TEMPLATE BASED AV/VA INTERVAL COMPARISON FOR THE DISCRIMINATION OF CARDIAC ARRHYTHMIAS

• US 20050256544A1
• Filed: 05/12/2004
• Published: 11/17/2005
• Est. Priority Date: 05/12/2004
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Thompson, Julie
• Granted Patent: US 7,515,956 B2
• Time in Patent Office: Days
• US Class Current: 607/14
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion

Abstract

An implantable cardioverter/defibrillator includes a tachycardia detection system that detects one-to-one (1:1) tachycardia, which is a tachycardia with a one-to-one relationship between atrial and ventricular contractions. When the 1:1 tachycardia is detected, the system discriminates ventricular tachycardia (VT) from supraventricular tachycardia (SVT) based on analysis of a cardiac time interval. Examples of the cardiac time interval include an atrioventricular interval (AVI) and a ventriculoatrial interval (VAI). A template time interval is created during a known normal sinus rhythm. The system measures a tachycardia time interval after detecting the 1:1 tachycardia, and indicates a VT detection if the tachycardia time interval differs from the template time interval by at least a predetermined percentage of the template time interval.

Claims

1. A system for discriminating ventricular tachycardia (VT) from supraventricular tachycardia (SVT), the system comprising:

a sensing circuit to sense an atrial electrogram indicative of atrial depolarizations and a ventricular electrogram indicative of ventricular depolarizations;

a rate detector circuit, coupled to the sensing circuit, to detect an atrial rate based on the atrial electrogram and a ventricular rate based on the ventricular electrogram;

a tachycardia detector circuit, coupled to the rate detector circuit, to detect a tachycardia based on at least one of the atrial rate and the ventricular rate;

a rhythm classifier circuit, coupled to the rate detector circuit and the tachycardia detector circuit, to classify the detected tachycardia as a 1;

1 tachycardia when the atrial rate and the ventricular rate are substantially equal; and

a tachycardia discriminator circuit coupled to the rhythm classifier circuit, the tachycardia discriminator circuit including;

a time interval measurement circuit, coupled to the sensing circuit, to measure a tachycardia time interval between an atrial depolarization and an adjacent ventricular depolarization during the 1;

1 tachycardia; and

a VT comparator circuit coupled to the time interval measurement circuit, the VT comparator circuit having an output adapted to indicate a VT detection when the tachycardia time interval differs from a template time interval by at least a predetermined margin.

2. The system of claim 1, wherein the predetermined margin is a predetermined percentage of the template time interval.

3. The system of claim 2, wherein the output of the VT comparator circuit is adapted to indicate the detection of VT when the tachycardia time interval differs from the template time interval by a predetermined percentage of the template time interval and the detection of SVT when the tachycardia time interval does not differ from the template time interval by the predetermined percentage of the VT template.

4. The system of claim 1, wherein the time interval measurement circuit comprises an atrioventricular interval (AVI) measurement module adapted to measure a tachycardia AVI when the tachycardia is detected and the 1:

1 tachycardia is classified.

5. The system of claim 4, wherein the AVI measurement module is further adapted to measure the template time interval as an AVI during a normal sinus rhythm.

6. The system of claim 1, wherein the time interval measurement circuit comprises a ventriculoatrial interval (VAI) measurement module to measure a tachycardia VAI when the tachycardia is detected and the 1:

1 tachycardia is classified.

7. The system of claim 6, wherein the VAI measurement module is further adapted to measure the template time interval as a VAI during a normal sinus rhythm.

8. The system of claim 1, wherein the output of the VT comparator circuit is adapted to indicate an SVT detection when the tachycardia time interval does not differ from the template time interval by at least the predetermined margin.

9. The system of claim 1, wherein the tachycardia detector circuit comprises a tachycardia comparator circuit having a tachycardia output indicative a detected tachycardia when the ventricular rate exceeds a predetermined tachycardia threshold rate.

10. The system of claim 9, wherein the rhythm classifier circuit comprises a rhythm comparator circuit to compare the atrial rate to the ventricular rate after the tachycardia is detected, the rhythm comparator circuit having an atrial rate input to receive the atrial rate, a ventricular rate input to receive a ventricular rate, and a classification output indicative of VT if the ventricular rate is substantially higher than the atrial rate, SVT or dual arrhythmia if the atrial rate is substantially higher than the ventricular rate, and the 1:

1 tachycardia if the atrial rate and the ventricular rate are substantially equal, wherein the dual arrhythmia includes a combination of SVT and VT.

11. The system of claim 10, further comprising an atrial fibrillation (AF) detector circuit, coupled to the rhythm classifier, to detect AF.

12. The system of claim 11, further comprising an atrial defibrillation circuit, coupled to the AF detector circuit, to deliver one or more atrial defibrillation shocks when AF is detected.

13. The system of claim 10, further comprising a ventricular fibrillation (VF) detector circuit, coupled to the rhythm classifier circuit, to detect VF.

14. The system of claim 13, further comprising a ventricular defibrillation circuit, coupled to the VF detector circuit, to deliver one or more ventricular defibrillation shocks when VF is detected.

15. The system of claim 1, wherein the tachycardia discriminator circuit further comprises a VT verifier circuit, coupled to the VT comparator circuit, to verify the VT detection.

16. The system of claim 15, wherein the VT verifier circuit comprises a further tachycardia discriminator circuit.

17. The system of claim 1, comprising an implantable cardiovertor/defibrillator including a hermetically sealed implantable can to house a cardiovertor/defibrillator circuit including at least the sensing circuit, the rate detector circuit, the tachycardia detector circuit, the rhythm classifier circuit, and the tachycardia discriminator circuit.

39. The method of claim 11, wherein detecting the ventricular rate comprises sensing a ventricular electrogram indicative of ventricular depolarizations, and detecting the atrial rate comprises sensing an atrial electrogram indicative of atrial depolarizations.

40. The method of claim 39, wherein detecting tachycardia comprises comparing the detected ventricular rate to a predetermined tachycardia threshold rate.

41. The method of claim 40, further comprising classifying the tachycardia as VT if the detected ventricular rate is substantially higher than the detected atrial rate.

42. The method of claim 41, further comprising detecting ventricular fibrillation (VF).

43. The method of claim 40, further comprising delivering at least one ventricular defibrillation shock if VF is detected.

44. The method of claim 40, further comprising classifying the tachycardia as SVT or dual arrhythmia if the detected atrial rate is substantially higher than the detected ventricular rate, wherein the dual arrhythmia includes a combination of SVT and VT.

45. The method of claim 44, further comprising detecting atrial fibrillation (AF).

46. The method of claim 45, further comprising delivering at least one atrial defibrillation shock if AF is detected.

18. A cardiac rhythm management (CRM) system, comprising:

an implantable atrial lead allowing for sensing an atrial electrogram indicative of atrial depolarizations;

an implantable ventricular lead allowing for sensing a ventricular electrogram indicative of ventricular depolarizations; and

an implantable cardioverter/defibrillator (ICD) including;

a sensing circuit, coupled to the implantable atrial lead and the implantable ventricular lead, to sense the atrial electrogram and the ventricular electrogram;

a rate detector circuit, coupled to the sensing circuit, to detect an atrial rate based on the atrial electrogram and a ventricular rate based on the ventricular electrogram;

a tachycardia detector circuit, coupled to the rate detector circuit, to detect a tachycardia based on at least one of the atrial rate and the ventricular rate;

a rhythm classifier circuit, coupled to the rate detector circuit and the tachycardia detector circuit, to classify the detected tachycardia as a 1;

1 tachycardia when the atrial rate and the ventricular rate are substantially equal; and

a tachycardia discriminator circuit coupled to the rhythm classifier circuit, the tachycardia discriminator circuit including;

a time interval measurement circuit, coupled to the sensing circuit, to measure a tachycardia time interval between an atrial depolarization and an adjacent ventricular depolarization during the 1;

1 tachycardia; and

a VT comparator circuit coupled to the time interval measurement circuit, the VT comparator circuit having an output adapted to indicate a detection of VT when the tachycardia time interval differs from a template time interval by at least a predetermined margin and an SVT detection when the tachycardia time interval does not differ from the template time interval by at least the predetermined margin.

19. The CRM system of claim 18, wherein the predetermined margin is a predetermined percentage of the template time interval.

20. The CRM system of claim 18, wherein the time interval measurement circuit comprises an atrioventricular interval (AVI) measurement module adapted to measure a tachycardia AVI when the tachycardia is detected and the 1:

1 tachycardia is classified.

21. The CRM system of claim 18, wherein the time interval measurement circuit comprises a ventriculoatrial interval (VAI) measurement module to measure a tachycardia VAI when the tachycardia is detected and the 1:

1 tachycardia is classified.

22. The CRM system of claim 18, wherein the tachycardia detector circuit comprises a tachycardia comparator circuit having a tachycardia output indicative a detected tachycardia when the ventricular rate exceeds a predetermined tachycardia threshold rate.

23. The CRM system of claim 22, wherein the rhythm classifier circuit comprises a rhythm comparator circuit to compare the atrial rate to the ventricular rate after the tachycardia is detected, the rhythm comparator circuit having an atrial rate input to receive the atrial rate, a ventricular rate input to receive a ventricular rate, and a classification output indicative of VT if the ventricular rate is substantially higher than the atrial rate, SVT or dual arrhythmia if the atrial rate is substantially higher than the ventricular rate, and the 1:

1 tachycardia if the atrial rate and the ventricular rate are substantially equal, wherein the dual arrhythmia includes a combination of SVT and VT.

24. The CRM system of claim 18, wherein the ICD further comprises an atrial fibrillation (AF) detector circuit, coupled to the rhythm classifier circuit, to detect AF if SVT is indicated.

25. The CRM system of claim 24, wherein the ICD further comprises an atrial defibrillation circuit, coupled to the AF detector circuit, to deliver one or more atrial defibrillation shocks when AF is detected.

26. The CRM system of claim 18, wherein the ICD further comprises a ventricular fibrillation (VF) detector circuit, coupled to the rhythm classifier circuit and the VT discriminator circuit, to detect VF if VT is detected.

27. The CRM system of claim 26, wherein the ICD further comprises a ventricular defibrillation circuit, coupled to the VF detector circuit, to deliver one or more ventricular defibrillation shocks when VF is detected.

28. The CRM system of claim 18, wherein the ICD further comprises a VT verifier circuit, coupled to the VT discriminator circuit, to verify VT detections.

29. The CRM system of claim 28, wherein the VT verifier comprises a further tachycardia discriminator circuit.

30. The CRM system of claim 18, further comprising an external system including an external device communicatively coupled to the ICD via telemetry, a remote device providing for access to the ICD from a distant location, and a network communicatively coupling the external device and the remote device.

31. A method for discriminating ventricular tachycardia (VT) from supraventricular tachycardia (SVT), the method comprising:

detecting a ventricular rate being a frequency of ventricular depolarizations;

detecting an atrial rate being a frequency of atrial depolarizations;

detecting a tachycardia based on at least one of the atrial and ventricular rates;

classifying the tachycardia as a 1;

1 tachycardia if the detected atrial rate is substantially the same as the detected ventricular rate;

measuring a tachycardia time interval between adjacent atrial and ventricular depolarizations during the 1;

1 tachycardia;

determining whether the tachycardia time interval differs from a template time interval by at least a predetermined margin; and

indicating a VT detection if the tachycardia time interval differs from the template time interval by at least the predetermined margin.

32. The method of claim 31, wherein the predetermined margin includes a predetermined percentage of the template time interval.

33. The method of claim 31, further comprising indicating a SVT detection if the tachycardia time interval does not exceed the template time interval by the predetermined percentage of the template time interval.

34. The method of claim 33, wherein measuring the tachycardia time interval comprises measuring a tachycardia atrioventricular interval (AVI) during the 1:

1 tachycardia, and wherein indicating the VT detection comprises indicating the VT detection if the tachycardia AVI exceeds a template AVI by at least a predetermined percentage of the template AVI.

35. The method of claim 34, further comprising creating the template AVI by measuring an AVI during a normal sinus rhythm.

36. The method of claim 33, wherein measuring the tachycardia time interval comprises measuring a tachycardia ventriculoatrial interval (VAI) and a tachycardia heart rate during the 1:

1 tachycardia, and wherein indicating the VT detection comprises adjusting the tachycardia VAI based on the tachycardia heart rate and a template heart rate, and indicating the VT detection if a template VAI exceeds the adjusted tachycardia VAI by a predetermined percentage of the template VAI.

37. The method of claim 36, further comprising:

creating the template VAI by measuring a VAI during a normal sinus rhythm; and

creating the template heart rate by measuring a heart rate during the normal sinus rhythm.

38. The method of claim 31, further comprising performing a statistical study based on a patient population to determine the predetermined margin.

47. The method of claim 31, further comprising confirming the VT detection indicating the VT detection.