Method of noninvasively determining a patient's susceptibility to arrhythmia

• US 5,951,484 A
• Filed: 07/31/1998
• Issued: 09/14/1999
• Est. Priority Date: 08/01/1997
• Status: Expired due to Term

• Current Assignee: Harbinger Medical, Inc.
• Original Assignee: Harbinger Medical, Inc.
• Inventors: Hoium, Harold H., Ryan, Stephen J.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): LAYNO, CARL HERNANDZ
• Application Number:
  US09/127,231
• Time in Patent Office: 410 Days
• Field of Search: 600/515-518, 607/10
• US Class Current: 600/515
• CPC Class Codes: A61B 5/303 Patient cord assembly, e.g. cable harness
• CPC Class Codes: A61B 5/339 Displays specially adapted therefor
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/366 Detecting abnormal QRS complex, e.g. widening
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371
• CPC Class Codes: A61N 1/37247 User interfaces, e.g. input or presentation means

Abstract

A method for detecting a patient'"'"'s susceptibility to arrhythmias and cardiac tissue abnormality is disclosed. The method consists of using a computer, a display, software loaded onto the computer that generates graphical user interfaces (GUIs), an electronic interface, and a plurality of electrodes. The electronics interface is in electronic communication with the computer, and further in electronic communication with the electrodes that are placed by self-adhesion at predetermined locations on a test subject. According to one aspect of the invention, the method enables a user, typically a medical professional, to initiate, with minimal input, certain diagnostic tests involving observing and analyzing a series of QRS complexes, some of which are biased with a subpacing current, and others of which are unbiased. The signals are then compared, and the differences are analyzed to detect a patient'"'"'s susceptibility to arrhythmias and cardiac tissue abnormality.

Claims

1. A method for detecting patient susceptibility to arrhythmias comprising the steps of:

providing means for injecting low level electromagnetic energy stimulations into a patient'"'"'s body suitable to alter at least one cardiac signal to allow a comparison of acquired distinguishable signal differences with at least one other cardiac signal which has not been affected by said injected energy;

connecting a lead system for both sensing the cardiac signals and delivering the injected energy to said means for injecting low level electromagnetic energy into the patient'"'"'s body, said lead system, comprising a plurality of energy sensing and energy delivery leads and a reference lead; and

utilizing sensing improvement means for improving the quality of the sensed electromagnetic energy during the stimulation and acquisition process, said sensing improvement means utilization comprises the steps of;

comprises switch means connected between energy delivery leads so that the switch means is operable relative to the termination of the output current and switches from a high impedance to a low impedance for a short period of time to allow dissipation of any voltage present; and

using a fast recovery amplifier method for rapid recovery of the amplifier following stimulation signals.

2. The method of claim 1, further comprising the steps of evaluating baseline noise and continuing the stimulation and data acquisition process until enough data has been acquired to allow statistical noise reduction to a predetermined level.

3. The method of claim 1, in which said sensing improvement means utilization step further comprises the step of providing the energy delivery leads with shunting means connected between said leads.

4. A method for detecting patient susceptibility to arrhythmias comprising the steps of:

providing means for injecting low level electromagnetic energy stimulations into a patient'"'"'s body suitable to alter at least one cardiac signal to allow a comparison of acquired distinguishable signal differences with at least one other cardiac signal which has not been affected by said injected energy;

connecting a lead system for both sensing the cardiac signals and delivering the injected energy to said means for injecting low level electromagnetic energy into the patient'"'"'s body, said lead system comprising a plurality of energy sensing and energy delivery leads; and

utilizing sensing improvement means for improving the quality of the sensed electromagnetic energy, comprising using a lead effect modeling and correction algorithm which corrects for signal artifacts during stimulation and acquisition cycles during post-processing of acquired signal data.

5. The method of claim 4, in which the lead system connecting step further comprises connection of a body surface reference point with the lead system.

6. The method of claim 5, in which the sensing improvement means utilization comprises the step of using a fast recovery amplifier method for rapid recovery of the amplifier following stimulation signals.

7. The method of claim 6, in which the fast recovery amplifier step comprises the steps of:

configuring an electronic track and hold switch between a pre-switch stage and a post-switch stage of the amplifier so that when the switch is opened, the switch uses a lower capacitance reference point of the differential signal between positive and negative leads; and

configuring the track and hold switch to remain opened during stimulation and a blanking period following stimulation.

8. The method of claim 6, wherein the utilizing sensing improvement means for improving the quality of the sensed electromagnetic energy during the stimulation and acquisition process acquires a reference lead.

9. The method of claim 7, further comprising the steps of:

disengaging the track and hold switch to an open position during stimulation; and

configuring the track and hold switch so that when in an open position the switch provides a hold function that holds the signal level for post-switch stages at a constant output and connects the lower capacitance reference signal to the pre-switch stages.

10. The method of claim 9, further comprising the step of configuring a clamping circuit to engage when the input signal is greater than about ±

5 millivolts.

11. The method of claim 7, further comprising the step of filtering the acquired stimulation signal to eliminate possible high frequency, switch-related artifacts.

12. The method of claim 6, in which the fast recovery amplifier performs the steps of:

configuring an electronic track and hold switch between a pre-switch stage and a post-switch stage of the amplifier so that when the switch is closed the switch uses a lower capacitance reference point of the differential signal between positive and negative leads; and

configuring a clamping circuit for switching to an engaged position when the input signal is greater than about ±

5 millivolts; and

configuring a clamping circuit to engage when the input signal is greater than about ±

5 millivolts.

13. A method for detecting patient susceptibility to arrhythmias comprising the steps of:

providing means for injecting low level electromagnetic energy stimulations into a patient'"'"'s body suitable to alter at least one cardiac signal to allow a comparison of acquired distinguishable signal differences with at least one other cardiac signal which has not been affected by said injected energy;

connecting a lead system for both sensing the cardiac signals and delivering the injected energy to said means for injecting low level electromagnetic energy into the patient'"'"'s body, said lead system comprising a plurality of energy sensing and energy delivery leads; and

utilizing sensing improvement means for improving the quality of the sensed electromagnetic energy, comprising using a lead position correction algorithm which corrects for signal artifacts during stimulation and acquisition cycles.

14. A method for detecting patient susceptibility to arrhythmias comprising the steps of:

providing means for injecting low level electromagnetic energy stimulations into a patient'"'"'s body suitable to alter at least one cardiac signal to allow a comparison of acquired distinguishable signal differences with at least one other cardiac signal which has not been affected by said injected energy;

connecting a lead system for both sensing the cardiac signals and delivering the injected energy to said means for injecting low level electromagnetic energy into the patient'"'"'s body, said lead system comprising a plurality of energy sensing and energy delivery leads; and

utilizing sensing improvement means for improving the quality of the sensed electromagnetic energy, comprising using a lead position correction algorithm which corrects for signal artifacts during stimulation and acquisition cycles during post-processing of acquired signal data.

15. A method for detecting patient susceptibility to arrhythmias comprising the steps of:

providing means for injecting low level electromagnetic energy stimulations into a patient'"'"'s body suitable to alter at least one cardiac signal to allow a comparison of acquired distinguishable signal differences with at least one other cardiac signal which has not been affected by said injected energy;

connecting a lead system for both sensing the cardiac signals and delivering the injected energy to said means for injecting low level electromagnetic energy into the patient'"'"'s body, said lead system comprising a plurality of energy sensing and energy delivery leads; and

utilizing sensing improvement means for improving the quality of the sensed electromagnetic energy, comprising using a muscle response correction algorithm which corrects for signal artifacts during stimulation and acquisition cycles.

16. A method for detecting patient susceptibility to arrhythmias comprising the steps of:

providing means for injecting low level electromagnetic energy stimulations into a patient'"'"'s body suitable to alter at least one cardiac signal to allow a comparison of acquired distinguishable signal differences with at least one other cardiac signal which has not been affected by said injected energy;

connecting a lead system for both sensing the cardiac signals and delivering the injected energy to said means for injecting low level electromagnetic energy into the patient'"'"'s body, said lead system comprising a plurality of energy sensing and energy delivery leads; and

utilizing sensing improvement means for improving the quality of the sensed electromagnetic energy, comprising using a muscle response correction algorithm which corrects for signal artifacts during post-processing of acquired signal data.

17. A method for detecting patient susceptibility to arrhythmias comprising the steps of:

providing means for injecting low level electromagnetic energy stimulations into a patient'"'"'s body suitable to alter at least one cardiac signal to allow a comparison of acquired distinguishable signal differences with at least one other cardiac signal which has not been affected by said injected energy;

connecting a lead system for both sensing the cardiac signals and delivering the injected energy to said means for injecting low level electromagnetic energy into the patient'"'"'s body, said lead system comprising a plurality of energy sensing and energy delivery leads; and

applying a plurality of stimulations during the stimulation and acquisition process, the application of the stimulations being commenced between the T and P waves during a period of low signal level prior to the R-wave detection.

18. A method for detecting patient susceptibility to arrhythmias comprising the steps of:

providing means for injecting low level electromagnetic energy stimulations into a patient'"'"'s body suitable to alter at least one cardiac signal to allow a comparison of acquired distinguishable signal differences with at least one other cardiac signal which has not been affected by said injected energy;

connecting a lead system for both sensing the cardiac signals and delivering the injected energy to said means for injecting low level electromagnetic energy into the patient'"'"'s body, said lead system comprising a plurality of energy sensing and energy delivery leads; and

applying a plurality of stimulations during the stimulation and acquisition process, and insuring that each of the stimulations have approximately the same energy and duration as the stimulations delivered at other times in the cardiac cycle.

19. A method for detecting patient susceptibility to arrhythmias comprising the steps of:

providing means for injecting low level electromagnetic energy stimulations into a patient'"'"'s body suitable to alter at least one cardiac signal to allow a comparison of acquired distinguishable signal differences with at least one other cardiac signal which has not been affected by said injected energy;

connecting a lead system for both sensing the cardiac signals and delivering the injected energy to said means for injecting low level electromagnetic energy into the patient'"'"'s body, said lead system comprising a plurality of energy sensing and energy delivery leads;

providing stimulation signals within a lead effect modeling time period between the T and P waves, at the beginning and periodically throughout the stimulation and acquisition process;

determining the response to the stimulations for a period of up to about 50 milliseconds for each of said stimulations;

creating a lead effect model by combining the response of the stimulations during said determining period to generate a response signal; and

utilizing the derived response signal to mathematically attribute electrical artifact and muscle activity.

20. The method of claim 19, in which the determining step comprises removing any baseline signal by subtracting the corresponding waveform having a non-stimulating T-P interval from the current signal.

21. A method for detecting patient susceptibility to arrhythmias comprising the steps of:

providing means for injecting low level electromagnetic energy stimulations into a patient'"'"'s body suitable to alter at least one cardiac signal to allow a comparison of acquired distinguishable signal differences with at least one other cardiac signal which has not been affected by said injected energy;

connecting a lead system for both sensing the cardiac signals and delivering the injected energy to said means for injecting low level electromagnetic energy into the patient'"'"'s body, said lead system comprising a plurality of energy sensing and energy delivery leads; and

providing stimulation signals within a lead effect modeling time period between the T and P waves, at the beginning and periodically throughout the stimulation and acquisition process.

22. The method of claim 21, further comprising the step of utilizing a baseline shift with a time constant decay.

23. The method of claim 22, in which the baseline shift is determined by comparing samples prior to stimulations during the lead effect modeling time period to samples following the lead effect modeling time period.

24. The method of claim 23, further comprising the step of sampling the decay following the lead effect modeling time period to determine a time constant for the decay.

25. The method of claim 22, in which the decay is determined by determining the decay over about 10 milliseconds.

26. The method of claim 22, in which the decaying baseline shift is mathematically removed from the acquired data following the lead effect modeling time period.

27. The method of claim 22, in which the decaying baseline shift is mathematically removed for up to about 300 milliseconds following the end of the lead effect modeling time period.

28. A method for detecting patient susceptibility to arrhythmias comprising the steps of:

providing means for injecting low level electromagnetic energy stimulations into a patient'"'"'s body suitable to alter at least one cardiac signal to allow a comparison of acquired distinguishable signal differences with at least one other cardiac signal which has not been affected by said injected energy;

connecting a lead system for both sensing the cardiac signals and delivering the injected energy to said means for injecting low level electromagnetic energy into the patient'"'"'s body, said lead system comprising a plurality of energy sensing and energy delivery leads;

configuring a plurality of the sensing leads with a fast recovery material for rapid dissipation of any induced energy; and

configuring a plurality of the energy delivery leads to have a low impedance.

29. A method for detecting patient susceptibility to arrhythmias comprising the steps of:

providing means for injecting low level electromagnetic energy stimulations into a patient'"'"'s body suitable to alter at least one cardiac signal to allow a comparison of acquired distinguishable signal differences with at least one other cardiac signal which has not been affected by said injected energy;

connecting a lead system for both sensing the cardiac signals and delivering the injected energy to said means for injecting low level electromagnetic energy into the patient'"'"'s body, said lead system comprising a plurality of energy sensing and energy delivery leads;

providing the energy delivery leads with shunting means connected between said leads; and

providing switch means configured to sense termination of an output current in the energy delivery leads and then switch from a high impedance to a low impedance for a short period of time to allow dissipation of any voltage present.

30. The method of claim 29, in which the switch means switches between an initial high impedance of greater than about 5,000 ohms and a lower impedance of less than about 500 ohms.

31. The method of claim 29, in which the switching between high and low impedances occurs within a time of less than about 1 millisecond.

32. A method for detecting patient susceptibility to arrhythmias comprising the steps of:

providing means for injecting low level electromagnetic energy stimulations into a patient'"'"'s body suitable to alter at least one cardiac signal to allow a comparison of acquired distinguishable signal differences with at least one other cardiac signal which has not been affected by said injected energy;

connecting a lead system for both sensing the cardiac signals and delivering the injected energy to said means for injecting low level electromagnetic energy into the patient'"'"'s body, said lead system comprising a plurality of energy sensing and energy delivery leads;

configuring the leads of said lead system at a plurality of external locations on the patient'"'"'s skin;

maintaining each of the leads of said lead system in the same locations during a time period during which cardiac signals include a detected plurality of stimulated and non-stimulated cardiac signals; and

configuring said lead system to sense the spatial direction of cardiac wavefront.

33. The method of claim 32, further comprising the step of determining the magnitude and direction of the cardiac wavefronts.

34. The method of claim 32, further comprising the step of processing and analyzing the directional signals.

35. The method of claim 34, further comprising the step of comparing and displaying the directional data of stimulated and non-stimulated cardiac signals as acquired by leads which have remained stationary throughout the time period of the transmission and detection of the signals resulting in the processed cardiac signals.

36. The method of claim 35, in which the comparing step is performed for cardiac signals throughout all locations of the QRST complex independent of signal amplitude.

37. A method for detecting patient susceptibility to arrhythmias, using a computer and a computer display, the method comprising:

installing on said computer a diagnostic software program comprising data files and application programs, the software program providing computer-generated and displayed graphical user interfaces (GUIs);

connecting an electronics interface to said computer, and further connecting a lead system by a connector to said electronic interface;

applying a plurality of electrodes, said electrodes being a part of said lead system, to a patient upon whom a diagnostic test to determine susceptibility to arrythmia is to be performed;

selecting, from a drop-down menu of said computer-generated GUI, a command to perform a test sequence;

selecting, from a further computer-generated GUI, an existing patient profile or a new patient profile;

configuring, from a subsequent computer-generated GUI, patient information, subpacing pulse configuration, test duration, sensitivity, and deviation limit;

observing, in real time, resulting QRS complex events;

biasing, by delivering a subpacing current to the cardiac tissue of the patient, to effect a QRS complex event at a predetermined time, said predetermined time being determined by the software program; and

analyzing the resultant data, with assistance of the software program, to determine the patient'"'"'s susceptibility to arrhythmia.

38. A method for detecting patient susceptibility to arrhythmias, using a computer and a computer display, the method comprising:

installing on said computer a diagnostic software program comprising data files and application programs, the software program providing computer-generated and displayed graphical user interfaces (GUIs);

connecting an electronics interface to said computer, and further connecting a lead system by a connector to said electronic interface;

applying a plurality of electrodes, said electrodes being a part of said lead system, to a patient upon whom a diagnostic test to determine susceptibility to arrythmia is to be performed;

biasing, by delivering a subpacing current to the cardiac tissue of the patient, to effect a QRS complex event at a predetermined time, said predetermined time being determined by the software program;

determining the presentation of the acquired data by selecting features available from the computer-generated GUI;

filtering the acquired data by selecting features available from the computer-generated GUI;

observing the acquired data by selecting features available from the computer-generated GUI;

manipulating the acquired data by selecting features available from the computer-generated GUI;

simulating the acquired data by selecting features available from the computer-generated GUI;

displaying a graph of the average of the acquired data on the computer-generated GUI;

displaying a biased average of the acquired data on the computer-generated GUI; and

graphing the difference between a biased and an unbiased QRS complex average on the computer-generated GUI;

analyzing the resultant data, with assistance of the software program, to determine the patient'"'"'s susceptibility to arrhythmia.

39. A method for detecting patient susceptibility to arrhythmias, using a computer and a computer display, the method comprising:

installing on said computer a diagnostic software program comprising data files and application programs, the software program providing computer-generated and displayed graphical user interfaces (GUIs);

connecting an electronics interface to said computer, and further connecting a lead system by a connector to said electronic interface;

applying a plurality of electrodes, said electrodes being a part of said lead system, to a patient upon whom a diagnostic test to determine susceptibility to arrythmia is to be performed;

biasing, by delivering a subpacing current to the cardiac tissue of the patient, to effect a QRS complex event at a predetermined time, said predetermined time being determined by the software program;

analyzing the resultant data, with assistance of the software program, to determine the patient'"'"'s susceptibility to arrhythmia;

saving the acquired data to an internal disk by selecting features available from the computer-generated GUI;

saving the acquired data to an external disk by selecting features available from the computer-generated GUI;

retrieving data from an external disk by selecting features available from the computer-generated GUI;

saving protocol steps for future use by selecting features available from the computer-generated GUI; and

retrieving selected protocols from past use by selecting features available from the computer-generated GUI.