Pacemaker lead with auxiliary stimulation pole

A pacemaker lead of the type comprising a flexible cord formed of at least one spiralled electric conductor and surrounded by an insulating material sheath and connected, at one end of the lead, to a connection head removable from the pacemaker and, at the other end, to a stimulation electrode device, said lead being characterized in that at a defined position of the flexible cord said sheath has an interruption of continuity making said spiralled conductor accessible from the outside, said interruption of continuity being able to be sealingly insulated from the outside by a mobile means.

BACKGROUND OF THE INVENTION 
The present invention relates to pacemaker stimulation leads. 
At the present time, in a stimulation lead, only the head of the lead may 
receive electric stimulation. The head of the lead being inserted into the 
pacemaker, it is only accessible when the lead is disconnected and removed 
from the pacemaker. 
During replacement of a pacemaker, the stimulation lead is practically 
always kept. The operation consists in loosening a screw providing 
pacemaker lead contact, removing the lead from the pacemaker, inserting it 
into the new pacemaker and tightening the screw on the head of the lead 
and finally reimplanting the lead and pacemaker under the skin. 
This operation may take several tens of seconds. 
Now, as soon as the screw is loosened, the patient is no longer stimulated. 
That is not serious if the patient keeps his own spontaneous cardiac 
rhythm, but some patients, called "dependent" have no spontaneous cardiac 
rhythm. The patient is then in cardiac arrest from the moment when the 
screw of the old pacemaker is loosened until the moment when the screw of 
the new pacemaker again provides contact with the stimulation lead. 
In a dependent patient, this operation is difficult, even dangerous. 
The object of the invention is to overcome this serious drawback by 
providing a lead designed so as to ensure continuity of the stimulation of 
the patient, particularly during replacement of his pacemaker. 
SUMMARY OF THE INVENTION 
For this, the invention provides a pacemaker lead of the type comprising a 
flexible cord formed of at least one spiralled electric conductor and 
surrounded by an insulating material sheath and connected, at one end of 
the lead, to a connection head removable from the pacemaker and, at the 
other end, to a stimulation electrode device, said lead being 
characterized in that at a defined position of the flexible cord said 
sheath has an interruption of continuity making said spiralled conductor 
accessible from the outside, said interruption of continuity being able to 
be sealingly insulated from the outside by a mobile means. 
In the present description by flexible cord is meant the connection between 
the stimulation electrode device and the pacemaker, whether this 
connection is formed of a single flexible cord or a flexible cord 
connected by any interconnection means to a so-called adapter connection 
having an appropriate head, the device of the invention being situated on 
the single flexible cord or on said connection. 
In a preferred embodiment, said interruption of continuity is formed by a 
local absence, at least partial, of the sheath for baring the spiralled 
conductor, this acess to the conductor being masked by a sleeve mounted 
for sliding on the flexible cord. 
With such a device, at the time of changing the pacemaker, said sleeve, 
which masks the orifice giving access to the internal conductor of the 
lead during use thereof, is slid so as to free said access for inserting a 
connection plug therein, such as a clip, in contact with said conductor. 
After connection of an auxiliary stimulation through this connection, the 
lead may be disconnected from the pacemaker without any risk. 
Once the new pacemaker is positioned, the auxiliary connection clip is 
disconnected and the insulating and sealed sleeve is repositioned over 
said access. Thus, the cardiac stimulation of the patient is permanently 
ensured during the whole operation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIG. 1, a pacemaker has been shown schematically and partially at 1 in 
which is engaged the head 2 of an unipolar lead formed, in a way known per 
se, of an electric conductor 3 wound in a spiral with substantially 
jointing turns and surrounded by a sheath 4 made from a flexible 
electrically insulating and biocompatible material such as polyurethane. 
Conductor 3 is extended, at the level of head 2, by a female tubular socket 
5 intended to come into electric contact with the internal circuits of 
pacemaker 1 via a screw 6 for fixing the head. 
The other end of conductor 3 is connected to the unipolar or bipolar 
electrode stimulation device (not shown). 
According to the invention, at a given position of sheath 4, preferably 
close to head 2, an interruption of continuity is provided making the 
internal conductor 3 accessible. 
In the embodiment illustrated in FIG. 1, this interruption of continuity 
consists in a local absence 7 of sheath, preferably over the whole 
periphery of the flexible cord, which thus has a narrow annular zone for 
temporarily connecting to conductor 3, for example, a crocodile type clip 
(not shown), itself connected to an external auxiliary stimulator for 
momentarily taking over from the pacemaker when this latter is 
disconnected for pacemaker replacement. 
In normal use of the lead, with pacemaker 1 connected, the uncovered zone 7 
of the sheath is masked and covered by means of a sleeve 8 in the form of 
an olive mounted for sliding on the flexible cord. In FIG. 1 the "normal" 
position of the sleeve, astride said zone 7, has been shown with broken 
lines at 8'. 
The role of sleeve 8, made for example from the same material as sheath 4, 
is to insulate the bared portion of conductor 3 electrically and sealingly 
from the medium surrounding the lead. In the absence of such a sleeve, 
because pacemaker 1 and the proximal portion of the flexible cord are 
disposed under the skin of the patient and are likely to be in contact 
with a conducting medium, short circuits might occur between the spiralled 
conductor 3 and the pacemaker, which should be avoided at all costs. 
Sleeve 8 must be relatively easy to slide along the flexible cord 
therefore, in order to have sealing as perfect as possible, on sheath 4, 
on each side of zone 7, annular projections 9 are advantageously provided 
slightly compressed by sleeve 8 when it is in its normal position (8') for 
insulating the auxiliary stimulation pole formed in zone 7. To have a 
better electric contact and avoid damaging the spiralled conductor 3, the 
bared portion of the latter is preferably, as illustrated in FIG. 2, 
surrounded by a metal conducting ring 10 welded to the conductor. It is in 
fact important to keep the spiralled form of conductor 3 for the internal 
passage of the conductor serves for introducing a guide for inserting the 
lead into the heart or repositioning the lead. 
FIG. 3 shows another way of providing an interruption of continuity in 
sheath 4 surrounding the conductor 3 giving access to the latter. In this 
other embodiment, a branch is formed, for example in the form of a Y, with 
a spiralled conductor section 11 one of whose ends is welded to conductor 
3 and the other end of which is welded to a connecting plug 12, male or 
female, which is accessible for a connecting plug, crocodile clip or the 
like, connected to an external auxiliary sitmulator. 
Said section 11 and at least a portion of the auxiliary connection plug 12 
are surrounded by an insulating sheath 4'. 
The accessible part of plug 12 is capped by a cap 13 insulating it 
completely electrically and sealingly. The cap is for example made from 
the same material as sheaths 4,4'. 
Cap 13, force fitted, is removed for changing the pacemaker for connecting 
the external auxiliary stimulator just before disconnection of head 2. 
Cap 13 is repositioned after reconnection of head 2 in the pacemaker. 
The device of the invention makes it possible, in all safety and 
particularly for dependent patients, to disconnect the head 2 from its 
pacemaker 1 for pacemaker replacement in particular but also for 
repositioning the lead in the heart by means of the guide whose 
progression inside the spiralled conductor 3 is in no wise hindered by the 
provision of the auxiliary stimulation pole of the invention. 
The invention also applies to bipolar leads. In this case, the solution 
illustrated in FIG. 3 is used preferably, which means providing two 
branches side by side each assigned to one of the two spiralled conductors 
of the bipolar lead. 
In the case where the device of the invention is provided on a connector or 
adapter connection, in patients fitted with a single flexible cord, in 
particular, it is possible to insert such a connection between their 
flexible cord and the pacemaker, the male connection head of the 
connection being identical or not to the head of said lead for connecting 
this latter to the same type of pacemaker or to a pacemaker with a 
different type of connection. Thus, it is not necessary to replace the 
existing lead which may thus, through the connection equiped with the 
invention, remain under stimulation at each subsequent change of 
pacemaker. 
Finally, the invention is obviously not limited to the embodiments shown 
and described above but covers on the contrary all variants thereof, 
particularly in so far as the means are concerned giving access to the 
spiralled conductor 3 and the mobile means combined with said access means 
for providing access at will to said conductor or on the contrary total 
electric and sealed insulation thereof with respect to the environment in 
which the lead is plunged.