Systems and methods for tracking stroke volume using hybrid impedance configurations employing a multi-pole implantable cardiac lead
| Title: | Systems and methods for tracking stroke volume using hybrid impedance configurations employing a multi-pole implantable cardiac lead |
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| Patent Number: | 10016,607 |
| Publication Date: | July 10, 2018 |
| Appl. No: | 13/023408 |
| Application Filed: | February 08, 2011 |
| Abstract: | Techniques are provided for use with an implantable medical device for assessing stroke volume or related cardiac function parameters such as cardiac output based on impedance signals obtained using hybrid impedance configurations that exploit a multi-pole cardiac pacing/sensing lead implanted near the left ventricle. In one example, current is injected between a large and stable reference electrode and a ring electrode in the RV. The reference electrode may be, e.g., a coil electrode implanted within the superior vena cava (SVC). Impedance values are measured along a set of different sensing vectors between the reference electrode and each of the electrodes of the multi-pole LV lead. Stroke volume is then estimated and tracked within the patient using the impedance values. In this manner, a hybrid impedance detection configuration is exploited whereby one vector is used to inject current and other vectors are used to measure impedance. |
| Inventors: | Min, Xiaoyi (Thousand Oaks, CA, US) |
| Assignees: | PACESETTER, INC. (Sylmar, CA, US) |
| Claim: | 1. A method for use with an implantable medical device for implant within a patient having a lead system including a right ventricular (RV) lead and a multi-pole left ventricular (LV) lead, the method comprising: injecting current between a reference electrode and an electrode in the RV lead; measuring values representative of impedance along different sensing vectors between the reference electrode and each of a plurality of sensing electrodes of the multi-pole LV lead, wherein the values representative of impedance are obtained using measurements of an electric field caused by the injected current; and estimating a parameter representative of stroke volume within the patient from a combination of the values representative of impedance. |
| Claim: | 2. The method of claim 1 wherein the reference electrode used to inject current is a relatively large electrode compared to the sensing electrodes of the LV lead. |
| Claim: | 3. The method of claim 1 wherein the reference electrode is a superior vena cava (SVC) coil electrode. |
| Claim: | 4. The method of claim 1 wherein the plurality of sensing electrodes of the LV lead include a tip electrode and a set of ring electrodes. |
| Claim: | 5. The method of claim 4 wherein the multi-pole LV lead is quad-pole lead comprising the tip electrode and three ring electrodes. |
| Claim: | 6. The method of claim 1 wherein the electrode in the RV lead used to inject current is an RV ring electrode. |
| Claim: | 7. The method of claim 1 wherein measuring values representative of impedance includes, for each electrode “i” of the LV lead, performing the steps of: measuring impedance (Zi) values between the electrode and the reference electrode over at least one heart beat while the current is being injected; determining maximum and minimum impedance values (max Zi and min Zi) with each heartbeat; and determining a set of difference values (ΔZi) based on the maximum and minimum impedance values (max Zi and min Zi). |
| Claim: | 8. The method of claim 7 further including combining the impedance values to yield a combined impedance value by summing the set of difference values (ΔZi) to yield a combined difference value (ΔZsum). |
| Claim: | 9. The method of claim 8 wherein estimating the parameter representative of stroke volume includes estimating stroke volume. |
| Claim: | 10. The method of claim 9 wherein stroke volume is estimated from the combined difference value (ΔZsum). |
| Claim: | 11. The method of claim 1 further including detecting a heart failure parameter based on the parameter representative of stroke volume. |
| Claim: | 12. The method of claim 1 further including tracking heart failure based on the parameter representative of stroke volume. |
| Claim: | 13. The method of claim 1 further including setting pacing delays based, at least in part, on the parameter representative of stroke volume. |
| Claim: | 14. The method of claim 13 wherein the parameter representative of stroke volume is stroke volume and wherein the pacing delays are set values sufficient to increase stroke volume within the patient. |
| Claim: | 15. The method of claim 13 wherein the parameter representative of stroke volume is cardiac output and wherein pacing delays are set values sufficient to increase cardiac output within the patient. |
| Claim: | 16. The method of claim 1 wherein all of the steps are performed by the implantable medical device. |
| Claim: | 17. The method of claim 1 wherein at least some of the steps are performed by an external device based on signals received from the implantable medical device. |
| Claim: | 18. The method of claim 1 wherein the values representative of impedance include one or more of impedance, admittance, conductance and immittance. |
| Claim: | 19. A system for use with an implantable medical device for implant within a patient having a lead system including a right ventricular (RV) lead and a multi-pole left ventricular (LV) lead, the system comprising: a current injection system operative to inject current between a reference electrode and a ring electrode in the RV lead, wherein the reference electrode is a superior vena cava (SVC) coil electrode; an impedance measuring system operative to measure values representative of impedance along different sensing vectors between the reference electrode and electrodes of the multi-pole LV lead, wherein the electrodes of the LV lead include a tip electrode and a set of ring electrodes, wherein the values representative of impedance are obtained using measurements of an electric field caused by the injected current; and a stroke volume parameter estimation system operative to estimate parameters representative of stroke volume within the patient from a combination of the values representative of impedance. |
| Claim: | 20. A system for use with an implantable medical device for implant within a patient having a lead system including a right ventricular (RV) lead and a multi-pole left ventricular (LV) lead, the system comprising: means for injecting current between a reference electrode and a ring electrode in the RV lead, wherein the reference electrode is a superior vena cava (SVC) coil electrode; means for measuring values representative of impedance along different sensing vectors between the reference electrode and electrodes of the multi-pole LV lead, wherein the electrodes of the LV lead include a tip electrode and a set of ring electrodes, wherein the values representative of impedance are obtained using measurements of an electric field caused by the injected current; and means for estimating a parameter representative of stroke volume within the patient from a combination of the values representative of impedance. |
| Patent References Cited: | 6522923 February 2003 Turcott 7447543 November 2008 Belalcazar et al. 2005/0090870 April 2005 Hine et al. 2006/0271119 November 2006 Ni 2009/0157136 June 2009 Yang et al. 2009/0240298 September 2009 Lian et al. 2005039690 May 2005 |
| Other References: | Webster, J. “Medical Instrumentation: Application and Design” John Wiley and Sons Inc, Hoboken, NJ. 1998. pp. 359-371. cited by examiner M. Lippert et al.; Intracardiac Impedance as a Method for Ventricular Volume Monitoring—Investigation by a Finite-Element Model and Clinical Data, 2010. cited by applicant Mario Bocchiardo et al.; Intracardiac Impedance Monitors Stroke Volume in Resynchronization Therapy Patients, May 2010. cited by applicant Carsten Stahl, M.D., et al.; Intracardiac Impedance Monitors Hemodynamic Deterioration in a Chronic Heart Failure Pig Model, Sep. 2007. cited by applicant |
| Primary Examiner: | Behringer, Luther G |
| Accession Number: | edspgr.10016607 |
| Database: | USPTO Patent Grants |
| Language: | English |
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