Electrode assembly having spines with controlled flexibility

1. A spine for use in an electrode assembly of an electrophysiologic catheter comprising: a flexible core that extends through a length of the spine; a polymeric cover coaxially disposed over the flexible core; a filler material coaxially disposed between the polymeric cover and the flexible core; and a plurality of electrodes distributed longitudinally along the spine over the polymeric cover; wherein each electrode has at least one associated lead that extends to a proximal end of the spine, the at least one lead disposed between the filler material and the polymeric cover; the flexible core, the polymeric cover and the filler material forming the spine, wherein the filler material comprises at least one layer of filler material; and wherein an amount of the at least one layer of filler material forming the spine is adjusted longitudinally along the spine based on changes in flexibility to the spine caused by varying numbers of electrode leads present at different relative longitudinal positions along the spine, the at least one layer of filler material having a variable number of layers of filler material depending on the different relative longitudinal positions along the spine and the number of electrode leads present at the different relative longitudinal positions.

2. The spine of claim 1 , wherein the adjusted amount of the at least one layer of filler material is configured to provide the spine with more uniform flexibility along the length.

3. The spine of claim 1 , wherein there are more layers of the at least one layer of filler material in a distal position as compared to a proximal position along the length of the spine.

4. The spine of claim 1 , wherein there are more layers of the at least one layer of filler material in a distal position as compared to a proximal position along the length of the spine.

5. The spine of claim 4 , wherein a distal position comprises two layers of the at least one layer of filler material, an intermediate position comprises one layer of the at least one layer of filler material and a proximal position comprises no layers of the at least one layer of filler material.

6. The spine of claim 1 , wherein each layer of the at least one layer of filler material comprises a shrink fit polymer.

7. The spine of claim 1 , wherein the adjusted amount of the at least one layer of filler material comprises a tapered structural component.

8. A catheter comprising an elongated catheter body having proximal and distal ends and at least one lumen therethrough and an electrode assembly at the distal end of the catheter body, the electrode assembly comprising at least one spine having a proximal end connected to the catheter body, wherein the spine has a flexible core that extends through a length of the spine, a polymeric cover coaxially disposed over the flexible core, a filler material coaxially disposed between the polymeric cover and the flexible core, and a plurality of electrodes distributed longitudinally along the spine over the polymeric cover, wherein each electrode has at least one associated lead that extends to a proximal end of the spine, the at least one lead disposed between the filler material and the polymeric cover; the flexible core, the polymeric cover and the filler material forming the spine, wherein the filler material comprises at least one layer of filler material, and wherein an amount of the at least one layer of filler material forming the spine is adjusted longitudinally along the spine based on changes in flexibility to the spine caused by varying numbers of electrode leads present at different relative longitudinal positions along the spine, the at least one layer of filler material having a variable number of layers of filler material depending on the different relative longitudinal positions along the spine and the number of electrode leads present at the different relative longitudinal positions.

9. The catheter of claim 8 , further comprising a plurality of spines connected at their proximal and distal ends configured as a basket-shaped electrode assembly, wherein the basket-shaped electrode assembly has an expanded arrangement wherein the spines bow radially outwardly and a collapsed arrangement wherein the spines are arranged generally along a longitudinal axis of the catheter body.

10. The catheter of claim 9 , wherein the plurality of spines comprise a framework formed from a laser cut tube of material.

11. A method for controlling spine flexibility comprising:

providing a spine having a flexible core that extends through a length of the spine, a polymeric cover coaxially disposed over the flexible core, a filler material coaxially disposed between the polymeric cover and the flexible core, and a plurality of electrodes distributed longitudinally along the spine over the polymeric cover, wherein each electrode has at least one associated lead that extends to a proximal end of the spine, the at least one lead disposed between the filler material and the polymeric cover; the flexible core, the polymeric cover and the filler material forming the spine, wherein the filler material comprises at least one layer of filler material; and

adjusting an amount of the at least one layer of filler material forming the spine longitudinally along the spine based on changes in flexibility to the spine caused by varying numbers of electrode leads present at different relative longitudinal positions along the spine, the at least one layer of filler material having a variable number of layers depending on a relative longitudinal position along the spine and the number of electrode leads present at that relative longitudinal position.

12. The method of claim 11 , wherein adjusting the amount of the at least one layer of filler material provides the spine with more uniform flexibility along the length.

13. The spine of claim 11 , wherein adjusting the amount of the at least one layer of filler material comprises providing more layers of the at least one layer of filler material in a distal position as compared to a proximal position along the length of the spine.

14. A method for treatment comprising:

providing a catheter having an elongated catheter body with proximal and distal ends and at least one lumen therethrough and an electrode assembly at the distal end of the catheter body, the electrode assembly comprising at least one spine having a proximal end connected to the catheter body, wherein the spine has a flexible core that extends through a length of the spine, a polymeric cover coaxially disposed over the flexible core, a filler material coaxially disposed between the polymeric cover and the flexible core, and a plurality of electrodes distributed longitudinally along the spine over the polymeric cover, wherein each electrode has at least one associated lead that extends to a proximal end of the spine, the at least one lead disposed between the filler material and the polymeric cover; the flexible core, the polymeric cover and the filler material forming the spine, wherein the filler material comprises at least one layer of filler material, and wherein an amount of the at least one layer of filler material forming the spine is adjusted longitudinally along the spine based on changes in flexibility to the spine caused by varying numbers of electrode leads present at different relative longitudinal positions along the spine, the at least one layer of filler material having a variable number of layers of filler material the different relative longitudinal positions along the spine and the number of electrode leads present at the different relative longitudinal positions;

advancing the distal end of the catheter body with the electrode assembly to a desired region within a patient with the at least one spine in a collapsed arrangement that is generally aligned along a longitudinal axis of the catheter body; and

causing the electrode assembly to assume an expanded arrangement in which the at least one spine assumes an expanded arrangement, wherein the expanded arrangement is based at least in part on a flexibility of the spine resulting from the adjusted amount of the at least one layer of filler material.

15. The method of claim 14 , further comprising receiving electrical signals from the plurality of electrodes in contact with tissue.