Systems and methods of medical monitoring according to patient state

Abstract

A system for the detection of cardiac events occurring in a human patient is provided. At least two electrodes are included in the system for obtaining an electrical signal from a patient's heart. An electrical signal processor is electrically coupled to the electrodes for processing the electrical signal. The systems receives data regarding the patient's state (e.g. asleep, exercising). Patient state information is stored in a patient state array, thereby enabling the system to track the patient's state over time, and to select an appropriate test for detecting a cardiac event based on both past and present data regarding the patient's state.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention and its advantages, there is provided a detailed description and accompanying drawings of embodiments which are presently preferred. In illustrations of methods, when arrows indicate iteration (a return from later steps to prior steps), this iteration is understood to be a preferred embodiment, and executing the steps a single time may also be an option. In the illustration of methods, steps which occur sequentially may also occur concurrently, in parallel, or may be repeated several times (e.g., in order to obtain an estimation of a measure by computing a statistic such as the mean), prior to the next step occurring. In illustrations of systems, when lines contain arrow heads on both ends, this signifies that information may regularly travel in both directions. It is understood that the invention is not intended to be limited to the precise arrangements and instruments shown, wherein:

FIG. 1A illustrates a schematic representation of a preferred embodiment of the CardioTrend comprising an implantable system and an external system;

FIG. 1B illustrates a schematic representation of a preferred embodiment of the CardioTrend system and its modules;

FIG. 2 shows a preferred embodiment of the sensing module;

FIG. 3 shows a preferred embodiment of the diagnostic module;

FIG. 4 shows a preferred embodiment of the alarm module;

FIG. 5A shows a preferred embodiment of the storage module;

FIG. 5B shows a schematic representation of a method of operating the storage module;

FIG. 5C shows, on the top, an embodiment of a data module including divisions for alarm and storage data, and shows, on the bottom, a method for using such a data module;

FIG. 6 shows a preferred embodiment of the histogram module;

FIG. 7 shows a preferred embodiment of the intervention module;

FIG. 8 is a flow chart of a method for detecting ischemia based on ST segment deviations;

FIG. 9A shows a method by which a patient's state is used to adjust one or more of the cardiotrend operations by modifying the operation of the detection algorithm, or the operation of the modules of an alarm module, in order to adjust the detection of abnormal cardiac activity or the generation of alarms, respectively;

FIG. 9B shows several examples of patient state arrays applicable to the method shown in FIG. 9A;

FIG. 9C shows hypothetical data applicable to the method shown in FIG. 9A:

FIG. 10 illustrates an electrogram segment and associated heart signal features;

FIG. 11 shows exercise-induced ST deviation, as a function of heart-rate, computed from electrogram data from a patient before and after a therapeutic stent procedure;

FIG. 12 shows the steps associated with a segmentation based cardiac event detection scheme that utilizes patient state information to perform various operations; and,

FIGS. 13 a, 13b and 13c each show a table that contains information regarding the segmentation based cardiac event detection scheme outlined in FIG. 12.

Claims

1. A device for detecting a cardiac event, the device including: an sensor adapted to sense the cardiac signal from the patient's heart,a memory;a digital processor configured to: (i) compute a plurality of patient state values and store the plurality of patient state values in the memory, wherein at least two of the plurality of patient state values are different from one another; (ii) compute a plurality of a heart signal feature values from the cardiac signal, (iii) store each of the plurality of heart signal feature values so that it is associated with a corresponding patient state value; (iv) apply a test for detecting the cardiac event, wherein the test is based on both the plurality of patient state values and the plurality of heart signal feature values.

2. The device of claim 1 wherein the processor is further configured to compute an additional heart signal feature value from the cardiac signal, and to apply the test to the additional heart signal feature value.

3. The device of claim 2 wherein the test is a threshold test characterized by a threshold that is a function of both the plurality of patient state values and the plurality of heart signal feature values.

4. The device of claim 3 wherein each of the plurality of patient state values corresponds to an activity level, and wherein the processor is further configured to: (i) determine a plurality of thresholds associated with a corresponding plurality of activity levels, (ii) determine a particular activity level associated with the additional heart signal feature value, and (iii) select the threshold associated with the particular activity level, thereby selecting the test for detecting the cardiac event.

5. The device of claim 3 wherein each of the plurality of patient state values corresponds to an activity level, and one of the plurality of patient state values corresponds to a resting state and another of the plurality of patient state values corresponds to an exercising state.

6. The device of claim 1 wherein the sensor is an electrode.

7. The device of claim 6 wherein the sensor adapted for implantation into a human body.

8. A device for detecting a cardiac event, the device including: an sensor adapted to sense the cardiac signal from the patient's heart,a memory;a digital processor configured to: (i) compute a plurality of patient state values and store the plurality of patient state values in the memory; (ii) compute a plurality of a heart signal feature values from the electrical signal, (iii) store each of the plurality of heart signal feature values so that it is associated with a corresponding patient state value; (iv) select a response to the occurrence of the cardiac event, wherein the response is based on both the plurality of patient state values and the plurality of heart signal feature values.

9. The device of claim 8 wherein the response comprises initiating a patient alert.

10. The device of claim 8 wherein the response comprises initiating a therapeutic intervention.

11. The device of claim 8 wherein the electrode is adapted for implantation into a human body.

12. A device for detecting a cardiac event, the device including: a sensor adapted to sense the cardiac signal from the patient's heart,a memory;a digital processor configured to: (i) compute a plurality of patient state values from data other than cardiac electrical data and store the plurality of patient state values in the memory; (ii) compute a plurality of a heart signal feature values from the electrical signal, (iii) store each of the plurality of heart signal feature values so that it is associated with a corresponding patient state value;(iv) apply a test for detecting the cardiac event, wherein the test is based on both the plurality of patient state values and the plurality of heart signal feature values.

13. The device of claim 12 wherein the patient state values pertain to the patient's activity level.

14. The device of claim 13 wherein the test depends on activity level, and the test corresponding to a prior activity level is applied if the prior activity level occurred within a predetermined amount of time before the at least one heart beat occurred.

15. The device of claim 14 wherein the test is a thresholding test with a low threshold corresponding to a low activity level, and a high threshold corresponding to a high activity level, and wherein the high threshold is applied when the patient's current activity level is low if the patient's activity level was high within the predetermined amount of time.

16. The device of claim 12 further comprising an accelerometer, and wherein the patient state values are derived from the accelerometer.

17. The device of claim 12 further comprising a patient input device, and wherein the patient state values are derived from the patient input device.

18. A device for detecting a cardiac event, the device including: a sensor adapted to sense the a cardiac signal from the patient's heart,a memory for storing information regarding the patient's state;a digital processor configured to compute the value of a heart signal feature from the cardiac signal, wherein the heart signal feature corresponds to at least one heart beat, the digital processor further configured to select and apply a threshold function test for detecting the cardiac event, wherein the threshold function is based on the value of the heart signal feature and the stored information regarding the patient's state, and wherein the threshold function changes over time and in relation to prior patient activity levels.

19. The device of claim 18 wherein the threshold function is a recovery function.

20. The device of claim 18 wherein the threshold function additionally changes according to the patient's current activity level.

21. The device of claim 19 wherein the threshold function is an induction function.

22. The device of claim 18 wherein the threshold function is a self norm.

23. The device of claim 18 wherein the threshold function is a population norm.

24. The device of claim 18 wherein the threshold function is computed upon normal heart activity.

25. The device of claim 18 wherein the threshold function is computed upon ischemic heart activity.

26. The device of claim 18 wherein the threshold function is computed upon abnormal heart activity.

27. The device of claim 18 wherein the threshold function is computed as values which are statistically unlikely at a selected probability level.

28. A device for detecting a cardiac event, the device including: a sensor adapted to sense a signal from the patient's heart,a memory for storing information regarding the patient's state over time in a patient state array;a digital processor configured to compute the value of a heart signal feature from the sensed signal, wherein the heart signal feature corresponds to at least one heart beat, the digital processor further configured to select and apply a test for detecting the cardiac event, wherein the test is based on a patient state index that is a function of the information in the patient state array, such that the patient state index depends on a history of at least two patient state values.

29. The method of claim 28 wherein the patient state value is determined according to a window algorithm.

30. The method of claim 29 in which the window algorithm includes a “hold duration” algorithm.

31. A device for detecting a cardiac event, the device including: a sensor adapted to sense a signal reflective of cardiac activity;a state module configured to derive a patient state value;a memory for storing information regarding the patient's state over time in a patient state array of patient state values;a digital processor configured to compute the value of a heart signal feature from the sensed signal, wherein the heart signal feature corresponds to at least one heart beat;the digital processor further configured to select and apply a test for determining a cardiac status value;the digital processor further configured to operate to provide therapy in relation to at least one selected cardiac status value;wherein at least one of the operations of computing a heart signal feature, selecting a test, or providing therapy is adjusted based on a patient state index that is a function of the information in the patient state array, such that the patient state index depends on a history of at least one patient state values.

32. The device of claim 31 wherein therapy is the provision of an alert signal.

33. The device of claim 31 wherein therapy is the stimulation of the patient's heart.

34. The device of claim 31 wherein the digital processor is also adjusted to operate based upon a historical record of sensed activity.

35. The device of claim 31 wherein the digital processor is also adjusted to operate based upon a historical record of operation.

36. The device of claim 31 wherein the digital processor is also adjusted to operate based upon a historical record of heart rate.

37. The device of claim 31 wherein the patient state array contains values related to classification of a patient's state.

38. The device of claim 31 wherein the patient state array contains values related to quantification of a patient's state.

39. The device of claim 31 wherein the patient state value is obtained by a user's button press.

40. The device of claim 31 wherein the patient state value is obtained by evaluation of sensed data.

41. The device of claim 31 wherein the patient state value is set according to the values of a therapy protocol implemented by the system.

42. The device of claim 31 wherein the digital processor is adjusted to operate based on the patient state index so that alerting operations are modified based upon the patient state array values.

43. The device of claim 31 wherein the patient state index is determined according to a patient state algorithm that is applied to the patient state array.

44. The device of claim 31 wherein the patient state index is computed using a window algorithm that is applied to a selected span of values of the patient state array.

45. The device of claim 31 wherein the patient state index is computed using a window algorithm that is applied to a selected span of values of the patient state array, and wherein the occurrence of identical consecutive patient state values produces a different result than occurs when consecutive patient state values are not identical, for the same number of patient state values in the array.

46. The device of claim 44 in which the window algorithm includes a “hold duration” algorithm, which ignores current patient state values in favor of prior values for a specified interval.

47. The device of claim 31 wherein the digital processor is adjusted to operate based on a patient state index so that evaluation of sensed data operations are modified based upon a patient state index.

48. The device of claim 31 wherein the digital processor is adjusted to operate based on a patient state index so that sensed data are compared to reference data of a similar state.

49. The device of claim 31 wherein the digital processor is adjusted to operate based on a patient state index so that sensed data are stored as reference data of a particular patient state.

50. The device of claim 31 wherein the digital processor is adjusted to operate based on a patient state index so that features of sensed data are compared to a threshold function which changes over time and in relation to values of a patient state array, and wherein if said features exceed said threshold function then an alarm is triggered.

51. The device of claim 31 wherein the digital processor is adjusted to operate based on a patient state index so that alerting operations occur in relation to a particular patient state.

52. The device of claim 31 wherein the digital processor is adjusted to operate based on a patient state index so that stimulation operations occur in relation to a particular patient state.

53. The device of claim 31 wherein the digital processor is adjusted to operate based on a patient state index wherein the operations are adjusted in relation to a particular patient state.

54. The device of claim 31 wherein the digital processor is adjusted to operate based on a patient state index wherein a control law is adjusted in relation to a particular patient state.

55. The device of claim 31 wherein the digital processor is adjusted to operate based on a patient state index wherein the operations are limited in relation to a particular patient state.

56. The device of claim 31 wherein the digital processor is adjusted to operate based on a patient state index so that sensed data are analyzed according to an evaluation protocol that was designed to be used during a particular patient state.

57. The device of claim 46 wherein evaluation of sensed data operations are modified based upon a patient state index so that current data is evaluated using at least one criterion that is selected for a recent prior heart rate that is different than the current heart rate.

58. The device of claim 57 wherein the sensed data operations are related to evaluation of ST deviations and the at least one criterion is a threshold value above which the presence of ischemia is detected by the system.

59. A device for detecting a cardiac event, the device including: a sensor adapted to sense the electrical signal from the patient's heart,a memory;a digital processor configured to: (i) compute a plurality of types of patient state values and store the plurality of types of patient state values in the memory, wherein at least two of the plurality of patient state values are different from one another; (ii) compute a plurality of a heart signal feature values from the electrical signal, (iii) store each of the plurality of heart signal feature values so that it is associated with a corresponding patient state value; (iv) apply a test for detecting the cardiac event, wherein the test is based on both the plurality of patient state values and the plurality of heart signal feature values.