Rate-responsive pacemaker with rapid minute volume determination

• US 5,824,020 A
• Filed: 05/02/1997
• Issued: 10/20/1998
• Est. Priority Date: 05/02/1997
• Status: Expired due to Term

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Inventors: Cooper, Daniel
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): LAYNO, CARL HERNANDZ
• Application Number:
  US08/850,557
• Time in Patent Office: 536 Days
• Field of Search: 607/17-19
• US Class Current: 607/17
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance

Abstract

A rate responsive pacemaker with improved response to exercise onset includes a detector for detecting a metabolic parameter indicative of the patient'"'"'s metabolic demand. The metabolic demand parameter derived therefrom is analyzed either using a heart rate sensitive zero crossing detector or a derivative calculator and used to generate an optimized pacing rate.

Claims

1. An implantable pacemaker comprising:

a. a cardiac sensor for sensing intrinsic activity in a patient'"'"'s heart and generating a sensed signal;

b. a pacing generator for generating pacing pulses in response to pacing commands;

c. a metabolic demand generator for generating a metabolic demand signal indicative of the metabolic demand of the patient; and

d. a controller for generating said commands corresponding to said sensed and metabolic demand signals;

wherein said metabolic demand generator includes

i. a metabolic sensor for generating a metabolic detected signal;

ii. a metabolic detected signal processor for processing said metabolic detected signal in accordance with one of a paced and sensed heart rate, said signal processor including a derivative calculator for calculating a derivative of said metabolic detected signal; and

iii. a signal generator for generating said demand signal based on said derivative and said sensed signal whereby said command signals have a fast response to exercise onset.

2. The pacemaker of claim 1 wherein said signal processor includes a zero crossing sensor for sensing zero crossings of said metabolic detected signal.

3. The pacemaker of claim 1 wherein said metabolic detected signal comprises a thoracic impedance.

4. The pacemaker of claim 1 wherein said metabolic detected signal comprises related to a tidal volume signal.

5. The pacemaker of claim 1 wherein said signal processor includes a breath sensor for sensing a respiration rate of the patient.

6. An implantable pacemaker comprising:

a. a sensor for sensing intrinsic activity in a patient'"'"'s heart and generating a sensed signal;

b. a pacing generator for generating pacing pulses in response to pacing commands;

c. a metabolic demand generator for generating a metabolic demand signal indicative of the metabolic demand of the patient; and

d. a controller for generating said commands corresponding to said sensed and metabolic demand signals;

wherein said metabolic demand generator includes

i. a metabolic sensor for generating a metabolic detected signal, said metabolic detected signal having zero crossings; and

ii. a metabolic detected signal processor for processing said metabolic detected signal into a metabolic demand signal, said processor being a fuzzy logic circuit and including a zero crossing detector for sensing said zero crossings in accordance with one of a paced and sensed heart rate.

7. The pacemaker of claim 6 wherein said zero crossing detector is constructed and arranged to adapt to said pacing and sensed heart rate.

8. An implantable pacemaker comprising:

a. a sensor for sensing intrinsic activity in a patient'"'"'s heart and generating a sensed signal;

b. a pacing generator for generating pacing pulses in response to pacing commands;

c. a metabolic demand generator for generating a metabolic demand signal indicative of the metabolic demand of the patient; and

d. a controller for generating said commands corresponding to said sensed and metabolic demand signals;

wherein said metabolic demand generator includes

i. a metabolic sensor for generating a thoracic impedance signal;

ii. a metabolic detected signal processor for processing said thoracic impedance signals characterized by thoracic impedance values, said processor including an accumulator for accumulating a plurality of values; and

iii. a signal generator for generating said demand signal based on an output of said accumulator;

wherein said signal generator generates said demand signal using a rate response function, said rate response function being an exponential curve.

9. The pacemaker of claim 8 wherein said processor further includes a moving average generator for generating a moving average of said values, said moving average being used to normalize said thoracic impedance signal with a baseline.

10. The pacemaker of claim 8 wherein said controller includes an interval detector for detecting an RR interval between intrinsic cardiac events and a tidal volume generator generating a tidal volume signal, said RR interval and said tidal volume signals being indicative of said thoracic impedance.

11. The pacemaker of claim 10 further comprising a noise sensing circuit, said RR interval and said tidal volume signals being adjusted to compensate for said noise signal.