METHODS AND SYSTEMS THAT MONITOR FOR AN IMPENDING MYOCARDIAL INFARCTION

• US 20110009712A1
• Filed: 07/08/2009
• Published: 01/13/2011
• Est. Priority Date: 07/08/2009
• Status: Active Grant

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Carlson, Mark, Dokko, Daniell, Fayram, Timothy A., Farazi, Taraneh Ghaffari
• Granted Patent: US 8,672,855 B2
• Time in Patent Office: Days
• US Class Current: 600/301
• CPC Class Codes: A61B 5/0084 for introduction into the body, e.g. by catheters A61B5/1459 takes precedence
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/02154 by optical transmission
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/026 Measuring blood flow A61B3/1233, A61B3/1241 take precedence
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• 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 5/7242 using integration
• CPC Class Codes: A61B 5/746 Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/36557 controlled by chemical substances in blood

Abstract

Implantable systems, and methods for use therewith, are provided for monitoring for an impending myocardial infarction. A signal indicative of changes in arterial blood volume is obtained. Such a signal can be a photoplethysmography signal or an impedance plethysmography signal. For each of a plurality of periods of time, a metric indicative of the areas under the curve of the signal or number of inflections in the signal is determined. An impending myocardial infarction is monitored for based on changes in the metric indicative of the area under the curve of the signal or number of inflections in the signal, and an alert and/or therapy is triggered in response to an impending myocardial infarction being predicted.

Claims

1. For use with an implanted system, a method for monitoring for an impending myocardial infarction (MI), comprising:

(a) using an implanted sensor to produce a plethysmography signal that is indicative of changes in arterial volume;

(b) for each of a plurality of periods of time, determining a metric indicative of the area under the curve of the plethysmography signal for the period of time;

(c) monitoring for an impending MI based on changes in the metric indicative of the area under the curve of the plethysmography signal; and

(d) triggering an alert and/or therapy in response to an impending MI being detected at step (c).

2. The method of claim 1, wherein:

step (a) comprises using an implanted photoplethysmography sensor to produce a photoplethysmography (PPG) signal that is indicative of changes in arterial volume; and

step (b) comprises for each of the plurality of periods of time, determining a metric indicative of the area under the curve of the PPG signal for the period of time.

3. The method of claim 1, wherein:

step (a) comprises using an implanted impedance plethysmography sensor to produce an impedance plethysmography (IPG) signal that is indicative of changes in arterial volume; and

step (b) comprises for each of the plurality of periods of time, determining a metric indicative of the area under the curve of the IPG signal for the period of time.

4. The method of claim 1, wherein step (c) includes distinguishing between an impending MI and a transient myocardial ischemic event.

5. The method of claim 1, further comprising determining a baseline of the metric indicative of area under the curve;

wherein step (c) comprises;

(c.1) comparing the determined metrics indicative of the area under the curve to the baseline; and

(c.2) predicting an impending MI if the determined metric indicative of the area under the curve falls below the baseline by at least a specified threshold.

6. The method of claim 5, wherein step (c.2) includes distinguishing between an impending MI and a transient myocardial ischemic event based on a length of time that the metric indicative of the area under the curve falls below the baseline by at least the specified threshold.

7. The method of claim 1, wherein step (c) comprises predicting an impending MI if a decrease beyond a specified threshold is detected, in the metric indicative of the area under the curve of the plethysmography signal, from one of the periods of time to the immediately following one of the periods of time.

8. The method of claim 1, wherein step (c) comprises predicting an impending MI if the metric indicative of the area under the curve of the plethysmography signal decreases by at least a specified amount for at least a specified period of time.

9. The method of claim 1, wherein the metric indicative of area under the curve is selected from the group consisting of:

an integral of at least one cycle of the plethysmography signal;

a width from the start to the end of a cycle of the plethysmography signal;

a full width at half maximum (FWHM) of a cycle of the plethysmography signal;

10. The method of claim 1, wherein step (c) includes:

(c.1) detecting changes in vascular stiffness based on changes in the area under the curve of the plethysmography signal; and

(c.2) monitoring for an impending MI based on changes in vascular stiffness that are detected based on changes in the area under the curve of the plethysmography signal.

11. The method of claim 10, wherein step (c.2) comprises predicting an impending MI if an increase in vascular stiffness beyond a specified threshold is detected.

12. The method of claim 10, wherein step (c.2) comprises predicting an impending MI if an increase in vascular stiffness beyond a specified threshold is detected within a specified time period.

13. An implantable system for monitoring for an impending myocardial infarction (MI), comprising:

an implantable sensor to produce a plethysmography signal that is indicative of changes in arterial volume;

a monitor configured to;

determine a metric indicative of the area under the curve of the plethysmography signal for each of a plurality of periods of time,

monitor for an impending MI based on changes in the metric indicative of the area under the curve of the plethysmography signal, and

trigger an alert and/or therapy in response to an impending MI being detected.

14. The system of claim 13, wherein the monitor is configured to monitor for an impending MI, based on changes in the metric indicative of the area under the curve of the plethysmography signal, by comparing the determined metrics indicative of the area under the curve to a baseline, and predicting an impending MI if the determined metric indicative of the area under the curve falls below the baseline by at least a specified threshold.

15. For use with a chronically implanted device, a method for monitoring for an impending myocardial infarction (MI), comprising:

(a) using an implanted sensor to produce a plethysmography signal that is indicative of changes in arterial volume;

(b) for each of a plurality of periods of time, determining a metric indicative of a number of inflections in the plethysmography signal for the period of time;

(c) monitoring for an impending MI based on changes in the metric indicative of the number of inflections in the plethysmography signal; and

(d) triggering an alert and/or therapy in response to an impending MI being detected at step (c).

16. The method of claim 15, wherein step (c) includes distinguishing between an impending MI and a transient myocardial ischemic event.

17. The method of claim 15, further comprising determining a baseline of the metric indicative of the number of inflections in the plethysmography signal;

wherein step (c) comprises;

(c.1) comparing the determined metrics indicative of the number of inflections to the baseline; and

(c.2) predicting an impending MI if the determined metric indicative of the metric indicative of the number of inflections increases beyond the baseline by at least a specified threshold.

18. The method of claim 17, wherein step (c.2) includes distinguishing between an impending MI and a transient myocardial ischemic event based on a length of time that the metric indicative of the number of inflections remains increased beyond the baseline by at least the specified threshold.

19. The method of claim 15, wherein step (c) comprises predicting an impending MI if an increase beyond a specified threshold is detected, in the metric indicative of the number of inflections in the plethysmography signal, from one of the periods of time to the immediately following one of the periods of time.

20. The method of claim 15, wherein step (c) comprises predicting an impending MI if the metric indicative of the number of inflections in the plethysmography signal increases by at least a specified amount for at least a specified period of time.

21. An implantable system for monitoring for an impending myocardial infarction (MI), comprising:

an implantable sensor to produce a plethysmography signal that is indicative of changes in arterial volume;

a monitor configured to

determine a metric indicative of a number of inflections in the plethysmography signal for each of a plurality of the periods of time,

monitor for an impending MI based on changes in the metric indicative of the number of inflections in the plethysmography signal, and

trigger an alert and/or therapy in response to an impending MI being detected.

22. The system of claim 21, wherein the monitor is configured to monitor for an impending MI, based on changes in the metric indicative of the number of inflections in the plethysmography signal, by comparing the determined metrics indicative of the number of inflections to a baseline, and predicting an impending MI if the determined metric indicative of the number of inflections increases above the baseline by at least a specified threshold.

23. For use with a chronically implanted device, a method for monitoring for an impending myocardial infarction (MI), comprising:

(a) obtaining

a first signal indicative of changes arterial volume, the first signal comprising one of a photoplethysmography (PPG) signal and an impedance-plethysmography (IPG) signal, and

a second signal indicative of electrical cardiac activity, the second signal comprising one of an electrocardiogram (ECG) signal and an intracardiac electrogram (IEGM) signal;

(b) determining, based on the first and second signals, a metric indicative of aortic pulse wave velocity (PWV);

(c) determining, based on the first signal, a metric indicative of diastolic blood pressure (DBP);

(d) determining, based on at least one of the first and second signals, a metric indicative of heart rate (HR);

(e) determining, based on the first signal, a metric indicative of vascular stiffness (VS);

(f) monitoring for an impending MI based on the metrics indicative of PWV, DBP, HR and VS; and

(g) triggering an alert and/or therapy in response to an impending MI being detected at step (f).

24. The method of claim 23, wherein step (f) comprises detecting an impending MI if the metrics indicative of PWV, DBP, HR and VS each satisfies a corresponding criteria indicative of an impending MI.

25. The method of claim 23, wherein step (f) comprises detecting an impending MI if a majority of the metrics indicative of PWV, DBP, HR and VS each satisfies a corresponding criteria indicative of an impending MI.