Apparatus with noise classification in an implantable cardiac device by using an amplifier with a variable threshold

• US 5,891,171 A
• Filed: 10/22/1997
• Issued: 04/06/1999
• Est. Priority Date: 10/22/1997
• Status: Expired due to Term

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Wickham, John
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): SCHAETZLE, KENNEDY
• Application Number:
  US08/955,540
• Time in Patent Office: 531 Days
• Field of Search: 607/9, 607/11, 607/14, 607/2, 607/4, 607/5, 607/7, 128/901, 600/509, 600/521
• US Class Current: 607/4
• CPC Class Codes: A61B 5/283 Invasive
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/366 Detecting abnormal QRS complex, e.g. widening
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7217 of noise originating from a therapeutic or surgical apparatus, e.g. from a pacemaker
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions
• CPC Class Codes: A61N 1/39622 Pacing therapy
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

An implantable cardiac device includes electrodes for sensing and pacing the heart, and optionally, defibrillation electrodes. The IECG with a noise component sensed in the heart is processed to derive raw sense signals indicative of whether the sensed QRS complexe'"'"'s range is outside a certain range. This range is dynamically adjusted to compensate for the noise component. Preferably this range is defined by a threshold signal generator which generates a threshold signal including a first part which varies dynamically in accordance with a preset criteria and a second part which is at least equal to the peak amplitude of the noise.

Claims

1. An implantable cardiac device comprising:

a sensor sensing intrinsic cardiac activity and generating a corresponding sensed signal, said sensed signal including a noise component having a peak noise amplitude;

a pulse generator generating pulses in response to commands, said pulses being selected to provide cardiac therapy;

a signal analyzer analyzing said sensed signal to generate an output signal indicative of a relation between said sensed signal and a threshold signal;

a threshold signal generator for generating said threshold signal, said threshold signal having a threshold amplitude at least equal to said peak noise amplitude; and

a controller receiving said output signal and generating in response said commands.

2. The device of claim 1 wherein said threshold signal generator includes a feature extractor extracting said peak noise amplitude of said noise component.

3. The device of claim 1 wherein said signal analyzer is a comparator comparing said sensed signal to said threshold signal.

4. The device of claim 3 wherein said threshold generator includes an amplitude detector for detecting said peak noise amplitude.

5. The device of claim 4 wherein said threshold signal generator includes a fractional sensor for generating a fractional signal indicative of a preselected fraction of said sensed signal, and wherein said threshold signal is dependent on said fractional signal.

6. An implantable cardiac device comprising:

a sensor sensing intrinsic cardiac activity in a cardiac chamber and generating a corresponding sensed signal, said sensed signals including a noise component with a peak noise amplitude;

a pulse generator generating pulses in response to commands, said pulses being structured to provide a therapy selected from antibradycardia, antitachycardia, cardioversion and defibrillation;

an analyzer analyzing said sensed signal in comparison to a threshold signal and generating a corresponding analyzed signal;

a threshold signal generator generating said threshold signal, said threshold signal including a first part which is varied dynamically in accordance with a preset criteria and a second part which is at least equal to said peak noise amplitude; and

a controller receiving said analyzed signal and generating in response said commands.

7. The device of claim 6 wherein said threshold signal generator includes a feature extractor for extracting said peak noise amplitude.

8. The device of claim 6 wherein said threshold signal generator further includes a clipper for clipping a portion of said sensed signal before said peak amplitude is extracted.

9. The device of claim 6 wherein said threshold signal generator includes a summer for summing said first and second parts.

10. The device of claim 6 wherein said threshold signal generator further includes an offset signal generator for generating an offset signal selected to supply a safety margin, and wherein said threshold signal generator includes a summer for summing said first and second parts and said offset signal.

11. The device of claim 6 wherein said sensed signal includes a cardiac component and said noise component, and wherein said threshold signal generator includes a detector for detecting an amplitude of said cardiac component, said generator generating said first part as a fraction of said amplitude.

12. The device of claim 11 wherein said cardiac component is a biphasic signal and wherein said first threshold part includes a positive threshold signal and a negative threshold signal.