Method for automatic, adaptive, active facilitation to access myocardial electrical instability

• US 5,555,888 A
• Filed: 02/27/1995
• Issued: 09/17/1996
• Est. Priority Date: 02/27/1995
• Status: Expired due to Term

• Current Assignee: Harbinger Medical, Inc.
• Original Assignee: Clontz Corporation
• Inventors: Brewer, James E., Taghizadeh, Ehssanollah
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): Getzow, Scott M.
• Application Number:
  US08/395,048
• Time in Patent Office: 568 Days
• Field of Search: 128/705, 128/702, 128/696
• US Class Current: 600/515
• 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: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371

Abstract

A method and apparatus continuously, automatically, and adaptively facilitate the electrical activity of a patient'"'"'s heart by pulsing the heart with current. The method and apparatus further continuously, automatically, and adaptively monitor the resulting electrical activity of the patient'"'"'s heart to assess the patient'"'"'s likelihood for myocardial electrical instability. The method comprises the steps of injecting current across the patient'"'"'s heart, monitoring the patient'"'"'s electrocardiogram for the effects of these current pulses, and adapting the current pulses continuously and automatically to maximize the effects, thereby assessing a patient'"'"'s likelihood of sudden cardiac death.

Claims

1. A method for assessing a patient'"'"'s myocardial electrical instability, comprising the steps of:

(a) injecting a plurality of electromagnetic energy pulses into said patient'"'"'s body;

(b) monitoring a plurality of electrocardiographic signals from said patient;

(c) recording changes in said electrocardiographic signals caused by said injecting of said electromagnetic energy pulses; and

(d) nonlinearly optimizing said injecting of said electromagnetic energy pulses automatically to maximize said recorded changes, whereby said myocardial electrical instability is assessed.

2. The method of claim 1, wherein said monitoring further comprises the step of filtering said electrocardiographic signals with a state-variable active filter cascaded in a plurality of low-pass filter sections, high-pass filter sections, and notch filter sections.

3. The method of claim 2, wherein said low-pass filter sections have adjustable filtering characteristics and are controlled by a microcontroller and wherein said high-pass filter sections have adjustable filtering characteristics and are controlled by said microcontroller, whereby said microcontroller adjusts said filtering characteristics in real-time.

4. The method of claim 1, wherein said injecting is controlled by a first microcontroller, wherein said monitoring is controlled by a second microcontroller, and further comprising the step of switching between said injecting and said monitoring with a third microcontroller, whereby said steps of injecting and monitoring operate synchronously and in parallel.

5. The method of claim 4, wherein said microcontrollers comprise a plurality of high-performance, programmable, microcontroller integrated circuits coupled in a master-slave arrangement and controlled by a master data clock.

6. The method of claim 1, wherein said monitoring further comprise the steps of:

(a) continuously injecting a very high-frequency, high-impedance current source separate from said injecting of said electromagnetic energy pulses;

(b) continuously monitoring voltage levels derived from said injecting of said high-impedance current source; and

(c) signaling an alarm when said voltage levels exceed a predetermined threshold, whereby a failure of an electrocardiograph wire or an electrode is detected.

7. The method of claim 1, wherein said nonlinearly optimizing comprises the steps of a simplex method.

8. The method of claim 1, wherein said nonlinearly optimizing comprises the steps of a direction-set method.

9. The method of claim 1, wherein said nonlinearly optimizing comprises the steps of a conjugate gradient method.

10. The method of claim 1, wherein said nonlinearly optimizing comprises the steps of a variable metric method.

11. The method of claim 1, wherein said recording changes in said plurality of electrocardiographic signals comprises the steps of:

(a) collecting said recorded changes into an electrical instability waveform; and

(b) analyzing said electrical instability waveform, whereby an electrical instability index is formed.

12. The method of claim 11, wherein said collecting said recorded changes comprises the steps of:

(a) extracting and time-wise aligning a plurality of cardiac cycles from said electrocardiographic signals;

(b) computing a square of an algebraic difference between temporally-adjacent pairs of said cardiac cycles; and

(c) averaging said square of algebraic differences, whereby an electrical instability waveform is formed.

13. The method of claim 11, wherein said analyzing said electrical instability waveform comprises the steps of:

(a) summing said electrical instability waveform;

(b) computing a peak to peak amplitude assessment of said plurality of electrocardiographic signals; and

(c) normalizing said summation of said electrical instability waveform by said peak to peak amplitude assessment.

14. The method of claim 13, wherein said summing said electrical instability waveform comprises the steps of:

(a) computing a baseline of said electrical instability waveform;

(b) subtracting said baseline from said electrical instability waveform to form a facilitated electrical instability waveform; and

(c) summing values of said facilitated electrical instability waveform.

15. The method of claim 1, further comprising the steps of, prior to said step of injecting, monitoring a plurality of natural electrocardiographic signals from said patient and recording a plurality of natural changes in said natural electrocardiographic signals, said changes recorded via said step of recording changes in said electrocardiographic signals caused by said injecting of said electromagnetic energy pulses being facilitated changes, the method further comprising the step of removing said natural changes from said facilitated changes, whereby confounding effects of naturally occurring physiological variations are removed from said assessment of myocardial electrical instability.

16. A method for assessing a patient'"'"'s myocardial electrical instability, comprising the steps of:

(a) precisely regulating a programmable, digitally controlled, current source to inject electromagnetic energy pulses into said patient'"'"'s body;

(b) acquiring a plurality of high-fidelity electrocardiographic signals from said patient to monitor said injecting of said electromagnetic energy pulses;

(c) recording changes in said electrocardiographic signals caused by said injecting of said electromagnetic energy pulses;

(d) collecting said recorded changes into an electrical instability waveform;

(e) integrating said electrical instability waveform to form an electrical instability index; and

(f) adapting said injecting of said electromagnetic energy pulses automatically to maximize said electrical instability index, whereby said myocardial electrical instability is assessed.

17. A method for assessing a patient'"'"'s myocardial electrical instability, comprising the steps of:

(a) precisely regulating a programmable, digitally controlled, current source to inject electromagnetic energy pulses into said patient'"'"'s body;

(b) acquiring a plurality of high-fidelity electrocardiographic signals from said patient to monitor said injecting of said electromagnetic energy pulses;

(c) extracting and time-wise aligning a plurality of cardiac cycles from said electrocardiographic signals;

(d) computing a squared algebraic difference between temporally-adjacent pairs of said cardiac cycles;

(e) averaging said squared algebraic differences to form an electrical instability waveform;

(f) computing a baseline of said electrical instability waveform;

(g) subtracting said baseline from said electrical instability waveform to form a facilitated electrical instability waveform;

(h) summing said facilitated electrical instability waveform to form a facilitated electrical instability index; and

(i) nonlinearly optimizing said injecting of said electromagnetic energy pulses automatically to maximize said facilitated electrical instability index, whereby said myocardial electrical instability is assessed.

18. A method for assessing a patient'"'"'s myocardial electrical instability, comprising the steps of:

(a) injecting a plurality of electromagnetic energy pulses into said patient'"'"'s body;

(b) controlling said injecting by a first microcontroller;

(c) monitoring a plurality of electrocardiographic signals from said patient;

(d) controlling said monitoring by a second microcontroller;

(e) switching between said injecting and said monitoring with a third microcontroller, whereby said steps of injecting and monitoring operate synchronously and in parallel;

(f) recording changes in said electrocardiographic signals caused by said injecting of said electromagnetic energy pulses; and

(g) adapting said injecting of said electromagnetic energy pulses automatically to maximize said recorded changes, whereby said myocardial electrical instability is assessed.

19. A method for assessing a patient'"'"'s myocardial electrical instability, comprising the steps of:

(a) injecting a plurality of electromagnetic energy pulses into said patient'"'"'s body;

(b) continuously injecting a very high-frequency, high-impedance current source separate from said injecting of said electromagnetic energy pulses;

(c) monitoring a plurality of electrocardiographic signals from said patient;

(d) continuously monitoring voltage levels derived from said injecting of said high-impedance current source;

(e) signaling an alarm when said voltage levels exceed a predetermined threshold, whereby a failure of an electrocardiograph wire or an electrode is detected;

(f) recording changes in said electrocardiographic signals caused by said injecting of said electromagnetic energy pulses; and

(g) adapting said injecting of said electromagnetic energy pulses automatically to maximize said recorded changes, whereby said myocardial electrical instability is assessed.

20. A method for assessing a patient'"'"'s myocardial electrical instability, comprising the steps of:

(a) precisely regulating a programmable current source to inject a plurality of electromagnetic energy pulses into said patient'"'"'s body;

(b) monitoring a plurality of electrocardiographic signals from said patient;

(c) recording changes in said electrocardiographic signals caused by said injecting of said electromagnetic energy pulses;

(d) collecting said recorded changes into an electrical instability waveform;

(e) analyzing said electrical instability waveform to form an electrical instability index; and

(f) adapting said injecting of said electromagnetic energy pulses automatically to maximize said electrical instability index, whereby said myocardial electrical instability is assessed.

21. A method for assessing a patient'"'"'s myocardial electrical instability, comprising the steps of:

(a) monitoring a plurality of electrocardiographic signals from said patient;

(b) recording a plurality of natural changes in said electrocardiographic signals;

(c) injecting a plurality of electromagnetic energy pulses into said patient'"'"'s body;

(d) monitoring a plurality of electrocardiographic signals from said patient;

(e) recording a plurality of facilitated changes in said electrocardiographic signals caused by said injecting of said electromagnetic energy pulses;

(f) removing said natural changes from said facilitated changes; and

(g) adapting said injecting of said electromagnetic energy pulses automatically to maximize said facilitated changes, whereby said myocardial electrical instability is assessed and confounding effects of naturally occurring physiological variations are removed from said assessment of myocardial electrical instability.