Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical energy applicator
Reexamination Certificate
1998-08-12
2001-05-29
Schaetzle, Kennedy (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical energy applicator
C607S116000, C600S374000
Reexamination Certificate
active
06240321
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to medical devices, such as leads and catheters. More particularly, it pertains to expandable seals for medical devices such as leads and catheters.
BACKGROUND OF THE INVENTION
Leads implanted in or about the heart have been used to reverse (i.e., defibrillate or cardiovert) certain life threatening arrhythmias, or to stimulate contraction (pacing) of the heart. Electrical energy is applied to the heart via the leads to return the heart to normal rhythm. Leads have also been used to sense in the atrium or ventricle of the heart and to deliver pacing pulses to the atrium or ventricle. The same lead used to sense the condition is sometimes also used in the process of delivering a corrective pulse or signal from the pulse generator of the pacemaker.
Cardiac pacing may be performed by the transvenous method or by leads implanted directly onto the ventricular epicardium. Most commonly, permanent transvenous pacing is performed using a lead positioned within one or more chambers of the heart. A lead, sometimes referred to as a catheter, may be positioned in the right ventricle or in the right atrium through a subclavian vein, and the lead terminal pins are attached to a pacemaker which is implanted subcutaneously. The lead may also be positioned in both chambers, depending on the lead, as when a lead passes through the atrium to the ventricle. Sense electrodes may be positioned within the atrium or the ventricle of the heart.
Pacemaker leads represent the electrical link between the pulse generator and the heart tissue which is to be excited. These pacemaker leads include single or multiconductor coils of insulated wire having an insulating sheath. The coils provide a cylindrical envelope, many times referred to as a lumen, which provides a space into which a stiffening stylet can be inserted. The conductive coil is connected to an electrode in an electrode assembly at a distal end of a pacing lead.
After the electrode assembly is positioned at a desired location within the heart, it is desirable to provide some method for securing the electrode assembly at that location. One approach is to use a passive device which has structure to allow for tissue growth surrounding the structure to affix the electrode assembly to the heart. Another approach is to use an active device where mechanical fixation devices are used to firmly anchor the electrodes in the heart. One type of mechanical fixation device used is a corkscrew, or a helix. During placement of the lead, the tip of the lead travels intravenously through veins and the heart. While traveling through the veins, the helix at the tip of the lead may snag or attach to the side wall of the vein. Since this is highly undesirable as it may cause damage or other complications to a patient, retractable helixes have been provided for leads.
The practitioner must maintain the electrode pressed against the wall of the cavity before shifting the screw. When the screw is shifted, the electrode may be correctly in contact with the wall, and the fixation screw, as it travels out of the body of the electrode, penetrates and becomes hooked in the tissue of the wall. Alternatively, the electrode may stop short of the wall of the cavity and it may be necessary for the practitioner to start again by retracting the screw and then turning the helix out again into the cardiac tissue. Thus, it is important for the helix to rotate freely within the electrode.
During use, the lead provides and receives critical information to and from the heart. The lead, therefore, must remain in sufficient operative condition without interference from entry of bodily fluids. To prevent entry of bodily fluids into the lead, a seal can be provided at the distal end of the lead. Conventional leads often use O-rings or puncture seals to seal the distal end of the lead from entry of bodily fluids. The O-ring seals can be difficult to manufacture due to dimensional constraints which also affects the extension/retraction mechanism of the lead, as well as the effectiveness of the seal. Puncture seals also may increase the difficultly of using the helix, since the helix needs to puncture the seal and the puncture seals can increase the friction between the extension mechanism and the seal. The friction makes it more difficult to extend or retract the extension mechanism and the helix. In addition, the structural integrity of the puncture seal can be jeopardized if the seal continues to tear from repeated movement and/or stress from the fixation screw.
Accordingly, there is a need for a lead which is sufficiently sealed from the environment. What is further needed is a seal which does not interfere with the extension and retraction of the helix.
SUMMARY OF THE INVENTION
A body-implantable lead assembly is provided comprising a lead, one end being adapted to be connected to an electrical supply for providing or receiving electrical pulses. The lead further comprises a distal tip which is adapted to be connected to tissue of a living body. The lead also has a sheath of material inert to body materials and fluids and at least one conductor extending through the lead body.
The distal tip electrode is adapted for implantation proximate to or within the heart while connected with a system for monitoring or stimulating cardiac activity. In another embodiment, the distal tip electrode assembly is adapted for implantation proximate to the heart while connected with a system for monitoring or stimulating cardiac activity. The distal tip electrode includes, in one embodiment, an electrode tip, a mesh screen disposed at a distal end of the electrode tip, a fixation helix disposed within the electrode tip, and a hydrogel seal. The helix is retractable, and is in contact with a movement mechanism. The movement mechanism provides for retracting the helix, such as during travel of the electrode tip through veins. In another embodiment, the electrode tip further includes a piston for moving the helix. The piston can further include a slot for receiving a stylet. When engaged and rotated, the piston provides movement to the helix. The piston is coated with the hydrogel seal, in one embodiment, which is adapted to expand upon contact with bodily fluid.
In another configuration, a distal tip electrode is provided which is adapted for implantation proximate to the heart, while optionally connected with a system for monitoring or stimulating cardiac activity. The distal tip electrode includes a seal comprised of an expandable matrix which is adapted to expand upon contact with fluid. The seal can be in the form of a plug which is inserted into the electrode, or a medical device, using an advancing tool. The plug can be molded of the expandable material into a variety of shapes, for instance a ring, or including a tapered surface. The ring shape can also be used for surrounding an internal lead structure disposed within the lead. The plug can optionally include features which frictionally engage an encompassing surface and prevent premature removal of the advancing tool. In another embodiment, the seal is in the form of an end cap which is affixed to the distal tip of the electrode. Alternatively, the expandable matrix is disposed on the interior of a housing which is secured to the electrode.
The provided medical device, which includes an electrode tip, supplies an extension/retraction mechanism which is sealed from exposure to fluids. The lead avoids deterioration of its function by entry of liquid inside the lead, owing to the provision of a highly effective seal which does not interfere with the helix. In addition, the seal remains functional when the lead is removed for short periods of time from an environment filled or partially filled with fluid. Yet another advantage is that the lead and the seal permit rotating the extension/retraction mechanism until it penetrates the cardiac tissue without limitation on the number of rotations until proper anchorage has been achieved, and without significant friction imparted to the extension/ret
Heil, Jr. Ronald W.
Hum Larry L.
Janke Aaron W.
Tockman Bruce
Westlund Randy
Cardiac Pacemakers Inc.
Schaetzle Kennedy
Schwegman Lundberg Woessner & Kluth P.A.
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