HEMODYNAMIC STATUS ASSESSMENT

• US 20130325359A1
• Filed: 03/18/2011
• Published: 12/05/2013
• Est. Priority Date: 03/18/2011
• Status: Active Grant

• Current Assignee: St. Jude Medical AB (Abbott Laboratories)
• Original Assignee: St. Jude Medical AB (Abbott Laboratories)
• Inventors: Jarverud, Karin, Bjorling, Anders, Hollmark, Malin, Noren, Kjell, Svensson, Tomas, Hjelm, Stefan
• Granted Patent: US 9,436,801 B2
• Time in Patent Office: Days
• US Class Current: 702/19
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/36535 controlled by body position or posture
• CPC Class Codes: G16B 40/00 ICT specially adapted for biostatistics; ICT specially adapted for bioinformatics-related machine learning or data mining, e.g. knowledge discovery or pattern finding
• CPC Class Codes: G16B 5/00 ICT specially adapted for modelling or simulations in systems biology, e.g. gene-regulatory networks, protein interaction networks or metabolic networks
• CPC Class Codes: G16H 40/63 for local operation
• CPC Class Codes: G16H 50/30 for calculating health indices; for individual health risk assessment
• CPC Class Codes: G16H 50/50 for simulation or modelling of medical disorders

Abstract

A patient-specific hemodyanmic status model is determined from impedance data collected during periods of normal and abnormal hemodynamic status by deriving parameter values of a set of multiple impedance-derivable parameters from impedance signals collected during periods of normal hemodynamic status and in connection with periods of abnormal hemodynamic status. The parameter values are employed to estimate coefficients of a linear parametric status model. These coefficients can then be used together with parameter values determined from impedance signals determined during status assessment periods in order to determine a current hemdoynamic status of the patient.

Claims

1. A system for determining a hemodynamic status model, the system comprising:

a lead connector electrically connectable to at least two electrodes of at least one electric lead;

a signal generator connected to the lead connector and configured to generate, during a period of normal hemodynamic status of a subject and in connection with a period of abnormal hemodynamic status of the subject, electric signals applicable over two electrodes of the at least two electrodes;

a signal sensing unit connected to the lead connector and configured to sense, during the period of normal hemodynamic status of the subject and in connection with the period of abnormal hemodynamic status of the subject, resulting electric signals over two electrodes of the at least two electrodes;

an impedance processor configured to determine a first impedance signal based on the electric signals applied and the resulting electric signals sensed during the period of normal hemodynamic status of the subject and determine a second impedance signal based on the electric signals applied and the resulting electric signals sensed in connection with the period of abnormal hemodynamic status of the subject;

a parameter processor configured to calculate first parameter values of a set of N different impedance-derivable parameters based on the first impedance signal and calculate second parameter values of the set of N different impedance-derivable parameters based on the second impedance signal, N is a positive integer equal to or larger than two;

a model processor configured to estimate, based on the first parameter values and the second parameter values, N+1 coefficients of a linear parametric status model

2. The system according to claim 1, further comprising a tachyarrhythmia detector configured to generate a tachyarrhythmia signal in response to a tachyarrhythmia period of the subject detected by the tachyarrhythmia detector based on electric signals sensed from a heart of the subject by at least one electric lead of the at least one electric lead, wherein

the signal generator is configured to generate, in connection with the period of abnormal hemodynamic status of the subject and in response to the tachyarrhythmia signal, the electric signals applicable over the two electrodes of the at least two electrodes;

and

the signal sensing unit is configured to sense, in connection with the period of abnormal hemodynamic status of the subject and in response to the tachyarrhythmia signal, the resulting electric signals over the two electrodes of the at least two electrodes.

3. The system according to claim 1, further comprising a posture sensor configured to generate a posture signal representative of a current posture of the subject, wherein the signal generator is configured to generate the electric signal when the posture signal indicates that the subject is in a predefined target posture.

4. The system according to claim 1, further comprising a posture sensor configured to generate a posture signal representative of a current posture of the subject, wherein

the signal generator is configured to generate, during the period of normal hemodynamic status of the subject and when the posture signal represents a first predefined posture of the subject, during the period of normal hemodynamic status of the subject and when the posture signal represents a second predefined posture of the subject, in connection with the period of abnormal hemodynamic status of the subject and when the posture signal represents the first predefined posture of the subject, and in connection with the period of abnormal hemodynamic status of the subject and when the posture signal represents the second predefined posture of the subject, the electric signals applicable over two electrodes of the at least two electrodes;

the signal sensing unit is configured to sense, during the period of normal hemodynamic status of the subject and when the posture signal represents the first predefined posture of the subject, during the period of normal hemodynamic status of the subject and when the posture signal represents the second predefined posture of the subject, in connection with the period of abnormal hemodynamic status of the subject and when the posture signal represents the first predefined posture of the subject, and in connection with the period of abnormal hemodynamic status of the subject and when the posture signal represents the second predefined posture of the subject, the resulting electric signals over two electrodes of the at least two electrodes;

the impedance processor is configured to determine the first impedance signal based on the electric signals applied and the resulting electric signals sensed during the period of normal hemodynamic status of the subject and when the posture signal represents the first predefined posture of the subject, determine the second impedance signal based on the electric signals applied and the resulting electric signals sensed in connection with the period of abnormal hemodynamic status of the subject and when the posture signal represents the first predefined posture of the subject, determine a third impedance signal based on the electric signals applied and the resulting electric signals sensed during the period of normal hemodynamic status of the subject and when the posture signal represents the second predefined posture of the subject, and determine a fourth impedance signal based on the electric signals applied and the resulting electric signals sensed in connection with the period of abnormal hemodynamic status of the subject and when the posture signal represents the second predefined posture of the subject;

the parameter processor is configured to calculate the first parameter values of the set of N different impedance-derivable parameters based on the first impedance signal, calculate the second parameter values of the set of N different impedance-derivable parameters based on the second impedance signal, calculate third parameter values of the set of N different impedance-derivable parameters based on the third impedance signal and calculate fourth parameter values of the set of N different impedance-derivable parameters based on the fourth impedance signal;

the model processor is configured to estimate, based on the first parameter values and the second parameter values, N+1 coefficients of a first linear parametric status model

5. The system according to claim 1, wherein

the signal generator is configured to generate, during a status assessment period, electric signals applicable over two electrodes of the at least two electrodes;

the signal sensing unit is configured to sense, during the status assessment period, resulting electric signals over two electrodes of the at least two electrodes;

the impedance processor is configured to determine an impedance signal based on the electric signals applied and the resulting electric signals sensed during the status assessment period; and

the parameter processor is configured to calculate parameter values of the set of N different impedance-derivable parameters based on the impedance signal, the system comprises a status processor configured to calculate an index representative of a current hemodynamic status of the subject based on the N+1 coefficients and the parameter values calculated by the parameter processor.

6. The system according to claim 5, further comprising:

a threshold comparator configured to compare the index calculated by the status processor with at least one threshold having a threshold value that is smaller than the predefined first value representative of normal hemodynamic status of the subject and is larger than the predefined second value representative of abnormal hemodynamic status of the subject; and

a therapy selector configured to generate a therapy signal representative of a proposed therapy for the subject based on a result of the comparison of the index with the at least one threshold as determined by the threshold comparator.

7. The system according to claim 1, wherein the system comprises:

an implantable medical device comprising the lead connector the signal generator, the signal sensing unit, the impedance processor, the memory and a transceiver configured to transmit data representative of the first impedance signal and the second impedance signal and receive data representative of the N+1 coefficients; and

a non-implantable data processing unit comprising the parameter processor, the model processor and a transceiver configured to receive the data representative of the first impedance signal and the second impedance signal and transmit data representative of the N+1 coefficients.

8. The system according to claim 1, wherein the system comprises:

an implantable medical device comprising the lead connector, the signal generator, the signal sensing unit, the impedance processor, the parameter processor, the memory and a transceiver configured to transmit data representative of the first parameter values and the second parameter values and receive data representative of the N+1 coefficients; and

a non-implantable data processing unit comprising the model processor and a transceiver configured to receive the data representative of the first parameter values and the second parameter values and transmit the data representative of the N+1 coefficients.

9. The system according to claim 1, wherein the system comprises an implantable medical device comprising the lead connector, the signal generator, the signal sensing unit, the impedance processor, the parameter processor, the model processor and the memory.

10. An implantable medical device 400) comprising:

a lead connector electrically connectable to at least two electrodes of at least one electric lead;

a signal generator connected to the lead connector and configured to generate, during a status assessment period, electric signals applicable over two electrodes of the at least two electrodes;

a signal sensing unit connected to the lead connector and configured to sense, during the status assessment period, resulting electric signals over two electrodes of the at least two electrodes;

an impedance processor configured to determine an impedance signal based on the electric signals applied and the resulting electric signals sensed during the status assessment period;

a parameter processor configured to calculate parameter values of a set of N different impedance-derivable parameters based on the impedance signal; and

a status processor configured to calculate an index representative of a current hemodynamic status of a subject based on the parameter values calculated by the parameter processor and N+1 coefficients of a linear parametric status model

11. The implantable medical device according to claim 10, further comprising:

a threshold comparator configured to compare the index calculated by the status processor with at least one threshold having a threshold value that is smaller than a predefined first value representative of normal hemodynamic status of the subject and is larger than a predefined second value representative of abnormal hemodynamic status of the subject; and

a therapy selector configured to generate a therapy signal representative of a proposed therapy for the subject based on a result of the comparison of the index with the at least one threshold as determined by the threshold comparator.

12. The implantable medical device according to claim 10, further comprising a posture sensor configured to generate a posture signal representative of a current posture of the subject, wherein the signal generator is configured to generate the electric signal during the status assessment period when the posture signal indicates that the subject is in a predefined target posture.

13. The implantable medical device according to claim 10, further comprising:

a posture sensor configured to generate a posture signal representative of a current posture of the subject; and

a model selector configured to select between a first linear parametric status model

14. A method of determining a hemodynamic status model, the method comprising:

generating, during a period of normal hemodynamic status of a subject and in connection with a period of abnormal hemodynamic status of the subject, electric signals applicable over two electrodes of at least one electric lead;

sensing, during the period of normal hemodynamic status of the subject and in connection with the period of abnormal hemodynamic status of the subject, resulting electric signals over two electrodes of the at least one electric lead;

determining a first impedance signal based on the electric signals applied and the resulting electric signals sensed during the period of normal hemodynamic status of the subject;

determining a second impedance signal based on the electric signals applied and the resulting electric signals sensed in connection with the period of abnormal hemodynamic status of the subject;

calculating first parameter values of a set of N different impedance-derivable parameters based on the first impedance signal;

calculating second parameter values of the set of N different impedance-derivable parameters based on the second impedance signal, N is a positive integer equal to or larger than two;

estimating, based on the first parameter values and the second parameter values, N+1 coefficients of a linear parametric status model

15. The method according to claim 14, further comprising detecting a tachyarrhythmia period of the subject based on electric signals sensed from a heart of the subject by at least one electric lead of the at least one electric lead, wherein

generating the electric signals in connection with the period of abnormal hemodynamic status comprises generating, in connection with the period of abnormal hemodynamic status of the subject and in response to the detected tachyarrhythmia period, the electric signals applicable over the two electrodes;

and

sensing the resulting electric signals in connection with the period of abnormal hemodynamic status comprises sensing, in connection with the period of abnormal hemodynamic status of the subject and in response to the detected tachyarrhythmia period, the resulting electric signals over the two electrodes.

16. The method according to claim 14, further comprising detecting a current posture of the subject, wherein generating the electric signals comprises generating, during the period of normal hemodynamic status of the subject and in connection with the period of abnormal hemodynamic status of the subject and when the subject is in a predefined target posture, electric signals applicable over the two electrodes.

17. The method according to claim 14, further comprising detecting a current posture of the subject, wherein

generating the electric signals comprises generating, during the period of normal hemodynamic status of the subject and when the current posture is a first predefined posture of the subject, during the period of normal hemodynamic status of the subject and when the current posture is a second predefined posture of the subject, in connection with the period of abnormal hemodynamic status of the subject and when the current posture is the first predefined posture of the subject, and in connection with the period of abnormal hemodynamic status of the subject and when the current posture is the second predefined posture of the subject, the electric signals applicable over the two electrodes;

sensing the resulting electric signals comprises sensing, during the period of normal hemodynamic status of the subject and when the current posture is the first predefined posture of the subject, during the period of normal hemodynamic status of the subject and when the current posture is the second predefined posture of the subject, in connection with the period of abnormal hemodynamic status of the subject and when the current posture is the first predefined posture of the subject, and in connection with the period of abnormal hemodynamic status of the subject and when the current posture is the second predefined posture of the subject, the resulting electric signals over the two electrodes;

determining the first impedance signal comprises determining the first impedance signal based on the electric signals applied and the resulting electric signals sensed during the period of normal hemodynamic status of subject and when the current posture is the first predefined posture of the subject;

determining the second impedance signal comprises determining the second impedance signal based on the electric signals applied and the resulting electric signals sensed in connection with the period of abnormal hemodynamic status of the subject and when the current posture is the first predefined posture of the subject, the method further comprises;

determining a third impedance signal based on the electric signals applied and the resulting electric signals sensed during the period of normal hemodynamic status of the subject and when current posture is the second predefined posture of the subject;

determining a fourth impedance signal based on the electric signals applied and the resulting electric signals sensed in connection with the period of abnormal hemodynamic status of the subject and when the current posture is the second predefined posture of the subject;

calculating third parameter values of the set of N different impedance-derivable parameters based on the third impedance signal; and

calculating fourth parameter values of the set of N different impedance-derivable parameters based on the fourth impedance signal, wherein estimating the N+1 coefficients comprises;

estimating, based on the first parameter values and the second parameter values, N+1 coefficients of a first linear parametric status model

18. The method according to claim 14, further comprising:

generating, during a status assessment period, electric signals applicable over two electrodes of the at least one electric lead;

sensing, during the status assessment period, resulting electric signals over two electrodes of the at least one electric lead;

determining an impedance signal based on the electric signals applied and the resulting electric signals sensed during the status assessment period;

calculating parameter values of the set of N different impedance-derivable parameters based on the impedance signal; and

calculating an index representative of a current hemodynamic status of the subject based on the N+1 coefficients and the calculated parameter values.

19. The method according to claim 18, further comprising:

comparing the calculated index with at least one threshold having a threshold value that is smaller than the predefined first value representative of normal hemodynamic status of the subject and is larger than the predefined second value representative of abnormal hemodynamic status of the subject; and

generating a therapy signal representative of a proposed therapy for the subject based on a result of the comparison of the index with the at least one threshold.

20. A method of assessing a hemodynamic status of a subject, the method comprising:

generating, during a status assessment period, electric signals applicable over two electrodes of at least one electric lead;

sensing, during the status assessment period, resulting electric signals over two electrodes of the at least one electric lead;

determining an impedance signal based on the electric signals applied and the resulting electric signals sensed during the status assessment period;

calculating parameter values of a set of N different impedance-derivable parameters based on the impedance signal; and

calculating an index representative of a current hemodynamic status of the subject based on the parameter values and N+1 coefficients of a linear parametric status model

21. The method according to claim 20, further comprising:

comparing the calculated index with at least one threshold having a threshold value that is smaller than a predefined first value representative of normal hemodynamic status of the subject and is larger than a predefined second value representative of abnormal hemodynamic status of the subject; and

generating a therapy signal representative of a proposed therapy for the subject based on a result of the comparison of the index with the at least one threshold.

22. The method according to claim 20, further comprising detecting a current posture of the subject, wherein generating the electric signals comprises generating, during the status assessment period and when the current posture is a predefined target posture, the electric signals applicable over the two electrodes.

23. The method according to claim 20, further comprising:

detecting a current posture of the subject; and

selecting between a first linear parametric status model