Heart pacemaker with improved detection of electrical signals

• US 5,683,425 A
• Filed: 12/12/1995
• Issued: 11/04/1997
• Est. Priority Date: 12/12/1994
• Status: Expired due to Fees

• Current Assignee: Pacesetter AB
• Original Assignee: Pacesetter AB
• Inventors: Hauptmann, Werner
• Primary Examiner(s): Jastrzab, Jeffrey R.
• Application Number:
  US08/571,189
• Time in Patent Office: 693 Days
• Field of Search: 607/9, 128/696, 128/697, 128/708, 128/901
• US Class Current: 607/9
• CPC Class Codes: A61N 1/3704 Circuits specially adapted therefor, e.g. for sensitivity control
• CPC Class Codes: H03H 21/0018 Matched filters
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

A heart pacemaker with improved detection of electrical signals which are used for triggering pacemaker functions, has a detection circuit for registering intracardial heart signals in which certain noise signals having a generally chromatic spectrum are superimposed on the signals to be detected, the detection circuit undertaking an adaptive, non-linear noise filter of those intracardial heart signals for converting the spectrum of the noise signals into an essentially white spectrum. The signals filtered by the non-linear noise filtering are supplied to a matched filter wherein correlation of these signals with a sought signal pattern takes place.

Claims

1. In a heart pacemaker supplied with electrical signals obtained from a heart, the improvement of a system for detecting said electrical signals comprising:

means for acquiring electrical intracardial heart signals containing a signal of interest and having noise with a substantially chromatic spectrum superimposed on said signal of interest;

means for adaptive, non-linear filtering of said intracardial heart signals for converting the spectrum of the noise into a substantially white spectrum, thereby producing filtered signals; and

means for matched filtering of said filtered signals by correlating said filtered signals with a signal pattern corresponding to said signal of interest and generating a matched filter output having an amplitude indicative of the presence of said signal pattern in said filtered signal.

2. The improvement of claim 1 further comprising means for comparing said output to a threshold for generating a binary signal having a high level when said output exceeds said threshold.

3. The improvement of claim 2 further comprising means for triggering a pacemaker function when said output exceeds said threshold.

4. The improvement of claim 3 wherein said means for triggering a pacemaker function includes means for generating a trigger signal, and said improvement comprising means for extracting a sample of said signal pattern from said intracardial heart signal at a time coinciding with said trigger signal, and for chronologically adapting said means for matched filtering dependent on said sample.

5. The improvement of claim 1 wherein said electrical intracardial heart signals contain a QRS complex, and wherein said means for matched filtering comprises means for correlating said filtered signal with a QRS complex signal pattern.

6. The improvement of claim 1 wherein said means for adaptive, nonlinear filtering comprises a neural network finite impulse response filter.

7. A method for detecting said electrical signals in a heart pacemaker comprising the steps of:

acquiring electrical intracardial heart signals containing a signal of interest and having noise with a substantially chromatic spectrum superimposed on said signal of interest;

adaptively, non-linearly filtering said intracardial heart signals for converting the spectrum of the noise into a substantially white spectrum, thereby producing filtered signals; and

matched filtering said filtered signals by correlating said filtered signals with a signal pattern corresponding to said signal of interest and generating a matched filter output having an amplitude indicative of the presence of said signal pattern in said filtered signal.

8. The method of claim 7 comprising the additional steps of comparing said output to a threshold and generating a binary signal having a high level when said output exceeds said threshold.

9. The method of claim 8 comprising the additional step of triggering a pacemaker function when said output exceeds said threshold.

10. The method of claim 9, wherein the step of triggering a pacemaker function includes generating a trigger signal, and said method comprising the further steps of extracting a sample of said signal pattern from said intracardial heart signal at a time coinciding with said trigger signal, and chronologically adapting said matched filter dependent on said sample.

11. The method of claim 7 wherein said electrical intracardial heart signals contain a QRS complex, and wherein the step of matched filtering comprises correlating no filtered signal with a QRS complex signal pattern.