Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical energy applicator
Reexamination Certificate
1999-04-27
2001-06-26
Kamm, William E. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical energy applicator
Reexamination Certificate
active
06253110
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to implantable stimulation leads generally and more particularly to implantable stimulation leads having electrodes optimized reduce post pulse polarization.
Following delivery of a cardiac pacing pulse by an electrode, an after potential typically remains on the electrode which persists for a sufficient period of time thereafter to interfere with sensing of cardiac signals associated with tissue depolarization caused by the delivered pulse. This phenomenon has been addressed in a number of ways over the years, and quite a large variety of electrode coatings have been developed in an effort to reduce post pulse polarization effects. One of the most common approaches to reducing post pulse polarization is to provide a high surface area coating having micron or sub-micron size surface features, such as a porous sintered metallic coating as described in U.S. Pat. No. 4,280,514 issued to MacGregor, a metal oxide or nitride coating as described in U.S. Pat. No. 4,679,572 issued to Baker, U.S. Pat. No. 5,571,158 issued to Bolz et al. and U.S. Pat. No. 5,683,443 issued to Munshi et al., or a coating of platinum black, as described in U.S. Pat. No. 4,502,492 issued to Bornzin, U.S. Pat. No. 4,506,680 issued to Stokes and U.S. Pat. No. 5,282,844 also issued to Stokes, all of which patents are incorporated herein by reference in their entireties. As noted in the these patents, the provision of a high surface area coating does substantially lower post pulse polarization levels. However, as a practical matter, further reduction in post pulse polarization levels are still desirable.
SUMMARY OF THE INVENTION
The present invention is directed to further reducing the post pulse polarization levels of pacing electrodes provided with platinum black or other high surface area coatings. The inventors have determined that this may be accomplished by plasma cleaning the electrodes toward the end of the lead manufacturing process, following application of the high surface area coating to the electrode. In particular, in the context of electrodes as in the above cited Stokes patents which are provided with a platinum black coating and which have a steroid coating applied after assembly of the lead, the plasma cleaning process may optimally be undertaken immediately prior to the steroid application step. Testing performed by the inventors on electrodes having platinum black coatings has indicated that the plasma cleaning step produces substantial reductions in post pulse polarization levels. While the specific mechanism by which plasma cleaning produces an electrode having improved polarization characteristics has not been precisely demonstrated, it is believed by the inventors that the plasma cleaning process removes hydrophobic contaminants from the surface which improves the “wetability” of the coating, which in turn assists in dispersion of ionic species adjacent the electrode surface and the discharge of the accumulated polarization following delivery of the pacing pulse.
It is believed by the inventors that plasma cleaning the previously coated electrodes is beneficial in the context of any pacing electrode, including endocardial, myocardial and epicardial electrodes, and including both pacing cathodes and pacing anodes. The improved polarization characteristics of the electrodes so produced is believed particularly valuable in improving the operation of the “auto-capture” features now present in some implantable pacemakers, which attempt to sense the heart depolarization waveform following delivery of the pacing pulse, which depolarization waveform in many cases overlaps the voltage waveform associated with decay of the post pulse polarization.
While the plasma cleaning process as described in detail herein is specifically applied to leads having platinum black, titanium nitride and ruthenium oxide coatings, it is also believed by the inventors that the plasma cleaning process is beneficial in the context of other porous or high surface area coatings having micron or sub-micron surface features, for example, sputtered, sintered or otherwise produced porous metal, metal oxide or metal nitride coatings, including platinum, iridium, titanium, iridium oxide, tantalum oxide, iridium nitride and the like, as disclosed in the MacGregor, Baker, Bolz et al. and Munshi et al. patents incorporated by reference above. It is believed that the improved wetability imparted by plasma cleaning following application of these types of high surface area coatings will also provide for improvements in post pulse polarization characteristics.
REFERENCES:
patent: 4280514 (1981-07-01), MacGregor
patent: 4502492 (1985-03-01), Bornzin
patent: 4506680 (1985-03-01), Stokes
patent: 4679572 (1987-07-01), Baker, Jr.
patent: 4735205 (1988-04-01), Chachques et al.
patent: 4934049 (1990-06-01), Kiekhafer et al.
patent: 4972848 (1990-11-01), DiDomenico et al.
patent: 5016645 (1991-05-01), Williams et al.
patent: 5071351 (1991-12-01), Green, Jr. et al.
patent: 5265608 (1993-11-01), Lee et al.
patent: 5282844 (1994-02-01), Stokes et al.
patent: 5397343 (1995-03-01), Smits
patent: 5545207 (1996-08-01), Smits et al.
patent: 5571158 (1996-11-01), Bolz et al.
patent: 5683443 (1997-11-01), Munshi et al.
Brabec Scott J.
Brennen Kenneth R.
Johnson Bruce C.
Rugland Roger E.
Schindeldecker William J.
Kamm William E.
Medtronic Inc
Wolde-Michael Girma
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