SYSTEM AND METHOD FOR SYSTOLIC INTERVAL ANALYSIS

• US 20080103399A1
• Filed: 10/26/2006
• Published: 05/01/2008
• Est. Priority Date: 10/26/2006
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Patangay, Abhilash, Carlson, Gerrard M., Siejko, Krzysztof Z., Moon, Loell Boyce
• Granted Patent: US 8,364,263 B2
• Time in Patent Office: Days
• US Class Current: 600/508
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/0265 using electromagnetic means, e.g. electromagnetic flowmeter
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/283 Invasive
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/4836 Diagnosis combined with treatment in closed-loop systems or methods A61B5/0036 takes precedence
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/7282 Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence
• CPC Class Codes: A61B 7/00 Instruments for auscultation
• CPC Class Codes: A61B 7/04 Electric stethoscopes microphones, acoustic transducers therefor H04R
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/36571 controlled by blood flow rate, e.g. blood velocity or cardiac output
• CPC Class Codes: A61N 1/36578 controlled by mechanical motion of the heart wall, e.g. measured by an accelerometer or microphone
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters

Abstract

A system and method provide for systolic interval analysis. In an example, an implantable device measures a cardiac impedance signal. A transformation of the cardiac impedance interval is generated. The device also measures a heart sound signal. A time interval between a point on the transformed signal of the cardiac impedance signal and a point on the heart sound signal is calculated.

Claims

1. A system comprising:

an implantable medical device comprising;

a timing circuit;

a cardiac impedance sensing circuit, coupled to the timing circuit, the cardiac impedance sensing circuit configured to detect a cardiac impedance signal;

an acoustic sensor, coupled to the timing circuit, the acoustic sensor configured to sense an acoustic signal; and

a heart sound detector circuit, coupled to the timing circuit, the heart sound detector circuit configured to detect a heart sound signal in the acoustic signal;

wherein the timing circuit is configured to calculate a time interval between a point on the heart sound signal and a point on the cardiac impedance signal.

2. The system of claim 1, further comprising:

a telemetry circuit, coupled to the timing circuit, the telemetry circuit configured to transmit one or more of heart sound data and cardiac impedance data to one or more of an external device and an external database.

3. The system of claim 1, comprising a transform circuit, coupled to the timing circuit, the transform circuit including one or more of a differentiator, a filter, a derivative circuit, and an integrator, the transform circuit configured to transform the cardiac impedance signal into a transformed signal;

wherein the timing circuit is further configured to calculate a time interval between a point on the heart sound signal and a point on the transformed signal.

4. The system of claim 3, wherein the timing circuit configuration to calculate a time interval between a point on the heart sound signal and a point on the transformed signal calculates a left ventricular ejection time;

and further wherein in the calculation of the left ventricular ejection time the timing circuit uses a point on the heart sound signal indicative of an S1 heart sound, and a point on the transformed signal indicative of an aortic valve closure within a cardiac cycle.

5. The system of claim 3, wherein the timing circuit configuration to calculate a time interval between a point on the heart sound signal and a point on the transformed signal uses a point on the heart sound signal indicative of an S4 heart sound, and a point on the transformed signal indicative of one or more of an aortic valve opening within a cardiac cycle and a maximum systolic blood flow within a cardiac cycle.

6. The system of claim 3, wherein the timing circuit is configured to calculate the time interval between:

a point on the heart sound signal indicative of an S2 heart sound; and

a point on the transformed signal indicative of one of a maximum systolic blood flow within a cardiac cycle, an aortic valve opening within a cardiac cycle, a pulmonary valve closure within a cardiac cycle, an aortic valve closure within a cardiac cycle, or a mitral valve opening within a cardiac cycle.

7. The system of claim 3, wherein the timing circuit is configured to calculate the time interval between:

a point on the heart sound signal indicative of an S1 heart sound; and

a point on the transformed signal indicative of one of an aortic valve opening within a cardiac cycle, a pulmonary valve closure within a cardiac cycle, or a mitral valve opening within a cardiac cycle.

8. The system of claim 3, wherein the timing circuit is configured to calculate the time interval between:

a point on the heart sound signal indicative of an S3 heart sound; and

a point on the transformed signal indicative of one of an aortic valve closure within a cardiac cycle, a pulmonary valve closure within a cardiac cycle, or a mitral valve opening within a cardiac cycle.

9. The system of claim 1, wherein the timing circuit is configured to calculate the time interval over multiple cardiac cycles, and to identify or characterize a decompensation as a function of one or more changes in the time interval over the multiple cardiac cycles.

10. The system of claim 3, further comprising:

an external device; and

wherein the implantable medical device further comprises;

a cardiac sensing circuit, coupled to the timing circuit, the cardiac sensing circuit configured to detect a cardiac signal;

an ensemble averaging circuit, coupled to the timing circuit, the ensemble averaging circuit configured to generate an ensemble average for one or more of the cardiac signal, the cardiac impedance signal, the heart sound signal, and the transformed signal; and

a telemetry circuit;

and wherein the external device comprises;

a telemetry circuit;

a memory circuit configured to store one or more of the ensemble averaged cardiac signal, the ensemble averaged cardiac impedance signal, the ensemble averaged heart sound signal, and the ensemble averaged transformed signal; and

a timing circuit configured to calculate a second time interval between one or more of (1) a point on the ensemble averaged cardiac signal and a point on the ensemble averaged heart sound signal, (2) a first point on the ensemble averaged heart sound signal and a second point on the ensemble averaged heart sound signal, (3) a point on the ensemble averaged impedance signal and a point on the ensemble averaged heart sound signal, and (4) a point on the ensemble averaged heart sound signal and a point on the ensemble averaged transformed signal.

11. The system of claim 10, wherein the point of the ensemble averaged cardiac signal comprises a portion of an R wave, and the point of the ensemble averaged heart sound signal is indicative of one of an S1, S2, S3, or S4 heart sound.

12. The system of claim 10, wherein the external device memory includes one or more of cardiac signal data, cardiac impedance data, heart sound data, and transformed signal data from a population of individuals, and further wherein the external device is configured to use the cardiac signal, cardiac impedance, heart sound, and transformed signal population data in connection with an analysis of an individual'"'"'s cardiac signal, cardiac impedance, heart sound, and transformed signal data.

13. The system of claim 10, wherein the external device includes or is coupled to one or more external sensors, and further wherein one or more patient thresholds are set as a function of data received from the one or more external sensors.

14. The system of claim 10, wherein the external device includes or is coupled to one or more of an external sensor and a database, and wherein the external device further comprises a circuit configured to compare one or more of the cardiac signal, the cardiac impedance signal, the heart sound signal, the transformed signal, data from the external sensor, and data from the database.

15. The system of claim 14, wherein the external sensor includes one or more of a body weight sensor and a blood pressure sensor, and further wherein the database comprises one or more of a medication history, a disease history, a hospitalization history, and one or more population statistics.

16. A process comprising:

measuring a cardiac impedance signal with an implantable medical device;

measuring a heart sound signal with the implantable medical device; and

calculating a time interval between a point on the cardiac impedance signal a point on the heart sound signal.

17. The process of claim 16, further comprising:

transforming the cardiac impedance signal into a transformed signal; and

calculating a time interval between a point on the transformed signal and a point on the heart sound signal;

wherein the transforming includes one or more of differentiation, a filtering, a derivation, and an integration.

18. The process of claim 17, wherein the calculation of the time interval between a point on the transformed signal and a point on the heart sound signal calculates a left ventricular ejection time;

and further wherein the calculation of the left ventricular ejection time uses a point on the heart sound signal indicative of an S1 heart sound, and a point on the transformed signal indicative of an aortic valve closure within a cardiac cycle.

19. The process of claim 17, wherein the calculation of a time interval between a point on the transformed signal and a point on the heart sound signal uses a point on the heart sound signal indicative of an S4 heart sound, and a point on the transformed signal indicative of one or more of an aortic valve opening within a cardiac cycle and a maximum systolic blood flow within a cardiac cycle.

20. The process of claim 17, wherein the calculation of the time interval uses:

a point on the heart sound signal indicative of an S2 heart sound; and

a point on the transformed signal indicative of one of a maximum systolic blood flow within a cardiac cycle, an aortic valve opening within a cardiac cycle, a pulmonary valve closure within a cardiac cycle, an aortic valve closure within a cardiac cycle, or a mitral valve opening within a cardiac cycle.

21. The process of claim 17, wherein the calculation of the time interval uses:

a point on the heart sound signal indicative of an S1 heart sound; and

a point on the transformed signal indicative of one of an aortic valve opening within a cardiac cycle, a pulmonary valve closure within a cardiac cycle, or a mitral valve opening within a cardiac cycle.

22. The process of claim 17, wherein the calculation of the time interval uses:

a point on the heart sound signal indicative of an S3 heart sound; and

a point on the transformed signal indicative of one of an aortic valve closure within a cardiac cycle, a pulmonary valve closure within a cardiac cycle, or a mitral valve opening within a cardiac cycle.

23. The process of claim 17, comprising calculating the time interval over multiple cardiac cycles, and identifying or characterizing a decompensation as a function of a change in the time interval over the multiple cardiac cycles.

24. A process comprising:

measuring a cardiac impedance signal with an implantable medical device;

measuring a cardiac electrical signal with the implantable medical device, the cardiac electrical signal including an R-wave;

measuring a heart sound signal with the implantable medical device, the heart sound signal including an S2 heart sound;

transforming the cardiac impedance signal into a transformed signal, the transformed signal including a portion indicative of an aortic opening;

estimating a pre-ejection time by calculating an interval between the R-wave on the cardiac electrical signal and the aortic opening on the transformed cardiac impedance signal; and

estimating a left ventricular ejection time by calculating an interval between the S2 heart sound on the heart sound signal and the aortic opening on the transformed cardiac impedance signal.

25. The process of claim 24, further comprising calculating a ratio of the pre-ejection time and the left ventricular ejection time;

and

wherein the transforming the cardiac impedance signal includes one or more of differentiation, a filtering, a derivation, and an integration.