Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical energy applicator
Reexamination Certificate
1999-09-03
2001-09-11
Jastrzab, Jeffrey R. (Department: 3737)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical energy applicator
C600S374000
Reexamination Certificate
active
06289250
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an implantable electrode lead and, more particularly, to an implantable electrode lead to be implanted in body tissue, which improves the repetition durability of the lead body of the electrode lead in the body tissue when used generally together with a cardiac pacemaker or implantable defibrillator and which can reduce the mechanical stress applied by the lead body onto the body tissue because of its softness.
2. Description of the Related Art
Many types of implantable electrode leads used together with a cardiac pacemaker or implantable defibrillator are conventionally known. Generally, an electrode lead is constituted by at least one electrode, an electrical connector, and a lead body, and is used as an implantable electrode lead. The electrode electrically stimulates the heart or senses electrical cardiac activity in one or both of the chambers of the heart. The electrode lead is electrically connected to the cardiac pacemaker or implantable defibrillator through the electrical connector. The lead body is arranged between the electrode and electrical connector, and is formed of an electrical conductor and a bio-compatible electrically insulating cover. The electrical conductor transmits an electrical signal between the electrode and the cardiac pacemaker or implantable defibrillator.
In a transvenously used implantable electrode lead, the electrode and part of the lead body are inserted in the heart and vein. The lead body outside the vein and the electrical connector are extended to a connection housing for the cardiac pacemaker or defibrillator and connected to it.
Currently, in the lead body of a bipolar implantable electrode lead, a coaxial structure constituted by two types of conductive coils having different pitch diameters (mean diameters), an insulating sheath located between the two conductive coils, and a sheath located on the outermost surface of the lead body is the main stream.
According to another lead structure, a sheath is formed on the outer surface of an insulating parallel-wound coil on which a conductive wire with insulating coating is wound with the same pitch diameter (mean diameter).
Generally, in a conductive coil used in an implantable electrode lead, since the conductive wire is helically wound, when the lead body deforms, the internal stress of the conductive wire is reduced. It is known that the larger the spring index (D/d), the larger this internal stress reducing effect where D is the pitch diameter (mean diameter) of the conductive coil, d is the diameter of the conductive wire, and d and D are constant.
SUMMARY OF THE INVENTION
An implantable electrode lead inserted by puncture reaches the heart chamber through the subclavian vein. Since it is repeatedly pressed by the clavicle and the first rib, the electrode lead sometimes fractures to pose a clinical problem. Attempts have been made to solve this problem in terms of implantation by performing puncture at an appropriate portion where the electrode lead will not be easily damaged. If, however, the electrode lead has a large outer diameter, not only the load on the electrode lead applied by the clavicle and first rib increases, but also the electrode lead is difficult to be inserted in the blood vessel. It is also pointed out that when a plurality of leads are to be inserted in the cardiac ventricle, tricuspid incompetence can be caused.
Improvement is accordingly made to decrease the outer diameter of the electrode lead. In the conventional coaxial structure, it is difficult to further decrease the outer diameter of the lead due to its structure. In particular, when silicone is used as the sheath material, since its mechanical characteristics, e.g., the tearing strength, are generally inferior to those of polyurethane, the sheath must have a large thickness, resulting in a large electrode lead diameter. When the number of stimulations to be transmitted to the lead body or the number of signals to be sensed is to be increased, the conductive coil must be extended in the radial direction of the lead body, thus increasing the outer diameter of the electrode lead.
In the bipolar electrode lead, when the lead body undergoes a pressure load, the insulating sheath located between the two conductive coils may be damaged to cause an insulation failure, which is a clinical problem.
With the structure in which the sheath is formed on the outer surface of the parallel-wound conductive wire on which the conductive wire with an electrically insulating coating layer is formed to have the same pitch diameter (mean diameter), the number of stimulations to be transmitted to the lead body or the number of signals to be sensed can be increased easily by increasing the number of coils without increasing the outer diameter of the lead, which is advantageous.
Even in the electrode lead having an increased number of coils, when a polyurethane material having comparatively high hardness (Shore hardness:
55
D) is used as the sheath material, the sheath is permanently deformed or buckled when it is subjected to repeated flexure or flexure with a very small radius of curvature. An excessive load acts on the conductive coil to likely disconnect it. Since the pitch of the conductive coil is increased in accordance with the thickness of the insulating coating layer, a decrease in flexure durability may degrade. Conventionally, these problems have been coped with by minimizing the number of conductive wires assigned to transmit one electrical signal or increasing the pitch diameter (mean diameter) of the conductive coils.
However, these countermeasures are not effective at all in terms of failsafe measure against disconnection and further decrease in the outer diameter of the electrode lead. Therefore, improvement has been sought for.
The present invention has been made in view of the problems described above, and has as its object to provide an implantable electrode lead in which durability against the pressure applied under the clavicle, repeated flexure caused in the body tissue, or flexure with a very small radius of curvature is improved, and the lead body of which has softness to reduce the mechanical stress applied by the lead body on the body tissue.
In order to solve the above problems and to achieve the above object, the present invention relates to a small-diameter lead having excellent flexure durability, and provides a combination of the preferable mechanical characteristics of the conductive coil and sheath. More specifically, according to the present invention, there is provided an implantable electrode lead having connecting means arranged at a proximal end of a lead body and mechanically and electrically connected to an implantable device, and at least one electrode arranged at a distal end of the lead body in order to transmit an electrical signal between the implantable device and the electrode which is implanted in a predetermined portion to perform one or both of transmission of electrical stimulation to body tissue and sensing of an electrical signal from the body tissue, characterized in that the lead body is constituted by a conductive coil obtained by helically winding a conductive wire formed with an insulating coating layer and having a diameter (d) to have a coil pitch diameter (mean diameter) (D), and a sheath made of a bio-compatible electrically insulating material to cover an outer surface of the conductive coil, and the lead body is set to have an outer diameter of not more than 2 mm, the electrically insulating material of the sheath is formed of a soft material having a Shore hardness of less than
80
A, and the conductive coil is set to have a spring index (D/d) of larger than 7.8.
The implantable electrode lead is characterized in that the conductive coil is formed by a multi-filar structure obtained by winding a plurality of conductive wires to have the same coil pitch diameter (D). The implantable electrode lead is characterized in that the electrode comprises a plurality of electrodes so that
Katayama Kunimasa
Shirakawa Katsuhiro
Tsuboi Fuminori
Burns Doane , Swecker, Mathis LLP
Jastrzab Jeffrey R.
Kabushiki Kaisha Cardio-Pacing Research Laboratory
LandOfFree
Implantable electrode lead does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Implantable electrode lead, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Implantable electrode lead will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2494166