Method and apparatus for discriminating between tachyarrhythmias

• US 6,760,615 B2
• Filed: 10/31/2001
• Issued: 07/06/2004
• Est. Priority Date: 10/31/2001
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Ferek-Petric, Bozidar
• Primary Examiner(s): Layno, Carl
• Application Number:
  US09/999,890
• Publication Number:
  US 20030083586A1
• Time in Patent Office: 979 Days
• Field of Search: 607/9, 607/14, 607/25, 600/509, 600/512, 600/515-518
• US Class Current: 600/518
• CPC Class Codes: A61B 5/341 Vectorcardiography [VCG]
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia

Abstract

Implantable medical devices (IMDs) are adapted for developing a vectorcardiograph (VCG) from signals across pairs of electrodes. Sense amplifiers of the IMD are calibrated to correlate the signals to reference sagittal, horizontal and frontal planes of the body. Polar coordinate data is plotted over the time of occurrence of the sensed PQRST electrogram as at least one of an x-axis vector projected into the reference sagittal plane as a sagittal VCG, a y-axis vector projected into the reference horizontal plane as a horizontal VCG, a z-axis vector projected into the reference frontal plane as a frontal VCG, and an xyz-vector in 3-D space. The VCG loops plotted by each of the vectors can also be derived. Thresholding and template matching techniques determine one or more of the maximum vector magnitude and orientation, average axis vector magnitude and orientation, the loop shape, and the loop area representing a particular heart rhythm.

Claims

1. Within an implantable medical device, a method of confirming a ventricular tachycardia sense event declared when the apparent ventricular heart rate exceeds a tachycardia rate comprising:

sensing the PQRST electrogram of the heart across an internal lead vector defined by a pair of vectorcardiogram sense electrodes implanted in the body and defining an internal lead vector in the body having a vector orientation in relation to reference sagittal, horizontal, and frontal planes of the body;

declaring a ventricular tachycardia sense event when a feature of the PQRST electrogram satisfies ventricular sense event detection criteria chracteristic of an R-wave, and is therefore an apparent R-wave, and the interval between successive ventricular sense events satisfies tachycardia rate criteria;

deriving a QRS vectorcardiogram of the QRS segment of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the QRS wave;

deriving a T-wave vectorcardiogram of the T-wave of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the T-wave;

determining that the apparent R-wave is a true depolarization R-wave or a re-polarization T-wave satisfying the sense event detection criteria from characteristic features of one or both of the derived QRS vectorcardiogram and T-wave vectorcardiogram; and

confirming the declaration of the ventricular tachycardia sense, event when the apparent R-wave is determine to be a true depolarization R-wave,

wherein the determining stop comprises comparing a feature of the T-wave vectorcardiogram to a reference T-wave vectorcardiogram.

2. Within an implantable medical device, a method of confirming a ventricular tachycardia sense event declared when the apparent ventricular heart rate exceeds a tachycardia rate comprising:

sensing the PQRST electrogram of the heart across an internal lead vector defined by a pair of vectorcardiogram sense electrodes implanted in the body and defining an internal lead vector in the body having a vector orientation in relation to reference saqittal, horizontal, and frontal planes of the body;

declaring a ventricular tachycardia sense event when a feature of the PQRST electrogram satisfies ventricular sense event detection criteria characteristic of an R-wave, and is therefore an apparent R-wave, and the interval between successive ventricular sense events satisfies tachycardia rate criteria;

deriving a QRS vectorcardiogram of the QRS segment of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the QRS wave;

deriving, a T-wave vectorcardiogram of the T-wave of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the T-wave;

determining that the apparent R-wave is a true depolarization R-wave or a re-polarization T-wave satisfying the sense event detection criteria from characteristic features of one or both of the derived QRS vectorcardiogram and T-wave vectorcardiogram; and

confirming the declaration of the ventricular tachycardia sense event when the apparent R-wave is determine to be a true depolarization R-wave, wherein;

the step of deriving the T-wave vectorcardiogram comprises sampling the T-wave vector magnitude to derive a set of polar coordinates of each sample value;

the determining step comprises deriving a T-wave loop area from the set polar coordinates, comparing the T-wave loop area to a reference T-wave loop area, and declaring the apparent ventricular sense event to not be a true depolarization R-wave when the T-wave loop area exceeds the reference T-wave loop area.

3. Within an implantable medical device, a method of confirming a ventricular tachycardia sense event declared when the apparent ventricular heart rate exceeds a tachycardia rate comprising:

sensing the PQRST electrogram of the heart across an internal lead vector defined by a pair of vectorcardiogram sense electrodes implanted in the body and defining an internal lead vector in the body having a vector orientation in relation to reference sagittal, horizontal, and frontal planes of the body;

declaring a ventricular tachycardia sense event when a feature of the PQRST electrogram satisfies ventricular sense event detection criteria characteristic of an R-wave, and is therefore an apparent R-wave, and the interval between successive ventricular sense events satisfies tachycardia rate criteria;

deriving a QRS vectorcardiogram of the QRS segment of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the QRS wave;

deriving a T-wave vectorcardiogram of the T-wave of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the T-wave;

determining that the apparent R-wave is a true depolarization R-wave or a repolarization T-wave satisfying the sense event detection criteria from characteristic features of one or both of the derived QRS vectorcardiogram and T-wave vectorcardiogram; and

confirming the declaration of the ventricular tachycardia sense event when the apparent R-wave is determine to be a true depolarization R-wave, wherein;

the step of deriving the T-wave vectorcardiogram comprises sampling the T-wave vector magnitude to derive a set of polar coordinates of each sample value;

the determining step comprises deriving a T-wave loop shape from the set of polar coordinates, comparing the T-wave loop shape to a reference T-wave loop shape, and declaring the apparent ventricular sense event to not be a true depolarization R-wave when the T-wave loop shape differs from the reference T-wave loop shape.

4. Within an implantable medical device, a method of confirming a ventricular tachycardia sense event declared when the apparent ventricular heart rate exceeds a tachycardia rate comprising:

sensing the PQRST electrogram of the heart across an internal lead vector defined by a pair of vectorcardiogram sense electrodes implanted in the body and defining an internal lead vector in the body having a vector orientation in relation to reference sagittal, horizontal, and frontal planes of the body;

declaring a ventricular tachycardia sense event when a feature of the PQRST electrogram satisfies ventricular sense event detection criteria characteristic of an R-wave, and is therefore an apparent R-wave, and the interval between successive ventricular sense events satisfies tachycardia rate criteria;

deriving a QRS vectorcardiogram of the QRS segment of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the QRS wave;

deriving a T-wave vectorcardiogram of the T-wave of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the T-wave;

determining that the apparent R-wave is a true depolarization R-wave or a re-polarization T-wave satisfying the sense event detection criteria from characteristic features of one or both of the derived QRS vectorcardiogram and T-wave vectorcardiogram;

confirming the declaration of the ventricular tachycardia sense event when the apparent R-wave is determine to be a true depolarization R-wave; and

further comprising classifying an apparent current tachycardia episode as a predetermined tachycardia or tachyarrhythmia by;

deriving an average axis vector of the QRS vectorcardiogram;

comparing the derived average axis vector to stored average axis vectors of tachycardias and tachyarrhythmias to determine the closest matching case; and

declaring that the current tachycardia episode comprises a predetermined tachycardia or tachyarrhythmia that is the closest matching case.

5. Within an implantable medical device, a method of confirming a ventricular tachycardia sense event declared when the apparent ventricular heart rate exceeds a tachycardia rate comprising:

sensing the PQRST electrogram of the heart across an internal lead vector defined by a pair of vectorcardiogram sense electrodes implanted in the body and defining an internal lead vector in the body having a vector orientation in relation to reference sagittal, horizontal, and frontal planes of the body;

declaring a ventricular tachycardia sense event when a feature of the PQRST electrogram satisfies ventricular sense event detection criteria characteristic of an R-wave and is therefore an apparent R-wave and the interval between successive ventricular sense events satisfies tachycardia rate criteria;

deriving a QRS vectorcardiogram of the QRS segment of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the QRS wave;

deriving a T-wave vectorcardiogram of the T-wave of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the T-wave;

determining that the apparent R-wave is a true depolarization R-wave or a repolarization T-wave satisfying the sense event detection criteria from characteristic features of one or both of the derived QRS vectorcardiogram and T-wave vectorcardiogram;

confirming the declaration of the ventricular tachycardia sense event when the apparent R-wave is determine to be a true depolarization R-wave; and

further comprising classifying an apparent current tachycardia episode as a predetermined tachycardia or tachyarrhythmia by;

determining the maximum axis vector of the QRS vectorcardiogram;

comparing the derived maximum axis vector to stored maximum axis vectors of tachycardias and tachyarrhythmias to determine the closest matching case; and

declaring that the current tachycardia episode comprises a predetermined tachycardia or tachyarrhythmia that is the closest matching case.

6. Within an implantable medical device, apparatus for confirming a ventricular tachycardia sense event declared when the apparent ventricular heart rate exceeds a tachycardia rate comprising:

a pair of vectorcardiogram sense electrodes implanted in the body and means for defining an internal lead vector in the body having a vector orientation in relation to reference sagittal, horizontal, and frontal planes of the body;

means for sensing the PQRST electrogram of the heart across an internal lead vector defined by

means for declaring a ventricular tachycardia sense event when a feature of the PQRST electrogram satisfies ventricular sense event detection criteria characteristic of an R-wave, and is therefore an apparent R-wave, and the interval between successive ventricular sense events satisfies tachycardia rate criteria;

means for deriving a QRS vectorcardiogram of the QRS segment of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the QRS wave;

means for deriving a T-wave vectorcardiogram of the T-wave of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the T-wave;

means for determining that the apparent R-wave is a true depolarization R-wave or a re-polarization T-wave satisfying the sense event detection criteria from characteristic features of one or both of the derived QRS vectorcardiogram and T-wave vectorcardiogram;

means for confirming the declaration of the ventricular tachycardia sense event when the apparent R-wave is determine to be a true depolarization R-wave; and

wherein the determining means comprises means for comparing a feature of the T-wave vectorcardiogram to a reference T-wave vectorcardiogram.

7. Within an implantable medical device, apparatus for confirming a ventricular tachycardia sense event declared when the apparent ventricular heart rate exceeds a tachycardia rate comprising:

a pair of vectorcardiogram sense electrodes implanted in the body and means for defining an internal lead vector in the body having a vector orientation in relation to reference sagittal, horizontal, and frontal planes of the body;

means for sensing the PQRST electrogram of the heart across an internal lead vector defined by

means for declaring a ventricular tachycardia sense event when a feature of the PQRST electrogram satisfies ventricular sense event detection criteria characteristic of an R-wave, and is therefore an apparent R-wave, and the interval between successive ventricular sense events satisfies tachycardia rate criteria;

means for deriving a QRS vectorcardiogram of the QRS segment of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the QRS wave;

means for deriving a T-wave vectorcardiogram of the T-wave of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the T-wave;

means for determining that the apparent R-wave is a true depolarization R-wave or a re-polarization T-wave satisfying the sense event detection criteria from characteristic features of one or both of the derived QRS vectorcardiogram and T-wave vectorcardiogram;

means for confirming the declaration of the ventricular tachycardia sense event when the apparent R-wave is determine to be a true depolarization R-wave, and wherein;

the means for deriving the T-wave vectorcardiogram comprises means for sampling the T-wave vector magnitude to derive a set of polar coordinates of each sample value;

the determining means comprises means for deriving a T-wave loop area from the set of polar coordinates, comparing the T-wave loop area to a reference T-wave loop area, and means for declaring the apparent ventricular sense event to not be a true depolarization R-wave when the T-wave loop area exceeds the reference T-wave loop area.

8. Within an implantable medical device, apparatus for confirming a ventricular tachycardia sense event declared when the apparent ventricular heart rate exceeds a tachycardia rate comprising:

a pair of vectorcardiogram sense electrodes implanted in the body and means for defining an internal lead vector in the body having a vector orientation in relation to reference sagittal, horizontal, and frontal planes of the body;

means for sensing the PQRST electrogram of the heart across an internal lead vector defined by

means for declaring a ventricular tachycardia sense event when a feature of the PQRST electrogram satisfies ventricular sense event detection criteria characteristic of an R-wave, and is therefore an apparent R-wave, and the between successive ventricular sense events satisfies tachycardia rate criteria;

means for deriving a QRS vectorcardiogram of the QRS segment of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the QRS wave;

means for deriving a T-wave vectorcardiogram of the T-wave of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the T-wave;

means for determining that the apparent R-wave is a true depolarization R-wave or a re-polarization T-wave satisfying the sense event detection criteria from characteristic features of one or both of the derived QRS vectorcardiogram and T-wave vectorcardiogram;

means for confirming the declaration of the ventricular tachycardia sense event when the apparent R-wave is determine to be a true depolarization R-wave, and wherein;

the means for deriving the T-wave vectorcardiogram comprises means for sampling the T-wave vector magnitude to derive a set of polar coordinates of sample value;

the determining means comprises means for deriving a T-wave loop shape from the set of polar coordinates, means for comparing the T-wave loop shape to a reference T-wave loop shape, and means for declaring the apparent ventricular sense event to not be a true depolarization R-wave when the T-wave loop shape differs from the reference T-wave loop shape.

9. Within an implantable medical device, apparatus for confirming a ventricular tachycardia sense event declared when the apparent ventricular heart rate exceeds a tachycardia rate comprising:

a pair of vectorcardiogram sense electrodes implanted in the body and means for defining art internal lead vector in the body having a vector orientation in relation to reference sagittal, horizontal, and frontal planes of the body;

means for sensing the PQRST electrogram of the heart across an internal lead vector defined by

means for declaring a ventricular tachycardia sense event when a feature of the PQRST electrogram satisfies ventricular sense event detection criteria characteristic of an R-wave, and is therefore an apparent R-wave, and the interval between successive ventricular sense events satisfies tachycardia rate criteria;

means for deriving a QRS vectorcardiogram of the T-wave of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the QRS wave;

means for deriving a T-wave vectorcardiogram of the T-wave of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the T-wave;

means for determining that the apparent R-wave is a true depolarization R-wave or a re-polarization T-wave satisfying the sense event detection criteria from characteristic features of one or both of the derived QRS vectorcardiogram and T-wave vectorcardiogram; and

means for confirming the declaration of the ventricular tachycardia sense event when the apparent R-wave is determine to be a true depolarization R-wave; and

further comprising means for classifying an apparent current tachycardia episode as a predetermined tachycardia or tachyarrhythmia comprising;

means for deriving an average axis vector of the QRS vectorcardiogram;

means for comparing the derived average axis vector to stored average axis vectors of tachycardias and tachyarrhythmias to determine the closest matching case; and

means for declaring that the current tachycardia episode comprises a predetermined tachycardia or tachyarrhythmia that is the closest matching case.

10. Within an implantable medical device, apparatus for confirming a ventricular tachycardia sense event declared when the apparent ventricular heart rate exceeds a tachycardia rate comprising:

a pair of vectorcardiogram sense electrodes implanted in the body and means for defining an internal lead vector in the body having a vector orientation in relation to reference sagittal, horizontal, and frontal planes of the body;

means for sensing the PQRST electrogram of the heart across an internal lead vector defined by

means for declaring a ventricular tachycardia sense event when a feature of the PQRST electrogram satisfies ventricular sense event detection criteria characteristic of an R-wave, and is therefore an apparent R-wave, and the interval between successive ventricular sense events satisfies tachycardia rate criteria;

means for deriving a QRS vectorcardiogram of the QRS segment of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the QRS wave;

means for deriving a T-wave vectorcardiogram of the T-wave of the sensed QRST electrogram quantifying the orientation and magnitude of the vector of the T-wave;

means for determining that the apparent R-wave is a true depolarization R-wave or a re-polarization T-wave satisfying the sense event detection criteria from characteristic features of one or both of the derived QRS vectorcardiogram and T-wave vectorcardiogram;

means for confirming the declaration of the ventricular tachycardia sense event when the apparent R-wave is determine to be a true depolarization R-wave; and

further comprising means for classifying an apparent current tachycardia episode as a predetermined tachycardia or tachyarrhythmia comprising;

means for determining the maximum axis vector of the QRS vectorcardiogram;

means for comparing the derived maximum axis vector to stored maximum axis vectors of tachycardias and tachyarrhythmias to determine the closest matching case; and

means for declaring that the current tachycardia episode comprises a predetermined tachycardia or tachyarrhythmia that is the closest matching case.