Cardiac pacer for pacing a human heart and pacing method

• US 4,730,618 A
• Filed: 06/16/1986
• Issued: 03/15/1988
• Est. Priority Date: 06/16/1986
• Status: Expired due to Term

• Current Assignee: Pacesetter AB
• Original Assignee: Siemens AG
• Inventors: Amundson, David C., Lekholm, Anders
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): Keegan, Timothy
• Application Number:
  US06/874,585
• Time in Patent Office: 638 Days
• Field of Search: 128/419 PG, 128/902, 128/419 PT, 128/723, 128/635, 128/697
• US Class Current: 607/20
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: Y10S 128/902 Biological signal amplifier

Abstract

A cardiac pacer which generates pacing pulses at a predetermined pacing rate includes a device for making a body activity measurement. The measured body activity signal is non-linearly amplified such that signal portions having higher amplitudes are more amplified than signal portions having lower amplitudes. The non-linearly amplified body activity signal is integrated over a period of time. The predetermined pacing rate is varied dependent on the integrated signal.

Claims

1. A cardiac pacer for pacing a human heart in a patient comprising

(a) means for generating pacing pulses at a predetermined pacing rate;

(b) means for transmitting the pacing pulses to the heart for pacing;

(c) means for making a body activity measurement of the patient;

(d) means for obtaining a body activity signal depending on the body activity measurement, said signal varying according to the body activity level;

(e) means for non-linearly amplifying all of the body activity signal such that signal portions having higher amplitudes are more amplified than signal portions having lower amplitudes;

(f) means for integrating the non-linearly amplified body activity signal over a period of time; and

(g) means for varying the predetermined pacing rate dependent on the integrated signal.

2. A cardiac pacer as claimed in claim 1, wherein said means for non-linearly amplifying the body activity signal is means for squaring the body activity signal.

3. A cardiac pacer as claimed in claim 1, wherein said integrated means integrates said body activity signal over a time period in the range of 5 to 30s.

4. A cardiac paceer as claimed in claim 1, wherein said means for obtaining a body activity signal is a means for obtaining a respiratory signal.

5. A cardiac pacer as claimed in claim 4, wherein said means for making a body activity measurement means for making a body impedance measurement.

6. A method for pacing a heart in a patient comprising the steps of:

generating pacing pulses at a predetermined pacing rate;

transmitting said pacing pulses to said heart for pacing thereof;

making a measurement of selected body activity of said patient;

generating a body activity signal in dependence upon said body activity measurement, said body activity signal varying according to the level of body activity of said patient;

non-linearly amplifying all of said body activity signal by more greatly amplifying portions of said body activity signal having higher amplitudes than portions of said signal having lower amplitudes;

integrating the non-linearly amplified body activity signal over a selected period of time; and

varying said predetermined pacing rate in dependence on said integrated signal.

7. A method as claimed in claim 6, wherein the step of non-linearly amplifying said body activity signal is further defined by squaring said body activity signal.

8. A method as claimed in claim 6, wherein the step of integrating the non-linearly amplified body activity signal is further defined by integrating said non-linearly amplified body activity signal for a period in the range of 5 to 30s.

9. A method as claimed in claim 6, wherein the step of making a measurement of the body activity of the patient is further defined by making a measurement of the respiratory activity of said patient.

10. A method as claimed in claim 9, wherein the step of making a respiratory activity measurement of said patient is further defined by making a body impedance measurement of said patient.