Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-08-13
2001-02-06
Getzow, Scott M. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06185459
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the field of implantable stimulators and more particularly to cardiac pacemakers and implantable anti-arrhythmia devices.
It has been proposed to reduce the incidence of tachyarrhythmias in the ventricle by using multiple site pacing. For example, in U.S. Pat. No. 3,937,226, issued to Funke, multiple electrodes are provided for location around the ventricles. In response to a sensed depolarization following a refractory period, at any of the electrodes, all electrodes are paced. All electrodes are similarly paced in the absence of sensed depolarizations for a period of 1000 ms. U.S. Pat. No. 4,088,140 issued to Rockland et al discloses a similar device, in which a pacing pulse is delivered only to a single electrode in response to a failure to sense during a 1000 ms period, and delivery of pacing pulses to multiple electrodes is triggered in response to sensed depolarizations occurring between 150 and 500 ms following delivery of a previous sensed depolarization or pacing pulse. U.S. Pat. No. 4,354,497, issued to Kahn adds sensing electrodes adjacent the septum of the heart and delivers pacing pulses to multiple electrodes spaced around the ventricles in response to sensed depolarizations at the ventricular electrodes which are not preceded by depolarizations sensed at the septum electrodes. Multi-site pacing in the ventricles has also been proposed to improve hemodynamic function, as in U.S. Pat. No. 4,928,688, issued to Mower. The Funke, Kahn, Rockland and Mower patents are all hereby incorporated herein by reference in their entireties.
Multi-site atrial pacing has also been proposed as a mechanism for reducing the incidence of atrial tachyarrhythmias. For example, multi-site pacing for arrhythmia prevention is discussed in U.S. Pat. No. 5,584,867, issued to Limousin et at, U.S. Pat. No. 5,683,429 issued to Mehra and U.S. Pat. No. 5,403,356, issued to Hill et al. and in the article “Prevention of Atrial Tachyarrhythmias Related to Advanced Inter-atrial Block by Permanent Atrial Resynchronization”, by Mabo, et al, published in
Pace,
Vol. 14, April 1991, Part II, p 648. The Limousin, Mehra and Hill et al. patents are hereby incorporated herein by reference in their entireties.
Pacing methodologies employing only a single pacing site have also been proposed for prevention of tachyarrhythmias. For example, U.S. Pat. No. 4,941,471 issued to Mehra discloses a single site rate stabilization pacing method for use in the ventricles. An improvement to this pacing methodology is disclosed in U.S. Pat. No. 5,545,185 issued to Denker et al, and further improvements are disclosed in U.S. Pat. No. 5,814,085 issued to Hill, and U.S. patent application Ser. No. 08/764,568, filed on Dec. 16, 1996 by Peterson et al. An additional atrial overdrive arrhythmia prevention pacing mode which is disclosed in U.S. Pat. No. 5,713,929, issued to Hess et al. The Mehra, Hill, Hess et al. and Denker patents, as well as the Peterson et al. application are all hereby incorporated herein by reference in their entireties.
SUMMARY OF THE INVENTION
The present invention is directed toward preventing the occurrence of atrial or ventricular tachyarrhythmias by means of a pacemaker having the capability of delivering tachyarrhythmia prevention pacing therapies at single or at multiple locations within the atria and/or ventricles. The present invention accomplishes this desired goal by means of control and timing circuits and methods of operation which provide for optimization of the delivered pacing therapy by choosing which therapy, which electrodes and which pacing sites are employed, from among those available for tachyarrhythmia prevention pacing. The timing and control circuitry includes means for tracking the occurrences of tachyarrhythmias over defined extended time periods, such as days, weeks or months.
Pacing at multiple sites may be accomplished by delivering pacing pulses through separate electrode pairs, each pair located adjacent a different site within the atria or within the ventricles, may be accomplished by delivering pacing pulses between electrodes located adjacent different sites within the atria or within the ventricles or may be accomplished by delivering pulses between individual electrodes in the atria or ventricles and remote indifferent electrodes. The device may employ single or multi-site pacing in the atria, the ventricles, or in both the atria and the ventricles, with separate prioritized lists of therapies and/or electrodes and polarities programmed for the atria and the ventricles and may employ separate counts or durations of occurrences of tachyarrhythmia in the atria and the ventricles in order to induce switching of the electrode configurations used to pace the atria and the ventricles, independent of one another.
In some embodiments, in response to detection of a predetermined number of occurrences of tachyarrhythmias within a defined extended time period and/or detection of a predefined cumulative duration of tachyarrhythmias within the defined extended time period, the selection of pacing therapy and/or interconnection of the electrodes available for pacing is modified to disable a tachyarrhythmia prevention therapy and/or to change the tachyarrhythmia prevention therapy. With each subsequent detection of a defined number and/or cumulative duration of tachyarrhythmias within the a defined extended time period, the device may switch to another available therapy and/or set of electrodes and pacing sites until an effective tachyarrhythmia therapy is selected or until all available therapies have been determined to be ineffective.
For example, in a device embodied in the form of a multi-site atrial pacemaker having electrodes positioned to stimulate at two different locations within the atria, the device may initially employ first and second electrodes in contact with atrial tissue to stimulate at both locations using the pacing method disclosed in the above-cited Mehra et al '429 patent, and then, in response to detection of a defined number of occurrences and/or a defined cumulative duration of tachyarrhythmia within the defined extended time period, the pacemaker may employ the second electrode, in conjunction with an indifferent electrode to stimulate only the second location using the pacing method disclosed in the above-cited Mehra '471 patent.
In some preferred embodiments of the invention, upon detection of a defined number of occurrences of tachyarrhythmias and/or a defined cumulative total duration of tachyarrhythmias in the atria or the ventricles within a defined extended time period, the device checks to see if there is an available therapy and/or set of electrodes and polarities which offer the opportunity of reducing the frequency or duration of tachyarrhythmias. In these embodiments, a therapy and/or an associated set of electrodes and polarities not previously employed will, by definition, be considered as offering the possibility of reducing the frequency or duration of tachyarrhythmias. In addition, the device may record information with regard to the frequency and durations of occurrences of tachyarrhythmia in conjunction with a particular therapy and/or associated set of electrodes and polarities, and may consider any previously employed therapies and/or sets of electrodes and polarities as offering an opportunity for reducing the frequency or duration of tachyarrhythmias if the associated recorded information indicates reduced frequency or duration of tachyarrhythmias as compared to the electrodes and polarities currently being employed.
In other preferred embodiments of the invention the device automatically determines whether any tachyarrhythmia prevention therapy is desirable and, if so which therapy and/or set of electrodes and polarities will be initially employed, based upon the frequency and durations of occurrences of tachyarrhythmia in conjunction with the particular therapies and/or associated sets of electrodes and polarities available. In these embodiments the de
Fitts Stephanie M.
Hill Michael R. S.
Mehra Rahul
Mongeon Luc R.
Duthler Reed A.
Getzow Scott M.
Medtronic Inc.
Patton Harold R.
Wolde-Michael Girma
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