JPH02185265A - Meltable cover for heart-adjusting electrode - Google Patents

Abstract

PURPOSE: To provide a cover which is dissolvable in the body fluid and thereby exposes a fixed machine element at a specific time after first inserting into a body, by transmitting an electric signal between a selected position of a heart and the base end part of a conductive body through an electrode with a fixing machine element for fixing at a position selected by stinging it into the heart tissue at the selected position and a position and a conductive body. CONSTITUTION: A transplantable and securely fixable device such as an intracardiac lead 16 is inserted, for instance, into a vascular system such as a subclavian artery blood vessel or a head artery and gradually moved until a distal end part 62 reaches the selected cardiac chamber. The transplanted lead transmits an electric signal between the selected position of the heart and the base end part of the lead to monitor the electric motion of the heart at the selected position and carries a pulse from a pulse generator connected to the base end part of the lead to the selected position. To transmit the electric signal, a conductive body shown as a double winding coil 18 made of a nickel alloy is fitted. The coil gives only the minimum stress to the conductive body to give the maximum flexibility so as to match it with the shape of a blood vessel.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lead wire for diagnosis and long-term treatment of heart disease, and more particularly to a fixed lead wire in which internal electrodes have fixed elements. 11 Jl.

BACKGROUND OF THE INVENTION The utility of cardiac pacing leads is well recognized both for transmitting pulse stimulation signals from a pacemaker to the heart and for monitoring the electrical activity of the heart from outside the body. Many such S-wires are sufficiently flexible and have a small diameter for intravenous introduction into the intracardiac space, allowing the electrode at the distal end of the wire to be implanted in the endocardium. This is done to secure the conductor. For this purpose,
Typically helical coils, barbs and other fixed elements are provided as part of the electrode.

Such fixation elements penetrate the endocardium, e.g.
The S1 must be sharp enough to prevent the electrode from detaching due to contraction of the layer. During the critical period II, usually between 3 and 12 weeks, before the growth of the fibrillation of the transplant model is complete, the fixation element is used to maintain substantially all of the electrodes in the selected position. Must have the power of the forest.

Given these conditions, 1 valid fixed III
It is not surprising that the elements become entangled within the veins, heart valves, or other tissues encountered during intravenous insertion.

The above problem has given rise to numerous solutions.

For example, U.S. Pat. It shows a sleeve. Granted to Subing dated August 11, 1981] 1 Patent No. 4.28
No. 2.885, the protective core is surrounded by a helix and is movable axially relative to the helix. A wire attached to the core extends through the conductor so that, after insertion of the conductor, the core can be pulled out and pulled to expose the helix. U.S. Pat. No. 4,146,036, issued March 27, 1975, to Dutcher et al., discloses an extendable and retractable body surrounded by a helix.

Another solution is to make fixed elements movable. For example, U.S. Pat. being done. October 1974
No. 3,84 for U.S. Patent granted to Bolduc, dated May 29
No. 4.292 shows a plunger external to the body which is movable to push the barbed tops outward after releasing the two locking mechanisms. U.S. Pat. No. 4,258,724 issued to Barratt on March 31, 1981, discloses a platinum piston movable to push a barb-like fixture beyond the end of a tubular 'i' pole. It is shown.

While satisfactory in their construction, such devices undesirably require that the wires used in them have a large diameter. These require additional tools, such as a screwdriver with a pierce to rotate the spiral. Furthermore, such devices are often overly complex, reducing reliability and creating the potential for current leakage between the bipolar conductors.

[Problems to be Solved by the Invention] Accordingly, it is an object of the present invention to provide a smooth rounded cover for the fixation element of an endocardial electrode to facilitate intravenous insertion of the electrode. be.

Another object of the invention is to provide such a cover that is dissolvable in body fluids, thereby exposing the fixation element at a specific time after it has first been applied to the body.

Furthermore, it is an object of the present invention to provide a simple and three-way mechanical covering of the fixation mechanism during intravenous insertion of a pacing electrode with a fixation element without requiring longitudinal relative movement between the electrode and the fixation element. It is to provide stomach fillings.

SUMMARY OF THE INVENTION To achieve the above and other objects, an intravascular lead implantable within the body of a patient is provided. The lead wire includes an electrode that pierces tissue within the heart at a selected location and holds an anchoring element for securing the electrode at the selected location. The lead includes one or more flexible electrical conductors and one or more flexible biocompatible dielectric sheaths extending over and surrounding substantially the entire length of the electrical conductors. Contains. A coupling device electrically and mechanically couples the electrode to the distal end of the electrical conductor such that the electrical conductor and electrode transmit electrical signals from the selected location to the proximal end of the lead. A biocompatible cover surrounds the fixation element and facilitates intravascular movement of the electrode. The cover is dissolvable in body fluids and allows insertion of the lead and electrode into the vessel, at least at selected locations, before the cover is sufficiently dissolved to expose the fixation element and allow penetration. (2) The thickness N11' is selected to allow at least a predetermined minimum time for positioning one pole in the vicinity of N11'.

Mannitol and other saccharide derivatives have been found suitable for forming covers, and these can be used to place the immobilized element in a beaker containing mannitol or other cover components. It can be produced by oil immersion at a temperature -b slightly above the melting point. The fixed element is taken out and l! It is cooled together with the part of the material that is J W. Alternatively, the cover can be molded as a capsule, with a hole formed in the turnip to accommodate the fixing element. The fixation element is then placed into the hole and adhesive is used to bond the cover to the electrode.

Another feature of the invention is an apparatus that facilitates intravascular insertion of cardiac pacing electrodes. The device includes a biocompatible non-heat generating cover that substantially surrounds the fixed element of the electrode. This cover is dissolvable in body fluids and is placed inside the patient's body before the cover dissolves sufficiently to expose the fixation element and allow the fixation element to be penetrated at the selected location within the body. The thickness is selected to provide at least tl+a predetermined time for insertion of the north pole into the vessel at least proximate to the selected location.

As another feature of the invention, a method is proposed for coating a fixed G1 element on a body-implantable electrode, which method comprises: (b) selecting a biocompatible, non-pyrogenic material with a high melting point and heating it to a temperature slightly above its melting point; (b) holding the immobilized element of the body-implantable electrode at said temperature; (c) immersing said material in i8 liquid;
(d) removing the fixation element from the solution along with the first portion of material attached thereto and allowing them to cool for a sufficient period of time for said first portion of B1 to at least partially solidify; immersing the fixation element and said first part in said solution for a sufficient time to allow subsequent parts of said material to adhere to said first part; (e) said fixation element, said first part and subsequent parts; The steps include removing the b from the solution and allowing the b to cool to ambient humidity.

Steps (d) and (8) can be repeated until the thickness of the cover is sufficient to obtain the desired dissolution time.

The cover according to the invention may be preformed or dip coated to form a smooth, blunt distal end for the mating leads, and as the fixation element moves towards the heart.
This allows for rapid intravenous insertion of the lead without the risk of snagging the vessel, tearing the vessel, or causing other vessel or other tissue damage. After the electrode reaches the selected ventricle, the cover dissolves sufficiently to expose the fixation element and prepare it for puncturing the endocardium.

There are many materials suitable for the cover, including various salts and derivatives of polyvinylpyrrolidone and the aforementioned sugars, and furthermore, by controlling the thickness of the cover a wide range of dissolution times can be obtained. Yes, a particular cover can be adjusted to the expected dissolution time for a particular procedure. Furthermore, improved control over cover dimensions, thickness, and surface area is further refined by preformed capsules.

BRIEF DESCRIPTION OF THE DRAWINGS For a further understanding of these and other features and advantages of the present invention, reference is made to the following detailed description and drawings.

Referring now to the drawings, FIG. 1 shows an implantable and positively identified intracardiac lead 16. The device, such as lead 16, is inserted mold-wise into a vessel, such as the supraclavicular artery or the cephalic vessel, and is progressively moved until the distal end reaches the selected ventricle. Once the distal end is positioned at the selected location, the proximal end of the lead, which is still external to the body, is manipulated to implant the distal end into the endocardium. The implanted yJ wire transmits electrical signals between selected locations in the heart and the proximal end of the lead to serve one or both of two purposes.

The pulse generator also monitors the electrical activity of the heart at a selected location and delivers pulses to the selected location from a pulse generator (not shown) connected to the proximal end of the lead. be.

To transmit electrical signals, an electrical conductor, shown in FIG. 1 as a double-wound coil 18 made of a nickel alloy, is provided. This coil is 13. It is designed to give the ff1 body maximum flexibility so as to conform to the shape of the blood vessel while applying minimal stress.

At the distal end of the conductor is an electrode 20 that is electrically and mechanically coupled to the coil 18 by a platinum alloy constrictor 22, with a flexible dielectric sheath 24 surrounding the coil and the constrictor tube. There is. A suitable material for this sheath is silicone rubber.

The electrode 20 is porous and has a screen 26 formed from a platinum alloy. The screen 26 assists in long-term fixation, whereby the connective tissue of the fibers and the bamboo are interfused with the screen to firmly fix the electrode 20. However, it takes several weeks for the tissue to become enveloped, and it is important to install a device that securely secures the far FA end of the conductor during the period immediately following implantation.

For this purpose, a fixed helix 28 of platinum alloy is provided. The helix 28 has a sharp tip at its distal end that allows it to easily pierce the endocardium. After the initial penetration, the helix is manipulated from the proximal end of the lead 16, rotated clockwise, and further penetrated into the tissue to a position that firmly secures the electrode 20 at the designated endocardial location. It will be passed.

A problem associated with such helices 28 is that their sharp tips can become lodged and become entangled with blood vessel walls, venous valves, or heart valves. Therefore, it is suggested that physicians using the lead 16 typically rotate the helix counterclockwise to pull the sharp tip of the helix away from the mating tissue to minimize the possibility of entanglement. Otherwise, protection devices such as those described above would be used.

FIG. 2 shows a conductor 16 having a cover or end 30 attached to the distal end 14 in accordance with the present invention. This end 30 is solid and rigidly attached to the distal ends of the helix 28, screen 26, and sheath 24. However, the exact surface shape requires that the end 30 be smooth, rounded and not sharp, and that the fixed helix, especially its sharp tip 32,
It is less important than completely surrounding the fixation helix 28 to protect the I canal and other tissues.

The end portion 30 is made of an insulating, biocompatible, non-pyrogenic material. The material must also be soluble in body fluids (particularly blood) within a temperature range that includes normal body temperature (37°C). Furthermore, the material of the 3° end should retain its structural form in an environment of body fluids at approximately normal body temperatures and should not undergo plastic and elastic deformation as it melts. Typically, the requirements for such a structural configuration are such that the melting point of the end is substantially higher than the normal body 4, in fact 60°C or higher.
If it is fA degree, it will be satisfied.

In one example, end 30 was formed from mannitol having the chemical formula C6H1406. Mannitol has a melting point of about 167°C, and 1 gram of mannitol dissolves in about 5.5 milliliters of water.
i1 degrees becomes even greater as the water gets hotter. The mannitite within the glass was first heated to a temperature of 177°C to 182°C, slightly above its melting point, and held at this temperature. The distal end N1 of the conductor 16 was briefly immersed in a solution of mannitol and withdrawn. spiral body 28
A portion of the mannitol was allowed to pass through to form a core portion 34 as shown in FIG. The spiral body 28 and core portion 34 taken out from the beaker were subjected to cooling IJ1 for a sufficient period of time to solidify the core portion. This cold moon 1 took about 5 seconds.

Following this cooling, the distal end of the wire was dipped again into the mannitol melt and removed after about 1 second. The second portion of the mannitol melt rigidly bonded to the core portion 34, the helix 28 and the screen 26 was sufficient to cover the core portion to form the end 30 shown in FIG. 2. The spheroidal end shape results from the natural surface tension of the mannitol melt as it solidifies. The ends thus formed were dissolved in water heated to about 38° C. for about 3 minutes.

Repeated testing of this example yielded a satisfactory S-line edge δ;i. These results showed that the exact temperature of the mannitol melt is not important as long as it is kept in liquid form and slightly above the melting point.

11 [as in each immersion] δ coating period should be sufficient for subsequent layers of mannitol to adhere firmly, yet not so long as to dissolve the mannitol already solidified on the S line, but not too long. Finally, the number of dip coatings required is not critical; the number of dip coatings required is largely a function of the desired end dimensions and is substantially the same as described above in end designs. Soaking 1! It can be more than just a cover.

The dissolution time of the end 30 in body fluids is primarily controlled by the material, surface area and thickness of the end, with increased dissolution time being obtained by increasing the thickness of the end if desired. The primary consideration is that the end 30 is sufficiently sized to ensure that the lead 16 is directed into the selected ventricular vein before the helix 28, particularly its tip 32, is exposed. It is. It is also a consideration that within a reasonably short period of time after insertion, the end 30 is completely dissolved to expose the helix 28 and allow for implantation of the electrode 20.

Although the above examples include mannitol, derivatives of other sugars that are stable at temperatures below 60° C. are also suitable substitutes, such as dextrose, '/rubose, saccharose and glucosamine. . Salts such as thorium chloride, potassium chloride and 1Mm sodium can also be used. Yet another suitable component is polyvinylpyrrolidone (PVP). These materials are suitable as well as non-helical fixed elements.

The dipping method described above, when used to form the end 30, tends to entrap air, which can expand upon heating and create undesirable air bubbles within the end. In such cases, it is advantageous to control the extent to which the remote end of the conductor is immersed in the component melt. For example, FIG. 4 shows a conductor 36 with an end 40 generally surrounding a fixed helix 42. As shown in FIG. The end portion 40 is the sheath body 4
4, the base end 46 of the screen 48 is exposed. As a result of this controlled immersion, air escapes through the proximal end 46, which later facilitates oxidative sterilization of the distal end of the wire.

To improve control over the size and shape of the dissolvable end, the end 50 of the conductor 52 of FIG. 5 is formed by melt casting or injection molding of the components. This end is the sheath body 5
The spiral body 54 and the screen 56 are surrounded so as to be in contact with the spiral body 54 and the screen 56 . The profile along the side of the end is straight, as shown at 60, but a rounded, blunt distal end 62 is retained. This allows the diameter of the end to be reduced to the nominal lead diameter to further facilitate intravenous insertion.1. 'E.

Another method of controlling the size and shape of the ends is to preform the ends by casting or injection molding. FIG. 6 shows a conductor 864 having a screen 65 and a locking helix 66 secured to the conductor surrounded by a sheath 68. FIG. Surrounding the helix and screen is a preformed end-beat capsule 70 secured at 72 to the sheath 68 using adhesive. Such adhesives may be dissolved in themselves in the case of mannitol, heated syrups of fructose and sucrose that solidify on cooling, or syrups of other sugars (mannitol, sorbyl, etc.). I can do it. A large diameter hole 74 is formed in the capsule 7o to accommodate the screen 65, and a large deep cylindrical hole 76 accommodates the helix 66.

As shown in dashed lines at 77 and 78, the holes 76 can be projected if desired to give the capsule 70 a substantially uniform thickness. If desired, one or more 17110 may be formed as shown at 79 to facilitate sterilization and increase the surface area of the capsule exposed to bodily fluids during lead insertion.

Preformed ends offer significant advantages in young applications, although they require adhesives that are not needed with dip coating or direct molding. First, it provides the greatest control+ability over the size and shape of the end, and relatively accurate dissolution times can be obtained by appropriately selecting the end components and end width. The conformity achieved between multiple edges makes preformed edges a desirable option for mass production. Preformed ends also require fewer end components.

In particular, components are not provided if they are not needed, ie in the cylinder bounded by the fixed helix. Such factors contribute to more predictable dissolution times and material savings. Preformed ends can also be installed or replaced in the field. At the end, a component that cannot be melted due to thermal instability but has a melting characteristic of a given ψ is compressed or molded to form the end 7.
It can be formed at an end such as 0. Examples of such components are lactose, lecithin in combination with other 0131s and glucosamine.

In FIG. 7, a differently preformed end or capsule 80 is mounted onto the securing helix 84 and screen 86 of the conductor 82. In FIG. A helical hole 88 sized and shaped to receive a helix 84 is formed in the end 80 and secured to the end 80S conductor 82 by rotating the conductor 182 clockwise relative to the helix of the end 80. I can do it. When attached in this manner, the end 80 is adhesive-free, and no adhesive is required to connect the end to the sheath 90.

Although the forming tool 92 is shown in FIGS. 8 and 9,
The forming tool is a block of aluminum and includes two opposing portions 94 and 96 held by socket head screws 98 and 1°O. part 9
The opposing wall portions of 4 and 96 have been cut away to form cavities 102, 104 and 106 when these portions are attached to each other as shown. A spacing strip, indicated by 108, maintains a small gap between these portions 94 and 96, preferably about 0.13 am (about 0.005 inch).

Although the shape of these cavities can be formed to different dimensions corresponding to ends of different selected dimensions, here the cavities are made substantially the same. For example, empty space 104
includes an end molded segment 110 J') and an upper chamfered segment 112. The end molded segment 110 has a rounded base to form the desired cylindrical sides and the desired blunt end, while the beveled L segment 112 has a rounded base to form the desired cylindrical sides and the desired blunt end, while the chamfered L segment 112 has a rounded base to form the desired cylindrical sides and the desired blunt end. It also serves as a temporary catchment container for excess melting/molding material.

Forming tool 92 is used to control the direction and shape of the dissolvable end formed by the dipping method described in connection with FIGS. 2-4.

More specifically, the distal end of the conductor is immersed in a solution of 7 nits, allowed to cool and then dipped again; this method does not produce an end larger than the desired size. repeated a sufficient number of times. Next, by heating the forming tool 92 to a desired temperature, preferably slightly above the melting point of mannitol, the edge formed by the dip 101 momentarily snaps into any of the cavities 102-106. It is inserted into the desired one and then rapidly withdrawn, the desired time being in the selected cavity being a fraction of a second.
That's it. During this brief insertion, the heated cavity walls melt the excess mannitol, after which the melt is drained through the gap provided by the spacer 108 and removed. A portion of the excess Mannilla j. lysate is collected in a 1 m simply beveled segment 112 before being discharged.

Although not required, the ends may be rotated slightly about the vertical @ line during insertion to further ensure fixation of the desired cylindrical sides and blunt ends.

Whether formed by dip coating, direct molding or separately molded for subsequent installation,
The dissolvable ends of the present invention allow for safer and less traumatic implantation of cardiac pacing leads.

The end dissolves as it is moved toward the heart through the selected blood vessel, but remains in place in a fixed helix or other until the electrode is near the selected location along the endocardium. molten H at a rate slow enough to close off the exposure of the fixed elements. The virtually smooth rounded blunt end facilitates insertion of the 81 wire within the vessel. The thickness and components of the end are selected according to the expected insertion time and are carried out with particularly good precision in the case of preformed ends or capsules. Therefore, the correct place v!
After a short period of time, a fixation spiral or other fixation element is normally manipulated from outside the body to fix the electrode.

[Brief explanation of the drawing]

FIG. 1 is a side cross-sectional view of the distal end region of an implantable fixed secure t'c intracardiac lead. 2 is an enlarged side view of the conductor of FIG. 1 provided with a dissolvable cover according to the present invention; FIG. FIG. 143 is an enlarged side view similar to FIG. 2, showing the cover in an intermediate step of formation. FIG. 4 is a side view of the conductor provided with the cover of the second embodiment. FIG. 5 is a side elevational view of a third embodiment covered conductor including a seven-fold molded end. FIG. 7 is a side view of the 3# wire provided with a cover including preformed ends as shown in FIGS. 6 and 7, respectively. 8 and 9 are top and side views, respectively, of a tool used to form a meltable cover according to the present invention. 16.36.52.64.82...Intracardiac S line 18.
... double-wound coil 20 ... electrode 22 ... constriction tube 24, 44. 58. 68°26.48.56, 65°28, 42.54. 66°30.40,50. 70°32...Tip 34...Core portion 46...Proximal end 62...Distal end 70.80...Capsule 74.79...Opening arrow...Cylindrical hole 88... ...Spiral hole 92...Forming tool 94,96...Opposing portions 102, 104, 106...Vacancy 108...Spacer piece 110...End forming segment 112...Chamfered segment. 9o...It electrical sheath body 6...Screen 84...Fixed spiral body 80...End part

Claims (1)

[Scope of Claims] (1) An intravascular lead implantable within a patient, having a fixation element for piercing tissue within the heart at a selected position and fixing it at the selected position. an electrode, a flexible electrical conductor, a flexible biocompatible dielectric sheath surrounding said electrical conductor along substantially the entire length thereof, and said electrode at a remote end of said electrical conductor. a coupling device that electrically and mechanically couples the electrical conductor and the electrode to transmit electrical signals between the selected location and the proximal end of the electrical conductor; a biocompatible cover surrounding the electrode to facilitate intravascular movement of the electrode, the cover being soluble in body fluids and stable in the surrounding environment;
has a melting point of 0° C., has a tendency to retain its structural form in an environment of body fluids at approximately body temperature, and before the cover has sufficiently melted to expose the anchoring element; having a thickness selected to allow at least a predetermined minimum time for inserting the lead and the electrode into a vessel and positioning the electrode at least generally proximate to the selected location; The cover contains substantially at least the following components: mannitol, purified glucose (de
xtrose), sorbose, sucrose, sodium chloride, potassium chloride, and sodium carbonate; 2. The intravascular lead of claim 1, wherein the cover consists essentially of mannitol. 3. The intravascular lead of claim 1, wherein said cover comprises one of said components. (4) a preformed capsule in which the cover has a device forming a hole for accommodating the fixing element, and joining the capsule to the electrode such that the fixing element is inside the hole; The intravascular lead of claim 1, further comprising a device for: 5. The intravascular lead of claim 4, wherein the bonding device includes an adhesive. (6) The intravascular lead wire according to claim 4, wherein the fixation element is a helix, and the hole has a helical shape corresponding to the shape of the helix. The intravascular lead of claim 1, wherein: (1) the electrode includes an electrically conductive porous electrode portion proximate the fixation element. 8. The intravascular lead of claim 7, wherein the cover overlies a portion of the porous electrode portion, exposing the remainder of the portion. (9) A device for facilitating intravascular insertion of a body-implantable device, comprising: a body-implantable device; a fixation element at a distal end of the device; a biocompatible, non-pyrogenic covering surrounding the body, having a melting point of at least 60°C, stable in the surrounding environment, soluble in body fluids, and capable of forming a structural form within the body fluid environment at approximately body temperature. and the remote area before the cover dissolves sufficiently to expose the fixation element and permit penetration of the fixation element into body tissue at the selected location. having a thickness selected to allow at least a predetermined period of time for intravascular insertion of the distal end at least proximate to a selected location within the body of the organism within the vascular end; , wherein said cover consists essentially of one of at least the following components: mannitol, purified glucose, sorbose, sucrose, sodium chloride, potassium chloride, and sodium carbonate. 10. The apparatus of claim 9, wherein the cover consists essentially of mannitol. 11. The apparatus of claim 9, wherein said cover consists essentially of one of said components. 12. The device of claim 9, wherein the implantable device includes a cardiac pacing electrode. (13) the cover is formed by dip coating a material comprising the cover in liquid molten form onto the stationary element so as to solidify in surrounding relation to the element; 13. Apparatus according to claim 12. (14) the cover includes a preformed capsule and a device for forming an aperture for accommodating the fixation element, and a device for facilitating intravascular insertion couples the capsule to the electrode. 13. The apparatus of claim 12, further comprising means for causing the fixation element to be received within the bore. (15) Claim 14, wherein the fixed element is a spiral body, and the hole has a spiral shape corresponding to the shape of the spiral body.
The device described. 16. The device of claim 14, wherein the electrode includes a porous screen, and the capsule is adapted to cover a majority of the screen and expose the remainder of the screen when coupled to the electrode. . (17) the electrode includes a conductive porous screen disposed proximate the stationary element, the electrode being selectively dip coated to cover the stationary element and a portion of the screen; 13. Apparatus according to claim 12, adapted to expose the remainder of the screen. (18) A method of coating a fixed element of a body-implantable electrode comprising: (a) a biocompatible, non-pyrogenic material that is soluble in body fluids and has a melting point substantially higher than normal body temperature; Select
heating said material to a temperature slightly above its melting point; (b) immersing a fixation member of a body-implantable electrode in a solution of said material held at said temperature; and (c) said fixation. removing the component from the solution along with the initial portion of the material attached thereto and allowing them to cool for a sufficient period of time to allow the initial portion to at least partially solidify; (d) immersing said securing member and said portion of material in said solution after said cooling for a sufficient period of time to allow subsequent portions of said material to adhere to said first portion; and (e) said securing member. , removing the first portion and subsequent portions from the solution so that they may be cooled to ambient temperature. (19) repeating steps (d) and (e) until the combined thickness of the first portion and all subsequent portions is at least a predetermined value; 19. The method according to claim 18. (20) providing a device for defining a cavity having a selected size and shape, heating a wall forming the cavity to a preselected temperature at least equal to the melting point of the material; Momentarily inserting the end into the cavity to remove excess material such that the combined thickness is at least the preselected value to form an end that is larger than the cavity. 19. The method of claim 18, further comprising the steps of melting and draining the excess material from the cavity. (21) In an intravascular lead implantable within a patient, an electrode having a fixing element for piercing intracardiac tissue at a selected position and fixing the electrode at the selected position; a flexible, biocompatible, dielectric sheath surrounding the electrical conductor along substantially the entire length of the electrical conductor; a coupling device mechanically joined to cause the electrical conductor and the electrode to transmit electrical signals between the selected location and the proximal end of the electrical conductor; and a coupling device that facilitates intravascular movement of the electrode. a biocooperative cover surrounding the fixed element so as to be soluble in body fluids, stable in the surrounding environment, having a melting point of at least 60°C, and capable of dissolving in the body fluid environment at approximately body temperature; intravascular insertion of the electrode and at least the selected said cover has a thickness selected to allow at least a predetermined minimum time for positioning in the vicinity of a location, said cover immersing said fixation element into a liquid melt of material comprising said cover. an intravascular lead adapted to be formed by dip coating.