# US 6,438,410 B1 · System and method for a classifying cardiac complexes

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- Number: US 6,438,410 B1
- Document ID: US6438410B1
- Status: Granted
- Kind: B1
- Application number: 09/848,605
- Filed: 2001-05-03
- Published: 2002-02-14
- Granted: 2002-08-20
- Earliest claimed: 1998-02-12
- Assignees: Cardiac Pacemakers, Inc.
- Inventors: William Hsu; Joseph Martin Smith
- Web page: https://patentgrep.com/patent/US6438410B1

## CPC

- A61B 5/35: by template matching
- A61B 5/7264: {Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems}
- A61N 1/3622: {comprising two or more electrodes co-operating with different heart regions}
- A61N 1/3704: {Circuits specially adapted therefor, e.g. for sensitivity control}
- G16H 50/20: for computer-aided diagnosis, e.g. based on medical expert systems
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- A61N: ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY (measurement of bioelectric currents A61B; surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body A61B18/00; anaesthetic apparatus in general A61M; incandescent lamps H01K; infrared radiators for heating H05B)
- G16H: HEALTHCARE INFORMATICS, i.e. INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR THE HANDLING OR PROCESSING OF MEDICAL OR HEALTHCARE DATA

## Abstract

A system and method classify cardiac complexes based on cardiac information derived from two or more cardiac signals. Two or more cardiac signals containing cardiac complexes are monitored. A cardiac complex in the two or more cardiac signals is isolated in an analysis window. The morphology of the cardiac complex in each of the two or more cardiac signals is then compared to the morphology of a template cardiac complex representing a predetermined cardiac condition. Based on this comparison, the cardiac complex is classified as either belonging or not belonging to the predetermined cardiac condition.

## Claims

### Claim 1

A method, comprising:
monitoring a first cardiac signal and a second cardiac signal;
detecting a first cardiac complex in the first cardiac signal and a second cardiac complex in the second cardiac signal, the first and second cardiac complexes associated with the same heart contraction;
creating at least one first template cardiac complex for the first cardiac signal and at least one second template cardiac complex for the second cardiac signal, wherein each of the first and second template cardiac complexes represents a predetermined cardiac rhythm state;
comparing the first cardiac complex to the first template cardiac complex and the second cardiac complex to the second template cardiac complex to determine whether the heart contraction is representative of the predetermined cardiac rhythm state; and
classifying the heart contraction as being representative of the predetermined cardiac rhythm state based on the comparison of the first cardiac complex to the first template cardiac complex and the second cardiac complex to the second template cardiac complex.

### Claim 2 (depends on 1)

The method of claim 1, further comprising determining a therapy at least in part in response to the classification of the heart contraction.

### Claim 3 (depends on 2)

The method of claim 2, furthering comprising delivering, at least in part in response to the classification of the heart contraction, at least one of:
a cardiac pacing therapy;
a cardioversion therapy; and
a defibrillation therapy.

### Claim 4 (depends on 1)

The method of claim 1, wherein the predetermined cardiac rhythm state includes at least one of:
a normal sinus rhythm (NSR);
a ventricular tachycardia (VT);
a supraventricular tachycardia (SVT);
a premature ventricular contraction (PVC); and
an ischemic event.

### Claim 5 (depends on 1)

The method of claim 1, wherein the first and second template cardiac complexes are template morphologies and comparing the first and second cardiac complexes to the corresponding first and second template cardiac complexes comprises comparing morphologies of the first and second cardiac complexes to the respective first and second template morphologies.

### Claim 6 (depends on 5)

The method of claim 5, further comprising deriving the first and second template morphologies from cardiac complexes detected in the first and second cardiac signals, respectively.

### Claim 7 (depends on 6)

The method of claim 6, wherein the first and second template morphologies are each derived from at least one repeatably identifiable feature of cardiac complexes sensed from a patient manifesting at least one of the predetermined cardiac rhythm states.

### Claim 8 (depends on 6)

The method of claim 6, wherein the first and second template morphologies are each derived from at least one repeatably identifiable feature of cardiac complexes sensed from a population of patients manifesting at least one of the predetermined cardiac rhythm states.

### Claim 9 (depends on 5)

The method of claim 5, wherein comparing the morphologies comprises comparing at least one predetermined feature in the first and second cardiac complexes to a corresponding at least one predetermined feature in the corresponding one of the first and second template morphologies.

### Claim 10 (depends on 9)

The method of claim 9, wherein the predetermined feature includes at least one of:
a maximum signal deflection;
a predetermined signal deviation from a baseline; and
a signal return to the baseline for a predetermined time period.

### Claim 11 (depends on 10)

The method of claim 10, further comprising aligning the predetermined feature in the first and second cardiac complexes and the respective first and second morphologies.

### Claim 12 (depends on 11)

The method of claim 11, furthering comprising utilizing a correlation waveform analysis algorithm for comparing the first and second cardiac complexes to the respective first and second morphologies.

### Claim 13

A method, comprising:
monitoring a first cardiac signal and a second cardiac signal;
detecting a first cardiac complex in the first cardiac signal and a second cardiac complex in the second cardiac signal, the first and second cardiac complexes associated with the same heart contraction;
locating at least one first predetermined feature in the first cardiac complex and at least one second predetermined feature in the second cardiac complex;
generating at least one characteristic quantity as a function of a position of at least one of the first and second predetermined features; and
classifying the heart contraction as being representative of a predetermined cardiac rhythm state based at least in part on the characteristic quantity.

### Claim 14 (depends on 13)

The method of claim 13, further comprising determining a therapy at least in part in response to the classification of the heart contraction.

### Claim 15 (depends on 14)

The method of claim 14, furthering comprising delivering, at least in part in response to the classification of the heart contraction, at least one of:
a cardiac pacing therapy;
a cardioversion therapy; and
a defibrillation therapy.

### Claim 16 (depends on 13)

The method of claim 13, wherein the cardiac signals are monitored to provide a substantially simultaneous view of a cardiac complex from at least two different cardiac locations.

### Claim 17 (depends on 13)

The method of claim 13, wherein the predetermined cardiac rhythm state includes at least one of:
a normal sinus rhythm (NSR);
a ventricular tachycardia (VT);
a supraventricular tachycardia (SVT);
a premature ventricular contraction (PVC); and
an ischemic event.

### Claim 18 (depends on 13)

The method of claim 13, wherein at least one of the first and second predetermined features is at least one of:
a maximum signal deflection;
a predetermined signal deviation from a baseline; and
a signal return to the baseline for a predetermined time period.

### Claim 19 (depends on 13)

The method of claim 13, further comprising:
creating at least one classification quantity, wherein the classification quantity represents a predetermined cardiac rhythm state; and
comparing the characteristic quantity to the classification quantity to determine whether the characteristic quantity is representative of the predetermined cardiac rhythm state;
wherein the classifying the heart contraction is based at least in part on the outcome of the comparing the characteristic quantity to the classification quantity.

### Claim 20 (depends on 19)

The method of claim 19, wherein the characteristic quantity comprises a characteristic scalar value, the classification quantity comprises a classification scalar value, and the comparing the characteristic quantity to the classification quantity comprises comparing the characteristic scalar value to the classification scalar value.

### Claim 21 (depends on 20)

The method of claim 20, further comprising deriving the classification scalar value from cardiac complexes detected in the first and second cardiac signals.

### Claim 22 (depends on 19)

The system of claim 19, wherein the characteristic scalar value is representative, at least in part, of at least one of:
a time associated with at least one of the first and second predetermined features;
a time difference between the first and second predetermined features;
an amplitude value of at least one of the first and second predetermined features; and
a time difference between two predetermined features in one cardiac signal.

### Claim 23 (depends on 19)

The method of claim 19, wherein the classification scalar value is population-based.

### Claim 24 (depends on 19)

The method of claim 19, wherein the classification scalar value is individual-based.

### Claim 25 (depends on 19)

The method of claim 19, wherein:
the characteristic quantity is a characteristic vector comprising two or more scalar values;
the classification quantity is a classification vector; and
comparing the characteristic quantity to the classification quantity comprises comparing the characteristic vector to the classification vector.

### Claim 26 (depends on 25)

The method of claim 25, wherein classifying the heart contraction comprises:
determining a correlation between the characteristic vector and the classification vector; and
classifying the cardiac complex as being representative of the predetermined cardiac rhythm state if the correlation exceeds a predetermined threshold.

### Claim 27 (depends on 26)

The method of claim 26, wherein determining the correlation comprises determining a mean square error value between the characteristic vector and the classification vector.

### Claim 28

A system, comprising
an amplifier to sense first and second cardiac signals;
a detector, coupled to the amplifier, to detect first and second cardiac complexes in the respective first and second cardiac signals, the first and second cardiac complexes associated with the same heart contraction;
a morphology analyzer, coupled to the detector, to locate at least one predetermined feature in a morphology of each of the first and second cardiac complexes;
a comparator, coupled to the morphology analyzer, to compare the first and second cardiac complexes with respective first and second template cardiac complexes; and
a processor, coupled to the comparator, to classify the heart contraction.

### Claim 29 (depends on 28)

The system of claim 28, wherein the predetermined feature includes at least one of:
a maximum signal deflection;
a predetermined signal deviation from a baseline; and
a signal return to the baseline for a predetermined time period.

### Claim 30 (depends on 29)

The system of claim 29, wherein the morphology analyzer further comprises at least one scalar value that is representative, at least in part, of at least one of:
a time associated with at least one of the first and second predetermined features;
a time difference between the first and second predetermined features;
an amplitude value of at least one of the first and second predetermined features; and
a time difference between two predetermined features in one cardiac signal.

### Claim 31 (depends on 29)

The system of claim 29, further comprising a template generator, coupled to the comparator, to generate at least one template morphology for each of the first and second cardiac signals, wherein the template morphology represents a predetermined cardiac rhythm state that includes at least one of:
a normal sinus rhythm (NSR);
a ventricular tachycardia (VT);
a supraventricular tachycardia (SVT);
a premature ventricular contraction (PVC); and
an ischemic event.

### Claim 32 (depends on 31)

The system of claim 31, wherein the template generator comprises a characterization vector comprising at least two scalar values.

### Claim 33 (depends on 28)

The system of claim 28, further comprising a cardiac rhythm analyzer, coupled to the amplifier, to analyze at least one of the first and second cardiac signals to detect a predetermined cardiac condition.

### Claim 34 (depends on 33)

The system of claim 33, wherein the cardiac rhythm analyzer comprises a heart rate detector.

### Claim 35 (depends on 28)

The system of claim 28, wherein the comparator includes a correlation waveform analysis algorithm to compare the morphologies of the first and second cardiac complexes with respective first and second template morphologies.

### Claim 36 (depends on 28)

The system of claim 28, wherein the comparator comprises comparing a characteristic quantity to a classification quantity.

### Claim 37 (depends on 36)

The system of claim 36, wherein the comparator comprises comparing a characteristic scalar value to a classification scalar value.

### Claim 38 (depends on 36)

The system of claim 36, wherein the comparator comprises comparing a characteristic vector to a classification vector, wherein the characteristic vector comprises at least two scalar values and the classification vector comprises at least two scalar values.

### Claim 39 (depends on 28)

The system of claim 28, further comprising a therapy delivery circuit, wherein the therapy delivery circuit comprises at least one of:
a pace output circuit; and
a cardioversion and defibrillation output circuit.