Methods and apparatus for localization, diagnosis, contact or activity detection of bio-electric tissue

• US 8,521,262 B2
• Filed: 06/10/2009
• Issued: 08/27/2013
• Est. Priority Date: 07/13/2006
• Status: Expired due to Fees

• Current Assignee: Advanced Cardiovascular Systems Incorporated
• Original Assignee: Abbott Cardiovascular Systems Incorporated (Abbott Laboratories Incorporated)
• Inventors: Webler, William E.
• Primary Examiner(s): Porter, Jr., Allen
• Application Number:
  US12/482,255
• Publication Number:
  US 20090240163A1
• Time in Patent Office: 1,539 Days
• Field of Search: 600508-522
• US Class Current: 600/509
• CPC Class Codes: A61B 5/283 Invasive
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/6885 Monitoring or controlling sensor contact pressure

Abstract

Methods and apparatus for localization, diagnosis, contact or activity detection of bio-electric tissue providing improved sensitivity to the distance between a sensing electrode and bio-electric tissue and providing the means to measure the impedance of the tissue between a sensing electrode and bio-electric tissue. In accordance with the method, a controlled effective input impedance is provided to the monitor, which input impedance can be set to cause a significant portion of the bio-electric tissue signal to be dropped across the tissue between a sensing electrode and the bio-electric tissue when the two are separated by a predetermined or arbitrary distance. Various illustrative embodiments and forms of construction are disclosed.

Claims

1. A method of determining bio-electric activity of normally bio-electric tissue comprising:

causing a sensing electrode to touch a normally bio-electric cardiovascular tissue;

measuring, using a monitor with a predetermined input impedance R₁, a response voltage V_M′

with a second predetermined impedance R_N coupled between the sensing electrode and a reference electrode, and measuring a response voltage V_M with the second predetermined impedance R_N not coupled between the sensing electrode and the reference electrode, the response voltages V_M′

a and V_M being the voltages generated in response to the normally bio-electric cardiovascular tissue being touched by the sensing electrode; and

determining, by a processor, whether the normally bio-electric cardiovascular tissue is bio-electrically active or inactive, wherein determining is based on the measured values of V_M and V_M′

.

2. The method of claim 1 wherein determining whether the normally bio-electric cardiovascular tissue is bio-electrically active or inactive comprises comparing the measured value of V_M′

with a predetermined expected value of V_M′

.

3. The method of claim 1 wherein determining the bio-electric activity of the normally bio-electric cardiovascular tissue comprises comparing a difference in the measured values of V_M and V_M′

with a predetermined value of the difference.

4. The method of claim 1, further comprising:

calculating a parameter responsive to an impedance R_D of the cardiovascular tissue between the sensing electrode and a target bio-electric tissue based on the measured values of V_M and V_M′

.

5. The method of claim 4, wherein the predetermined input impedance R₁ is much larger than the second predetermined input impedance R_N, and the parameter responsive to the impedance R_D of the cardiovascular tissue between the sensing electrode and the target bio-electric tissue is determined based on an equation:

6. The method of claim 4, wherein the response voltages V_M and V_M′

are repeatedly measured, and the calculation of the parameter responsive to the impedance R_D is repeatedly updated based on updated measurements of V_M and V_M′

.

7. The method of claim 6, wherein the calculated values of the parameter responsive to the impedance R_D are displayed on a display.

8. The method of claim 7, wherein the method is carried out under processor control.

9. An apparatus, for use with an ECG monitor, the apparatus comprising:

a sensing electrode configured to touch a normally electric cardiovascular tissue;

an interface unit connectable to the sensing electrode and a reference electrode, wherein the interface unit is also connectable to at least a pair of ECG monitor inputs, the interface unit being configured to couple the sensing electrode and the reference electrode to an ECG monitor inputs having a predetermined input impedance R_I and to also impose a second predetermined input impedance R_N between the sensing electrode and the reference electrode, and being configured to measure a response voltage V_M′

with the second predetermined input impedance R_N coupled between the sensing electrode and the reference electrode and being configured to measure a response voltage V_M with the second predetermined input impedance R_N not coupled between the sensing electrode and the reference electrode, the response voltages V_M′ and

V_M being the voltages generated in response to the normally bio-electric cardiovascular tissue being touched by the sensing electrode; and

a processor being configured to determine whether the normally bio-electric cardiovascular tissue is bio-electrically active or inactive, wherein determining is based on the measured values of V_M and V_M′

.

10. The apparatus of claim 9, wherein the interface unit includes at least one switch to controllably connect and disconnect the second predetermined input impedance R_N between the sensing electrode and the reference electrode.

11. The apparatus of claim 10, wherein the at least one switch comprises a pushbutton switch.

12. The apparatus of claim 10, wherein the at least one switch comprises a plurality of switches to controllably independently connect and disconnect any of more than one predetermined impedances between the sensing electrode and the reference electrode.

13. The apparatus of claim 9, wherein the interface unit is permanently connected to the sensing electrode.

14. The apparatus of claim 9, wherein the interface unit is configured to alternately impose the second predetermined input impedance R_N between the sensing electrode and the reference electrode and not impose the second predetermined input impedance R_N between the sensing electrode and the reference electrode.

15. The apparatus of claim 14, wherein the interface unit is further configured to repeatedly calculate a parameter responsive to an impedance R_D of the cardiovascular tissue between the sensing electrode and a target bio-electric tissue as determined based on an equation:

16. The apparatus of claim 15, wherein the interface unit comprises the processor.

17. The apparatus of claim 15, further comprised of a display coupled to the processor to display the parameter responsive to the impedance R_D of the cardiovascular tissue between the sensing electrode and the target bio-electric tissue.