material of various inner and outer diameters, in fact in some embodiments the entire length of the core wire might be covered with a polymeric sleeve material. These sleeve materials could be of differing raw materials depending on whether the sleeve will perform the function of acting as the wire tip, or shaft segment. The outer coating utilized on the wire could be of a hydrophilic or hydrophobic nature depending on the specific clinical application. 
     Another embodiment involves a slideable torque tool may be employed. This embodiment is implemented through side loading and/or a torque-limiting (or a slip clutch mechanism) that engage with the lead via a connector. In another embodiment, for ease of torquing delivery device  200 , a proximal end is configured with square (or a non-rounded) cross-section, segmented round to non-round. In yet another embodiment, the delivery device is configured with alternating floppy and stiff areas. In still yet another embodiment, a coupling and decoupling via a lead and wire mechanism is disclosed. In yet another embodiment, an infusion wire with an injection lumen and sideport are used to inject contrast through the lumen. In yet another embodiment, a mechanism is employed for using a temperature sensitive alloy for lead fixation. In yet another embodiment, a pacing wire may include unipolar and/or bi-polar configuration. This may include a cathode range: 1.5 mm 2  to 15 mm 2 -5 mm 2  nominal and/or an anode range: 5 mm 2  to 30 mm 2 -10 mm 2  nominal. In yet another embodiment, a telescoping delivery device is employed. In yet another embodiment, the delivery device includes a centering/loading tool. 
     Other embodiments of the claimed invention relate to a conductive element (e.g. wire etc.) from which springs  218 ,  220  are formed. Referring to  FIGS. 11A-11B , an exemplary spring  300  is depicted. Spring  300  is comprised of a conductive element  302  (e.g. wire etc.) that includes proximal and distal ends  304 ,  306 . In one embodiment, proximal and/or distal ends  304 ,  306  may be pulled apart to expand (i.e. lengthen) conductive element  302  or may be pushed together (i.e. compress) conductive element  302 . A portion of the length of conductive element  302  may be expanded (e.g. portion near the proximal end, a portion near substantially centralized, and/or a portion near the distal end etc.) Alternatively, the entire length of conductive element  302  may be expanded. 
     Expansion of conductive element  302  may occur through a variety of ways. For example, a raw spring can be expanded by pulling on at least one end  308  (also referred to as a first end) while holding the other end  310  (also referred to as a second end). As depicted, first and second ends  308 ,  310  show a circular cross-section with flattened substantially rectangular or square ends. A winding process can be used to expand conductive element  302 . In one winding process, a “spring winder” may be used to mechanically expand conductive element  302 . 
     Conductive element  302 , in one embodiment, is made from flattened wire. Flattened wire typically comprises a thickness of about 0.0002 inches to about 0.005 inches. In general, a width to thickness ratio for the conductive element  302  can be as high as 10:1, as width is a function of thickness. In one embodiment, the flattened wire includes a substantially rectangular cross-sectional shape. In another embodiment, conductive element  302  includes a substantially round cross-sectional shape. 
     In one embodiment, the conductive element  302  is comprised of conductive materials such as (e.g. stainless steel, Nitinol, MP35N, titanium, platinum, platinum-filled nickel titanium (NiTi) or stainless, cobalt-chromium-nickel alloy (also known as ELGILOY®) or other suitable alloys is covered by a polymeric sleeve. An exemplary polymer sleeve comprises a thermoplastic polymer. An exemplary thermoplastic polymer is polyethylene terephthalate (PET). In another embodiment, the conductive element  302  (e.g. wire etc.) has a cross-section that is round. 
     While the invention has been described in its presently preferred form, it will be understood that the invention is capable of modification without departing from the spirit of the invention as set forth in the appended claims.