Implantable endocardial lead with self-healing retractable fixation apparatus

DETAILED DESCRIPTION OF OUR PREFERRED EMBODIMENT Reference is now made to the drawings, wherein like numerals designate like parts throughout.
FIG.
1 shows an endocardial lead, generally designated 10.
The lead 10 has a suture sleeve 12 which slides along the lead 10 and which can be attached at an entrance into a vein of a patient in a conventional manner.
The lead 10 also has an electrode 14 located at a distal end 16 of the lead.
As shown in FIG.
2, the lead 10 comprises a polyurethane sheath or catheter 18 which defines a lumen 20 along a longitudinal axis of the lead 10.
Within the lumen 20, there is a coil conductor 22 for transmitting electrical impulses between the electrode 14 and a proximal end 24 of the lead 10.
In the illustrated embodiment, a trifilar conductor is shown as the coil conductor 22.
The coil conductor 22 wraps around a crimp plug 26 at the distal end 16 of the lead 10.
The electrode 14 comprises a contact 28 and a conductive sleeve 30.
The conductive sleeve 30 fits over-the crimp plug 26 and the coil conductor 22.
A first single strand short coil segment 32 is interposed between the coils of the trifilar conductor 22 and adjacent crimp plug 26.
As can best be seen in FIG.
4, the short coil segment 32 has a smaller normal interior diameter than does the trifilar conductor 22.
This causes the short coil segment 32 to effectively form a thread within the trifilar conductor 22.
The short coil segment 32 extends along the crimp plug 26 and for preferably between five and ten turns proximally from the crimp plug 26.
The four elements just mentioned are secured together by a crimp 34 in the conductive sleeve 30.
A silicone rubber sheath 36 houses the electrode 14.
The silicone rubber sheath 36 comprises a distal edge 38 which is open to allow the electrode to be exposed.
Near the distal edge 38 is a radiopaque ring 40 which is useful to a physician in placing the lead 10 within the heart of the patient.
Proximal from the radiopaque ring 40 is an hexagonal chamber 42.
The hexagonal chamber 42 houses a male hexagonal piston 44