System and method to monitor the heart of a patient

• US 5,743,267 A
• Filed: 10/27/1995
• Issued: 04/28/1998
• Est. Priority Date: 10/19/1995
• Status: Expired due to Term

• Current Assignee: Telecom Medical Incorporated
• Original Assignee: Telecom Medical Incorporated
• Inventors: Nikolic, Serjan D., Feierbach, Gary
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US08/549,375
• Time in Patent Office: 914 Days
• Field of Search: 128/672, 128/673, 128/675, 128/677, 128/680-683, 128/687, 128/691, 128/713, 128/740, 128/903
• US Class Current: 600/483
• CPC Class Codes: A61B 5/0028 Body tissue as transmission medium, i.e. transmission systems where the medium is the human body
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: Y10S 128/903 Radio telemetry

Abstract

A system and method for monitoring a physiological attribute of a patient is disclosed. The system includes a measuring device to measure an absolute physiological attribute of a patient and to generate an absolute physiological attribute signal. The present invention also includes a processing element to receive the measured absolute physiological attribute signal. The processing element then generates a filtered physiological attribute signal by substantially removing the effects of certain bodily functions from the absolute physiological attribute signal and other artifacts of measurement. The processor also generates a set of parameters derived from the filtered physiological attribute signal which are indicative of the health and condition of the patient.

Claims

1. A system used to monitor a patient'"'"'s heart, the system comprising:

a measuring device configured to measure the absolute blood pressure of the patient and to generate an absolute blood pressure signal; and

a processing element configured to be coupled to receive the absolute blood pressure signal, the processing element being further configured to generate a filtered blood pressure signal from the absolute blood pressure signal by substantially removing variations from the absolute blood pressure signal caused by the respiratory activity of the patient, the processing element further including;

a filtering element further including a sampling element configured to sample the absolute blood pressure signal during a plurality of selected heart cycles that occur over a course of a plurality of respiratory cycles of the patient, the plurality of selected heart cycles being selected at approximately the same phase during each of the plurality of respiratory cycles respectively;

an averaging element configured to generate the filtered blood pressure signal by averaging the absolute blood pressure signal measured during the plurality of selected heart cycles; and

a computation element configured to generate a set of parameters derived from the filtered blood pressure signal which are indicative of the condition of the patient.

2. The system of claim 1, further comprising:

a processing station, coupled to receive the set of parameters, and configured to process the set of parameters to monitor the patient; and

a communication element configured to communicate the set of parameters from the processing element to the processing station.

5. The system of claim 2, wherein the communication element and the processing station communicate through a transmission medium, the transmission medium selected from one of the following group of transmission mediums, including:

telephone lines, radio waves, light waves, acoustic sound waves, a computer network, or a wired interconnect coupled between the communication element and the processing station.

6. The system of claim 2, wherein the processing station is configured to be located at a position remote from the patient, and the processing station is further configured to process the set of parameters to aid personal in diagnosing the patient from the remote location.

7. The system of claim 2, wherein the processing station is further configured to maintain a record containing information related to the patient, the record containing a plurality of the sets of parameters generated at specific points of time respectively.

8. The system of claim 1, wherein the measuring device is a pressure transducer configured to be implanted into the heart of the patient.

9. The system of claim 1, wherein the selected phase is an end exhalation phase of each of the plurality of respiratory cycles.

10. The system of claim 1, wherein the selected phase is an end inhalation phase of each of the plurality of respiratory cycles.

11. The system of claim 1, wherein the set of parameters are selected from the following group of parameters:

(a) a peak systolic pressure measurement of the filtered blood pressure signal;

(b) a minimum diastolic pressure measurement of the filtered blood pressure signal;

(c) a mean diastolic pressure measurement of the filtered blood pressure signal;

(d) a time constant of isovolumic pressure decay indicative of the rate at which the heart of the patient relaxes;

(e) a contraction signal indicative of the ability of the heart of the patient to contract;

(e) a contraction signal derived by determining a change in blood pressure over time during an isovolumic contraction phase of the filtered blood pressure signal;

(f) a maximum pressure time derivative signal;

(g) a normalized maximum pressure time derivative signal;

(h) a time to the maximum pressure time derivative signal;

(i) a normalized time to the maximum pressure time derivative signal;

(j) a relaxation signal indicative of the ability of the heart of the patient to relax by calculating a change in pressure over time during an isovolumic relaxation phase of the filtered blood pressure signal;

(k) a minimum pressure time derivative;

(l) a time to the minimum pressure time derivative;

(m) the pressure of the filtered blood pressure signal at the time to the minimum pressure time derivative;

(n) a minimum of the second derivative;

(o) the blood pressure at a predetermined point in the down slope of the second derivative of the filtered blood signal;

(p) end diastolic pressure signal;

(q) a time to the end diastolic pressure signal;

(r) a time measurement of a diastolic period of the filtered blood pressure signal;

(s) a measure of an asymptote of isovolumic relaxation pressure exponential derived from the filtered blood pressure signal; and

(t) a signal indicative of the heart rate of the patient.

12. The system of claim 1, wherein the processing element is an implantable device designed to be implanted into the body of the patient and includes circuitry configured to process the absolute physiological attribute signal and to generate the set of parameters.

13. The system of claim 7, wherein the processing station further comprises a processing unit configured to process the plurality of sets of parameters and to generate a display indicative of changes in the physiological attribute of the patient over the specific points in time.

14. The system of claim 1, wherein the measuring device is configured to be embedded into the patient.

15. The system of claim 1, wherein the measuring device is configured to be located external to the body of the patient and measures the absolute blood pressure of the patient using a non-invasive technique.

16. The system of claim 1, wherein the processing element is configured to be located external to the body of the patient.

17. The system of claim 1, wherein the processing element is configured to be implanted into the body of the patient.

3. The system of clam 2, wherein the communication element includes a first communication device configured to be implanted into the body of the patient and coupled to the processing element, and a second communication device configured to be located external to the body of the patient.

4. The system of claim 3, wherein the first communication device and the second communication device communicate through a communication medium, the communication medium selected from one of the following group of communication mediums, including:

radio waves, light waves, acoustic sound waves, or a hard wired port coupled between the first communication device and the second communication device.

18. A method to monitor a patient'"'"'s heart, the method comprising the steps of:

measuring the absolute blood pressure of the patient;

generating an absolute blood pressure signal indicative of the absolute blood pressure of the patient;

generating a filtered blood pressure signal from the absolute blood pressure signal by substantially removing variations from the absolute blood pressure signal caused by the respiratory activity of the patient;

generating a set of parameters derived from the filtered blood pressure signal which are indicative of the condition of the patient'"'"'s heart;

transmitting the set of parameters to a processing station;

analyzing the set of parameters to monitor the condition of the patient'"'"'s heart;

the step of generating the filtered blood pressure signal further comprising the steps of;

sampling the absolute blood pressure signal during a plurality of selected heart cycles that occur over the course of a plurality of respiratory cycles of the patient, the selected heart cycles being selected at a approximately the same phase of each of the plurality of respiratory cycles;

generating a plurality of sampled blood pressure signals during the plurality of selected heart cycles;

averaging the plurality of sampled blood pressure signals; and

generating the filtered blood pressure signal from the averaged blood pressure signal.

19. The method of claim 18, wherein the selected phase is an end exhalation phase of each of the plurality of respiratory cycles.

20. The method of claim 18, wherein the selected phase is an end inhalation phase of each of the plurality of respiratory cycles.

21. The method of claim 18, wherein the transmitting step further includes the step of communicating the set of parameters from a first communication device located internal to the body of the patient to a second communication device located external to the patient of the body.

22. The method of claim 21, wherein the communication step includes the step of communicating between the first communication device and the second communication device through a communication medium, the communication medium selected from one of the following group of communication mediums, including:

radio waves, light waves, acoustic sound waves, or a wire interconnect coupled between the first communication device and the second communication device.

23. The method of claim 18, wherein the transmitting step further includes the step of communicating the set of parameters to the processing station through a communication medium, the communication medium selected from one of the following group of communication mediums, including:

telephone lines, radio waves, light waves, acoustic sound waves, a computer network, or a wire interconnect.

24. The system of claim 18, wherein the step of analyzing the set of parameters occurs at a position remote from the patient.

25. A method of monitoring the heart of a patient, comprising the steps of:

sampling the blood pressure of the patient over a first series of respiratory cycles of the patient during a first period in time;

generating a first absolute blood pressure signal over the first series of respiratory cycles;

generating a first filtered blood pressure signal by substantially removing variations in the first absolute blood pressure signal caused by respiratory activity of the patient during the first series of respiratory cycles;

the step of generating the first filtered blood pressure signal further comprising the steps of;

sampling the first absolute blood pressure signal during a first plurality of selected heart cycles that occur over the course of the first plurality of respiratory cycles, the selected first plurality of heart cycles being selected at approximately the same phase of each of the first plurality of respiratory cycles;

generating a first plurality of sampled blood pressure signals from the first plurality of selected heart cycles;

averaging the first plurality of sampled blood pressure signals;

generating the first filtered blood pressure signal from the averaged first plurality of sampled blood pressure signals;

generating a first set of parameters from the first filtered blood pressure signal, the first set of parameters indicative of the condition of the heart of the patient during the first period in time; and

analyzing the first set of parameters.

26. The method of claim 25, further comprising the steps of:

sampling the blood pressure of the patient over a second series of respiratory cycles of the patient during a second period of time;

generating a second absolute blood pressure signal over the second series of respiratory cycles;

generating a second filtered blood pressure signal by substantially removing variations in the second absolute blood pressure signal caused by the respiratory activity of the patient during the second series of respiratory cycles;

the step of generating the second filtered blood pressure signal further comprising the steps of;

sampling the second absolute blood pressure signal during a second plurality of selected heart cycles that occur over the course of the second plurality of respiratory cycles, the second plurality of selected heart cycles being selected at approximately the same phase of each of the second plurality of respiratory cycles;

generating a plurality of second sampled blood pressure signals from the second plurality of selected heart cycles;

averaging the second plurality of sampled blood pressure signals;

generating a second filtered blood pressure signal from the second averaged plurality of sampled blood pressure signals;

generating a second set of parameters from the second filtered blood pressure signal, the second set of parameters indicative of the condition of the heart of the patient during the second period in time; and

analyzing the second set of parameters.

27. The method of claim 26, further comprising the steps of

comparing the first set of parameters and the second set of parameters;

ascertaining the relative difference between the first set of parameters and the second set of parameters; and

monitoring the condition of the heart of the patient based on the relative difference between the first set of parameters and the second set of parameters.

28. The method of claim 27, further comprising the step of subscribing a medical treatment for the patient based on the monitoring step.

29. The method of claim 25, further comprising the step of communicating the first set of parameters to a location remote from the patient so that the heart condition of the patient can be monitored from the remote location.

30. The method of claim 25, wherein the step of generating the first set of parameters includes the step of generating at least one of the following group of parameters:

(a) a peak systolic pressure measurement of the filtered blood pressure signal;

(b) a minimum diastolic pressure measurement of the filtered blood pressure signal;

(c) a mean diastolic pressure measurement of the filtered blood pressure signal;

(d) a time constant of isovolumic pressure decay indicative of the rate at which the heart of the patient relaxes;

(e) a contraction signal indicative of the ability of the heart of the patient to contract;

(e) a contraction signal derived by determining a change in blood pressure over time during an isovolumic contraction phase of the filtered blood pressure signal;

(f) a maximum pressure time derivative signal;

(g) a normalized maximum pressure time derivative signal;

(h) a time to the maximum pressure time derivative signal;

(i) a normalized time to the maximum pressure time derivative signal;

(j) a relaxation signal indicative of the ability of the heart of the patient to relax by calculating a change in pressure over time during an isovolumic relaxation phase of the filtered blood pressure signal;

(k) a minimum pressure time derivative;

(l) a time to the minimum pressure time derivative;

(m) the pressure of the filtered blood pressure signal at the time to the minimum pressure time derivative;

(n) a minimum of the second derivative;

(o) the blood pressure at a predetermined point in the down slope of the second derivative of the filtered blood signal;

(p) end diastolic pressure signal;

(q) a time to the end diastolic pressure signal;

(r) a time measurement of a diastolic period of the filtered blood pressure signal;

(s) a measure of an asymptote of isovolumic relaxation pressure exponential derived from the filtered blood pressure signal; and

(t) a signal indicative of the heart rate of the patient.

31. The method of claim 25, wherein the step of sampling the blood pressure of the patient further includes the step of implanting a blood pressure sensor into the heart of the patient.

32. The method of claim 25, wherein the step of generating the first set of parameters comprises the step of providing the patient with a processing element configured to receive the first absolute blood pressure signal, configured to generate the first filtered blood pressure signal, and further configured to generate the first set of parameters.

33. The method of claim 25, further comprising the step of providing the patient with a communication element so that the patient can communicate the first set of parameters to a remote location where the analysis step takes place.