Importance

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Abstract

The implantable cardioverter/pacer includes a pacer channel and a rate detect channel both receiving a cardiac signal representative of the ECG of patient. The pacing channel issues a pacing signal when the amplitude of the cardiac signal fails to exceed a first predetermined threshold within a predetermined time period. The rate detect channel has a variable gain amplifier which is controlled by an automatic gain control (AGC). The AGC increases the gain in the amplifier based upon the level of the cardiac signal applied thereto and upon the time since the last peak of the cardiac signal. A one shot receives the output of the variable gain amplifier and produces a heart rate signal. Both the pacing and the heart rate signals are applied to a microprocessor. The microprocessor ignores or blanks out the first two or three pacing signals in order to allow the automatic gain control in the rate detect channel to increase or approach a maximum in order to determine whether a low level cardiac signal is present which may be indicative of certain ventricular arrhythmias. After the blanking period, the microprocessor issues appropriate treatments, either pacing or cardioverting, to the heart.

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First Claim