Controlled entry pacemaker electrode for myocardial implantation
United States Patent Starr et al.  
 [451 Apr. 29, 1975 CONTROLLED ENTRY PACEMAKER ELECTRODE FOR MYOCARDIAL IMPLANTATION Inventors: Albert Starr, Portland, 0reg.; David L. Swendson, Garden Grove, Calif.  
 Assignee: American Hospital Supply Corporation, Evanston, 111.  
 Filed: Jan. 2, 1974 Appl. No.: 429,974  
 U.S. Cl. 128/418; 128/419 P Int. Cl A6ln 1/04 Field of Search 128/348, 351, 404, 418,  
 References Cited UNITED STATES PATENTS Fisher et al 128/419 P Chardack 128/419 P Williamson 128/419 P Shanker 128/419 P OTHER PUBLICATlONS Morris et 211., Annals of the New York Academy of Sciences.&#34; Vol. 167, Art. 2. Oct. 30, 1969, pp. 987-994 (pp. 990 &amp; 991 relied on).  
 Schuder et al., Transactions of the American Society of Artificial internal Organs,&#34; Vol. 10, 1964, pp. 366-370.  
 Primary Examiner-William E. Kamm Attorney, Agent, or Firm-Lee R. Schermerhorn [57) ABSTRACT An insulated lead has a sharp pointed electrode on its distal end for penetration into the myocardium. The tip end portion of the electrode is bent at a small angle to the axis of the lead so that the depth of penetration of the electrode can be controlled by choosing an appropriate angle of penetration. A felt pad on the lead and electrode provides for a single suture fixation of the lead to the heart muscle and controls blood seepage adjacent the electrode.  
 6 Claims, 5 Drawing Figures CONTROLLED ENTRY PACEMAKER ELECTRODE FOR MYOCARDIAL IMPLANTATION BACKGROUND OF THE INVENTION This invention relates to a pacemaker electrode.  
  In myocardial implantation. a pointed stimulating electrode is caused to penetrate into the myocardium or heart muscle. The electrode is applied externally and is equipped with suitable means for fixation to the outside of the heart by sutures.  
  It has been the practice heretofore to project the electrode rigidly at a right angle from a relatively stiff and rigid base plate so that the electrode penetrates the myocardium in a direction perpendicular to the surface of the heart. With such an arrangement the depth of penetration is predetermined at the time of manufacture and it cannot be varied by the surgeon at the time of implantation. This imposes undesirable limitations on the technique of implantation because the optimum depth of penetration may vary.  
  Objects of the invention are, therefore, to provide a controlled entry myocardial lead, to provide a myocardial stimulating electrode wherein the depth of pene tration may be controlled at the time of implantation, to provide an electrode which allows a wider choice as to the manner in which the heart is approached and exposed, to provide an electrode adaptable to a minimum exposure of epicardial surface. to provide an improved suturing pad, to provide means for controlling blood seepage adjacent the electrode, and to provide a myo cardial lead which may be secured quickly and come niently by a single suture.  
 SUMMARY OF THE INVENTION The present lead has a sharp pointed electrode on its distal end for penetration into the myocardium. The tip end portion of the electrode is bent at a small angle to the axis of the lead so that the depth of penetration of the electrode can be controlled by choosing an appro priate angle of penetration. A felt pad on the lead provides for single suture fixation of the lead to the heart muscle.  
  Placement of the electrode is facilitated when a minimum of epicardial surface can be exposed. This allows a wider choice as to the manner in which the heart is approached and exposed. The porous and flexible suture pad also performs a hcmostatic function. controlling blood seepage from the area immediately surrounding the electrode tip.  
  The invention will be better understood and additional objects and advantages will become apparent from the following description of the preferred embodiment illustrated on the accompanying drawing. Various changes may be made, however. in the details of construction and arrangement of parts and certain features may be used without others. All such modifications within the scope of the appended claims are included in the invention.  
 BRIEF DESCRIPTION OF THE DRAWING FIG. I is a fragmentary elevation view of a heart showing the first step in the placement of the electrode; FIG. 2 is a view similar to FIG. I showing fixation of the electrode;  
  FIG. 3 is a plan view of the distal end ofthe lead, with parts broken away;  
  FIG. 4 is a side elevation view, with parts broken away; and  
  FIG. 5 is a longitudinal sectional view of the proximal end of the lead.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment shown on the drawing comprises an elongated lead having an electrode portion II on its distal end and a connector fitting 12 on its proximal end. The lead comprises a flexible insulating tube I3 of suitable material. such as silicone rubbcr, containing a flexible coiled conductor 15. Conductor I5 is made of a metal which is extremely corrosion and fatigue resistant. such as, for example, Elgiloy, manufactured by Elgiloy Company, a division of American Gage and Machine Company in Elgin, Ill.  
  The electrode portion ll comprises a rigid electrode body 20 of the same metal as conductor 15. Electrode 20 has a sharp point 21 in its outer end and a cylindrical axial bore 22 in its inner end to receive the end of the conductor coil 15. The wall of bore 22 is crimped at 23 on the coil to anchor the coil and make good electrical contact therewith. The inner end of electrode abuts the end of tube 13.  
  After crimping, a portion of the electrode 20 is covered with a silicone rubber insulating sleeve 25 which overlies the end of tube 13 for a short distance. The distal end of sleeve 25 is received in an annular recess 26 in electrode 20 so as to leave the sharpened tip end 21 of the electrode exposed and provide a continuous relatively smooth surface across the transition from the point 21 to the sleeve 25.  
  For reasons which will presently appear, the outer end portion of electrode 20 is bent at 27 at a small angle A from the axis of its inner end as shown in FIG. 4. A preferred value for the angle A is l6 plus or minus 1 but any angle within the range between 10 and 45 would be considered within the scope of the invention.  
  A porous and flexible sewing pad 30 of a polyester felt, such as Dacron, is bonded to the tubes 13 and 25 at or closely adjacent the proximal side of the bend 27. Pad 30 is preferably rectangular with outlying wings projecting from opposite sides of the lead and electrode with the pad 30 preferably underlying the lead and electrode on the concave side of bend 27. Thus, the pad 30 is disposed in a plane perpendicular to the plane of angle A. The sewing pad may include a smaller pad 31 overlying the lead and electrode and secured at its ends by stitches 32 to the underlying pad 30. In addition, the overlying pad 31 may also be adhesively bonded to tubes I3 and 25 and to the underlying pad 30.  
  The angle A in the electrode provides for varying the depth of penetration. The angle of penetration is not limited to the fixed value of the angle A but may be varied by the surgeon as penetration occurs. For deep pen etration the point 21 may be inserted at a steeper angle than the angle A. After penetration, the muscle tissue will adjust to the position ultimately assumed by point 21 when pad 30 is sutured to the surface of the heart.  
  The small angle A provides greater versatility in the selection of implant sites. Should the electrode be implanted in the left ventricle, the penetration of the point 21 can be made relatively deep. If the right ventricle is more easily exposed, penetration can be made more shallow.  
  Thus. when a minimum of epicardial surface can be exposed. placement of the electrode is facilitated. This allows a wider choice as to the manner in which the heart is approached and exposed. For example. the ventricles may be exposed by sternal split, subdiaphragmatic or abdominal, mediastinal or costal cartilage. or by standard thoracotomy.  
  When the point of penetration has been selected. the electrode point 21 may be pushed directly into the myocardium. If scar tissue impedes entry. a small stab wound may be made as indicated at 38 in FIG. 1 to assist entry of the point 21.  
  Prior to penetration a fine. non-absorbable suture 35 is passed through one wing of the pad 30 from top to bottom. through the myocardium, then through the opposite wing of pad 30 from bottom to top as shown in FIG. 1. The lead and pad 30 are slid down the suture until the electrode tip 2! penetrates the myocardium as previously described and both wings of the pad contact the epicardial surface. The suture is then secured by knot 36 as shown in FIG. 2.  
  The flexibility of the myocardium and the flexibility of paid 30 accommodate the angle of penetration of electrode point 21 when that angle is not the same as angle A. This flexibility and accommodation of pad 30 are enhanced by the use of a single suture overlying the lead 10 transversely as a fulcrum.  
  Heretofore. it has been the practice to use a relatively stiff. rigid and non-porous sewing pad provided with holes around its periphery to receive multiple sutures at a plurality of points distributed both longitudinally and laterally of the lead. Such a pad has no accommodation to the epicardial surface; the heart must accommodate to the pad.  
  Further, the absorbent properties of the present pad 30 perform a hemostatic function by controlling blood seepage from an area adjacent the electrode tip.  
  Connector 12 comprises a metal pin 45 having a bore 46 to receive the proximal end of conductor coil 15. The wall of the bore is crimped at 47 on coil to anchor the coil and make good electrical connection therewith. Sharp bends at the connector are prevented by a protective wire coil 48 and an external rubber boot 49. An insulating seal 50 secures the pin 45 in a standard bayonet fitting 51.  
  Having now described our invention and in what manner the same may be used, what we claim as new and desire to protect by Letters Patent is:  
  l. A controlled entry pacemaker electrode for myocardial implantation comprising a bent, rigid electrode having a pointed distal end portion disposed at a small angle to the axis of its proximal end portion so that said pointed end portion may be caused to penetrate the myocardium at an oblique angle which will effect penetration to a selected depth. an insulating sleeve on said electrode leaving the point thereof exposed. a flexible lead connected axially to said proximal end portion of said electrode, a flexible insulating tube on said lead. and a transverse sewing pad fixedly secured to said sleeve and tube in a plane perpendicular to the plane of the angle in said bend and having wings extending laterally on opposite sides of said lead and electrode with the distal edge of said pad spaced in a proximal di rection from the bend in the electrode so that said pad may lie against the surface of the heart and receive a suture in the herat extending through said wings and transversely overlying said flexible lead as a fulcrum to hold said pointed end of said electrode penetrated in the myocardim at said oblique angle projecting in a distal direction from said pad.  
  2. An electrode as defined in claim 1, said sewing pad being flexible and absorbent to accommodate to the epicardial surface and control blood seepage adjacent said electrode.  
  3. An electrode as defined in claim 1, said angle of the bend in said electrode having a value in the range between lO and 45.  
  4. An electrode as defined in claim 3, said angle being approximately l6&#34;.  
  5. An electrode as defined in claim 1 including said electrode. and an annular recess in said electrode adjacent said pointed end containing the distal end of said sleeve.  
  6. An electrode as defined in claim 1 including said suture. said suture comprising a single suture spaced a short distance in a proximal direction from the proximal end of said rigid electrode.