Methods and apparatus for detecting heart failure decompensation event and stratifying the risk of the same

Patent metadata

Field	Value
Publication number	US-9622664-B2
Application number	US-201414510392-A
Country	US
Kind code	B2
Filing date	Oct 9, 2014
Priority date	Nov 4, 2013
Publication date	Apr 18, 2017
Grant date	Apr 18, 2017

Abstract

Devices and methods for detecting heart failure (HF) events or identifying patient at elevated risk of developing future HF events, such as events indicative of HF decompensation status, are described. The devices and methods can detect an HF event or predict HF risk using one or more physiologic sensor signals including an electrogram and a heart sound signal. A medical device can use the physiologic signals to calculate one more signal metrics indicative of systolic function of the heart, including relative timing between first and second signal features selected from signal features generated from the electrogram or the heart sound signals. The medical device can detect an HF event using the signal metrics, or use the signal metrics to calculate a composite risk indicator indicative of the likelihood of the patient later developing an event indicative of worsening of HF.

First claim

What is claimed is:

1. A system, comprising:
an ambulatory medical device (AMD) including:
a cardiac electrogram sensor circuit configured to sense from a patient at least one electrogram and to generate one or more electrogram features using the sensed electrogram, the electrogram indicative of electrical activity of a heart of the patient;
a heart sound detector circuit configured to sense from the patient a vibratory or acoustic heart sound (HS) signal and to generate one or more HS features using the sensed HS signal;
a target event indicator generator circuit configured to:
calculate a first normalized signal metric including a first relative timing normalized by a normalization factor, the first relative timing measured between a first pair of signal features selected from the one or more electrogram features or the one or more HS features; and
calculate a second unnormalized signal metric including a second relative timing measured between a different second pair of signal features selected from the one or more electrogram features or the one or more HS features signal metric; and

a physiologic event detector circuit coupled to the target event indicator generator circuit, the physiologic event detector circuit configured to detect a target physiologic event using a combination of at least the first normalized signal metric and the second unnormalized signal metric.

2. The system of claim 1 , wherein the physiologic event detector circuit is configured to detect worsening of heart failure.

3. The system of claim 1 , wherein the target event indicator generator circuit is configured to calculate the first normalized signal metric including an electrogram-to-heart sound time interval indicative of a pre-ejection period (PEP), the electrogram-to-heart sound time interval including a delay from a first electrogram feature to a second HS feature.

4. The system of claim 1 , wherein the target event indicator generator circuit is configured to calculate the second unnormalized signal metric including an intra-heart sound time interval indicative of a left-ventricular ejection time (LVET), the intra-heart sound time interval including an interval between a first heart sound S1 and a second heart sound S2 of the sensed HS signal.

5. The system of claim 1 , wherein at least one of the first normalized or second unnormalized signal metric includes a ratio between a first time interval indicative of the PEP and a second time interval indicative of the LVET.

6. The system of claim 1 , wherein the target event indicator generator circuit is configured to generate the normalization factor including a representative value of a physiologic time interval.

7. The system of claim 1 , comprising a heart sound sensor coupled to the heart sound detector circuit, wherein the HS sensor is adapted to sense from the patient a physiologic signal indicative of heart sound.

8. The system of claim 1 , wherein the heart sound detector circuit includes at least one filter circuit configured to filter the sensed heart sound signal to a specified frequency range, the heart sound detector configured to generate the HS features including timing of at least one of a first heart sound S1, a second heart sound S2, or a third heart sound S3 using the filtered HS signal.

9. The system of claim 8 , wherein the filter circuit includes a double differentiator circuit configured to calculate a double differentiation of the sensed HS signal.

10. The system of claim 8 , wherein the filter circuit includes a band-pass filter.

11. The system of claim 10 , wherein the band-pass filter has cutoff frequencies of 5 Hz and 90 Hz.

12. The system of claim 1 , wherein the physiologic event detector circuit is further configured to:
generate, for the one or more signal metrics, respective predicted performance measures including one or more of a predicted sensitivity, a predicted specificity, or a predicted signal quality; and
detect the target physiologic event further using the respective predicted performance measures.

13. A system, comprising:
a signal analyzer circuit, including:
a cardiac electrogram sensor circuit configured to sense at least one electrogram of a heart of a patient and to generate one or more electrogram features using the sensed electrogram, the electrogram indicative of electrical activity of the heart;
a heart sound (HS) signal detector circuit configured to sense a HS signal of the patient and to generate one or more HS features using the sensed HS signal; and
a signal metric generator circuit configured to:
calculate a first normalized signal metric including a first relative timing normalized by a normalization factor, the first relative timing measured between a first pair of signal features selected from the one or more electrogram features or the one or more HS features; and
calculate a second unnormalized signal metric including a second relative timing measured between a different second pair of signal features selected from the one or more electrogram features or the one or more HS features a normalized first signal metric using the first signal metric and a normalization factor; and

a risk stratifier circuit configured to calculate a composite risk indicator using a combination of at least the first normalized signal metric and the second unnormalized signal metric, the composite risk indicator indicative of the likelihood of the patient developing a future target physiologic event.

14. The system of claim 13 , wherein:
the cardiac electrogram sensor circuit is configured to generate the one or more electrogram features including timing of an R wave on the sensed electrogram;
the HS signal detector circuit is configured to generate the one or more HS features including relative timing of a first heart sound S1, a second heart sound S2, or a third heart sound S3 with respect to the timing of the R wave; and
the signal metric generator circuit is configured to calculate the first normalized signal metric using at least a first time interval indicative of the pre-ejection period (PEP) and to calculate the second unnormalized signal metric using at least a second time interval indicative of the left ventricular ejection time (LVET), the first time interval including an interval between the R wave and the S1 heart sound, the second time interval including an interval between the S1 and S2 heart sounds.

15. The system of claim 13 , wherein the risk stratifier circuit is configured to calculate for the first normalized signal metric and the second unnormalized signal metric respective individual risk scores, and to calculate the composite risk indicator using a linear or nonlinear combination of the individual risk scores for the first normalized signal metric and the second unnormalized signal metric.

16. A method, comprising:
receiving from a patient at least one electrogram indicative of electrical activity of a heart of the patient;
generating one or more electrogram features using the sensed electrogram;
receiving from the patient a physiologic signal indicative of heart sound (HS);
processing the sensed physiologic signal including filtering the sensed physiologic signal using a filter with specified frequency response;
generating one or more HS features using the processed physiologic signal;
calculating a first normalized signal metric including a first relative timing normalized by a normalization factor, the first relative timing measured between a first pair of signal features selected from the one or more electrogram features or the one or more HS features;
calculate a second unn

Assignees

• Cardiac Pacemakers Inc

Inventors

• An Qi
• Thakur Pramodsingh Hirasingh
• Zhang Yi
• Averina Viktoria A

Classifications

• A61B5/02028 Primary

  Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction · CPC title

• A61B5/0006

  ECG or EEG signals · CPC title

• A61B5/686

  Permanently implanted devices, e.g. pacemakers, other stimulators, biochips (A61B5/6861 takes precedence) · CPC title

• A61B5/0205

  Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition · CPC title

• A61B7/045

  Detection of Korotkoff sounds (A61B5/0225 takes precedence; measuring blood pressure A61B5/021) · CPC title