Method, apparatus and system for predicting electromechanical dissociation

• US 8,523,777 B2
• Filed: 04/15/2008
• Issued: 09/03/2013
• Est. Priority Date: 04/19/2007
• Status: Active Grant

• Current Assignee: Baxter Healthcare SA (Baxter International Inc.), Baxter International Inc.
• Original Assignee: Cheetah Medical, Inc. (Baxter International Inc.)
• Inventors: Avidor, Yoav, Keren, Hanan
• Primary Examiner(s): Koharski, Christopher D
• Assistant Examiner(s): Patel, Natasha
• Application Number:
  US12/596,483
• Publication Number:
  US 20100217140A1
• Time in Patent Office: 1,967 Days
• Field of Search: 600/454, 600/509, 600/500
• US Class Current: 600/454
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295

Abstract

A method of predicting onset of electromechanical dissociation in a heart of a subject is disclosed. The method comprises: extracting from the composite input signal an electrocardiac signal and determining electrical activity of the heart based on the electrocardiac signal; extracting from the composite input signal a radiofrequency signal and determining blood flow measure based on the radiofrequency signal; and if the blood flow measure is below a predetermined threshold and the electrical activity is above a predetermined threshold, then predicting the onset of electromechanical dissociation.

Claims

1. A method of predicting onset of electromechanical dissociation in a heart of a subject using a composite input electrical signal received from the subject, the method comprising:

extracting from the composite input signal an electrocardiac signal and determining electrical activity of the heart based on said electrocardiac signal;

extracting from the composite input signal a radiofrequency signal and determining blood flow measure based on said radiofrequency signal; and

if said blood flow measure is below a predetermined threshold and said electrical activity is above a predetermined threshold, then predicting a future onset of electromechanical dissociation.

2. A method of predicting onset of electromechanical dissociation in a heart of a subject, comprising:

transmitting output radiofrequency signals to the subject;

receiving a composite input electrical signal from the subject; and

executing the method of claim 1.

3. The method of claim 1, further comprising reducing or eliminating amplitude modulation of said radiofrequency component so as to provide a signal of substantially constant envelope.

4. The method of claim 1, further comprising filtering said radiofrequency signal using a dynamically variable filter.

9. The method of claim 4, wherein said dynamically variable filter is adapted in response to a change in a physiological condition of the subject.

10. The method of claim 9, wherein said physiological condition is a heart rate of the subject.

11. The method of claim 10, wherein a lower frequency bound characterizing said filter is about 0.9*(HR/60) Hz at all times, wherein said HR is said heart rate in units of beats per minute.

12. The method of claim 10, wherein an upper frequency bound characterizing said filter is about 6+1.5*[(HR/60)−

1] Hz at all times, wherein said HR is said heart rate in units of beats per minute.

13. The method of claim 1, wherein said electrocardiac signal comprises an ECG signal.

14. The method of claim 13, wherein said determination of said electrical activity comprises determination of a QRS rate from said ECG signal.

15. The method of claim 1, wherein said blood flow measure comprises cardiac output.

16. The method of claim 15, wherein the onset of electromechanical dissociation is predicted if said cardiac output is reduced by at least 50% and said electrical activity is characterized by pulse rate of at least 60 pulses per minute.

17. The method of claim 15, wherein the onset of electromechanical dissociation is predicted if, over a period of about five minutes, said cardiac output is less than 1 liter per minute and said electrical activity is characterized by a rhythm of at least 40 cycles per minute.

18. The method claim 1, wherein said blood flow measure comprises cardiac index.

19. The method of claim 18, wherein the onset of electromechanical dissociation is predicted if, over a period of about five minutes, said cardiac index is less than 1 liter per minute per square meter and said electrical activity is characterized by a rhythm of at least 40 cycles per minute.

20. The method of claim 18, wherein the onset of electromechanical dissociation is predicted if, over a period of about five minutes, said cardiac index is less than 0.75 liter per minute per square meter and said electrical activity is characterized by a rhythm of at least 40 cycles per minute.

5. Apparatus for predicting onset of electromechanical dissociation in a heart of a subject, the apparatus comprising:

an input unit for receiving a composite input electrical signal from the subject;

an electrocardiac unit for extracting from the composite input signal an electrocardiac signal and determining electrical activity of the heart based on said electrocardiac signal;

a radiofrequency unit for extracting a radiofrequency signal from the composite input signal and determining blood flow measure based on said radiofrequency signal; and

an output unit for outputting a signal predicting a future onset of electromechanical dissociation if said blood flow measure is below a predetermined threshold and said electrical and activity is above a predetermined threshold.

6. A system for predicting onset of electromechanical dissociation in a heart of a subject, comprising:

a radiofrequency generator for generating output radiofrequency signals;

a plurality of electrodes designed for transmitting said output radiofrequency signals to the subject and for sensing a composite input electrical signal from the subject; and

the apparatus of claim 5.

7. The apparatus claim 5, wherein the apparatus further comprises an envelope elimination unit designed and configured for reducing or eliminating amplitude modulation of said radiofrequency signal so as to provide a radiofrequency signal of substantially constant envelope.

8. The apparatus of claim 5, wherein the apparatus further comprises a filtering unit configured for filtering said radiofrequency signal using dynamically variable filter.