Trending of systolic murmur intensity for monitoring cardiac disease with implantable device

• US 7,963,926 B2
• Filed: 07/28/2008
• Issued: 06/21/2011
• Est. Priority Date: 05/05/2005
• Status: Expired due to Fees

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Siejko, Krzysztof Z., Fogoros, Richard
• Primary Examiner(s): Layno; Carl H
• Assistant Examiner(s): Gedeon; Brian T
• Application Number:
  US12/220,710
• Publication Number:
  US 20080294212A1
• Time in Patent Office: 1,058 Days
• Field of Search: 607/6, 607/17, 600/513, 600/514, 600/521, 600/528
• US Class Current: 600/528
• CPC Class Codes: A61B 7/023 for introduction into the body, e.g. into the oesophagus oesophageal ECG probes A61B5/285
• CPC Class Codes: A61N 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy
• CPC Class Codes: A61N 1/36514 controlled by a physiological quantity other than heart potential, e.g. blood pressure controlled by two or more physical parameters A61N1/36585

Abstract

Described is an implantable device configured to monitor for changes in the intensity and/or duration of a systolic murmur such as mitral regurgitation by means of an acoustic sensor. Such changes may be taken to indicate a change in a patient'"'"'s heart failure status. Upon detection of a worsening in the patient'"'"'s heart failure statue, the device may be programmed to alert clinical personnel over a patient management network and/or make appropriate adjustments to pacing therapy.

Claims

1. An implantable cardiac device, comprising:

a pressure sensor adapted for disposition so as to sense the acoustic vibrations produced by a systolic murmur and produce a pressure signal reflective thereof;

circuitry for measuring the intensity of the systolic murmur from the pressure signal produced by the pressure sensor;

an impedance sensor configured to measure transthoracic impedance reflective of cardiac volume;

a controller programmed to record a baseline murmur intensity; and

,

wherein the controller is further programmed to measure a current murmur intensity as an average of intensity measurements taken over some period of time, compare the current murmur intensity to the baseline murmur intensity, and detect a change indicative of worsening cardiac status if the current murmur intensity exceeds the baseline murmur intensity by a first specified threshold amount and if the transthoracic impedance measurement indicates an increase in cardiac volume above a second specified threshold amount.

2. The device of claim 1 wherein the controller is programmed to measure a current duration of the murmur during the systolic phase, compare the current murmur duration to a baseline murmur duration, and set an alarm flag if the current murmur duration exceeds the baseline murmur duration by the first specified threshold amount.

3. The device of claim 1 further comprising a signal energy detector and an R-wave detector for enabling the signal energy detector to measure the intensity of the murmur during the systolic phase of the cardiac cycle.

4. The device of claim 1 further comprising a telemetry transceiver and wherein the controller is programmed to transmit an alarm message over a patient management network via telemetry if the current murmur intensity exceeds the baseline murmur intensity by the first specified threshold amount.

5. The device of claim 1 wherein the controller is further programmed to store the current murmur intensity measurements take over a specified period time and compute a trend in the murmur'"'"'s intensity.

6. The device of claim 5 wherein the trend is computed by computing differences between consecutive current murmur intensity measurements over the specified period of time and summing the differences.

7. The device of claim 1 further comprising:

a bandpass filter for filtering the pressure signal; and

,

a signal energy detector for measuring a parameter related to the signal energy of the filtered pressure signal to represent the murmur intensity.

8. The device of claim 1 further comprising circuitry for pacing the heart in a programmed mode and wherein the controller is programmed to adjust the programmed mode if the current murmur intensity exceeds the baseline murmur intensity by a specified threshold amount.

9. The device of claim 8 wherein the device is configured to pace the heart in an atrial triggered mode and wherein the controller is programmed to adjust a programmed AV delay if the current murmur intensity exceeds the baseline murmur intensity by a specified threshold amount.

10. The device of claim 8 wherein the device is configured to pace the heart in a biventricular pacing mode and wherein the controller is programmed to adjust a biventricular offset if the current murmur intensity exceeds the baseline murmur intensity by the first specified threshold amount.

11. A method, comprising:

producing a pressure signal reflective of the acoustic vibrations produced by a systolic murmur;

filtering the pressure signal;

measuring a parameter related to the signal energy of the filtered pressure signal to represent the murmur intensity;

recording a baseline murmur intensity;

measuring transthoracic impedance reflective of cardiac volume; and

,

measuring a current murmur intensity as an average of intensity measurements taken over some period of time, comparing the current murmur intensity to the baseline murmur intensity, and detecting a change indicative of worsening cardiac status if the current murmur intensity exceeds the baseline murmur intensity by a first specified threshold amount and if the transthoracic impedance measurement indicates an increase in cardiac volume above a second specified threshold amount.

12. The method of claim 11 further comprising measuring a current duration of the murmur during the systolic phase, comparing the current murmur duration to a baseline murmur duration, and setting an alarm flag if the current murmur duration exceeds the baseline murmur duration by the first specified threshold amount.

13. The method of claim 11 further comprising detecting R-waves in order to measure the intensity of the murmur during the systolic phase of the cardiac cycle.

14. The method of claim 11 further comprising transmitting an alarm message over a patient management network via telemetry if the current murmur intensity exceeds the baseline murmur intensity by the first specified threshold amount.

15. The method of claim 11 further comprising storing the current murmur intensity measurements take over a specified period time and computing a trend in the murmur'"'"'s intensity.

16. The method of claim 15 wherein the trend is computed by computing differences between consecutive current murmur intensity measurements over the specified period of time and summing the differences.

17. The method of claim 11 further comprising measuring the pulmonary pressure and setting an alarm flag if the current murmur intensity exceeds the baseline murmur intensity by the first specified threshold amount and if the pulmonary pressure also exceeds another specified threshold amount.

18. The method of claim 11 further comprising pacing the heart in a programmed mode and adjusting the programmed mode if the current murmur intensity exceeds the baseline murmur intensity by a specified threshold amount.

19. The method of claim 18 further comprising pacing the heart in an atrial triggered mode and adjusting a programmed AV delay if the current murmur intensity exceeds the baseline murmur intensity by a specified threshold amount.

20. The method of claim 18 further comprising pacing the heart in a biventricular pacing mode and adjusting a biventricular offset if the current murmur intensity exceeds the baseline murmur intensity by a specified threshold amount.