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Abstract

A tiered therapy cardiac detection system is provided for a medical device that senses cardiac signals representative of beat-to-beat intervals and delivers at least one therapy in response to a detected cardiac dysrhythmia corresponding to one of a plurality of programmed zones of heart rates. The detection system includes a global counter that counts at least all beat-to-beat intervals indicating a rate greater than a programmed threshold value representative of a minimum heart rate for delivering any therapy once an initial threshold condition is met. A plurality of window memories and parameter memories are provided in the device. Each window memory corresponds to a given one of the zones and stores an indication of whether each of a last N cardiac signals are within that zone. Each parameter memory corresponds to a given one of the zones and stores a programmed trigger value of the global counter required in order for a therapy in that zone to be delivered. Processing circuitry evaluates the global counter, the window memories and the parameter memories on a beat-by-beat basis and indicates that a cardiac dysrhythmia has been detected for a given zone if the global counter exceeds the programmed trigger value for that zone and the indications stored by the window memory for that zone satisfy a predetermined criteria.

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First Claim