METHOD AND DEVICE TO MONITOR PATIENTS WITH KIDNEY DISEASE

• US 20120277546A1
• Filed: 04/19/2012
• Published: 11/01/2012
• Est. Priority Date: 04/29/2011
• Status: Active Grant

• Current Assignee: Mozarc Medical US LLC
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Soykan, Orhan, Manda, VenKatesh R., Gerber, Martin T., Hobot, Christopher M.
• Granted Patent: US 9,456,755 B2
• Time in Patent Office: Days
• US Class Current: 600/301
• CPC Class Codes: A61B 2505/07 Home care
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/145 Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissuemeasuring of blood pressure or blood flow A61B5/02; non-radiation detecting or locating of foreign bodies in blood A61B5/06
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61M 1/14 Dialysis systems; Artificial kidneys; Blood oxygenators semi-permeable membranes characterised by the material, manufacturing processes therefor B01D71/00 ; Reciprocating systems for treatment of body fluids, e.g. single needle systems for hemofiltration or pheresis
• CPC Class Codes: A61M 1/1601 Control or regulation
• CPC Class Codes: A61M 2205/18 with alarm
• CPC Class Codes: A61M 2205/3553 remote, e.g. between patient's home and doctor's office
• CPC Class Codes: A61M 2205/3584 using modem, internet or bluetooth
• CPC Class Codes: A61M 2205/52 with memories providing a history of measured variating parameters of apparatus or patient
• CPC Class Codes: A61M 2230/005 Parameter used as control input for the apparatus
• CPC Class Codes: A61M 2230/06 Heartbeat rate only
• CPC Class Codes: A61M 2230/20 Blood composition characteristics
• CPC Class Codes: A61M 2230/208 pH-value
• CPC Class Codes: A61M 2230/30 Blood pressure A61M2230/04 takes precedence
• CPC Class Codes: A61M 2230/63 Motion, e.g. physical activity

Abstract

A medical monitoring device for monitoring electrical signals from the body of a subject is described. The medical monitoring device monitors electrical signals originating from a cardiac cycle of the subject and associates each cardiac cycle with a time index. The medical monitoring device applies a forward computational procedure to generate a risk score indicative of hyperkalemia, hypokalemia or arrhythmia of the subject. The medical monitoring device can adjust the forward computational procedure based upon clinical data obtained from the subject.

Claims

1. A medical monitor, comprising:

a medical device for determining body potassium status by monitoring electrical signals of the body of a subject;

a processor for applying a forward computational procedure to the electrical signals monitored from the body in communication with the medical device; and

a communication system indicating a condition of hyperkalemia, hypokalemia or arrhythmia of the subject;

wherein the medical device associates a cardiac cycle of the subject with a time index and calculates at least one risk score associated with the time index.

2. The medical monitor of claim 1, wherein the processor is configured to receive clinical information regarding the physiological state of the subject associated with the time index and makes an adjustment to the forward computational procedure based upon an error between the at least one risk score and the clinical information.

3. The medical monitor of claim 1, wherein the medical device is implantable in the subject.

4. The medical monitor of claim 1, wherein the medical device is an external device comprising a plurality of electrodes for placement on the skin of the subject.

5. The medical monitor of claim 1, wherein the processor identifies a plurality of features of the cardiac cycle and compares the plurality of features to determinant values to calculate the at least one risk score using the forward computational procedure.

6. The medical monitor of claim 5, wherein the plurality of features includes one or more selected from the group consisting of P-R interval, QRS width, Q-T interval, QT-dispersion, P-wave amplitude, P-wave peak, S-T segment depression, T-wave inversion, U-wave amplitude, T-wave peak amplitude, and heart rate variability.

7. The medical monitor of claim 5, wherein a first risk score is calculated for a time index by applying a first forward computational procedure to one or more of the features of P-R interval, S-T segment depression, T-wave inversion and U-wave amplitude, wherein the processor increases a first alert counter by an incremental amount for each time index where the first risk score exceeds a predetermined threshold and an alert is issued when the first alert counter exceeds the predetermined threshold.

8. The medical monitor of claim 5, wherein a first risk score is calculated for a time index by applying a first forward computational procedure to one or more of the features of P-R interval, S-T segment depression, T-wave inversion and U-wave amplitude, wherein the processor increases an alert when the area under the curve of the risk score exceeds the predetermined threshold.

9. The medical monitor of claim 7, wherein the predetermined threshold is determined based upon a baseline risk score value of the subject.

10. The medical monitor of claim 7, wherein the first alert counter is increased for each consecutive time index where the first risk score exceeds the predetermined threshold.

11. The medical monitor of claim 10, wherein the predetermined threshold is determined based upon a baseline risk score value of the subject.

12. The medical monitor of claim 7, wherein the first alert counter is periodically reset if a sufficient number of time indices where the first risk score exceeding the predetermined threshold are not observed over a time period.

13. The medical monitor of claim 12, wherein the predetermined threshold is determined based upon a baseline risk score value of the subject.

14. The medical monitor of claim 5, wherein the plurality of features includes one or more selected from the group consisting of QRS width, Q-T interval, P-wave amplitude, P-wave peak, T-wave amplitude and heart rate variation, and wherein a second score is calculated for a time index by applying a second forward computational procedure to the features of QRS width, Q-T interval, P-wave amplitude, P-wave peak, T-wave amplitude, and heart rate variation.

15. The medical monitor of claim 7, wherein the first forward computational procedure determines a non-weighted or weighted sum of the feature scores P1, P6, P7, P8 and P10 to calculate the first risk score and the feature scores are assigned a zero or non-zero value based on the following:

P1 based upon the feature P-R interval in time units,

P6 based upon the feature of depression of the S-T segment,

P7 based upon the feature of inversion of the T-wave,

P8 based upon the feature of U-wave amplitude in potential units, and

P10 is heart rate variation in time units.

16. The medical monitor of claim 14, wherein the second forward computational procedure determines a non-weighted or weighted sum of the feature scores P2, P3, P4, P5, P9 and P10 and feature scores are assigned a zero or non-zero value based on the following:

P2 based upon the feature QRS width in time units,

P3 based upon the feature Q-T interval in time units,

P4 based upon the feature P-wave amplitude in potential units per time unit,

P5 based upon the feature P-wave peak in potential units,

P9 based upon the feature of T-wave amplitude in potential units and,

P10 is heart rate variation in time units.

17. The medical monitor of claim 5, wherein a third risk score is calculated for a time index by applying a third forward computational procedure to one or more of the features of P-R interval, QRS width, Q-T interval, P-wave amplitude, P-wave peak, S-T segment, T-wave inversion, U-wave amplitude, T-wave peak amplitude, and heart rate variability.

18. The medical monitor of claim 17, wherein the third forward computational procedure determines a non-weighted or weighted sum of the feature scores P1 through P10 and feature scores are assigned a zero or non-zero value based on the following:

P1 based upon the feature P-R interval in time units,

P2 based upon the feature QRS width in time units,

P3 based upon the feature Q-T interval in time units,

P4 based upon the feature P-wave amplitude in potential units per time unit,

P5 based upon the feature P-wave peak in potential units,

P6 based upon the feature of depression of the S-T segment,

P7 based upon the feature of inversion of the T-wave,

P8 based upon the feature of U-wave amplitude in potential units,

P9 based upon the feature of T-wave amplitude in potential units, and

P10 is heart rate variation in time units.

19. The medical monitor of claim 1, wherein the at least one risk score is calculated by the forward computational procedure by the addition of the plurality of features converted to scalar feature scores on a common scale, wherein the addition of the feature scores can be weighted or non-weighted as provided in Equation 4:

Risk Score=Σ

_k=1ⁿW_k*P_k, 

 

(Eq.

     4)

wherein W_k is a weighting factor and P_k is a feature score.

20. The medical monitor of claim 19, wherein the feature value P_k has a value of 0 or 1 or another integer value as determined by applying a discrete function to the corresponding feature of the cardiac function.

21. The medical monitor of claim 19, wherein the feature value P_k can have a non-integer value.

22. The medical monitor of claim 19, wherein the processor is configured to receive clinical information regarding the physiological state of the subject associated with the time index and makes an adjustment to the forward computational procedure based upon an error between the at least one risk score and the clinical information, and wherein the adjustment to the forward computational procedure based upon an error between the at least one risk score and the clinical information is done by the processor using a backward computational procedure, the backward computational procedure adjusts weighting factors W_k.

23. The medical monitor of claim 21, wherein the processor is configured to receive clinical information regarding the physiological state of the subject associated with the time index and makes an adjustment to the forward computational procedure based upon an error between the at least one risk score and the clinical information, and wherein the adjustment to the forward computational procedure based upon an error between the at least one risk score and the clinical information is done by the processor using a backward computational procedure, the backward computational procedure adjusts exponential factors used to calculate the scalar feature score.

24. The medical monitor of claim 19, wherein the processor is configured to receive clinical information regarding the physiological, state of the subject associated with the time index and makes an adjustment to the forward computational procedure based upon an error between the at least one risk score and the clinical information, and wherein the adjustment to the forward computational procedure based upon an error between the at least one risk score and the clinical information is done by the processor using a backward computational procedure, the backward computational procedure makes adjusts determinant values to calculate the risk score and feature scores P_k.

25. The medical monitor of claim 19, wherein the feature score P_k is determined by any one of the following computational procedures where X is a feature extracted from the electrical signals, X_c is a determinant value, and k is an exponential factor:

26. The medical monitor of claim 18, wherein the processor is configured to receive clinical information regarding the physiological state of the subject associated with the time index and makes an adjustment to the forward computational procedure based upon an error between the at least one risk score and the clinical information, and wherein the adjustment to the forward computational procedure based upon an error between the at least one risk score and the clinical information is done by the processor using a backward computational procedure, the backward computational procedure adjusts one or more selected from the determinant values X_C, the weighting factors W_k and the exponential factor k.

28. The method of claim 20, wherein the threshold is determined based upon a baseline risk score value of the subject.

29. The method of claim 20, wherein one or more of a first risk score and a second risk score is calculated by one of the following:

the first risk score calculated by comparing one or more features selected from P-R interval, QRS width, Q-T interval, QT-dispersion, P-wave amplitude, P-wave peak, S-T segment depression, T-wave inversion, U-wave amplitude, T-wave peak amplitude, and heart rate variability to corresponding value criteria, and

the second risk score calculated by comparing one or more features selected from QRS width, Q-T interval, P-wave amplitude, P-wave peak and T-wave amplitude to corresponding value criteria.

30. The method of claim 22, wherein at least one of the first risk score and the second risk score is calculated based upon assigning values to one or more selected from feature scores P1, P2, P3, P4, P5, P6, P7, P8, P9 and P10, wherein the set values are assigned as follows:

P1 based upon a comparison with the feature P-R interval in time units,

P2 based upon a comparison with the feature QRS width in time units,

P3 based upon a comparison with the feature Q-T interval in time units,

P4 based upon a comparison with the feature P-wave amplitude in potential units per time unit,

P5 based upon a comparison with the feature P-wave peak in potential units,

P6 based upon a comparison with the feature of depression of the S-T segment,

P7 based upon a comparison with the feature of inversion of the T-wave,

P8 based upon a comparison with the feature of U-wave amplitude in potential units,

P9 based upon a comparison with the feature of T-wave amplitude in potential units, and

P10 based upon a comparison with the feature of heart rate variation in time units.

31. The method of claim 23, wherein the set values are assigned a non-zero value based on the following:

P1 assigned a non-zero value if P-R interval is greater than 200 msec,

P2 assigned a non-zero value if QRS width is greater than 130 msec,

P3 assigned a non-zero value if Q-T interval is greater than 200 msec,

P4 assigned a non-zero value if P-wave amplitude is less than 1 mV,

P5 assigned a non-zero value if P-wave peak is greater than 1 mV/msec,

P6 assigned a non-zero value if S-T segment is depressed,

P7 assigned a non-zero value if T-wave is inverted,

P8 assigned a non-zero value if U-wave amplitude is greater than 2 mV,

P9 assigned a non-zero value if T-wave amplitude is greater than 3 mV, and

P10 assigned a non-zero value if heart rate variation is less than 50 msec.

32. The method of claim 23, wherein the first risk score is determined by a non-weighted or weighted sum of P1, P6, P7, P8 and P10.

33. The method of claim 23, wherein the second risk score is determined by a non-weighted or weighted sum of P2, P3, P4, P5, P9 and P10.

34. The method of claim 24, wherein the first risk score is determined by a non-weighted or weighted sum of P1, P6, P7, P8 and P10.

35. The method of claim 24, wherein the second risk score is determined by a non-weighted or weighted sum of P2, P3, P4, P5 and P9.

36. The method of claim 20, further comprising incrementally increasing a risk counter for each consecutive time index that a risk score of the at least one risk score exceeds the threshold value.

37. The method of claim 20, further comprising incrementally increasing a risk counter for each time index within a defined time period that a risk score of the at least one risk score exceeds the threshold value.

38. The method of claim 29, wherein the threshold is determined based upon a baseline risk score value of the subject.

39. The method of claim 30, wherein the threshold is determined based upon a baseline risk score value of the subject.

40. The method of claim 20, wherein the medical device is implantable in the subject.

41. The method of claim 20, wherein the medical device is an external device comprising a plurality of electrodes for placement on the skin of the subject.

42. The method of claim 20, further comprising making a modification to a dialysis treatment received by the subject based upon the result of the forward computational procedure.

43. The method of claim 35, wherein the dialysis treatment is modified to occur at a more frequent basis compared to a prior dialysis treatment if blood serum potassium concentration of the patient is determined to be high by the forward computational procedure.

44. The method of claim 35, wherein the dialysis treatment is modified to use a dialysate with a non-constant concentration of a potassium over the course of the dialysis treatment if blood serum potassium concentration of the patient is determined to be high by the forward computational procedure.

45. The method of claim 35, wherein the dialysis treatment is modified to a longer period of time compared to a prior dialysis treatment if blood serum potassium concentration of the patient is determined to be high by the forward computational procedure.

46. The method of claim 35, wherein the dialysis treatment is modified to use a dialysate having a higher concentration of a potassium salt compared to a prior dialysis treatment if blood serum potassium concentration of the patient is determined to be low by the forward computational procedure.

47. The method of claim 35, wherein the dialysis treatment is modified to a shorter period of time compared to a prior dialysis treatment if blood serum potassium concentration of the patient is determined to be low by the forward computational procedure.

27. A method for determining hyperkalemia, hypokalemia or arrhythmia, comprising:

observing a cardiac cycles of a subject by means of a medical device;

calculating at least one risk score based upon a plurality of features of the cardiac cycle, the cycle associated with a time index and a risk score, wherein the risk score is calculated using a forward computational procedure; and

sending an alert when at least one risk score exceeds a threshold for a defined time period, for a number of time indices, or for a certain fraction or number of time indices within a defined time period.