Patent ID: 8750989

Claim:
A method of discriminating cardiac rhythms in an implantable defibrillator, the implantable defibrillator including a plurality of electrodes for use in sensing and/or therapy delivery, as well as operational circuitry coupled to the plurality of electrodes, the method comprising: the operational circuitry detecting a number of cardiac events in an electrical signal using at least two of the plurality of electrodes; the operational circuitry calculating a rate using the number of detected cardiac events; the operational circuitry determining a width for a plurality of the detected cardiac events and further determining a width stability therefrom; the operational circuitry applying a decision boundary to a combination of the rate and width stability observed from the detected events; and the operational circuitry determining, from the application of the decision boundary, whether a supraventricular condition which should not receive therapy is occurring or a ventricular arrhythmia which should receive therapy is occurring.