Patent Publication Number: US-6223087-B1

Title: Apparatus for replacement of an electrode at a desire location in the atrium

Description:
This application is a division of application No. 09/036,114, filed Mar. 6, 1998. Now U.S. Pat. No. 6,006,137 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to implantable medical leads, and more particularly to cardiac pacing leads and methods of their delivery. 
     As discussed in the article, “Atrial Septal Pacing: A method for Pacing Both Atria Simultaneously”, by Spencer et al. published in PACE, Vol. 29, November, 1997, pp. 2739-2745, it is possible to pace both atria with a single active fixation electrode appropriately located in the anterior portion of the right side of the atrial septum separating the right and left atria. However, using present lead technologies, accurate placement of a lead at this desired site, typically located adjacent and slightly above and anterior to the ostium of the coronary sinus can be relatively difficult. While delivery of cardiac pacing leads or other electrode catheters to desired locations within the heart by means of a deflectable or pre-curved guide catheter is known, typically the location of the lead to be so delivered must be determined flouroscopically. As the lead is to be placed while the heart is beating, placement even using a guide catheter is not as simple as would be desired. 
     SUMMARY OF THE INVENTION 
     The present invention is directed toward providing a reliable and easy to use mechanism for accurately locating an atrial pacing electrode in the atrial septum, adjacent and above the ostium of the coronary sinus. The present invention accomplishes this desired result by means of an active fixation atrial pacing lead delivered by means of a pre-curved or preferably a deflectable guiding catheter. The guiding catheter is provided with an internal lumen through which the atrial pacing lead is passed, which lumen exits laterally, proximal to the distal tip of the catheter. The distal portion of the catheter is pre-curved or deflectable into an S-shaped bend, having two generally coplanar curves, with a lateral exit aperture located along the outer portion of the more proximal of the two curves. The guiding catheter when so curved is configured so that when the distal tip of the guiding catheter is located in the coronary sinus, the distal end of the atrial lead may be advanced out of the lateral aperture of the guide catheter and embedded in the atrial septum at the desired location. Locating the distal end of the guide catheter in the coronary sinus both assists in proper location of the atrial pacing lead relative to the coronary sinus and in providing a stable platform, allowing the lead to be maintained in its desired location during the measurement of pacing and sensing thresholds and during placement of the electrode in the atrial septal tissue. After the atrial electrode is placed, the guide catheter is withdrawn over the lead, and the lead is coupled to an implantable cardiac pacemaker. 
     In a preferred embodiment, the guide catheter is configured so that it may be deflectable to first display only the more distally located of the two curves, facilitating placement of the guide catheter in the coronary sinus. The catheter then preferably may then be curved to also display the more proximal of the two curves, facilitating the exit of the atrial pacing lead adjacent to the desired location on the atrial septum. The catheter may be deflectable by any of the numerous presently known mechanisms for providing controlled variable curvature, including but not limited to the use of internal pull wires and the use of nested straight and pre-curved catheter tubes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of an atrial pacing lead appropriate for use in conjunction with the present invention. 
     FIG. 2 is a plan view of the lead of FIG. 1 in conjunction with a deflectable guide catheter according to a first embodiment of the present invention. 
     FIG. 3 is a plan view of the lead according to FIG. 1 in conjunction with a deflectable guide catheter according to a second embodiment of the present invention. 
     FIG. 4 illustrates the initial advancement of the guide catheter of FIG. 2 into the right atrium, prior to placement of the atrial lead. 
     FIG. 5 illustrates the guide catheter of FIG. 2, deflected to display only the more distal of its two curves, prior to placement of the distal end of the guide catheter into the coronary sinus. 
     FIG. 6 illustrates the guide catheter of FIG. 2, deflected to display only the more distal of its two curves, after placement of the distal end of the guide catheter into the coronary sinus. 
     FIG. 7 illustrates the guide catheter of FIG. 2, deflected to display both of its two curves, with the distal end of the atrial pacing lead advanced from the lateral aperture into contact with the intra-atrial septum at the desired pacing site. 
     FIG. 8 illustrates the atrial lead after placement, coupled to an implantable pacemaker to allow for single electrode bi-atrial pacing. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates an atrial lead according to the present invention. The lead is provided with an elongated insulative lead body  10  which carries at least one electrical conductor therein. As illustrated, the lead is configured as a bipolar lead and thus carries two conductors within lead body  10 . Located at the distal end of the lead is an active fixation electrode  12  which in this case takes the form of a helical electrode. An optional, indifferent electrode  14  is provided proximal to the active fixation electrode  12 . Electrode  12  as illustrated takes the form of a fixed helix, rotatable into body tissue by rotation of lead body  10 . Alternatively, electrode  12  may be replaced with an advanceable helix as disclosed in U.S. Pat. No. 4,106,512 issued to Bisping or may take the form of a barb, hook or other known type of active fixation electrode as described in U.S. Pat. No. 4,497,326 issued to Curry, U.S. Pat. No. 4,257,428 issued to Barton et al. or U.S. Pat. No. 4,475,560 issued to Tarjan et al., all of which are incorporated herein by reference in their entireties. As an additional alternative, electrode  12  may be replaced by a ring or tip electrode in conjunction with a separate active fixation device, if desired. 
     At the proximal end of the lead is located an iso-diametric connector assembly  16  which carries two connector rings  18  and  20 , coupled to electrodes  14  and  12 , respectively by means of conductors located in lead body  10 . Iso-diametric connector  16  may correspond to that in allowed, commonly assigned, U.S. patent application Ser. No. 08/846,008 by Ries et al., filed on Apr. 25, 1997, also incorporated herein by reference in its entirety. The provision of an iso-diametric connector assembly is believed beneficial in the context of the present invention in that it simplifies removal of the guide catheter over the lead body by simply pulling the guide catheter proximally over the lead. In the absence of an iso-diametric connector assembly, provision for splitting or slitting the guide catheter to enable its removal over the connector assembly as disclosed in U.S. Pat. No. 5,188,606, issued to Maloney et al., incorporated herein by reference in its entirety could alternatively be provided. 
     FIG. 2 illustrates the lead of FIG. 1 mounted in a guide catheter according to the present invention. The guide catheter is provided with an elongated, pre-curved catheter body comprised of a curved inner tube  100  and a straight outer tube  101 . The longitudinal lumen within tube  100  exits at a lateral aperture  104  through which the distal portion of the lead of FIG. 1 can be seen emerging, with electrodes  12  and  14  visible exterior to the guide catheter tube  100 . At the proximal end of catheter tube  101  is a fitting  103 , through which catheter tube  100  exits. At proximal end of catheter tube  100  is a fitting  102 , through which lead body  10  exits. The proximal portion of the lead body  10 , connector assembly and connector rings  18  and  20  are visible exiting the proximal end of fitting  102 . 
     Lead body  10  is slidable within tube  100  so that it its distal end may be drawn proximally into tube  100  through lateral aperture  104 . Tubes  100  and  102  are similarly slidable relative to each other so that the distal, curved portion  106  of tube  100  may be drawn into the distal end of tube  101 , thereby straightening tube  100  to provide a guide catheter with a generally straight configuration. The curved portion of tube  100  is provided with two generally planar oppositely directed curves  105 A and  105 B. In the embodiment illustrated, curve  105 B is located about an inch proximal to the distal end of tube  100  and curve  105 A is located about ⅜of an inch proximal to curve  5 B. Both curves in the embodiment illustrated are about 45 degrees. Lateral aperture  104  is located on the outside of curve  105 A, axially aligned with the portion of catheter tube  100  extending proximal thereto, facilitating exit of the distal end of the lead body  10  an rotation of lead body  10  to screw electrode  12  into heart tissue. 
     Initially, lead body  10  is withdrawn into tube  100  and tube  100  is withdrawn into tube  101  to provide a generally straight guide catheter. When the distal end of the guide catheter enters the right atrium, tube  100  is advance distally relative to tube  101  to allow curve  105 B to exit tube  101 , providing a guide catheter with a single curve configured to assist in location of the distal end of the guide catheter in the coronary sinus. After the distal end of the guide catheter is in the coronary sinus, tube  101  is withdrawn proximally to allow curve  105 A to exit tube  101 , and the distal end of lead body  10  is then advanced distally through lateral aperture  104  and screwed into the inter-atrial septum. The guide catheter is then withdrawn proximally over lead body  10 . 
     FIG. 3 illustrates the lead of FIG. 1 in conjunction with an alternative, deflectable guide catheter according to the present invention. The guide catheter as illustrated employs two internal deflection wires to provide two curves  205  and  205 B, corresponding to curves  105 A and  105 B illustrated in FIG.  2 . At the proximal end of the catheter body  200  is a handle  202  which carries two rotatable knobs  201  and  203 , each of which pulls one of the two tension wires within the catheter body  200 , for example using the mechanisms disclosed in allowed U.S. patent application Ser. No. 08/613,298 filed by Maguire et al. on Mar. 11, 1996, and incorporated herein by reference in its entirety. One deflection wire extends to a point just distal to curve  205 A and the other extends to a point distal to curve  205 B and, in the manner described in the Maguire et al. application, may be employed to cause the catheter body  200  to successively display curves  205 B and  205 A, allowing the guide catheter to perform in a manner analogous to the guide catheter illustrated in FIG.  2 . Like the guide catheter of FIG. 2, the guide catheter is provided with a lateral aperture  204  which is located on the exterior of curve  205 A. The proximal end of lead body  10 , carrying connector assembly  16  is shown exiting the handle  202 . 
     Preferably, the length of the lead of FIG. 1 is sufficient so that the connector assembly  16  and the proximal portion of the lead body  10  extend proximal to the handle or fitting of the guide catheters of FIGS. 2 and 3 when the electrode  12  is located in or adjacent the tissue of the atrial septum, to allow for connection of the electrode connectors  18  and  20  to an external pacing systems analyzer to facilitate the taking of pacing and sensing thresholds, before and after placement of electrode  12  and to allow rotation of lead body  10  to screw electrode  12  into atrial tissue. As illustrated, the lateral aperture  104  is shown exiting on the interior of the curve either pre-formed into the guide catheter as in FIG. 2 or formed by tension applied to the internal pull wires in the catheter of FIG.  3 . This in turn facilitates location of the electrode  12  in the atrial septal tissues above the ostium of the coronary sinus when the distal ends of the catheter bodies  100 ,  200  are placed in the ostium of the coronary sinus. 
     FIGS. 4-8 illustrate the method of use of the lead of FIG. 1 in conjunction with the guide catheter of FIG.  2 . Numbered elements correspond to identically numbered elements in FIGS. 1 and 2. 
     FIG. 4 illustrates advancement of the catheter illustrated in FIG. 2 into the atrium of a human heart. The guide catheter body is advanced with tube  100  withdrawn into tube  101  to straighten both curves  105 A and  105 B and with the distal end of the atrial pacing lead of FIG. 1 withdrawn interior to the lateral aperture  104  on tube  100 . The desired location of the electrode on the pacing lead is illustrated at  302 , relative to the ostium  300  of the coronary sinus and the fossa ovale  303 . 
     FIG. 5 shows the guide catheter with tube  100  extending distally from tube  101  to allow curve  105 B to exit tube  101 , providing a guide catheter with a single curve adapted to assist in locating its distal end in the ostium  300  of the coronary sinus. 
     FIG. 6 shows the guide catheter with its distal end inserted into the ostium  300  of the coronary sinus, with curve  105 B adjacent the ostium. 
     FIG. 7 shows catheter tube  101  withdrawn proximally to allow curve  105 A to exit the tube  101 , in turn placing the lateral aperture  104  adjacent the tissue of the intra-atrial septum. The distal end of lead body  10  is advanced through aperture  104  and into contact with the septum at the desired location  302 . With the helical electrode located adjacent the atrial tissue, cardiac pacing and sensing thresholds can be taken. Assuming the pacing and sensing thresholds are appropriate, the lead body may be located within catheter tube  100  to screw electrode  112  into the desired location on the atrial septum. If, however, pacing and sensing thresholds are not initially adequate, the specific location of the active fixation electrode  12  may be varied by twisting the body of the guide catheter slightly, keeping the distal end of the catheter located in the ostium of the coronary sinus and/or by advancing or retracting the distal end of the catheter slightly relative to the ostium of the coronary sinus. At such point as desired pacing and thresholds are acquired, the electrode  12  may be screwed into atrial septal tissue. 
     FIG. 8 illustrates the lead of FIG. 1 as installed with electrode  12  located at the desired location  302  in the intra-atrial septum. In this location, electrical pulses provided to electrode  12  can be employed to simultaneously pace both atria. The connector  16  located at the proximal end of lead body  10  is shown inserted into the connector block  402  of a cardiac pacemaker  400  which employs electrodes  12  and  14  to sense and pace the atria of the heart.