Method and apparatus for intracardiac electrogram morphologic analysis

• US 5,351,696 A
• Filed: 04/23/1993
• Issued: 10/04/1994
• Est. Priority Date: 04/23/1993
• Status: Expired due to Fees

• Current Assignee: Reed A. Duthler
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: McDonald, Ray S., German, Michael J., Riff, Kenneth M.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US08/052,359
• Time in Patent Office: 529 Days
• Field of Search: 607/9, 128/702-705, 128/695-696
• US Class Current: 600/515
• CPC Class Codes: A61N 1/371 Capture, i.e. successful stimulation

Abstract

A method and apparatus for morphologic analysis of an electrical signal, implementable in an implantable device such as a pacemaker, cardioverter, defibrillator or the like. The morphologic analysis uses a phase plane representation of the signal, where the signal and its first derivative are plotted along orthogonal axes. A magnitude signal corresponding to the magnitude component of the trajectory of the phase plane representation is generated and applied to a comparator. The comparator produces an activation signal when the magnitude signal exceeds a predetermined threshold. In response to the activation signal, a quadrant detector selectively applies the magnitude signal to one of four integrators, the selection of one integrator over the others being based at all times upon which quadrant of the phase plane the trajectory is in. When the magnitude decreases below a predetermined threshold, the activation signal is deasserted, whereupon the respective outputs from the four integrators may be interpreted as reflecting of the trajectory of the phase plane representation of the signal. In operation, a particular cardiac event to be detected is induced in a patient, and the resultant phase plane signals are examined to determine particular aspects of the phase plane signals which can be used as an indication that the particular event has occurred. The apparatus is then conditioned to recognize such aspects in subsequent phase plane signals, in order to provide an indication when such aspects are again present in the signals.

Claims

1. A method of identifying a cardiac event as being of a specific type, comprising the steps of:

monitoring a patient'"'"'s EGM signal during a cardiac event;

generating a four quadrant phase plane trajectory representation of said patient'"'"'s EGM signal during said event;

defining a metric reflecting the relative areas circumscribed by said phase plane trajectory in each said quadrant; and

identifying said event as being of said specific type in response to said phase plane trajectory corresponding to said metric;

wherein said generating step comprises;

applying said patient'"'"'s EGM signal to a filter circuit and to a differentiator circuit to produce a filtered EGM signal and a differentiated EGM signal;

applying said filtered EGM signal to a squaring circuit to produce a filtered, squared signal;

applying said differentiated EGM signal to a squaring circuit to produce a squared, differentiated EGM signal;

summing said squared, differentiated EGM signal and said filtered, squared EGM signal to produce a summation signal;

applying said summation signal to a square root circuit to produce a magnitude signal corresponding to a magnitude component of said phase plane trajectory representation of said patient'"'"'s EGM signal;

defining said four quadrants of said phase plane trajectory representation;

for each said quadrant, separately integrating said magnitude signal to produce a separate integration signal for each said quadrant; and

wherein said identifying step comprises indicating occurrence of an event of said specific type when said integration signals correlate in accordance with said metric.

2. A method for indicating occurrences of a specific type of cardiac event comprising the steps of defining at least one characteristic feature of a patient'"'"'s EGM signal when said specific type of event occurs and thereafter detecting said at least one characteristic feature of said patient'"'"'s EGM signal;

wherein said step of defining said at least one characteristic feature comprises

defining a metric expressing a correlation of four areas circumscribed by a four quadrant phase plane trajectory;

and wherein said step of detecting said at least one characteristic feature comprises the sub-steps of;

monitoring said patient'"'"'s EGM signal during a cardiac event;

generating a phase plane representation of said EGM signal, said phase plane representation comprising trajectory in a phase plane having four quadrants, said generating step in turn comprising deriving, from said patient'"'"'s EGM signal, four integration signals, each one of said four integration signals reflecting an area circumscribed by said phase plane trajectory in one said quadrant of said phase plane representation of said EGM signal; and

indicating an occurrence of an event of said specific type when said four integration signals correlate in accordance with said metric.

3. An apparatus for detecting occurrences of a specific type of cardiac event, comprising:

a magnitude signal generating circuit means, responsive to an EGM signal from a patient'"'"'s heart for generating a magnitude signal corresponding to a phase plane trajectory representation of said EGM signal, said phase plane trajectory representation corresponding to a plot of said EGM signal versus a first derivative of said EGM signal in a phase plane having four quadrants;

first, second, third, and fourth integrator circuits, each associated with a different one of said four phase plane quadrants, each coupled to said magnitude generating circuit, each integrator circuits comprising means for producing an integration signal corresponding to an area circumscribed by said phase plane trajectory in its associated quadrant of said phase plane;

a discriminating circuit, coupled to said first, second, third, and fourth integrator circuits and comprising means responsive to receipt of first, second, third, and fourth integration signals having a predetermined correlation for producing produce an event detected signal indicative of occurrence of a cardiac event of said specific type, wherein said predetermined correlation is predetermined based upon analysis of an said patient'"'"'s EGM signal during an induced occurrence of said specific event.

4. A method of identifying a cardiac event, comprising the steps of:

applying a patient'"'"'s EGM signal to an amplifier circuit and to a differentiator circuit to produce an amplified EGM signal and a differentiated EGM signal;

applying said amplified EGM signal to a squaring circuit to produce a squared, amplified EGM signal;

applying said differentiated EGM signal to a squaring circuit to produce a squared, differentiated EGM signal;

summing said squared, differentiated EGM signal and said squared, amplified EGM signal to produce a summation signal;

applying said summation signal to a square root circuit to produce a magnitude signal;

separately integrating said magnitude signal (a) while said differentiated EGM signal is positive and said amplified EGM signal is positive, (b) while said differentiated EGM signal is negative and said amplified EGM signal is positive, (c) while said differentiated EGM signal is positive and said amplified EGM signal is negative, and (d) while said differentiated EGM signal is negative and said amplified EGM signal is negative, to produce four separate integration signals; and

identifying said event as a function of relative magnitudes of said integration signals.

5. A method of identifying a cardiac event, comprising the steps of:

applying a patient'"'"'s EGM signal to an amplifier circuit and to a differentiator circuit to produce an amplified EGM signal and a differentiated EGM signal;

combining said amplified EGM signal and said differentiated EGM signal to produce a magnitude signal;

separately integrating said magnitude signal (a) while said differentiated EGM signal is positive and said amplified EGM signal is positive, (b) while said differentiated EGM signal is negative and said amplified EGM signal is positive, (c) while said differentiated EGM signal is positive and said amplified EGM signal is negative, and (d) while said differentiated EGM signal is negative and said amplified EGM signal is negative, to produce four separate integration signals; and

identifying said event as a function of relative magnitudes of said integration signals.

6. A method of identifying a cardiac event, comprising the steps of:

applying a patient'"'"'s EGM signal to an amplifier circuit and to a differentiator circuit to produce an amplified EGM signal and a differentiated EGM signal;

applying said amplified EGM signal to a squaring circuit to produce a squared, amplified EGM signal;

applying said differentiated EGM signal to a squaring circuit to produce a squared, differentiated EGM signal;

summing said squared, differentiated EGM signal and said squared, amplified EGM signal to produce a summation signal;

applying said summation signal to a square root circuit to produce a magnitude signal;

separately integrating said magnitude signal while said differentiated EGM signal meets a first predefined criterion and said amplified EGM meets a second predefined criterion to produce an integration signal; and

identifying said event as a function of magnitude of said integration signal.

7. A method of identifying a cardiac event, comprising the steps of:

applying a patient'"'"'s EGM signal to an amplifier circuit and to a differentiator circuit to produce an amplified EGM signal and a differentiated EGM signal;

combining said amplified EGM signal and said differentiated EGM signal to produce a magnitude signal;

separately integrating said magnitude signal while said differentiated EGM signal meets a first predefined criterion and said amplified EGM signal meets a second predefined criterion to produce an integration signal; and

identifying said event as a function of magnitude of said integration signal.

8. Apparatus for identifying a cardiac event, comprising:

means for sensing a patient'"'"'s EGM signal;

amplifier means, coupled to said sensing means, for producing an amplified EGM signal;

differentiator means, coupled to said sensing means, for producing a differentiated EGM signal;

first squaring means, coupled to said filter means, for producing a filtered, squared signal;

second squaring means, coupled to said differentiator means, for producing a squared, differentiated EGM signal;

summing means, coupled to said first and second squaring means, for summing said squared, differentiated EGM signal and said filtered, squared EGM signal to produce a summation signal;

square root determining means, coupled to said summing means, for producing a magnitude signal;

means for separately integrating said magnitude signal (a) while said differentiated EGM signal is positive and said amplified EGM signal is positive, (b) while said differentiated EGM signal is negative and said amplified EGM signal is positive, (c) while said differentiated EGM signal is positive and said amplified EGM signal is negative, and (d) while said differentiated EGM signal is negative and said amplified EGM signal is negative, to produce four separate integration signals; and

means for identifying said event as a function of relative magnitudes of said integration signals.

9. Apparatus for identifying a cardiac event, comprising:

means for sensing a patient'"'"'s EGM signal;

amplifier means, coupled to said sensing means, for producing an amplified EGM signal;

differentiator means, coupled to said sensing means, for producing a differentiated EGM signal;

means for combining said amplified and differentiated EGM signals to produce a magnitude signal;

means for separately integrating said magnitude signal (a) while said differentiated EGM signal is positive and said amplified EGM signal is positive, (b) while said differentiated EGM signal is negative and said amplified EGM signal is positive, (c) while said differentiated EGM signal is positive and said amplified EGM signal is negative, and (d) while said differentiated EGM signal is negative and said amplified EGM signal is negative, to produce four separate integration signals; and

means for identifying said event as a function of relative magnitudes of said integration signals.

10. Apparatus for identifying a cardiac event, comprising:

means for sensing a patient'"'"'s EGM signal;

amplifier means, coupled to said sensing means, for producing an amplified EGM signal;

differentiator means, coupled to said sensing means, for producing a differentiated EGM signal;

first squaring means, coupled to said filter means, for producing a filtered, squared signal;

second squaring means, coupled to said differentiator means, for producing a squared, differentiated EGM signal;

summing means, coupled to said first and second squaring means, for summing said squared, differentiated EGM signal and said filtered, squared EGM signal to produce a summation signal;

square root determining means, coupled to said summing means, for producing a magnitude signal;

means for separately integrating said magnitude signal while said differentiated EGM signal meets a first predefined criterion and said amplified EGM signal meets a second predefined criterion to produce an integration signal; and

means for identifying said event as a function of magnitude of said integration signal.

11. Apparatus for identifying a cardiac event, comprising:

means for sensing a patient'"'"'s EGM signal;

amplifier means, coupled to said sensing means, for producing an amplified EGM signal;

differentiator means, coupled to said sensing means, for producing a differentiated EGM signal;

means for combining said amplified and differentiated EGM signals to produce a magnitude signal;

means for separately integrating said magnitude signal while said differentiated EGM signal meets a first predefined criterion and said amplified EGM signal meets a second predefined criterion to produce an integration signal; and

means for identifying said event as a function of magnitude of said integration signal.