Sensing rate of change of pressure in the left ventricle with an implanted device

• US 7,670,298 B2
• Filed: 06/01/2005
• Issued: 03/02/2010
• Est. Priority Date: 06/01/2005
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Wariar, Ramesh, Carlson, Gerrard M., Siejko, Krzysztof Z., Brockway, Marina
• Primary Examiner(s): Layno; Carl H.
• Assistant Examiner(s): Morales; Jon-Eric C.
• Application Number:
  US11/142,851
• Publication Number:
  US 20060276849A1
• Time in Patent Office: 1,735 Days
• Field of Search: 600/528, 600/586, 600/513, 600/587, 600/508, 600/481, 600/483, 600/485, 600/486, 600/488
• US Class Current: 600/528
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 7/00 Instruments for auscultation
• CPC Class Codes: A61N 1/36564 controlled by blood pressure
• 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 1/375 Constructional arrangements, e.g. casings
• CPC Class Codes: A61N 1/37512 Pacemakers

Abstract

An implantable device and method for monitoring S1 heart sounds with a remotely located accelerometer. The device includes a transducer that converts heart sounds into an electrical signal. A control circuit is coupled to the transducer. The control circuit is configured to receive the electrical signal, identify an S1 heart sound, and to convert the S1 heart sound into electrical information. The control circuit also generates morphological data from the electrical information. The morphological data relates to a hemodynamic metric, such as left ventricular contractility. A housing may enclose the control circuit. The housing defines a volume coextensive with an outer surface of the housing. The transducer is in or on the volume defined by the housing.

Claims

1. An implantable device comprising:

a transducer that converts heart sounds into an electrical signal;

a control circuit coupled to the transducer, the control circuit configured to receive the electrical signal, identify an S1 heart sound, convert the S1 heart sound into morphological data comprising a maximum S1 amplitude and a minimum S1 amplitude, and determine and provide, to a user or automated process, a patient status indicator based on an indication of a peak-to-peak difference between the maximum S1 amplitude and the minimum S1 amplitude, wherein the patient status indicator is correlative to at least one of contractility or a maximum time rate of change of pressure within a ventricle of a heart during a cardiac cycle; and

a housing enclosing the control circuit, the housing defining a volume coextensive with an outer surface of the housing;

wherein the transducer is located in a region in or on the housing.

2. The device of claim 1, wherein the implantable device is configured to mate to a lead system that is configured to extend from the implantable device to a patient'"'"'s heart.

3. The device of claim 1, wherein the transducer comprises an accelerometer.

4. The device of claim 1, further comprising:

a therapy delivery circuit coupled to the control circuit, the therapy delivery circuit configured to deliver therapy to a heart in the form of electrical impulses.

5. The device of claim 4, wherein the control circuit is further configured to adjust the therapy delivered by the therapy deliver circuit based on the morphological data.

6. The device of claim 1, wherein the patient status indicator is based on an indication of a peak-to-peak difference between a central tendency, for a plurality of S1 heart sounds, of the maximum S1 amplitude and a central tendency of the minimum S1 amplitude.

7. The device of claim 1, wherein the patient status indicator is based on an indication of a central tendency of a peak-to-peak difference between the maximum S1 amplitude and the minimum S1 amplitude.

8. The device of claim 1, wherein the control circuit is configured to determine the peak-to-peak difference between the maximum S1 amplitude and the minimum S1 amplitude by:

identifying a time, t_m, associated with a beginning of the S1 heart sound, and a time, t_n, associated with an ending of the S1 heart sound;

identifying, over a span of time between t_m and t_n, a global maximum S1 amplitude and a global minimum S1 amplitude;

determining, for a plurality of S1 heart sounds, a central tendency of the global maximum S1 amplitudes and a central tendency of the global minimum S1 amplitudes; and

subtracting the central tendency of the global minimum S1 amplitudes from the central tendency of the global maximum S1 amplitudes to determine the peak-to-peak difference.

9. A method comprising:

using a transducer located outside of a heart to detect an S1 heart sound;

converting the S1 heart sound into an electrical signal using the transducer;

using the electrical signal to convert the S1 heart sound into morphological data comprising a maximum S1 amplitude and a minimum S1 amplitude; and

determining and providing, to a user or automated process, a patient status indicator based on an indication of a peak-to-peak difference between the maximum S1 amplitude and the minimum S1 amplitude, wherein the patient status indicator is correlative to at least one of contractility or a maximum time rate of change of pressure within a ventricle of a heart during a cardiac cycle.

10. The method of claim 9, further comprising:

storing the morphological data in a datastore, so that a trend regarding the morphological data may be obtained.

11. The method of claim 9, further comprising:

adjusting a therapy delivered to said heart on the basis of the morphological data.

12. The method of claim 11, wherein the therapy comprises cardiac resynchronization therapy.

13. The method of claim 9, further comprising:

adjusting a drug dosage on the basis of the morphological data.

14. The method of claim 9 further comprising:

transmitting the morphological data to an external unit for display.

15. The method of claim 9, comprising determining the peak-to-peak difference between the maximum S1 amplitude and the minimum S1 amplitude by:

identifying a time, t_m, associated with a beginning of the S1 heart sound, and a time, t_n, associated with an ending of the S1 heart sound;

identifying, over a span of time between t_m and t_n, a global maximum S1 amplitude and a global minimum S1 amplitude;

determining, for a plurality of S1 heart sounds, a central tendency of the global maximum S1 amplitudes and a central tendency of the global minimum S1 amplitudes; and

subtracting the central tendency of the global minimum S1 amplitudes from the central tendency of the global maximum S1 amplitudes to determine the peak-to-peak difference

16. A system comprising:

(a) an implantable device including

a transducer located in or on the implantable device, the transducer configured to convert heart sounds into an electrical signal;

a first control circuit coupled to the transducer, configured to receive the electrical signal; and

a first interface circuit for communicating with an external system; and

(b) the external system including

a second interface circuit for communicating with the implantable device; and

a second control circuit coupled to the second interface circuit, wherein at least one of the first and second control circuits is configured to identify an S1 heart sound, convert the S1 heart sound into morphological data comprising a maximum S1 amplitude and a minimum S1 amplitude, and determine and provide, to a user or automated process, a patient status indicator based on an indication of a peak-to-peak difference between the maximum S1 amplitude and the minimum S1 amplitude, wherein the patient status indicator is correlative to at least one of contractility or a maximum time rate of change of pressure within a ventricle of a heart during a cardiac cycle.

17. The system of claim 16, wherein the implantable device is configured to mate to a lead system configured to extend from the implantable device to a patient'"'"'s heart.

18. The system of claim 16, wherein the transducer comprises an accelerometer.

19. The system of claim 16, wherein the implantable device further comprises:

a therapy delivery circuit coupled to the control circuit, the therapy delivery circuit configured to deliver therapy to a heart in the form of electrical impulses.

20. The system of claim 19, wherein the control circuit is further configured to adjust the therapy delivered by the therapy deliver circuit based on the morphological data.

21. The system of claim 16, wherein the patient status indicator is based on an indication of a peak-to-peak difference between a central tendency, for a plurality of S1 heart sounds, of the maximum S1 amplitude and a central tendency of the minimum S1 amplitude.

22. The system of claim 16, wherein the patient status indicator is based on an indication of a central tendency of a peak-to-peak difference between the maximum S1 amplitude and the minimum S1 amplitude.

23. The system of claim 16, wherein the second control circuit is configured to determine the peak-to-peak difference between the maximum S1 amplitude and the minimum S1 amplitude by:

identifying a time, t_m, associated with a beginning of the S1 heart sound, and a time, t_n, associated with an ending of the S1 heart sound;

identifying, over a span of time between t_m and t_n, a global maximum S1 amplitude and a global minimum S1 amplitude;

determining, for a plurality of S1 heart sounds, a central tendency of the global maximum S1 amplitudes and a central tendency of the global minimum S1 amplitudes; and

subtracting the central tendency of the global minimum S1 amplitudes from the central tendency of the global maximum S1 amplitudes to determine the peak-to-peak difference.