US3844292A

US3844292A - Intravascular lead assembly

Info

Publication number: US3844292A
Application number: US00261156A
Authority: US
Inventors: L Bolduc
Original assignee: Medtronic Inc
Current assignee: Medtronic Inc
Priority date: 1972-06-09
Filing date: 1972-06-09
Publication date: 1974-10-29
Anticipated expiration: 1991-10-29
Also published as: GB1437354A; NL7308020A; FR2187365B1; CA1003502A; JPS4956488A; AR197903A1; SE7705349L; FR2187365A1; DE2328996A1

Abstract

A body-implantable, intravascular lead assembly which is adapted to be connected to a source of electrical energy at its proximal end. At the distal end of the lead is affixed an electrically conductive barb. Means are provided for inserting the lead in and guiding it through a body vessel to a desired location inside the body. Further means are provided for lodging and permanently securing the barb to body tissue at the desired location. Part of the assembly is withdrawn from the vessel after the barb is lodged and secured in the tissue. The lead and a portion of the barb are sealed from body fluids and tissue by a material substantially inert to body fluids and tissue.

Description

United States Patent 1191 Bolduc Oct. 29, 1974 1 INTRAVASCULAR LEAD ASSEMBLY [75] lnventor: Lee Robin Bolduc, Minneapolis,

Minn.

[73] Assignee: Medtronic, Inc., Minneapolis, Minn. [22] Filed: June 9, 1972 [21] Appl. No.: 261,156

[52] US. Cl 128/418, 128/419 P [51] Int. Cl A6ln l/04 [58] Field 01 Search 128/418, 419 P, 419, 404, 128/405, 2.06 E, 2.1 E, 348, 349, 214.4, 2 R,

' 2.1 R, DIG. 4

[56] References Cited 7 UNITED STATES PATENTS 2,831,174 4/1958 Hilmo 128/418 X 3,087,486 4/1963 Kilpatrick 128/2.1 E 3,416,534 12/1968 Quinn 128/418 3,536,073 10/1970 128/214.4 3,572,344 3 1971 B olduc 1281418 3,580,242 5/1971 La ClOiX 3,595,230. 7 7/1971 Suyeoka 128/348 X OTHER PUBLICATIONS Wende et al., Neue lntrakardiale Schrittmacherelektrodc, Deutsche Medizinischc, Wochenschrift, Nr. 40, Oct. 2, 70, 95 lg, pp. 2026-2028.

Schaldach, New Pacemaker Electrodes, Transactions: Am. Society for Artificial Internal Organs, Vol. 17, pp. 29-35, 1971.

Primary ExaminerRichard A. Gaudet Assistant ExaminerLee S. Cohen Attorney, Agent, or Firmlrving S. Rappaport; Wayne A. Sivertson; Joseph F. Breimayer 1 ABSTRACT A body-implantable, intravascular lead assembly which isadapted to be connected to a source of electrical energy at its proximal end. At the distal end of the lead is affixed an electrically conductive barb. Means are provided for inserting the lead in and guiding it through a body vesselto a desired-location'inside the body. Further means are provided for lodging and permanently securing the barb to body tissue at the desired location. Part of the assembly is withdrawn from the vessel after the barbis lodged and secured in the tissue. The lead and a portion of the barb are sealed from body fluids and tissue by a material substantially inert to body fluids and tissue.

17 Claims, 6 Drawing Figures PATENTEU URI 29 I974 SW. 1 OF 6 m nimums 12mv 3344292 sum aor 6 FIG. 2

PAIENIEDBBI 29 m4 SHEET 50$ 6 FIG. 5

INTRAVASCULAR LEAD ASSEMBLY BACKGROUND OF THE INVENTION There are generally two types of body-implantable leads-one which requires surgery to expose that portion of the body to which the electrode is to be affixed and the other which is inserted in and guided to the desired location through a body vessel. In the cardiovascular field, in particular, there are myocardial and endocardial type leads. Use of a standard myocardial lead generally provides an excellent electrical contact but requires a thoracotomy in order to affix the electrodes in the outer wall of the heart. This type of surgery is quite strenuous on the patient, particularly an elderly one. Use of a standard endocardial lead .does not involve serious surgery since the lead is inserted in and guided through a selected vein. However, endocardial leads currently in use are difficult to place and to maintain in proper position and do not insure the best electrical contact since the electrode merely rests against the inner wall of the heart at the apex of the right ventricle. As a result, the electrodes of such prior art leads tend to become dislodged from their proper position, often resulting in loss of heart capture and thus loss of stimulation of the patient's heart. Also, since the electrodes of an endocardial lead are not secured in the cardiac tissue, the lead tends to move with each contraction of the heart muscle, thereby forming an undesirable callous or fibrotic growth on the inner wall of the right ventricle. Another problem is that with the contraction of the heart, the tip or distal electrode may occasionally puncture the heart wall, resulting in serious injury to the heart and a loss of heart capture.

The body-implantable lead of the present invention combines all the advantages of both the myocardial and e ndocardial leads with none of the attendant disadvantages of each of these leads as currently found in the prior art. One of the features of the present invention is the provision of a body-implantable intravascular lead which can be lodged in and permanently secured to the body tissue which it is desired to stimulate. Another feature of the present invention is an extremely thin, durable, very flexible lead with excellent electrical and mechanical properties. An advantage of the present invention is the fact that the electrode is lodgedin and permanently secured to the tissue so that puncturing of the surrounding tissue and formation of a callous or fibrotic growth cannot occur. Still another feature of the present invention is the provision of a very simple, easily operable means for inserting the lead into and guiding it through a body vessel to the desired location. An advantage is realized from the fact that the insertion and guidance means imparts sufficient rigidity to the lead to facilitate its placement, thereby eliminating the need for a stylette and thus allowing the lead to be made thinner and more flexible than would otherwise be possible. Yet another feature is the means for lodging and permanently securing the electrode to the selected body tissue once the lead is in proper position. An advantage is realized from the fact that the insertion and guiding means and the lodging and securing means may be made as an integral, disposable unit which is very simple to manufacture, and extremely easy to operate. Once the electrode is secured in the tissue at the desired location, this unit is easily removed and can be disposed.

SUMMARY OF THE INVENTION The above features and advantages of the present invention, as well as others, are accomplished by providing a body-implantable, intravascular lead comprising electrically conductive lead means adapted to be connected at one end to a source of electrical energy and electrode means affixed to the opposite end of the lead means and adapted to be firmly lodged in and permanently secured to tissue inside the body at a desired location. The lead means and the portion of the electrode means affixed to the lead means are sealed from living animal body fluids and tissue by a material substantially inert to body fluids and tissue. Further means are provided for permitting the lead means and electrode means to be inserted into and guided through a body vessel to a desired location and position inside the body. Means are also provided for permitting the electrode means to be firmly lodged in and permanently secured to body tissue at the desired location.

Other features, advantages and objects of the present invention will hereinafter become more fully apparent from the following description of the drawings, which illustrate-a preferred embodiment.

BRIEF DESCRIPTIONOF THE DRAWINGS tion for taking threshold measurements with the barb of the lead of FIG. l just barely extending beyond th device of FIG. 2;

FIG. 5 shows the lead assembly of FIG. 3 in another position for the lodging and securing of the electrode of the lead into the body tissue at the desired location inside the body; and

FIG. 6 shows the lead assembly of FIGS. 3 and 4 with the electrode of thelead lodged in and permanently secured in the tissue forming the apex of the right ventricle of a heart. I

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a lead 10 having an electrical conductor 12 which may, for example, be of a configuration and construction as the lead described in US. Pat. No. 3,572,344. Affixed to the distal end 14 of conductor 12 is an electrically conductiveelectrode 16 having a sharply-pointed electrically conductive barb 18 formed on the end thereof, both of which may be metallic. Electrode l6 and barb 18 are made of a metal which is substantially inert to body fluids and tissue, such as platinum or a platinum-iridium alloy. Conductor 12 has a covering 20 which is made of a material substantially inert to body fluids and tissue such as, for example, silicone rubber. Surrounding the distal end 14 of conductor 12 and a portion of electrode 16 is a substantially cylindrical sleeve 22 having three spaced ridges 24 formed integrally therewith along its length. Sleeve 22 and ridges 24 are formed as an integral sleeve and may be made of a material substantially inert to body fluids and tissue, such as silicone rubber. Proximal end 28 of conductor I2 may be fitted with a connector pin (not shown) or in any other manner adapted for connection to a source of electrical energy such as a pulse generator.

FIG. 2 shows a cross sectional view of a device 30 which may be used for positioning the lead 10 of FIG. I at the desired location within the body as will be described hereinafter. Device 30 has a pair of concentric, substantially

cylindrical'hollow tubes

32 and 34.

Tubes

32 and 34 are made ofa pliant material, such as, for example, teflon. Outer tube 32 is maintained in a fixed position by a substantially cylindrical, hollow sleeve 38 having a flat plate 40 formed integrally therewith. Sleeve 38 and plate 40 may be made of a machineable polymer such as Delrin or Nylon. Inner tube 34 is axially movable within outer tube 32 and sleeve 38. Projecting through an opening in plate 40 is a plunger 42, also made of a machineable polymer such as Delrin or Nylon. Plunger 42 has an opening 44 passing therethrough. Plunger 42 has an end 46 to which is affixed inner tube 34. Tube 34 and opening 44 define a passageway in which lead 10 is placed as willbe described later; As plunger 42 is pushed toward plate 40, when the appropriate locking mechanisms are unlocked, tube 34 moves axially within and toward the distal end 48.0f tube 32.

Device 30 has a first locking mechanism 49. With reference to FIG. 4, locking mechanism 49 comprises a slide 50 having a pin 52 projecting from one end thereof. Sleeve 38 and plunger 42 have aligning openings in one side thereof through which pin 52 passes for providing this first locking mechanism. With pin 52 in the aligned openings, plunger 42 cannot be moved in either direction. A screw 53 shown in FIG. 2 passes through an elongated opening through plate 40 and into slide 50 and allows slide 50 to move so that pin 52 may be engaged with. or disengaged from, the openings in the sides of sleeve 38 and plunger 42.

Device 30 has a second locking mechanism 54 comprising a second slide 56 having a lip 58 which may be grasped for engaging and disengaging an edge 60 of slide 56 with the opposing face of plunger 42. Slide 56 has a pair of legs 62 between which plunger 42 is located. Slide 56 has an elongated opening. A screw 64 passes through plate 40 and slide 56 and together with legs 62 allows slide 56 to have edge 60 engage with and disengage from a groove 66 located in the opposing face of plunger 42. Plunger 42 also has a pair of shoulders 67 on opposite sides thereof which are designed to engage legs 62 when locking mechanism 54 is unlocked and plunger 42 is fully depressed.

The operative relationship between device 30 and lead 10 will now be described in conjunction with FIGS. 3-5. Lead assembly 70 will be described in the application of using lead 10 as a lead positioned intravenously into the heart for use as a cardiac pacemaker lead. When the lead assembly 70 shown in FIG. 3 is removed from its sterile package, lead I is positioned in the opening defined by tube 34 and opening 44 in plunger 42. Pin 52 of slide 50 is positioned in the aligned openings in sleeve 38 and plunger 42 and slide 56 is in the locked position whereby edge 60 abuts against groove 66 in the opposing face of plunger 42. With locking

mechanisms

49 and 54 in their locked positions as shown in FIG. 3, electrode 16 and barb 18 are located well inside outer tube 32 with the sleeve 22 abutting against'the distal end of tube 34. Ridges 24 of sleeve 22 engage the inner wall of tube 32 thereby forming a seal to prevent the back-up of blood into

tubes

32 and 34 when device 30 with lead 10 carried thereby is inserted into a body vessel. With the locking

mechanisms

49 and 54 in their locked positions, as shown in FIG. 3, the distal end 48 of tube 32 is inserted,

for example, into the right jugular vein. Device 30 serves as a means for inserting lead 10 into the vein and guiding it to the desired position in the heart. When the tube 32 is believed to be in the proper position in the heart, locking mechanism 49 is unlocked as shown in FIG. 4 by pulling slide 50 so that pin 52 is disengaged from the aligned openings in sleeve 38 and plunger 42. Plunger 42 may then be depressed to move inner tube 34 and lead 10 to a position, shown in FIG. 4, where the edge defined by groove 66 in plunger 42 is stopped by edge of locking mechanism 54. In this position barb 18 just barely extends beyond the end 48 of tube 32 so that the necessary threshold measurements may be taken. The threshold measurements are used to determine whether the electrode position in relation to the heart tissue is adequate or not. Good electrode positioning is important, as only with good positioning can the patients heart be maintained in capture at-low voltages. When these measurements have been completed and a satisfactory electrode position found, locking mechanism 54 is unlocked, as shown in FIG. 5,'by moving slide 56 in a direction away from plunger 42. Movement of slide 56 disengages edge 60 of slide 56 from plunger 42. This disengagement allows plunger 42 to be further depressed until shoulders 67 of'plunger 42 engage legs 62 of slide 56, thereby moving electrode 16 a predetermined distance out of tube 32 and driving barb 18 a predetermined distance into the tissue of the heart. These predetermined distances are such that barb 18 is driven sufficiently into myocardial tissue to be permanently secured therein but without puncturing through the heart's wall. The total distance through which barb 18 moves is determined by the distance X from shoulders 67 to the surface of slide 56 when both locking

mechanisms

49 and 54 are in their locked positions as shown in FIG. 3. Device 30 may then be completely withdrawn from the vein by pulling device 30 past lead 10, leaving barb 18 lodged in and permanently secured to heart tissue.

FIG. 5 shows plunger 42 in its fully depressed posi- I tion with shoulders 67 abutting legs 62 and with electrode 16 extended beyond end 48 of tube 32. FIG. 6 shows barb l8lodged in and permanently secured in heart tissue and with device 30 partially withdrawn. After device 30 is fully withdrawn from the vein, the proximal end 28 of lead 10 is ready to be connected to the pulse generator for applying stimulating pulses through lead 10 and electrode 16 to the heart.

A single lead 10 would be used in a monopolar pacing system. Use of a pair of leads 10 would permit use I claims.

What is claimed is:

l. A body-implantable, intravascular lead adapted to f be connected at its proximal end to a source of electrical energy and permanently secured at its distal end through the endothelial tissue of a living animal body for electrical stimulation thereof comprising:

electrically conductive lead means for insertion in and guidance through a body vessel to a desired location and position inside an organ of a living animal body the lead means having a cross-section which will fit within a body vessel; electrode means affixed to the distalend of said lead means and adapted to supply electrical impulses to tissue at a desired location inside the living animal body, said electrode means including a tissue piercing portion and further including separate tissue engaging means for allowing said electrode means to be firmly lodged in and permanently secured through the endothelial tissue at the desired location; and material means substantially inert to body fluids and tissue encasing said lead means and a portion of said electrode means for sealing them from living animal body fluids and tissue.

2. The lead of claim 1 wherein the means for allowing the electrode means to be firmly lodged in and permanently secured through endothelial tissue comprises means for allowing the el'ectrode'means to be firmly lodged in and permanently secured through endocardial tissue.

3. A body-implantable, intravascular lead assembly for use in conjunction with an electromedical device, said lead assembly comprising:

electrically conductive lead means of a cross-section which will fit within a body vessel having electrode means affixed to its distal end and adapted to be electrically connected at its proximal end to a source of electrical power, said electrode means including a tissue piercing portion and further including separate tissue engaging means for allowing said electrode means to be firmly lodged in and permanently secured through the endothelial tissue of selected organs of living animal bodies; means for inserting and guiding said lead means in and through a body vessel to a desired location and position inside the living animal body organ;

means for allowing said electrode to be moved a predetermined distance for firmly lodging and permanently securing said electrode through the endothelial tissue of the selected organ at the desired location; and

means substantially inert to body fluids and tissues for encasing and sealing all of the lead means for the living animal body fluids and tissue except the distal end of the electrode means.

4. A lead assembly as set forth in claim 3 wherein said electrode means includes an electrically conductive barb means for insertion into the tissue.

5'. A lead assembly according to claim 4 wherein said insertion and guide means encases the lead means, said insertion and guide means comprises two separate concentric tubes fitted one within the other, the inner tube being connected to a means adapted for moving it within the outer tube.

6. A lead assembly according to claim 5 wherein said tubes are substantially cylindrical and the lead means is constructed such that it has a substantially cylindrical sleeve means having a cross-sectional diameter greater than the cross-sectional diameter of the inner tube but less than the cross-sectional diameter of the outertube, said sleeve means being positionable within the outer tube and into abuttment with the distal end of the inner tube so as to provide movement of the lead means when the inner tube is moved within the outer tube.

7. A lead assembly as set forth in claim 6 wherein said sleeve means has at least one ridge formed on the outer surface thereof the diameter of said ridge being substantially equal to the inside diameter of said outer tube and forming a seal with the inside wall of said outer tube to prevent the back flow of body fluids into said tubes when said sleeve is within said outer tube.

8. A lead assembly as set forth in claim 6 wherein said means for lodging and securing includes plunger means connected to said inner tube, said plunger means being adapted to forceably move the inner tube and lead means a predetermined distance so that the electrode means of said lead means moves from a position within the outer tube to a position outside the outer tube, said plunger forceable movement being used to firmly lodge and permanently secure the electrode means through the endothelial tissue of the selected body organ.

9. A lead assembly as set forth in claim 8 wherein said plunger means includes engageable first locking means which when in'locked position insures that the barb cannot be inadvertently moved from its position within the outer tube, engageable second locking means which when locked prevents the plunger means from moving the barb further from the outer tube than a position in which it just protrudes from the outer tube, and means for preventing the plunger means from moving the barb more than a predetermined distance when lodging and securing the barb thereby preventing overly deep and injurious barb lodgings.

10. A lead assembly as set forth in claim 3 wherein said insertion and guide means encases the lead means, said insertion and guide means being constructed and adapted to impart sufficient rigidity to facilitate placement of the lead means.

11. The lead assembly of claim 3 wherein the means for firmly lodging and permanently securing the electrode means through the endothelial tissue of a selected body organ comprises means for firmly lodging and permanently securing the electrode through endocardial tissue.

12. A device for inserting a body-implantable intravascular lead with an electrode at one end thereof into .a body vessel and for guiding said lead into a desired location and position within a selected organ of the body, said electrode including a tissue piercing portion and further including separate tissue engaging means for allowing said electrode to be firmly lodged in and permanently secured through endothelial tissue at said selected body organ, said device comprising:

means surrounding said lead means for inserting and guiding said lead into and through a body vessel to a desired location and position inside the selected body organ;

locking means for preventing movement of said electrode beyond a position where it just protrudes from said inserting and guiding means; and

plunger means for allowing said electrode to be moved a distance, greater than said locking means for firmly lodging and permanently securing said electrode through the endothelial tissue of the selected organ at the desired location.

13. A device as set forth in claim 12 wherein said insertion and guide means comprises inner and outer concentric, flexible tubes, said inner and outer tubes encasing a substantial portion of said lead, said outer tube being constructed and adapted to encase said electrode.

14. A device as set forth in claim 13 wherein said plunger means is operatively connected to said inner tube for allowing said inner tube and lead to move a predetermined distance so that the electrode moves from its position within said outer tube so as to be lodged in and permanently secured to said body tissue.

15. A device as set forth in claim 14 further including additional locking means for insuring that said electrode cannot be inadvertently lodged in and secured to body tissue; and said plunger means including means for allowing said electrode to move only a predetermined distance from said outer tube when lodging and securing the electrode in the tissue so as to prevent injury to the tissue.

16. The'device of claim 12 wherein the means for allowing the electrode to be moved a predetermined distance for firmly lodging and permanently securing the electrode through endothelial tissue comprises means for allowing the electrode to be moved a predetermined distance for firmly lodging and permanently securing theelectrode through endocardial tissue.

17. A body-implantable, intravascular lead assembly for use in conjunction with an electro-medical device,

. said lead assembly comprising:

electrically conductive lead means of a cross-section which will fit within a body vessel having electrode means affixed to its distal end and adapted to be electrically connected 4 at its proximal end to a source of electrical power, said electrode means including a tissue piercing portion and further including separate tissue engaging means for allowing said electrode means to be firmly lodged in and permanently secured through the endothelial tissue of selected organs of living animal bodies;

means for inserting and guiding said lead means in and through a body vessel to a desired location and position inside the living animal body'organ;

means for allowing said electrode to be moved a predetermined distance for firmly lodging and permanently securing said electrode through the endothelial tissue of the selected organ at the desired 10- cation; means for allowing a threshold measurement with said electrode means while preventing a firm lodging and permanent securement of said electrode means during said threshold measurement; and means substantially inert to body fluids and tissues for encasing and sealing all of the lead means from living animal body fluids and tissue except the distal end of the electrode means.

Claims

1. A body-implantable, intravascular lead adapted to be connected at its proximal end to a source of electrical energy and permanently secured at its distal end through the endothelial tissue of a living animal body for electrical stimulation thereof comprising: electrically conductive lead means for insertion in and guidance through a body vessel to a desired location and position inside an organ of a living animal body the lead means having a crosssection which will fit within a body vessel; electrode means affixed to the distal end of said lead means and adapted to supply electrical impulses to tissue at a desired location inside the living animal body, said electrode means including a tissue piercing portion and further including separate tissue engaging means for allowing said electrode means to be firmly lodged in and permanently secured through the endothelial tissue at the desired location; and material means substantially inert to body fluids and tissue encasing said lead means and a portion of said electrode means for sealing them from living animal body fluids and tissue.

2. The lead of claim 1 wherein the means for allowing the electrode means to be firmly lodged in and permanently secured through endothelial tissue comprises means for allowing the electrode means to be firmly lodged in and permanently secured through endocardial tissue.

3. A body-implantable, intravascular lead assembly for use in conjunction with an electromedical device, said lead assembly comprising: electrically conductive lead means of a cross-section which will fit within a body vessel having electrode means affixed to its distal end and adapted to be electrically connected at its proximal end to a source of electrical power, said electrode means including a tissue piercing portion and further including separate tissue engaging means for allowing said electrode means to be firmly lodged in and permanently secured through the endothelial tissue of selected organs of living animal bodies; means for inserting and guiding said lead means in and through a body vessel to a desired location and position inside the living animal body organ; means for allowing said electrode to be moved a predetermined distance for firmly lodging and permanently securing said electrode through the endothelial tissue of the selected organ at the desired location; and means substantially inert to body fluids and tissues for encasing and sealing all of the lead means for the living animal body fluids and tissue except the distal end of the electrode means.

5. A lead assembly according to claim 4 wherein said insertion and guide means encases the lead means, said insertion and guide means comprises two separate concentric tubes fitted one within the other, the inner tube being connected to a means adapted for moving it within the outer tube.

6. A lead assembly according to claim 5 wherein said tubes are substantially cylindrical and the lead means is constructed such that it has a substantially cylindrical sleeve means having a cross-sectional diameter greater than the cross-sectional diameter of the inner tube but less than the cross-sectional diameter of the outer tube, said sleeve means being positionable within the outer tube and into abuttment with the distal end of the inner tube so as to provide movement of the lead means when the inner tube is moved within the outer tube.

9. A lead assembly as set forth in claim 8 wherein said plunger means includes engageable first locking means which when in locked position insures that the barb cannot be inadvertently moved from its position within the outer tube, engageable second locking means which when locked prevents the plunger means from moving the barb further from the outer tube than a position in which it just protrudes from the outer tube, and means for preventing the plunger means from moving the barb more than a predetermined distance when lodging and securing the barb thereby preventing overly deep and injurious barb lodgings.

12. A device for inserting a body-implantable intravascular lead with an electrode at one end thereof into a body vessel and for guiding said lead into a desired location and position within a selected organ of the body, said electrode including a tissue piercing portion and further including separate tissue engaging means for allowing said electrode to be firmly lodged in and permanently secured through endothelial tissue at said selected body organ, said device comprising: means surrounding said lead means for inserting and guiding said lead into and through a body vessel to a desired location and position inside the selected body organ; locking means for preventing movement of said electrode beyond a position where it just protrudes from said inserting and guiding means; and plunger means for allowing said electrode to be moved a distance, greater than said locking means for firmly lodging and permanently securing said electrode through the endothelial tissue of the selected organ at the desired location.

16. The device of claim 12 wherein the means for allowing the electrode to be moved a predetermined distance for firmly lodging and permanently securing the electrode through endothelial tissue comprises means for allowing the electrode to be moved a predetermined distance for firmly lodging and permanently securing the electrode through endocardial tissue.

17. A body-implantable, intravascular lead assembly for use in conjunction with an electro-medical device, said lead assembly comprising: electrically conductive lead means of a cross-section which will fit within a body vessel having electrode means affixed to its distal end and adapted to be electrically connected at its proximal end to a source of electrical power, said electrode means including a tissue piercing portion and further including seParate tissue engaging means for allowing said electrode means to be firmly lodged in and permanently secured through the endothelial tissue of selected organs of living animal bodies; means for inserting and guiding said lead means in and through a body vessel to a desired location and position inside the living animal body organ; means for allowing said electrode to be moved a predetermined distance for firmly lodging and permanently securing said electrode through the endothelial tissue of the selected organ at the desired location; means for allowing a threshold measurement with said electrode means while preventing a firm lodging and permanent securement of said electrode means during said threshold measurement; and means substantially inert to body fluids and tissues for encasing and sealing all of the lead means from living animal body fluids and tissue except the distal end of the electrode means.