Pacemaker Lead and Method of Making Same
An improved pacemaker lead including a lead body supporting at least one flexible conductor element that provides an electrical signal path between a proximal connector element and a distal electrode. The lead body includes an insulating structure that protects the flexible conductor element(s) wherein the insulating structure is realized from a polymer material comprises an isobutylene block copolymer. The polymer material of the insulating structure has a maximum tensile strength in the range between 20 MPa and 40 MPa (most preferably in a range between 25 MPa and 35 MPa). In the preferred embodiment, the hardness of the polymer material of the insulating structure can be characterized by a Shore hardness in a range between 70A and 80A. In the preferred embodiment, the isobutylene block copolymer consists of a first polymer block component containing isobutylene-derived monomer units and a second polymer block component derived from a monomer component other than isobutylene (most preferably, styrene) with mole fraction of said second polymer block component as part of said isobutylene block copolymer in a range between 30% and 40%. The flexible conductor element(s) preferably include a coiled wire conductor defining a central axis with an outer surface facing radially outward away from the central axis and an inner surface facing radially inward toward the central axis, and the insulating structure surrounds at least the outer surface of the coiled wire conductor (and more preferably encapsulates the coiled wire conductor). The polymer material of the insulating structure has reduced oxygen permeability, and thus provides improved resistance to environmental stress cracking and metal ion induced oxidation while maintaining the flexibility and desired tensile strength of the lead body.
1 . A flexible pacemaker lead comprising:
a lead body supporting at least one flexible conductor element that provides an electrical signal path between a proximal connector element and a distal electrode, said lead body including an insulating structure that protects said at least one flexible conductor element, said insulating structure realized from a polymer material comprising an isobutylene block copolymer, and said polymer material having a maximum tensile strength in the range between 20 MPa and 40 MPa.
2 . A flexible pacemaker lead according to claim 1 , wherein:
said at least one flexible conductor element comprises a coiled wire conductor defining a central axis with an outer surface facing radially outward away from the central axis and an inner surface facing radially inward toward the central axis; and said insulating structure surrounds at least said outer surface of said coiled wire conductor.
3 . A flexible pacemaker lead according to claim 2 , wherein:
said insulating structure encapsulates said coiled wire conductor.
4 . A flexible pacemaker lead according to claim 3 , wherein:
said insulating structure comprises a coaxial insulting structure including an outer insulating part and an inner insulating part.
5 . A flexible pacemaker lead according to claim 4 , wherein:
said at least one flexible conductor element is formed over said inner insulating part, and said outer insulating part is formed over both said at least one flexible conductor and said inner insulating part.
6 . A flexible pacemaker lead according to claim 4 , wherein:
said inner insulating part defines a guide lumen for receiving a stylet or guide wire.
7 . A flexible pacemaker lead according to claim 1 , wherein:
the polymer material of said insulating structure consists essentially of an isobutylene block copolymer that contains, in at least part thereof, isobutylene-derived monomer units.
8 . A flexible pacemaker lead according to claim 7 , wherein:
said isobutylene block copolymer consists of a first polymer block component containing isobutylene-derived monomer units and a second polymer block component derived from a monomer component other than isobutylene.
9 . A flexible pacemaker lead according to claim 8 , wherein:
said second polymer block component comprises at least one cation-polymerizable monomer selected from the group including aliphatic olefins, alicyclic olefins, aromatic vinyl compounds, dienes, vinyl ethers, silanes, vinylcarbazole, β-pinene, acenaphthylene and like monomers.
10 . A flexible pacemaker lead according to claim 7 , wherein:
said isobutylene block copolymer has a block structure selected from the group including a diblock copolymer structure, a triblock copolymer structure, and a multiblock copolymer structure.
11 . A flexible pacemaker lead according to claim 10 , wherein:
said block structure has a straight chain, branched chain, star-shaped or other structure.
12 . A flexible pacemaker lead according to claim 11 , wherein:
said isobutylene block copolymer of said polymer blend comprises a styrene-isobutylene-styrene triblock copolymer.
13 . A flexible pacemaker lead according to claim 8 , wherein:
mole fraction of said second polymer block component as part of said isobutylene block copolymer is in a range between 30% and 40%.
14 . A flexible pacemaker lead according to claim 8 , wherein:
said second polymer block component comprises styrene.
15 . A flexible pacemaker lead according to claim 14 , wherein:
mole fraction of styrene content as part of said isobutylene block copolymer is in a range between 30% and 40%.
16 . A flexible pacemaker lead according to claim 1 , wherein:
said polymer material has a Shore hardness between 70A and 80A.