IMPLANTABLE SYSTEM FOR FLOW MEASUREMENT INCLUDING CHARGE AMPLIFIER

• US 20090112275A1
• Filed: 10/31/2007
• Published: 04/30/2009
• Est. Priority Date: 10/31/2007
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Breyer, Branko, Cinbis, Can, Ferek-Petric, Bozidar
• Granted Patent: US 9,042,983 B2
• Time in Patent Office: Days
• US Class Current: 607/17
• CPC Class Codes: A61B 5/027 using catheters
• CPC Class Codes: A61N 1/056 Transvascular endocardial electrode systems
• CPC Class Codes: A61N 1/36514 controlled by a physiological quantity other than heart potential, e.g. blood pressure controlled by two or more physical parameters A61N1/36585
• CPC Class Codes: A61N 1/36571 controlled by blood flow rate, e.g. blood velocity or cardiac output
• CPC Class Codes: A61N 1/37512 Pacemakers

Abstract

An implantable medical device lead having a flow measurement sensor mounted thereon is provided with a capsule mounted proximate to the sensor. The capsule is used to house electrical circuitry corresponding to the sensor in order to prevent impedance on conductors of the lead, which gradually decreases over chronic periods, from directly affecting signal transmission between the sensor and the electrical circuitry. The electrical circuitry includes a charge amplifier used for processing signals from the sensor. In some cases, the amplifier can be initially calibrated and periodically tuned so as to have consistent functioning with the sensor over chronic periods.

Claims

1. A flow measurement system comprising:

a lead adapted for implantation within a patient;

at least one flow measurement means, mounted on the lead, for detecting a flow parameter of ionic media at a detecting position in a selected detecting area when the lead is inserted into the patient;

a capsule, positioned on the lead proximate to the flow measurement means, the flow measurement means comprising at least first and second electrodes, the capsule positioned on the lead proximate to at least the first electrode;

electrical circuitry, housed within the capsule and operatively connected to the first electrode, for receiving and processing flow signals from the flow measurement means; and

a plurality of electrical conductors contained in said lead, at least one conductor having a distal end operatively connected to the electrical circuitry and having a proximal end operatively connected to a medical device.

2. A system according to claim 1, wherein the medical device comprises a cardiac electrotherapy system, wherein the selected detecting area comprises the patient'"'"'s heart, and wherein the ionic media comprises blood.

3. A system according to claim 2, wherein the detecting position comprises the tricuspid valve region of the patient'"'"'s heart and the flow parameter comprises flow velocity.

4. A system according to claim 2, wherein the medical device houses a control circuit adapted to generate flow waveforms from processed signals transmitted from the electrical circuitry and adapted to interpret the flow waveforms in assessing irregularities with respect to functioning of the patient'"'"'s heart.

5. A system according to claim 4, wherein the medical device comprises a pacemaker and the lead comprises a pacing lead having a third electrode mounted thereon and adapted for delivering electrical therapy to the patient'"'"'s heart, wherein the pacemaker houses a pulse generator that is operatively connected to both the third electrode via another of the lead conductors and the control circuit, the control circuit programmed to control delivery of electrical therapy to the patient'"'"'s heart via the pulse generator and the third electrode based on its interpretation of the generated flow waveforms.

6. A system according to claim 1, wherein the flow measurement means comprises a non-Doppler flow measurement configuration, the first electrode comprising a polarizable electrode and being disposed in the detecting position and the second electrode being disposed on the lead axially spaced from the first electrode.

7. A system according to claim 1, wherein the flow measurement means comprises a Doppler flow measurement configuration, the first and second electrodes being disposed in the detecting position and forming an annular piezo body for measuring the flow parameter by means of ultrasound.

8. A system according to claim 1, wherein the electrical circuitry therapy comprises at least one charge amplifier.

9. A system according to claim 8, wherein the charge amplifier comprises a differential charge amplifier circuit.

10. A system according to claim 8, wherein the charge amplifier comprises one or more pluralities of feedback capacitors, feedback resistors, and input resistors, each of the pluralities connected to the charge amplifier via switches.

11. A system according to claim 10, wherein the medical device comprises a control circuit operatively connected to the charge amplifier via one or more of the lead conductors, the control circuit adapted to periodically determine source capacitance of the charge amplifier and adapted to trigger one or more of the switches to adjust one or more of gain, low cutoff frequency, and high cutoff frequency of the amplifier to correspond with the determined source capacitance.

12. A system according to claim 8, wherein the electrical circuitry comprises at least one data acquisition circuit operatively connected between the charge amplifier and the at least one conductor, the at least one data acquisition circuit adapted for digitizing processed flow signals from the charge amplifier and transmitting such digitized signals to the medical device via the at least one conductor.

13. A system according to claim 1, wherein the capsule has at least an outer surface formed of an insulative, biocompatible, water resistant material.

14. A medical device having flow measurement system capable of being dynamically adjusted following implantation within a patient comprising:

a lead adapted for implantation within a patient;

at least one flow measurement means, mounted on the lead, for detecting a flow parameter of ionic media at a detecting position in a selected detecting area when the lead is inserted into the patient;

a capsule positioned on the lead proximate to the flow measurement means;

electrical circuitry housed within the capsule and operatively connected to the flow measurement means, the electrical circuitry adapted for receiving and processing flow signals from the flow measurement means, the electrical circuitry comprising at least one charge amplifier comprising one or more pluralities of electrical components, each of the pluralities connected to the charge amplifier via switches;

a medical device comprising a control circuit operatively connected to the charge amplifier, the control circuit adapted to periodically determine source capacitance of the charge amplifier and adapted to trigger one or more of the switches to adjust one or more electrical characteristics of the amplifier to correspond with the determined source capacitance; and

a plurality of electrical conductors contained in said lead, at least one conductor having a distal end operatively connected to the one or more of the switches and having a proximal end operatively connected to the control circuit, and at least another conductor having a distal end operatively connected to an output of the amplifier and having a proximal end operatively connected to the control circuit.

15. A system according to claim 14, wherein the electrical components comprise a feedback capacitor, a feedback resistor, and an input resistor.

16. A system according to claim 14, wherein the electrical characteristics comprise gain, low cutoff frequency, and high cutoff frequency.

17. A system according to claim 14, wherein the flow measurement means comprises either a non-Doppler means or a Doppler means.

18. A method of calibrating and subsequent tuning a charge amplifier in an implantable medical device having flow measurement capability comprising the steps of:

providing a medical device having an implantable lead including at least one flow measurement means and capsule positioned thereon, the means adapted for detecting a flow parameter of ionic media at a detecting position in a selected detecting area when said lead is inserted into a patient, the capsule housing electrical circuitry that is operatively connected to the flow measurement means, the electrical circuitry at least comprising a charge amplifier;

implanting the lead within the patient;

determining a baseline capacitance of the flow measurement sensor following implantation of the lead;

calibrating the charge amplifier by adjusting values of electrical components of the charge amplifier to correspond with the baseline capacitance;

determining source capacitance of the charge amplifier following use of the medical device within the patient for a period of time; and

tuning the charge amplifier if the source capacitance differs from the baseline capacitance by adjusting the values of the electrical components of the charge amplifier to correspond with the source capacitance.

19. A method according to claim 18, wherein the charge amplifier comprises one or more pluralities of feedback capacitors, feedback resistors, and input resistors of the charge amplifier, each of the pluralities connected to the charge amplifier via switches, and wherein the medical device comprises a control circuit operatively connected to the charge amplifier, wherein the calibrating and tuning steps involve the control circuit triggering one or more of the switches.

20. A method according to claim 19, wherein the triggering of one or more of the switches in the calibrating step leads to adjustment of one or more of gain, low cutoff frequency, and high cutoff frequency of the amplifier to correspond with the baseline capacitance, and the triggering of one or more of the switches in the tuning step leads to adjustment of one or more of the gain, the low cutoff frequency, and the high cutoff frequency of the amplifier to correspond with the source capacitance.