IMPROVED MONITOR OF HEART FAILURE USING BIOIMPEDANCE

• US 20110245712A1
• Filed: 10/09/2009
• Published: 10/06/2011
• Est. Priority Date: 10/10/2008
• Status: Active Grant

• Current Assignee: Regents of The University of Minnesota (University of Minnesota)
• Original Assignee: Regents of The University of Minnesota (University of Minnesota)
• Inventors: Patterson, Robert, Yang, Fei
• Granted Patent: US 8,731,653 B2
• Time in Patent Office: Days
• US Class Current: 600/547
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/4878 Evaluating oedema
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance

Abstract

In a method of monitoring pulmonary edema in a human being, an electrical current is injected between a first electrode located in or around a heart and a housing of a medical device implanted in a chest region. A voltage potential is measured between a second electrode in a superior vena cava and a third electrode in the superior vena cava, where the voltage potential is created by the electrical current. Pulmonary edema is assessed based on an impedance value calculated from the electrical current and the voltage potential and a stored edema threshold impedance value.

Claims

1. A method of monitoring pulmonary edema in a human being, the method comprising:

injecting an electrical current between a first electrode located in or around a heart and a housing of a medical device implanted in a chest region;

measuring a voltage potential between a second electrode in a superior vena cava and a third electrode in the superior vena cava, the voltage potential created by the electrical current; and

assessing pulmonary edema based on an impedance value calculated from the electrical current and the voltage potential and a stored edema threshold impedance value.

2. The method of claim 1, wherein the injected electrical current is a cardiac pacing pulse configured to initiate a cardiac cycle.

3. The method of claim 1, wherein the injected electrical current is configured such that a cardiac cycle is not initiated in response to injection of the electrical current.

4. The method of claim 1, wherein the second electrode and the third electrode are positioned on a lead, a distal end of which is located in a right ventricle.

5. The method of claim 1, further comprising measuring a second voltage potential between a fourth electrode in the vena cava and either the second electrode or the third electrode, and wherein the assessing pulmonary edema further comprises calculating a second impedance value based on the electrical current and the second voltage potential.

6. The method of claim 5, further comprising assessing heart enlargement based on the calculated impedance values.

7. The method of claim 6, wherein relative contributions to impedance changes attributable to pulmonary edema and heart enlargement are determined by solving a system equations using the calculated impedance values and predetermined coefficients.

8. The method of claim 5, wherein two of the second electrode, third electrode and fourth electrode are positioned on a first lead and the remaining electrode is positioned on a second lead.

9. The method of claim 5, wherein each of the second, third and fourth electrodes is positioned on a single lead.

10. The method of claim 1, wherein the current injection, voltage measurement, and impedance value calculation is repeated on a periodic basis and the assessing pulmonary edema includes assessing a change in edema based on two or more of the calculated impedance values.

11. A method of monitoring pulmonary edema in a human being, the method comprising:

injecting an electrical current between a first electrode located in a right ventricle of a heart and a housing of a medical device implanted in a chest region;

measuring a voltage potential between a second electrode in a superior vena cava and a third electrode in the superior vena cava, the voltage potential created by the electrical current; and

assessing pulmonary edema based on an impedance value calculated from the electrical current and the voltage potential and a stored edema threshold impedance value.

12. A method of monitoring pulmonary edema in a human being, the method comprising:

injecting an electrical current between a first electrode located in a coronary vein of a left ventricle of a heart and a housing of a medical device implanted in a chest region;

measuring a voltage potential between a second electrode in a superior vena cava and a third electrode in the superior vena cava, the voltage potential created by the electrical current; and

assessing pulmonary edema based on an impedance value calculated from the electrical current and the voltage potential and a stored edema threshold impedance value.

13. An implantable medical device, comprising:

a housing for the implantable device sized for implantation in a chest region of a patient and comprising a housing electrode;

a lead port into which a proximal end of a lead is connectable, the lead having first, second, and third conductors that are insulated from one another and that extend from the proximal end of the lead to corresponding first, second, and third electrodes, the third electrode positioned near a distal end of the lead for location in or around a heart, the first and second electrodes positioned on the lead for location in a superior vena cava;

an electrical impedance measurement circuit electrically connected to the lead port and the housing electrode, the circuit comprising a current generator, a voltage amplifier and a control module, the current generator designed to inject an electrical current between the third electrode located in or around the heart and the housing electrode, the voltage amplifier designed to measure a voltage potential between the first and second electrodes located in the superior vena cava, wherein the voltage potential is created by the electrical current, and the control module designed to assess pulmonary edema based on an impedance value calculated from the electrical current and the voltage potential and a stored edema threshold impedance value.

14. The device of claim 13, wherein the injected electrical current is a cardiac pacing pulse configured to initiate a cardiac cycle.

15. The device of claim 13, wherein the injected electrical current is configured such that a cardiac cycle is not initiated in response to injection of the electrical current.

16. The device of claim 13, wherein the current injection, voltage measurement, and impedance value calculation is repeated on a periodic basis and the assessing pulmonary edema includes assessing a change in edema based on two or more of the calculated impedance values.

17. The device of claim 16, wherein the control module is further designed to assess heart enlargement based on the calculated impedance values.

18. The device of claim 17, wherein relative contributions to impedance changes attributable to pulmonary edema and heart enlargement are determined by solving a system equations using the calculated impedance values and predetermined coefficients.