IMPLANT TRANSMITTER

• US 20110098584A1
• Filed: 08/27/2010
• Published: 04/28/2011
• Est. Priority Date: 08/22/2005
• Status: Active Grant

• Current Assignee: Scisense Inc. (Measurement Innovations Corp.)
• Original Assignee: Scisense Inc. (Measurement Innovations Corp.)
• Inventors: Wood, Kim, Maymandi-Nejad, Mohammad, Placko, Milan, Poetschke, Blair, Plouf, Peter
• Granted Patent: US 8,460,198 B2
• Time in Patent Office: Days
• US Class Current: 600/508
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/283 Invasive
• CPC Class Codes: A61N 1/3655 controlled by body or blood temperature
• CPC Class Codes: A61N 1/36564 controlled by blood pressure

Abstract

A monitoring system is provided that enables the monitoring of a heart in a living organism by continuously measuring both pressure and volume in a chamber of the heart, preferably the left ventricle (LV). The pressure and volume measurements are acquired using a single sensing tip and are communicated to a transmitting device to be wirelessly transmitted to a receiving device, wherein they are used to monitor the heart. The system may also incorporate a temperature measurement that can be transmitted with the volume and pressure measurement to provide further data for monitoring. The system may also extract an electrocardiogram (ECG) signal from the volume measurement. This allows the monitoring of up to four signals that can be used to determine the beat by beat state of cardiac output and any changes caused by disease or therapy. In addition to a compact design, the system may also incorporate an energy saving timing scheme that reduces the power required per acquisition cycle and thus increases the operational lifetime of the transmitting device.

Claims

1. A system for monitoring a heart of a living organism comprising:

a sensing tip situated within a chamber of said heart and extending therethrough, said sensing tip comprising;

a pressure sensing device comprising a highly resistive strain gauge comprising a pair of resistors configured such that the resistances of said resistors change in opposite directions during operation of said pressure sensing device, said pressure sensing device operable to obtain a pressure measurement in said chamber by compensating for an offset caused by the temperature coefficient of resistance of the resistors and the highly resistive nature of said strain gauge using a pair of current sources; and

a transmitting device for receiving said pressure measurement from said sensing tip, said transmitting device being operable to wirelessly transmit an electrical representation of said pressure measurement to a receiving station.

2. The system of claim 1, wherein the sensing tip further comprises a volume sensing device to obtain a volume measurement in said chamber, and wherein said transmitting device is further operable to receive said volume measurement and transmit an electrical representation of said volume measurement to said receiving station.

3. The system of claim 1 wherein said transmitting device is external to said heart.

4. The system of claim 1 further comprising said receiving station and a processor in communication with said receiving station for analysing said electrical representations to generate data indicative of the health of said heart.

5. The system of claim 4 wherein said data is an index computed by said processor based on said electrical representation.

6. The system of claim 4 wherein said receiving station comprises a display for displaying said data.

7. The system of claim 1 wherein said sensing tip extends along substantially the entirety of the longitudinal axis of said chamber.

8. The system of claim 1 wherein said pressure sensing device comprises a piezoresistive deflection sensor arranged on said sensing tip, said pressure measurement being sensed through flexure of said sensor.

9. The system of claim 2 wherein said volume sensing device comprises a first set of electrodes for transmitting and receiving an electrical signal through said chamber, said first set of electrodes being arranged at opposite ends of said sensing tip and flanking said pressure sensing device;

and at least one set of inner electrodes for sensing said electrical signal transmitted and received by said first set of electrodes to obtain said volume measurement, said at least one set of inner electrodes flanking said pressure sensing device and being arranged between respective ones of said first set of electrodes and said pressure sensing device.

10. The system of claim 1 wherein said system comprises an analog to digital converter, said electrical representation is analog, and said system is operable to convert said electrical representation from analog to digital using said analog to digital converter.

11. The system of claim 1 wherein said transmitting device obtains a supply of energy to enable continuous monitoring.

12. The system of claim 1 further comprising a temperature sensing device for obtaining an internal temperature measurement, said system being operable to communicate said temperature measurement to said transmitting device, and said transmitting device being operable to transmit an electrical representation of said temperature measurement to said receiving device.

13. The system of claim 2, further comprising a processor operable to obtain an electrocardiogram measurement from said volume measurement by conditioning said volume measurement to separate a noise portion of said conductance signal comprising said electrocardiogram measurement from a conductance portion of said conductance signal, and extracting said electrocardiogram measurement from said noise portion.

14. The system according to claim 1 wherein said pair of resistors and said current sources are provided in a Wheatstone bridge configuration.

15. The system according to claim 1 wherein said current sources are chosen to have temperature coefficients that cancel out the temperature coefficient of resistance and the temperature coefficient of the gauge factor of said pressure sensing device.

16. The system according to claim 2 wherein said volume sensing device comprises at least three pairs of electrodes and obtaining said volume measurement comprises selecting a first set of electrodes for transmitting and receiving an electrical signal through said chamber according to the size of said chamber and selecting a second set of electrodes from others of said at least three pairs for sensing said electrical signal to obtain said volume measurement.

17. A system for obtaining an intracardiac electrocardiogram signal comprising:

a receiver for obtaining a measurement of a conductance signal from a heart chamber in a living organism, said conductance signal indicative of the volume of said chamber;

a signal conditioner for conditioning said conductance signal to separate a noise portion of said conductance signal comprising said electrocardiogram signal from a conductance portion of said conductance signal; and

circuitry for extracting said electrocardiogram signal from said noise portion.

18. The system according to claim 17 wherein said circuitry for extracting comprises an inverter and a summing element, said electrocardiogram signal being extracted from said noise portion by inverting a conditioned conductance signal using said inverter and summing said inverted conductance signal with said conductance signal obtained from said heart chamber using said summing element.

19. The system according to claim 17 wherein said circuitry further comprises a buffer, said conductance signal obtained from said heart chamber being buffered while said conditioned signal is being generated using said buffer.