Variation in cardiac chamber volume or pressure as a controlling parameter

• US 5,391,190 A
• Filed: 04/07/1992
• Issued: 02/21/1995
• Est. Priority Date: 03/08/1990
• Status: Expired due to Term

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Pederson, Brian D., Salo, Rodney W.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): Getzow, Scott M.
• Application Number:
  US07/864,666
• Time in Patent Office: 1,050 Days
• Field of Search: 607/23, 607/18
• US Class Current: 607/23
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: G06F 2218/00 Aspects of pattern recognition specially adapted for signal processing

Abstract

A rate adaptive cardiac pacer is described in which the impedance versus time information derived using impedance plethysmography or the pressure versus time information derived from a pressure transducer in a ventricular chamber is signal processed to recover a modulating envelope due to volume or pressure changes occasioned by respiratory activity. Either or both of the respiratory interval or respiratory depth may be combined in an appropriate rate control algorithm with other parameters also derived from the impedance versus time signal to develop a rate control signal for an implanted pacer.

Claims

1. A rate adaptive pacer comprising:

implantable pulse generator means for normally producing cardiac stimulating pulses at a predetermined lower rate;

sensing means for sensing impedance in the blood in a selected cardiac chamber;

means for producing a time varying impedance signal proportional to the intracardiac impedance sensed in the selected cardiac chamber due to the beating action of the heart;

means for extracting from the time varying impedance signal a modulation signal due to volume changes;

means for relating the modulation signal to the respiratory activity of the patient and processing the modulation signal to extract quantitative information therefrom with respect to the respiratory activity of the patient in whom the pulse generator means is implanted, the respiratory activity information including that relating both to the respiration interval (I_RESP) and the respiration depth (D_RESP) wherein the means for relating the modulation signal to I_RESP comprises a zero-crossing detector and wherein the means for relating the modulation signal to D_RESP comprises a peak to peak amplitude detector; and

means for producing a rate control signal from the processed modulation signal which, when applied to the pulse generator means, changes the rate at which the stimulating pulses are produced from the predetermined lower rate to a higher rate in accordance with a known relationship between I_RESP and D_RESP expressed as an empirical algebraic function.

2. A rate adaptive pacer comprising:

implantable pulse generator means for normally producing cardiac stimulating pulses at a predetermined lower rate;

sensor means for sensing the pressure in a selected cardiac chamber;

means for producing a time varying signal proportional to the pressure sensed in the selected cardiac chamber due to the beating action of the heart;

means for extracting from the time varying pressure signal a modulation signal due to pressure changes;

means for relating the modulation signal to the respiratory activity of the patient and extracting quantitative information therefrom relating to the respiratory activity of the patient in whom the pulse generator means is implanted, the respiratory activity information including that related to the respiration interval (I_RESP) and the respiration depth (D_RESP); and

means for producing a rate control signal from the modulation signal which, when applied to the pulse generator means, changes the rate at which said stimulating pulses are produced from said predetermined lower rate to a higher rate in accordance with a known relationship between I_RESP and D_RESP expressed as an empirical algebraic function.

3. A method for controlling a rate adaptive pacer comprising an implantable pulse generator means for normally producing cardiac stimulating pulses at a predetermined lower rate comprising the steps of:

sensing an intracardiac parameter selected from the group consisting of impedance and pressure in the blood in a selected cardiac chamber;

producing a time varying signal related to the magnitude of the intracardiac parameter sensed in the selected cardiac chamber due to the beating action of the heart;

extracting from the time varying signal from the sensed parameter a modulation signal due to the selected one of impedance volume changes or pressure changes;

relating the modulation signal to and extracting quantitative information from the modulation signal with respect to the respiratory activity of the patient in whom the pulse generator means is implanted, the respiratory activity information including that relating both to the respiration interval (I_RESP) and the respiration depth (D_RESP) wherein the modulation signal is related to I_RESP by subjecting it to a zero-crossing detector and wherein the modulation signal is related to D_RESP by processing it utilizing a peak to peak amplitude detector;

producing a rate control signal from the modulation signal which, when applied to the pulse generator means, changes the rate at which the stimulating pulses are produced from the predetermined lower rate to a higher rate in accordance with a known relationship among the selected parameter, I_RESP and D_RESP in which the modulation signal is used to generate the rate control signal to control the interval between the cardiac stimulating pulses according to an empirical algebraic relationship; and

applying the rate control signal to the pulse generator.

4. The method of claim 3 wherein the selected parameter is impedance.