SENSING VECTOR SELECTION IN A CARDIAC STIMULUS DEVICE WITH POSTURAL ASSESSMENT

• US 20080188901A1
• Filed: 02/07/2007
• Published: 08/07/2008
• Est. Priority Date: 02/07/2007
• Status: Active Grant

• Current Assignee: Cameron Incorporated (Schlumberger NV)
• Original Assignee: Cameron Incorporated (Schlumberger NV)
• Inventors: Sanghera, Rick, Allavatam, Venugopal
• Granted Patent: US 8,200,341 B2
• Time in Patent Office: Days
• US Class Current: 607/28
• CPC Class Codes: A61B 5/1116 Determining posture transitions
• CPC Class Codes: A61B 5/283 Invasive
• CPC Class Codes: A61B 5/29 for permanent or long-term implantation
• CPC Class Codes: A61B 5/341 Vectorcardiography [VCG]
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61N 1/36535 controlled by body position or posture
• CPC Class Codes: A61N 1/368 comprising more than one electrode co-operating with different heart regions A61N1/3622, A61N1/3627 take precedence
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371
• CPC Class Codes: A61N 1/3704 Circuits specially adapted therefor, e.g. for sensitivity control
• CPC Class Codes: A61N 1/37247 User interfaces, e.g. input or presentation means
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion

Abstract

Methods, implantable medical devices and systems configured to perform analysis of captured signals from implanted electrodes to identify cardiac arrhythmias. In an illustrative embodiment, signals captured from two or more sensing vectors are analyzed, where the signals are captured with a patient in at least first and second body positions. Analysis is performed to identify primary or default sensing vectors and/or templates for event detection.

Claims

1. A method of implanting a cardiac stimulus device in a patient comprising:

physically implanting the cardiac stimulus device in the patient, including a canister and a lead system, into the patient, the canister and lead system having a plurality of electrodes that, when implanted, define at least first and second sensing vectors;

initializing the device, including activating the device; and

causing the patient to assume at least first and second body positions to allow the device to perform postural assessment of at least the first and second sensing vectors.

2. The method of claim 1, further comprising selecting a default vector for use in cardiac event detection by:

capturing sensing data along at least the first and second sensing vectors while the patient is in the first body position;

capturing sensing data along at least the first and second sensing vectors while the patient is in the second body position;

analyzing the captured sensing data; and

selecting one of the sensing vectors for monitoring cardiac activity of the patient when the patient is in any position.

3. The method of claim 2, wherein the step of selecting one of the sensing vectors for monitoring cardiac activity of the patient includes selecting a vector in which sensing data captured in each position varies less than in other vectors.

4. The method of claim 2, wherein the step of selecting one of the sensing vectors for monitoring cardiac activity of the patient includes selecting a vector using consideration of the following metrics:

amplitudes of captured signal and noise for each vector in each position; and

similarity of amplitude, for a given vector, in the first body position and the second body position.

5. The method of claim 2, wherein the step of selecting one of the sensing vectors for monitoring cardiac activity of the patient includes determining whether a valid template can be formed for performing beat comparison between a captured beat and a formed template.

6. The method of claim 5, wherein the step of determining whether a valid template can be formed includes:

capturing a series of detected events, wherein a detected event occurs when a captured signal amplitude crosses an event threshold, and a detected event includes a number of samples related to the threshold crossing; and

determining whether the series of detected events demonstrate similarity.

7. A method of selecting a vector for use in cardiac event detection in an implantable cardiac stimulus system, wherein the implantable cardiac stimulus system comprises at least three electrodes defining a plurality of sensing vectors, the electrodes being coupled to operational circuitry for the system;

the method comprising;

implanting the housing and the lead electrode assembly into a patient;

having the patient hold a first body position;

identifying a primary sensing vector;

having the patient hold a second body position; and

determining whether the primary sensing vector functions at least adequately while the patient is in the second body position.

8. The method of claim 7, wherein the step of identifying a primary sensing vector includes observing a metric of signal quality for the identified sensing vector with the patient in the first body position.

9. The method of claim 8, wherein the step of observing a metric of signal quality includes determining whether a valid template can be formed for performing beat comparison between a captured beat and a formed template.

10. The method of claim 9, wherein the step of determining whether a valid template can be formed includes:

capturing a series of detected events, wherein a detected event occurs when a captured signal amplitude crosses an event threshold, and a detected event includes a number of samples related to the threshold crossing; and

determining whether the series of detected events demonstrate similarity.

11. The method of claim 7, wherein the system includes a housing for the operational circuitry and a lead assembly attached to the housing, at least one of the electrodes being disposed on the housing and at least one of the electrodes being disposed on the lead assembly, the method further comprising implanting the housing and the lead assembly to subcutaneous, non-intrathoracic positions in the patient'"'"'s torso.

12. An implantable cardiac stimulus system comprising:

an implantable medical device including a canister housing operational circuitry coupled to at least three electrodes; and

a programmer configured to communicate with the implantable medical device after the implantable medical device is implanted in a patient;

wherein the system is configured to perform the following method after the implantable medical device is implanted in a patient such that the at least three electrodes define at least first and second sensing vectors analyzable by the operational circuitry;

the programmer indicates that the patient is to hold a first body position while a first analysis is performed;

the implantable medical device captures data using at least the first and second sensing vectors;

the implantable medical device indicates to the programmer that a first data capture for sensing vector analysis using the first and second sensing vectors is completed;

the programmer, once the implantable medical device indicates completion of the first data capture for sensing vector analysis, indicates that the patient is to hold a second body position while a second analysis is performed;

the implantable medical device again captures data using at least the first and second sensing vectors;

the implantable medical device indicates to the programmer that a second data capture for sensing vector analysis using the first and second sensing vectors is completed; and

the programmer indicates that the second analysis is complete.

13. The system of claim 12, wherein the implantable medical device is configured to perform analysis of the data captured during at least the first and second data capture and select a primary sensing vector for use in cardiac event detection.

14. The system of claim 12, wherein the implantable medical device is configured to transmit data to the programmer from the first and second data capture, and the programmer is configured to select one of the sensing vectors as a primary sensing vector for use in cardiac event detection.

15. The system of claim 12, wherein the implantable medical device is configured to perform analysis directed toward identifying cardiac events in a sensed data stream and, if difficulties occur in identifying cardiac events in the captured data, the implantable medical device is adapted to identify such difficulties, and communicate data to the programmer related to such difficulties and, if data related to difficulties in identifying cardiac events in the captured data is communicated to the programmer, the programmer is adapted to present one or more queries to an operator of the programmer in order to resolve such difficulties.

16. The system of claim 12, wherein the implantable medical device identifies primary and secondary sensing vectors.

17. An implantable cardiac stimulus system comprising:

an implantable medical device including a canister housing operational circuitry coupled to at least three electrodes;

a programmer configured to communicate with the implantable medical device when the implantable medical device is implanted in a patient;

wherein the programmer is configured to request that;

the patient hold a first body position while the implantable medical device performs first analysis from an implanted configuration defining at least two sensing vectors between the at least three electrodes, and

the patient hold a second body position while the implantable medical device performs second analysis from the implanted configuration; and

the implantable medical device is configured to;

capture data corresponding to the first and second analysis and indicate completion of the first and second analysis to the programmer such that the programmer may end corresponding requests;

select a first template representative of detection along a first template sensing vector of non-malignant cardiac activity while the patient is in the first body position;

select a second template representative of detection along a second template sensing vector of non-malignant cardiac activity while the patient is in the second body position; and

use the first and second templates to determine whether a malignant cardiac rhythm is occurring.

18. The system of claim 17, wherein the implantable medical device is configured to use the first and second templates to determine whether a malignant cardiac rhythm is occurring by the following:

comparing a captured event to the first template and, if the comparison indicates substantial dissimilarity therebetween;

comparing the captured event to the second template and, if the comparison indicates substantial dissimilarity therebetween;

determining that the captured event indicates a malignant cardiac rhythm; and

determining whether a substantial number of captured events in a defined set of captured events indicates a malignant cardiac rhythm.

19. An implantable cardiac stimulus system comprising:

an implantable medical device including a canister housing operational circuitry coupled to at least three electrodes;

a programmer configured to communicate with the implantable medical device when the implantable medical device is implanted in a patient;

wherein, once the implantable medical device is implanted in a patient such that the at least three electrodes define at least first and second sensing vectors analyzable by the operational circuitry, the system is configured to select a first sensing vector for analysis and perform the following steps to analyze the first sensing vector;

a. the programmer indicates that the patient is to hold a first body position while a first analysis is performed;

b. the implantable medical device captures data using the selected sensing vector;

c. the implantable medical device indicates to the programmer that a first data capture for sensing vector analysis using the selected sensing vector is completed;

d. the programmer, once the implantable medical device indicates completion of the first data capture, indicates that the patient is to hold a second body position while a second analysis is performed;

e. the implantable medical device captures data using the selected sensing vector;

f. the implantable medical device indicates to the programmer that a second data capture for sensing vector analysis using the selected sensing vector is completed; and

g. the programmer indicates that the second analysis is complete.

20. The system of claim 19, further configured to determine whether the selected sensing vector is suitable for detection of cardiac events in each of the body positions and, if not, the system is also configured to select a second sensing vector for analysis and repeat steps a-g.