Discrimination of supraventricular tachycardia and ventricular tachycardia events

• US 20020032469A1
• Filed: 11/21/2001
• Published: 03/14/2002
• Est. Priority Date: 03/12/1999
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Marcovecchio, Alan F.
• Granted Patent: US 6,687,540 B2
• Time in Patent Office: Days
• US Class Current: 607/5
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion

Abstract

A method and system for discrimination of supraventricular tachycardia and ventricular tachycardia events. Morphological features points are extracted from normal sinus rhythm (NSR) complexes and used to generate a NSR template. A numerical convolution is performed using the NSR template and the feature points for each sensed NSR to give a NSR filter output. Using a plurality of NSR complexes, a median NSR filter output template is determined, where the median NSR filter output template has a median value for each value in the NSR filter output. The median NSR filter output template is then used during a tachycardia event to distinguish tachycardia events as either ventricular tachycardia events or supraventricular tachycardia events.

Claims

1. A method comprising:

for a normal sinus rhythm (NSR) complex, sampling a NSR QRS-complex;

locating a plurality of feature points on the NSR QRS-complex based on morphological features of the NSR QRS-complex;

for a plurality of the NSR complexes, determining a NSR template, where the NSR template includes a median value for each of the plurality of feature points;

performing a numerical convolution of the NSR template and the plurality of feature points for each of the plurality of the NSR complexes to give a NSR filter output;

for the plurality of the NSR complexes, determining a median NSR filter output template, where the median NSR filter output template has a median value for each value in the NSR filter output;

during a tachycardia event, sampling a QRS-complex from a tachycardia complex;

locating the plurality of feature points on the QRS-complex from the tachycardia complex based on morphological features of the QRS-complex;

performing a numerical convolution of the NSR template with the plurality of feature points on the QRS-complex from the tachycardia complex to give a tachycardia complex output; and

summing a numerical difference between the values of the tachycardia complex output and the median NSR filter output template.

2. The method of claim 1, including classifying the tachycardiac complex as a ventricular tachycardia complex when the sum of the difference between the values of the tachycardia complex output and the median NSR filter output template is greater than or equal to a sum of residual threshold value.

3. The method of claim 2, including classifying the cardiac complex as a supraventricular tachycardia complex when the absolute value of the difference between the values of the tachycardia complex output and the median NSR filter output template is less than the sum of residual threshold value.

4. The method of claim 3, including sampling a plurality of tachycardiac complexes, classifying each of the plurality of tachycardiac complexes as either a ventricular tachycardia complex or a supraventricular tachycardia complex, and determining whether the number of ventricular tachycardia complexes exceeded a predetermined threshold value.

5. The method of claim 4, including declaring ventricular tachycardia event when the number of ventricular tachycardia complexes exceeded a predetermined threshold value.

6. The method of claim 5, including providing a signal to a cardioversion/defibrillation output circuit to deliver ventricular tachycardia therapy to a heart when a ventricular tachycardia event is declared.

7. The method of claim 4, including declaring supraventricular tachycardia event when the number of supraventricular tachycardia complexes exceeded a predetermined threshold value.

8. The method of claim 7, including providing a signal to a cardioversion/defibrillation output circuit to deliver supraventricular tachycardia therapy to a heart when a supraventricular tachycardia event is declared.

9. The method of claim 1, where summing a numerical difference includes summing an absolute value of the difference between the values of the tachycardia complex output and the median NSR filter output template.

10. A system comprising:

an endocardial lead including at least one defibrillation coil electrode and at least one pacing electrode; and

an implantable cardioverter defibrillator, where the endocardial lead is physically and electrically coupled to the implantable cardioverter defibrillator and where the implantable cardioverter defibrillator includes;

input circuitry electrically coupled to the at least one defibrillation coil electrode and the at least one pacing electrode,

a signal morphology analyzing circuit coupled to the input circuitry where the signal morphology analyzing circuitry extracts a plurality of feature points from the sensed cardiac complexes,

a template generating circuit coupled to the signal morphology analyzing circuit to generate a normal sinus rhythm template for sensed normal sinus rhythm complexes, where the normal sinus rhythm template includes a median value for each of the plurality of feature points;

a filter output response circuit coupled to the template generating circuit to create a normal sinus rhythm filter output from a numerical convolution of the NSR template and the plurality of feature points for each of the plurality of the NSR complexes, and to determine a median normal sinus rhythm output template from the plurality of normal sinus rhythm complexes, where the median NSR filter output template has a median value for each value in the NSR filter output; and

when, during a tachycardia event, the input circuitry electrically coupled to the at least one defibrillation coil electrode and the at least one pacing electrode receive a QRS-complex from a tachycardia complex, the signal morphology analyzing circuit locates the plurality of feature points on the QRS-complex based on morphological features of the QRS-complex, the filter output response circuit performs a numerical convolution of the NSR template with the plurality of feature points on the QRS-complex to give a tachycardia complex output and sums a numerical difference between the values of the tachycardia complex output and the median NSR filter output template.

11. The system of claim 10, where the implantable cardioverter defibrillator includes a microprocessor which receives the sum of the numerical difference from the filter output response circuit and classifies the tachycardiac complex as a ventricular tachycardia complex when the sum of the difference is greater than or equal to a sum of residual threshold value.

12. The system of claim 11, where the microprocessor classifies the tachycardia complex as a supraventricular tachycardia complex when the sum of the difference is less than the sum of residual threshold value.

13. The system of claim 12, where the microprocessor declares a ventricular tachycardia when the number of ventricular tachycardia complexes exceeded a predetermined threshold value.

14. The system of claim 13, where the implantable medical device includes a cardioversion/defibrillation output circuit, and the microprocessor provides a signal to the cardioversion/defibrillation output circuit to deliver ventricular tachycardia therapy to a heart when a ventricular tachycardia event is declared.

15. The system of claim 13, where the microprocessor provides a signal to the cardioversion/defibrillation output circuit to deliver supraventricular tachycardia therapy to a heart when a supraventricular tachycardia event is declared.

17. The system of claim 16, wherein the microprocessor is adapted for declaring a ventricular tachycardia event if the number of ventricular tachycardia complexes exceeds a predetermined threshold value.

18. The system of claim 16, wherein the microprocessor is adapted for declaring a supraventricular tachycardia event if the number of supraventricular tachycardia complexes exceeds a predetermined threshold value.

19. The system of claim 16, wherein the filter output response circuit is adapted for convolving the plurality of feature points with the NSR template.

20. The system of claim 16, wherein the input circuit is adapted for receiving a rate signal, and wherein the system further includes an R-wave detector coupled to the input circuit for receiving the rate signal and conveying cardiac rate information to the microprocessor.

21. The system of claim 16, further including an output circuit coupled to the microprocessor, wherein the output circuit is adapted for being coupled to the endocardial lead and for delivering cardioversion and defibrillation therapy through the endocardial lead.

16. A system, comprising:

an input circuit adapted for receiving a cardiac complex from an endocardial lead;

a morphology analyzing circuit coupled to the input circuit for extracting a plurality of feature points from the cardiac complex;

a template generating circuit coupled to the morphology analyzing circuit for receiving the plurality of feature points and for generating a normal sinus rhythm (NSR) template from a plurality of normal feature points extracted from NSR cardiac complexes;

a filter output response circuit for receiving the NSR template and the plurality of feature points, and for generating a NSR filter output from the NSR template and the plurality of feature points; and

a microprocessor coupled to the filter output response circuit, the microprocessor being adapted for classifying the cardiac complex as a ventricular tachycardia complex or a supraventricular tachycardia complex.

22. A system, comprising:

an endocardial lead having at least one pacing electrode and at least one defibrillation electrode;

an input circuit coupled to the endocardial lead for receiving cardiac complexes;

an R-wave detector coupled to the input circuit for conveying cardiac rate information to the microprocessor;

a morphology analyzing circuit coupled to the input circuit for extracting a plurality of feature points from cardiac complexes, including a plurality of normal feature points from at least one normal sinus rhythm (NSR) cardiac complex;

a template generating circuit coupled to the morphology analyzing circuit for generating an NSR template from the plurality of normal feature points;

a filter output response circuit for receiving the NSR template from the template generating circuit and the plurality of feature points from the morphology analyzing circuit, and for generating a NSR filter output from the NSR template and the plurality of feature points;

a microprocessor coupled to the filter output response circuit, the microprocessor being adapted for classifying the cardiac complex as a ventricular tachycardia complex or a supraventricular tachycardia complex; and

an output circuit coupled to the microprocessor and to the endocardial lead for delivering cardioversion and defibrillation therapy through the endocardial lead.

23. The system of claim 22, wherein the input circuit includes:

a first amp having an input coupled to the at least one pacing electrode and an output coupled to the R-wave detector; and

a second amp having an input coupled to the at least one defibrillation electrode and an output coupled to the morphology analyzer.

24. The system of claim 22, wherein the microprocessor is adapted for declaring a ventricular tachycardia event if the number of ventricular tachycardia complexes exceeds a predetermined threshold value.

25. The system of claim 22, wherein the microprocessor is adapted for declaring a supraventricular tachycardia event if the number of supraventricular tachycardia complexes exceeds a predetermined threshold value.

26. The system of claim 22, wherein the filter output response circuit is adapted for convolving the plurality of feature points with the NSR template to provide a tachycardia complex output to the microprocessor.

27. The system of claim 26, wherein the filter output response is adapted for determining a median normal sinus rhythm output template from the at least one normal sinus rhythm (NSR) cardiac complex, and for summing a numerical difference between the tachycardia complex output and the median NSR filter output template.

28. The system of claim 27, wherein the microprocessor receives the numerical difference and compares the numerical difference to a predetermined sum of residual threshold value and classifies the cardiac complexes as a ventricular tachycardia complex or a supraventricular complex.

29. The system of claim 28, wherein the microprocessor is adapted for declaring a supraventricular tachycardia event if the number of supraventricular tachycardia complexes exceeds a predetermined threshold value, and for providing a signal to the cardioversion/defibrillation output circuit to deliver supraventricular tachycardia therapy if the microprocessor declares a supraventricular tachycardia event.