AUTOMATIC SELECTION OF ELECTRODE VECTORS FOR ASSESSING RISK OF HEART FAILURE DECOMPENSATION EVENTS

• US 20130197381A1
• Filed: 01/29/2013
• Published: 08/01/2013
• Est. Priority Date: 01/31/2012
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Charlton, Sandra B., Sims, James J.
• Granted Patent: US 9,560,980 B2
• Time in Patent Office: Days
• US Class Current: 600/523
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/341 Vectorcardiography [VCG]
• CPC Class Codes: A61B 5/4875 Hydration status, fluid retention of the body
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61B 5/7275 Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
• CPC Class Codes: G16H 40/67 for remote operation
• CPC Class Codes: G16H 50/30 for calculating health indices; for individual health risk assessment

Abstract

An implantable medical device (IMD) is implanted in a patient. The IMD uses a plurality of electrode vectors to generate intrathoracic impedance measurements. The intrathoracic impedance measurements can be indicative of amounts of intrathoracic fluid in the patient. An accumulation of intrathoracic fluid may indicate that the patient is at an increased risk of experiencing a heart failure event in the near future. The IMD performs a vector selection operation on a recurring basis. When the IMD performs the vector selection operation, the IMD uses impedance measurements to select one of the electrode vectors. The IMD can perform a risk assessment operation on another recurring basis. During performance of the risk assessment operation, the IMD uses impedance measurements of the selected electrode vector and/or other patient characteristics stored within the IMD to determine whether the patient is at an increased risk of experiencing a heart failure event.

Claims

1. A method for determining a risk of a patient experiencing a heart failure decompensation event in the near future, the method comprising:

using, by a medical device implanted in the patient, a plurality of electrode vectors to generate a plurality of intrathoracic impedance measurements, each of the electrode vectors being a different combination of electrodes;

performing, by the medical device, a vector selection operation on a first recurring basis, wherein each time the medical device performs the vector selection operation, the medical device selects a given electrode vector from among the plurality of electrode vectors, the intrathoracic impedance measurements generated using the given electrode vector being at a current time likely to be more reliable than the intrathoracic impedance measurements generated using other ones of the electrode vectors for determining the risk; and

performing, by the medical device, a risk assessment operation on a second recurring basis, wherein each time the medical device performs the risk assessment operation, the medical device determines the risk based at least in part on intrathoracic impedance measurements generated using one of the electrode vectors that was selected during a most recent performance of the vector selection operation.

2. The method of claim 1, wherein when the medical device performs the risk assessment operation, the medical device does not determine the risk based on impedance measurements generated using ones of the electrode vectors that were not selected during the most recent performance of the vector selection operation.

3. The method of claim 1, wherein performing the vector selection operation comprises:

assigning vector scores to the electrode vectors;

ranking the electrode vectors based on the vector scores assigned to the electrode vectors; and

selecting the given electrode vector when the given electrode vector is a highest-ranked electrode vector.

4. The method of claim 3, wherein assigning vector scores to the electrode vectors comprises:

assigning the vector scores to the electrode vectors based at least in part on signal-to-noise ratios of the electrode vectors.

5. The method of claim 3, wherein performing the vector selection operation further comprises:

determining whether there is a tie among top-ranked ones of the electrode vectors; and

after determining that there is a tie among the top-ranked electrode vectors, selecting one of the top-ranked electrode vectors based at least in part on a default ranking of the electrode vectors.

6. The method of claim 1, wherein performing the vector selection operation comprises:

selecting a first electrode vector from among the plurality of electrode vectors;

after selecting the first electrode vector, determining whether the first electrode vector has one or more disqualifying characteristics; and

selecting a second electrode vector from among the plurality of electrode vectors after determining that the first electrode vector has one or more disqualifying characteristics.

7. The method of claim 1, further comprising:

transmitting a vector suggestion message to a programmer after performing the vector selection operation; and

after transmitting the vector suggestion message, receiving a vector selection message from the programmer, the vector selection message specifying the given vector or another one of the electrode vectors; and

wherein performing the risk assessment operation comprises;

if the vector selection message specifies the given vector, using impedance measurements of the given vector to determine the risk; and

if the vector selection message specifies the other one of the electrode vectors, using impedance measurements generated using another one of the electrode vectors to determine the heart failure risk.

8. The method of claim 1, wherein performing the vector selection operation on a first recurring basis comprises performing the vector selection operation whenever a recurrence period has expired.

9. The method of claim 1, wherein the first recurring basis is longer than the second recurring basis.

10. The method of claim 1, wherein performing the risk assessment operation comprises using intrathoracic impedance measurements generated using another one of the electrode vectors to confirm the risk.

11. An implantable medical device (IMD) implanted in a patient, the IMD comprising:

a plurality of electrodes; and

a processor that is configured to;

use a plurality of electrode vectors to generate a plurality of intrathoracic impedance measurements, each of the electrode vectors being a different combination of the electrodes;

perform a vector selection operation on a first recurring basis, wherein each time the processor performs the vector selection operation, the processor selects a given electrode vector from among the plurality of electrode vectors, the intrathoracic impedance measurements generated using the given electrode vector being at a current time likely to be more reliable than the intrathoracic impedance measurements generated using other ones of the electrode vectors for determining the risk; and

perform a risk assessment operation on a second recurring basis, wherein each time the processor performs the risk assessment operation, the processor determines the risk based at least in part on intrathoracic impedance measurements generated using one of the electrode vectors that was selected during a most recent performance of the vector selection operation.

12. The IMD of claim 11, wherein when the processor performs the risk assessment operation, the processor does not determine the risk based on impedance measurements generated using ones of the electrode vectors that were not selected during the most recent performance of the vector selection operation.

13. The IMD of claim 11, wherein when the processor performs the vector selection operations, the processor:

assigns vector scores to the electrode vectors;

ranks the electrode vectors based on the vector scores assigned to the electrode vectors; and

selects the given electrode vector when the given electrode vector is a highest-ranked electrode vector.

14. The IMD of claim 13, wherein when the processor assigns the vector scores to the electrode vectors, the processor assigns the vector scores to the electrode vectors based at least in part on signal-to-noise ratios of the electrode vectors.

15. The IMD of claim 13, wherein when the processor performs the vector selection operation, the processor:

determines whether there is a tie among top-ranked ones of the electrode vectors; and

after determining that there is a tie among the top-ranked electrode vectors, selects one of the top-ranked electrode vectors based on a default ranking of the electrode vectors.

16. The IMD of claim 11, wherein when the processor performs the vector selection operation, the processor:

selects a first electrode vector from among the plurality of electrode vectors;

after selecting the first electrode vector, determines whether the first electrode vector has one or more disqualifying characteristics; and

selects a second electrode vector from among the plurality of electrode vectors after determining that the first electrode vector has one or more disqualifying characteristics.

17. The IMD of claim 11,

wherein the processor is further configured to:

cause a telemetry unit of the IMD to transmit a vector suggestion message to a programmer after performing the vector selection operation; and

after transmitting the vector suggestion message, receive a vector selection message from the programmer, the vector selection message specifying the given vector or another one of the electrode vectors;

wherein when the processor performs the risk assessment operation, the processor;

uses impedance measurements of the given vector to determine the risk when the vector selection message specifies the given vector; and

uses impedance measurements generated using another one of the electrode vectors to determine the heart failure risk when the vector selection message specifies the other one of the electrode vectors.

18. The IMD of claim 11, wherein when the processor performs the vector selection operation on a first recurring basis, the processor performs the vector selection operation whenever a recurrence time interval expires.

19. The IMD of claim 11, wherein the first recurring basis being longer than the second recurring basis.

20. The IMD of claim 11, wherein when the processor performs the risk assessment operation, the processor uses intrathoracic impedance measurements generated using another one of the electrode vectors to confirm the risk.

21. An implantable medical device (IMD) implanted in a patient, the IMD comprising:

a plurality of electrodes;

means for using a plurality of electrode vectors to generate a plurality of intrathoracic impedance measurements, each of the electrode vectors being a different combination of the electrodes;

means for performing a vector selection operation on a first recurring basis, wherein each time the processor performs the vector selection operation, the processor selects a given electrode vector from among the plurality of electrode vectors, the intrathoracic impedance measurements generated using the given electrode vector being at a current time likely to be more reliable than the intrathoracic impedance measurements generated using other ones of the electrode vectors for determining the risk; and

means for performing a risk assessment operation on a second recurring basis, wherein each time the processor performs the risk assessment operation, the processor determines the risk based at least in part on intrathoracic impedance measurements generated using one of the electrode vectors that was selected during a most recent performance of the vector selection operation.

22. A computer readable medium that stores instructions, execution of the instructions causing an implantable medical device (IMD) implanted in a patient to:

use a plurality of electrode vectors to generate a plurality of intrathoracic impedance measurements, each of the electrode vectors being a different combination of electrodes;

perform a vector selection operation on a first recurring basis, wherein each time the medical device performs the vector selection operation, the medical device selects a given electrode vector from among the plurality of electrode vectors, the intrathoracic impedance measurements generated using the given electrode vector being at a current time likely to be more reliable than the intrathoracic impedance measurements generated using other ones of the electrode vectors for determining the risk; and

perform a risk assessment operation on a second recurring basis, wherein each time the medical device performs the risk assessment operation, the medical device determines the risk based at least in part on intrathoracic impedance measurements generated using one of the electrode vectors that was selected during a most recent performance of the vector selection operation.