Active implantable medical device including means for the evaluation of intracardiac volume

• US 20060116591A1
• Filed: 08/18/2005
• Published: 06/01/2006
• Est. Priority Date: 08/18/2004
• Status: Active Grant

• Current Assignee: Ela Medical S.A. (LivaNova Plc)
• Original Assignee: Ela Medical S.A. (LivaNova Plc)
• Inventors: Cooper, Daniel
• Granted Patent: US 7,410,467 B2
• Time in Patent Office: Days
• US Class Current: 600/508
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance

Abstract

An active implantable medical device having a plurality of connection terminals able to be connected to electrodes placed in at least three distinct respective sites in a myocardium; circuits for measuring an intracardiac bio-impedance, comprising circuits for injecting a current and circuits for collecting a voltage at respective poles of a configuration of said connection terminals, and circuits able to deliver at an output a dynamic impedance signal that is a function of the injected current and the collected voltage; and circuits for evaluating an intracardiac volume, receiving at in input the impedance signal and delivering at an output a dynamic value of volume representing an instantaneous absolute value of intracardiac volume.

Claims

1. An active implantable medical device comprising:

a plurality of connection terminals able to be connected to electrodes placed in at least three distinct respective sites in a myocardium;

means for measuring an intracardiac bio-impedance, comprising means for injecting a current, means for collecting a voltage at selected ones of said plurality of connection terminals, and means able to deliver at an output a dynamic impedance signal that is a function of the injected current and the collected voltage; and

means for evaluating an intracardiac volume, said means receiving at an input the impedance signal and delivering at an output a dynamic value of volume representing an instantaneous absolute value of intracardiac volume.

2. The device of claim 1, in which the means for evaluating an intercardiac volume further comprises means for converting the impedance signal into a volume according to a linear characteristic in the form Vol=(a*Z)+b, wherein Vol is the value of volume delivered by the means for evaluating, Z is the value of the impedance signal received at input, and a and b are constants.

3. The device of claim 2, further comprising calibration means for determining constants a and b based upon at least two values of measured volume and at least two values of measured impedance.

4. The device of claim 1, in which the means for evaluating an intercardiac volume further comprises means for converting the impedance signal into a volume according to a hyperbolic characteristic in the form Vol=a/(Z+b), wherein Vol is the value of volume delivered by the means for evaluating, Z is the value of the impedance signal received at input, and a and b are constants.

5. The device of claim 4, further comprising calibration means, for determining constants a and b based upon at least two values of measured volume and at least two values of measured impedance.

6. An active implantable medical device comprising:

a plurality of connection terminals able to be connected to a plurality of electrodes placed in at least three distinctive sites in a myocardium; and

means for measuring an intracardiac bio-impedance comprising;

a current source having an output current pulse;

a voltage detector having an output signal responsive to a voltage detected at selected ones of said connector terminals in response to an output current pulse;

a first converter circuit responsive to the detected voltage having an output corresponding to a dynamic impedance signal; and

a second converter circuit response to the dynamic impedance signal and a conversion algorithm having a dynamic output signal corresponding to an instantaneous absolute value of the intracardiac volume.

7. The device of claim 6 wherein the conversion algorithm further comprises a linear characteristic in the form Vol=(a*Z)+b, wherein Vol is the instantaneous volume output by the second converter circuit, Z is the dynamic impedance signal output by the first converter circuit, and a and b are constants.

8. The device of claim 7, further comprising calibration means for determining constants a and b based upon at least two values of measured volume and at least two values of measured impedance.

9. The device of claim 6 wherein the conversion algorithm further comprises a hyperbolic characteristic in the form Vol=a/(Z+b) wherein Vol is the instantaneous volume output by the second converter circuit, Z is the dynamic impedance signal output by the first converter circuit, and a and b are constants.

10. The device of claim 9, further comprising calibration means for determining constants a and b based upon at least two values of measured volume and at least two values of measured impedance.