Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-12-06
2001-07-24
Getzow, Scott M. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C600S510000
Reexamination Certificate
active
06266565
ABSTRACT:
FIELD OF THE INVENTION
The invention generally relates to implantable medical devices and to external programmers used in connection therewith and in particular to methods and apparatus for processing information with an external programmer pertaining to P-waves and R-waves detected by the implantable medical device.
BACKGROUND OF THE INVENTION
Implantable medical devices, particularly pacemakers, are often configured to be used in conjunction with an external programmer which allows a physician to control the implantable medical device and to display information sensed by the device. For example, with a pacemaker, the external programmer may operate to control the parameters by which the pacemaker paces the heart and to display intracardiac electrograms (IEGMs) and other useful diagnostic information.
One example of an external programmer for use with a pacemaker is an analyzer-programmer system (APS) identified as the APS II system which is provided by St. Jude Medical CRMD of Sylmar, Calif. Components of the APS II system operate to allow a physician to program the operation of the pacemaker to, for example, control the manner by which the pacemaker detects arrhythmia conditions within the heart and responds thereto. In particular, the APS II system allows the physician to specify atrial and ventricular sensitivity threshold values with which the pacemaker senses P-waves and R-waves within, respectively, the atrium and ventricle of the heart and to further specify the mode employed by the pacemaker for pacing the heart in circumstances where expected P-waves or R-waves are not-sensed. An exemplary single-chambered pacing mode is VVI wherein both pacing and sensing is performed in the ventricle and wherein, upon detection of an R-wave, subsequent pacing within the ventricle is inhibited for a predetermined pacing interval. An exemplary dual-chambered pacing mode is VDD wherein sensing is performed in both the atrium and the ventricle but pacing is performed only in the ventricle. With the VDD mode, which is also referred to as the P tracking mode, detection of an R-wave in the ventricle triggers a pacing pulse, then further pacing is inhibited for the duration of the pacing interval. U.S. Pat. No. 5,487,755, to Snell et al. entitled “Method for Displaying a Sequential Series of Pacing Events” provides a detailed description of the operation of the APS II system of St. Jude Medical CRMD (formerly Pacesetter, Inc.) including a description of various pacing modes. U.S. Pat. No. 5,487,755 is incorporated by reference herein.
It is particularly important that the atrial and ventricular sensitivity threshold values are set optimally to ensure that P-waves and R-waves are properly detected so that the correct pacing action is taken by the pacemaker based upon the selected pacing mode. If the sensitivity threshold values are set too low, then random noise spikes may be misinterpreted as P-waves or R-waves and incorrect action may be taken by the pacemaker, perhaps resulting in the failure to provide pacing pulses when otherwise required. If the sensitivity threshold values are set too high, then P-waves or R-waves that are actually present may go undetected and again incorrect action maybe taken by the pacemaker including, for example, providing a pacing pulse when none is needed, perhaps triggering pacemaker mediated tachycardia (PMT). Although the atrial and ventricular sensitivity threshold values are typically not the only factors employed to determine whether a sensed electrical signal is a P-wave or an R-wave, the sensitivity threshold values are key factors in that determination and optimal sensitivity threshold values are critical for the safe and reliable operation of the pacemaker.
Although the aforementioned APS II system provides much useful diagnostic information to assist a physician in setting or adjusting the atrial and ventricular sensitivity values, room for further improvement remains. In particular, it would be desirable to provide a diagnostic display which allows the physician to easily visually verify that the atrial and ventricular sensitivity threshold values are properly set and it is primarily to that end that the present invention is directed. Additionally, it would be desirable to provide a method whereby the sensitivity threshold values may be automatically adjusted to a more optimal value by the pacemaker itself and aspects of the present invention are directed to that end as well.
SUMMARY OF THE INVENTION
In accordance with the present invention, a method is provided for processing information pertaining to electrical heart signals, such as P-waves and R-waves, to generate histograms representative of the information. The method is employed using an implantable medical device and an external display device, e.g., an external programmer, wherein the implantable medical device is connected to heart tissue and is capable of sensing electrical activity within the heart tissue. The method includes the steps of detecting a plurality of signals representative of electrical depolarization activity within the heart tissue connected to the implantable medical device and determining, for each respective detected signal, whether the signal corresponds to a predetermined type of heart tissue depolarization. The method also includes the steps of transmitting from the implantable medical device to the external display device, for each respective detected signal, a signal representative of the degree of depolarization of the detected signal as well as a signal indicative of whether the detected signal is of the predetermined type of heart tissue depolarization. The method additionally includes the steps of receiving the transmitted signals at the external display device, processing the signals to generate a histogram representative of the plurality of detected signals as a function of the degree of depolarization of the signals and further representative of whether the signals were determined to correspond to the predetermined type of heart tissue depolarization, and graphically displaying the histogram.
In accordance with an exemplary embodiment, wherein the implantable medical device includes a pacemaker, the predetermined type of heart tissue depolarization sensed is either a P-wave depolarization or an R-wave depolarization and separate histograms are generated for the P-waves and the R-waves. Signals that are identified as P-waves or R-waves are shown in their respective histograms as sensed signals and signals that cannot be identified as corresponding to P-waves or R-waves (e.g., because they don't satisfy a sensitivity threshold value criteria) are shown in their respective histograms as not-sensed signals. Each sensed
ot-sensed histogram also identifies portions of the sensed signals that were detected during either an alert period or a refractory period. Additionally, sensed
ot-sensed histograms are preferably provided which correspond to the current tracking (e.g., VDD, DDD) or non-tracking (e.g., DDI, VVI) mode of operation.
Also in the exemplary embodiment, the step of determining whether each signal corresponds to either a P-wave or an R-wave is performed, in part, by filtering, e.g., high-pass filtering, each signal to obtain a filtered amplitude and then comparing the filtered amplitude of each signal with a predetermined sensitivity threshold, such as 0.75 mv (millivolts). The predetermined sensitivity threshold is displayed in the histogram. The predetermined sensitivity threshold may also be adjusted based upon a comparison of a ratio of the number of sensed and not-sensed signals received as discussed further below. Such an adjustment may be triggered upon detection of an automode switching event, i.e., when the onset of an atrial tachycardia within the heart tissue is detected the pacemaker may switch from a tracking (e.g., VDD, DDD) to a non-tracking (e.g., DDI, VVI) operational mode.
Hence, with the present invention, methods are provided for graphically displaying histograms representative of sensed and not-sensed P-waves and R-waves t
Er Siew Bee
Sloman Laurence S.
Tyler James E.
Getzow Scott M.
Pacesetter Inc.
LandOfFree
Method and apparatus for detecting and displaying P-wave and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for detecting and displaying P-wave and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for detecting and displaying P-wave and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2441677