Method and apparatus for discriminating tachycardia events in a medical device

1. A method of detecting a cardiac event and delivering shock therapy via a medical device, comprising:

sensing cardiac signals from a plurality of electrodes, the plurality of electrodes forming a first sensing vector and a second sensing vector;

performing a first processing of a first interval sensed along the first sensing vector during a predetermined sensing window and a second interval simultaneously sensed along the second sensing vector;

identifying the cardiac event as being a shockable event based on the first processing of the first interval and the second interval;

performing a second processing of the first interval and the second interval, different from the first processing, in response to the cardiac event being identified as a shockable event;

determining whether to delay a confirmation of the identification of the cardiac event as being shockable based on the second processing of the first interval and the second interval;

initiating charging of a high voltage shocking capacitor of the medical device configured to deliver the shock therapy in response to determining not to delay the confirmation of the identification of the cardiac event as being shockable based on to the second processing; and

discharging the high voltage shocking capacitor to deliver the shock therapy.

2. The method of claim 1 , wherein the cardiac event is a first cardiac event and the sensing window is a first sensing window, the method further comprising:

performing a first processing of a third interval sensed along the first sensing vector during a second predetermined sensing window and a fourth interval simultaneously sensed along the second sensing vector;

identifying a second cardiac event as being a shockable event based on the first processing of the third interval and the fourth interval;

performing a second processing of the third interval and the fourth interval, different from the first processing, in response to the second cardiac event being identified as a shockable event; and

determining to delay the confirmation of the identification of the second cardiac event as being shockable based on the second processing of the third interval and the fourth interval.

3. The method of claim 2 , wherein performing the second processing of the third interval and the fourth interval comprises:

identifying a plurality of R-waves associated with the third interval and a plurality of R-waves associated with the fourth interval;

comparing a selected R-wave of the plurality of R-waves associated with the third interval with one or more R-waves of the plurality of R-waves associated with the third interval other than the selected R-wave associated with the third interval;

comparing a selected R-wave of the plurality of R-waves associated with the fourth interval with one or more R-waves of the plurality of R-waves associated with the fourth interval other than the selected R-wave associated with the fourth interval; and

determining that at least one of the third interval and the fourth interval correspond to monomorphic ventricular tachycardia based on both of the comparisons.

4. The method of claim 3 , further comprising:

performing, while delaying the confirmation of the identification of the second cardiac event as being shockable, a processing of a fifth interval sensed along the first sensing vector during a third predetermined sensing window occurring subsequent to the second predetermined sensing window and a sixth interval simultaneously sensed along the second sensing vector during the third predetermined sensing window;

confirming the identification of the second cardiac event as being a shockable event based on the processing of the fifth interval and the sixth interval;

initiating charging of a high voltage shocking capacitor of the medical device configured to deliver a shock therapy in response to the confirmation of the identification of the cardiac event as being shockable based on to the processing of the fifth interval and the sixth interval; and

discharging the high voltage shocking capacitor to deliver the shock therapy.

5. The method of claim 4 , wherein performing the processing of the fifth interval and the sixth interval comprises:

identifying a plurality of R-waves associated with the fifth interval and a plurality of R-waves associated with the sixth interval;

comparing a selected R-wave of the plurality of R-waves associated with the fifth interval with one or more of the R-waves associated with the fifth interval other than the selected R-wave of the plurality of R-waves associated with the fifth interval;

comparing a selected R-wave of the plurality of R-waves associated with the sixth interval with one or more of the R-waves associated with the sixth interval other than the selected R-wave of the plurality of R-waves associated with the sixth interval; and

determining that the fifth interval and the sixth interval correspond to monomorphic ventricular tachycardia based on both of the comparisons.

6. The method of claim 5 , further comprising determining the cardiac event as being monomorphic ventricular tachycardia based on the determination that the fifth interval and the sixth interval correspond to monomorphic ventricular tachycardia.

7. The method of claim 4 , wherein confirming the identification of the second cardiac event as being a shockable event comprises:

determining that both the fifth interval and the sixth interval correspond to monomorphic ventricular tachycardia based on the second processing of the fifth interval and the sixth interval; and

determining the second cardiac event as being monomorphic ventricular tachycardia in response to both the fifth interval and the sixth interval being determined to correspond to monomorphic ventricular tachycardia.

8. The method of claim 1 , wherein determining not to delay the confirmation of the identification of the cardiac event as being shockable comprises determining that the cardiac event is not monomorphic ventricular tachycardia based on the second processing.

9. The method of claim 8 , wherein determining that the cardiac event is not monomorphic ventricular tachycardia based on the second processing comprises:

identifying a plurality of R-waves associated with the first interval and a plurality of R-waves associated with the second interval;

comparing a selected R-wave of the plurality of R-waves associated with the first interval with one or more R-waves of the plurality of R-waves associated with the first interval other than the selected R-wave associated with the first interval;

comparing a selected R-wave of the plurality of R-waves associated with the second interval with one or more R-waves of the plurality of R-waves associated with the second interval other than the selected R-wave associated with the second interval; and

determining that at least one of the first interval and the second interval correspond to polymorphic ventricular tachycardia based on both of the comparisons.

10. A medical device for detecting a cardiac event and delivering a shock therapy, comprising:

a plurality of electrodes configured to sense cardiac signals, the plurality of electrodes forming a first sensing vector and a second sensing vector;

a housing having circuitry positioned therein and electrically coupled to the plurality of electrodes;

a high voltage shocking capacitor configured to deliver a shock therapy to a patient's heart via electrodes coupled to the medical device; and

a processor positioned within the housing and configured to:

perform a first processing of a first interval sensed along the first sensing vector during a predetermined sensing window and a second interval simultaneously sensed along the second sensing vector,

identify the cardiac event as being a shockable event based on the first processing of the first interval and the second interval,

perform a second processing of the first interval and the second interval, different from the first processing, in response to the cardiac event being identified as a shockable event,

determine whether to delay a confirmation of the identification of the cardiac event as being shockable based on the second processing of the first interval and the second interval,

initiate charging of the high voltage shocking capacitor in response to determining not to delay the confirmation of the identification of the cardiac event as being shockable based on to the second processing; and

initiate discharging of the high voltage shocking capacitor to deliver the shock therapy.

11. The medical device of claim 10 , wherein the cardiac event is a first cardiac event and the sensing window is a first sensing window, and wherein the processor is further configured to:

perform a first processing of a third interval sensed along the first sensing vector during a second predetermined sensing window and a fourth interval simultaneously sensed along the second sensing vector;

identify a second cardiac event as being a shockable event based on the first processing of the third interval and the fourth interval;

perform a second processing of the third interval and the fourth interval, different from the first processing, in response to the second cardiac event being identified as a shockable event; and

determine to delay the confirmation of the identification of the second cardiac event as being shockable based on the second processing of the third interval and the fourth interval.

12. The medical device of claim 11 , wherein the processor is configured to perform the second processing of the third interval and the fourth interval comprise by at least:

identifying a plurality of R-waves associated with the third interval and a plurality of R-waves associated with the fourth interval;

comparing a selected R-wave of the plurality of R-waves associated with the third interval with one or more R-waves of the plurality of R-waves associated with the third interval other than the selected R-wave associated with the third interval;

comparing a selected R-wave of the plurality of R-waves associated with the fourth interval with one or more R-waves of the plurality of R-waves associated with the fourth interval other than the selected R-wave associated with the fourth interval; and

determining that at least one of the third interval and the fourth interval correspond to monomorphic ventricular tachycardia based on both of the comparisons.

13. The medical device of claim 12 , wherein the processor is further configured to:

perform, while delaying the confirmation of the identification of the second cardiac event as being shockable, a processing of a fifth interval sensed along the first sensing vector during a third predetermined sensing window occurring subsequent to the second predetermined sensing window and a sixth interval simultaneously sensed along the second sensing vector during the third predetermined sensing window;

confirm the identification of the second cardiac event as being a shockable event based on the processing of the fifth interval and the sixth interval;

initiate charging of the high voltage shocking capacitor in response to the confirmation of the identification of the cardiac event as being shockable based on to the processing of the fifth interval and the sixth interval; and

initiate discharging the high voltage shocking capacitor to deliver the shock therapy.

14. The medical device of claim 13 , wherein the processor is configured to perform the processing of the fifth interval and the sixth interval by at least:

identifying a plurality of R-waves associated with the fifth interval and a plurality of R-waves associated with the sixth interval,

comparing a selected R-wave of the plurality of R-waves associated with the fifth interval with one or more of the R-waves associated with the fifth interval other than the selected R-wave of the plurality of R-waves associated with the fifth interval,

comparing a selected R-wave of the plurality of R-waves associated with the sixth interval with one or more of the R-waves associated with the sixth interval other than the selected R-wave of the plurality of R-waves associated with the sixth interval, and

determining that the fifth interval and the sixth interval correspond to monomorphic ventricular tachycardia based on both of the comparisons.

15. The medical device of claim of claim 14 , wherein the processor is further configured to determine the cardiac event as being monomorphic ventricular tachycardia based on the determination that the fifth interval and the sixth interval correspond to monomorphic ventricular tachycardia.

16. The medical device of claim 13 , wherein the processor is configured to confirm the identification of the second cardiac event as being a shockable event by at least:

determining that both the fifth interval and the sixth interval correspond to monomorphic ventricular tachycardia based on the second processing of the fifth interval and the sixth interval; and

determining the second cardiac event as being monomorphic ventricular tachycardia in response to both the fifth interval and the sixth interval being determined to correspond to monomorphic ventricular tachycardia.

17. The medical device of claim 10 , wherein the processor is configured to determine not to delay the confirmation of the identification of the cardiac event as being shockable by at least determining that the cardiac event is not monomorphic ventricular tachycardia based on the second processing.

18. The medical device of claim 17 , wherein the processor is configured to determine that the cardiac event is not monomorphic ventricular tachycardia based on the second processing by at least:

identifying a plurality of R-waves associated with the first interval and a plurality of R-waves associated with the second interval;

comparing a selected R-wave of the plurality of R-waves associated with the first interval with one or more R-waves of the plurality of R-waves associated with the first interval other than the selected R-wave associated with the first interval;

comparing a selected R-wave of the plurality of R-waves associated with the second interval with one or more R-waves of the plurality of R-waves associated with the second interval other than the selected R-wave associated with the second interval; and

determining that at least one of the first interval and the second interval correspond to polymorphic ventricular tachycardia based on both of the comparisons.

19. The medical device of claim 11 , wherein the processor is further configured to:

delay the confirmation of the identification of the second cardiac event as being shockable by a delay period following the third and fourth intervals in response to determining to delay identifying the confirmation of the identification of the second cardiac event as being shockable;

determine that the second cardiac event terminated during the delay period; and

adjust the delay period in response to determining the second cardiac event terminated during the delay period.

20. A non-transitory, computer-readable storage medium storing instructions for causing a processor included in a medical device to perform a method for determining a cardiac event and controlling shock therapy delivery via the medical device, the method comprising:

sensing cardiac signals from a plurality of electrodes, the plurality of electrodes forming a first sensing vector and a second sensing vector;

performing a first processing of a first interval sensed along the first sensing vector during a predetermined sensing window and a second interval simultaneously sensed along the second sensing vector;

identifying the cardiac event as being a shockable event based on the first processing of the first interval and the second interval;

performing a second processing of the first interval and the second interval, different from the first processing, in response to the cardiac event being identified as a shockable event;

determining whether to delay a confirmation of the identification of the cardiac event as being shockable based on the second processing of the first interval and the second interval;

initiating charging of a high voltage shocking capacitor of the medical device configured to deliver the shock therapy in response to determining not to delay the confirmation of the identification of the cardiac event as being shockable based on to the second processing; and

discharging the high voltage shocking capacitor to deliver the shock therapy.