Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical energy applicator
Reexamination Certificate
1999-03-08
2001-11-20
Schaetzle, Kennedy (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical energy applicator
C600S374000
Reexamination Certificate
active
06321123
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to implantable electrical leads and more particularly for implantable leads intended for use in the coronary sinus of a patient's heart.
Recently there has been an increased interest in the placement of cardiac pacing and sensing electrodes in the coronary sinus, particularly for purposes of bi-atrial and bi-ventricular pacing. In this context, a number of configurations have been proposed in order to assist in placement and retention of the lead and its electrodes in desired locations within the coronary sinus. Early coronary sinus leads such as the Medtronic Model 6992 Lead had a generally straight lead body configuration and employed a non-conductive tip extending distally from the distal-most electrode as a mechanism for assisting in the insertion of the lead in the coronary sinus and for retaining it in the coronary sinus after insertion. More recently, it has been proposed to provide a body of a coronary sinus lead with a pre-formed sinusoidal or helical configuration in order to allow the lead to expand into contact with the walls of the coronary sinus and thereby retain the lead, much in the same fashion as has been employed in the context of spinal stimulation leads. Coronary sinus leads having such a pre-formed configuration are disclosed in U.S. Pat. No. 5,423,865 issued to Bowald et al. and U.S. Pat. No. 5,476,498 issued to Ayers. Spinal cord stimulation leads having similar pre-formed configurations are disclosed in U.S. Pat. No. 4,374,527 issued to Iversen and U.S. Pat. No. 4,414,986 issued to Dickhudt.
An alternative approach to fabrication of coronary sinus leads has been to provide the distal portion of the lead with a curved configuration corresponding to some extent to the curved configuration of the coronary sinus and great vein. For example, a coronary sinus lead having a continuous multi-radius curvature is disclosed in U.S. Pat. No. 5,433,729 issued to Adams et al. Similar configurations are illustrated in U.S. Pat. No. 5,423,772 issued to Lurie and in U.S. Pat. No. 5,445,148 issued to Jaraczewski. An alternative configuration employing two spaced 45° bends is disclosed in U.S. Pat. No. 5,683,445 issued to Swoyer.
SUMMARY OF THE INVENTION
In the context of coronary sinus leads, it is believed that further improvements in lead configuration can still be made in order to enhance both the sensing characteristics of the coronary sinus lead and to provide for stable location of electrodes in the coronary sinus. The lead of the present invention is intended to accomplish these goals by means of an improved lead body and electrode configuration. In a preferred embodiment, the lead is pre-formed to display a small radius, J-shaped bend in its distal end. In particular, the J-shaped bend is preferably configured such that the distal tip of the lead is spaced less than about 0.9 inches laterally from the portion of the lead proximal to the J-shaped bend. In such a lead, the tip of the lead is provided with a pacing and sensing electrode and the curved portion of the J-shaped distal portion of the lead carries an elongated coil electrode which serves as the indifferent electrode for pacing and sensing. This configuration is optimized to allow placement of the lead in portions of the coronary sinus having a wide variety of diameters.
For example, if the lead is placed in a portion of the coronary sinus having a relatively larger diameter, the lead can be placed such that the distal tip of the lead is curved back more proximally such that the J-shaped curve is compressed to display a reduced radius of curvature, bracing the lead within the coronary sinus and stabilizing the location of the tip electrode. In portions of a coronary sinus having a lesser diameter, the lead may be implanted with the distal tip of the lead directed distally relatively to the lead body such that the J-shaped bend is opened to display a greater radius of curvature, which also braces the lead within the coronary sinus and stabilizes the location of the tip electrode.. In either configuration, the pre-formed J-shaped bend serves to cause the lead to extend across the width of the coronary sinus and to brace the electrode located at the distal end of the lead against the wall of the coronary sinus.
Preferably, for purposes of left atrial pacing, the lead is located so that the tip electrode is located adjacent the wall of the coronary sinus closest to the left atrium. Given the configuration of the lead this necessarily results in the elongated coil indifferent electrode being located at least in part adjacent the opposite wall of the coronary sinus, closer to the left ventricle. The indifferent electrode in preferred embodiments extends over a length of at least about 10 millimeters, in order to provide a large surface area electrode which in turn provides some averaging of the ventricular signal due to the spatial dispersion of the electrode. In other embodiments, the coil electrode may be extended over a substantially greater distance, for example 20 to 50 millimeters in order to further enhance the spatial distribution of the indifferent electrode and provide for a greater averaging of the ventricular signal, in turn reducing the relatively high far field of the ventricular signal relative to the atrial signal and assisting in accurate discrimination between atrial and ventricular signals sensed by the lead. As an alternative, rather than employing a single longer coil electrode, spatial dispersion may be accomplished by provision of multiple spaced indifferent electrodes proximal to the tip electrode to accomplish averaging of the ventricular signal.
In analyzing the ventricular signal sensed in leads generally corresponding to those according to the present invention, the inventors have determined that the ventricular signals sensed at the ends of the indifferent electrodes generally display the highest slew rate, and that this slew rate can be reduced if the end of the indifferent electrode is curved such that it extends generally perpendicular to the axis of the coronary sinus, directed generally away from the ventricle. In order to accomplish this result, in some embodiments, the lead may be configured to employ a longer electrode, for example, 20 millimeters or more in length, and the lead body may be preformed so that as implanted, both ends of the indifferent electrode are curved away from the coronary sinus wall closer to the ventricle and toward the coronary sinus wall adjacent the atrium when the lead is implanted. This may be accomplished by providing a second, preformed bend proximal to the J-shaped bend at the distal end of the lead and directed in an opposite direction or it may be accomplished by other mechanisms, for example, by manufacturing the lead such that the curved portion of the lead carrying the elongated coil electrode is of greater rigidity than the portion of the lead immediately proximal thereto which in turn will encourage the lead to display a similar configuration as implanted.
An additional mechanism for reducing the slew rate of the ventricular signals sensed at the ends of the indifferent electrode is to provide a conductivity reducing coating on one or both end portions of the indifferent electrode. This mechanism may be employed as a substitute or in addition to provision of a spatially dispersed indifferent electrode and/or configuring the indifferent electrode so that the ends of the electrodes are directed away from the ventricles.
REFERENCES:
patent: 4374527 (1983-02-01), Iversen
patent: 4387717 (1983-06-01), Brownlee et al.
patent: 4402328 (1983-09-01), Doring
patent: 4414986 (1983-11-01), Dickhudt et al.
patent: 4506680 (1985-03-01), Stokes
patent: 4641656 (1987-02-01), Smits
patent: 4972848 (1990-11-01), DiDomenico et al.
patent: 5282844 (1994-02-01), Stokes et al.
patent: 5423772 (1995-06-01), Lurie et al.
patent: 5423865 (1995-06-01), Bowald et al.
patent: 5433729 (1995-07-01), Adams et al.
patent: 5445148 (1995-08-01), Jaraczewski et al.
patent: 5476498 (1995-12-01), Ayers
p
Min Xiaoyi
Morris Mary M.
Duthler Reed
Medtronic Inc.
Schaetzle Kennedy
Wolde-Michael Girma
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Kirshna
It would be interesting to do a sthiagrt ROI analysis for this given this data. For example, if a wind turbine cost $2 million, to make back the $2 million and then finally start making a profit, there would have to be X amount of kWh generated per day to keep pace with the expected ROI. For every day where no electricity is generated then that will set back the ROI schedule or place a greater output per turbine to keep on track for the ROI.So in other words, how or why would anyone want to put an investment into an energy source that is as fickle as the wind? Proponents may say that collectively the wind is always blowing, thus to make the investment less risky, you have to place bets on many turbines to accumulate an expected (an optimistic) generation rate of 25% of collective capacity.I don't know the details of the subsidies that wind is given, but my hunch is that without those incentives, wind power is a no go. This was basically stated by T Boone Pickens before. T Boone got into the wind game because of this, the risk was reduced to nil for him and if his "plan" worked then it would provide a huge new business for his gas sales.
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