Systems and methods for detecting ischemic events

• US 9,095,257 B2
• Filed: 10/31/2013
• Issued: 08/04/2015
• Est. Priority Date: 08/28/2003
• Status: Active Grant

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Farai, Taraneh Ghaffari
• Primary Examiner(s): Gedeon, Brian T
• Application Number:
  US14/069,197
• Publication Number:
  US 20140058278A1
• Time in Patent Office: 642 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/02405 Determining heart rate variability
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/1118 Determining activity level
• CPC Class Codes: A61B 5/283 Invasive
• CPC Class Codes: A61B 5/364 Detecting abnormal ECG interval, e.g. extrasystoles, ectopic heartbeats
• 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 5/7275 Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61B 5/7282 Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• 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 1/36114 Cardiac control, e.g. by vagal stimulation stimulating the heart A61N1/362
• 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 1/36592 controlled by the heart rate variability
• CPC Class Codes: A61N 1/3962 in combination with another heart therapy
• CPC Class Codes: A61N 1/39622 Pacing therapy
• CPC Class Codes: G16H 40/63 for local operation
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

Embodiments of the present invention relate to implantable systems, and method for use therein, that can detect myocardial ischemic events. In accordance with specific embodiments of the present invention, short-term fluctuations in cardiac intervals that follow premature ventricular contractions (PVCs) are monitored. This allows myocardial ischemic events to be detected based on these monitored fluctuations. The cardiac intervals for which fluctuations are being monitored can be, for example, RR intervals. Alternatively, or additionally, short-term fluctuations in other types of cardiac intervals may be monitored. Such other cardiac intervals include, for example, PR intervals, PP intervals, QT intervals and RT intervals.

Claims

1. An implantable system, comprising:

a monitor that monitors short-term fluctuations in cardiac intervals that follow premature ventricular contractions;

a detector that detects ischemic events based on the monitored fluctuations, determines whether a patient is experiencing an ischemic event, and, when the patient is experiencing an ischemic event, at least one of the following;

triggers myocardial ischemia therapy, transmits an alert that an action appropriate to the detection of myocardial ischemia should be taken, and stores a measure of myocardial ischemia burden.

2. The system of claim 1, wherein the monitor monitors cardiac intervals that both precede and follow each premature ventricular contraction, such that cardiac intervals that precede the premature ventricular contraction can be used in calculating the short-term fluctuations in cardiac intervals that follow the premature ventricular contraction.

3. The system of claim 1, wherein the monitor monitors short-term fluctuations in cardiac intervals within beats that follow a premature ventricular contraction.

4. The system of claim 1, wherein the premature ventricular contractions are intrinsic, induced or simulated, or combinations thereof.

5. The system of claim 1, wherein the detector further:

determines a degree of short-term fluctuations in cardiac intervals that follow premature ventricular contractions; and

identifies ischemic events when the measured degree crosses a corresponding threshold in a specified direction.

6. The system of claim 1, wherein the detector further:

determines a degree of short-term fluctuations in cardiac intervals that follow premature ventricular contractions; and

identifies ischemic events when the measured degree deviates from a baseline by more than a threshold.

7. The system of claim 6, wherein the monitor monitors short-term fluctuations in cardiac intervals that follow premature ventricular contractions when a patient is at rest and after the patient is at rest, and wherein the detector further determines a baseline based on the values measured when the patient is at rest and determines whether a patient is experiencing an ischemic event based on a comparison of the baseline to the monitored short-term fluctuations in cardiac intervals that follow premature ventricular contractions after the patient is at rest.

8. The system of claim 7, wherein the monitor and detector update the baseline from time to time.

9. The system of claim 1, wherein the monitored fluctuations comprise a degree of heart rate turbulence (HRT), and wherein the detector identifying periods, when the degree of HRT crosses a corresponding threshold in a specified direction, as ischemic events.

10. The system of claim 1, wherein the monitored fluctuations comprise degree of heart rate turbulence (HRT), and wherein the detector identifying periods, when the degree of HRT deviates from a baseline by more than a threshold amount, as ischemic events.

11. The system of claim 10, wherein the monitored fluctuations comprise at least one HRT parameter measured when a patient is at rest;

and wherein the detector determines the baseline based on the at least one HRT parameter measured when the patient is at rest.

12. The system of claim 10, wherein the monitor and detector update the baseline from time to time.

13. The system of claim 11, wherein the at least one HRT parameter comprises at least one of:

turbulence onset (TO);

turbulence slope (TS); and

turbulence timing (TT).

14. The system of claim 1, wherein the detector triggers myocardial ischemia therapy when the patient is experiencing an ischemic event, and wherein the myocardial ischemia therapy comprises stimulating the vagal nerve, and wherein the system further comprises a vagal stimulation electrode that stimulates the vagal nerve when triggered by the detector.

15. An implantable system for detecting myocardial ischemic events, comprising:

a monitor that monitors morphology of a signal that is indicative of cardiac intervals that follow premature ventricular contractions; and

a detector that detects myocardial ischemic events based on the monitored morphology, determines whether a patient is experiencing an ischemic event, and when the patient is experiencing an ischemic event, at least one of the following;

triggers myocardial ischemia therapy, transmits an alert that an action appropriate to the detection of myocardial ischemia should be taken, and stores a measure of myocardial ischemia burden.

16. The system of claim 15, wherein the detector compares the monitored morphology to a baseline morphology, and detects myocardial ischemic events when the monitored morphology differs from the baseline morphology by more than a specified degree.

17. The system of claim 15, wherein the baseline morphology is determined based on measurements of cardiac intervals that correspond to premature ventricular contractions that occur while a patient is at rest.

18. The system of claim 15, wherein the monitor monitors fluctuations in cardiac intervals corresponding to the first N successive beats that follow premature ventricular contractions, where N is an integer between 10 and 25.

19. The system of claim 15, further comprising:

a display that displays the present ischemia burden with previously determined ischemia burdens, wherein the detector further compares the present ischemia burden with the previously determined ischemia burdens, and determines whether a patient'"'"'s cardiovascular condition has worsened or improved over a time period based on the comparison.

20. The system of claim 15, wherein the detector triggers myocardial ischemia therapy when the patient is experiencing an ischemic event, and wherein the myocardial ischemia therapy comprises stimulating the vagal nerve, and wherein the system further comprises a vagal stimulation electrode that stimulates the vagal nerve when triggered by the detector.