Patent ID: 8670826

Claim:
An implantable cardiac stimulus device (ICSD) configured for implantation into a patient's body comprising, a housing having at least one electrode and configured to receive a lead having a plurality of electrodes, operational circuitry contained in the housing and configured to receive signals from electrodes on the lead and/or housing when the lead is received by the housing wherein the operational circuitry is configured to perform a method of cardiac signal analysis comprising: sensing signals from the electrodes; identifying detected events in the sensed signals with the intent that detected events represent cardiac events; determining whether a high-rate arrhythmia appears likely; calculating an X/Y counter in which X represents the number of detected events identified as likely indicating a malignant cardiac rhythm out of a set of Y detected events; and determining whether the X/Y counter indicates therapy for the patient; wherein the operational circuitry is configured to allow at least first and second settings for the X/Y counter, in which the second setting uses values for X and Y that are greater than values for X and Y used in the first setting and greater than 18 for X and greater than 24 for Y; wherein the operational circuitry is configured to identify nonsustained tachycardia in which the first setting of the X/Y counter is net and, in response to identification of nonsustained tachycardia, to adopt the use of the second setting for the X/Y counter in analyzing future cardiac rhythms to avoid unnecessary therapy delivery.