Device for slitting introducers for pacemaker electrodes

Apparatus for implanting pacemaker electrodes whose proximal ends have enlarged plugs for attachment to pacemakers has a one-piece unslotted and unweakened tubular introducer of somewhat flexible material whose front end portion is inserted into the subclavian vein of the patient with assistance from a guide wire and a dilator. The dilator and the guide wire are thereupon extracted from the introducer so that the latter provides an unobstructed passage for implantation of a pacemaker electrode. The exposed section of the implanted electrode between the rear end of the introducer and the plug is then engaged by the trough-shaped elastically deformable portion of a severing device whose knife extends radially of the exposed section of the electrode and severs the introducer longitudinally while the latter is being pulled in a direction to extract its front end portion from the vein. The rear end of the introducer is formed with wing-shaped handgrip portions which facilitate the pulling of introducer in a direction toward the cutting edge of the knife and the exertion of a simultaneous lateral pull upon the rear end of the introducer so that the latter is automatically separated from the exposed section of the electrode simultaneously with longitudinal slitting by the cutting edge.

BACKGROUND OF THE INVENTION 
The present invention relates to improvements in apparatus for implanting 
pacemaker electrodes, catheters and similar slender elongated objects into 
the circulatory systems or cavities of animal bodies, especially human 
patients. 
The article "Permanente Herzschrittmacherversorgung mittels perkutaner 
Implantationstechnik" on pages 489-494 of the German-language publication 
entitled "Herz/Kreislauf 10" (Nov. 10, 1978) describes an apparatus which 
employs a syringe with a hollow metallic needle serving for introduction 
of a guide wire into a selected vein (e.g., into the subclavian vein) so 
that the guide wire can facilitate the insertion of a plastic sleeve- or 
hose-like introducer with assistance from a rigid dilator. Once a portion 
of the introducer is properly inserted into the vein, the guide wire and 
the dilator are extracted so that the introducer provides an unobstructed 
passage for implantation of a pacemaker electrode, a catheter or a similar 
elongated object which is to be permanently or temporarily implanted in 
the body. In a final step, the introducer is severed longitudinally so as 
to permit its separation from the implanted object. The guide wire is 
normally a so-called Seldinger spiral which is caused to pass through the 
hollow needle of the syringe as soon as the tip of the needle has 
penetrated into the selected vein and as soon as the cylinder and piston 
of the syringe are detached from the needle. The convolutions of the 
Seldinger wire allow for convenient introduction of the front end portion 
of the introducer and of the hollow cylindrical dilator therein into the 
vein by rotating the dilator and the introducer around the wire. The guide 
wire and the dilator are thereupon withdrawn from the vein and from the 
introducer while the corresponding part of the body is monitored by an 
X-ray machine. 
Extraction of the introducer upon completed implantation of a pacemaker 
electrode and its separation from the implanted object present problems 
because the exposed proximal end of the implanted pacemaker electrode 
carries a plug by means of which the electrode is connectable to a 
pacemaker. The dimensions of the plug (as measured radially of the 
electrode) exceed the inner diameter of the introducer so that the latter 
cannot be slipped over the plug. Consequently, the introducer must be 
severed longitudinally and/or otherwise in order to allow for its 
separation from the implanted electrode without the need to remove the 
plug or to attach the plug to the electrode upon completed implantation 
into the body of the patient. The aforementioned German-language 
publication offers two solutions, namely to separate the plug from the 
implanted electrode or to use shears or a similar cutting implement in 
order to slit the introducer longitudinally so as to allow for its 
separation by moving it radially of and away from the exposed section of 
the implanted electrode. 
U.S. Pat. Nos. 4,243,050 and 4,345,606 to Littleford propose to employ a 
tubular introducer which is formed with a longitudinally extending slot 
prior to putting it to actual use. This reduces the problem of separating 
the introducer from the exposed section of the implanted electrode without 
removing the plug but such types of preslotted sleeve-like introducers 
present many other equally serious or even graver problems. Thus, the 
introducer should exhibit at least some flexibility so that it can conform 
to the anatomy of a patient in the region where a portion thereof is 
introduced into the body for the purpose of establishing a path for 
implantation of a pacemaker electrode or the like. The longitudinally 
extending slot weakens the introducer so that the latter is likely to 
exhibit excessive flexibility and to actually buckle prior to or during 
implantation of an electrode or the like. This necessitates extraction of 
the introducer and restarting of the entire procedure, i.e., puncturing of 
the vein with the needle of a syringe, insertion of a guide wire, 
insertion of an introducer and a dilator, and extraction of the dilator 
and guide wire upon completed insertion of the front end portion of the 
introducer into the vein. On the other hand, if the preslotted introducer 
is relatively stiff so that it cannot undergo excessive flexing in spite 
of the longitudinally extending slot therein, the material of the 
introducer is likely to damage the relatively soft layer of insulating 
material which surrounds the pacemaker electrode. In other words, the 
rigidity of the introducer cannot be increased at will because an 
excessively rigid introducer is not likely to assume an optimum shape for 
implantation of an electrode or the like, and such rigid introducer is 
likely to damage the implanted object as a result of contact between the 
edges bounding its slit and the insulating material on the electrode. 
U.S. Pat. No. 4,243,050 to Littleford also discloses an introducer having 
two slotted tubes which are partially telescoped into each other. When the 
inner tube is completely withdrawn from the outer tube, each of these 
tubes can be readily separated from the exposed section of a pacemaker 
electrode because its longitudinally extending slot has or can have a 
width at least matching the diameter of the electrode. The just discussed 
proposal exhibits the drawback that the introducer is quite expensive and 
complex as well as that a lengthy manipulation is necessary to separate 
its components from the implanted object. Furthermore, the electrode 
cannot be reliably held while the inner tube of the two-piece introducer 
is fully extracted from the outer tube as well as that large quantities of 
body fluid can escape by way of the introducer during separation of its 
components from the exposed section of the electrode. Moreover, if the 
slot in the one and/or the other component of such composite introducer is 
too narrow, the person in charge must use shears, a scalpel or another 
severing implement to separate the respective component from the implanted 
object. The shears and scalpel are likely to damage the insulation on the 
implanted electrode. 
German Offenlegungsschrift No. 23 43 094 of Nordstrom discloses an 
introducer with two longitudinally extending weakened portions which allow 
for separation of a longitudinally extending strip therebetween. Such 
introducers are expensive and their flexibility cannot be controlled with 
a requisite degree of accuracy. 
German Gebrauchsmuster No. 71 03 368 of Braun discloses an apparatus for 
implantation of a flexible catheter which also employs an introducer with 
two longitudinally extending weakened portions. 
German Gebrauchsmuster No. 79 28 830 of Technological Supply, S. A. 
discloses an introducer which is slotted all the way from end to end prior 
to actual use. 
OBJECTS AND SUMMARY OF THE INVENTION 
An object of the invention is to provide novel and improved means for 
facilitating separation of an introducer, which is devoid of a 
longitudinally extending slot and/or of one or more longitudinally 
extending weakened portions, from the exposed section of an implanted 
object. 
Another object of the invention is to provide a novel and improved 
introducer severing device for use in the above outlined apparatus. 
The invention provides a severing device for use with an apparatus for 
introducing an elongated slender object into an animal body, particularly 
for introducing a pacemaker electrode or a catheter into a vein of a 
patient. The apparatus comprises a severable tubular introducer 
(preferably in the form of a reasonably rigid but still flexible sleeve 
made of a suitable synthetic plastic material) the first end portion of 
which can be caused to extend into the body in a conventional manner, 
e.g., by employing a syringe, a wire guide and a dilator and by thereupon 
withdrawing the dilator and the wire guide. The second end portion of the 
introducer is located outside of the body which receives the first end 
portion so that an elongated slender object can be inserted or implanted 
into the body by way of the second end portion, thereupon by way of a 
series of intermediate portions and ultimately by way of the first end 
portion of the introducer until a first section of the thus inserted 
object extends beyond the first end portion (e.g., all the way into the 
heart of a patient who is to receive a pacemaker) and a second section of 
the inserted object extends outwardly beyond the second end portion of the 
introducer. The improved severing device for the introducer comprises a 
supporting portion which can be caused to releasably engage the second 
section of the inserted object and a knife which is provided on the 
supporting portion and has at least one cutting edge facing the second end 
portion of the introducer when the supporting portion engages the second 
section of the inserted object so that the introducer is automatically 
severed longitudinally in response to its movement in a direction to 
extract the first end portion from the body and to advance the second end 
portion, successive intermediate portions and ultimately the first end 
portion of the introducer toward and against the cutting edge or cutting 
edges. 
The supporting portion of the severing device is preferably elongated for 
more convenient manipulation and application to the second section of the 
inserted object and extends beyond the knife in at least one direction as 
considered longitudinally of the second section of the inserted object. 
Such supporting portion can be formed with a longitudinally extending slot 
so that it can be placed around the second section of the inserted object; 
to this end, the supporting portion is preferably a substantially 
trough-shaped part having a C-shaped or U-shaped cross-sectional outline. 
The supporting portion is preferably deformable so that it can be moved 
into desired frictional engagement with the second section of the inserted 
object. To accomplish this object, the supporting portion consists (at 
least in part) of a suitable elastomeric material. Furthermore, the 
supporting portion can be configurated so as to conform to one or more 
fingers of the hand which is used to hold the supporting portion in 
engagement with the second section of the implanted object. For example, 
the supporting portion can be formed with one or more flutes or analogous 
recesses. The knife of the severing device is preferably located between 
the second end portion of the introducer and the flute or flutes of the 
supporting portion when the latter engages the second section of the 
inserted object. 
The supporting portion of the severing device preferably further comprises 
a terminal which is receivable in the second end portion of the introducer 
to at least partially stem the outflow of body fluids (particularly blood 
from a vein) by way of the introducer while the first portion of the 
introducer extends into the body. Such terminal can constitute a 
substantially conical tip which is preferably adjacent to the cutting edge 
of the knife. 
The second end portion of the introducer is preferably provided with at 
least one substantially wing-like handgrip portion which can be grasped by 
fingers to pull the second end portion in a direction toward the cutting 
edge to thereby extract the first end portion from the body and to 
simultaneously split the introducer longitudinally in a direction from the 
second toward the first end portion. In accordance with a presently 
preferred embodiment, the second end portion of the introducer has a 
plurality of handgrip portions, most preferably two handgrip portions 
which are normally located substantially diametrically opposite each other 
and extend radially outwardly from the second end portion. At least one of 
such plurality of handgrip portions is preferably movable relative to the 
other handgrip portion(s) into close or immediate proximity of another 
handgrip portion to form therewith a relatively large handle which can be 
engaged by the fingers of a person preparatory to and during pulling of 
the second end portion in a direction to extract the first end portion 
from the body. The handgrip portions are preferably integral parts of the 
introducer. At least one of the handgrip portions can be provided with at 
least one flute or an analogous recess for reception of a portion of a 
finger of the hand which is used to move the movable handgrip portion 
relative to another handgrip portion. The handgrip portions which form the 
aforementioned handle preferably have substantially flat abutting edge 
faces. 
The novel features which are considered as characteristic of the invention 
are set forth in particular in the appended claims. The improved severing 
device itself, however, both as to its construction and the mode of 
utilizing the same, together with additional features and advantages 
thereof, will be best understood upon perusal of the following detailed 
description of certain specific embodiments with reference to the 
accompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a syringe with a hollow metallic needle 3 which is in the 
process of being inserted into the subclavian vein 2 (see FIG. 2) of a 
patient. The purpose of the needle 3 is to facilitate implantation of a 
pacemaker electrode 1 (see FIG. 7), a catheter or another elongated 
slender object into the circulatory system, especially into the heart, of 
the patient. The needle 3 punctures the vein 2 in a manner as shown in 
FIG. 2 (so that its tip extends into the vein) and is then detached from 
the remainder of the syringe so that its rear end portion is accessible 
for insertion of an elongated flexible guide wire 4 in the direction 
indicated by the arrow Pf1 (see FIG. 3). The needle 3 and the guide wire 4 
constitute two conventional constituents of the apparatus which is used to 
implant the electrode 1 into the body of the patient. The guide wire 4 can 
constitute a so-called Seldinger spiral which can be flexed (see FIG. 3) 
so that its front end portion can penetrate into the vein 2 beyond the tip 
of the needle 3. In the next step, the needle 3 is extracted from the body 
of the patient in the direction of arrow Pf2 (see FIG. 4) by sliding 
toward and beyond the exposed end portion of the guide wire 4 while the 
front end portion of the guide wire remains in the vein 2. 
The apparatus further comprises a relatively rigid but flexible sleeve-like 
introducer 6 which is preferably made of a suitable synthetic plastic 
material, and an elongated rigid hollow cylindrical dilator 5 which can be 
inserted into the introducer 6 so that its front end portion extends 
beyond the first or front end portion 6a of the introducer 6 and that its 
rear end portion extends beyond the second or rear end portion 6b of the 
introducer 6. This can be seen in FIG. 5 which shows the front end portion 
6a of the introducer 6 temporarily implanted in the body of the patient, 
i.e., the first end portion 6a extends into the vein 2. The wire 4 serves 
as a reliable guide for convenient introduction of the first end portion 
6a into the vein 2, and the dilator 5 stiffens the introducer 6 during 
such insertion so as to reduce the likelihood of extensive bending or 
buckling. The dilator 5 is inserted into the introducer 6 before it is 
slipped onto the guide wire 4 and before it is moved to the position of 
FIG. 5 in which the first end portion 6a of the introducer is already 
implanted in the body of the patient. In the next step (see FIG. 6), the 
guide wire 4 and the dilator 5 are extracted from the introducer 6 and the 
latter is pushed deeper into the vein 2 so that its first end portion 6a 
as well as the majority of its intermediate portions between the end 
portions 6a, 6b extend into and in the longitudinal direction of the 
channel which the vein 2 defines for the flow of body fluid therein. The 
direction in which the guide wire 4 and the dilator 5 are extracted from 
the introducer 6 is indicated by the arrow Pf3 which is shown in FIG. 6. 
The introducer 6 is at least slightly flexible and can flex as soon as the 
dilator 5 is extracted from its channel or passage 14 (compare FIGS. 6 and 
7 with FIG. 5). The introducer 6 is then ready to allow for introduction 
of the electrode 1 in a manner as shown in FIGS. 7 and 8, i.e., a first 
section 1a of the implanted electrode extends into the vein 2 beyond the 
first end portion 6a of the introducer 6 and a second section 1b of the 
electrode 1 extends beyond the exposed and accessible second end portion 
6b of the introducer. The direction of insertion of the pacemaker 
electrode 1 is indicated by the arrow Pf4 which is shown in FIG. 7. The 
introducer 6 has fulfilled its primary purpose as soon as the tip 1c of 
the fully inserted electrode 1 reaches its destination, e.g., the heart of 
the patient. 
The introducer 6 must be withdrawn from the vein 2 and must be separated 
from the electrode 1 as soon as the latter is properly anchored in the 
body of the patient, i.e., as soon as the tip 1c reaches its destination. 
Extraction of the introducer 6 from the vein 2 would be simple but for the 
fact that the rear end of the section 1b of the electrode 1 carries a 
customary plug (reference may be had, for example, to FIG. 7 of the 
aforementioned U.S. Pat. No. 4,345,606) whose diameter exceeds the 
diameter of the passage 14 in the introducer 6 so that the latter cannot 
be slipped over the plug. Consequently, it is necessary to sever the 
introducer 6 in order to allow for its separation from the section 1b of 
the electrode 1. The plug at the rear end of the section 1b is necessary 
to connect the electrode with the pacemaker, such as the one disclosed in 
the aforementioned U.S. Pat. No. 4,345,606. Another solution would be that 
of severing the plug from the electrode section 1b or of attaching the 
plug to the section 1b subsequent to removal of the introducer 6. Neither 
of these solutions has been found to be practical and, therefore, the 
apparatus comprises a novel and improved severing device 7 which is shown 
in FIGS. 10, 11 and 13 and serves to slit the introducer 6 open from the 
end portion 6b to the end portion 6a in the course of and following the 
extraction of the end portion 6a from the body of the patient. As can be 
best seen in FIG. 12, the introducer 6 is a sleeve which is 
circumferentially complete from the end portion 6a to the end portion 6b, 
i.e., the sleeve is not formed with a slit or with one or more 
longitudinally extending weakened portions prior to insertion of the end 
portion 6a into the vein. However, the material (preferably a synthetic 
plastic substance) of the introducer 6 can be severed by the cutting edge 
10 of a knife 9 which forms part of the severing device 7 and is integral 
with or securely attached to an elongated trough-shaped supporting portion 
or holder 8 of the device 7. 
As can be seen in FIG. 11, the supporting portion 8 of the severing-device 
7 has a substantially U-shaped cross-sectional outline (it is also 
possible to use a supporting portion which has a substantially C-shaped 
cross-sectional outline). In other words the supporting portion 8 
resembles an elongated trough which preferably extends longitudinally 
beyond both sides of the knife 9, as considered in the longitudinal 
direction of the exposed second section 1b of the implanted electrode 1. 
This facilitates proper gripping of the supporting portion 8 by the 
fingers (e.g., by the thumb 17a and index finger 17b) of the person who is 
in charge of extracting the introducer 6 from the body of the patient and 
of simultaneously severing the introducer so that it can be separated from 
the electrode section 1b in the space between the locus where the 
electrode 1 extends into the vein and the locus of the aforediscussed 
plug. The knife 9 extends substantially radially from the supporting 
portion 8 and its cutting edge 10 faces the exposed end face 11 of the 
second end portion 6b of the introducer 6 when the latter assumes the 
position of FIG. 10 (in which the end portion 6a still extends into the 
vein, not shown) and the supporting portion 8 surrounds and frictionally 
engages the section 1b of the implanted electrode 1. A supporting portion 
8 having a substantially U-shaped cross-sectional outline prior to 
deformation of its preferably elastic material (e.g., a synthetic plastic 
substance) can be converted into a supporting portion with a substantially 
C-shaped cross-sectional outline when the supporting portion is properly 
grasped by the fingers 17a and 17b in a manner as shown in FIG. 13. The 
length of the supporting portion 8 is preferably selected with a view to 
allow for convenient and reliable grasping by one hand of the person who 
is in charge of extracting the introducer 6 from the vein 2 and of 
severing the introducer so that it can be separated from the section 1b of 
the pacemaker electrode 1. 
The end portion 6b of the introducer 6 carries two wing-like handgrip 
portions 12 which normally extend radially of the introducer and are 
located diametrically opposite each other. In the illustrated embodiment, 
the handgrip portions 12 are integral parts of the introducer 6 and each 
thereof has a flat or substantially flat edge face 16 as well as a second 
edge face which is provided with a recess 15 in the form of a relatively 
shallow flute. At least one of the handgrip portions 12 can be moved close 
to the other handgrip portion so that the flat edge faces 16 are close to 
or actually contact each other (see FIG. 10) whereby the two handgrip 
portions form a relatively large handle which can be grasped by two 
fingers of one hand (see FIG. 13) while the fingers 17a, 17b of the other 
hand grasp the supporting portion 8 of the severing device 7. FIG. 9 shows 
that each of the two handgrip portions 12 is movable about the axis of the 
introducer 6 toward the other handgrip portion (note the arrows Pf5) until 
the two handgrip portions reach the positions which are shown in FIG. 10, 
i.e., until such handgrip portions form the aforediscussed handle. Such 
movement of the handgrip portions 12 from the positions of FIG. 8, through 
the positions of FIG. 9 and to the positions of FIG. 10 results in at 
least some stretching or tensioning of the material of the introducer 6 at 
the location 18 (i.e., diametrically opposite the handle including the two 
abutting handgrip portions) which facilitates initial severing of the 
introducer 6 by the cutting edge 10 of the knife 9 when the handle 
including the handgrip portions 12 is pulled in the direction which is 
indicated in FIG. 13 by the arrow Pf6, namely in a direction having a 
component in the axial direction of the section 1b of the electrode 1 and 
a component at right angles to the axis of the section 1b. Once the 
cutting edge 10 has severed the end portion 6b (i.e., once the cutting 
edge 10 has penetrated into the end face 11 at the location 18), the 
severing of successive intermediate portions and ultimately of the end 
portion 6a of the introducer 6 can be completed in response to the 
exertion of a relatively small force. In other words, the person in charge 
of removing the introducer 6 simply continues to grasp the handle 
including the abutting handgrip portions 12 and continues to move such 
handle along the arcuate path which is denoted by the arrow Pf6. 
FIGS. 10, 11 and 13 show that the supporting portion 8 of the severing 
device 7 has a substantially conical terminal or tip 13 which can be 
received in and then at least partially seals the exposed end of the 
passage 14 in the introducer 6 to thus prevent any or to prevent 
pronounced outflow of blood via introducer 6 while the latter is being 
extracted from the vein and while it is in the process of being slotted 
longitudinally by the cutting edge 10 of the knife 9. The terminal 13 need 
not be exactly or pronouncedly conical, as long as it can sealingly engage 
the end face 11 or as long as it can enter into and sealingly engage the 
internal surface of the end portion 6b of the introducer 6. The terminal 
13 is preferably close or immediately adjacent to the cutting edge 10 of 
the knife 9 so that severing of the introducer 6 can begin practically 
immediately in response to entry of the terminal 13 into the end portion 
6b. The supporting portion 8 of the severing device 7 can be caused to 
surround the section 1b of the electrode 1 in close or immediate proximity 
of the end portion 6b prior to start of extraction of the end portion 6a 
from the vein so that severing of the introducer 6 begins substantially 
simultaneously with the start of extraction of the end portion 6a. This is 
desirable and advantageous because it contributes to a shortening of the 
interval which is required to extract the end portion 6a from the body of 
the patient and to separate the introducer 6 from the section 1b of the 
pacemaker electrode 1. The terminal 13 further ensures that the end 
portion 6b of the introducer 6 is reliably guided toward and against the 
cutting edge 10 during the initial stage of extraction of the end portion 
6a from the body, i.e., after the terminal 13 has penetrated into the 
oncoming end of the passage 14 in the introducer 6. This even more 
reliably ensures that the cutting edge 10 can sever the end portion 6b at 
the desired location (18). 
The purpose of flutes 15 in the respective edge faces of the handgrip 
portions 12 at the end face 11 of the end portion 6b of the introducer 6 
is to allow for more predictable engagement by two fingers which are used 
to move the handgrip portions 12 along the arcuate paths indicated by the 
arrows Pf5 before the thus formed handle is gripped in a manner as shown 
in FIG. 13 and pulled in the direction which is indicated by the arrow Pf6 
of FIG. 13. 
The material of the supporting portion 8 of the severing device 7 is 
preferably an elastomeric substance so that the supporting portion can be 
deformed whereby its internal surface can engage the external surface of 
the section 1b of the electrode 1 in order to reduce the likelihood of 
slippage of the supporting portion relative to the electrode while the 
cutting edge 10 of the knife 9 severs the introducer 6. That part of the 
supporting portion 8 which extends rearwardly and beyond the knife 9 
(i.e., in a direction away from the end portion 6b as viewed in FIG. 13) 
is preferably formed with one or more recesses in the form of shallow 
flutes 17 to allow for more convenient and more reliable engagement by the 
fingers (such as the thumb 17a) of the person in charge of extracting and 
separating the introducer 6. The fingers 17a and 17b can be used to shift 
the entire severing device 7 toward the end face 11 of the end portion 6b 
before the person in charge begins to extract the end portion 6a from the 
body of the patient. The flute 17 can be replaced with serrations at the 
exterior of the supporting portion 8, or such serrations can be provided 
in addition to one or more flutes 17. 
An important advantage of the severing device 7 is that it can be used to 
sever or slit open a reasonably stiff but severable introducer so that the 
latter can properly guide the electrode 1 during implantation in a manner 
as shown in FIGS. 7, 8 and 9 without excessive bending, buckling and/or 
other deformation which could prevent rapid and predictable implantation 
of the electrode. 
An important advantage of the improved severing device is that the 
apparatus can utilize a relatively simple, relatively rugged and 
relatively rigid introducer which need not be slotted prior to use and 
which need not be provided with longitudinally extending perforations, 
external grooves or otherwise weakened portions which are used in 
conventional introducers to allow for predictable slitting during or 
subsequent to extraction from the body of the patient. This is 
accomplished by the expedient of providing the improved severing device 
which can be readily applied around the exposed section of a properly 
implanted electrode or an analogous slender elongated object. The cutting 
edge of the knife cannot damage the insulating layer which is provided at 
the exterior of the electrode because the knife never contacts any part of 
the electrode, either during or subsequent to implantation. The insulation 
on the electrode is much more likely to be damaged or destroyed if the 
introducer is to be severed by shears or by a similar implement in order 
to allow for its separation from the implanted electrode without removing 
the aforediscussed plug. 
The introducer can be made of a single piece of suitable severable 
material, i.e., it is not necessary to employ two slotted tubes which are 
telescoped into each other in a manner such that they can be separated 
from the exposed section of an implanted electrode which already carries a 
plug for connection to the pacemaker. Composite introducers are bulky and 
expensive. On the other hand, an introducer which is slotted prior to 
introduction into the body of a patient is unduly weakened and is likely 
to buckle during implantation of an electrode. The same applies for 
introducers which are weakened by external grooves or by one or more rows 
of perforations. Moreover, a slotted or perforated introducer is likely to 
permit the escape of substantial quantities of body fluid during 
implantation of an electrode and during subsequent detachment of the 
introducer from the implanted object. The introducer which is used in the 
apparatus can be designed with a view to ensure that its characteristics 
(such as rigidity, suppleness, flexibility, sealing action at the point of 
penetration into the body, inner and outer diameters and/or others) are 
selected exclusively with a view to ensure predictable and rapid 
implantation of the electrode and not primarily or largely with a view to 
allow for separation from the implanted electrode without the need to 
remove the plug. 
The improved severing device exhibits the important advantage that it can 
be rapidly applied to and engaged with as well as rapidly separated from 
the exposed section of the implanted electrode and is highly unlikely to 
damage or otherwise adversely affect the insulation on or any other part 
of the electrode. The length of the supporting portion and the 
configuration of its flute or flutes can be readily selected in such a way 
that the supporting portion reliably maintains the knife in an optimum 
position for severing of the introducer and that it can be conveniently 
and predictably grasped by the fingers of one hand to hold it against 
slippage in the longitudinal direction of the exposed section of the 
implanted electrode. The material of the supporting portion can be elastic 
but nevertheless sufficiently rigid to hold the knife in an optimum 
orientation to ensure predictable severing of the portion 6b, of the 
intermediate portions and finally of the end portion 6a of the introducer 
in response to exertion of a pull in the direction of arrow Pf6 as 
described in connection with FIG. 13. At such time, the handgrip portions 
perform several important functions, namely of forming a satisfactory 
handle and also of enabling one hand of the person in charge to exert a 
pull in the direction of arrow Pf6 and to thus ensure that the severing 
action of the cutting edge begins at the location 18, i.e., diametrically 
opposite the handle. 
The provision of a severing device whose supporting portion is made of or 
contains elastomeric material which comes into contact with the exposed 
section of the implanted electrode is desirable and advantageous because 
such elastomeric material is highly unlikely to damage or destroy the 
insulation on the electrode, and such material also ensures that the 
supporting portion can frictionally engage the exposed section of the 
electrode so as to ensure that the severing device can be held at an 
optimum distance from the point of penetration of the electrode into the 
body of the patient without any slippage along the section 1b. Moreover, 
the forces which the fingers 17a and 17b apply to the exposed section 1b 
of the implanted electrode 1 are distributed (at least substantially 
uniformly) all the way between the two longitudinal ends of the elastic 
supporting portion 8 so that the latter is even less likely to damage the 
insulation of the electrode. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic and specific aspects of my contribution to 
the art and, therefore, such adaptations should and are intended to be 
comprehended within the meaning and range of equivalence of the appended 
claims.