HFpEF detection using exertional heart sounds

1. A medical-device system, comprising:

a signal receiver circuit configured to receive exertion information of a subject and cardiac vibration acceleration information of the subject, the cardiac acceleration information comprising third heart sound (S 3 ) information of the subject; and

an assessment circuit configured to:

determine a period of rest of the subject using the received exertion information;

determine a period of exertion of the subject using the received exertion information;

determine a measure of cardiac acceleration information of the subject for the determined periods of rest;

determine a measure of cardiac acceleration information of the subject for the determined periods of exertion;

determine a change in magnitude or energy of the determined measure of cardiac acceleration information of the subject for the determined period of exertion relative to the determined measure of cardiac acceleration information of the subject at rest, and to for the determined period of rest;

determine an indication of heart failure with preserved ejection fraction (HFpEF) of the subject using the determined change in magnitude or energy of the determined measures; and

provide an output of the determined indication of HFpEF to a user interface for display to a user, or to another circuit to control or adjust a process or function of the medical-device system.

2. The system of claim 1 , wherein the cardiac acceleration information comprises the S 3 information of the subject and at least one of first heart sound (Si) information of the subject, second heart sound (S 2 ) information of the subject, or fourth heart sound (S 4 ) information of the subject, and

wherein the measure of cardiac acceleration information comprises a ratio of the S 3 information and at least one of the S 1 information, the S 2 information, or the S 4 information.

3. The system of claim 2 , wherein the S 1 information, the S 2 information, the S 3 information, and the S 4 information comprise a magnitude or energy of the respective information.

4. The system of claim 1 , wherein the assessment circuit is configured to:

trend determined measures of cardiac acceleration information of the subject for determined periods of rest;

trend determined measures of cardiac acceleration information of the subject for determined periods of exertion; and

determine the change in magnitude or energy of the determined measure of cardiac acceleration information of the subject for the determined period of exertion relative to the determined measure of cardiac acceleration information of the subject for the determined period of rest using the trends.

5. The system of claim 3 , wherein the signal receiver circuit is further configured to receive posture information of the subject, and

wherein the assessment circuit is configured to:

determine the period of rest of the subject using the received exertion information and the received posture information; and

determine the period of exertion of the subject using the received exertion information and the received posture information.

6. The system of claim 1 , wherein the assessment circuit is configured to:

trend determined changes in the determined measure of cardiac acceleration information of the subject for the determined period of exertion relative to the determined measure of cardiac acceleration information of the subject for the determined period of rest; and

determine the change in cardiac acceleration information of the subject using the trend.

7. The system of claim 1 , wherein the signal receiver circuit is configured to receive the cardiac acceleration information of the subject and the exertion information of the subject using the same acceleration sensor at different times, and

wherein the assessment circuit is configured to:

determine a level of exertion using acceleration information from the acceleration sensor;

detect a transition from a first exertion level to a second, lower exertion level;

determine, following the detected transition from the first exertion level to the second exertion level, a measure of cardiac acceleration information of the subject indicative of cardiac acceleration information of the subject at the first exertion level; and

determine, after a recovery period following the detected transition from the first exertion level to the second exertion level, a measure of cardiac acceleration information of the subject indicative of cardiac acceleration information of the subject at the second exertion level.

8. The system of claim 7 , comprising a posture sensor configured to sense posture information of the subject,

wherein the assessment circuit is configured to detect the transition from the first exertion level to the second, lower exertion level using the exertion information of the subject and the posture information of the subject.

9. The system of claim 7 , comprising the acceleration sensor configured to sense cardiac acceleration information of the subject and exertion information of the subject,

wherein the signal receiver circuit is configured to receive the cardiac acceleration information of the subject and the exertion information of the subject from the acceleration sensor, and

wherein the second exertion level is rest.

10. The system of claim 1 , comprising:

a cardiac acceleration sensor configured to sense the cardiac acceleration information of the subject; and

an activity sensor configured to sense exertion information of the subject,

wherein the signal receiver circuit is configured to receive the cardiac acceleration information of the subject from the cardiac acceleration sensor and the exertion information of the subject from the activity sensor.

11. The system of claim 1 , wherein the assessment circuit is configured to determine the indication of HFpEF of the subject using a determined change in cardiac acceleration information at exertion relative to cardiac acceleration information of the subject at rest greater than an HFpEF threshold.

12. The system of claim 1 , wherein, to determine the indication of HFpEF of the subject, the assessment circuit is configured to determine an indication of worsening HFpEF of the subject using the determined change in cardiac acceleration information, the system further comprising:

a user interface configured to provide a human-perceptible alert to the subject or a clinician using the determined indication of worsening HFpEF of the subject.

13. The system of claim 1 , wherein the assessment circuit is configured to distinguish between heart failure with reduced ejection fraction (HFrEF) and HFpEF using the determined change in magnitude or energy of the determined measures.

14. A method of controlling a medical-device system, comprising:

receiving exertion information of a subject and cardiac acceleration information of the subject using a signal receiver circuit, the cardiac acceleration information comprising third heart sound (S 3 ) information of the subject;

determining, using an assessment circuit, a period of rest of the subject using the received exertion information;

determining, using the assessment circuit, a period of exertion of the subject using the received exertion information;

determining, using the assessment circuit, a measure of cardiac acceleration information of the subject for the determined periods of rest;

determining, using the assessment circuit, a measure of cardiac acceleration information of the subject for the determined periods of exertion;

determining, using the assessment circuit, a change in magnitude or energy of the determined measure of cardiac acceleration information of the subject for the determined period of exertion relative to the determined measure of cardiac acceleration information of the subject for the determined period of rest;

determining, using the assessment circuit, an indication of heart failure with preserved ejection fraction (HFpEF) of the subject using the determined change in magnitude or energy of the determined measures; and

providing, using the assessment circuit, an output of the determined indication of HFpEF to a user interface for display to a user, or to another circuit to control or adjust a process or function of the medical-device system.

15. The method of claim 14 , wherein the cardiac acceleration information comprises the S 3 information of the subject and at least one of first heart sound (S 1 ) information of the subject, second heart sound (S 2 ) information of the subject, or fourth heart sound (S 4 ) information of the subject.

16. The method of claim 15 , comprising:

trending determined measures of cardiac acceleration information of the subject for determined periods of rest; and

trending determined measures of cardiac acceleration information of the subject for determined periods of exertion,

wherein determining the change in magnitude or energy of the determined measures of cardiac acceleration information of the subject for the determined period of exertion relative to the determined period of rest includes using the trends, and

wherein determining the indication of HFpEF of the subject includes using the determined change in magnitude or energy of the determined measures.

17. The method of claim 15 , comprising receiving posture information of the subject using the signal receiver circuit,

wherein determining the period of rest of the subject includes using the received exertion information and the received posture information, and

wherein determining the period of exertion of the subject includes using the received exertion information and the received posture information.

18. The method of claim 14 , comprising trending determined changes in-the determined measure of cardiac acceleration information of the subject for the determined period of exertion relative to the determined measure of cardiac acceleration information of the subject for the determined period of rest,

wherein determining the change in cardiac acceleration information of the subject includes using the trend.

19. The method of claim 14 , wherein receiving the cardiac acceleration information of the subject and the exertion information of the subject includes using the same acceleration sensor at different times, the method further comprising:

determining a level of exertion using acceleration information from the acceleration sensor;

detecting a transition from a first exertion level to a second, lower exertion level;

determining, following the detected transition from the first exertion level to the second exertion level, a first measure of cardiac acceleration information of the subject indicative of cardiac acceleration information of the subject at the first exertion level; and

determining, after a recovery period following the detected transition from the first exertion level to the second exertion level, a second measure of cardiac acceleration information of the subject indicative of cardiac acceleration information of the subject at the second exertion level.

20. The method of claim 14 , wherein determining the indication of HFpEF of the subject includes using a determined change in cardiac acceleration information at exertion relative to cardiac acceleration information of the subject at rest greater than an HFpEF threshold.