Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2000-03-28
2002-08-13
Schaetzle, Kennedy (Department: 3762)
Surgery
Diagnostic testing
Cardiovascular
C600S515000
Reexamination Certificate
active
06434417
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains to systems and methods for detecting bioelectrical activity. In particular, the invention relates to systems and methods for discriminating between cardiac depolarization and other sensed signals.
BACKGROUND
Cardiac rhythm management devices, such as pacemakers and implantable cardioverter/defibrillators, must accurately detect heart beats resulting from cardiac depolarization in order to perform their function. Such beat detection involves sensing a signal and then distinguishing between a signal due to cardiac depolarization and a noise signal due to either other cardiac electrical activity (e.g., abnormally conducted impulses, repolarization) or external noise. External noise sources that can generate sensed signals include electromagnetic fields in the environment and potentials produced by the patient's muscular activity. A common method for reducing the risk of mistaking one of these noise signals for a cardiac depolarization is to use a sensing threshold designed to be above the average amplitude of the noise signal but below a depolarization signal. In conventional pacemakers with sensing channels for sensing one or more heart chambers, the sensing channels must also distinguish between ventricular and atrial depolarizations. One way of facilitating this is to render a sensing channel refractory following certain events. (The term “refractory” means a no sensing condition when applied to a sensing channel, to be distinguished from the physiological refractory period of excitable tissue.) Sensing channels are rendered refractory both in order to prevent reentry into the system of an output pacing pulse (in which case the sensing amplifiers are blanked) and to prevent the misinterpretation of input data by the sensing of afterpotentials or by crosstalk between sensing channels.
Both of the above-mentioned methods for reducing the risk of oversensing, however, necessarily increase the risk of undersensing, i.e., that a depolarization event will fail to be detected. The present invention is directed toward an improved method for beat detection and discrimination that reduces the need for sensing thresholds and refractory periods.
SUMMARY OF THE INVENTION
The present invention is a system and method for detecting specific depolarization events such as occur in cardiac or other excitable tissue. It is particularly applicable to implantable cardiac devices such as pacemakers that function in response to detected heart beats, where the sensing channels of such devices are configured to sense either atrial or ventricular electrical activity in order to generate pacing pulses according to a programmed pacing mode. In accordance with the invention, cardiac electrical activity is sensed by a sensing channel to generate a sense signal. The sense signal is then processed in order to detect a specific cardiac depolarization event, such as a ventricular or atrial depolarization, by decomposing the signal into linearly independent components using orthogonal filters. A feature representing a statistical characteristic is then extracted from each signal component in synchronous fashion. The resulting feature set can then be compared with feature sets extracted from known signals (referred to as template signals) in order to identify the signal as a specific depolarization event.
In an exemplary embodiment, the sense signal is decomposed into multiple frequency components by a bandpass filter bank having passbands that correspond to the frequency components of a template signal that represents the specific cardiac depolarization event that is to be detected. In order to emphasize the high frequency components reflective of a change in signal energy, the frequency components of the sense signal are differentiated to extract a derivative signal therefrom. The sense signal frequency components are then amplitude demodulated to detect envelope signals representative of the signal energy changes in each of the passbands. The envelope signals are processed to determine if the signal energies of the passband frequency components of the sense signal increase in a phase-locked fashion. In a particular embodiment, the envelope signals are synchronously combined together by multiplying to generate a composite signal that is indicative of the detection of a depolarization event. In this manner, a cardiac depolarization event, such as an atrial or ventricular heart beat, can be reliably detected and discriminated from other signals.
REFERENCES:
patent: 3828768 (1974-08-01), Douglas
patent: 3939824 (1976-02-01), Arneson et al.
patent: 3998214 (1976-12-01), Garrison
patent: 4000461 (1976-12-01), Barber et al.
patent: 4945917 (1990-08-01), Akselrod et al.
patent: 5411529 (1995-05-01), Hudrlik
patent: 5417221 (1995-05-01), Sickler
patent: 5447519 (1995-09-01), Peterson
patent: RE35148 (1996-01-01), Lizzi
patent: 5682902 (1997-11-01), Herleikson
patent: 5738104 (1998-04-01), Lo et al.
patent: 5738105 (1998-04-01), Kroll
patent: 5778881 (1998-07-01), Sun et al.
patent: 5957857 (1999-09-01), Hartley
patent: 5984954 (1999-11-01), Cohen
patent: 6161037 (2000-12-01), Cohen
Afonso et al., Multirate Processing of the ECG using Filter Banks, 1996, Computers in Cardiology, 245-248.*
Afonso et al., Filter Bank Based ECG Beat Detection, 1996, IEEE, 1037-1038.*
Afonso et al., Filter Bank Based ECG Beat Classification, 1997, IEEE, 97-100.*
Afonso et al., Filter Bank Based Processing of the Stress ECG, 1997, IEEE, 887-888.*
Valtino X. Afonso et al. ECG Beat Detection Using Filter Banks, Feb. 1999, IEEE Transactions on Biomedical Engineering vol. 46. No. 2 pp. 192-202.
Cardiac Pacemakers Inc.
Droesch Kristen
Schaetzle Kennedy
Schwegman Lundberg Woessner & Kluth P.A.
LandOfFree
Method and system for detecting cardiac depolarization 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 system for detecting cardiac depolarization, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and system for detecting cardiac depolarization will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2938084